Joint vibration suppression method, device and equipment of collaborative robot and storage medium

Abstract

The invention discloses a joint vibration suppression method, device and equipment of a collaborative robot and a storage medium. The method comprises the steps that according to position information of a motor end encoder and position information of a harmonic reducer end encoder, an observation speed and speed observation delay containing vibration information are obtained; subtracting the observation speed from the given speed to obtain a speed deviation; obtaining a group of control parameters of the current working condition according to the load inertia and the tail end speed of the robot through an automatic variable gain strategy; performing speed loop PID control according to the speed deviation and the control parameters to obtain a control torque; load disturbance observation is carried out according to feedback information of the torque sensor and the observation speed, and harmonic reducer end disturbance torque is obtained; and adding the disturbance torque to the control torque to obtain the given torque of the torque ring. According to the invention, the speed loop feedback channel contains information which directly reflects the vibration of the robot, and the method can adapt to vibration suppression of various models in different postures.

Description

Technical Field

[0001] The invention belongs to the field of motor control, and in particular relates to a method for suppressing joint vibration of a collaborative robot. Background Art

[0002] With the development and popularization of robot technology, collaborative robots are being widely used in various fields such as industry, scientific research, education, and consumption. Unlike industrial robots, in order to achieve high torque density, harmonic reducers are usually used in collaborative robots. The unique vibration of the flexible wheel and steel wheel of the harmonic reducer is introduced into the joint, making the joint a second-order elastic oscillation system. The mutual influence between the joints further aggravates the vibration of the robot body.

[0003] In the prior art, there are three main methods to reduce this natural vibration: One is to reduce the bandwidth of the joint velocity loop so that the system does not respond to the vibration of the second-order elastic system. This method reduces vibration by sacrificing the system stiffness performance. In essence, it does not achieve vibration suppression, but only does not aggravate vibration.

[0004] The second method is to use a torque notch filter. This method is similar to method 1, filtering out the part of the servo controller output torque that has the same frequency as the second-order system. However, since the natural frequency of the harmonic reducer is very low, adding a notch filter will also lead to a decrease in the system stiffness performance.

[0005] The third method is to use the speed loop to change the PI parameters. This method uses segmented discontinuous PI parameters, which is extremely dependent on the on-site experience of engineers and requires one machine to be adjusted, making it difficult to achieve automatic parameter adjustment.

[0006] At the same time, the existing methods are difficult to adapt to the vibration suppression of the same robot in different postures. In addition, since the joint speed loop feedback in the existing technology uses the motor end encoder information, and the robot vibration occurs at the harmonic reducer end, the control effect is very limited. Summary of the invention

[0007] In order to overcome the shortcomings of the prior art in the joint vibration suppression effect of the collaborative robot, the embodiment of the present application first provides a joint vibration suppression method for a collaborative robot, which is characterized by comprising the following steps: The motor end speed and the harmonic reducer end speed are obtained according to the motor end encoder position information and the harmonic reducer end encoder position information, and the speed adaptive hybrid observation is performed according to the motor end speed and the harmonic reducer end speed to obtain the observation speed and speed observation delay containing vibration information; Subtract the observed speed from the given speed to obtain a speed deviation; The robot load inertia and terminal speed are automatically variable gain strategy to obtain a set of control parameters for the current working condition; Perform speed loop PID control according to the speed deviation and the control parameter to obtain a control torque; Perform load disturbance observation according to the feedback information of the torque sensor and the observed speed to obtain the disturbance torque at the harmonic reducer end; The control torque is added to the disturbance torque to obtain the torque setting of the torque loop.

[0008] In order to achieve the above-mentioned purpose of the invention, the embodiment of the present application further provides a joint vibration suppression device for a collaborative robot, which is characterized by comprising: A speed feedback adaptive observer is used to obtain the motor end speed and the harmonic reducer end speed according to the motor end encoder position information and the harmonic reducer end encoder position information, and to perform speed adaptive mixed observation according to the motor end speed and the harmonic reducer end speed to obtain the observation speed and speed observation delay containing vibration information; A subtractor, used for subtracting the observed speed from the given speed to obtain a speed deviation; The automatic variable gain module is used to obtain a set of control parameters for the current working condition by using the automatic variable gain strategy to change the robot load inertia and terminal speed; A speed loop PID controller, used for performing speed loop PID control according to the speed deviation and the control parameter to obtain a control torque; A load disturbance observer, used to observe the load disturbance according to the feedback information of the torque sensor and the observed speed, and obtain the disturbance torque at the harmonic reducer end; The adder is used to add the control torque to the disturbance torque to obtain the torque setting of the torque loop.

[0009] To achieve the above-mentioned purpose of the invention, an embodiment of the present application also provides an electronic device, including a processor and a memory, wherein the memory stores a program that can be run on the processor, and is characterized in that when the program is executed by the processor, the steps of the above-mentioned collaborative robot joint vibration suppression method are implemented.

[0010] Also, a computer-readable storage medium is provided, storing at least one program, characterized in that the at least one program can be executed by at least one processor to implement the steps of the above-mentioned method for suppressing joint vibration of a collaborative robot.

[0011] The present invention has the following beneficial effects: 1. Design a speed adaptive hybrid observation link, introduce the encoder position information at the motor end and the encoder position information at the harmonic reducer end, so that the speed loop feedback channel contains information that directly reflects the robot vibration; 2. Introduce the inertia of the end of the collaborative robot relative to each joint in different postures to compensate for the reduction of system stiffness caused by vibration suppression; 3. Introduce the feedback information of the torque sensor at the end of the joint and design the load disturbance observation link to truly compensate for the vibration caused by the joint load disturbance; 4. Speed ​​loop PID control should correct and offset the harmonic reducer object characteristics as much as possible; 5. Based on the load inertia and terminal speed under different postures of the collaborative robot, a nonlinear automatic variable gain strategy for the speed loop is designed so that a set of parameter configurations can be adapted to vibration suppression in a variety of models and their different postures. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The flowchart of the joint vibration suppression method of the collaborative robot; Figure 2 This is the overall block diagram of the joint vibration suppression device of the collaborative robot; Figure 3 It is the block diagram of the speed feedback adaptive observer; Figure 4 Schematic diagram of the velocity adaptive hybrid observation method; Figure 5 is the block diagram of the load disturbance observer; Figure 6 is the Bode plot of the load disturbance observer; Figure 7 It is a schematic diagram of the automatic variable gain strategy; Figure 8 This is a schematic diagram of extremely low speed time-varying gain; Fig. 9 This is the speed loop control block diagram; Fig.10 This is a structural block diagram of an electronic device. DETAILED DESCRIPTION

[0013] In order to make the technical solution of the present invention more clearly understood, the technical solution of the present invention is further described in detail below according to specific embodiments and in combination with the accompanying drawings. Obviously, the following embodiments are only part of the embodiments of the present invention and do not constitute a limitation on the technical solution of the present invention. For those of ordinary skill in the art, other embodiments can also be obtained according to the embodiments of the present application without paying creative labor.

[0014] It should be noted that the order of steps described in the method embodiments in the following embodiments does not constitute a limitation on the technical solution of the present invention. For ordinary technicians in this field, without paying any creative labor, they can also reasonably adjust the order of certain steps according to the embodiments of the present application.

[0015] Embodiment 1: This embodiment provides a method for suppressing joint vibration of a collaborative robot. Figure 1 As shown, the following steps are included: Step S101, obtain the motor end speed according to the motor end encoder position information, obtain the harmonic reducer end speed according to the motor end encoder position information, perform speed adaptive mixed observation according to the motor end speed and the harmonic reducer end speed, and obtain an observation speed containing robot vibration information.

[0016] Specifically, Figure 3 As shown, the encoder position information at the motor end and the encoder position information at the harmonic reducer end are respectively input into their respective speed calculation functions, and the motor end speed and the harmonic reducer end speed are calculated. These two speeds are mixed observed by the speed adaptive hybrid observation unit to obtain the observed speed and speed observation delay containing vibration information for the feedback channel of the speed loop PID controller.

[0017] The specific speed adaptive hybrid observation method is as follows: Figure 4 As shown: When the observed speed is zero, the observed speed is equal to the motor end speed, and the speed observation delay is equal to the motor end speed observation delay; When the observed speed is greater than the low speed threshold, the observed speed is equal to the harmonic reducer end speed, and the speed observation delay is equal to the harmonic reducer end speed observation delay; When the observed speed is between zero speed and low speed threshold, observed speed = K1*motor end speed + (1-K1)*harmonic reducer end speed; speed observation delay = K1*motor end speed observation delay + (1-K1)*harmonic reducer end speed observation delay, where K1 is a linear coefficient.

[0018] Step S102: subtract the observed speed from the given speed to obtain the speed deviation.

[0019] The above speed setting is calculated by the position loop.

[0020] Step S103: The robot load inertia and terminal speed are automatically varied by a gain strategy to obtain a set of control parameters for the current working condition.

[0021] Among them, the load inertia and terminal speed of the above-mentioned robot are calculated by the host computer.

[0022] Figure 7Schematic diagram of automatic variable gain strategy. Since the vibration characteristics of the robot are different under different loads and postures, the load inertia ratio is used as the independent variable in the automatic variable gain strategy of this embodiment, and the intermediate frequency width of the speed loop is changed. The overall strategy is that the larger the load inertia ratio, the larger the intermediate frequency width, that is, the larger the phase margin, the stronger the stability, but the lower the stiffness. Although the stiffness is reduced, stiffness compensation can be performed because it is at a larger load inertia ratio at this time.

[0023] Usually in the speed loop correction method, the intermediate frequency width H is generally set to 4 or 5. In this embodiment, the intermediate frequency width of the speed loop adopts a nonlinear change: ,

[0024] Among them, H is the intermediate frequency width of the speed loop, Kj represents the load inertia ratio, Kj=J2 / J1, J1 represents the motor rotation inertia, J2 represents the load inertia, a is a gain change curve base value, generally ranging from 2 to 8, and 2 is taken in this embodiment. H0 is the basic intermediate frequency width, generally ranging from 4 to 24, and 8 is taken in this embodiment. Kn is the gain coefficient at extremely low speed (i.e., the robot end speed is less than 1% of the rated speed of the motor), such as Figure 8 , further reducing the intermediate frequency width at extremely low speeds, improving system stiffness and dynamic tracking accuracy. When the terminal speed is greater than the low-speed threshold, the intermediate frequency width is adjusted only according to the load inertia. When it is lower than the low-speed threshold, the intermediate frequency width is further reduced based on the base value after load inertia adjustment, and can be reduced to half at zero speed.

[0025] Step S104: Perform speed loop PID control according to the above speed deviation and control parameters to calculate the current control torque.

[0026] like Fig. 9 The speed loop PID control block diagram of this embodiment is shown in FIG. The speed loop PID controller transfer function is: ,

[0027] Assume that the speed calculation feedback delay time is , the equivalent delay time of the reducer is , first make , and then the speed loop open-loop transfer function is: ,

[0028] Take the intermediate frequency width H, we have The intermediate frequency width changes nonlinearly in real time according to the load inertia and terminal speed. At this time, the controller open-loop transfer function is: ,

[0029] According to the engineering optimal design principle of minimizing the resonance peak, we get ,

[0030] That is, the open-loop gain of the system increases as the load inertia sent by the host computer increases. From then on, all control parameters are calibrated.

[0031] Step S105: Observe the load disturbance according to the feedback information of the torque sensor and the observed speed to obtain the disturbance torque at the harmonic reducer end.

[0032] Specifically, based on the fact that the harmonic reducer motor end rotates one tooth every time the harmonic reducer motor end rotates one circle, the disturbance torque experiences two peaks and two troughs, that is, the frequency of the disturbance torque is twice the mechanical frequency of the motor shaft end. In this embodiment, a second-order notch filter is designed, such as Figure 5 As shown, the notch frequency is equal to twice the mechanical frequency of the motor shaft end. The disturbance torque at the harmonic reducer end is obtained by subtracting the output signal of the second-order notch filter from the source signal (i.e. the torque sensor feedback information signal).

[0033] The second-order notch filter transfer function of this embodiment is: ,

[0034] Among them, s is a complex variable, To set the center frequency of the notch, the bandwidth of the notch filter , which is the frequency band range of -3dB from left to right of the center frequency, ; Notch depth For example, when the center frequency is 100ras / s, =10%, =10, attenuation coefficient A=0.1, DP=-20dB, its Bode plot is as follows Figure 6 shown.

[0035] Step S106: Add the control torque to the disturbance torque to obtain the torque setting of the torque loop.

[0036] Embodiment 2: This embodiment provides a joint vibration suppression device for a collaborative robot for implementing the method of embodiment 1, such as Figure 2 As shown, including: The speed feedback adaptive observer is used to obtain the motor end speed and the harmonic reducer end speed according to the motor end encoder position information and the harmonic reducer end encoder position information respectively, and to perform speed adaptive mixed observation according to the motor end speed and the harmonic reducer end speed to obtain the observed speed containing vibration information.

[0037] like Figure 3As shown, the encoder position information at the motor end and the encoder position information at the harmonic reducer end are respectively input into their respective speed calculation functions to calculate the motor end speed and the harmonic reducer end speed. These two speeds are mixed and observed by the speed adaptive hybrid observation unit to obtain the observed speed and speed observation delay containing vibration information for the feedback channel of the speed loop PID controller. The specific speed adaptive hybrid observation method of the speed adaptive hybrid observation unit is as follows: Figure 4 shown.

[0038] The subtractor is used to subtract the observed speed from the given speed to obtain the speed deviation.

[0039] The automatic variable gain module is used to obtain a set of control parameters for the current working conditions by using the automatic variable gain strategy to change the robot load inertia and terminal speed.

[0040] The automatic variable gain module adopts the following automatic variable gain strategy: the load inertia ratio is used as the independent variable, and the intermediate frequency width of the speed loop is changed. The overall strategy is that the larger the load inertia ratio, the larger the intermediate frequency width. In this embodiment, the intermediate frequency width of the speed loop adopts nonlinear change: ,

[0041] Among them, H is the intermediate frequency width of the speed loop, Kj represents the load inertia ratio, Kj=J2 / J1, J1 represents the motor rotation inertia, J2 represents the load inertia, a is a base value of the gain change curve, H0 is the basic intermediate frequency width, and Kn is the gain coefficient at extremely low speed (that is, the robot end speed is less than 1% of the rated speed of the motor).

[0042] The speed loop PID controller is used to perform speed loop PID control according to the speed deviation and control parameters to obtain the control torque.

[0043] The load disturbance observer is used to observe the load disturbance according to the feedback information of the torque sensor and the observed speed, and obtain the disturbance torque at the harmonic reducer end.

[0044] This embodiment designs a second-order notch filter, such as Figure 5 As shown, the notch frequency is equal to twice the mechanical frequency of the motor shaft end. The disturbance torque at the harmonic reducer end is obtained by subtracting the output signal of the second-order notch filter from the source signal (i.e. the torque sensor feedback information signal).

[0045] The second-order notch filter transfer function of this embodiment is: ,

[0046] Among them, s is a complex variable, To set the center frequency of the notch, the bandwidth of the notch filter , which is the frequency band range of -3dB from left to right of the center frequency, ; Notch depth .

[0047] The adder is used to add the control torque to the disturbance torque to obtain the torque setting of the torque loop.

[0048] Embodiment three: This embodiment provides an electronic device, such as Fig.10 As shown, it includes a processor 31 and a memory 32 that is in communication with the processor 31. The memory 32 stores a program that can be run on the processor 31, and when the program is executed by the processor 31, the steps of the data comparison method provided in the above embodiment are implemented.

[0049] The above program can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, C++, and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a separate software package, partially on the user's computer and partially on a remote computer, or entirely on the remote computer or server.

[0050] Embodiment 4: This embodiment provides a computer-readable storage medium, which stores at least one program. The at least one program can be executed by at least one processor to implement the steps of the data comparison method provided in the above embodiment.

[0051] The above storage media include: U disk, mobile hard disk, read-only memory, random access memory, disk or optical disk and other media that can store program code and their combination. With the development of science and technology, the meaning of storage media may become more and more extensive and not limited to tangible media.

[0052] Those skilled in the art can understand that the above-mentioned embodiments are specific embodiments for implementing the present invention. In addition to the above-mentioned embodiments, the present invention may also have other implementation modes; any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the protection scope required by the present invention.

Claims

1. A method for suppressing joint vibration of a collaborative robot, characterized in that: The steps include: The motor end speed and the harmonic reducer end speed are obtained according to the motor end encoder position information and the harmonic reducer end encoder position information, and the speed adaptive hybrid observation is performed according to the motor end speed and the harmonic reducer end speed to obtain the observation speed and speed observation delay containing vibration information; Subtract the observed speed from the given speed to obtain a speed deviation; The robot load inertia and terminal speed are automatically variable gain strategy to obtain a set of control parameters for the current working condition; Perform speed loop PID control according to the speed deviation and the control parameter to obtain a control torque; Perform load disturbance observation according to the feedback information of the torque sensor and the observed speed to obtain the disturbance torque at the harmonic reducer end; The control torque is added to the disturbance torque to obtain the torque setting of the torque loop.

2. The method for suppressing joint vibration of a collaborative robot as claimed in claim 1, characterized in that: According to the motor end speed and the harmonic reducer end speed, speed adaptive hybrid observation is performed to obtain the observation speed and speed observation delay containing vibration information, including: When the observed speed is zero, the observed speed is equal to the motor end speed, and the speed observation delay is equal to the motor end speed observation delay; When the observed speed is greater than the low speed threshold, the observed speed is equal to the harmonic reducer end speed, and the speed observation delay is equal to the harmonic reducer end speed observation delay; When the observed speed is between zero speed and low speed threshold, observed speed = K1*motor end speed + (1-K1)*harmonic reducer end speed; speed observation delay = K1*motor end speed observation delay + (1-K1)*harmonic reducer end speed observation delay; K1 is the linear coefficient.

3. The method for suppressing joint vibration of a collaborative robot according to claim 1, characterized in that: The load disturbance observation is performed according to the torque sensor feedback information and the observed speed to obtain the disturbance torque at the harmonic reducer end, including: The torque sensor feedback information signal and the 2-speed signal of the observed speed are input into the first and second order notch filters, and the output signal of the second order notch filter is subtracted from the torque sensor feedback information signal to obtain the harmonic reducer end disturbance torque.

4. The method for suppressing joint vibration of a collaborative robot as claimed in claim 3, characterized in that: The notch frequency of the second-order notch filter is equal to twice the mechanical frequency of the motor shaft end.

5. The method for suppressing joint vibration of a collaborative robot as claimed in claim 3, characterized in that: The transfer function of the second-order notch filter is The expression is as follows: ， Among them, s is a complex variable, To set the center frequency of the notch, the bandwidth of the notch filter ; Notch depth .

6. The method for suppressing joint vibration of a collaborative robot according to claim 1, characterized in that: The automatic variable gain strategy takes the load inertia ratio as an independent variable and nonlinearly changes the intermediate frequency width of the speed loop. The larger the load inertia ratio, the larger the intermediate frequency width.

7. The method for suppressing joint vibration of a collaborative robot as claimed in claim 6, characterized in that: The speed loop intermediate frequency width expression is as follows: ， Wherein, H is the intermediate frequency width of the speed loop, Kj represents the load inertia ratio, Kj=J2 / J1, J1 represents the motor rotation inertia, J2 represents the load inertia, a is the base value of the gain change curve, H0 is the basic intermediate frequency width, and Kn is the gain coefficient when the robot end speed is lower than 1% of the rated speed of the motor.

8. A joint vibration suppression device for a collaborative robot, characterized in that: include: A speed feedback adaptive observer is used to obtain the motor end speed and the harmonic reducer end speed according to the motor end encoder position information and the harmonic reducer end encoder position information, and to perform speed adaptive mixed observation according to the motor end speed and the harmonic reducer end speed to obtain the observation speed and speed observation delay containing vibration information; A subtractor, used for subtracting the observed speed from the given speed to obtain a speed deviation; The automatic variable gain module is used to obtain a set of control parameters for the current working condition by using the automatic variable gain strategy to change the robot load inertia and terminal speed; A speed loop PID controller, used for performing speed loop PID control according to the speed deviation and the control parameter to obtain a control torque; A load disturbance observer, used to observe the load disturbance according to the feedback information of the torque sensor and the observed speed, and obtain the disturbance torque at the harmonic reducer end; The adder is used to add the control torque to the disturbance torque to obtain the torque setting of the torque loop.

9. An electronic device comprising a processor and a memory, wherein the memory stores a program that can be run on the processor, characterized in that: When the program is executed by the processor, the steps of the method for suppressing joint vibration of a collaborative robot described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing at least one program, characterized in that: The at least one program can be executed by at least one processor to implement the steps of the method for suppressing joint vibration of a collaborative robot as described in any one of claims 1 to 7.

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