Robot vibration suppression method based on input shaping technology

Abstract

The invention provides a robot vibration suppression method based on an input shaping technology, and the method comprises the steps: S1, obtaining the last point number in an original trajectory of a robot, and determining the length S (t) in the trajectory direction according to the trajectory of a robot Cartesian space; s2, adding 2T points on the basis of the original trajectory of the robot, and shaping the S (t) by adopting a ZVD input shaping mode to obtain SIS (t); s3, acquiring an issuing value [x (s), y (s), z (s)] of the next track point of the robot according to the SIS (t); and S4, calculating a motion instruction of each joint through inverse kinematics according to the issuing value of the track point. In order to eliminate errors caused by inarrival of point-to-point motion due to shaping time delay, the invention provides input shaping for increasing the number of points of delay time; in order to ensure the motion trail in the Cartesian space, a shaping method along the trail direction in the Cartesian space is adopted. The technology does not depend on feedback control of the system, so that the method has high robustness and application flexibility; and an unreached bit error caused by algorithm delay can be eliminated.

Description

Technical Field

[0001] The invention relates to the technical field of robot vibration suppression, and in particular to a robot vibration suppression method based on input shaping technology. Background Art

[0002] In the field of modern industrial automation and robotics, precise motion control is essential to improve system performance and reliability. Large-load robots, especially industrial robots, often encounter vibration problems when performing high-precision tasks. These vibrations not only affect the accuracy and efficiency of the robot, but may also cause accelerated wear of mechanical parts and even cause safety issues; therefore, vibration suppression (vibration suppression) is a very important part of robot design and application.

[0003] The vibration suppression methods used by existing robots include: using damping materials to absorb vibration energy, such as rubber, viscous fluid or metal alloys. However, although damping materials can effectively absorb part of the vibration energy, they have limited suppression effects on high-frequency or strong vibrations, and some types of damping materials (such as rubber pads) may take up more space, affecting the use of robots. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention aims to provide a robot vibration suppression method based on input shaping technology, which can solve the existing problems.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] The present invention is implemented by the following technical solution: a robot vibration suppression method based on input shaping technology, comprising the following steps:

[0007] S1. Get the last point in the original trajectory of the robot, and determine the length S(t) along the trajectory according to the trajectory of the robot in Cartesian space;

[0008] S2. Add 2T points to the original trajectory of the robot and use ZVD input shaping to shape S(t) to obtain S IS (t);

[0009] S3. According to S IS (t) Obtain the value of the robot's next trajectory point [x(s), y(s), z(s)];

[0010] S4. Calculate the motion instructions of each joint through inverse kinematics according to the sent values ​​of the trajectory points.

[0011] Furthermore, the determining of the length S(t) along the trajectory direction according to the trajectory of the robot in Cartesian space includes presetting the trajectory of the robot in Cartesian space as [x(t), y(t), z(t)], and taking the parameters as: S(t)=sqrt(x t 2 +y t 2 +z t 2 ), where S(t) represents the length along the trajectory direction.

[0012] Furthermore, 2T points are added to the original trajectory of the robot, and S(t) is shaped by ZVD input shaping to obtain S IS (t); including

[0013] 2.1. Obtain the natural frequency and damping coefficient of the robot;

[0014] 2.2. Square the ZVD shaper to obtain the pulse sequence of the shaper; obtain f according to the pulse sequence of the ZVD shaper and the time delay IS (t);

[0015] 2.3. Use ZVD input shaping to reshape S(t) to obtain S IS (t), where: S IS (t) = S (t) * f IS (t).

[0016] Furthermore, the obtaining of the natural frequency and damping coefficient of the robot includes:

[0017] Assume w n is the undamped natural frequency of the system, ξ is the damping ratio of the system, and s is a variable; the transfer function of the system can be expressed as:

[0018]

[0019] Its unit pulse input response is:

[0020]

[0021] where t i is the moment of unit pulse action, is the damped natural frequency of the system;

[0022] From formula (2), we can see that the vibration signal is a decaying sinusoidal signal, and its envelope is:

[0023]

[0024] Then taking the logarithm gives a straight line:

[0025]

[0026] Let M = -ξw n , the damping coefficient can be calculated as:

[0027]

[0028] Further, the ZVD shaper for shaping is squared to obtain a pulse sequence of the shaper; f is obtained according to the pulse sequence of the ZVD shaper and the time delay. IS (t), including:

[0029] The pulse sequence for obtaining the shaper is:

[0030]

[0031] in, The time lags are t 1 =0,t 2 =T,t 3 =2T; the shaper consists of 3 pulses, and the time delay length is one vibration cycle, which is half a vibration cycle longer than the ZV input shaper; thus, f IS (t) = A 1 δ(tt 1 )+A 2 δ(tt 2 )+A 3 δ(tt 3 ).

[0032] Further, according to S IS (t) Obtain the value of the robot's next trajectory point [x(s), y(s), z(s)], including: Where: ΔS is the total length of the displacement trajectory; Δx, Δy, Δz represent the changes in the position of x, y, z in Cartesian space, and the same applies to the posture.

[0033] Furthermore, the algorithm for inverse kinematics calculation includes a Jacobian matrix method or an analytical method.

[0034] A robot vibration suppression device based on input shaping technology comprises a processor and a memory; the memory is used to store a program; the processor executes the program to implement any one of the above methods.

[0035] A computer-readable storage medium, characterized in that: the storage medium stores a program, and the program is executed by a processor to implement any of the above methods.

[0036] Compared with the prior art, the beneficial effects of the present invention include:

[0037] The robot vibration suppression method based on input shaping technology of the present invention first estimates the frequency and damping of the robot system based on the modal parameter identification algorithm of Fourier spectrum analysis and time domain analysis; in order to eliminate the error caused by the point-to-point motion misalignment caused by the shaping time delay, an input shaping method with an increased number of delay time points is proposed; in order to ensure the motion trajectory in Cartesian space, a shaping method along the trajectory direction in Cartesian space is adopted. The technology of the present invention does not rely on the feedback control of the system, so it has high robustness and application flexibility; it can eliminate the misalignment error caused by algorithm delay; it can reduce the residual vibration by 70%, and ensure that the original trajectory in Cartesian space remains unchanged. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The disclosure of the present invention is described with reference to the accompanying drawings. It should be understood that the drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In the drawings, the same reference numerals are used to refer to the same components. Among them:

[0039] Figure 1 A schematic flow chart of a robot vibration suppression method based on input shaping technology according to the present invention;

[0040] Figure 2 A flow chart of an input shaper in an embodiment of the present invention;

[0041] Figure 3 The effect diagram after different pulse treatments in the implementation cases of the present invention;

[0042] Figure 4 It is a trajectory diagram before and after Cartesian space shaping in an implementation case of the present invention;

[0043] Figure 5 It is a curve comparison diagram before and after X-direction shaping in an implementation case of the present invention;

[0044] Figure 6 This is a comparison diagram of acceleration before and after shaping in an implementation case of the present invention;

[0045] Figure 7 It is a spectrum comparison diagram before and after shaping in the implementation case of the present invention. DETAILED DESCRIPTION

[0046] It is easy to understand that according to the technical solution of the present invention, without changing the essential spirit of the present invention, a person skilled in the art can propose a variety of interchangeable structural modes and implementation modes. Therefore, the following specific implementation modes and drawings are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as the whole of the present invention or as a limitation or restriction to the technical solution of the present invention.

[0047] The present invention provides a robot vibration suppression method based on input shaping technology, which mainly includes estimating the natural frequency and damping coefficient of the robot system based on a modal parameter identification algorithm based on Fourier spectrum analysis and time domain analysis; and then shaping the Cartesian space position of the robot arm using a robot position planning jitter suppression algorithm with an increased number of points. Finally, the present invention verifies the method through simulation and experiments.

[0048] The present invention adopts ZVD method to perform input shaping; wherein the input shaping technology is an open-loop control method, which is composed of a series of pulse signals. Vibration is reduced by shaping the input signal. As a feedforward control, the input shaping is designed and solved according to the characteristics of the system to obtain a pulse sequence with different amplitudes and time delays. Then the input signal is convolved with the pulse sequence of the unshaped device to generate a shaped control signal to control the system. The flow chart of the input shaper is shown in FIG. Figure 2 shown.

[0049] The present invention will specifically introduce the robot vibration suppression method of the technology input shaping technology in combination with the embodiment; its process is as follows Figure 1 As shown, the following steps are included:

[0050] S1. Get the last point in the original trajectory of the robot, and determine the length S(t) along the trajectory according to the trajectory of the robot in Cartesian space;

[0051] For example, suppose the original trajectory of the robot consists of a series of points ((x (1) ,y (1) ,z (1) ),(x (2) ,y (2) ,z (2) ),……,(x (n) ,y (n) ,z (n) )), where (n) is the number of points in the original trajectory. Get the coordinates of the last point, i.e. ((x (n) ,y (n) ,z (n) )).

[0052] The robot's trajectory in Cartesian space is preset to [x(t), y(t), z(t)], and the parameters are:

[0053] Where: S(t) represents the length along the trajectory direction.

[0054] S2. Add 2T points to the original trajectory of the robot and use ZVD input shaping to shape S(t) to obtain S IS (t);

[0055] 2.1. Obtain the natural frequency and damping coefficient of the robot;

[0056] Assume w n is the undamped natural frequency of the system, ξ is the damping ratio of the system, and s is a variable; the transfer function of the system can be expressed as:

[0057]

[0058] Its unit pulse input response is:

[0059]

[0060] where t i is the moment of unit pulse action, is the damped natural frequency of the system.

[0061] For example, Figure 3 As shown in the figure, a pulse signal is given to the system at time A1, which will stimulate the vibration response of the system; another pulse signal is given to the system at time A2, which will stimulate another vibration response of the system. The two vibration responses have the same amplitude and opposite direction, and cancel each other out after superposition, thus achieving the effect of eliminating vibration after time A2. Therefore, it is necessary to determine the amplitude and time lag of the input signal to achieve vibration suppression.

[0062] The design of the input shaper requires the pre-acquisition of the natural frequency and damping coefficient of the system, and the effect of the shaper mainly depends on whether the modal parameters of the system can be accurately identified. For the residual vibration of the flexible structure, it can be approximated as a damped simple harmonic vibration. The present invention identifies the vibration frequency based on Fourier analysis, performs fast Fourier transform on the residual vibration signal, and analyzes the spectrum diagram to obtain the main vibration frequency domain of the system. The damping coefficient is calculated by the logarithmic attenuation method. It can be seen from formula (2) that the vibration signal is an attenuated sinusoidal signal, and its envelope is:

[0063]

[0064] Then taking the logarithm gives a straight line:

[0065]

[0066] Let M = -ξw n , the damping coefficient can be calculated as:

[0067]

[0068] 2.2. Square the ZVD shaper to obtain the pulse sequence of the shaper; obtain f according to the pulse sequence of the ZVD shaper and the time delay IS (t).

[0069] The pulse sequence of the shaper is:

[0070]

[0071] in, The time lags are t 1 =0,t 2 =T,t 3 =2T. It can be seen that the shaper consists of 3 pulses, and the time lag length is one vibration cycle, which is half a vibration cycle longer than the ZV input shaper; and then we get; f IS (t) = A 1 δ(tt 1 )+A 2 δ(tt 2 )+A 3 δ(tt 3 );

[0072] 2.3. Use ZVD input shaping to reshape S(t) to obtain S IS (t), where: S IS (t) = S (t) * f IS (t).

[0073] S3. According to S IS (t) Obtain the value of the robot's next trajectory point [x(s), y(s), z(s)]; Where: ΔS is the total length of the displacement trajectory; Δx, Δy, Δz represent the changes in the position of x, y, z in Cartesian space, and the same applies to the posture.

[0074] Exemplarily, the present invention uses a zero vibration derivative shaper (ZVD shaper). When the model parameters are accurate, the ZV shaper can effectively suppress the residual oscillation, but when the model parameters are inaccurate, the zero point of the ZV shaper cannot effectively cancel the zero point of the system, and thus cannot effectively eliminate the residual vibration. In order to improve the robustness of the shaper,

[0075] The present invention adopts ZVD mode to perform input shaping. The ZVD shaper can not only eliminate residual vibration, but also has zero derivative for vibration change, which is equivalent to having two zero points at the vibration frequency.

[0076] In order to ensure that the positioning accuracy between the filtered trajectory and the original design trajectory is the same, since the movement of the robot end is the result of the mutual coupling of six joints, when the trajectory of each joint is shaped separately, the end effector will deviate from the design trajectory. The present invention adopts a shaping method along the trajectory direction and shapes the Cartesian trajectory. After the shaping, the inverse solution is converted to the joint space.

[0077] Assume that the trajectory in Cartesian space is [x(t), y(t), z(t)], and take the parameters as: Where: S(t) represents the length along the trajectory direction. The coordinates of the Cartesian space trajectory can be redefined according to the parameter S(t) as

[0078] [x(s), y(s), z(s)], only S(t) needs to be shaped, and the shaping of the robot wrist translation motion can be realized after the corresponding robot coordinates are calculated. This method actually manifests itself as reconfiguring the speed along the trajectory direction. Theoretically, there is no error after shaping. However, when the original trajectory is actually shaped, there will be a phenomenon of not reaching the position, and the robot arm cannot reach this waypoint. When it reaches the position during actual movement, it will cause jitter. Therefore, it is necessary to increase the number of the last point of the original trajectory by 2T on the basis of the original trajectory. Then shaping it can ensure the position of the motion trajectory.

[0079] S4. Calculate the motion instructions of each joint through inverse kinematics according to the sent values ​​of the trajectory points.

[0080] Exemplarily, it includes: defining the robot model: establishing the dynamic model of the robot, including the link length of each joint, the joint type (rotation or translation), etc.

[0081] Apply inverse kinematics algorithm: For each trajectory point and corresponding posture information, use the inverse kinematics algorithm to calculate the angle or position of each joint. Common inverse kinematics algorithms include Jacobian matrix method, analytical method, etc.

[0082] Get the motion instructions for each joint: get the joint angle or position corresponding to each trajectory point.

[0083] Implementation Cases

[0084] Take the 20KG robotic arm as an example for the experiment; according to step 2.1, the damping coefficient of the 20KG robotic arm is finally calculated to be 0.1 and the natural frequency is 10π.

[0085] Apply input shaping to the robot arm, execute the moveL instruction, and collect data analysis results as follows:

[0086] Figure 4 is the trajectory before and after shaping in Cartesian space, given by Figure 4 It can be obtained that the light grey solid line is the trajectory before shaping, and the black thick line is the trajectory after shaping; the present invention can ensure that the trajectory before and after shaping remains unchanged in the Cartesian space. Figure 5 The curve comparison before and after shaping in the X direction is shown in Figure 5 It can be seen that after shaping, the acceleration of the starting and stopping stages is reduced; the trajectory can ensure that the positions of the starting and stopping points are consistent.

[0087] The conclusion of the test is: the 20KG robotic arm was tested with a load of 10kg and an operating speed of 100%. Figure 6 Comparison of acceleration before and after plastic surgery, where gray is after plastic surgery and black is before plastic surgery; Figure 7 The spectrum comparison before and after shaping. Finally, the method of the present invention is verified under the condition of 20KG robot arm full load. The experimental results show that the residual vibration can be reduced to about 70%, and the original trajectory can be guaranteed not to be deformed.

[0088] High-precision stable control is very important in robot applications. However, when the robot arm is fully loaded, it will inevitably vibrate due to the influence of joint flexibility. In order to achieve high-speed and high-precision point-to-point movement of the robot arm, the present invention designs an input shaper to suppress jitter. The main steps are as follows:

[0089] First, the frequency and damping of the robot system are estimated based on the modal parameter identification algorithm of Fourier spectrum analysis and time domain analysis; in order to eliminate the error caused by the point-to-point motion misalignment caused by the shaping time delay, an input shaping method with an increased number of delay time points is proposed. In order to ensure the motion trajectory in Cartesian space, a shaping method along the trajectory direction in Cartesian space is adopted. The technology of the present invention does not rely on the feedback control of the system, so it has high robustness and application flexibility. It can eliminate the misalignment error caused by algorithm delay; it can reduce the residual vibration by 70%, and ensure that the original trajectory in Cartesian space remains unchanged.

[0090] Input shaping technology is used to suppress the residual vibration of the flexible load end, so as to achieve high-speed and high-precision point-to-point movement. The present invention proposes input shaping technology, which is applicable to the movement in joint space and the movement in Cartesian space. Input shaping technology is a method to reduce or eliminate the vibration of a mechanical system by modifying the input mode of the control signal. The core idea of ​​this technology is to suppress the vibration of the natural frequency of the system when responding to the input instruction by precalculating and adding a specific compensation signal. Input shaping technology does not rely on the feedback control of the system, so it has high robustness and application flexibility.

[0091] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this article.

[0092] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0093] In the several embodiments provided herein, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, or it can be an electrical, mechanical or other form of connection.

[0094] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the embodiments of this article.

[0095] In addition, each functional unit in each embodiment of this invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above integrated unit may be implemented in the form of hardware or in the form of software functional unit.

[0096] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this article is essentially or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of this article. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program code.

[0097] Specific embodiments are used in this article to illustrate the principles and implementation methods of this article. The description of the above embodiments is only used to help understand the methods and core ideas of this article. At the same time, for general technicians in this field, according to the ideas of this article, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on this article.

Claims

1. A robot vibration suppression method based on input shaping technology, characterized in that: The following steps are involved: S1. Get the last point in the original trajectory of the robot, and determine the length S(t) along the trajectory according to the trajectory of the robot in Cartesian space; S2. Add 2T points to the original trajectory of the robot and use ZVD input shaping to shape S(t) to obtain S IS (t); S3. According to S IS (t) Obtain the value of the robot's next trajectory point [x(s), y(s), z(s)]; S4. Calculate the motion instructions of each joint through inverse kinematics according to the sent values ​​of the trajectory points.

2. The robot vibration suppression method based on input shaping technology according to claim 1, characterized in that: Determining the length S(t) along the trajectory direction according to the trajectory of the robot in Cartesian space includes presetting the trajectory of the robot in Cartesian space as [x(t), y(t), z(t)], and taking the parameters as: Where S(t) represents the length along the trajectory direction.

3. The robot vibration suppression method based on input shaping technology according to claim 2, characterized in that: The robot adds 2T points to the original trajectory and uses ZVD input shaping to shape S(t) to obtain S IS (t); include 2.

1. Obtain the natural frequency and damping coefficient of the robot; 2.

2. Square the ZVD shaper to obtain the pulse sequence of the shaper; obtain f according to the pulse sequence of the ZVD shaper and the time delay IS (t); 2.

3. Use ZVD input shaping to reshape S(t) to obtain S IS (t), where: S IS (t) = S(t)*f IS (t).

4. The robot vibration suppression method based on input shaping technology according to claim 3 is characterized in that: The obtaining of the natural frequency and damping coefficient of the robot; include Assume w n is the undamped natural frequency of the system, ξ is the damping ratio of the system, and s is a variable; the transfer function of the system can be expressed as: Its unit pulse input response is: where t i is the moment of unit pulse action, is the damped natural frequency of the system; From formula (2), we can see that the vibration signal is a decaying sinusoidal signal, and its envelope is: Then taking the logarithm gives a straight line: Let M = -ξw n , the damping coefficient can be calculated as:

5. The robot vibration suppression method based on input shaping technology according to claim 3 is characterized in that: The ZVD shaper that performs shaping is squared to obtain a pulse sequence of the shaper; According to the pulse sequence and time delay of the ZVD shaper, f IS (t), including: The pulse sequence for obtaining the shaper is: in, The time delays are t1=0, t2=T, t3=2T respectively; the shaper consists of 3 pulses, and the time delay length is one vibration cycle, which is half a vibration cycle longer than the ZV input shaper; thus, f IS (t)=A1δ(t-t1)+A2δ(t-t2)+A3δ(t-t3).

6. The robot vibration suppression method based on input shaping technology according to claim 3 is characterized in that: According to S IS (t) Obtain the value of the robot's next trajectory point [x(s), y(s), z(s)], including: Where: ΔS is the total length of the displacement trajectory; Δx, Δy, Δz represent the changes in the position of x, y, z in Cartesian space, and the same applies to the posture.

7. The robot vibration suppression method based on input shaping technology according to claim 3 is characterized in that: The algorithm for inverse kinematics calculation includes Jacobian matrix method or analytical method.

8. A robot vibration suppression device based on input shaping technology, characterized in that: It comprises a processor and a memory; the memory is used to store a program; the processor executes the program to implement the method as described in any one of claims 1-7.

9. A computer-readable storage medium, characterized in that: The storage medium stores a program, and the program is executed by a processor to implement the method according to any one of claims 1 to 7.

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