A humanoid robot joint servo module torque compensation control method

Abstract

The application discloses a humanoid robot joint servo module torque compensation control method, and relates to the technical field of joint torque control, which comprises the following steps: collecting motor side encoder angle, joint output end angle, motor phase current, temperature state, trunk posture, foot bottom contact state, target speed and target torque, and constructing joint motion state quantity; calculating corresponding compensation torque according to the joint motion state quantity; combining the commutation prediction window, the action stage, the left-right symmetrical joint compensation difference and the impact contact state to generate the amplitude-limited target torque compensation quantity; superimposing the amplitude-limited target torque compensation quantity and the target torque to generate the compensated target torque, and converting the compensated target torque into motor target current to execute current loop control. The application realizes nonlinear dynamic compensation of the transmission chain, weakens commutation hysteresis and contact impact, and guarantees smooth torque output and operation safety of the whole machine.

Description

Technical Field

[0001] This invention relates to the field of joint torque control technology, and in particular to a torque compensation control method for a humanoid robot joint servo module. Background Technology

[0002] As the core execution unit for achieving humanoid motion, the torque control accuracy of the humanoid robot's joint servo module directly affects the robot's dynamic response, walking stability, and environmental interaction compliance. Currently, joint torque control commonly employs a feedforward compensation strategy based on dynamic models, improving torque tracking performance through gravity compensation, inertial compensation, and friction compensation. Gravity compensation calculates static torque based on the mass and center of mass of the limb segments; inertial compensation estimates dynamic torque using equivalent moment of inertia and acceleration; and friction compensation improves low-speed motion quality through Coulomb friction and viscous friction models. Furthermore, some studies introduce adjacent joint coupling compensation to address torque coupling effects in multi-joint cooperative motion and use temperature monitoring to attenuate and compensate for temperature rise in motor windings and reducers. Under ideal operating conditions, these methods can improve the accuracy and response speed of joint torque control to a certain extent.

[0003] However, existing torque compensation methods still have shortcomings in terms of the completeness of compensation dimensions and stage adaptability. On the one hand, traditional methods mainly focus on conventional dynamic compensation terms such as gravity, inertia, and friction, lacking a systematic compensation mechanism for the inherent nonlinear characteristics of the transmission chain, such as output hysteresis caused by reducer transmission clearance and backlash caused by elastic torsion of flexible connectors and output flanges. On the other hand, existing methods usually adopt fixed compensation strategies, failing to dynamically adjust the participation degree of each compensation component according to different action stages such as joint support bearing, swing following, posture recovery, or external disturbance suppression, and also lacking identification and response mechanisms for compensation differences between left and right symmetrical joints and impact contact states. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a torque compensation control method for a humanoid robot joint servo module to solve the problems of incomplete compensation dimensions and lack of adaptive adjustment during motion stages in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] This invention provides a torque compensation control method for a humanoid robot joint servo module, comprising: acquiring the encoder angle on the motor side of the target joint, the joint output angle, the motor phase current, the temperature state, the torso posture, the foot contact state, the target speed, and the target torque; calculating the actual speed, actual acceleration, and comprehensive angular deviation of the transmission chain of the joint to construct joint motion state quantities; calculating gravity compensation torque, inertia compensation torque, adjacent joint coupling compensation torque, friction compensation torque, temperature rise attenuation compensation torque, clearance transition compensation torque, and elastic backlash compensation torque based on the joint motion state quantities; establishing a reversal prediction window based on the target speed direction and the target torque direction; determining the action stage based on the foot contact state, torso posture, and joint load state; and generating a limited target torque compensation quantity by combining the compensation differences of the left and right symmetrical joints and the impact contact state; superimposing the limited target torque compensation quantity with the target torque to generate a compensated target torque, converting it into a target motor current, and executing current loop control by the servo driver.

[0008] As a preferred embodiment of the torque compensation control method for the humanoid robot joint servo module described in this invention, the acquisition of the target joint's motor-side encoder angle, joint output angle, motor phase current, temperature status, torso posture, foot contact status, target speed, and target torque includes: acquiring the target joint's motor-side encoder angle and joint output angle in each servo control cycle; acquiring the motor phase current, bus voltage, motor winding temperature, and reducer housing temperature; acquiring the robot's torso posture and foot contact status; receiving the target joint position, target speed, and target torque from the upper controller; and using the motor-side encoder angle, joint output angle, motor phase current, temperature status, torso posture, foot contact status, target speed, and target torque as real-time operating data of the target joint servo module.

[0009] As a preferred embodiment of the torque compensation control method for the humanoid robot joint servo module described in this invention, the calculation of the actual joint speed, actual acceleration, and comprehensive transmission chain angle deviation includes: calculating the converted angle from the motor side to the joint output end based on the encoder angle on the motor side and the transmission ratio of the reducer; calculating the actual joint speed based on the joint output end angle of the current control cycle and the joint output end angle of the previous control cycle; calculating the actual joint acceleration based on the actual joint speed of the current control cycle and the joint actual speed of the previous control cycle; and generating the comprehensive transmission chain angle deviation based on the difference between the converted angle and the joint output end angle.

[0010] As a preferred embodiment of the torque compensation control method for the joint servo module of the humanoid robot described in this invention, the calculation of gravity compensation torque, inertia compensation torque, and adjacent joint coupling compensation torque includes: calculating gravity compensation torque based on the equivalent mass of the limb segment driven by the target joint, the equivalent distance from the center of mass to the rotation center of the target joint, and the angle of the joint output end; calculating inertia compensation torque based on the equivalent moment of inertia of the target joint converted to the output end and the actual acceleration of the joint; calculating adjacent joint coupling compensation torque based on the actual velocity of adjacent joints that have a motion coupling relationship with the target joint, the actual velocity of the target joint, and the coupling coefficient of the adjacent joints to the target joint; and generating the nominal driving torque of the joint based on the gravity compensation torque, inertia compensation torque, and adjacent joint coupling compensation torque.

[0011] As a preferred embodiment of the torque compensation control method for the joint servo module of the humanoid robot described in this invention, the calculation of the friction compensation torque, temperature rise attenuation compensation torque, clearance transition compensation torque, and elastic hysteresis compensation torque includes: calculating the friction compensation torque based on the actual joint speed, Coulomb friction compensation coefficient, viscous friction compensation coefficient, static friction compensation coefficient, and low-speed friction smoothing speed threshold; calculating the temperature rise attenuation compensation torque based on the motor winding temperature or reducer housing temperature, reference temperature, temperature rise compensation coefficient, and nominal joint driving torque; calculating the clearance transition compensation torque based on the comprehensive angle deviation of the transmission chain, the allowable transmission clearance threshold, and the transmission clearance compensation stiffness coefficient; and calculating the elastic hysteresis compensation torque based on the comprehensive angle deviation of the transmission chain in the current control cycle, the comprehensive angle deviation of the transmission chain in the previous control cycle, the equivalent torsional stiffness of the transmission chain, and the equivalent damping coefficient of the transmission chain.

[0012] As a preferred embodiment of the torque compensation control method for the humanoid robot joint servo module described in this invention, the step of establishing a reversal prediction window based on the target velocity direction and the target torque direction includes: reading the target velocity of the current control cycle and the target velocity of the previous control cycle, and determining whether the target velocity direction has reversed; reading the target torque of the current control cycle and the target torque of the previous control cycle, and determining whether the target torque direction has reversed; when the target velocity direction or the target torque direction reverses, determining that the target joint enters the reversal prediction window; when the target joint enters the reversal prediction window, increasing the participation of the gap transition compensation torque and limiting the rate of change of the gap transition compensation torque, so that the gap transition compensation torque intervenes in advance before the target joint reversal.

[0013] As a preferred embodiment of the torque compensation control method for the joint servo module of the humanoid robot described in this invention, the step of determining the action stage based on the foot contact state, torso posture, and joint load-bearing state includes: when the foot contact state is contact and the target joint bears a continuous load-bearing torque, the target joint is determined to be in the support load-bearing stage; when the foot contact state is not contact and the target joint performs a swing trajectory following according to the target speed, the target joint is determined to be in the swing following stage; when the torso posture deviates from the preset posture range and the target joint is used to restore the robot's posture balance, the target joint is determined to be in the posture recovery stage; when the target joint is subjected to external collision, foot impact, or contact reaction force disturbance, the target joint is determined to be in the external disturbance suppression stage; and the participation coefficient of each compensation torque is determined according to the action stage.

[0014] As a preferred embodiment of the torque compensation control method for the joint servo module of the humanoid robot described in this invention, the step of generating a limited target torque compensation amount by combining the compensation difference of the left and right symmetrical joints includes: obtaining the target torque compensation amount of the left and right symmetrical joints corresponding to the target joint; calculating the left and right symmetrical joint compensation difference between the target torque compensation amount of the left joint and the target torque compensation amount of the right joint; when the compensation difference of the left and right symmetrical joints exceeds the allowable compensation difference threshold of the left and right symmetrical joints, and the left and right joints are in the same action stage, limiting the rate of change of the target torque compensation amount on the side with the larger compensation amount, or enhancing the compensation of the target torque compensation amount on the side with the smaller compensation amount; the left and right symmetrical joints include the left and right hip joints, the left and right knee joints, the left and right ankle joints, the left and right shoulder joints, the left and right elbow joints, or the left and right wrist joints.

[0015] As a preferred embodiment of the torque compensation control method for the joint servo module of the humanoid robot described in this invention, generating the limited target torque compensation amount in conjunction with the impact contact state includes: calculating the target torque change rate based on the target torque of the current control cycle and the target torque of the previous control cycle; calculating the comprehensive angle deviation change amount based on the comprehensive angle deviation of the transmission chain in the current control cycle and the comprehensive angle deviation of the transmission chain in the previous control cycle; determining that the target joint is in an impact contact state when the target torque change rate exceeds the impact contact judgment threshold and the foot contact state changes, or when the comprehensive angle deviation change amount exceeds the comprehensive angle deviation change threshold; when the target joint is in an impact contact state, reducing the participation coefficient of the inertial compensation torque and the clearance transition compensation torque, while retaining the gravity compensation torque and the elastic backlash compensation torque.

[0016] As a preferred embodiment of the torque compensation control method for the humanoid robot joint servo module described in this invention, the step of superimposing the limited target torque compensation amount with the target torque to generate a compensated target torque, converting it into a motor target current, and having the servo driver execute current loop control includes: superimposing the limited target torque compensation amount with the target torque sent by the upper controller to generate a compensated target torque; calculating the motor target current based on the compensated target torque, the motor torque constant, the reducer transmission ratio, and the reducer transmission efficiency; when the motor target current exceeds the allowable output current of the servo driver, limiting the motor target current; the servo driver executing current loop control based on the limited motor target current, causing the motor to output the corresponding compensated driving torque to the joint output terminal via the reducer; when overcurrent, overtemperature, encoder abnormality, bus voltage abnormality, joint reverse impact, or torque error exceeding the safety threshold is detected, the target joint is switched to torque-limiting holding mode or unloading protection mode.

[0017] The beneficial effects of this invention are as follows: by constructing a multi-dimensional compensation architecture, the system compensates for nonlinear factors in the transmission chain, improving the accuracy of torque tracking and position control; by identifying the action stage and dynamically adjusting the compensation coefficient, adaptive matching is achieved, avoiding overcompensation or undercompensation; by establishing a commutation prediction and impact identification mechanism, the gap is actively compensated and the transient response is softened, reducing impact and hysteresis; by limiting the compensation amount and monitoring the left-right symmetry difference, smooth torque output and safe operation of the whole machine are ensured. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart of a torque compensation control method for a humanoid robot joint servo module.

[0020] Figure 2 Flowchart for constructing joint motion state parameters and judging data validity.

[0021] Figure 3 Flowchart for multi-compensation torque calculation and reversal prediction.

[0022] Figure 4 The flowchart shows the generation of the target torque compensation and the current loop control.

[0023] Figure 5 This is a diagram showing the effect of suppressing dynamic tracking errors in the knee joint.

[0024] Figure 6This diagram illustrates the effect of suppressing impact deviation during transmission chain reversal. Detailed Implementation

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0026] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0027] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0028] Reference Figures 1-6 As one embodiment of the present invention, this embodiment provides a torque compensation control method for a humanoid robot joint servo module, comprising the following steps:

[0029] S1. Collect the encoder angle on the motor side of the target joint, the angle of the joint output end, the motor phase current, the temperature status, the torso posture, the foot contact status, the target speed and the target torque, calculate the actual speed of the joint, the actual acceleration and the comprehensive angle deviation of the transmission chain, and construct the joint motion state quantities.

[0030] S1.1 Collect real-time operating data of the target joint servo module.

[0031] Furthermore, within each servo control cycle, the following data are collected: the encoder angle on the motor side of the target joint, the joint output angle, the motor phase current, the bus voltage, the motor winding temperature, the reducer housing temperature, the robot's torso posture, the foot contact state, as well as the target joint position, target speed, and target torque issued by the upper controller.

[0032] Among them, the encoder angle on the motor side is used to characterize the actual rotation position of the motor rotor; the joint output end angle is used to characterize the actual rotation position of the reducer output end or the joint connecting rod end; the motor phase current is used to characterize the current motor output torque state; the bus voltage is used to determine the power supply capability of the servo driver; the motor winding temperature and the reducer housing temperature are used to determine the temperature rise state of the servo module; the robot torso posture is used to determine the overall posture change of the humanoid robot; and the foot contact state is used to determine whether the lower limb joints are in the process of supporting and bearing load.

[0033] It should be noted that the plantar contact state can be determined by a plantar pressure sensor, a plantar contact switch, or changes in ankle joint force; the robot's torso posture can be obtained by an inertial measurement unit, which includes at least an angular velocity meter and an accelerometer.

[0034] S1.2 Calculate the actual motion parameters at the joint output end.

[0035] Furthermore, let the first Within each control cycle, the encoder angle on the motor side is The gear ratio of the reducer is The angle of the joint output end is The control cycle is The angle from the motor side to the joint output end is:

[0036] ;

[0037] in, This indicates the angle from the motor side to the joint output end.

[0038] The actual speed at the joint output end is:

[0039] ;

[0040] in, Indicates the first The actual speed of the joint output end within each control cycle. This indicates the angle of the joint output end during the previous control cycle.

[0041] The actual acceleration at the joint output end is:

[0042] ;

[0043] in, Indicates the first The actual acceleration of the joint output during each control cycle. This indicates the actual speed of the joint output during the previous control cycle.

[0044] S1.3 Calculate the overall angle deviation of the servo module drive chain.

[0045] Furthermore, based on the angle calculated from the motor side to the joint output end and the angle of the joint output end, the overall angle deviation of the servo module transmission chain is calculated:

[0046] ;

[0047] in, This indicates the overall angular deviation of the servo module's drivetrain.

[0048] It should be noted that the comprehensive angle deviation of the servo module transmission chain is used to characterize the angle deviation caused by the combined effects of reducer transmission clearance, elastic torsion of flexible connectors, deformation of output flanges, and joint linkage connection clearance during the process of transmitting motion from the motor side to the joint output end.

[0049] S1.4 Construct joint motion state quantities.

[0050] Furthermore, the target joint position, actual joint position, actual velocity, actual acceleration, motor current, bus voltage, temperature status, torso posture, foot contact status, and comprehensive angular deviation are collectively constituted as joint motion state quantities.

[0051] Joint motion state quantities are represented as follows: ;

[0052] in, Indicates the first Joint motion state quantities within a control cycle Indicates the position of the target joint. Indicates the actual joint position. Indicates the target joint velocity. Indicates the actual joint velocity. This represents the actual joint acceleration. Indicates the phase current of the motor. Indicates bus voltage. Indicates the temperature of the motor windings. Indicates the temperature of the reducer housing. Indicates the state of contact between the sole of the foot and the skin. This indicates the overall angular deviation of the servo module's drivetrain.

[0053] S1.5, Perform a validity check on the status data.

[0054] Furthermore, the validity of encoder data, current data, bus voltage data, and temperature data is determined.

[0055] When the encoder angle on the motor side or the output angle of the joint exceeds the mechanical limit range of the corresponding joint, the encoder data is determined to be abnormal.

[0056] When the motor phase current exceeds the allowable current range of the servo driver, the current data is determined to be abnormal.

[0057] When the bus voltage is lower than the driver's minimum operating voltage or higher than the driver's maximum operating voltage, the bus voltage data is considered abnormal.

[0058] When the temperature of the motor windings or the temperature of the reducer housing exceeds the preset temperature protection threshold, the temperature data is determined to be abnormal.

[0059] When encoder data, current data, bus voltage data, or temperature data are abnormal, maintain the safety torque command of the previous control cycle and restrict the target joint from entering the low-speed protection state.

[0060] It should be noted that the safety torque command refers to the torque command that does not exceed the safety output boundary of the target joint servo module and can maintain the current posture of the humanoid robot without sudden changes; the preset temperature protection threshold is used to determine whether the motor winding or reducer housing has entered the over-temperature protection state. It is derived from the motor insulation level, the allowable operating temperature of the reducer grease and the thermal balance test results of the servo module, and the value range is usually [60℃, 120℃].

[0061] S2. Calculate the gravity compensation torque, inertia compensation torque, adjacent joint coupling compensation torque, friction compensation torque, temperature rise attenuation compensation torque, clearance transition compensation torque, and elastic backlash compensation torque based on the joint motion state quantities.

[0062] S2.1 Calculate the nominal driving torque of the joint.

[0063] Furthermore, based on the current posture of the humanoid robot, the target joint position, the actual joint position, and the motion state of adjacent joints, the nominal driving torque of the target joint in the current action phase is calculated.

[0064] The nominal driving torque of a joint includes gravity compensation torque, inertia compensation torque, and coupling compensation torque between adjacent joints. Its calculation formula is as follows:

[0065] ;

[0066] in, This represents the nominal driving torque of the joint. This represents the gravitational compensation torque. Indicates the inertial compensation torque. This indicates the coupling compensation torque between adjacent joints.

[0067] S2.2 Calculate the gravity compensation torque.

[0068] Furthermore, based on the equivalent mass, center of mass position, and output end angle of the limb segment driven by the target joint, the gravity compensation torque is calculated:

[0069] ;

[0070] in, It represents the equivalent mass of the limb segment driven by the target joint. Represents gravitational acceleration. This represents the equivalent distance from the center of mass of the limb segment to the center of rotation of the target joint. This indicates the output angle of the target joint.

[0071] It should be noted that when the target joint is the knee joint, the limb segment driven by the target joint may include the lower leg segment and the equivalent mass of the foot; when the target joint is the hip joint, the limb segment driven by the target joint may include the thigh segment, the lower leg segment and the equivalent mass of the foot; when the target joint is the shoulder joint, the limb segment driven by the target joint may include the upper arm segment, the forearm segment and the equivalent mass of the end effector.

[0072] S2.3 Calculate the inertia compensation torque.

[0073] Furthermore, based on the equivalent moment of inertia of the target joint referred to the output end and the actual acceleration at the joint output end, the inertial compensation torque is calculated:

[0074] ;

[0075] in, This represents the equivalent moment of inertia of the target joint referred to the output. This represents the actual acceleration at the joint output end.

[0076] It should be noted that the equivalent moment of inertia It can be calculated based on the servo module motor rotor inertia, reducer transmission ratio, output end connecting rod inertia, and load inertia, or it can be obtained through joint servo module calibration experiments.

[0077] S2.4 Calculate the coupling compensation torque between adjacent joints.

[0078] Furthermore, based on the actual velocities of adjacent joints that have a kinematic coupling relationship with the target joint, the coupling compensation torque of the adjacent joints is calculated:

[0079] ;

[0080] in, This indicates the number of adjacent joints that have a kinematic coupling relationship with the target joint. Indicates the first The coupling coefficient of each adjacent joint to the target joint. Indicates the first The actual speed of each adjacent joint This indicates the actual speed at the output end of the target joint.

[0081] The coupling coefficient between adjacent joints and the target joint is derived from the fitting result of the velocity coupling term on the torque change of the target joint in the synchronous motion experiment between the target joint and adjacent joints. The value range is usually [-10N.m.s² / rad², 10N.m.s² / rad²].

[0082] For example, when the target joint is the knee joint, adjacent joints may include the hip joint and the ankle joint; when the target joint is the elbow joint, adjacent joints may include the shoulder joint and the wrist joint.

[0083] S2.5 Calculate the friction compensation torque.

[0084] Furthermore, based on the actual speed of the target joint, the friction compensation torque of the servo module is calculated:

[0085] ;

[0086] in, This indicates the friction compensation torque. Indicates the Coulomb friction compensation coefficient. This represents the viscous friction compensation coefficient. Indicates the static friction compensation coefficient. This indicates the threshold speed for smoothing low-speed friction.

[0087] It should be noted that the friction compensation torque is used to compensate for the frictional hysteresis generated by the humanoid robot joint servo module during low-speed crawling, starting, stopping, and reversing; the low-speed friction smoothing speed threshold is used to smooth low-speed static friction and Coulomb friction, and is derived from the speed range when static friction transitions to dynamic friction in the joint low-speed crawling experiment, with a value range of [0.001 rad / s, 0.50 rad / s]; the Coulomb friction compensation coefficient is derived from the average friction torque corresponding to the stable current in the target joint during the low-speed uniform forward and reverse rotation experiment, with a value range of [0.01 N·m, 20 N·m]; the viscous friction compensation coefficient is derived from the slope of the linear fitting between the friction torque and the speed when the target joint is running at different speeds in uniform motion, with a value range of [0.001 N·m·s / rad, 5 N·m·s / rad]; the static friction compensation coefficient is derived from the torque calculated from the starting current required for the target joint to move from rest to a small displacement, with a value range of [0.01 N·m, 30 N·m].

[0088] S2.6 Calculate the temperature rise attenuation compensation torque.

[0089] Furthermore, based on the motor winding temperature or the reducer housing temperature, the temperature rise attenuation compensation torque is calculated:

[0090] ;

[0091] in, This indicates the torque for compensating for temperature rise decay. This represents the temperature rise compensation coefficient. This indicates the temperature of the motor windings or the temperature of the reducer housing. Indicates reference temperature. This represents the nominal driving torque of the joint.

[0092] It should be noted that the temperature rise attenuation compensation torque is used to compensate for the decrease in actual output torque caused by the increase in motor winding temperature, changes in magnetic flux, and changes in the lubrication state of the reducer; the temperature rise compensation coefficient is derived from the fitting relationship between the servo module output torque attenuation ratio and temperature rise at different temperatures, and the value range is usually [0.0001 / ℃, 0.01 / ℃].

[0093] S2.7 Calculate the gap transition compensation torque.

[0094] Furthermore, based on the comprehensive angular deviation of the servo module drive train, the clearance transition compensation torque is calculated:

[0095] ;

[0096] in, This indicates the clearance transition compensation torque. This represents the stiffness coefficient for transmission backlash compensation. This indicates the overall angular deviation of the servo module drivetrain. This indicates the permissible transmission clearance threshold.

[0097] It should be noted that the clearance transition compensation torque is used to compensate for the output lag caused by the reducer transmission backlash when the target joint reverses or the load direction changes; the allowable transmission clearance threshold is used to determine whether the comprehensive angle deviation exceeds the allowable range of the reducer transmission clearance, which is derived from the reducer backlash test results of the target joint servo module, determined by loading at low speeds in both forward and reverse directions and recording the output lag angle, and the value range is usually [0.0001rad, 0.05rad]; the transmission clearance compensation stiffness coefficient is derived from the calibration curve between the comprehensive angle deviation and the compensation torque during the forward and reverse loading process of the reducer, and the value range is usually [10N·m / rad, 5000N·m / rad].

[0098] S2.8. Establish a reversal prediction window.

[0099] Furthermore, in order to enable clearance transition compensation to intervene in advance before the target joint changes direction, a reversal prediction window is established based on the target joint velocity direction and the target torque direction.

[0100] Let the target joint velocity sent by the upper controller be... The target torque is When satisfied or satisfy When the target joint enters the reversal prediction window, it is determined that the target joint has entered the reversal prediction window.

[0101] When the target joint enters the reversal prediction window, the participation of the clearance transition compensation torque is increased, and the growth rate of the clearance transition compensation torque is limited.

[0102] The rate of change of the clearance transition compensation torque is limited to:

[0103] ;

[0104] in, This indicates the maximum allowable change in transition compensation torque between two adjacent control cycles.

[0105] It should be noted that the reversal prediction window does not compensate only after the transmission clearance deviation has been amplified, but rather triggers clearance transition compensation in advance when the target joint speed direction or target torque direction shows a reversal trend, thereby reducing the reverse impact caused by the reducer transmission idle.

[0106] S2.9 Calculate the elastic hysteresis compensation torque.

[0107] Furthermore, based on the comprehensive angular deviation and the change in comprehensive angular deviation of the servo module drivetrain, the elastic hysteresis compensation torque is calculated:

[0108] ;

[0109] in, This indicates the elastic hysteresis compensation torque. This represents the equivalent torsional stiffness of the transmission chain. This represents the equivalent damping coefficient of the transmission chain. This indicates the overall angle deviation of the current control cycle. This represents the overall angle deviation from the previous control cycle. Indicates the control cycle.

[0110] It should be noted that the elastic hysteresis compensation torque is used to compensate for the elastic torsion and recovery error generated by the reducer, output flange and joint connector after being loaded; the equivalent torsional stiffness of the transmission chain comes from the static loading test in which a known torque is applied to the joint output end and the angle deviation between the motor side and the output end is measured, and the value range is usually [10 N·m / rad, 10000 N·m / rad]; the equivalent damping coefficient of the transmission chain comes from the fitting result between the comprehensive angle deviation recovery speed and the damping torque in the joint loading release test, and the value range is usually [0.01 N·m·s / rad, 100 N·m·s / rad].

[0111] S3. Establish a reversal prediction window based on the target velocity direction and the target torque direction. Determine the action stage based on the foot contact state, trunk posture and joint load state. Combine the left and right symmetrical joint compensation differences and impact contact state to generate the target torque compensation amount after amplitude limitation.

[0112] S3.1 Identify the current motion phase of the target joint.

[0113] Furthermore, based on the plantar contact state, trunk posture changes, target joint movement direction, and target joint load-bearing state, the target joint is divided into a support and load-bearing stage, a swing-following stage, a posture recovery stage, or an external disturbance suppression stage.

[0114] When the foot is in contact and the target joint is subjected to a continuous torque from the weight of the robot body or an external load, the target joint is determined to be in the support and bearing stage.

[0115] When the foot is not in contact and the target joint follows the swing trajectory according to the target speed, the target joint is determined to be in the swing following phase.

[0116] When the robot's torso posture deviates from the preset posture range, and the target joint is used to restore the robot's posture balance, the target joint is determined to be in the posture recovery phase.

[0117] When the target joint is disturbed by external collision, landing impact or contact reaction force, the target joint is determined to be in the external disturbance suppression stage.

[0118] The preset attitude range refers to the allowable deviation range of the torso roll angle, pitch angle and yaw angle obtained by the inertial measurement unit based on the average torso attitude of the humanoid robot in a static upright posture or normal gait stabilization phase. It is derived from the attitude fluctuation statistical boundary when the robot stands, walks and turns without triggering attitude recovery control during calibration.

[0119] It should be noted that the same target joint can be preferentially assigned to one motion phase within a control cycle, or the final motion phase can be determined according to priority rules. The priority rules can be set as follows: external disturbance suppression phase is higher than attitude recovery phase, attitude recovery phase is higher than support and bearing phase, and support and bearing phase is higher than swing following phase.

[0120] S3.2 Determine the participation coefficient of the compensation component based on the action stage.

[0121] Furthermore, let the current motion phase of the target joint be... The participation coefficients of gravity compensation torque, inertia compensation torque, adjacent joint coupling compensation torque, friction compensation torque, temperature rise attenuation compensation torque, clearance transition compensation torque, and elastic backlash compensation torque in the current action phase are determined respectively.

[0122] The target torque compensation amount is: ;

[0123] in, Indicates the target torque compensation amount. Indicates the current movement phase of the target joint. , , , , , , These represent the participation coefficients of gravity compensation torque, inertia compensation torque, adjacent joint coupling compensation torque, friction compensation torque, temperature rise attenuation compensation torque, clearance transition compensation torque, and elastic backlash compensation torque during the current motion phase, respectively, with values ​​ranging from [value range missing]. to .

[0124] It should be noted that the participation coefficients of gravity compensation torque, inertia compensation torque, adjacent joint coupling compensation torque, friction compensation torque, temperature rise attenuation compensation torque, clearance transition compensation torque, and elastic backlash compensation torque in the current action stage are all determined by individually compensating and closing the load-bearing stage, swing following stage, attitude recovery stage, and external disturbance suppression stage. The evaluation indexes are joint position tracking error, velocity tracking error, torque error, trunk attitude offset, and contact impact peak value. The normalized ratio value that minimizes the comprehensive error in the corresponding action stage and does not exceed the joint safety output boundary is selected.

[0125] Furthermore, if the target joint is in the support and bearing stage, the participation coefficients of gravity compensation torque and elastic backlash compensation torque are increased.

[0126] If the target joint is in the swing-following phase, increase the participation coefficients of the inertial compensation torque and the friction compensation torque.

[0127] If the target joint is in the attitude recovery phase, the rate of change of the inertial compensation torque is limited while the gravity compensation torque is retained.

[0128] If the target joint is in the external disturbance suppression stage, the participation coefficients of the coupling compensation torque and elastic backlash compensation torque of adjacent joints are increased.

[0129] If the target joint enters the reversal prediction window, increase the participation coefficient corresponding to the clearance transition compensation torque. This allows the gap transition compensation torque to intervene in advance before the target joint changes direction.

[0130] S3.3, Perform left and right symmetrical joint difference compensation.

[0131] Furthermore, for the left and right symmetrical joints of the humanoid robot, the target torque compensation amount of the symmetrical joints corresponding to the left and right sides of the target joint is obtained.

[0132] Let the target torque compensation amount of the left joint be... The target torque compensation amount of the right joint is The difference in compensation between the left and right symmetrical joints is as follows:

[0133] ;

[0134] in, This indicates the difference in compensation between the left and right symmetrical joints. This indicates the target torque compensation amount for the left joint. This indicates the target torque compensation amount of the right joint.

[0135] When satisfied Furthermore, when the left and right joints are in the same movement phase, the rate of change of the target torque compensation amount on the side with the larger compensation amount is limited, or the target torque compensation amount on the side with the smaller compensation amount is appropriately enhanced.

[0136] in, This indicates the threshold for allowable compensation differences in symmetrical joints.

[0137] Specifically, using the excess difference As an adjustment, when the target torque compensation on the left is greater than that on the right, the increment of the target torque compensation on the left within adjacent control cycles is limited to no more than 30% to 80% of the preset maximum torque change, or the target torque compensation on the right is increased along its original compensation direction. ,in Take a value between 0.1 and 0.5. When the target torque compensation on the right side is greater than that on the left side, reverse the same rule. The adjusted target torque compensation on both sides must not exceed the safety torque margin of the corresponding joint.

[0138] It should be noted that the allowable compensation difference threshold for the left and right symmetrical joints is used to determine whether the target torque compensation amount of the left and right symmetrical joints is too different. It is derived from the statistical upper limit of the compensation difference obtained when the left and right symmetrical joints are calibrated for normal gait, swing following, posture recovery and support bearing under the same action stage. The value can be set to the 95th percentile of the compensation difference or 5% to 20% of the maximum allowable output torque of the target joint servo module, and the smaller value of the two is taken.

[0139] For example, when a humanoid robot is in the two-legged support phase, both the left and right knee joints are in the support and bearing phase. If the target torque compensation amount of the left knee joint is significantly greater than that of the right knee joint, then the rate of change of the target torque compensation amount of the left knee joint is limited to avoid the robot's torso shifting to one side due to inconsistent outputs from the left and right knee joints.

[0140] It should be noted that symmetrical joints can include the left and right hip joints, the left and right knee joints, the left and right ankle joints, the left and right shoulder joints, the left and right elbow joints, and the left and right wrist joints.

[0141] S3.4 Identify the impact contact state.

[0142] Furthermore, the target joint is judged to be in an impact contact state based on the target torque change rate, the plantar contact state, and the comprehensive angle deviation change.

[0143] The rate of change of the target torque is:

[0144] ;

[0145] in, Indicates the rate of change of the target torque. Indicates the first The target torque issued by the upper controller within each control cycle This indicates the target torque issued by the host controller in the previous control cycle.

[0146] When satisfied And the state of contact with the sole of the foot changes, or the overall angle deviation meets the requirements. At that time, it is determined that the target joint is in an impact contact state.

[0147] in, This indicates the threshold for determining impact contact. This represents the threshold for changes in overall angular deviation.

[0148] It should be noted that the impact contact determination threshold is used to determine whether the target joint is in an impact contact state caused by landing, touching the ground, or external collision. It is derived from the distribution boundary of the target torque change rate in normal swinging, normal support, and landing impact experiments of the humanoid robot, and its value range is typically [0.05]. N·m / s, 0.50 [N·m / s], where, This represents the maximum allowable output torque of the target joint servo module; the comprehensive angle deviation change threshold is used to help determine whether the target joint has experienced impact contact or a sudden change in the transmission chain. It is derived from the statistical upper limit of the comprehensive angle deviation change of the target joint under normal tracking conditions, and the value range is usually [0.0005rad, 0.05rad].

[0149] For example, when a humanoid robot's feet switch from being off the ground to being in contact with the ground during walking, and the rate of change of the target torque of the ankle or knee joint exceeds the impact contact determination threshold, the corresponding joint is determined to be in an impact contact state.

[0150] S3.5 Adjust the participation coefficient of the compensation component according to the impact contact state.

[0151] Furthermore, if the target joint is in an impact contact state, the participation coefficients of the inertial compensation torque and the clearance transition compensation torque are reduced, while the gravity compensation torque and the elastic backlash compensation torque are retained.

[0152] It should be noted that reducing the participation coefficient of inertial compensation torque and clearance transition compensation torque can prevent excessive joint rigidity caused by the continued amplification of compensation torque during landing, ground contact, or external collision; retaining gravity compensation torque and elastic backlash compensation torque can maintain the basic load-bearing capacity and contact compliance of the target joint.

[0153] S3.6. Set safety boundary limits for the target torque compensation amount.

[0154] Furthermore, to ensure safe joint output, torque boundary limits are imposed on the target torque compensation amount:

[0155] ;

[0156] in, This represents the target torque compensation amount after amplitude limiting. This indicates the maximum permissible output torque of the target joint servo module.

[0157] Furthermore, the rate of change of the target torque compensation is restricted:

[0158] ;

[0159] in, This indicates the maximum allowable torque change between two adjacent control cycles.

[0160] It should be noted that by limiting the torque boundary and the rate of change, sudden torque changes in the target joint can be avoided during reversal, ground contact, external disturbances, or compensation for differences between left and right symmetrical joints.

[0161] S4. The target torque compensation amount after the limit is superimposed with the target torque to generate the compensated target torque, which is then converted into the target motor current and the current loop control is executed by the servo driver.

[0162] S4.1 Generate the target torque after compensation.

[0163] Furthermore, the target torque compensation amount after amplitude limiting is superimposed with the target torque sent by the upper controller to generate the compensated target torque:

[0164] ;

[0165] in, This represents the target torque after compensation. This indicates the target torque issued by the upper-level controller. This indicates the target torque compensation amount after amplitude limiting.

[0166] S4.2 Calculate the target current of the motor based on the compensated target torque.

[0167] Furthermore, based on the compensated target torque, motor torque constant, reducer transmission ratio, and reducer transmission efficiency, the target motor current is calculated:

[0168] ;

[0169] in, Indicates the target current of the motor. This represents the motor torque constant. Indicates the gear ratio of the reducer. This indicates the transmission efficiency of the speed reducer.

[0170] S4.3 Limit the target current of the motor.

[0171] Furthermore, when the target motor current exceeds the servo driver's allowable output current, the target motor current is limited.

[0172] ;

[0173] in, This represents the target motor current after limiting. This indicates the maximum current that the servo driver is allowed to output.

[0174] It should be noted that the motor target current limiting process is used to prevent the target torque after compensation from being too large, which could lead to overcurrent protection of the servo driver or overheating of the motor windings.

[0175] S4.4 Execute current loop closed-loop control.

[0176] Furthermore, the servo driver performs current loop control based on the limited target motor current, causing the motor to output the corresponding compensated driving torque to the joint output terminal via the reducer.

[0177] During the current loop control process, the servo driver collects the motor phase current in real time and compares the actual motor phase current with the limited target motor current. Based on the deviation between the two, the drive voltage is adjusted so that the actual motor phase current follows the limited target motor current.

[0178] S4.5 Execute abnormal protection control.

[0179] Furthermore, when overcurrent, overtemperature, encoder malfunction, bus voltage malfunction, joint reverse impact, or torque error exceeding the safety threshold is detected, the target joint will be switched to torque holding mode or unloading protection mode.

[0180] Among them, the torque limiting and holding mode refers to limiting the output torque of the target joint within a preset safe torque range to maintain the current posture of the humanoid robot; the unloading protection mode refers to gradually reducing the output torque of the target joint so that the target joint transitions from a high-load output state to a safe unloading state.

[0181] When the actual position error, velocity error and torque error of the target joint are all within the preset allowable range, the current compensated target torque output is maintained, thereby completing the real-time torque compensation control of the target joint servo module.

[0182] In this embodiment, Figure 5 The results of the comparison of dynamic tracking errors of the knee joint are shown.

[0183] Depend on Figure 5 It is evident that during continuous gait movements and joint speed changes, the absolute position tracking error under traditional servo control fluctuates significantly, with obvious local peaks, indicating that it is insufficient in compensating for factors such as gravity, inertia, friction, and transmission chain lag during support load, swing following, and posture adjustment.

[0184] By adopting this technical solution, the joint motion state quantities are constructed by collecting the encoder angle on the motor side, the joint output end angle, the motor phase current, the temperature state, the torso posture and the foot contact state. Based on the movement stage, gravity compensation torque, inertia compensation torque, friction compensation torque, temperature rise attenuation compensation torque and elastic backlash compensation torque are comprehensively introduced to keep the knee joint at a low error level during dynamic tracking.

[0185] The results show that the proposed technical solution can improve the position tracking accuracy of the joint output end, reduce the error accumulation and fluctuation amplitude during joint movement, thereby improving the stability and control consistency of the lower limb joint movement of the humanoid robot.

[0186] In this embodiment, Figure 6 The results show a comparison of the overall angular deviation of the transmission chain under commutation and impact conditions.

[0187] Depend on Figure 6 It is evident that when joint reversal, foot contact, or external disturbances occur, the overall angular deviation of the transmission chain under traditional servo control shows a significant sudden increase, indicating that the reducer transmission clearance, output flange elastic deformation, and joint connection clearance can easily cause output lag and reverse impact.

[0188] By adopting this technical solution, a reversal prediction window is established based on the target velocity direction and the target torque direction. The gap transition compensation torque and elastic backlash compensation torque are calculated in combination with the comprehensive angle deviation, so that the compensation effect can intervene in advance before the deviation amplifies. At the same time, the participation coefficient of the compensation component is adjusted and the torque amplitude and rate of change are limited under the impact contact state to avoid sudden changes in the compensation torque.

[0189] The results show that the proposed technical solution can effectively suppress the transmission chain angle deviation caused by commutation backlash and impact contact, reduce joint reverse impact, and improve the compliance, safety and dynamic response stability of the servo module under complex working conditions.

[0190] In summary, this invention improves torque tracking and position control accuracy by constructing a multi-dimensional compensation architecture to systematically compensate for nonlinear factors in the transmission chain; it achieves adaptive matching by identifying the action stage and dynamically adjusting the compensation coefficient to avoid overcompensation or undercompensation; it actively compensates for gaps and softens transient responses by establishing a commutation prediction and impact recognition mechanism to reduce impact and hysteresis; and it ensures smooth torque output and safe operation of the entire machine by limiting the compensation amount and monitoring left-right symmetry differences.

[0191] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A torque compensation control method for a humanoid robot joint servo module, characterized in that, include: Collect the encoder angle on the motor side of the target joint, the joint output angle, the motor phase current, the temperature status, the torso posture, the foot contact status, the target speed and the target torque, calculate the actual speed of the joint, the actual acceleration and the comprehensive angle deviation of the transmission chain, and construct the joint motion state variables; Calculate the gravity compensation torque, inertia compensation torque, adjacent joint coupling compensation torque, friction compensation torque, temperature rise attenuation compensation torque, clearance transition compensation torque, and elastic hysteresis compensation torque based on the joint motion state quantities. A reversal prediction window is established based on the target velocity direction and the target torque direction. The movement stage is determined based on the foot contact state, torso posture, and joint load state. Combined with the compensation differences of the left and right symmetrical joints and the impact contact state, the target torque compensation amount after amplitude limiting is generated. This includes determining the participation coefficient of each of the aforementioned compensation torques based on the action phase; increasing the participation coefficient of the clearance transition compensation torque when the target joint enters the reversal prediction window; and limiting the rate of change of the clearance transition compensation torque so that the clearance transition compensation torque intervenes in advance before the target joint reversal. When the target joint is in an impact contact state, reduce the participation coefficient of inertial compensation torque and clearance transition compensation torque, while retaining gravity compensation torque and elastic backlash compensation torque; The target torque compensation amount is calculated by summing the products of each compensation torque and its corresponding parameter coefficient. When the difference in compensation between the left and right symmetrical joints exceeds the threshold for the difference in compensation between the left and right symmetrical joints, and the left and right joints are in the same movement stage, the rate of change of the target torque compensation amount on the side with the larger compensation amount is limited, or the target torque compensation amount on the side with the smaller compensation amount is enhanced. Based on the target torque compensation amount after correction of the difference in compensation between the left and right symmetrical joints, safety boundary limits and rate of change limits are applied to generate the target torque compensation amount after amplitude limitation. The target torque compensation amount after limiting is superimposed with the target torque to generate the compensated target torque, which is then converted into the target motor current and controlled by the servo driver using the current loop.

2. The torque compensation control method for the joint servo module of a humanoid robot as described in claim 1, characterized in that, The data collected from the target joint includes the following: encoder angle on the motor side, joint output angle, motor phase current, temperature status, torso posture, foot contact status, target speed, and target torque. Within each servo control cycle, acquire the motor-side encoder angle and the joint output angle of the target joint; Obtain motor phase current, bus voltage, motor winding temperature, and reducer housing temperature; Acquire the robot's torso posture and foot contact status; Receive target joint position, target velocity, and target torque from the upper controller; The motor-side encoder angle, joint output angle, motor phase current, temperature status, torso posture, foot contact status, target speed, and target torque are used as the real-time operating data of the target joint servo module.

3. The torque compensation control method for a humanoid robot joint servo module as described in claim 1 or 2, characterized in that, The calculation of the actual joint velocity, actual acceleration, and overall angular deviation of the transmission chain includes: Calculate the angle from the motor side encoder to the joint output end based on the motor side encoder angle and the reducer transmission ratio. Calculate the actual speed of the joint based on the joint output angle of the current control cycle and the joint output angle of the previous control cycle. Calculate the actual joint acceleration based on the actual joint velocity in the current control cycle and the actual joint velocity in the previous control cycle. The overall angle deviation of the transmission chain is generated based on the difference between the calculated angle and the angle at the joint output end.

4. The torque compensation control method for the joint servo module of a humanoid robot as described in claim 1, characterized in that, The calculation of gravity compensation torque, inertia compensation torque, and adjacent joint coupling compensation torque includes: The gravity compensation torque is calculated based on the equivalent mass of the limb segment driven by the target joint, the equivalent distance from the center of mass to the center of rotation of the target joint, and the angle of the joint output end. Calculate the inertia compensation torque based on the equivalent moment of inertia of the target joint referred to the output end and the actual acceleration of the joint; Calculate the coupling compensation torque of adjacent joints based on the actual velocities of adjacent joints that have kinematic coupling with the target joint, the actual velocity of the target joint, and the coupling coefficient of adjacent joints to the target joint. Based on the gravity compensation torque, inertia compensation torque, and adjacent joint coupling compensation torque, the nominal driving torque of the joint is generated.

5. The torque compensation control method for the joint servo module of a humanoid robot as described in claim 1, characterized in that, The calculation of the friction compensation torque, temperature rise attenuation compensation torque, clearance transition compensation torque, and elastic hysteresis compensation torque includes: Calculate the friction compensation torque based on the actual joint speed, Coulomb friction compensation coefficient, viscous friction compensation coefficient, static friction compensation coefficient, and low-speed friction smoothing speed threshold. Calculate the temperature rise attenuation compensation torque based on the motor winding temperature or reducer housing temperature, reference temperature, temperature rise compensation coefficient, and nominal driving torque of the joint. Calculate the clearance transition compensation torque based on the comprehensive angular deviation of the transmission chain, the allowable transmission clearance threshold, and the transmission clearance compensation stiffness coefficient; The elastic backlash compensation torque is calculated based on the comprehensive angle deviation of the transmission chain in the current control cycle, the comprehensive angle deviation of the transmission chain in the previous control cycle, the equivalent torsional stiffness of the transmission chain, and the equivalent damping coefficient of the transmission chain.

6. The torque compensation control method for the joint servo module of a humanoid robot as described in claim 1, characterized in that, The step of establishing a reversal prediction window based on the target velocity direction and the target torque direction includes: Read the target speed of the current control cycle and the target speed of the previous control cycle, and determine whether the target speed direction has reversed. Read the target torque of the current control cycle and the target torque of the previous control cycle, and determine whether the direction of the target torque has reversed. When the target velocity direction is reversed or the target torque direction is reversed, the target joint is determined to enter the reversal prediction window.

7. The torque compensation control method for a humanoid robot joint servo module as described in claim 6, characterized in that, The process of determining the action phase based on foot contact state, trunk posture, and joint load-bearing state includes: When the foot is in contact and the target joint is subjected to a continuous load moment, the target joint is defined as the support and load-bearing stage. When the foot is not in contact and the target joint follows the swing trajectory according to the target speed, the target joint is determined to be in the swing following phase. When the trunk posture deviates from the preset posture range and the target joint is used to restore the robot's posture balance, the target joint is identified as the posture recovery stage. When the target joint is disturbed by external collision, landing impact or contact reaction force, the target joint is identified as the external disturbance suppression stage.

8. The torque compensation control method for the joint servo module of a humanoid robot as described in claim 1, characterized in that, The difference in compensation between left and right symmetrical joints was calculated as follows: Obtain the target torque compensation amount of the left and right symmetrical joints corresponding to the target joint; Calculate the difference in compensation between the left and right symmetrical joints between the target torque compensation of the left joint and the target torque compensation of the right joint; The bilaterally symmetrical joints include the left and right hip joints, the left and right knee joints, the left and right ankle joints, the left and right shoulder joints, the left and right elbow joints, or the left and right wrist joints.

9. The torque compensation control method for a humanoid robot joint servo module as described in claim 8, characterized in that, The impact contact state is determined in the following way: Calculate the rate of change of the target torque based on the target torque of the current control cycle and the target torque of the previous control cycle; Calculate the change in comprehensive angle deviation based on the comprehensive angle deviation of the transmission chain in the current control cycle and the comprehensive angle deviation of the transmission chain in the previous control cycle. When the rate of change of the target torque exceeds the impact contact determination threshold, and the foot contact state changes, or the change in the comprehensive angle deviation exceeds the comprehensive angle deviation change threshold, the target joint is determined to be in an impact contact state.

10. The torque compensation control method for a humanoid robot joint servo module as described in claim 1, characterized in that, The step of superimposing the limited target torque compensation amount with the target torque to generate the compensated target torque, converting it into the motor target current, and then having the servo driver perform current loop control includes: The target torque compensation amount after amplitude limiting is superimposed with the target torque sent by the upper controller to generate the compensated target torque; Calculate the target motor current based on the compensated target torque, motor torque constant, reducer transmission ratio, and reducer transmission efficiency; When the target current of the motor exceeds the allowable output current of the servo driver, the target current of the motor is limited. The servo driver performs current loop control based on the limited target motor current, so that the motor outputs the corresponding compensated driving torque to the joint output terminal through the reducer; When overcurrent, overtemperature, encoder malfunction, bus voltage malfunction, joint reverse impact, or torque error exceeding the safety threshold is detected, the target joint will be switched to torque holding mode or unloading protection mode.

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