Chapter 21 - Morphing Devices Safety Reliability A - 2018 - Morphing Wing Tec
Chapter 21 - Morphing Devices Safety Reliability A - 2018 - Morphing Wing Tec
Chapter 21 - Morphing Devices Safety Reliability A - 2018 - Morphing Wing Tec
CHAPTER OUTLINE
1 Introduction ................................................................................................................................... 648
2 System Level Approaches to the Certification of Morphing Wing Devices ........................................... 650
2.1 Adaptive Droop Nose ...................................................................................................... 652
2.2 Adaptive Trailing Edge Device ......................................................................................... 652
2.3 Morphing Winglet .......................................................................................................... 653
2.4 Defining the System Level Functions of Morphing Devices ................................................ 654
2.5 Dual Level Safety ........................................................................................................... 656
3 Functional Hazard Assessment ........................................................................................................ 657
4 Dual-Level Approach for the FTA of a Morphing Wing ....................................................................... 675
5 Common Cause Analyses ................................................................................................................ 678
5.1 Particular Risk Analysis .................................................................................................. 680
5.2 Common Mode Analysis ................................................................................................. 680
5.3 Zonal Safety Analysis ..................................................................................................... 680
6 Conclusions ................................................................................................................................... 681
References ........................................................................................................................................ 681
NOMENCLATURE
A/C aircraft
AIAA American Institute of Aeronautics and Astronautics
ARP aerospace recommended practices
ATED adaptive trailing edge device
CCA common cause analyses
1 INTRODUCTION
Despite the considerable interest and the growing advances in morphing wing technologies, morphing
devices continue to be perceived as highly difficult to certify by the aviation industry. Although several
morphing wing concepts and demonstrators already were tested in representative environment [1–5]
and, in some cases, even flight tested [6,7], the certification roadmap of these advanced mechanical
systems still suffers from certain safety-related gaps in the attempt to comply with current certification
requirements.
At this time, the authors are not aware of the use of morphing devices in any commercial aircraft.
Two fundamental questions still remain to be addressed: What changes or additions to the traditional
certification processes would be necessary to demonstrate that morphing devices comply with the cer-
tification standards? And is there any room for some nontraditional means of compliance? Answering
to these questions not only would allow for safe use of such highly integrated systems that perform
complex and interrelated aircraft-level functions, but also could result in a successful progress in
the certification prospects of morphing wing structures.
1 INTRODUCTION 649
In this chapter, some gaps in the design approach of morphing devices are discussed in order to
provide sufficient consistency with current standards in aviation. The use of acceptable safety-related
design methodologies, combined with more automated manufacturing, assembly, and integration pro-
cesses, appear to be the most adequate means to certify these mechanical systems within the context of
industry standards. Additionally, beyond structural factors or other considerations of airworthiness to
prevent catastrophic failures, the novel aircraft functions enabled by morphing systems imposes a
thorough examination of the associated risks that can have an impact on aircraft flight capabilities
and crew workload. As with all the other aircraft control surfaces and systems, the real challenge is
to show whether the safety targets are met, until the single system is assessed and the interaction
between conventional and adaptive systems performing different functions are collectively evaluated
at aircraft (A/C) system level. More reliance on verification by analysis, simulation, and limited proofs
of concepts from the early design phase could lead to partial certification credit while preserving the
essential features of safety.
Government Certification agencies such as the Federal Aeronautical Administration (FAA) and the
European Aviation Safety Agency (EASA) require that aircraft manufacturers follow precise design
and certification policies to manage and mitigate systems failure risks throughout the operational life
of an airplane. Historical evidence indicates that the probability of a serious accident because of
operational and airframe-related causes is approximately one per million hours of flight, and only about
10% of the total are attributed to failure conditions (FCs) caused by A/C systems [8]. The process of
identifying risks and quantifying or qualifying the degree of risk they pose to individuals and resources
is usually referred to as safety assessment [9]. A probability approach is typically used to manage these
assessments. A logical and acceptable inverse relationship must exist between the average probability
per flight hour (FH) and the severity of FC effects, as shown in Fig. 1. Catastrophic failures must be
FIG. 1
Relationship between probability and severity of failure condition effects.
650 CHAPTER 21 MORPHING DEVICES
extremely improbable and must not result from a single failure [8]. The upper limit for the average
probability per FH for catastrophic FCs shall be 1 10 9, which establishes an approximate probability
value for the term “extremely improbable.” On the other hand, FCs having less severe effects could be
relatively more likely to occur, with upper average probability limits equal to 1 10 7 and 1 10 5 per
FH for hazardous and major, respectively.
According to the EASA CS-25 regulations applicable to large commercial aircraft, safety assess-
ments consist of three major phases, i.e., functional hazard assessment (FHA), preliminary system
safety assessment (PSSA), and system safety assessment (SSA), which consider the interactions among
the aircraft systems, between software and hardware (HW) components, and all the interfaces, includ-
ing pilot and crew. In this frame, systems functions are examined qualitatively to identify potential
design, maintenance or crew faults, and external environment risks. The severity of these hazards is
determined and placed in specific classes, indicative of the maximum tolerable probability of occur-
rence. After that, the link between faults at subsystems level and their end-effects are evaluated in the
FHA, by taking into account the actual system constraints throughout the system lifetime. Each hazard
is quantitatively examined in a top-down fashion, from the events to their causes, until failures of the
basic components are classified. On the basis of the probabilities assigned to failure events of the basic
components, the probability of occurrence of the top event is then calculated. Such a quantitative anal-
ysis usually is achieved with the fault tree (FT) technique.
Starting from a generic overview of A/C system functions, this chapter follows a standard safety
analysis to define both qualitative and quantitative requirements to support the certification practices of
morphing devices with respect to safety and reliability targets. Two main documents combined with the
certification specifications (CS)-25 EASA regulations [8] are considered as guidelines: Society of Au-
tomotive Engineer (SAE) ARP 4754a [9] and SAE ARP 4761 [10]. A complete aircraft FHA, including
morphing systems and functions, is outside the scope of this study. Integrated use of three morphing
devices—droop nose, morphing trailing edge, and adaptive winglet—is assessed through the imposi-
tion of certain constraints after the design phase of the morphing architecture and permitted adaptation
to meet specific system safety properties. Because of the concepts novelty, literature references about a
safety-driven design of morphing devices are hard to find, for both new-generation aircraft and retrofit
applications. Furthermore, the identification and classification of the potential failures of morphing
devices might be a nontrivial exercise. Finally, not all the necessary analysis and modeling tools
are available in the literature and further work might be required to bring such an approach to practical
applications. Because of these points, a conservative approach is used to assign the functional systems
failure severities and safety targets by developing and sharing a high-level mapping between a func-
tional view of morphing devices and their A/C safety-related standards.
• Morphing on the order of minutes: Lift (and drag) control during long mission segments (mainly
cruise) to compensate aircraft weight reduction because of fuel consumption.
2 SYSTEM LEVEL APPROACHES TO THE CERTIFICATION 651
• Morphing on the order of seconds: Active lift distribution control to minimize drag during
short off-design mission segments (mainly climbing and turning operations).
• Morphing in less than a second: Wing load alleviation by reducing gust-induced root bending
moment (RBM) peaks on aircraft wing.
For some recent-generation aircraft, such as Boeing 787 and Airbus A350, some novel aircraft func-
tions, such as differential flap setting, already are performed by innovative flap actuation system con-
cepts. Distributed actuation enables decentralized load control along the wing span, which is
particularly suited for active lift distribution control for induced drag reduction. More tailored control
systems and inherent positioning sensors contribute to guarantee this functionality.
A standard system safety assessment of aircraft systems, whose the key phases are shown in Fig. 2,
must consider both the crew workload and operation implications of potential failures by establishing
key capabilities and related limitations.
As part of the certification process, after requirement analysis has been completed, the top-level
requirements assigned through the aircraft level FHA need to flow down to next level (the morphing
wing system FHA), and subsequently to lower levels, such us morphing devices FHA. Without a
specific A/C application, a generic set of aircraft level functions can be chosen arbitrarily to define
high-level links between enhanced morphing system functions and standard aircraft functions by
identifying, at the same time, the criticalities associated with the FCs. The analyses are intended at
subsystem level, and performed with a typical bottom-up approach.
The SSA invokes a quantitative analysis of the FTs generated for potential failures with hazardous
or catastrophic consequences. The reliability data of the system components are necessary to calculate
FIG. 2
Safety process overview diagram.
652 CHAPTER 21 MORPHING DEVICES
basic events probability figures which are typically requested to the components suppliers (commonly
required by contract and by equipment specification) prior to the system integration and assembly
phases.
We will elaborate on the safety process assessment approach by focusing on three morphing
systems:
A/C functions enabled by these systems are identified individually as explicitly requested by safety-
related standards. It is assumed that for a safe integration of such morphing devices in a morphing wing,
they are rigidly connected to a wing box without losing any deployment performance because of struc-
tural interactions. After that, their impact on A/C operation is evaluated by assessing their individual
and combined A/C level functions and hazards.
FS
1.5
10–9 10–5 1
Q - Probability of being in failure condition
FIG. 3
Computation of the safety factor [8].
Aircraft functions
FIG. 4
Aircraft top-level functions.
2 SYSTEM LEVEL APPROACHES TO THE CERTIFICATION 655
integrity also can be taken into account because of the structural load alleviation, protection, and con-
trol function, as seen in A/C function 8: Provide containment and internal support. An exploded view of
the aircraft level functions is given in the Table 2. High-level functions that might be potentially in-
volved by the use of an adaptive trailing edge device can be linked to the A/C function: Plan, generate,
and control A/C movement.
The functional safety analysis of a morphing wing concept and integrating different and indepen-
dently actuated morphing devices, must be performed at two different levels: the morphing wing level
and the single morphing device level. In order to integrate such results, a clear mapping of aircraft level
functions, morphing system functions, and physical devices becomes mandatory. These links create the
basis for a clear matching between the top-down morphing wing FHA and the bottom-up morphing
wing subsystems FHAs.
Table 3 Functional Link Between Aircraft Level and Morphing System Functions
Morphing System
Functions Aircraft Level Functions
Drag minimization 2. Plan, generate and control A/C 2.2.5.1 Control lift and drag
function movement 2.2.7 Provide aerodynamic control forces
Lift adaptation function 2. Plan, generate and control A/C 2.2.5.1 Control lift and drag
movement 2.2.7 Provide aerodynamic control forces
2.2.13 Generate lift
2.2.14 Provide aerodynamic stability
Turbulence/gust load 2. Plan, generate and control A/C 2.2.6.1 To provide protection against turbulence
alleviation movement effects
Maneuvers load 2. Plan, generate and control A/C 2.2.8.2 To provide protection against maneuvers
alleviation movement effects
Vibration and fatigue 8. Provide containment and 8.1.2.1 To provide fatigue protection
control internal support
A/C load protection 2. Plan, generate and control A/C 2.2.6.2 To provide protection against stall load
movement 2.2.8.1 To provide overload protection and A/C
load protection
This work proposes a dual-level functional link, as reported in Tables 3 and 4. By combining these
tables, it is possible to draft the functional, logical and architectural relationships among aircraft level
functions, morphing wing system, functions and morphing device functions.
• Identified FCs.
• Effects of FCs.
• Classification of each FC based on the identified effects.
• A statement summarizing the assumptions used for classifying each FC (e.g., adverse operational or
environmental conditions and phase of flight).
A discrete scale allows the categorization of the severity of the effects of a FC according to the CS-25
regulation criteria. The classification levels are defined as: Catastrophic, hazardous, major, major,
658 CHAPTER 21 MORPHING DEVICES
Morphing device 01
physical
Morphing device 02
behavior
physical
Morphing device 03
behavior
physical
behavior
FIG. 5
Dual level safety process overview.
minor, or no safety effect, depending on the related impact on aircraft operation and crew workload, as
follows [8]:
No safety effect: FCs that have no effect on safety and do not affect the operational capability of the
airplane or increase crew workload. As a safety target, these failures have no probability requirement.
Minor: FCs that do not significantly reduce airplane safety, and that involve crew actions that are
well within their capabilities. Minor FCs include, for example, a slight reduction in safety margins or
functional capabilities, a slight increase in crew workload, such as routine flight plan changes, or some
physical discomfort to passengers or cabin crew. When using quantitative analyses, these failures are
3 FUNCTIONAL HAZARD ASSESSMENT 659
commonly accepted as probable, i.e., FCs having an average probability per FH less than the order of
1 10 5.
Major: FCs that reduce the capability of the airplane or the ability of the crew to cope with adverse
operating conditions. For example, a significant reduction in safety margins or functional capabilities, a
significant increase in crew workload or in conditions impairing crew efficiency, or discomfort to the
flight crew, or physical distress to passengers or cabin crew, possibly including injuries. When using
quantitative analyses, these failures are commonly accepted as remote, i.e., FCs having an average
probability per FH greater than of the order of 1 10 5, but less than of the order of 1 10 7.
Hazardous: FCs that reduce the capability of the airplane or the ability of the crew to cope with
adverse operating conditions resulting in a large reduction in safety margins or functional capabilities,
an excessive workload to the flight crew or a serious or fatal injury to a relatively small number of the
occupants other than the flight crew. When using quantitative analyses, these failures are commonly
accepted as extremely remote, i.e., FCs having an average probability per FH greater than the order of
1 10 7 or less than of the order of 1 10 9.
Catastrophic: FCs that result in multiple fatalities, usually with the loss of the airplane. When using
quantitative analyses, these failures are commonly accepted as extremely improbable, i.e., FCs having
an average probability per FH greater than of the order of 1 10 9.
The goal of this step is to clearly identify the circumstances and severity of each FC along with the
rationale for its classification. For every identified morphing wing function, the following FCs can be
considered:
• Loss of function (total or partial).
• Erroneous provision of function.
• Inadvertent provision of function.
An example of subsystem level FHA developed in the framework of SARISTU project for the morph-
ing trailing edge device is shown in Table 5 [20]. The main information from the FHA includes
• The failure mode identification number.
• The failure mode description.
• The flight phase in which the failure mode can occur.
• The severity classification referred to CS-25 norms and the resulting probability figure required to
comply with CS-25 safety regulations.
• The FC details.
• A description of the A/C level effects.
• The detection method (if detection is possible).
• The flight crew reaction after failure detection (if detection is possible).
• The possible requirements coming from safety considerations (e.g., redundancy requirements,
inspections, etc.).
• The external events involved in the hazard (if applicable).
• The justification for safety categorization following CS-25 regulations.
Both qualitative and quantitative requirements result from the FCs safety classification. The typical
example is an electromechanical actuator (EMA) jamming. This failure mode leads to a FC that
can be identified with a functional loss. In detail, if the actuator allows the EMA-based morphing de-
vice to be configured to reduce drag, its jamming leads to a drag minimization function loss. As a result,
660 CHAPTER 21 MORPHING DEVICES
Loss of wing shape FC01 Loss of Loss of ATED All MIN- 1E-3/FH
optimization function ATED control function flight MAJ 1E-5/FH
phases
Erroneous provision of FC02 Erratic Erratic ATED All MAJ 1E-5/FH
wing shape ATED control function flight
optimization function phases
Inadvertent provision of FC03 Uncommanded All MIN- 1E-3/FH
wing shape Uncommanded ATED function flight MAJ 1E-5/FH
optimization function ATED control phases
Partial loss wing shape FC04 Symmetric Symmetric partial All MIN- 1E-3/FH
control capability partial loss of loss of ATED flight MAJ 1E-5/FH
(symmetric) ATED function function phases
Asymmetric partial loss FC05 Asymmetric Asymmetric partial All MAJ 1E-5/FH
of wing shape control partial loss of loss of ATED flight
capability ATED function function phases
Partial loss of wing FC06 Partial loss Loss of ATED Landing MAJ- 1E-5/FH
shape control capability of ATED control on one wing HAZ 1E-7/FH
(asymmetric) combined (asymmetric) (asymmetric)
with one engine loss at combined with combined with one
landing one engine loss at engine loss at
landing landing
Partial loss of wing FC07 Partial loss Loss of ATED Landing MAJ- 1E-5/FH
shape control capability of ATED control on one wing HAZ 1E-7/FH
(asymmetric) combined (Asymmetric) (asymmetric)
with strong cross-wind combined with combined with
at take-off or landing strong cross wind strong cross-wind at
at landing landing
the qualitative requirement becomes a driver for the system architecture definition and affects both the
actuation kinematics and the deployment logics. In case of a safety critical systems, the morphing
device also must be designed with a proper integrity level and redundancies. Monitoring of safety
critical functions is a safety target for system designers: morphing wing surfaces that cause forced
oscillations or free floating, potentially resulting in wing structural collapse, must be designed with
a fail-safe approach (e.g., mass balancing preventing free float induced vibrations) or with an indepen-
dent control/monitor architecture that can prevent forced oscillations.
The ATED fault hazard assessment is also applicable at morphing wing system level for the
identification of the FCs. They are listed in Table 6. The main criticalities associated with the simul-
taneous use of different morphing devices could include:
• The droop nose device can cause a sudden stall, possible catastrophic scenario in case of take-off
and landing phases (no time for the pilot to perform recovery actions).
Table 6 Fault Hazard Assessment of a Morphing Wing Incorporating a Droop Nose, a Morphing Trailing Edge Device,
and an Adaptive Winglet
Safety Requirement Traceability
A/C External
ID Failure Flight Failure Cause/ Event or
Mode Title Phase(s) Severity Objective Involved Subsystem WATE ATE EADN Condition
1 2.2.5.1-01 Loss of wing All flight MAJ 1E-5/FH FC 2.2.5.1-01: Total 1.c 1.1– Row 2
Drag shape phases loss of SARISTU (FC2); 1.4
minimization/ optimization wing shape control 1.e
lift adaptation function capability (including (FC6)
jamming)
– Loss of WATE
quasistatic
operation
– Loss of ATE
661
quasistatic
operation
Continued
662
Table 6 Fault Hazard Assessment of a Morphing Wing Incorporating a Droop Nose, a Morphing Trailing Edge Device,
and an Adaptive Winglet—cont’d
Safety Requirement Traceability
663
Continued
664
Table 6 Fault Hazard Assessment of a Morphing Wing Incorporating a Droop Nose, a Morphing Trailing Edge Device,
and an Adaptive Winglet—cont’d
Safety Requirement Traceability
665
Continued
666
Table 6 Fault Hazard Assessment of a Morphing Wing Incorporating a Droop Nose, a Morphing Trailing Edge Device,
and an Adaptive Winglet—cont’d
Safety Requirement Traceability
667
occasional gust
load alleviation
function
efficiency
Continued
Table 6 Fault Hazard Assessment of a Morphing Wing Incorporating a Droop Nose, a Morphing Trailing Edge Device,
668
and an Adaptive Winglet—cont’d
Safety Requirement Traceability
669
maneuvers load
alleviation
function provided
when not required
Continued
670
Table 6 Fault Hazard Assessment of a Morphing Wing Incorporating a Droop Nose, a Morphing Trailing Edge Device,
and an Adaptive Winglet—cont’d
Safety Requirement Traceability
671
continuous
function to
control fatigue
loads
Continued
672
Table 6 Fault Hazard Assessment of a Morphing Wing Incorporating a Droop Nose, a Morphing Trailing Edge Device,
and an Adaptive Winglet—cont’d
Safety Requirement Traceability
673
Continued
674
Table 6 Fault Hazard Assessment of a Morphing Wing Incorporating a Droop Nose, a Morphing Trailing Edge Device,
and an Adaptive Winglet—cont’d
Safety Requirement Traceability
The morphing droop nose device is a single subsystem that can cause a catastrophic failure because of
the possible detachment of aerodynamic flow after an erroneous deployment. For this device, no com-
mon cause can lead to this scenario. A single functional design assurance level (FDAL) A or a dual
FDAL B design is necessary to match the safety requirements [9] (see SAE ARP 4754a for details).
Furthermore, because of the dynamic deployment, an independent control/monitor architecture
must be implemented into the adaptive winglet to prevent induced oscillations. A symmetric deploy-
ment check (with the possibility to stop the morphing devices if an asymmetry is detected) is also fun-
damental to prevent failure case scenarios and to comply with the quantitative safety targets to make the
selected architectures certifiable and airworthy.
Regarding the possibility to achieve wing load/vibrations alleviation/control functions with fast-
actuated morphing devices, the CS-25 regulations impose that the additional load caused by the failed
morphing device shall be considered in the design load. The consequence is that every related FC (from
the structural standpoint) is classified no more than minor in the frame of morphing wing FHA. Finally,
it has to be noted that although software functions should be considered in the FHA and the proper DAL
shall be assigned, these topics are not discussed because they are outside the scope of this chapter.
These can be found within the referenced documents [9].
Failure condition
identified at
subsystem/device
level
SUBSYS1_FC1
SUBSYS1_GATE1 SUBSYS1_GATE2
of failure of the top event was then analyzed along with its compliancy with the expected severity with
the purpose of making ATED a sufficiently reliable device for aircraft application.
Several indexes, such as actuator position control, motor shaft angle sensors, and actuator absorbed
power, can help reveal ATED failures. The construction of the FT is based on relationships between
events and causes, represented by means of logical and or gates, which solve the system complexity and
Asymmetric
Partial Loss
ASYM_LOSS
Loss of Loss of
Right_ATED Left_ATED
LOSS_RIGHT_ATED LOSS_LEFT_ATED
Q = 5,254E-05
FR = 5,254E-05
Actuation beam/
Linear guide ATED WB Actuator / Spar Primary hinges Secondary
Actuator failure Actuation crank morphing rib Links fail
failure attachment attachment fail hinges fail
attachment
FIG. 7
Fault tree example with failure rates per hour for asymmetric partial loss of ATED function [20].
677
678 CHAPTER 21 MORPHING DEVICES
its potential failures. To this aim, the failure probability of each basic component of the morphing ki-
nematics must be collected.
The main drawback associated with the use of electromechanical actuators is mechanical failure or
jamming, which can typically lead to hazardous/catastrophic A/C FCs. Conversely, according to the
ATED FHA, asymmetric ATED failure caused, for example, by actuators jamming, is classified as
major. This means that the associated impact on wing loads can be reduced by acting on conventional
aircraft control surfaces on the basis of the detected ATED shapes. Nevertheless, although minimal
impacts are expected on A/C controllability, pilot workload increases in order to trim the aircraft lon-
gitudinally and laterally. In addition, safety margins on aircraft block fuel must be considered to com-
pensate the potential loss of ATED functions in flight.
Although the failure rate of the top event is not fully compliant with the safety requirement
(Failure rate for major events: 1.0E-5/FH), the investigated architecture does not incorporate any
standard device for detecting and minimizing asymmetric conditions onboard aircraft. The easiest
option can include, for instance, an ATED position sensor and a brake system that can be activated
automatically to stop further ATED movement after the position sensors detect any asymmetric sit-
uation. Their use would allow the ATED meeting the safety requirements starting from a failure rate
of 0.1 per FH. For morphing systems performing load (static or dynamic) alleviation such as the
adaptive winglet, a dual command and monitoring lane with its own control unit (ECU) is mandatory
to guarantee an adequate redundancy. In addition, an acceptable number of linear variable displace-
ment transducers (LVDTs) mounted to the actuator ball screw and angular sensors are needed for
operational reliability.
An example of higher level FTA is shown in Fig. 8. The potential failures at the morphing wing
level are a combination of subsystems (single morphing devices) failure cases with proper exposure
factors or external events. If a failure mode does not have immediate and detectable effect, the related
events are called “latent” or “dormant.” Commercial FT software can be used to evaluate these events
through mathematical models. Latent or dormant failures can be detected only with specific func-
tional tests or maintenance actions. Proper inspection intervals also can be scheduled to satisfy safety
requirements. The currently available technology is able to minimize the certification maintenance
requirement (CMR) with the implementation of self-test ability, in particular for complex electronic
devices.
WING_FC1
Combination of
morphing wing
subsystems failures
leading to morphing
wing hazard
WING_GATE1
r=0
Proper protection of cable and pipe routings must be considered in order to minimize zonal safety haz-
ards. Some previously exposed hazards seem to derive from the combination of at least two indepen-
dent failures. For example, in case of electrical cables/connectors positioned near fuel or hydraulic
REFERENCES 681
pipes, the fire/explosion event can be envisaged only if an electrical arc/spark is generated (failure of
cable or connector) in combination with a flammable fuel leakage (pipe rupture).
6 CONCLUSIONS
The design of morphing devices must not compromise the aircrafts general performance and intrinsic
functions. This chapter covers the major safety and reliability aspects associated with the design and
integration of morphing systems into an aircraft wing. The summary recommendation is that a three-
step strategy is needed for a safe use and successful certification of morphing devices. This strategy
consists of individual and combined safety assessments, followed by system design activities to comply
with the corresponding safety requirements, and design assurance using the latest A/C safety standards.
For future applications, theoretical and detailed simulations must support these steps along with model-
based design techniques. Furthermore, the verification process of the system level functional and safety
target can require different testing plans and tools to assess the associated risks. Although the chapter
has focused on some particular morphing devices and types, such a flow and recommendations are
likely to be applicable to a wider variety of morphing concepts.
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