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Displaying Tactile Sensation by SMA-Driven Vibration and Controlled Temperature for Cutaneous Sensation Assessment
Soft Robotic Actuators: Applications in Bioengineering and HASEL actuators's Future Potential
Beyond Human Touch: Integrating Soft Robotics with Environmental Interaction for Advanced Applications
Design, Control, and Testing of a Multifunctional Soft Robotic Gripper
Neuroadaptive Control of a Continuum Robot for Finger Rehabilitation

Journal Description

Actuators

Actuators is an international, peer-reviewed, open access journal on the science and technology of actuators and control systems published monthly online by MDPI.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within SCIE (Web of Science), Scopus, Inspec, and other databases.
Journal Rank: JCR - Q2 (Engineering, Mechanical) / CiteScore - Q2 (Control and Optimization)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 17.7 days after submission; acceptance to publication is undertaken in 1.9 days (median values for papers published in this journal in the second half of 2024).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.

Impact Factor: 2.2 (2023); 5-Year Impact Factor: 2.4 (2023)

Imprint Information Journal Flyer Open Access ISSN: 2076-0825

Latest Articles

18 pages, 5988 KiB

Open AccessArticle

Nonlinear Adaptive Control of Maglev System Based on Parameter Identification

by Haiyan Qiang, Sheng Qiao, Hengyue Huang, Ping Cheng and Yougang Sun

Actuators 2025, 14(3), 115; https://doi.org/10.3390/act14030115 (registering DOI) - 26 Feb 2025

To address the nonlinearity and control problems of the Maglev system caused by external disturbances and internal factors of the system, this study first established a kinematic model of a single-point levitation system. Secondly, based on the nonlinear characteristics of the kinematic model, [...] Read more.

To address the nonlinearity and control problems of the Maglev system caused by external disturbances and internal factors of the system, this study first established a kinematic model of a single-point levitation system. Secondly, based on the nonlinear characteristics of the kinematic model, Gaussian noise was introduced into the model as input disturbance, and a neural network was used to train the constructed model. A nonlinear autoregressive model with exogenous inputs was constructed, and the Recursive Least Squares method with Forgetting Factor (RLS-FF) was used to perform parameter identification on the levitation system by combining the training data, further constructing an accurate model of the levitation system. Then, based on the accurate model of the levitation system, the backstepping method was adopted to design an adaptive controller for the levitation system, and its stability was verified. Simulation analysis was conducted on the MATLAB/Simulink platform, and comparisons were made with the LQR control method and the Fuzzy-PID control method that verified that the designed controller had a faster response speed and better self-regulation ability. At the same time, interference signals were introduced into the simulation to simulate the actual scene, and the good anti-interference ability and adaptive performance of the designed controller were further verified. Full article

(This article belongs to the Special Issue Advanced Theory and Application of Magnetic Actuators—2nd Edition)

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<p>Cross-sectional view of EMS Maglev train.</p> Full article ">Figure 2
<p>Structural body of the single-point levitation system.</p> Full article ">Figure 3
<p>Training results of the nonlinear model.</p> Full article ">Figure 4
<p>Diagram of the model after slicing treatment.</p> Full article ">Figure 5
<p>Random point diagram of the model.</p> Full article ">Figure 6
<p>Input current–time curve under Gaussian noise after parameter identification.</p> Full article ">Figure 7
<p>Air gap–time curve after parameter identification.</p> Full article ">Figure 8
<p>Adaptive control structure of the levitation system.</p> Full article ">Figure 9
<p>Input voltage curve under adaptive control.</p> Full article ">Figure 10
<p>Air gap curve under adaptive control.</p> Full article ">Figure 11
<p>Error <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>e</mi> </mrow> <mrow> <mn>1</mn> </mrow> </msub> </mrow> </semantics></math>.</p> Full article ">Figure 12
<p>Error <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>e</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msub> </mrow> </semantics></math>.</p> Full article ">Figure 13
<p>LQR control structure.</p> Full article ">Figure 14
<p>Fuzzy-PID control structure.</p> Full article ">Figure 15
<p>Comparison of effects under different controls.</p> Full article ">Figure 16
<p>Comparison of different control effects under step signals.</p> Full article ">Figure 17
<p>Control effect of the levitation system under the sinusoidal signal.</p> Full article ">

18 pages, 3958 KiB

Open AccessArticle

Design of Automatic Landing System for Carrier-Based Aircraft Based on Adaptive Fuzzy Sliding-Mode Control

by Haotian Zhang, Ruoheng Ma, Zhenlin Xing and Jianliang Ai

Actuators 2025, 14(3), 114; https://doi.org/10.3390/act14030114 - 26 Feb 2025

Carrier-based aircraft (CBA) landing involves complex system engineering characterized by strong non-linearity, significant coupling and susceptibility to environmental disturbances. To address uncertainties in parameters, carrier air-wake disturbances and other challenges inherent to CBA landing, this paper presents a longitudinal automatic landing system based [...] Read more.

Carrier-based aircraft (CBA) landing involves complex system engineering characterized by strong non-linearity, significant coupling and susceptibility to environmental disturbances. To address uncertainties in parameters, carrier air-wake disturbances and other challenges inherent to CBA landing, this paper presents a longitudinal automatic landing system based on adaptive fuzzy sliding-mode control. This system was developed to improve control accuracy and stability during the critical landing phase. Furthermore, this paper analyzes components of carrier air-wake and motion conditions for ideal landing points on the carrier deck, and designs a sliding-mode surface with the integral term. An adaptive fuzzy sliding-mode controller based on equivalent and switching controls is constructed, which exhibits stability under the Lyapunov stability condition. Moreover, a Monte Carlo simulation method is employed to verify the simulation of the automatic landing control system. Owing to its impressive dynamic performance and robustness, the proposed control method can track expected values with high accuracy in a complex environment, thereby satisfying the CBA landing requirements. Full article

(This article belongs to the Section Aerospace Actuators)

19 pages, 6456 KiB

Open AccessArticle

Multi-Signal Induction Motor Broken Rotor Bar Detection Based on Merged Convolutional Neural Network

by Tianyi Wang, Shiguang Wen, Shaotong Sheng and Huimin Ma

Actuators 2025, 14(3), 113; https://doi.org/10.3390/act14030113 - 25 Feb 2025

Motor fault detection plays a vital role in industrial maintenance. Timely detection of faults in their early stages can prevent catastrophic consequences and reduce maintenance costs. Traditional methods face challenges in motor broken rotor bar (BRB) detection: model-driven methods are difficult to apply [...] Read more.

Motor fault detection plays a vital role in industrial maintenance. Timely detection of faults in their early stages can prevent catastrophic consequences and reduce maintenance costs. Traditional methods face challenges in motor broken rotor bar (BRB) detection: model-driven methods are difficult to apply accurately in complex and changing environments, while data-driven methods usually require sophisticated feature extraction and classification processes. In this paper, we propose a novel non-invasive fault detection method. The method preprocesses motor currents by Hilbert-Huang Transform (HHT) and Park’s Vector Modulus (PVM) and then uses a merged convolutional neural network (CNN) for classification. This experiment investigates the detection of broken rotor bars of motors with different loads (25%, 50%, 75%, and 100% of rated load) and different fault levels (Normal, 1BRB, 2BRB, 3BRB, and 4BRB). The results show that the model’s classification accuracy exceeds 95% under various operating conditions and can maintain high accuracy under low load conditions, thus addressing the limitations faced by existing methods. In addition, it is computationally efficient and can guarantee high real-time performance. This method combines advanced signal processing techniques and deep learning algorithms to provide a practical solution for motor broken rotor bar detection. Full article

(This article belongs to the Section Actuators for Manufacturing Systems)

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<p>IMF list and corresponding HHT spectrum of a current sample. (<b>a</b>) The IMFs obtained after EMD; (<b>b</b>) the generated HHT spectrum.</p> Full article ">Figure 2
<p>PVA and PVM images of normal motor and motor with four BRBs (100% load). (<b>a</b>,<b>c</b>) Normal motor; (<b>b</b>,<b>d</b>) faulty motor.</p> Full article ">Figure 3
<p>Motor current sampling data, including start-up transient and steady state.</p> Full article ">Figure 4
<p>Model training and testing data division method. (<b>a</b>) Normal motor, including four load levels, a total of four pieces of current data; (<b>b</b>) faulty motor, including four fault levels and four load levels, a total of 16 pieces of current data.</p> Full article ">Figure 5
<p>HHT spectra of motors under different working conditions. (<b>a</b>) Normal motor at 75% load; (<b>b</b>) motor with one BRB at 75% load; (<b>c</b>) motor with four BRBs at 75% load; (<b>d</b>) normal motor at 100% load; (<b>e</b>) motor with one BRB at 100% load; (<b>f</b>) motor with four BRBs at 100% load.</p> Full article ">Figure 6
<p>PVM images of motors under different working conditions. (<b>a</b>) Normal motor at 100% load; (<b>b</b>) motor with one BRB at 100% load; (<b>c</b>) motor with four BRBs at 100% load.</p> Full article ">Figure 7
<p>Flowchart of end-to-end CNN model training.</p> Full article ">Figure 8
<p>Detailed view of the merged CNN architecture.</p> Full article ">Figure 9
<p>Line plot of model training and validation accuracy and loss.</p> Full article ">Figure 10
<p>Overall confusion matrix of model testing.</p> Full article ">

21 pages, 5037 KiB

Open AccessFeature PaperArticle

SNN-Based Surrogate Modeling of Electromagnetic Force and Its Application in Maglev Vehicle Dynamics Simulation

by Yang Feng, Chunfa Zhao, Xin Liang and Zhan Bai

Actuators 2025, 14(3), 112; https://doi.org/10.3390/act14030112 - 25 Feb 2025

The majority of electromagnetic force calculation models employed in maglev vehicle system dynamics focus exclusively on vertical and lateral movement while neglecting the nonlinear magnetization properties of ferromagnetic materials. This oversight leads to discrepancies between the dynamics simulations and actual conditions. To enhance [...] Read more.

The majority of electromagnetic force calculation models employed in maglev vehicle system dynamics focus exclusively on vertical and lateral movement while neglecting the nonlinear magnetization properties of ferromagnetic materials. This oversight leads to discrepancies between the dynamics simulations and actual conditions. To enhance the accuracy of dynamics simulations and evaluate the performance of maglev vehicle systems under various operational conditions, it is imperative to identify an electromagnetic force calculation model that combines accuracy and applicability. To address this objective, this paper examines a U-shaped electromagnet in medium–low-speed maglev vehicles as a case study. It constructs a spatial electromagnetic force calculation surrogate model using a Shallow Neural Network. The surrogate model is capable of accurately calculating electromagnetic forces considering relative position deviations in the lateral, vertical, rolling, pitching, and shaking directions. Moreover, it can be integrated into vehicle system dynamics simulations. The accuracy of the electromagnetic force calculation surrogate model is confirmed by extensive comparisons with finite element simulation results across various conditions, achieving an impressive concordance rate of up to 95%. An illustrative application of the electromagnetic force calculation surrogate model in maglev vehicle system dynamics simulation is provided to showcase its practical utility. Full article

(This article belongs to the Special Issue Advanced Theory and Application of Magnetic Actuators—2nd Edition)

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<p>Schematic diagram of medium–low-speed maglev vehicle–track system.</p> Full article ">Figure 2
<p>Schematic diagram of building EFC surrogate model.</p> Full article ">Figure 3
<p>Calculation conditions sample distribution with the variation in rotation angle. (<b>a</b>) Pre-sampling data (<b>b</b>) sampling data for calculation.</p> Full article ">Figure 4
<p>Electromagnet–rail force FE model.</p> Full article ">Figure 5
<p>Magnetization characteristics.</p> Full article ">Figure 6
<p>Normalized electromagnetic force samples for SNN training. (<b>a</b>) Levitation force normalization, (<b>b</b>) guidance force normalization.</p> Full article ">Figure 7
<p>EFC surrogate model building flow diagram.</p> Full article ">Figure 8
<p>EFC results under different lateral misalignments (levitation gap 8 mm, coil current 35 A). (<b>a</b>) Levitation force, (<b>b</b>) guidance force.</p> Full article ">Figure 9
<p>EFC results under different coil currents (levitation gap 12 mm, lateral misalignment 10 mm). (<b>a</b>) Levitation force, (<b>b</b>) guidance force.</p> Full article ">Figure 10
<p>Error distributions of EFC surrogate model in rotation conditions (levitation gap 8 mm, lateral misalignment 0 mm and coil current 35 A). (<b>a</b>) Relative error of levitation force, (<b>b</b>) absolute error of guidance force.</p> Full article ">Figure 11
<p>Levitation force results with coil current increases from 45 A to 125 A (levitation gap 16 mm, lateral misalignment 0 mm).</p> Full article ">Figure 12
<p>EFC results with coil current increases from 45 A to 125 A (levitation gap 16 mm, lateral misalignment 12 mm). (<b>a</b>) Levitation force, (<b>b</b>) guidance force.</p> Full article ">Figure 13
<p>Scheme of dynamics simulation using EFC surrogate model.</p> Full article ">Figure 14
<p>Levitation gap and lateral displacement responses of levitation module. (<b>a</b>) Levitation gap, (<b>b</b>) lateral displacement.</p> Full article ">Figure 15
<p>Pitching angle and shaking angle responses of levitation module. (<b>a</b>) Pitching angle, (<b>b</b>) Shaking angle.</p> Full article ">Figure 16
<p>Vehicle dynamics response differences when using two different EFC models. (<b>a</b>) Levitation gap, (<b>b</b>) coil current, (<b>c</b>) Vertical acceleration.</p> Full article ">

16 pages, 2006 KiB

Open AccessArticle

Research on Risk Analysis Method of Maglev Train Suspension System Based on Fuzzy Multi-Attribute Decision-Making

by Xiang Chen, Xiaolong Li and Yilu Feng

Actuators 2025, 14(3), 111; https://doi.org/10.3390/act14030111 - 25 Feb 2025

As a new type of rail transit vehicle, maglev trains have extremely high requirements for safety and reliability. With the gradual commercial operation of maglev trains, how to scientifically and effectively assess the safety and analyze the risks of train equipment has become [...] Read more.

As a new type of rail transit vehicle, maglev trains have extremely high requirements for safety and reliability. With the gradual commercial operation of maglev trains, how to scientifically and effectively assess the safety and analyze the risks of train equipment has become an urgent issue to be addressed. Against the backdrop of the practical application of maglev train projects, this paper integrates domestic and international risk analysis models, proposes the steps for conducting the risk analysis of maglev rail transit, and establishes a risk analysis system for the entire lifecycle of maglev rail transit. Based on the results of fault analysis, a risk analysis of the levitation system is carried out. The theory of multi-attribute decision-making is studied, new risk evaluation indicators are established using triangular fuzzy numbers, the risk levels of the levitation system are determined, and the weak links within the system and the relationships between the pieces of equipment are identified. These efforts provide guidance for enhancing the safety and reliability of train equipment and for carrying out train maintenance work. Full article

(This article belongs to the Special Issue Advanced Theory and Application of Magnetic Actuators—2nd Edition)

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15 pages, 7444 KiB

Open AccessArticle

Soft Robot Workspace Estimation via Finite Element Analysis and Machine Learning

by Getachew Ambaye, Enkhsaikhan Boldsaikhan and Krishna Krishnan

Actuators 2025, 14(3), 110; https://doi.org/10.3390/act14030110 - 23 Feb 2025

Soft robots with compliant bodies offer safe human–robot interaction as well as adaptability to unstructured dynamic environments. However, the nonlinear dynamics of a soft robot with infinite motion freedom pose various challenges to operation and control engineering. This research explores the motion of [...] Read more.

Soft robots with compliant bodies offer safe human–robot interaction as well as adaptability to unstructured dynamic environments. However, the nonlinear dynamics of a soft robot with infinite motion freedom pose various challenges to operation and control engineering. This research explores the motion of a pneumatic soft robot under diverse loading conditions by conducting finite element analysis (FEA) and using machine learning. The pneumatic soft robot consists of two parallel hyper-elastic tubular chambers that convert pneumatic pressure inputs into soft robot motion to mimic an elephant trunk and its motion. The body of each pneumatic chamber consists of a series of bellows to effectively facilitate the expansion, contraction, and bending of the body. The first chamber spans the entire length of the soft robot’s body, and the second chamber spans half of it. This unique asymmetric design enables the soft robot to bend and curl in various ways. Machine learning is used to establish a forward kinematic relationship between the pressure inputs and the motion responses of the soft robot using data from FEA. Accordingly, this research employs an artificial neural network that is trained on FEA data to estimate the reachable workspace of the soft robot for given pressure inputs. The trained neural network demonstrates promising estimation accuracy with an R-squared value of 0.99 and a root mean square error of 0.783. The workspaces of asymmetric double-chamber and single-chamber soft robots were compared, revealing that the double-chamber robot offers approximately 185 times more reachable workspace than the single-chamber soft robot. Full article

(This article belongs to the Special Issue Bio-Inspired Soft Robotics)

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<p>The soft actuator inspired by the elephant trunk [<a href="#B6-actuators-14-00110" class="html-bibr">6</a>].</p> Full article ">Figure 2
<p>Overall approach.</p> Full article ">Figure 3
<p>Soft robot model. The measurement unit is mm.</p> Full article ">Figure 4
<p>Soft robot base and tip and two pneumatic chambers.</p> Full article ">Figure 5
<p>Analysis setup: (<b>a</b>) constraints for gravitational load analysis, (<b>b</b>) eccentricity, and (<b>c</b>) surface contacts.</p> Full article ">Figure 6
<p>The effects of gravity on bending displacement and stress.</p> Full article ">Figure 7
<p>Neural network architecture.</p> Full article ">Figure 8
<p>Mean square errors vs. training epochs.</p> Full article ">Figure 9
<p>Regression plots of neural network accuracy.</p> Full article ">Figure 10
<p>Residual analysis of displacement responses: without noise (<b>left</b>) and with 0.1% Gaussian noise (<b>right</b>).</p> Full article ">Figure 11
<p>Soft robot actuation for selected loading cases in <a href="#actuators-14-00110-t002" class="html-table">Table 2</a>.</p> Full article ">Figure 12
<p>Soft robot tip paths for loading cases in <a href="#actuators-14-00110-t002" class="html-table">Table 2</a>.</p> Full article ">Figure 13
<p>Soft robot tip paths estimated by trained NN for loading cases in <a href="#actuators-14-00110-t002" class="html-table">Table 2</a>.</p> Full article ">Figure 14
<p>Estimated workspace of soft robot tip for pressure inputs between 600 kPa and 700 kPa: top (<b>a</b>), front (<b>b</b>), side (<b>c</b>), and isometric (<b>d</b>) views of workspace in reference frame R1.</p> Full article ">Figure 15
<p>Workspace of the single-chamber soft robot tip for pressure inputs between 0 and 700 kPa: top (<b>a</b>), front (<b>b</b>), side (<b>c</b>), and isometric (<b>d</b>) views.</p> Full article ">Figure 16
<p>Comparisons between asymmetric and single-chamber pneumatic soft robots.</p> Full article ">

24 pages, 6389 KiB

Open AccessArticle

Local Heat Transfer Analysis of Dual Sweeping Jet, Double Sweeping Jets, and Double Circular Jets Impinging at a Flat Surface

by Muhammad Zubair, Feng Ren and Xin Wen

Actuators 2025, 14(3), 109; https://doi.org/10.3390/act14030109 - 21 Feb 2025

A sweeping jet is commonly preferred over a steady jet owing to its ability to better cool the region away from the strong core of an impinging jet. For industrial applications, it is important to study the thermal fields of oscillating jets in [...] Read more.

A sweeping jet is commonly preferred over a steady jet owing to its ability to better cool the region away from the strong core of an impinging jet. For industrial applications, it is important to study the thermal fields of oscillating jets in a multi-jet configuration to focus on the region that falls between the two consecutive fluidic oscillators and, hence, suggest a mechanism to uniformly cool the targeted flat surface. A comparative experimental study of dual sweeping jets (DSJs), double sweeping jets (DbSJs), and double circular jets (DbCJs) was conducted at different jet-to-plate spacings, various Re numbers, and three aspect ratios. The multi-circular and sweeping jets were impinged on a flat hot surface, which was heated at a constant flux of current, and thermocouples were employed to efficiently collect the time-averaged heat transfer distribution along the sweeping and transverse directions. It was determined that heat transfer, in terms of the Nusselt number, generally increased with increasing Re number and reduced the jet-to-wall spacing for the DSJ, DbSJ, and DbCJ, with some minor exceptions. The relative performance of these fluidic devices suggested that the best performance of DSJ was at small spacing and higher Re, DbSJ at moderate spacing and lower Re, and DbCJ at moderate spacing and moderate Re. The mutual comparison showed that along the sweeping motion, in the central region, DbCJ was better than both DSJ and DbSJ; in the right region, DSJ performance was far better than DbCJ and DbSJ; in the left region, DSJ was better than DbSJ when comparing the respective centers of DSJ and DbSJ. The dominance of DSJ over DbSJ at the centers of their respective bodies even extends in the transverse direction. Finally, for higher aspect ratios, the DSJ performed better in the outer regions, while the DbSJ performed well in the central region. Similarly, for both DSJ and DbSJ unanimously, the effect of changing the aspect ratio is interesting as initially, the Nu values increase for a higher aspect ratio, but by increasing the AR further, it causes a divergence of the fluidic volume from the central region to the surrounding region. Full article

(This article belongs to the Special Issue Active Flow Control: Recent Advances in Fundamentals and Applications—3rd Edition)

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<p>Different types of fluidic devices: (<b>a</b>) DbCJ—double circular jets, (<b>b</b>) DbSJ—double sweeping jets, and (<b>c</b>) DSJ—dual sweeping jet.</p> Full article ">Figure 2
<p>Impingement setup for heat transfer measurements: (<b>a</b>) front view, (<b>b</b>) top view.</p> Full article ">Figure 2 Cont.
<p>Impingement setup for heat transfer measurements: (<b>a</b>) front view, (<b>b</b>) top view.</p> Full article ">Figure 3
<p>Overall experimental setup for the heat transfer measurements.</p> Full article ">Figure 4
<p>Experimental methodology verification for a circular jet with hd = 5 mm (Kim et al. 2019 [<a href="#B27-actuators-14-00109" class="html-bibr">27</a>]).</p> Full article ">Figure 5
<p>Comparison of Nusselt number profiles of DSJ, DbSJ, and DbCJ along the x-axis (sweeping direction) and for different Re numbers: (<b>a</b>) Re = 8 k, (<b>b</b>) Re = 12 k, (<b>c</b>) Re = 16 k, (<b>d</b>) Re = 20 k.</p> Full article ">Figure 6
<p>Comparison of Nusselt number profiles of DSJ, DbSJ, and DbCJ along the x-axis (sweeping direction) and for different jet-wall-spacings: (<b>a</b>) H = 3 hd, (<b>b</b>) H = 5 hd, (<b>c</b>) H = 7 hd, and (<b>d</b>) H = 9 hd.</p> Full article ">Figure 7
<p>Comparison of Nusselt number profiles of DSJ, DbSJ, and DbCJ for different y-axes (transverse directions): (<b>a</b>) DSJ vs. DbSJ, at −3 hd and −4.2 hd y-axes respectively, Re = 16 k, different H; (<b>b</b>) DSJ vs. DbSJ, at −3 hd and −4.2 hd y-axes respectively, H = 5 hd, different Re; (<b>c</b>) DSJ vs. DbCJ, both at −3 hd y-axis, Re = 16 k, different H; (<b>d</b>) DSJ vs. DbCJ, both at −3 hd y-axis, H = 5 hd, different Re; (<b>e</b>) DSJ vs. DbSJ vs. DbCJ, all at 0 hd y-axis, Re = 16 k, different H; (<b>f</b>) DSJ vs. DbSJ vs. DbCJ, all at 0 hd y-axis, H = 5 hd, different Re.</p> Full article ">Figure 8
<p>Comparison of Nusselt number profiles of DSJ and DbSJ for different aspect ratios along the x-axis (sweeping direction): (<b>a</b>) AR = 1.20, Re = 16 k, different H; (<b>b</b>) AR = 1.20, H = 5 hd, different Re; (<b>c</b>) AR = 1.56, Re = 16 k, different H; (<b>d</b>) AR = 1.56, H = 5 hd, different Re; (<b>e</b>) DSJ, Re = 16 k, H = 5 hd, different AR; (<b>f</b>) DbSJ, Re = 16 k, H = 5 hd, different AR.</p> Full article ">

59 pages, 3714 KiB

Open AccessReview

Advances in Control Techniques for Rehabilitation Exoskeleton Robots: A Systematic Review

by Gazi Mashud, SK Hasan and Nafizul Alam

Actuators 2025, 14(3), 108; https://doi.org/10.3390/act14030108 - 21 Feb 2025

This systematic review explores recent advancements in control methods for rehabilitation exoskeleton robots, which assist individuals with motor impairments through guided movement. As robotics technology progresses, precise, adaptable, and safe control techniques have become accessible for effective human–robot interaction in rehabilitation settings. Key [...] Read more.

This systematic review explores recent advancements in control methods for rehabilitation exoskeleton robots, which assist individuals with motor impairments through guided movement. As robotics technology progresses, precise, adaptable, and safe control techniques have become accessible for effective human–robot interaction in rehabilitation settings. Key control methods, including computed torque and adaptive control, excel in managing complex movements and adapting to diverse patient needs. Robust and sliding mode controls address stability under unpredictable conditions. Traditional approaches, like PD and PID control schemes, maintain stability, performance, and simplicity. In contrast, admittance control enhances user–robot interaction by balancing force and motion. Advanced methods, such as model predictive control (MPC) and Linear Quadratic Regulator (LQR), provide optimization-based solutions. Intelligent controls using neural networks, Deep Learning, and reinforcement learning offer adaptive, patient-specific solutions by learning over time. This review provides an in-depth analysis of these control strategies by examining advancements in recent scientific literature, highlighting their potential to improve rehabilitation exoskeletons, and offering future recommendations for greater efficiency, responsiveness, and patient-centered functionality. Full article

(This article belongs to the Section Actuators for Robotics)

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<p>Flow chart of the search and inclusion process.</p> Full article ">Figure 2
<p>Robot dynamics including the friction model.</p> Full article ">Figure 3
<p>Computed torque control architecture.</p> Full article ">Figure 4
<p>Architecture of a sliding mode controller.</p> Full article ">Figure 5
<p>Architecture of a sliding mode controller with chattering suppressor.</p> Full article ">Figure 6
<p>Architecture of a Linear Quadratic Regulator.</p> Full article ">Figure 7
<p>Simplified control architecture of a PD controller.</p> Full article ">Figure 8
<p>Robot control architecture of a PID controller.</p> Full article ">Figure 9
<p>Generalized control architecture of an AI-based controller.</p> Full article ">

16 pages, 830 KiB

Open AccessArticle

Coupled Dynamics Modeling and Validation of Maglev Vehicle and Bridge Systems

by Fei Zhou and Xiaolong Li

Actuators 2025, 14(3), 107; https://doi.org/10.3390/act14030107 - 21 Feb 2025

To address the vehicle-bridge coupling vibration issue of the Qingyuan Maglev Tourist Line, it is necessary to establish a maglev vehicle–bridge coupling dynamics simulation model that reflects the actual line conditions. Based on the vehicle and bridge structural parameters of the Qingyuan Maglev [...] Read more.

To address the vehicle-bridge coupling vibration issue of the Qingyuan Maglev Tourist Line, it is necessary to establish a maglev vehicle–bridge coupling dynamics simulation model that reflects the actual line conditions. Based on the vehicle and bridge structural parameters of the Qingyuan Maglev Tourist Line, this paper utilizes multi-body dynamics simulation software to create a medium–low-speed maglev vehicle dynamics model, and employs finite element software to construct a bridge model. Using the modal reduction method, the bridge finite element model is imported into the vehicle dynamics model through a rigid–flex coupling interface, establishing a medium–low-speed maglev vehicle suspension system–bridge coupling dynamics model. The accuracy of the established coupling simulation model was verified by comparing the simulation data from the coupling model with the dynamic response measured data from the Qingyuan Maglev Tourist Line. Finally, the impact of different control parameters on the vehicle–bridge coupling system was calculated, and the results indicate that selecting appropriate suspension control parameters can reduce the coupling vibration response between the maglev vehicle and the bridge. The main work of this paper is closely related to engineering, modeling based on the actual maglev line’s vehicle and bridge parameters, and validating the model through the dynamic test results of the line, laying the foundation for the suppression of maglev vehicle–bridge coupling vibration and system optimization. Full article

(This article belongs to the Special Issue Advanced Theory and Application of Magnetic Actuators—2nd Edition)

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<p>Schematic diagram of medium- and low-speed maglev suspension frame structure.</p> Full article ">Figure 2
<p>Maglev Vehicle Dynamics Model.</p> Full article ">Figure 3
<p>Bridge finite element model.</p> Full article ">Figure 4
<p>Single-electromagnet suspension system model.</p> Full article ">Figure 5
<p>Block diagram of a two-stage series suspension control system.</p> Full article ">Figure 6
<p>Flowchart for importing a bridge finite element model into SIMPACK.</p> Full article ">Figure 7
<p>Flowchart for a maglev vehicle suspension system–bridge coupled dynamic modeling.</p> Full article ">Figure 8
<p>Maglev vehicle control system–bridge coupled dynamics model.</p> Full article ">Figure 9
<p>Schematic of the vehicle acceleration sensor placement: (<b>a</b>) Vehicle sensor placement points. (<b>b</b>) Suspension frame sensor placement points.</p> Full article ">Figure 10
<p>Comparison of test and simulation data for the vertical acceleration and frequency spectrum of the vehicle body: (<b>a</b>) Vertical acceleration of the vehicle body. (<b>b</b>) Frequency spectrum of the vertical acceleration of the vehicle body.</p> Full article ">Figure 11
<p>Comparison of test and simulation data for the vertical acceleration and frequency spectrum of the vehicle body: (<b>a</b>) Vertical acceleration of the vehicle body. (<b>b</b>) Frequency spectrum of the vertical acceleration of the vehicle body.</p> Full article ">Figure 12
<p>Comparison of test and simulation data for the vertical acceleration and frequency spectrum at the bridge mid-span: (<b>a</b>) Vertical acceleration at the bridge mid-span. (<b>b</b>) Frequency spectrum of the vertical acceleration at the bridge mid-span.</p> Full article ">Figure 13
<p>Plot of the dynamic response of the coupled system with varying suspension gap feedback coefficients: (<b>a</b>) Vertical acceleration of the vehicle body. (<b>b</b>) Vertical acceleration of the bridge.</p> Full article ">Figure 14
<p>Suspension gap fluctuation.</p> Full article ">Figure 15
<p>Plot of the dynamic response of the coupled system with varying suspension gap velocity feedback coefficients: (<b>a</b>) Vertical acceleration of the vehicle body. (<b>b</b>) Vertical acceleration of the bridge.</p> Full article ">Figure 16
<p>Suspension gap fluctuation.</p> Full article ">

31 pages, 6718 KiB

Open AccessArticle

A Study on a Speed Regulation Method for Mining Scraper Conveyors and a Control Strategy for Permanent Magnet Drive Systems

by Xi Zhang, Mingming Ren, Hongju Wang, Hongyu Xu, Bin Shi and Miaomiao Gao

Actuators 2025, 14(3), 106; https://doi.org/10.3390/act14030106 - 21 Feb 2025

To address the mismatch between materials and operational speed in mine scraper conveyors under time-varying load conditions, this paper proposes a methodology for the regulation of speed based on the quantity of coal transported by the scraper conveyor. Furthermore, a vector control strategy [...] Read more.

To address the mismatch between materials and operational speed in mine scraper conveyors under time-varying load conditions, this paper proposes a methodology for the regulation of speed based on the quantity of coal transported by the scraper conveyor. Furthermore, a vector control strategy for permanent magnet synchronous motors (PMSMs) is presented, underpinned by a global fast terminal sliding mode controller. Firstly, a calculation model for the real-time coal volume of the scraper conveyor was developed based on the double-end oblique cutting coal mining technology in fully mechanized mining operations. This model takes into account the operational condition of the shearer and the scraper conveyor. In addition, a graded speed regulation control method was introduced. Secondly, a global fast terminal controller was developed by integrating the features of linear and terminal sliding mode surfaces. An enhanced sliding mode vector control strategy for the permanent magnet drive motor of the scraper conveyor was subsequently proposed. Finally, a simulation and ground test were subsequently performed on the PMSM experimental bench and SGZ2×1200 scraper conveyor to validate the proposed control strategy. The results indicated that the proposed control strategy not only diminished the overshoot of the rotational speed and decreased the dynamic response time but also improved the anti-interference capabilities of the PMSM relative to the original PI control. Moreover, the ground test validated the feasibility of the suggested speed regulation method. Full article

(This article belongs to the Section Control Systems)

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Figure 1

Figure 1
<p>Diagram of coordinated operation of three machines on mining face.</p> Full article ">Figure 2
<p>The working processes of the shearer, cutting coal from the upper groove to the down groove: (<b>a</b>) process 1; (<b>b</b>) process 2; (<b>c</b>) process 3.</p> Full article ">Figure 3
<p>The working processes of the shearer, cutting coal from the down groove to the upper groove: (<b>a</b>) process 4; (<b>b</b>) process 5; (<b>c</b>) process 6.</p> Full article ">Figure 3 Cont.
<p>The working processes of the shearer, cutting coal from the down groove to the upper groove: (<b>a</b>) process 4; (<b>b</b>) process 5; (<b>c</b>) process 6.</p> Full article ">Figure 4
<p>Flowchart of the graded speed control method based on the coal loaded for the scraper conveyor.</p> Full article ">Figure 5
<p>A photograph of the operating trajectory of the shearer in the 15-21020 mining face.</p> Full article ">Figure 6
<p>The scraper conveyor’s output power for a production cycle: (<b>a</b>) rated speed; (<b>b</b>) graded speed regulation.</p> Full article ">Figure 7
<p>A structural comparison of the drive systems for the scraper conveyor: (<b>a</b>) head drive system; (<b>b</b>) tail drive system.</p> Full article ">Figure 8
<p>A block diagram of the PI current controllers.</p> Full article ">Figure 9
<p>The block diagram of the GFTSMC speed controller.</p> Full article ">Figure 10
<p>Block diagram of sliding mode speed controller based on GFTSMC.</p> Full article ">Figure 11
<p>Photograph of experimental platform: (1) RTU controller; (2) inverter; (3) DC power; (4) PMSM; (5) loading motor; (6) host computer.</p> Full article ">Figure 12
<p>Simulation curves of three control methods for PMSMs: (<b>a</b>) speed; (<b>b</b>) <span class="html-italic">d</span> axis current; (<b>c</b>) <span class="html-italic">q</span> axis current; (<b>d</b>) electromagnetic torque.</p> Full article ">Figure 13
<p>Speed curves of start-up conditions.</p> Full article ">Figure 14
<p>Speed curves of speed regulation experiments: (<b>a</b>) up-speed; (<b>b</b>) down-speed; (<b>c</b>) jump-speed.</p> Full article ">Figure 14 Cont.
<p>Speed curves of speed regulation experiments: (<b>a</b>) up-speed; (<b>b</b>) down-speed; (<b>c</b>) jump-speed.</p> Full article ">Figure 15
<p>A photograph of the experimental apparatus of the PMSM drive scraper conveyor: (1) head of the scraper conveyor; (2) tail of the scraper conveyor; (3) PMSM 1; (4) PMSM 2; (5) control box.</p> Full article ">Figure 16
<p>Test results of permanent magnet drive system under starting conditions: (<b>a</b>) speed; (<b>b</b>) current; (<b>c</b>) torque.</p> Full article ">Figure 17
<p>Test results of permanent magnet drive system under up-speed regulation conditions: (<b>a</b>) speed; (<b>b</b>) current; (<b>c</b>) torque.</p> Full article ">Figure 18
<p>Test results of permanent magnet drive system under down-speed regulation conditions: (<b>a</b>) speed; (<b>b</b>) current; (<b>c</b>) torque.</p> Full article ">

26 pages, 2295 KiB

Open AccessArticle

Robust Adaptive Cascade Trajectory Tracking Control for an Aircraft Towing and Taxiing System

by Weining Huang, Pengjie Xu, Tianrui Zhao, Wei Zhang and Yanzheng Zhao

Actuators 2025, 14(3), 105; https://doi.org/10.3390/act14030105 - 20 Feb 2025

With the rapid growth of the civil aviation industry, the aircraft towing and taxiing (ATT) system has gained significant attention in the literature. Due to its nonlinear and underactuated characteristics, the path tracking and control of the ATT system is a challenging issue. [...] Read more.

With the rapid growth of the civil aviation industry, the aircraft towing and taxiing (ATT) system has gained significant attention in the literature. Due to its nonlinear and underactuated characteristics, the path tracking and control of the ATT system is a challenging issue. Therefore, in this paper, a robust adaptive cascade control structure is proposed for the path tracking of the ATT system. Firstly, the system description is established via kinematic and dynamics modeling, and the lumped system disturbance is derived for the controller design. Next, the robust adaptive cascade control structure consisting of the adaptive MPC and the CSMC or the RASMC-based dynamics controller is designed with the application of the extended Kalman filter. The system stability in the dynamics loop is verified through the Lyapunov method. The simulation results reveal that the combination of the adaptive MPC and the RASMC can provide a more accurate tracking performance and smoother trajectories under the given disturbances and uncertainties, while both ensuring passenger comfort and meeting the civil aviation regulations, indicating its potential in practical applications. Full article

(This article belongs to the Special Issue Flight Control Systems and Dynamic Simulation for Aerospace Applications)

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Figure 1

Figure 1
<p>Illustration of the aircraft towing and taxiing operation.</p> Full article ">Figure 2
<p>Schematic diagram of the ATT system.</p> Full article ">Figure 3
<p>The designed robust adaptive cascade control structure for the ATT system.</p> Full article ">Figure 4
<p>Path tracking performance of the two control strategies.</p> Full article ">Figure 5
<p>Path tracking error of the ATT system.</p> Full article ">Figure 6
<p>Trajectory tracking errors of the ATT system.</p> Full article ">Figure 7
<p>Trajectories of the control inputs.</p> Full article ">Figure 8
<p>Trajectories of the aircraft velocities.</p> Full article ">Figure 9
<p>Trajectories of the hitch angles.</p> Full article ">Figure 10
<p>Torques of rear wheel motors on the tractor.</p> Full article ">

25 pages, 4799 KiB

Open AccessArticle

Optimized Structural Design of a Reciprocating Wing for the Reciprocating Airfoil (RA)-Driven Vertical Take-Off and Landing (VTOL) Aircraft

by Johnson Imumbhon Okoduwa, Osezua Obehi Ibhadode and Yiding Cao

Actuators 2025, 14(3), 104; https://doi.org/10.3390/act14030104 - 20 Feb 2025

The development of unconventional and hybrid unoccupied aerial vehicles (UAVs) has gained significant momentum in recent years, with many designs utilizing small fans or rotary blades for vertical take-off and landing (VTOL). However, these systems often inherit the limitations of traditional helicopter rotors, [...] Read more.

The development of unconventional and hybrid unoccupied aerial vehicles (UAVs) has gained significant momentum in recent years, with many designs utilizing small fans or rotary blades for vertical take-off and landing (VTOL). However, these systems often inherit the limitations of traditional helicopter rotors, including susceptibility to aerodynamic inefficiencies and mechanical issues. Additionally, achieving a seamless transition from VTOL to fixed-wing flight mode remains a significant challenge for hybrid UAVs. A novel approach is the reciprocating airfoil (RA) or reciprocating wing (RW) VTOL aircraft, which employs a fixed-wing configuration driven by a reciprocating mechanism to generate lift. The RA wing is uniquely designed to mimic a fixed-wing while leveraging its reciprocating motion for efficient lift production and a smooth transition between VTOL and forward flight. Despite its advantages, the RA wing endures substantial stress due to the high inertial forces involved in its operation. This study presents an optimized structural design of the RA wing through wing topology optimization and finite element analysis (FEA) to enhance its load-bearing capacity and stress performance. A comparative analysis with existing RA wing configurations at maximum operating velocities highlights significant improvements in the safety margin, failure criteria, and overall stress distribution. The key results of this study show an 80.4% reduction in deformation, a 43.8% reduction in stress, and a 78% improvement in safety margin. The results underscore the RA wing’s potential as an effective and structurally stable lift mechanism for RA-driven VTOL aircraft, demonstrating its capability to enhance the performance and reliability of next-generation UAVs. Full article

(This article belongs to the Special Issue Aerospace Mechanisms and Actuation—Second Edition)

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Figure 1

Figure 1
<p>UAV classification overview.</p> Full article ">Figure 2
<p>(<b>a</b>) Forward stroke of the reciprocating cycle, (<b>b</b>) reverse stroke of the reciprocating cycle, (<b>c</b>) RA aircraft conceptual design, (<b>d</b>) RA module conceptual design. Reprinted from [<a href="#B55-actuators-14-00104" class="html-bibr">55</a>,<a href="#B57-actuators-14-00104" class="html-bibr">57</a>].</p> Full article ">Figure 3
<p>The flow chart of the current study.</p> Full article ">Figure 4
<p>RA wing design (<b>a</b>) internal structure and (<b>b</b>) complete structure.</p> Full article ">Figure 5
<p>Workflow of the topology optimization process implemented in nTopology.</p> Full article ">Figure 6
<p>The three optimized wing structures. (<b>a</b>) The first design (mass fraction of 0.65), (<b>b</b>) the second design (mass fraction of 0.63), and (<b>c</b>) the third design (mass fraction of 0.67).</p> Full article ">Figure 7
<p>Depiction of the FEA results: (<b>a</b>) comparison across different iterations and (<b>b</b>) comparison of the RA wing at maximum velocity and the topology-optimized RA wing at maximum velocity.</p> Full article ">Figure 8
<p>Illustration of the FEA results: total deformation (mm) and maximum stress (MPa) from the three wing design iterations.</p> Full article ">Figure 8 Cont.
<p>Illustration of the FEA results: total deformation (mm) and maximum stress (MPa) from the three wing design iterations.</p> Full article ">Figure 9
<p>Topology-optimized wing. (<b>a</b>) Illustration of the topology-optimized wing framework and shell/skin and (<b>b</b>) full wing shell and structure.</p> Full article ">Figure 10
<p>Examples of advanced air mobility eVTOL industry players.</p> Full article ">

18 pages, 5366 KiB

Open AccessArticle

Regenerative Structural Fatigue Testing with Digital Displacement Pump/Motors

by Win Rampen, Marek J. Munko, Sergio Lopez Dubon and Fergus Cuthill

Actuators 2025, 14(3), 103; https://doi.org/10.3390/act14030103 - 20 Feb 2025

Historically, a large fraction of fatigue testing of both components and structures has been performed using hydraulic actuators. These are typically driven by servo-valves, which are in themselves very inefficient. But, as most tests involve elastically stressing mechanical components, a lot of stored [...] Read more.

Historically, a large fraction of fatigue testing of both components and structures has been performed using hydraulic actuators. These are typically driven by servo-valves, which are in themselves very inefficient. But, as most tests involve elastically stressing mechanical components, a lot of stored energy could be recovered. Unfortunately, servo-valves are not regenerative—simply metering out fluid in order to relax the system prior to the start of the next cycle. There is much to be gained with a more intelligently controlled system. The FastBlade facility in Scotland uses a new type of regenerative test hydraulics. Digital displacement pump/motors (DDPMs), originated by Artemis Intelligent Power, now Danfoss Scotland, are used to load and unload the test structure directly via hydraulic rams. The DDPMs are driven by induction motors supplied by three-phase frequency converters, each with a very loose speed correction target, such that they can speed up or slow down according to the instantaneous torque exerted by the load. The rotating assembly of the induction motor and DDPM is designed to have sufficient inertia so as to function as a kinetic energy storage flywheel. The loading energy is then cyclically transferred between the rotating inertia of the motor/DDPM and the spring energy in the test structure. The electric motor provides sufficient energy to maintain the target average cyclical shaft speed of the DDPM whilst the bulk of the system energy oscillates between the two storage mechanisms. Initial tests (at low load) suggest that this technique requires only 30% of the energy previously needed. FastBlade is a unique facility built by the University of Edinburgh and Babcock, with support from the UK EPSRC, conceived as a means of testing and certifying turbine blades for marine current turbines. However, this approach can be used in any cyclical application where elastic energy is stored. Full article

(This article belongs to the Special Issue Actuation and Control in Digital Fluid Power)

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Figure 1
<p>Simplified schematic of a regenerative hydraulic loading circuit with reversing energy flows.</p> Full article ">Figure 2
<p>Cross-section of an early DDP, illustrating basic conformation and components.</p> Full article ">Figure 3
<p>Rendering of loading frame, jacking actuators, strong wall, and test specimen at FastBlade.</p> Full article ">Figure 4
<p>Photo of the actual FastBlade facility with a short specimen blade on the test.</p> Full article ">Figure 5
<p>Photo of the undercroft where the four Artemis/Danfoss DDPMs are housed. The main level decking can be seen at the top of the photo, and the side of the loading frame is visible on the extreme right.</p> Full article ">Figure 6
<p>A simplified schematic of the hydraulic loading system, consisting of an oil reservoir, a DDPM unit, an adjustable pressure compensated flow control valve, a loading jack, and a load cell.</p> Full article ">Figure 7
<p>Traces of both the flywheel speed and the desired load acting on the specimen specimen deflection showing the energy exchange, both in amplitude and phase. The two vertical lines represent the phase shift, showing the maximum flywheel speed to be slightly leading to the minimum displacement.</p> Full article ">Figure 8
<p>Regeneration test, where power to the VLT is cut at 5 s. (<b>a</b>) The loading cycle continues, slightly diminishing in amplitude cycle by cycle until transferred energy sinks to 1/3rd of the initial amount after 25 cycles. (<b>b</b>) Motor speed slows after power is cut at 5 s. If loading is also stopped, then the system runs down following the smooth red trace. If loading continues, then the speed reduction is slightly faster. The small difference in speed decay illustrates the high round-trip efficiency of the loading system. (<b>c</b>) The energy that is being cycled between the flywheel and load also diminishes with time, but not in a way that might be recognised as a logarithmic decrement. For the first 3 s, after power is cut to the VLT, loading energy remains relatively constant since the flywheel can source the required energy in the time available. As flywheel speed drops, the energy that can be transferred also diminishes.</p> Full article ">Figure 9
<p>The relation between the power losses and the angular velocity of a DDPM for four operating modes: low pressure (LP), medium pressure (MP), high pressure (HP), and idle.</p> Full article ">Figure 10
<p>Sankey diagram for the loading portion of the cycle. It can be seen from the change in speed during the loading cycle that 2.2 kJ given up by the flywheel during its deceleration are passed through to the strain energy in the specimen, and the VLT makes up the rest, as well as supplying the various parasitic losses in the circuit.</p> Full article ">Figure 11
<p>Sankey diagram for the unloading phase of the cycle. Here, 3.37 kJ of energy are given up by the relaxing test specimen and directed to help accelerate the flywheel. The VLT once again makes up for losses.</p> Full article ">Figure 12
<p>Relative cycle input energy for the FastBlade DDPM regenerative system compared to a calculated approximation for a conventional proportional valve with a variable pump and accumulator supply.</p> Full article ">

17 pages, 1151 KiB

Open AccessArticle

Numerical Analysis of a Hypersonic Body Under Thermochemical Non-Equilibrium and Different Catalytic Surface Conditions

by Odelma Teixeira and José Páscoa

Actuators 2025, 14(2), 102; https://doi.org/10.3390/act14020102 - 19 Feb 2025

This work results from a numerical investigation of the thermochemical non-equilibrium effects on the surface properties of a hypersonic body. Non-equilibrium within an air mixture composed of 11 chemical species was considered when solving the Navier–Stokes–Fourier equations using a density-based algorithm in OpenFOAM. [...] Read more.

This work results from a numerical investigation of the thermochemical non-equilibrium effects on the surface properties of a hypersonic body. Non-equilibrium within an air mixture composed of 11 chemical species was considered when solving the Navier–Stokes–Fourier equations using a density-based algorithm in OpenFOAM. The influence of thermal and chemical non-equilibrium on the surface properties of a hypersonic double-cone test body was studied by considering two types of surfaces. It was found that the heat flux and pressure distribution along the surface are higher under non-equilibrium free-stream conditions. Unlike what was observed at the impingement point, where the vibrational non-equilibrium effects on the surface properties are almost independent of the surface type, at the stagnation point, these effects are highly dependent on the catalytic activity of the surface. At the stagnation point, the vibrational non-equilibrium effects are more pronounced on a fully catalytic surface than on a non-catalytic surface. Under the studied conditions, the vibrational non-equilibrium reduces the heat flux by 18% for a non-catalytic surface, while for a fully catalytic surface, it reduces the heat flux by 38%. Additionally, the presence of vibrational non-equilibrium in the free-stream reduces the pressure by 24% for a non-catalytic surface, while for a fully catalytic surface, it is reduced by 42%. Full article

(This article belongs to the Special Issue Flow Control and Beyond Enhancing Performance and Energy Efficiency in Complex Fluid System)

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Figure 1
<p>Simulation model diagram.</p> Full article ">Figure 2
<p>Double-cone model: (<b>a</b>) geometric parameters (dimensions in cm); (<b>b</b>) solution domain and boundary conditions.</p> Full article ">Figure 3
<p>Code validation: (<b>a</b>) heat flux; (<b>b</b>) pressure. Distribution along the double-cone surface.</p> Full article ">Figure 4
<p>Grid convergence analysis: (<b>a</b>) maximum heat flux location; (<b>b</b>) size of the separation zone.</p> Full article ">Figure 5
<p>Pressure contours considering five-species (top) and eleven-species air mixtures (bottom).</p> Full article ">Figure 6
<p>Vibro-electronic temperature contours at equilibrium and non-equilibrium free-stream conditions for: (<b>a</b>) five-species air mixture; (<b>b</b>) eleven-species air mixture.</p> Full article ">Figure 7
<p>Surface heat flux distribution along the double-cone surface for five-species and eleven-species air mixtures for different free-stream conditions: (<b>a</b>) equilibrium; (<b>b</b>) non-equilibrium.</p> Full article ">Figure 8
<p>Surface pressure distribution along the double-cone surface for five-species and eleven-species air mixture for different free-stream conditions: (<b>a</b>) equilibrium; (<b>b</b>) non-equilibrium.</p> Full article ">Figure 9
<p>Distribution of surface properties for equilibrium and non-equilibrium conditions: (<b>a</b>) heat flux; (<b>b</b>) pressure. Comparison between non-catalytic surface (NCS) and fully catalytic surface (FCS).</p> Full article ">Figure 10
<p>Distribution of flow properties along the impingement point line (Y = 0.052 m) for equilibrium and non-equilibrium conditions: (<b>a</b>) pressure; (<b>b</b>) trans-rotational temperature (<math display="inline"><semantics> <msub> <mi mathvariant="normal">T</mi> <mrow> <mi>t</mi> <mi>r</mi> </mrow> </msub> </semantics></math>); (<b>c</b>) vibro-electronic temperature (<math display="inline"><semantics> <msub> <mi mathvariant="normal">T</mi> <mrow> <mi>v</mi> <mi>e</mi> </mrow> </msub> </semantics></math>). Comparison between non-catalytic surface (NCS) and fully catalytic surface (FCS).</p> Full article ">Figure 11
<p>Temperature distributions along the stagnation line (Y = 0 m) for equilibrium and non-equilibrium conditions: (<b>a</b>) trans-rotational (<math display="inline"><semantics> <msub> <mi mathvariant="normal">T</mi> <mrow> <mi>t</mi> <mi>r</mi> </mrow> </msub> </semantics></math>); (<b>b</b>) vibro-electronic temperature (<math display="inline"><semantics> <msub> <mi mathvariant="normal">T</mi> <mrow> <mi>v</mi> <mi>e</mi> </mrow> </msub> </semantics></math>). Comparison between non-catalytic surface (NCS) and fully catalytic surface (FCS).</p> Full article ">

23 pages, 8016 KiB

Open AccessArticle

Flow Characteristics of a Dual Sweeping Jet Impinging on a Flat Surface

by Muhammad Zubair and Xin Wen

Actuators 2025, 14(2), 101; https://doi.org/10.3390/act14020101 - 19 Feb 2025

The dual sweeping jet (DSJ)-producing fluidic oscillator is a novel device developed by sharing a feedback channel between two standard fluidic oscillators. This device produces a pair of sweeping jets in the outer domain and has the potential to be used for the [...] Read more.

The dual sweeping jet (DSJ)-producing fluidic oscillator is a novel device developed by sharing a feedback channel between two standard fluidic oscillators. This device produces a pair of sweeping jets in the outer domain and has the potential to be used for the better and uniform treatment of impinged surfaces. Therefore, it is important to investigate the extent of the synchronicity of these jets at different Re numbers and various aspect ratios in outer domains, and to comprehend their internal switching mechanism simultaneously. The time-averaged flow fields demonstrated that, at lower Re numbers, both sweeping jets were symmetric about their centerlines and the cores were strong. The strength of the cores deteriorated at higher Re numbers, and the flare regions became wider and stronger. Moreover, the transverse velocities pulled the sweeping jets away from the origin and a high upwash flow formed in-between the jets. The phase-averaged flow fields vividly illustrated the sharing mechanism between the two power nozzles through the formation of left- and right-loops consecutively in the shared feedback channel. These primary loops generated an auxiliary mechanism on both sides of a fluidic oscillator, which actually controlled the synchronicity of the two sweeping jets in the outer domain. Additionally, they also showed that both jets are properly synchronized and have strong cores at lower Re numbers. However, at higher Re numbers, greater velocities were found in the switching and sweeping mechanisms which caused asynchrony between the sweeping jets but nonetheless impinged a larger area and covered the region in-between the jets properly. The power nozzles were also found to self-feed themselves due to the hindrance at the ‘outer shoulders’ of this fluidic oscillator and hence caused the premature formation of a recirculation bubble of vorticity between the power nozzle and its respective outer island. Lastly, the aspect ratio analysis revealed that the asynchrony of DSJ at higher Re numbers can be mitigated by reducing the aspect ratio. Full article

(This article belongs to the Special Issue Active Flow Control: Recent Advances in Fundamentals and Applications—3rd Edition)

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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schematic of DSJ fluidic oscillator (<b>a</b>) and its computational domain (<b>b</b>).</p> Full article ">Figure 2
<p>Numerical model validation at H = 7 hd: (<b>a</b>) Strouhal numbers for Re 1800 to 9200, (<b>b</b>) Ratio of Peak Velocities for Re 9200. Wen et. al. 2018 [<a href="#B4-actuators-14-00101" class="html-bibr">4</a>].</p> Full article ">Figure 3
<p>Time-averaged contours at Re 1800, AR 2.34: (<b>a</b>) velocity magnitude (streamwise), (<b>b</b>) velocity magnitude (sweeping direction), (<b>c</b>) turbulent fluctuations (streamwise), (<b>d</b>) turbulent fluctuations (sweeping direction).</p> Full article ">Figure 4
<p>Phase-averaged contours at Re 1800, AR 2.34.</p> Full article ">Figure 5
<p>Time-averaged contours at Re 5500, AR 2.34: (<b>a</b>) velocity magnitude (streamwise), (<b>b</b>) velocity magnitude (sweeping direction), (<b>c</b>) turbulent fluctuations (streamwise), (<b>d</b>) turbulent fluctuations (sweeping direction).</p> Full article ">Figure 6
<p>Phase-averaged contours at Re 5500, AR 2.34.</p> Full article ">Figure 7
<p>Time-averaged contours at Re 9200, AR 2.34: (<b>a</b>) velocity magnitude (streamwise), (<b>b</b>) velocity magnitude (sweeping direction), (<b>c</b>) turbulent fluctuations (streamwise), (<b>d</b>) turbulent fluctuations (sweeping direction).</p> Full article ">Figure 8
<p>Phase-averaged contours at Re 9200, AR 2.34.</p> Full article ">Figure 9
<p>Time-averaged contours of (<b>a</b>) velocity magnitude (streamwise), (<b>b</b>) velocity magnitude (sweeping direction), (<b>c</b>) turbulent fluctuations (streamwise), (<b>d</b>) turbulent fluctuations (sweeping direction) for the external flow field only at Re 9200: (<b>A</b>) AR 1.5, (<b>B</b>) AR 1.0.</p> Full article ">Figure 10
<p>Phase-averaged oscillation for one cycle: contours of time-averaged velocity for both the internal and external flow fields at Re 9200: (<b>A</b>) AR 1.5, (<b>B</b>) AR 1.0.</p> Full article ">

22 pages, 6734 KiB

Open AccessArticle

Envelope Morphology of an Elephant Trunk-like Robot Based on Differential Cable–SMA Spring Actuation

by Longfei Sun and Huiying Gu

Actuators 2025, 14(2), 100; https://doi.org/10.3390/act14020100 - 19 Feb 2025

Most trunk-like robots are designed with distributed actuators to mimic the envelope-grasping behavior of elephant trunks in nature, leading to a complex actuation system. In this paper, a modular underactuated elephant trunk-imitating robot based on the combined drive of the cable and shape [...] Read more.

Most trunk-like robots are designed with distributed actuators to mimic the envelope-grasping behavior of elephant trunks in nature, leading to a complex actuation system. In this paper, a modular underactuated elephant trunk-imitating robot based on the combined drive of the cable and shape memory alloy (SMA) springs is designed. Unlike the traditional underactuated structure that can only passively adapt to the envelope of the object contour, the proposed elephant trunk robot can control the cable tension and the equivalent stiffness of the SMA springs to achieve active control of the envelope morphology for different target objects. The overall structure of the elephant trunk robot is designed and the principle of deformation envelope is elucidated. Based on the static model of the robot under load, the mapping relationship between the tension force and the tension angle between modules is derived. The positive kinematic model of the elephant trunk robot is established based on the Debavit–Hartenberg (D–H) method, the spatial position of the elephant trunk robot is obtained, and the Monte Carlo method is used to derive the robot’s working space. The active bending envelope grasping performance is further verified by building the prototype to perform grasping experiments on objects of various shapes. Full article

(This article belongs to the Section Actuators for Robotics)

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Figure 1

Figure 1
<p>Elephant trunk function: (<b>a</b>) Elephant trunk muscle composition; (<b>b</b>) Elephant trunk curled objects.</p> Full article ">Figure 2
<p>Elephant trunk structure: (<b>a</b>) Elephant trunk [<a href="#B19-actuators-14-00100" class="html-bibr">19</a>]; (<b>b</b>) 3D model of elephant trunk-like robot; (<b>c</b>) Modular structure.</p> Full article ">Figure 3
<p>3D model of the unit module: (<b>a</b>) Front view; (<b>b</b>) Back view.</p> Full article ">Figure 4
<p>Force analysis: (<b>a</b>) Simplified model; (<b>b</b>) Mechanical model.</p> Full article ">Figure 5
<p>Robot envelope morphology: (<b>a</b>) Envelope spherical body; (<b>b</b>) Envelope trapezoid; (<b>c</b>) Envelope polygon.</p> Full article ">Figure 6
<p>D–H Coordinate system of elephant trunk robot.</p> Full article ">Figure 7
<p>Workspace: (<b>a</b>) Three-dimensional view of the workspace; (<b>b</b>) Workspace projection in x–y plane.</p> Full article ">Figure 8
<p>Adams model of elephant trunk robot: (<b>a</b>) Adams model (<b>b</b>) Tension spring damper setting (<b>c</b>) Back view.</p> Full article ">Figure 9
<p>Angle curve for elephant trunk robot: (<b>a</b>) Group 1; (<b>b</b>) Group 2; (<b>c</b>) Group 3; (<b>d</b>) Group 4.</p> Full article ">Figure 10
<p>Simulation results of robot envelope morphology: (<b>a</b>) Group 1 (<span class="html-italic">F</span> = 18.8 N, <span class="html-italic">R</span><sub>1</sub> ≈ 18 mm); (<b>b</b>) Group 2 (<span class="html-italic">F</span> = 11.7 N, <span class="html-italic">R</span><sub>2</sub> ≈ 28 mm) (<b>c</b>) Group 3 (<span class="html-italic">F</span> = 7.8 N, <span class="html-italic">R</span><sub>3</sub> ≈ 50 mm); (<b>d</b>) Group 4 (<span class="html-italic">F</span> = 11.3 N, <span class="html-italic">R</span><sub>4</sub> ≈ 80 mm).</p> Full article ">Figure 11
<p>Elephant trunk robot prototype.</p> Full article ">Figure 12
<p>Experimental system components.</p> Full article ">Figure 13
<p>The control system of the elephant trunk robot.</p> Full article ">Figure 14
<p>Mechanical property test experiment of SMA spring.</p> Full article ">Figure 15
<p>SMA spring tension response.</p> Full article ">Figure 16
<p>Variation of contraction force and elongation of SMA spring.</p> Full article ">Figure 17
<p>Elephant trunk envelope morphology: (<b>a</b>) <span class="html-italic">F</span><sub>1</sub> = 8 N; (<b>b</b>) <span class="html-italic">F</span><sub>2</sub> = 10 N; (<b>c</b>) <span class="html-italic">F</span><sub>3</sub> = 12 N.</p> Full article ">Figure 18
<p>Elephant trunk robot grasps objects: (<b>a</b>) Envelope egg (without active SMA springs); (<b>b</b>) Envelope tennis; (<b>c</b>) Envelope cube; (<b>d</b>) Envelope cup; (<b>e</b>) Envelope apple; (<b>f</b>) Envelope cylinder.</p> Full article ">

17 pages, 15169 KiB

Open AccessArticle

Research on the Five-Axis Support-Free Additive Manufacturing Method for Overhanging Parts

by Xingguo Han, Gaofei Wu, Xuan Liu, Wenquan Li, Xiaohui Song and Lixiu Cui

Actuators 2025, 14(2), 99; https://doi.org/10.3390/act14020099 - 19 Feb 2025

When printing overhanging parts with traditional additive manufacturing (AM) equipment, it is necessary to add support structures under the overhanging structure. The process of printing support structures not only wastes materials, but also increases the manufacturing time. Therefore, in order to reduce or [...] Read more.

When printing overhanging parts with traditional additive manufacturing (AM) equipment, it is necessary to add support structures under the overhanging structure. The process of printing support structures not only wastes materials, but also increases the manufacturing time. Therefore, in order to reduce or eliminate the need for support structures when printing parts with overhanging structures, such as propellers, a five-axis support-free printing method for overhanging parts is proposed for one of the most commonly used processes involving AM technology: fused deposition modeling (FDM). By offsetting the surface of the basic part, the offset surface is intersected with the model to be printed to obtain the spatial surface-layered curve. The contour offset method for the spatial curve is used to obtain the printing path, and continuous path planning is performed on it. While the presented method is targeted specifically at this ideal overhanging part, physical experiments on five-axis FDM equipment are performed. Compared with the traditional three-axis AM method, the time taken to print parts using this support-free five-axis AM method is shortened by 13.76–26.93%, and the printing material required is reduced by 17.24–29.29%. The experimental results show that this method realizes support-free printing of overhanging parts with the five-axis AM equipment, which not only saves materials and time consumed during part of the printing, but also improves the surface quality of the parts. Full article

(This article belongs to the Section Actuators for Manufacturing Systems)

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Figure 1
<p>Model of five-axis AM device.</p> Full article ">Figure 2
<p>Forward kinematics analysis of five-axis AM device.</p> Full article ">Figure 3
<p>Inverse kinematics analysis of a five-axis AM device.</p> Full article ">Figure 4
<p>Basic steps in the five-axis AM method.</p> Full article ">Figure 5
<p>Basic steps in curved layer slicing: (<b>a</b>) the propeller model; (<b>b</b>) the surface to be offset; (<b>c</b>) one of the overhanging parts of the model; (<b>d</b>) the layered curves.</p> Full article ">Figure 5 Cont.
<p>Basic steps in curved layer slicing: (<b>a</b>) the propeller model; (<b>b</b>) the surface to be offset; (<b>c</b>) one of the overhanging parts of the model; (<b>d</b>) the layered curves.</p> Full article ">Figure 6
<p>Path planning for a continuous curve: (<b>a</b>) the initial layering curve marked in red; (<b>b</b>) the initial outer contour marked in green; (<b>c</b>) the initial inner filling curve marked in blue.</p> Full article ">Figure 7
<p>Path planning for a continuous curve: (<b>a</b>) the start and end points of the offset curve; (<b>b</b>) the continuous curve.</p> Full article ">Figure 8
<p>Flowchart of the five-axis AM system.</p> Full article ">Figure 9
<p>The printing experiment: (<b>a</b>) a model of the part; (<b>b</b>) the five-axis AM platform; (<b>c</b>) the manufacturing process.</p> Full article ">Figure 10
<p>Comparison of the parts manufactured using different methods: (<b>a</b>) the part manufactured using the three-axis AM method; (<b>b</b>) the part manufactured using the five-axis AM method.</p> Full article ">Figure 11
<p>Comparison of the top surface of the parts manufactured using different methods: (<b>a</b>) one of overhanging parts of the model manufactured by three-axis AM method (red box); (<b>b</b>) one of overhanging parts manufactured by five-axis AM method (green box).</p> Full article ">Figure 12
<p>The bottom surface of the overhanging parts that printed by three-axis AM method (red dotted box) and the five-axis AM method (green dotted box).</p> Full article ">Figure 13
<p>The manufacturing process for the propeller part: (<b>a</b>) the first paddle; (<b>b</b>) the second paddle; (<b>c</b>) the last paddle.</p> Full article ">

15 pages, 3935 KiB

Open AccessArticle

Study on the Vibration Characteristics of Separated Armature Assembly in an Electro-Hydraulic Servo Valve Under Interference Fit

by Tong Li, Jinghui Peng, Songjing Li, Juan Zhang and Aiying Zhang

Actuators 2025, 14(2), 98; https://doi.org/10.3390/act14020098 - 19 Feb 2025

The electro-hydraulic servo valve is a critical component that transforms electrical signals into hydraulic signals, thereby controlling the hydraulic system. It finds extensive application in precision control systems. The stability of the electro-hydraulic servo valve is primarily influenced by the armature assembly. Unlike [...] Read more.

The electro-hydraulic servo valve is a critical component that transforms electrical signals into hydraulic signals, thereby controlling the hydraulic system. It finds extensive application in precision control systems. The stability of the electro-hydraulic servo valve is primarily influenced by the armature assembly. Unlike integral armature assembly, the separated armature assembly, comprising the armature, spring tube, flapper, and feedback spring, is joined through an interference fit, which introduces prestress within the assembly. The existence of prestress may affect the operational mode of the armature assembly. Consequently, this paper investigates the vibration characteristics of the separated armature assembly under interference fit conditions. Comparative analysis reveals that interference fit indeed generates prestress, which cannot be overlooked. To further validate the reliability of the simulation results, the natural frequency of the separated armature assembly is determined by applying a sweeping frequency signal to the torque motor using an electric drive, thereby verifying the feasibility of the simulation analysis. Additionally, the impact of interference on the vibration characteristics of the separated armature assembly is examined, confirming the accuracy of the simulation analysis method based on the interference fit. The research on vibration characteristics of a separated armature assembly provides technical support for the structural optimization design of the electro-hydraulic servo valve, thereby enhancing its performance. Full article

(This article belongs to the Special Issue Recent Developments in Precision Actuation Technologies)

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Figure 1
<p>Separated armature assembly.</p> Full article ">Figure 2
<p>Meshing. (<b>a</b>) Node coupling is not considered in meshing; (<b>b</b>) node coupling is considered in meshing.</p> Full article ">Figure 3
<p>Contact setting.</p> Full article ">Figure 4
<p>Calculation results.</p> Full article ">Figure 5
<p>Deformation nephogram.</p> Full article ">Figure 6
<p>Stress nephogram.</p> Full article ">Figure 7
<p>Modal analysis results under interference fit. (<b>a</b>) First-order vibration mode. (<b>b</b>) Second-order vibration mode. (<b>c</b>) Third-order vibration mode. (<b>d</b>) Fourth-order vibration mode. (<b>e</b>) Fifth-order vibration mode. (<b>f</b>) Sixth-order vibration mode.</p> Full article ">Figure 8
<p>Modal test of armature assembly. (<b>a</b>) Schematic diagram of the experimental system. (<b>b</b>) Data acquisition system.</p> Full article ">Figure 9
<p>Frequency domain analysis of armature end displacement under sweep signal.</p> Full article ">Figure 10
<p>The influence of interference on the modes of armature assembly. (<b>a</b>) The influence of interference between the armature and the spring tube on the modes. (<b>b</b>) The influence of interference between the spring tube and the flapper on the modes. (<b>c</b>) The influence of interference between the flapper and the feedback spring on the modes.</p> Full article ">Figure 10 Cont.
<p>The influence of interference on the modes of armature assembly. (<b>a</b>) The influence of interference between the armature and the spring tube on the modes. (<b>b</b>) The influence of interference between the spring tube and the flapper on the modes. (<b>c</b>) The influence of interference between the flapper and the feedback spring on the modes.</p> Full article ">

23 pages, 1136 KiB

Open AccessArticle

A Reasoned Attempt to Mitigate Vibrations in Nonlinear Flexible Systems Influenced by Tractive–Elastic Rolling Contact Friction Through Input Shaping: A Case Study on a Trolley–Pipe Benchmark Transport System

by Gerardo Peláez, Pablo Izquierdo, Gustavo Peláez and Higinio Rubio

Actuators 2025, 14(2), 97; https://doi.org/10.3390/act14020097 - 17 Feb 2025

The well-regarded feedforward control strategy known as Input Shaping is aimed at improving the dynamic response of flexible mechanical systems by reducing overshoot and residual vibration amplitude. Its validity has been confirmed by numerous studies dealing with linear system dynamics. However, its application [...] Read more.

The well-regarded feedforward control strategy known as Input Shaping is aimed at improving the dynamic response of flexible mechanical systems by reducing overshoot and residual vibration amplitude. Its validity has been confirmed by numerous studies dealing with linear system dynamics. However, its application in nonlinear systems, particularly those influenced by tractive–elastic rolling contact friction, remains a challenging and less explored open research area. This paper investigates whether Input Shaping, without tractive rolling friction compensation, can effectively mitigate vibrations in a trolley–pipe benchmark transport system. In this system, the pipe is modeled as a rolling disc attached to the trolley by a spring at its center of mass, while the trolley itself is connected to a guiding body frame by an additional spring acting as a proportional control. The natural frequencies of the system are analytically estimated and numerically verified from a corresponding well-suited multibody model. Thus, tailored two-mode shapers are designed based on simultaneous constraints and the convolution sum, respectively. Through multibody simulations, this study evaluates the performance of Input Shaping under tractive–elastic rolling contact friction conditions. The findings highlight both the potential and limitations of this control method in addressing nonlinear mechanical systems influenced by tractive–elastic rolling contact friction. Full article

(This article belongs to the Special Issue Nonlinear Active Vibration Control)

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Figure 1

Figure 1
<p>Application Unshaped and ZV-filtered responses to a step input: The unshaped input and its corresponding response are shown on the left, while the shaped input and the resulting vibration-suppressed response appear on the right.</p> Full article ">Figure 2
<p>(<b>a</b>) Physical representation of the mass-spring-damper system under gross-sliding friction force. (<b>b</b>) Block diagram representation of the system dynamics by the Laplace model.</p> Full article ">Figure 3
<p>Response of the mass-spring system under gross-slip friction, without the derivative damper action, to a nonzero initial position. Conditions: <math display="inline"><semantics> <mrow> <mi>k</mi> <mo>=</mo> <mn>5</mn> </mrow> </semantics></math> [N/m], <math display="inline"><semantics> <mrow> <mi>m</mi> <mo>=</mo> <mn>0.20</mn> </mrow> </semantics></math> [Kg], <math display="inline"><semantics> <mrow> <mi>μ</mi> <mo>=</mo> <mn>0.15</mn> </mrow> </semantics></math>.</p> Full article ">Figure 4
<p>Elastic rolling contact of a cylinder rolling freely on a plane under normal load P.</p> Full article ">Figure 5
<p>(<b>a</b>) Reference model of a two-mass and spring system undergoing rolling friction. (<b>b</b>) Impulse response of the rolling disc, showing the nearly undamped x-position of the mass center.</p> Full article ">Figure 6
<p>Steel coil transport system in manufacturing plants.</p> Full article ">Figure 7
<p>The Multibody System is broken up into the spring element ① and the super-element ②.</p> Full article ">Figure 8
<p>Simscape Mechanical Explorer Sketch of the system showing the body frames.</p> Full article ">Figure 9
<p>Simscape (Matlab) multibody model of the system showing bodies interconnected by kinematics joints plus a large number of important multibody formalisms by rigid frame transforms plus body and joint customizations.</p> Full article ">Figure 10
<p>FFT of the signal corresponding to the abscissa position of the center of mass of the pipe. Low-frequency component value 0.079998 [Hz]. High-frequency component 0.159997 [Hz].</p> Full article ">Figure 11
<p>Convolved two-mode ZVD-ZVD shaper for <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mn>1</mn> </msub> </mrow> </semantics></math>: 0.07998 and <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mn>2</mn> </msub> </mrow> </semantics></math>: 0.159997 Hz undamped frequencies.</p> Full article ">Figure 12
<p>Two-mode input shaper by simultaneous constraints for <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mn>1</mn> </msub> </mrow> </semantics></math>: 0.07998 and <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mn>2</mn> </msub> </mrow> </semantics></math>: 0.159997 [Hz] and <math display="inline"><semantics> <mrow> <mi>ζ</mi> </mrow> </semantics></math>: 0.0.</p> Full article ">Figure 13
<p>Trapezoidal input motion. Conditions: the ramp-up lasts for <math display="inline"><semantics> <mrow> <mi>t</mi> <msub> <mi>t</mi> <mn>1</mn> </msub> </mrow> </semantics></math>: 17 [s]. Unshaped input motion. Direct–ZVD-ZVD shaped input motion. Conditions: ramp-up lasts for <math display="inline"><semantics> <mrow> <mi>t</mi> <msub> <mi>t</mi> <mn>1</mn> </msub> <mo>+</mo> <msub> <mi>T</mi> <mn>5</mn> </msub> </mrow> </semantics></math>: 33 [s].</p> Full article ">Figure 14
<p>Multibody model pipe mass center X-position responses to trapezoidal input motion profile with 12 s ramp-up. Pipe mass center X-position unshaped response. Pipe mass center X-position shaped response for direct–ZVD-ZVD shaped input motion.</p> Full article ">Figure 15
<p>Trapezoidal input motion. Conditions: the ramp-up lasts for <math display="inline"><semantics> <mrow> <mi>t</mi> <msub> <mi>t</mi> <mn>1</mn> </msub> </mrow> </semantics></math>: 20 [s]. Unshaped input motion. Convolved–ZVD-ZVD shaped input motion.</p> Full article ">Figure 16
<p>Experimental trapezoidal input motion profile responses. Pipe mass center X-position unshaped response. Pipe mass center X-position for convolved–ZVD-ZVD shaped response.</p> Full article ">

20 pages, 7919 KiB

Open AccessArticle

Design and Performance Analysis of an All-Metal Phase-Change-Material Actuator for Enhanced Sealing and Displacement Output Characteristics

by Shuaiqi Guo, Xianwei Yang and Qingwen Wu

Actuators 2025, 14(2), 96; https://doi.org/10.3390/act14020096 - 16 Feb 2025

The phase-change-material (PCM) actuator, a non-pyrotechnic technology in aerospace, offers enhanced safety and convenience. This paper presents a novel PCM actuator featuring an all-metal construction to improve reliability and sealing. Characterized by high energy density and temperature-dependent actuation, the actuator’s displacement output characteristics [...] Read more.

The phase-change-material (PCM) actuator, a non-pyrotechnic technology in aerospace, offers enhanced safety and convenience. This paper presents a novel PCM actuator featuring an all-metal construction to improve reliability and sealing. Characterized by high energy density and temperature-dependent actuation, the actuator’s displacement output characteristics (DOCs) are examined through visualization experiments. The results show the formation of a concave gap within the PCM upon cooling, which can be controlled by adjusting the cooling load and temperature to minimize its impact on displacement output. A two-dimensional physical model is developed to investigate how varying thermophysical parameters and boundary conditions affect the phase change process and DOC. The study finds that increasing the thermal conductivity of the PCM and surface heat flow enhances displacement velocity, although the effect diminishes at higher values. Additionally, reducing latent heat significantly boosts output velocity. For a fixed surface heat flow, changes in wall thickness have a minor impact, with velocity variation under 2%. Full article

(This article belongs to the Section Actuator Materials)

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Figure 1

Figure 1
<p>Energy density of different actuator materials (adapted by the author) [<a href="#B2-actuators-14-00096" class="html-bibr">2</a>].</p> Full article ">Figure 2
<p>Design of the PCM actuator in a cross-sectional view.</p> Full article ">Figure 3
<p>PCM is enclosed within the actuator by CMH and a knife-edge flange.</p> Full article ">Figure 4
<p>Experimental system.</p> Full article ">Figure 5
<p>Thermal expansion coefficient vs. temperature relationship of paraffin wax upon heating at a very slow velocity [<a href="#B24-actuators-14-00096" class="html-bibr">24</a>] with fitted curve.</p> Full article ">Figure 6
<p>The comparison of the simulation results between the numerical result (Num) and experimental result (Kong, Q.) [<a href="#B19-actuators-14-00096" class="html-bibr">19</a>].</p> Full article ">Figure 7
<p>Computational domains and boundary conditions.</p> Full article ">Figure 8
<p>The performed analyses for the grid number (<b>a</b>) and time-step size (<b>b</b>) independence tests.</p> Full article ">Figure 9
<p>Sealing results displayed after 50 repetitions.</p> Full article ">Figure 10
<p>The out displacement of actuator comparing different cases.</p> Full article ">Figure 11
<p>Concave PCM state after solidification.</p> Full article ">Figure 12
<p>Schema of central gap in different cases.</p> Full article ">Figure 13
<p>The temperature (<b>left</b>) and thermal strain (<b>right</b>) for the simulation result.</p> Full article ">Figure 14
<p>The results of experimental (Exp) and numerical calculation (Num).</p> Full article ">Figure 15
<p>Displacement output results after 10% parameter change. (<b>a</b>) k, (<b>b</b>) L, (<b>c</b>) δ<sub>w</sub>, and (<b>d</b>) heat flux.</p> Full article ">Figure 16
<p>Results of the t<sub>ps</sub> and u<sub>ps</sub> for the 0.5× to 2.0× parameters. (<b>a</b>) k, (<b>b</b>) L, (<b>c</b>) δ<sub>w</sub>, and (<b>d</b>) heat flux.</p> Full article ">Figure 17
<p>Results of the average velocity and velocity variation for the 0.5× to 2.0× parameters. (<b>a</b>) k, (<b>b</b>) L, (<b>c</b>) δ<sub>w</sub>, and (<b>d</b>) heat flux.</p> Full article ">

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