KR101257793B1 - Method for controlling a very high speed parallel robot using a synchronization of multi-axis motion - Google Patents

Abstract

The present invention relates to a control method of a high speed parallel robot based on a synchronization method of multiple axes, and more particularly to a high speed parallel robot that effectively controls a high speed parallel robot by using a tracking error and a synchronization error for each joint of the parallel robot. Control method of the robot.
According to the present invention, precise parallel robot control is performed by adjusting the reflection ratio of the synchronization error by reflecting a synchronization error indicating a movement between the joints of each arm and a reference error representing a reference trajectory and a synchronization between the joints. Becomes possible.
In addition, another effect of the present invention is that it is possible to reduce the load while implementing control accuracy of the parallel robot control system by using the dependent control method without using an independent control method.
In addition, another effect of the present invention is that it is possible to reduce the synchronization error by reflecting the reference trajectory of the other joint to the feedforward control input.

Description

Method for controlling a very high speed parallel robot using a synchronization of multi-axis motion}

The present invention relates to a control method of a high speed parallel robot based on a synchronization method of multiple axes, and more particularly, to a high speed parallel type which effectively controls a parallel robot by using a tracking error and a synchronization error for each joint of the parallel robot. To control the robot.

In general, a parallel robot has a structure in which a plurality of robot arms are tied to one end device unlike a serial robot so that a plurality of arms move simultaneously to send the end device to a desired position. Therefore, there is an advantage that a heavier object can be handled more quickly than a serial robot.

In addition, such a parallel robot has an advantage in that the force to endure in the axial direction is greater and the accuracy is higher than that of the serial robot.

Accordingly, a parallel robot is a robot that controls a plurality of arms to implement a plurality of degrees of freedom, and parallel robots of various structures have been manufactured and are widely used in industrial robots.

By the way, in the case of such a parallel robot, a control system is comprised in order to control this parallel robot. However, the conventional control system does not reflect error correction due to synchronization considering tracking errors of other axes by independently controlling each axis of the CPU and the parallel robot. There is a problem that precise control of a plurality of arms is difficult.

In addition, according to the conventional method, since a plurality of arms must be controlled in real time, a large amount of processing is required in order to accurately send to a desired target position in a three-dimensional space, which causes a large load on the control system.

The present invention has been proposed to improve the control accuracy of a parallel robot, and a high speed parallel robot based on a multi-axis synchronization method capable of precise control of a plurality of arms by reflecting error correction according to synchronization between the axes of the parallel robot. The purpose is to provide a control method.

In addition, another object of the present invention is to provide a control method of a high-speed parallel robot based on a synchronization method of a plurality of axes capable of reducing synchronization error by reflecting a reference trajectory of another joint to the feedforward control input.

The present invention provides a control method of a high-speed parallel robot based on a synchronization method of a plurality of axes, in order to achieve the object raised above. The control method of the high speed parallel robot includes: a target trajectory information input step of inputting target trajectory information of each joint unit as a user controls the operation of the parallel robot; A feedback step of an encoder feeding back the current position information of each joint part to the motion controller according to the motion of each joint part; A tracking error calculating step of calculating, by a central processing unit, a tracking error of each joint part by comparing the target trajectory information with current position information; A synchronization error calculating step of calculating a synchronization error by using a tracking error of an i-th joint part and a tracking error of a previous and next joint part of the following joint part among the tracking errors of each joint part; A feedback control information calculation step of generating a feedback control information by a PID (Proportional-Integral-Derivative) controller calculating a total error using the tracking error and the synchronization error; A feed forward control information calculating step of generating, by a feed forward controller, feed forward control information by using a sum of the target trajectories of the respective joint portions and adjusting a reflection ratio of each joint portion with a constant parameter; A total control input information calculating step of generating, by the total control input information generating unit, a total control input using the sum of the feedback control information and the feed forward control information; And a joint unit driving step of driving each joint unit by driving a motor driving unit according to the overall control input information.

In this case, the current position information of each joint part may follow the target trajectory information of each joint part.

(여기서,

는 i번째 관절부의 각의 목표 궤적을,

는 i번째 관절부의 각을 나타낸다)으로 정의되는 것을 특징으로 한다. Here, the tracking error is the following equation,

(here,

Is the target trajectory of the angle of the i-th joint,

Denotes an angle of the i-th joint portion).

으로 정의되는 것을 특징으로 한다. Here, the synchronization error is the following equation,

Characterized in that defined.

(여기서,

는 추종오차이고,

는 동기화 오차를 나타내며,

는 동기화 오차의 반영비율을 조정하는 상수 파라미터를 나타낸다)으로 정의되는 것을 특징으로 한다. Here, the combined error (coupled error) is the following equation,

(here,

Is a tracking error,

Represents a synchronization error,

Denotes a constant parameter for adjusting the reflectance ratio of the synchronization error).

Here, the total control input is the following equation,

은 e의 미분치를 나타낸다)으로 정의되는 것을 특징으로 한다. Where K _p , K _d , and K _i are As a control parameter, it shows position error gain value, speed error gain value, and integral gain value of position error, respectively.

Is the derivative of e).

The driving of the joint part may further include removing noise from the overall control input information by a filter unit.

According to the present invention, precise parallelism is achieved by adjusting the reflection ratio of the synchronization error by reflecting not only the tracking error indicating the reference trajectory indicating the difference between the joint portions of each arm and the synchronization error indicating the synchronization of the movement between the joint portions. Robot control is possible. That is, there is an effect that can improve the accuracy of the control.

In addition, another effect of the present invention is that it is possible to reduce the synchronization error by reflecting the reference trajectory of the other joint to the feedforward control input.

In addition, another effect of the present invention is that it is possible to reduce the load while implementing control accuracy of the parallel robot control system by using the dependent control method without using the independent control method.

1 is a circuit block diagram showing the configuration of a general parallel robot control system.
2 is a diagram illustrating a feedback configuration between the motion control unit 150 and the parallel robot 190 according to an embodiment of the present invention.
3 is a parallel robot control block diagram according to an embodiment of the present invention.
4 is a flowchart illustrating a process of controlling a parallel robot according to an embodiment of the present invention.

As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, .

On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "having" are intended to indicate that there is a feature, number, process, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present disclosure does not exclude the possibility of the presence or the addition of numbers, processes, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, a parallel robot control system and method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a circuit block diagram showing the configuration of a parallel robot control apparatus according to an embodiment of the present invention. Referring to FIG. 1, the parallel robot control apparatus includes an image capturing unit 160 for capturing image information of a target object 10, an image information processor 130 for processing the captured image as image information, and Acquire the current target object information on the target object 10 from the image information, compare the current target object information with the obtained current parallel robot information of the parallel robot 190, calculate the tracking error and the synchronization error, and then calculate the parallel type. A central processing unit (CPU) 110 for generating overall control input information for moving the robot 190, and a motion controller 150 for moving the parallel robot 190 according to the generated total control input information. do.

The dual CPU 110, the image information processor 130, and the motion controller 150 constitute a central controller 100 block. The central control unit 100 includes a computer system composed of a computer and a Motion Engineering, Inc. (MEI) motion board. This computer system is based on the Windows, UNIX, and Linux operating systems (OS), and the CPU 110 and the motion controller 150 control the arms of the parallel robot 190. In order to secure the real-time, the operation is performed based on the Real Time Extension (RTX) and then the motion control command is given to the MEI motion board. These components will be described as follows.

The CPU 110 processes the user's input information, that is, when the user moves the target object 10 to another place, the CPU 110 commands the parallel robot 190. Of course, for this purpose, the user input processing unit 110 provides a user with a graphical user interface (GUI).

In addition, the tracking error and the synchronization error is calculated, the total error is calculated using the tracking error and the synchronization error, and the total control input information for changing the position of the parallel robot 190 is generated using the overall error. . Of course, the CPU 110 requires image information on the position and shape of the target object 10. To this end, the image information processor 130 and the image capturing unit 160 are provided.

The image capturing unit 160 photographs the target object 10 and transmits the photographing information to the image information processing unit 130.

The image information processor 130 generates image information by receiving and processing photographing information captured by the image capturing unit 160. In other words, the current object information about the object 10 is generated. The current object information includes position coordinates, angles, and shape information of the object 10.

This is because it is possible to calculate the displacement of each joint 193a to 193n of the parallel robot 190 only when the shape, position, angle, and the like of the object 10 are known.

The communication between the image information processor 130 and the CPU 110 uses various communication protocols such as Ethernet, a controller area network (CAN), RS232, and a digital input-output (DIO) scheme.

Of course, in FIG. 1, the image capturing unit 160 and the image information processing unit 130 are separately illustrated. However, the image capturing unit 160 and the image information processing unit 130 are not limited thereto. It is also possible to substitute an integrated camera capable of image processing.

(여기서, i=1,2,…,n)으로 표현되고, i번째 관절부의 각의 목표 궤적(즉, 기준 궤적(reference trajectory)으로 일컬어짐)은

으로 표현된다. In addition, the CPU 110 solves the target values x _d , y _d , and z _d input by the GUI (not shown) by inverse kinematics, and converts the target values x _d , y _d , and z _d into target values of the respective joint portions 193a to 193n. . That is, assuming that the total number of joint parts 193a to 193n is n, the angle of the i-th joint part is

(Where i = 1, 2, ..., n), and the target trajectory of the angle of the i-th joint (ie, referred to as a reference trajectory) is

.

Therefore, it is possible to acquire and express the current target object information of the target object 10 and the position information of the current parallel robot information with respect to the parallel robot 190 in advance. Of course, the current position information of the parallel robot may include a unique identification ID of the parallel robot 190 and the like.

The motion controller 150 performs a function of controlling the driving of the motor drivers 170a to 170n to control the motion of the parallel robot 190.

In order to stably perform the motion control of the parallel robot 190, the control protocol between the motion controller 150 and the parallel robot 190 uses a SynqNet protocol that exhibits robustness to noise. Therefore, the motion controller 150 may use SynqNet-based motion engineering, Inc. (MEI) motion control apparatus.

The parallel robot 190 includes a motor driver 170a to 170n connected to the motion control unit 150, shaft motors 191a to 191n driven by the motor driver 170a to 170n, and the shaft motors 191a to 191n. Joint portions 193a to 193n and the like which are operated by a mechanical mechanism.

In other words, the first motor driver 170a, the first shaft motor 191a, and the first joint part 193a are connected to each other, and the second motor driver 107b, the second shaft motor 191b, and the second joint part 193b are connected to each other. ) Is connected. In addition, the encoders 195a to 195n are integrally formed in each of the shaft motors 191a to 191n, and the rotational amounts of the shaft motors 191a to 191n are converted into digital signals and fed back to the motion controller 150. . Therefore, calculation of the positional information (that is, the movement amount) of each of the joint parts 191a to 191n can be performed.

In addition, the central control unit 100 includes a memory unit (not shown), a display unit (not shown), an input unit (not shown), and the like, which store data, programs, and software.

The memory unit may be a memory provided in the CPU 110 or may be a separate memory. Therefore, nonvolatile devices such as hard disk drives, flash memory, electrically erasable programmable read-only memory (EEPROM), static RAM (SRAM), ferro-electric RAM (FRAM), phase-change RAM (PRAM), magnetic RAM (MRAM), and so on. Memory and / or volatile memory such as random access memory (RAM), dynamic random access memory (DRAM), or the like may be used.

The display unit may be a liquid crystal display (LCD), an organic light emitting diode (OLED), a crystal ray tube (CRT), or the like. Therefore, it is possible to provide a GUI screen to a user through such a display part. Therefore, the user can adjust the parallel robot (190 in FIG. 1) using this display portion.

The input unit is an input means used by the user to operate the parallel robot (190 in FIG. 1), and may be a mouse, a keyboard, a voice input, or the like. Of course, in the case of voice input, a program for recognizing a user's voice is installed. Since the voice recognition program is widely known, a description thereof will be omitted.

2 is a diagram illustrating a feedback configuration between the motion control unit 150 and the parallel robot 190 according to an embodiment of the present invention. Referring to FIG. 3, the motion controller 150 moves the joints 193a to 193n of FIG. 1 through the motor driving units 170a to 170n of FIG. 1.

After the joints 193a to 193n move, it is confirmed whether the parallel robot 190 is exactly at the position of the target object 10. At this time, the position information of the parallel robot 190 described above is a motion controller. Feedback to 150. Of course, this feedback information may be transmitted to the CPU (110 of FIG. 1).

3 is a parallel robot control block diagram according to an embodiment of the present invention. Referring to FIG. 3, the parallel robot control block diagram includes an error calculator 200 that calculates a tracking error and a synchronization error, and an overall error generator 210 that calculates an overall error using the calculated tracking error and a synchronization error. PID (Proportional-Integral-Derivative) controller 220 for generating feedback control information using the overall error, by using the sum of the target trajectory reflected by the constant parameter (αi) to adjust the reflection rate by adjusting the feed forward control information A feed forward controller 270 to generate, a total control input information generation unit 230 for generating total control input information by combining the feedback control information and the feed forward control information, and a filter unit 240 for removing noise from the total control input information. ), The parallel robot 190 operated by the total control input information from which the noise is removed, and the angles of the joints (193a to 193n in FIG. 1) of the parallel robot 190. It is composed of an encoder 195, such as feedback to process the location information.

Referring to FIG. 3, when the parallel robot 190 operates, the respective position information of the joints 193a to 193n is calculated by the amount of rotation of the shaft motors 191a to 191n, which is a parallel robot 190. This is the current location information of. The current position information is transmitted to the error calculator 200 through the feedback line 300 by the encoder 195. That is, it is represented by q ₁ , q ₂ , q ₃ . In other words, the information values 203 of the joint portions (193a to 193n in FIG. 1) are obtained.

으로 표현된다. Of course, a target trajectory value 201 for the angles of the joints 193a to 193n is also input to the error calculator 200. At this time, the target trajectory value 201 is

.

The tracking error is calculated using the target trajectory value 201 and each information value 203 as follows.

Generalizing the equation 1 to be applied to a parallel robot having n joints, the equation 1 is expressed as follows.

는 i번째 관절부의 각의 목표 궤적을,

는 i번째 관절부의 각을 나타낸다.
here,

Is the target trajectory of the angle of the i-th joint,

Represents the angle of the i-th joint part.

The synchronization error is calculated using the following tracking error as follows.

In other words, the synchronization error ε ₁ of the first joint 193a of FIG. 1 is defined as a difference value between the first tracking error and the second and third tracking errors, and the second second joint part (of FIG. 1). The synchronization error ε ₂ of 193b) is defined as the sum of the second tracking error and the first tracking error, the second tracking error, and the third tracking error.

Generalizing the equation 1 to be applied to a parallel robot having n joints, the equation 1 is expressed as follows.

In other words, there is a difference between the i th tracking error, the previous (i-1) th tracking error and the next (i + 1) th tracking error value.

The total error generation unit 210 calculates the total error using the tracking error and the synchronization error generated by Equation 1 and Equation 2, and the calculation method is as follows.

는 추종 오차이고,

는 동기화 오차를 나타내며,

는 동기화 오차의 반영비율을 조정하는 상수 파라미터를 나타낸다.here,

Is the tracking error,

Represents a synchronization error,

Denotes a constant parameter that adjusts the reflectance ratio of the synchronization error.

) 및 동기화 오차(

)를 반영한 전체 오차가 된다. 따라서, PID 제어기(220)에 의해 피드백 제어 정보(

)가 생성된다.PID controller 220 is to calculate the position error, velocity error, and the integral value of the position error, as is well known, in the present invention, the error is a tracking error (

) And sync error (

) Is the total error reflected. Therefore, the feedback control information (the PID controller 220)

) Is generated.

)가 생성된다. The feed forward controller 270 is composed of a sum of target trajectories for each joint part (193a to 193n in FIG. 1), and the reflectance ratio is adjusted using a constant parameter α _i . The constant parameter α _i may be calculated in advance by an experimental value and stored in a memory included in the central controller 100 of FIG. 1. Therefore, the feed forward control information (by adjusting the reflecting ratio by the feed forward controller 270) (

) Is generated.

) 및 피드 포워드 제어기(270)에 의해 생성된 피드 포워드 제어 정보(

)을 합하여 전체 제어 입력 정보를 생성한다. 이러한 전체 제어 입력 정보를 표현하면 다음식과 같다. The overall control input information generator 230 may include feedback control information generated by the PID controller 220 (

) And feed forward control information generated by the feed forward controller 270 (

) To generate full control input information. The overall control input information is expressed as follows.

Here, K _p , K _i , K _d represent gain or gain values as control parameters.

These gain values are calculated by tuning, which is the process of calculating them by mathematical or experimental / empirical methods. There are several ways to tune this, the most widely known being Ziegler-Nichols and relay tuning.

The filter unit 240 may remove noise when the entire control input information generated by the entire control input information generator 230 is input to the parallel robot 190.

4 is a flowchart illustrating a process of controlling a parallel robot according to an embodiment of the present invention. Referring to FIG. 4, as the user controls the operation of the parallel robot (190 of FIG. 1), target trajectory information of each joint part 193a to 193n is input (step S400). In other words, the target trajectory information is generated when the user causes the parallel robot 190 to grip the target object (10 of FIG. 1) by using an input unit (not shown) connected to the central control unit (100 of FIG. 1). .

At the same time, the encoder 195 of FIG. 1 feeds back current position information of each joint 193a to 193n according to the operation of each joint 193a to 193n to the motion control unit 150 of FIG. 1 (step S420). Of course, this feedback process may be performed before the target trajectory information is input or may be performed after the target trajectory information is input.

When the target trajectory information and the feedback are made, the central processing unit (CPU) 110 compares the target trajectory information with the current position information and calculates a tracking error e _i of each joint 193a to 193n (step S430). .

When the tracking error is calculated, the synchronization error is obtained using the following error of the i-th joint part, the following (i-1) and following (i + 1) joint parts of the following errors of the respective joint parts 193a to 193n. (ε _i ) is calculated (step S440).

)를 생성한다(단계 S450).When the tracking error e _i and the synchronization error ε _i are calculated, a Proportional-Integral-Derivative (PID) controller 220 of FIG. 3 uses this tracking error e _i and the synchronization error ε _i . By calculating the overall error (e _coupled ), the feedback control information (

) Is generated (step S450).

)를 생성한다(단계 S460).In addition, the feed forward controller 270 of FIG. 3 uses the sum of the target trajectories of the joints 193a to 193n and adjusts the reflectance ratio of each joint 193a to 193n with a constant parameter α _i to feed the feed. Forward control information (

) Is generated (step S460).

) 및 피드 포워드 제어 정보(

)를 이용하여 전체 제어 입력 정보를 계산한다(단계 S470). The overall control input information generator 230 may include feedback control information (

) And feedforward control information (

) To calculate the total control input information (step S470).

The motion control unit 150 of FIG. 1 drives each of the joints 193a to 193n of FIG. 1 by driving the motor driving unit according to the entire control input information (steps S480 and S490).

10: object
100: central control unit 110: CPU (Central Processing Unit)
130: image information processing unit 150: motion control unit
160: image capturing unit 170a to 170n: motor driving unit
190: parallel robot
191a to 191n: drive motor
193a to 193n: joint portion
195a to 195n: encoder
200: error calculation unit 201: target trajectory value
203: angle value of the joint part 210: total error generating unit
220: PID controller 230: full control input information generation unit
240: filter unit 270: feed forward controller
300: feedback line

Claims (7)

A target trajectory information input step of inputting target trajectory information of each joint unit as the user controls the operation of the parallel robot;
A feedback step of an encoder feeding back the current position information of each joint part to the motion controller according to the motion of each joint part;
A tracking error calculating step of calculating, by a central processing unit, a tracking error of each joint part by comparing the target trajectory information with current position information;
A synchronization error calculating step of calculating a synchronization error using a tracking error of an i-th joint part and a tracking error of a previous and next joint part of the i-joint part among the tracking errors of each joint part;
A feedback control information calculation step of generating a feedback control information by a PID (Proportional-Integral-Derivative) controller calculating a total error using the tracking error and the synchronization error;
A feed forward control information calculating step of generating, by a feed forward controller, feed forward control information by using a sum of the target trajectories of the respective joint portions and adjusting a reflection ratio of each joint portion with a constant parameter;
A total control input information calculating step of generating, by the total control input information generating unit, a total control input using the sum of the feedback control information and the feed forward control information; And
Joint unit driving step of driving each joint part by driving a motor drive unit according to the overall control input information by the motion control unit
Control method of a high speed parallel robot based on a synchronization method of a plurality of axes comprising a.
The method of claim 1,
The current position information of each joint part follows the target trajectory information of each joint part.
3. The method according to claim 1 or 2,
The following error (

)

(here,

Is a tracking error,

Is the target trajectory of the angle of the i-th joint, and

Is the angle of the i-th joint)
A control method of a high speed parallel robot based on a synchronization method of a plurality of axes, characterized in that defined as.
The method of claim 1,
The synchronization error (

)

(here,

Is a synchronization error,

Is a tracking error)
A control method of a high speed parallel robot based on a synchronization method of a plurality of axes, characterized in that defined as.
The method of claim 1,
The overall error (

)

(here,

Is the overall error,

Is a tracking error,

Is the synchronization error and

Is a constant parameter that adjusts the reflection rate of the synchronization error.
A control method of a high speed parallel robot based on a synchronization method of a plurality of axes, characterized in that defined as.
The method of claim 1,
The entire control input (

)silver

(here,

Is the total control input,

Feedback control information (

)

Feed forward control information (

),
K _p , K _d and K _i are control parameters, respectively, position error gain value, speed error gain value, position error integral gain value,

Is the derivative of e,

Is the overall error,

Is a constant parameter and

Is the target trajectory of the angle of the nth joint part)
A control method of a high speed parallel robot based on a synchronization method of a plurality of axes, characterized in that defined as.
3. The method according to claim 1 or 2,
The driving of the joint part may further include removing a noise from the overall control input information by a filter unit.

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