A robot joint module servo controller with digital twin model

Abstract

The present invention belongs to the technical field of robot joint control systems, and specifically relates to a robot joint module servo controller with a digital twin model, including a first digital signal processor and a second digital signal processor, wherein the second digital signal processor is provided with a digital twin model composed of a twin control loop and a motor module model. The present invention utilizes the control and operating state of the original joint module of the digital twin model in the second digital signal processor, and provides the load size calculated by the load observer in the first digital signal processor to the twin model to simulate the real-time operating status of the motor, and finally obtains the early warning information of the motor module, which can monitor the operating status of the joint module in real time, reflect the theoretical characteristics of the joint module in real time, and analyze the early warning information so that the staff can make advance work deployment.

Description

Technical Field

[0001] The present invention belongs to the technical field of robot joint control systems, and in particular relates to a robot joint module servo controller with a digital twin model. Background Art

[0002] The robot arm joint servo module is composed of a servo motor, a reducer and a servo motor driver, and is a mechatronic system. During the operation of the robot arm joint servo module, as the operating years increase or the operating environment changes, the servo module components will also age and the performance will decline, resulting in reduced robot arm operation accuracy, vibration, changes in response speed and other adverse results. In the prior art, as the operating years increase, the servo joint module ages and causes performance degradation, resulting in a decline in robot arm operation accuracy or other performance. In addition to the necessary physical component maintenance, the servo joint module controller parameters are usually re-adjusted and optimized to achieve the original performance. Therefore, it is a challenge to enable the servo module to autonomously warn of such performance changes and prevent or take maintenance measures in advance. Summary of the invention

[0003] In view of this, the present invention proposes a robot joint module servo controller with a digital twin model, which is provided with a first digital signal processor and a second digital signal processor, and the second digital signal processor is provided with a digital twin model composed of a twin control loop and a motor module model. The present invention uses the digital twin model in the second digital signal processor to twin the control and operation status of the original joint module, and uses the load size calculated by the load observer in the first digital signal processor to provide the twin model to simulate the real-time operation status of the motor, and finally obtains the early warning information of the motor module, which can monitor the operation status of the joint module in real time, and reflect the theoretical characteristics of the joint module in real time, so as to analyze the early warning information and enable the staff to make advance deployment.

[0004] In order to achieve the above technical objectives, the specific technical solutions adopted by the present invention are:

[0005] A robot joint module servo controller with a digital twin model, comprising:

[0006] A first digital signal processor receives an external instruction and controls the joint motor of the robot joint module based on the actual control loop;

[0007] A second digital signal processor communicates with the first digital signal processor and runs a digital twin model; the digital twin model is provided with a twin control loop and a motor module model;

[0008] A load observer, running on the first digital signal processor, calculates the load size of the joint motor based on the actual speed of the joint motor, the motor current and the actual motor and load inertia;

[0009] Among them: the digital twin model operates based on the external instructions, the given speed and actual speed of the joint motor, the motor current, the motor inertia of the joint motor, the gear clearance effect of the reducer configured for the joint motor and the load size to obtain the operating current difference and operating speed difference between the motor module model and the joint motor.

[0010] Furthermore, the actual control loop realizes the control of the joint motor based on a position controller, a speed controller, a current controller, a speed feedback processing unit and a position feedback processing unit.

[0011] Furthermore, a twin control loop is provided in the digital twin model; the twin control loop includes a twin position controller, a twin speed controller and a twin current controller which are the same as the actual control loop; the twin control loop simulates the speed feedback processing unit based on the speed converter, and simulates the position feedback processing unit based on the position converter; the data of the speed converter and the position converter are extracted from the motor module model.

[0012] Furthermore, the mathematical model expression of the joint motor is as follows:

[0013]

[0014]

[0015] Wherein, Ud and Uq are the d-axis and q-axis voltage components applied to the joint motor in the dq coordinate system, respectively; Rs and Ls are the armature resistance and inductance of the joint motor, respectively; W m is the motor speed of the joint motor; λpm is the permanent magnet flux of the joint motor;

[0016] Then the expression of the motor module model is as follows:

[0017]

[0018]

[0019]

[0020] Wherein: Ks is the elastic coefficient of the motor and load coupling of the motor module model; Jm is the motor inertia of the motor module model; JL is the load inertia of the motor module model; Te is the motor electromagnetic torque of the motor module model; Ts is the Coulomb friction torque; ωm is the motor speed; ω L is the load speed.

[0021] Furthermore, the servo controller obtains the warning information of the motor module based on the running current difference between the motor module model and the joint motor and the running speed difference between the motor module model and the joint motor.

[0022] Furthermore, the method for obtaining the warning information is:

[0023] Based on the timeline, respectively draw a curve of the operating current difference and a curve of the operating speed difference, and extract the most significant frequency in the two groups of curves;

[0024] Based on the two groups of numerical curves of the most significant frequencies, the aging law and fault information of the robot joint module are estimated.

[0025] Furthermore, the servo controller also includes an analysis and judgment module; the analysis and judgment module is used to compare and analyze the curve of the current difference and the curve of the running speed difference to determine whether there is any abnormality in the robot joint module.

[0026] Furthermore, the servo controller also includes a feedback module; the feedback module feeds back the abnormality to a host computer of the servo controller. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments 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.

[0028] Figure 1 It is a module block diagram of an actual control loop in a specific implementation mode of the present invention;

[0029] Figure 2 It is a module block diagram of the digital twin model in a specific implementation manner of the present invention;

[0030] Figure 3 It is a working block diagram of a load observer in a specific implementation mode of the present invention;

[0031] Figure 4 It is a block diagram of the interaction principle between the first DSP and the second DSP in a specific implementation manner of the present invention;

[0032] Figure 5 It is a block diagram of the overall architecture of the first DSP and the second DSP digital control in a specific implementation manner of the present invention;

[0033] Figure 6 It is a block diagram of a load system model in a specific implementation manner of the present invention;

[0034] Figure 7 It is a flowchart of the second DSP running data processing in a specific implementation mode of the present invention;

[0035] Figure 8 It is a schematic diagram of the calculation results of the digital twin model when a touch occurs on the outside of the robot arm in a specific embodiment of the present invention;

[0036] Among them: 1. Position controller; 2. Speed ​​controller; 3. Current controller; 4. Joint motor; 5. Speed ​​feedback processing unit; 6. Position feedback processing unit; 7. Twin position controller; 8. Twin speed controller; 9. Twin current controller; 10. Motor module model; 11. Speed ​​converter; 12. Position converter; 13. Analysis and judgment module; 14. Load observer. DETAILED DESCRIPTION

[0037] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0038] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0039] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present invention, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0040] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention. The illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0041] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects described may be practiced without these specific details.

[0042] In one embodiment of the present invention, a robot joint module servo controller with a digital twin model is proposed, comprising:

[0043] A first digital signal processor receives an external instruction and controls the joint motor 4 of the robot joint module based on the actual control loop;

[0044] The second digital signal processor communicates with the first digital signal processor and runs a digital twin model; the digital twin model is provided with a twin control loop and a motor module model 10;

[0045] A load observer 14, running on the first digital signal processor, calculates the load size of the joint motor based on the actual speed, motor current and actual motor and load inertia of the joint motor 4;

[0046] Among them: the digital twin model operates based on external instructions, the actual speed of the joint motor 4, the motor inertia of the joint motor 4, the gear clearance effect of the reducer configured for the joint motor 4, and the load size to obtain the operating current difference and operating speed difference between the motor module model 10 and the joint motor 4.

[0047] The joint motor 4 of this embodiment is a servo motor, and the first digital signal processor and the second digital signal processor are both conventional DSPs or two independent cores in the same DSP; it has the advantage of small size and easy integration. This embodiment uses two DSPs or two DSP cores to make a servo controller with a digital twin model, which is simpler, more convenient and low-cost than the traditional digital twin method.

[0048] like Figure 1 As shown, the actual control loop of this embodiment realizes the control of the joint motor 4 based on the position controller 1 , the speed controller 2 , the current controller 3 , the speed feedback processing unit 5 and the position feedback processing unit 6 .

[0049] like Figure 2As shown, a twin control loop is provided in the digital twin model; the twin control loop includes a twin position controller 7, a twin speed controller 8 and a twin current controller 9 which are the same as the actual control loop; the twin control loop simulates the speed feedback processing unit 5 based on the speed converter 11, and simulates the position feedback processing unit 6 based on the position converter 12; the data of the speed converter 11 and the position converter 12 are extracted from the motor module model 10.

[0050] In this embodiment, a load observer 14 is provided to calculate the load inertia, and the load value of the motor module can be calculated as the load of the motor in the twin model.

[0051] The joint motor 4 of this embodiment is equipped with a reducer. The gear clearance effect of the reducer is also an important factor affecting the accuracy of the digital twin result. The actual control loop receives instructions (external instructions) from the robot controller to drive the joint motor 4 to perform corresponding actions. The basic control algorithm block diagram of the actual control loop is shown in the figure. Figure 1 shown.

[0052] The actual control loop and load observer 14 of this embodiment run on the first DSP, and the motor module model 10 runs on the second DSP. In the second DSP, a digital twin model of the original joint motor 4 and the actual control loop is established based on the actual control system control parameters and system parameters. The twin model has the same controller as the actual system, and a load equivalent model with similar characteristics of the actual motor, reducer and load, and receives the same control instructions as the actual system. Figure 2 As shown, the digital twin model includes: a position controller 1 that is the same as the position controller 1 in the first DSP; a speed controller 2 that is the same as the speed controller 2 in the first DSP; a current controller 3 that is the same as the current controller 3 in the first DSP; the load observation value TL′ comes from the output value of the load observer 14 in the first DSP; the module model includes a motor model and a load model.

[0053] like Figure 2 As shown, the external instruction of this embodiment is a position instruction, that is, controlling the joint motor 4 to run to the corresponding position, and the position instruction in the digital twin model and the position instruction in the first DSP are the same instruction value.

[0054] In the digital twin model, the actual control loop and the motor module model 10 are established respectively, and the load equivalent model that can reflect the characteristics of the reducer is also established. These models constitute a complete digital twin mathematical model. The second DSP runs these models independently of the first DSP, but the second DSP also receives position instructions from the upper robot controller, and the position feedback from the load model constitutes the actual position control loop, the speed feedback from the load model constitutes the speed closed loop, and the current feedback from the joint motor 4 model constitutes the current closed loop control.

[0055] In the first DSP, in addition to running the actual control loop as the control algorithm of the joint motor 4, a load observer 14 is also running to estimate the load of the joint motor 4 in real time. The real-time estimated load value is transmitted to the second DSP and applied to the motor module model 10 as the load of the digital twin model, such as Figure 3 As shown, Figure 3 middle:

[0056] Kt: electromagnetic torque constant of joint motor 4;

[0057] Te″: electromagnetic torque of joint motor 4;

[0058] TL′: estimated load torque; (input into the digital twin model in the second DSP as the load of the motor module model 10)

[0059] ωm′: Motor speed estimated in the load observer

[0060] ω(t): actual speed of joint motor 4;

[0061] HPF:High Pass Filter, high pass filter;

[0062] Jm: motor inertia of joint motor 4;

[0063] JL: load inertia of joint motor 4;

[0064] S: Laplace operator;

[0065] i(t): current of joint motor 4;

[0066] θ(t): rotor position angle of joint motor 4;

[0067] The load observer 14 runs on the first DSP. Its input is the motor speed ω(t) and the motor current i(t); its output is the estimated load torque TL′ and the compensation amount (the output of the HPF enters the actual motor speed loop).

[0068] In the load observer 14, the module HPF refers to the High Pass Filter, which feeds back the high-frequency components in the speed difference between the actual speed of the joint motor 4 and the speed output by the observer's theoretical load model (including the motor inertia Jm and the load inertia JL) to the actual motor actual control loop for compensation, thereby achieving the purpose of the dynamic components in the theoretical load model in the observer tracking the dynamic components in the actual system. The theoretical model itself realizes theoretical speed closed-loop control through controller A, and the torque output by the controller is input as the load torque to the second DSP as the load torque input of the digital twin model.

[0069] In this way, in theory, the characteristic indicators of the operation of the digital twin model, such as instantaneous speed, instantaneous torque, characteristic vibration frequency and other dynamic or static characteristics should be basically close to or even equal to the actual system, thereby reflecting the characteristics of the actual system and obtaining early warning information based on the characteristics of the actual system.

[0070] The method for obtaining the early warning information in this embodiment is:

[0071] Based on the time line, a curve of the running current difference and a curve of the running speed difference are respectively drawn, and characteristic frequencies in the two groups of curves are extracted;

[0072] Based on the numerical curves of the two sets of characteristic frequencies, the aging law and fault information of the joint motor 4 are estimated.

[0073] When the dynamic indicators of the actual system and the dynamic indicator errors output by the model change significantly over a long period of time, it means that the properties of the physical components of the actual system have changed. The host computer then outputs relevant fault information or aging conditions as a prompt, thereby making the module controller more intelligent and capable of self-diagnosis.

[0074] In this embodiment, the first DSP provides the second DSP with position instructions, real-time speed, real-time current and load observation values. The second DSP provides the first DSP with early warning information; the first DSP communicates with the upper robot control and exchanges data.

[0075] In addition to running the digital twin model of the module, the second DSP also needs to process, analyze and judge the parameters from the first DSP, and synthesize them into a final output to the first DSP for the first DSP to upload to the upper robot controller.

[0076] like Figure 4 Shown is a block diagram of the interaction principle between two DSPs.

[0077] The overall architecture of the first and second DSP digital control is as follows Figure 5 As shown, Figure 5 middle:

[0078] θ(t): rotor position of joint motor 4;

[0079] ω(t): motor speed of joint motor 4;

[0080] i(t): current of joint motor 4;

[0081] θref(t): position given value;

[0082] θt(t): motor rotor position of motor module model 10;

[0083] ωt(t): motor speed of motor module model 10;

[0084] it(t): motor current of motor module model 10;

[0085] The first DSP runs the actual control system algorithm, including the position loop, speed loop and current loop required to control the joint motor 4. The first DSP runs an industrial communication bus, which is responsible for communicating with the upper robot controller, exchanging data, transmitting alarm information, receiving instructions, etc.

[0086] The digital twin model of this module runs in the second DSP. The digital twin model receives position instructions and load observation values ​​from the first DSP, and forms a three-ring control system for self-operation, which is similar to an actual control system with a load model, and has servo performance close to the actual control of the first DSP.

[0087] An analysis and judgment module 13 is also running in the second DSP to compare and analyze the results output by the digital twin model and relevant parameters of the actual system to determine whether there is any abnormality in the actual system.

[0088] The block diagram of the joint motor 4 model and the load system model in the motor module model 10 is as follows Figure 6 As shown, the position feedback link in the load system model has a module that reflects the backlash effect of the reducer gear.

[0089] The mathematical model expression of the joint motor is as follows:

[0090]

[0091]

[0092] Wherein, Ud and Uq are the d-axis and q-axis voltage components applied to the joint motor 4 in the dq coordinate system; Rs and Ls are the armature resistance and inductance of the joint motor 4; Wm is the motor speed of the joint motor 4; λpm is the permanent magnet flux of the joint motor 4;

[0093] The expression of the motor module model is as follows:

[0094]

[0095]

[0096]

[0097] Wherein: Ks is the elastic coefficient of the coupling between the motor and the load of the motor module model 10; Jm is the motor inertia of the motor module model 10; JL is the load inertia of the motor module model 10; Te is the electromagnetic torque of the motor of the motor module model 10; Ts is the Coulomb friction torque; ωm is the motor speed; ωL is the load speed.

[0098] In this embodiment, the servo controller obtains the warning information of the motor module based on the running current difference between the motor module model and the joint motor and the running speed difference between the motor module model and the joint motor.

[0099] In one embodiment, the servo controller further includes an analysis and judgment module 13; the analysis and judgment module 13 is used to compare and analyze the current difference curve and the running speed difference curve to determine whether there is an abnormality in the robot joint module.

[0100] In one embodiment, the servo controller further includes a feedback module; the feedback module feeds back abnormalities to a host computer of the servo controller.

[0101] In this embodiment, in the digital twin model, the data received from the first DSP must be compared and historical data of a certain length must be recorded. If the data shows a large deviation over a period of time, it means that the actual system has changed and the original control parameters can no longer achieve the expected performance. The feedback module will then issue a prompt to the upper-level controller to draw attention, concern, or prompt the necessity of maintenance, thereby achieving the purpose of early warning and improving the intelligence level of the joint module and the reliability of long-life high-performance operation.

[0102] like Figure 7 The figure is a flow chart of the second DSP running data processing.

[0103] Figure 7 The flowchart of real-time processing and judgment of relevant data is shown in FIG. After the data is calculated, it is finally analyzed in the frequency domain to determine whether the actual system needs to be reminded of maintenance or has problems.

[0104] like Figure 7 As shown, Sign_maintenance indicates the category that triggers the warning:

[0105] Sign_maintenance = 1, indicating that during the actual system operation, a sudden external force may be applied to the robot arm components, which requires an early warning;

[0106] Sign_maintenance = 2, indicating that the actual system high-frequency characteristics have changed significantly, which means that the system has obvious vibration, which may cause an increase in positioning errors and require an early warning.

[0107] Sign_maintenance = 3, indicating that the actual system low-frequency characteristics have changed significantly, which means that the system mechanical components may have potential failures or even looseness, and an early warning needs to be triggered.

[0108] like Figure 8The figure shows the ferr_vel data curve calculated by the digital twin model when the robot arm touches an external object during operation. At time t0, its value exceeds the threshold value, then Sign_maintenance=1 is set and sent to the first DSP, triggering early warning processing.

[0109] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A robot joint module servo controller with a digital twin model, characterized in that: include: A first digital signal processor receives an external instruction and controls the joint motor of the robot joint module based on the actual control loop; A second digital signal processor communicates with the first digital signal processor and runs a digital twin model; the digital twin model is provided with a twin control loop and a motor module model; The twin control loop includes a twin position controller, a twin speed controller and a twin current controller which are the same as those of the actual control loop; the actual control loop controls the joint motor based on the position controller, the speed controller, the current controller, the speed feedback processing unit and the position feedback processing unit; A load observer, running on the first digital signal processor, calculates the load size of the joint motor based on the actual speed of the joint motor, the motor current and the actual motor and load inertia; Among them: the digital twin model operates based on the external instructions, the actual speed of the joint motor, the motor current, the motor inertia of the joint motor, the gear clearance effect of the reducer configured for the joint motor and the load size to obtain the operating current difference and operating speed difference between the motor module model and the joint motor.

2. The servo controller according to claim 1, characterized in that: The twin control loop simulates the speed feedback processing unit based on a speed converter, and simulates the position feedback processing unit based on a position converter; data of the speed converter and the position converter are extracted from the motor module model.

3. The servo controller according to claim 1, characterized in that: The servo controller obtains warning information of the motor module based on the operating current difference between the motor module model and the joint motor and the operating speed difference between the motor module model and the joint motor.

4. The servo controller according to claim 3, characterized in that: The method for obtaining the warning information is: Based on the timeline, respectively draw a curve of the operating current difference and a curve of the operating speed difference, and extract the most significant frequency in the two groups of curves; Based on the two groups of numerical curves of the most significant frequencies, the aging law and fault information of the robot joint module are estimated.

5. The servo controller according to claim 4, characterized in that: The servo controller also includes an analysis and judgment module; the analysis and judgment module is used to compare and analyze the curve of the current difference and the curve of the running speed difference to determine whether there is any abnormality in the robot joint module.

6. The servo controller according to claim 5, characterized in that: The servo controller further comprises a feedback module; the feedback module feeds back the abnormality to a host computer of the servo controller.

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