Method for identifying equivalent rotational inertia and friction parameter of robot joint

Abstract

The invention discloses a method for identifying equivalent rotational inertia and friction parameters of robot joints. The method comprises the steps that S1, the robot joints are driven to execute two sections of identification tracks meeting the speed parabolic motion law; s2, collecting joint torque signals of the whole running process of the two sections of tracks; and S3, identifying equivalent rotational inertia and friction force parameters according to a formula. According to the principle of angular momentum conservation, a function relationship among driving motor torque, equivalent rotational inertia and friction force is established, and inertia and friction force parameters are rapidly identified by collecting torque signals when the robot executes a specific track. On one hand, the influence of torque disturbance on an identification result is avoided; and on the other hand, sampling data are fully utilized, so that the identification result is more accurate.

Description

Technical Field

[0001] The present application relates to the technical field related to industrial robots, and in particular to a method for identifying equivalent rotational inertia and friction parameters of robot joints. Background Art

[0002] As far as the inventors know, in the field of industrial robot servo control, a single joint decentralized decoupling control strategy is generally used. Among them, the composite control structure of series PID correction and feedforward correction is the most commonly used control structure. This controller structure has strong robustness and high reliability, and occupies a dominant position in the control process of industrial robots.

[0003] In the single-joint decentralized decoupling control strategy, the performance of the single-joint position control directly affects the overall performance of the robot. Adjusting the controller parameters is an effective means to ensure the performance of the single joint. Establishing the controlled object model and obtaining the model parameters are the premise of the model tuning method. The load moment of inertia, motor rotor inertia and friction are the main parameters in the controlled object model. Therefore, identifying the inertia and friction parameters becomes the key to improving the performance of the robot's single joint. In the robot's joints, the load of the drive motor includes mechanical components, reducers and motor rotors that move with the rotation of the joints. The moment of inertia is the sum of all rotating components. When establishing the controlled object model, the inertia of all rotating components is usually equivalent to the joints to achieve better control effects.

[0004] When considering the influence of friction, the friction model is simplified to a combination of Coulomb friction and viscous friction. In industrial practice, the transfer function of the controlled object is usually simplified to a rational fraction with a numerator of one. Therefore, the process of identifying inertia and friction parameters is also simplified to a polynomial fitting problem. Although there are many solutions to the polynomial fitting problem, the fitting accuracy is related to the identification trajectory. Affected by the order of the polynomial and the sampling data, the noise of the sampling process reduces the identification accuracy. In addition, there are many simple and fast identification methods, all of which are based on the principle of establishing an identification equation group based on the dynamic model of the joint, and completing the identification by solving the solution of the equation group. However, this type of identification method for solving the equation group has a small amount of data and insufficient utilization of the sampling data. Summary of the invention

[0005] The problem to be solved by the present invention is to provide a method for identifying the equivalent moment of inertia and friction parameters of robot joints. According to the principle of conservation of angular momentum, a functional relationship between the torque of the driving motor, the equivalent moment of inertia and the friction force is established. By collecting the torque signal when the robot executes a specific trajectory, the inertia and friction force parameters can be quickly identified. On the one hand, the influence of torque disturbance on the identification result is avoided; on the other hand, the sampling data is fully utilized to make the identification result more accurate.

[0006] In order to solve the above problems, the present invention provides a method for identifying the equivalent moment of inertia and friction parameters of robot joints. In order to achieve the above objectives, the technical solution adopted by the present invention to solve the technical problems is:

[0007] A method for identifying equivalent moment of inertia and friction parameters of robot joints, comprising: step S1: driving the joints of the robot to execute two identification trajectories that satisfy the law of velocity parabola motion; step S2: collecting joint torque signals of the two trajectories during the entire operation; step S3: identifying equivalent moment of inertia and friction parameters according to a formula; wherein the equivalent moment of inertia is represented by I, and the formula for identifying the equivalent moment of inertia is:

[0008]

[0009] The friction parameter is a parameter that describes the magnitude of Coulomb friction and viscous friction in the Coulomb and viscous friction models. The formula of the friction model is:

[0010]

[0011] Among them, τ f represents the friction torque, τ c represents the Coulomb friction constant, B represents the viscous friction coefficient, τ c and B are the parameters to be identified.

[0012] As a further improvement of the present invention, the identification formula of the friction force parameter in step S3 is:

[0013]

[0014] As a further improvement of the present invention, the identification trajectory of step S1 is a data sequence of joint position instructions changing over time.

[0015] As a further improvement of the present invention, step S2 is to collect the torque feedback signal of the driver in the motion controller according to the sampling period.

[0016] As a further improvement of the present invention, the velocity parabola motion law in step S1 is determined by the maximum joint angle θ given in the trajectory. m and the total trajectory running time t m Determine that the function expression formula of the joint position command changing with time is:

[0017]

[0018] The formula for determining a and b is:

[0019]

[0020] As a further improvement of the present invention, the parabolic motion laws of the two-segment trajectory speed are represented by θ1(t) and θ2(t), respectively; the two trajectories are the first and second trajectories with the same maximum joint angle, the total running time of the second trajectory is twice that of the first trajectory, and the maximum joint angle and the total running time of the two trajectories are θ1(t) and θ2(t), respectively. m With t m ,θ m With 2t m ; Executing two trajectories means that the motion controller sends the two trajectories to the motor driver to drive the motor to complete the action.

[0021] As a further improvement of the present invention, the collection result in step S2 is obtained by τ1(kT s ) and τ2(kT s ), where k represents the kth sampling point, T s represents the sampling period, K represents the total number of sampling points; the total number of sampling points is different from the total number of sampling points of the two trajectories, and the acquisition results are represented by K1 and K2 respectively.

[0022] The beneficial technical effects of the method for identifying equivalent rotational inertia and friction parameters of robot joints of the present application are:

[0023] This application discloses a method for identifying equivalent moment of inertia and friction parameters of robot joints. Based on the principle of conservation of angular momentum, a functional relationship between the torque of the driving motor, the equivalent moment of inertia and the friction force is established. By collecting the torque signal when the robot executes a specific trajectory, the inertia and friction force parameters can be quickly identified. On the one hand, the influence of torque disturbance on the identification result is avoided; on the other hand, the sampling data is fully utilized to make the identification result more accurate.

[0024] Firstly, according to the principle of conservation of angular momentum, the identification method of the equivalent inertia and friction parameters of the robot joints was simplified. Secondly, two specific identification trajectories were planned, and a simple and easy-to-solve identification formula was obtained. Finally, the accumulated value of the collected torque signal was used to solve the equivalent inertia parameters and friction parameters, which avoided the influence of torque disturbance on the identification results and improved the identification accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is a schematic diagram of a flow chart of an implementation mode of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with specific embodiments:

[0028] In order to achieve the purpose of the present invention, the present invention proposes a method for identifying equivalent moment of inertia and friction parameters of robot joints. According to the principle of conservation of angular momentum, a functional relationship between the drive motor torque, equivalent moment of inertia and friction force is established, aiming to simplify the process of identifying equivalent moment of inertia and friction parameters of robot joints and improve the identification accuracy. Figure 1 As shown, the present invention mainly includes three steps: first, the joints of the robot are driven to execute two identification trajectories that satisfy the law of velocity parabolic motion; then, the joint torque signals of the entire running of the two trajectories are collected; finally, the equivalent moment of inertia and friction parameters are identified according to the formula.

[0029] To achieve the above object, the present invention adopts the following technical solution:

[0030] A method for identifying equivalent moment of inertia and friction parameters of robot joints, comprising:

[0031] Step S1: drive the robot joints to execute two identified trajectories that satisfy the velocity parabola motion law.

[0032] A trajectory is a data sequence of joint position commands changing over time;

[0033] The law of velocity parabola motion is given by the maximum joint angle θ in the trajectory m and the total trajectory running time t m The function expression of the joint position command changing with time is determined by the following formula:

[0034]

[0035] Where a and b are determined by the following formula:

[0036]

[0037] The two-speed parabolic motion law is to plan two trajectories according to the above formula, which are represented by θ1(t) and θ2(t) respectively.

[0038] The maximum joint angles of the two trajectories are the same, and the total running time of the second trajectory is twice that of the first trajectory. The maximum joint angles and total running time of the two trajectories are θ m With t m ,θ m With 2t m .

[0039] To execute two trajectories, the motion controller sends the above trajectories to the motor driver to drive the motor to complete the action.

[0040] Step S2: collecting joint torque signals of the entire running process of the two trajectories;

[0041] The joint torque signals of the two-segment trajectory are collected by collecting the torque feedback signals of the driver at a specific sampling period in the motion controller. The collection results are given by τ1(kT s ) and τ2(kT s ), where k represents the kth sampling point, T s represents the sampling period, and K represents the total number of sampling points.

[0042] The total number of sampling points, the total number of sampling points of the two trajectories is different, represented by K1 and K2 respectively. s ) where k ranges from 1 to K1; τ2(kT s ) The value range of k is 1 to K2.

[0043] Step S3: Identify the equivalent moment of inertia and friction parameters according to the formula:

[0044] The equivalent moment of inertia, denoted by I, is determined by the following formula:

[0045]

[0046] The friction parameter is a parameter that describes the magnitude of Coulomb friction and viscous friction in the Coulomb and viscous friction models. The friction model is expressed by the following formula:

[0047]

[0048] Among them, τ f represents the friction torque, τ c represents the Coulomb friction constant, and B represents the viscous friction coefficient. τ c and B are the parameters to be identified.

[0049] The formula for identifying the friction parameters is determined by the following formula:

[0050]

[0051] The beneficial effects of adopting the above technical scheme are: first, according to the principle of conservation of angular momentum, the identification method of the equivalent inertia and friction parameters of the robot joint is simplified; second, two specific identification trajectories are planned to obtain a simple and easy-to-solve identification formula; finally, the accumulated value of the collected torque signal is used to solve the equivalent inertia parameters and friction force parameters, avoiding the influence of torque disturbance on the identification results and improving the identification accuracy.

[0052] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for identifying equivalent moment of inertia and friction parameters of robot joints, characterized in that: include: Step S1: driving the joints of the robot to execute two identified trajectories that satisfy the velocity parabola motion law; Step S2: collecting joint torque signals of the entire running process of the two trajectories; Step S3: Identify equivalent moment of inertia and friction parameters according to the formula; Wherein, the equivalent moment of inertia is represented by I, and the formula for identifying the equivalent moment of inertia is: The friction force parameter is a parameter describing the magnitude of the Coulomb friction force and the magnitude of the viscous friction force in the Coulomb and viscous friction model. The formula of the friction force model is: Among them, τ f represents the friction torque, τ c represents the Coulomb friction constant, B represents the viscous friction coefficient, τ c and B are the parameters to be identified.

2. The method for identifying equivalent moment of inertia and friction parameters of robot joints according to claim 1, characterized in that: The identification formula of the friction force parameter in step S3 is:

3. The method for identifying equivalent moment of inertia and friction parameters of robot joints according to claim 1, characterized in that: The identification trajectory of step S1 is a data sequence of joint position instructions changing over time.

4. The method for identifying equivalent moment of inertia and friction parameters of robot joints according to claim 1, characterized in that: The step S2 is to collect the torque feedback signal of the driver in the motion controller according to the sampling period.

5. The method for identifying equivalent moment of inertia and friction parameters of robot joints according to claim 1, characterized in that: The velocity parabola motion law in step S1 is determined by the maximum joint angle θ given in the trajectory. m and the total trajectory running time t m Determine that the function expression formula of the joint position command changing with time is: The formula for determining a and b is:

6. The method for identifying equivalent moment of inertia and friction parameters of robot joints according to claim 5, characterized in that: The parabolic motion laws of the two trajectory velocities are represented by θ1(t) and θ2(t) respectively; The two trajectories are the first and second trajectories with the same maximum joint angles, and the total running time of the second trajectory is twice that of the first trajectory. The maximum joint angles and the total running time of the two trajectories are θ m With t m ,θ m With 2t m ; Executing the two-segment trajectory means that the motion controller sends the two-segment trajectory to the motor driver, and the driving motor completes the action.

7. The method for identifying equivalent moment of inertia and friction parameters of robot joints according to claim 1, characterized in that: The collection result in step S2 is τ1(kT s ) and τ2(kT s ), where k represents the kth sampling point, T s represents the sampling period, K represents the total number of sampling points; The total number of sampling points is different from the total number of sampling points of the two trajectories, and the acquisition results are represented by K1 and K2 respectively.

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