A robot compliant constant force polishing method and system based on admittance control

Abstract

This application relates to the field of robotic automated grinding technology, and provides a compliant constant-force grinding method and system based on admittance control. The method continuously acquires raw signals from the six-dimensional force sensor output by the robot's end effector throughout the grinding operation, simultaneously obtaining the real-time pose information of the robot's end effector, and extracting the actual external contact force acting on the robot's end effector. The admittance controller maps the actual external contact force into position and velocity correction values ​​for the robot's end effector. The method continuously and iteratively performs the acquisition and calibration processing of the raw signals and real-time pose information, the mapping of position and velocity correction values, and the adjustment of the preset grinding motion trajectory, ensuring that the contact force between the robot's end effector and the workpiece remains at a preset constant value, thus completing the compliant constant-force grinding operation. This method achieves accurate acquisition of the actual external contact force of the robot's end effector, providing a reliable data foundation for subsequent force control.

Description

Technical Field

[0001] This application relates to the field of robotic automated polishing technology, and in particular to a robotic compliant constant force polishing method and system based on admittance control. Background Technology

[0002] Current robotic grinding operations generally employ a pure position control mode, which cannot dynamically adjust the force based on the actual contact state of the workpiece surface, easily leading to over- or under-grinding. Some grinding methods using force feedback suffer from insufficient sensor data accuracy; sensor zero-point drift and end-effector load gravity can severely interfere with contact force measurement results. Furthermore, existing admittance control schemes often only correct the robot's end-effector position without synchronously adjusting the speed. This can easily cause severe force oscillations at the moment of robot-workpiece contact, making it impossible to maintain a constant contact force throughout the grinding process and failing to meet the requirements of high-precision, high-consistency grinding processes. Summary of the Invention

[0003] This application provides a robotic compliant constant force grinding method and system based on admittance control, which aims to solve the problem that existing technologies cannot meet the requirements of high-precision and high-consistency grinding processes.

[0004] In a first aspect, embodiments of this application provide a robotic compliant constant-force grinding method based on admittance control, the method comprising: Throughout the grinding process, the raw signals output by the six-dimensional force sensor at the end of the robot are continuously collected, and the real-time pose information of the robot end is obtained simultaneously. The collected raw signals are calibrated to remove zero-point drift values. Combined with the real-time pose information, the gravity component generated by the end load is calculated and eliminated, and the real external contact force on the end of the robot is extracted. The real external contact force is input in real time into the admittance controller built based on the mass damping spring model. The admittance controller maps the real external contact force into the position correction and velocity correction of the robot end effector. The robot's preset grinding motion trajectory is adjusted according to the position correction, and the robot end effector running speed is adjusted according to the velocity correction. The robot continuously and cyclically performs the acquisition and calibration processing of the original signal and real-time pose information, the mapping of position correction and speed correction, and the adjustment of the preset grinding motion trajectory, so that the contact force between the robot end and the workpiece being ground is always maintained at a preset constant value, thus completing the compliant constant force grinding operation.

[0005] In some embodiments, the step of continuously acquiring the raw signal output by the six-dimensional force sensor at the robot end of the grinding operation and simultaneously acquiring the real-time pose information of the robot end includes: fixing the six-dimensional force sensor at the robot end, completing the initial zero-point calibration of the six-dimensional force sensor before the grinding operation starts, acquiring the raw force signal and raw torque signal output by the six-dimensional force sensor at a fixed sampling frequency throughout the grinding operation, and simultaneously reading the real-time position information and real-time attitude information of the robot end from the robot control system.

[0006] In some embodiments, the calibration process performed on the acquired raw signal to remove zero-point drift values, the calculation and elimination of the gravity component generated by the end-effector load in combination with real-time pose information, and the extraction of the actual external contact force on the robot end-effector include: calculating the zero-point drift value of the six-dimensional force sensor based on the initial zero-point calibration result; calculating the gravity component value generated by the end-effector load in the six-dimensional force sensor coordinate system based on the real-time position information and real-time attitude information of the robot end-effector; and subtracting the corresponding zero-point drift value and gravity component value from the acquired raw force signal and raw torque signal, respectively, to obtain the actual external contact force value on the robot end-effector.

[0007] In some embodiments, the step of inputting the real external contact force into an admittance controller constructed based on a mass-damped spring model in real time, and mapping the real external contact force into position and velocity corrections for the robot end effector through the admittance controller, includes: pre-setting virtual mass parameters, virtual damping parameters, and virtual stiffness parameters corresponding to the admittance controller; inputting the real external contact force value into the admittance controller; and having the admittance controller perform calculations based on the equivalent model of the mass-damped spring to obtain the position and velocity correction values ​​of the robot end effector in three orthogonal directions.

[0008] In some embodiments, adjusting the robot's preset grinding motion trajectory according to the position correction amount includes: obtaining the end position coordinates of the robot's pre-planned grinding motion trajectory at each moment, superimposing the position correction values ​​in three orthogonal directions onto the end position coordinates at the corresponding moments to generate the adjusted grinding motion trajectory, and sending the adjusted grinding motion trajectory to the robot control system.

[0009] In some embodiments, adjusting the robot end effector speed according to the speed correction amount includes: while generating the adjusted grinding motion trajectory, superimposing the speed correction values ​​in three orthogonal directions onto the preset running speed value of the robot end effector at the corresponding moment to generate the adjusted end effector running speed value, and sending the adjusted end effector running speed value to the robot control system.

[0010] In some embodiments, the continuous cyclic execution of acquiring and calibrating the original signal and real-time pose information, mapping the position correction amount and velocity correction amount, and adjusting the preset grinding motion trajectory, so that the contact force between the robot end effector and the workpiece being ground is always maintained at a preset constant value, and the compliant constant force grinding operation is completed, includes: performing signal acquisition, data processing, correction amount mapping and trajectory speed adjustment operations in a fixed cycle throughout the grinding operation; maintaining the preset grinding motion trajectory when the robot end effector is not in contact with the workpiece being ground; dynamically adjusting the end effector motion state to suppress contact force oscillation during the process of the robot end effector contacting the workpiece being ground; and stably outputting the preset constant contact force after the robot end effector fully contacts the workpiece being ground.

[0011] In some embodiments, the method further includes: pre-storing preset constant contact force values ​​and admittance controller parameter combinations corresponding to various different workpiece materials being ground; identifying the material type of the current workpiece being ground before the grinding operation starts; and automatically matching and loading the corresponding preset constant contact force values ​​and admittance controller parameter combinations according to the identified material type.

[0012] In some embodiments, the method further includes: determining in real time whether the actual external contact force value exceeds a preset safety threshold range during the grinding operation; if the actual external contact force value exceeds the preset safety threshold range, immediately sending a stop command to the robot control system and generating grinding abnormality alarm information.

[0013] Secondly, this application provides a robotic compliant constant force polishing system based on admittance control, the system comprising: The signal acquisition unit is used to continuously acquire the raw signals output by the six-dimensional force sensor at the end of the robot throughout the grinding operation, and simultaneously acquire the real-time pose information of the robot end. The acquired raw signals are calibrated to remove zero-point drift values, and the gravity component generated by the end load is calculated and eliminated in combination with the real-time pose information to extract the real external contact force on the robot end. The speed adjustment unit is used to input the real external contact force into the admittance controller based on the mass damping spring model in real time. The admittance controller maps the real external contact force into the position correction and speed correction of the robot end effector. The robot's preset grinding motion trajectory is adjusted according to the position correction, and the robot end effector running speed is adjusted according to the speed correction. The grinding completion unit is used to continuously and cyclically perform the acquisition and calibration processing of the original signal and real-time pose information, the mapping of position correction and speed correction, and the adjustment of the preset grinding motion trajectory, so that the contact force between the robot end and the workpiece being ground is always maintained at a preset constant value, thus completing the compliant constant force grinding operation.

[0014] This application combines six-dimensional force sensor calibration with real-time gravity compensation to effectively eliminate the interference of zero-point drift and load gravity on the force signal, thereby achieving accurate acquisition of the real external contact force at the robot end and providing a reliable data foundation for subsequent force control.

[0015] An admittance controller is constructed based on a mass damping spring model, which simultaneously maps the contact force into position correction and velocity correction, enabling real-time coupling adjustment of the contact force with the robot's motion trajectory and running speed, thus significantly improving the response speed and stability of force control.

[0016] By adopting a closed-loop cyclic control mechanism, dynamic adaptive adjustment is achieved in the three stages of robot-workpiece non-contact, contact process, and complete contact. This effectively suppresses force oscillation at the moment of contact, ensures that the contact force is always maintained at a preset constant value throughout the grinding process, significantly improves the uniformity and consistency of the grinding surface, and reduces the workpiece scrap rate.

[0017] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

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

[0019] Figure 1 This is a schematic flowchart illustrating the steps of a robot compliant constant force grinding method based on admittance control according to an embodiment of this application; Figure 2 This is a schematic diagram illustrating the principle of a robot compliant constant force grinding method based on admittance control according to an embodiment of this application; Figure 3 This is a schematic block diagram of a robotic compliant constant force grinding system based on admittance control, provided in one embodiment of this application. Figure 4 This is a schematic block diagram of the structure of a computer device provided in an embodiment of this application.

[0020] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] The flowchart shown in the attached diagram is for illustrative purposes only and does not necessarily include all content and operations / steps, nor does it necessarily have to be performed in the order described. For example, some operations / steps can be broken down, combined, or partially merged, so the actual execution order may change depending on the actual situation.

[0023] It should be understood that, in order to clearly describe the technical solutions of the embodiments of the present invention, the terms "first" and "second" are used in the embodiments of the present invention to distinguish identical or similar items with essentially the same function and effect. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and the terms "first" and "second" are not necessarily different.

[0024] It should be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0025] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0026] Current robotic grinding operations generally employ a pure position control mode, which cannot dynamically adjust the force based on the actual contact state of the workpiece surface, easily leading to over- or under-grinding. Some grinding methods using force feedback suffer from insufficient sensor data accuracy; sensor zero-point drift and end-effector load gravity can severely interfere with contact force measurement results. Furthermore, existing admittance control schemes often only correct the robot's end-effector position without synchronously adjusting the speed. This can easily cause severe force oscillations at the moment of robot-workpiece contact, making it impossible to maintain a constant contact force throughout the grinding process and failing to meet the requirements of high-precision, high-consistency grinding processes.

[0027] Please refer to Figure 1 and Figure 2This invention provides a robotic compliant constant-force grinding method based on admittance control, applied to computer equipment. The computer equipment can be deployed on a single server or server cluster, or in a handheld terminal, laptop, wearable device, or robot control cabinet. It should be specifically noted that all data collection and processing operations involved in this application are conducted with the full authorization of the relevant users and in strict compliance with relevant data security laws and regulations, and will not infringe upon the personal privacy or legitimate rights of any user.

[0028] like Figure 1 As shown, the overall process of the robot compliant constant force grinding method based on admittance control provided in this embodiment of the invention includes steps S101 to S103. Figure 2 As shown, the system architecture for implementing this method includes a six-axis industrial robot, a six-dimensional force sensor mounted at the robot's end effector, a grinding wheel fixed to the end effector of the six-dimensional force sensor, a workpiece to be ground placed on the worktable, and a robot control cabinet. The six-dimensional force sensor and the robot control cabinet are connected via an industrial bus for real-time force signal transmission; the robot control cabinet and the six-axis industrial robot are connected via power cables and control cables for transmitting motion control commands and driving the robot to perform grinding actions.

[0029] The provided robotic compliant constant force grinding method based on admittance control includes steps S101 to S103. Details are as follows: Step S101. Throughout the grinding operation, the raw signals output by the six-dimensional force sensor at the end of the robot are continuously collected, and the real-time pose information of the robot end is obtained synchronously. The collected raw signals are calibrated to remove zero-point drift values. The gravity component generated by the end load is calculated and eliminated in combination with the real-time pose information, and the real external contact force on the robot end is extracted.

[0030] Specifically, step S101 is the real external contact force extraction step. Its core purpose is to eliminate the interference of sensor error and load gravity, obtain the pure contact force between the robot end and the workpiece, and provide accurate input data for subsequent force control.

[0031] The data processing module in the robot control cabinet is responsible for executing this step. Before starting the grinding operation, the physical installation and electrical connection of the six-dimensional force sensor must be completed, ensuring that the sensor is coaxially fixed to the robot's end effector flange and that the grinding tool is securely connected to the sensor output. After the grinding operation starts, the data processing module first activates the signal acquisition thread to continuously receive the raw signals output by the six-dimensional force sensor, while simultaneously acquiring the real-time pose information of the robot's end effector through the robot's internal communication interface.

[0032] After receiving the raw signal, the data processing module first performs calibration processing, subtracting the pre-stored sensor zero-point drift value from the raw signal to eliminate inherent errors caused by temperature changes, circuit drift, and other factors after the sensor is powered on. Subsequently, based on the synchronously acquired real-time pose information of the robot's end effector and combined with the pre-input mass and center-of-gravity parameters of the end effector load (including the six-dimensional force sensor, grinding tool, and connectors), the data processing module calculates the gravity component value generated by the end effector load in the six-dimensional force sensor coordinate system under the current pose through robot kinematic coordinate transformation. Finally, the data processing module further subtracts the gravity component value from the signal after zero-point drift subtraction, ultimately extracting the actual external contact force experienced by the robot's end effector solely by contact with the workpiece.

[0033] Step S102. Input the real external contact force into the admittance controller built based on the mass damping spring model in real time. The admittance controller maps the real external contact force into the position correction amount and velocity correction amount of the robot end effector. Adjust the robot's preset grinding motion trajectory according to the position correction amount, and adjust the robot end effector running speed according to the velocity correction amount.

[0034] Specifically, step S102 is the admittance control and motion correction step, the core purpose of which is to convert the real external contact force into the motion adjustment amount of the robot end effector, so as to realize the real-time coupling and adjustment of force and motion.

[0035] The admittance control module in the robot control cabinet is the main execution unit for this step. The admittance control module is pre-built based on an equivalent model of a mass-damped spring. Its core logic is to simulate the interaction between the robot's end effector and the environment as a spring-damped system with virtual mass, virtual damping, and virtual stiffness. When a real external contact force is input into the admittance control module, the module performs dynamic calculations based on preset virtual parameters, converting the force deviation into motion parameters that the robot's end effector needs to adjust.

[0036] Unlike existing technologies that only perform position correction, this step generates both position correction and velocity correction values ​​simultaneously. The position correction value compensates for trajectory deviations caused by workpiece surface errors and installation errors, ensuring the grinding tool maintains the correct contact depth with the workpiece surface. The velocity correction value adjusts the speed of the robot's end effector, suppressing the impact force generated by inertia at the moment of contact. After generating the correction values, the admittance control module sends them to the motion control module. The motion control module adjusts the pre-planned grinding trajectory based on the position correction value and simultaneously adjusts the robot's end effector speed based on the velocity correction value, generating the final motion control command and sending it to the robot body.

[0037] Step S103. Continuously cycle through the acquisition and calibration of the original signal and real-time pose information, the mapping of position correction and speed correction, and the adjustment of the preset grinding motion trajectory, so that the contact force between the robot end and the workpiece being ground is always maintained at a preset constant value, thus completing the compliant constant force grinding operation.

[0038] Specifically, step S103 is a closed-loop constant force control step. Its core purpose is to ensure that the contact force is always maintained at a preset constant value throughout the grinding process through continuous closed-loop feedback adjustment, so as to achieve a uniform grinding effect.

[0039] The main entity executing this step is the loop control module in the robot control cabinet. The loop control module runs continuously with a fixed control cycle, performing signal acquisition, data processing, correction mapping, and trajectory speed adjustment operations sequentially within each control cycle, forming a complete closed-loop control circuit.

[0040] Based on the contact state between the robot's end effector and the workpiece, this step divides the grinding process into three stages for differentiated control: The first stage is the non-contact stage, where the actual external contact force is zero, and the loop control module controls the robot to run at a constant speed along the preset grinding trajectory; the second stage is the contact process stage, where the robot's end effector has just made contact with the workpiece, and the contact force will oscillate violently due to inertia. The loop control module will dynamically adjust the virtual damping parameters of the admittance controller to increase the system damping and quickly attenuate the oscillation; the third stage is the complete contact stage, where the force oscillation has ended, and the loop control module maintains normal admittance control parameters and stabilizes the contact force at a preset constant value through continuous closed-loop adjustment until the grinding operation of the entire workpiece is completed.

[0041] In some embodiments, the step of continuously acquiring the raw signal output by the six-dimensional force sensor at the robot end of the grinding operation and simultaneously acquiring the real-time pose information of the robot end includes: fixing the six-dimensional force sensor at the robot end, completing the initial zero-point calibration of the six-dimensional force sensor before the grinding operation starts, acquiring the raw force signal and raw torque signal output by the six-dimensional force sensor at a fixed sampling frequency throughout the grinding operation, and simultaneously reading the real-time position information and real-time attitude information of the robot end from the robot control system.

[0042] This embodiment further refines the process of acquiring the original signal and pose information in step S101.

[0043] A six-dimensional force sensor is fixedly installed at the robot's end effector, ensuring that the sensor's coordinate system coincides with the coordinate system of the robot's end effector flange. Before starting the grinding operation, the robot is moved to an unloaded, stationary state. The robot is controlled to remain in multiple different poses for a preset time, and the output data of the six-dimensional force sensor in each pose is collected. The collected data sets are averaged to calculate the zero-point drift value of the six-dimensional force sensor, which is then stored in the non-volatile memory of the robot control cabinet.

[0044] After the grinding operation begins, the data processing module acquires the raw force and torque signals output by the six-dimensional force sensor at a fixed sampling frequency between 100 Hz and 1000 Hz. The raw force signal contains force components in three orthogonal directions, and the raw torque signal contains torque components in three orthogonal directions. Simultaneously, the data processing module reads the real-time position and attitude information of the robot's end effector at the same frequency as the signal acquisition via the robot control system's real-time data interface. The real-time position information is the robot's end effector's three-dimensional coordinates in the Cartesian coordinate system, and the real-time attitude information is the robot's end effector's Euler angle parameters in the Cartesian coordinate system.

[0045] In some embodiments, the calibration process performed on the acquired raw signal to remove zero-point drift values, the calculation and elimination of the gravity component generated by the end-effector load in combination with real-time pose information, and the extraction of the actual external contact force on the robot end-effector include: calculating the zero-point drift value of the six-dimensional force sensor based on the initial zero-point calibration result; calculating the gravity component value generated by the end-effector load in the six-dimensional force sensor coordinate system based on the real-time position information and real-time attitude information of the robot end-effector; and subtracting the corresponding zero-point drift value and gravity component value from the acquired raw force signal and raw torque signal, respectively, to obtain the actual external contact force value on the robot end-effector.

[0046] This embodiment further refines the extraction process of the actual external contact force in step S101.

[0047] The data processing module reads the pre-calculated zero-point drift value of the six-dimensional force sensor from the non-volatile memory of the robot control cabinet, subtracts the corresponding zero-point drift value from each component of the acquired original force signal, and subtracts the corresponding zero-point drift value from each component of the original torque signal to obtain the force signal and torque signal after deducting the zero-point drift.

[0048] The data processing module calculates the gravity vector of the end-effector load in the current pose by using the real-time position and attitude information of the robot end-effector, combined with the pre-input total mass of the end-effector load and the coordinate parameters of the center of gravity in the robot end-effector flange coordinate system through homogeneous coordinate transformation. Then, the gravity vector is converted into gravity component values ​​in the six-dimensional force sensor coordinate system, including gravity force components in three orthogonal directions and gravity torque components in three orthogonal directions.

[0049] Finally, the data processing module subtracts the corresponding gravity force component value from each component of the force signal after deducting zero-point drift, and subtracts the corresponding gravity torque component value from each component of the torque signal after deducting zero-point drift, to obtain the actual external contact force value of the robot end effector, including the actual contact force components in three orthogonal directions and the actual contact torque components in three orthogonal directions.

[0050] In some embodiments, the step of inputting the real external contact force into an admittance controller constructed based on a mass-damped spring model in real time, and mapping the real external contact force into position and velocity corrections for the robot end effector through the admittance controller, includes: pre-setting virtual mass parameters, virtual damping parameters, and virtual stiffness parameters corresponding to the admittance controller; inputting the real external contact force value into the admittance controller; and having the admittance controller perform calculations based on the equivalent model of the mass-damped spring to obtain the position and velocity correction values ​​of the robot end effector in three orthogonal directions.

[0051] This embodiment further refines the process of the admittance controller generating the correction value in step S102.

[0052] Before starting the grinding operation, the operator pre-sets the virtual mass parameter, virtual damping parameter, and virtual stiffness parameter corresponding to the admittance controller according to the grinding process requirements. Among them, the virtual mass parameter is used to adjust the system's response inertia; the larger the value, the smoother the system response but the slower the response speed. The virtual damping parameter is used to adjust the system's oscillation suppression capability; the larger the value, the faster the oscillation decays but the system stiffness will decrease. The virtual stiffness parameter is used to adjust the system's position holding capability; the larger the value, the smaller the position deviation but the lower the force compliance.

[0053] After receiving the actual external contact force value, the admittance control module compares it with the preset desired contact force value to calculate the contact force deviation. Based on the dynamic logic of the equivalent model of a mass-damped spring, and combined with preset virtual mass parameters, virtual damping parameters, and virtual stiffness parameters, the admittance control module calculates the contact force deviation value. First, it obtains the acceleration value that the robot's end effector needs to adjust. Then, it performs a first integration on the acceleration value to obtain the velocity correction value, and a second integration on the velocity correction value to obtain the position correction value. Finally, the admittance control module outputs the position correction value and velocity correction value of the robot's end effector in three orthogonal directions.

[0054] In some embodiments, adjusting the robot's preset grinding motion trajectory according to the position correction amount includes: obtaining the end position coordinates of the robot's pre-planned grinding motion trajectory at each moment, superimposing the position correction values ​​in three orthogonal directions onto the end position coordinates at the corresponding moments to generate the adjusted grinding motion trajectory, and sending the adjusted grinding motion trajectory to the robot control system.

[0055] This embodiment further refines the process of adjusting the grinding motion trajectory in step S102.

[0056] The motion control module obtains the pre-planned grinding motion trajectory from the trajectory storage unit of the robot control cabinet. The grinding motion trajectory consists of a series of discrete trajectory points, each of which contains a corresponding timestamp and the three-dimensional position coordinates of the robot end effector in the Cartesian coordinate system.

[0057] The motion control module superimposes the position correction values ​​in the three orthogonal directions output by the admittance control module onto the position coordinates of the trajectory point in the three orthogonal directions corresponding to the current control cycle, generating the adjusted trajectory point position coordinates. The motion control module performs this superposition operation sequentially for the trajectory points of each control cycle, generating a complete adjusted grinding motion trajectory. Finally, the motion control module sends the adjusted grinding motion trajectory to the robot's servo drive system via the industrial bus, driving the robot to run according to the adjusted trajectory.

[0058] In some embodiments, adjusting the robot end effector speed according to the speed correction amount includes: while generating the adjusted grinding motion trajectory, superimposing the speed correction values ​​in three orthogonal directions onto the preset running speed value of the robot end effector at the corresponding moment to generate the adjusted end effector running speed value, and sending the adjusted end effector running speed value to the robot control system.

[0059] This embodiment further refines the process of adjusting the robot end effector speed in step S102.

[0060] While acquiring the pre-planned grinding motion trajectory, the motion control module also acquires the preset running speed value of the robot end effector corresponding to each trajectory point. The preset running speed value is the linear velocity component of the robot end effector in three orthogonal directions in the Cartesian coordinate system.

[0061] Within the same control cycle of generating the adjusted grinding trajectory, the motion control module superimposes the velocity correction values ​​in the three orthogonal directions output by the admittance control module onto the preset running velocity values ​​in the three orthogonal directions corresponding to the current trajectory point, generating the adjusted end-effector running velocity value. The motion control module then binds the adjusted end-effector running velocity value with the adjusted trajectory point position coordinates to form a complete motion control command. Finally, the motion control module synchronously sends the motion control command, containing position and velocity information, to the robot's servo drive system, ensuring that the robot's end-effector position and velocity are adjusted synchronously.

[0062] In some embodiments, the continuous cyclic execution of acquiring and calibrating the original signal and real-time pose information, mapping the position correction amount and velocity correction amount, and adjusting the preset grinding motion trajectory, so that the contact force between the robot end effector and the workpiece being ground is always maintained at a preset constant value, and the compliant constant force grinding operation is completed, includes: performing signal acquisition, data processing, correction amount mapping and trajectory speed adjustment operations in a fixed cycle throughout the grinding operation; maintaining the preset grinding motion trajectory when the robot end effector is not in contact with the workpiece being ground; dynamically adjusting the end effector motion state to suppress contact force oscillation during the process of the robot end effector contacting the workpiece being ground; and stably outputting the preset constant contact force after the robot end effector fully contacts the workpiece being ground.

[0063] This embodiment further refines the process of cyclic constant force control in step S103.

[0064] The cyclic control module is set to a fixed control cycle that is the same as the signal acquisition frequency. In each control cycle, it sequentially performs signal acquisition, data processing, correction mapping, and trajectory speed adjustment operations to form a closed-loop control circuit.

[0065] The loop control module monitors the actual external contact force value in real time and determines the contact state between the robot end effector and the workpiece based on the contact force value: when the actual external contact force value is less than the preset contact threshold, it is determined to be in the non-contact stage, and the loop control module controls the robot to run at a constant speed according to the preset grinding motion trajectory and preset running speed; when the actual external contact force value rises rapidly from less than the contact threshold to greater than the contact threshold, it is determined to be in the contact process stage, and the loop control module increases the virtual damping parameter of the admittance controller to the preset high damping value to quickly suppress the force oscillation generated at the moment of contact; when the actual external contact force value stabilizes within the preset fluctuation range of the preset constant contact force value, it is determined to be in the complete contact stage, and the loop control module restores the virtual damping parameter of the admittance controller to the normal value, and maintains the contact force at the preset constant value through continuous closed-loop adjustment until the grinding operation is completed.

[0066] In some embodiments, the method further includes: pre-storing preset constant contact force values ​​and admittance controller parameter combinations corresponding to various different workpiece materials being ground; identifying the material type of the current workpiece being ground before the grinding operation starts; and automatically matching and loading the corresponding preset constant contact force values ​​and admittance controller parameter combinations according to the identified material type.

[0067] This embodiment provides an adaptive parameter matching method based on workpiece material as a supplement to steps S101 to S103.

[0068] Before the grinding operation starts, the operator conducts experiments to obtain the optimal preset constant contact force value and admittance controller parameter combination for various different workpiece materials. The above parameter combination is stored in the parameter database of the robot control cabinet, and each parameter combination corresponds to a unique material identifier.

[0069] When the grinding operation starts, the system obtains the material type of the workpiece being ground by inputting the workpiece number, scanning a QR code, or using machine vision recognition. Based on the material identifier corresponding to the material type, the system retrieves the corresponding preset constant contact force value and admittance controller parameter combination from the parameter database. The system automatically loads the retrieved parameters into the admittance control module and the cycle control module, eliminating the need for manual parameter input by the operator and achieving automatic matching of grinding parameters for workpieces of different materials.

[0070] In some embodiments, the method further includes: determining in real time whether the actual external contact force value exceeds a preset safety threshold range during the grinding operation; if the actual external contact force value exceeds the preset safety threshold range, immediately sending a stop command to the robot control system and generating grinding abnormality alarm information.

[0071] This embodiment provides a safety protection method for the grinding process, as a supplement to steps S101 to S103.

[0072] Before the grinding operation starts, the operator presets the contact force safety threshold range according to the grinding process requirements. The safety threshold range includes an upper threshold and a lower threshold. The upper threshold is set to 120% of the preset constant contact force value, and the lower threshold is set to 80% of the preset constant contact force value.

[0073] During the grinding operation, the cycle control module compares the actual external contact force value with the preset safety threshold range in real time. If the actual external contact force value is greater than the upper threshold, it is determined that an excessive force collision or workpiece loosening has occurred; if the actual external contact force value is less than the lower threshold, it is determined that the grinding tool is over-worn or the workpiece has fallen off. When any of the above abnormalities are detected, the cycle control module immediately sends an emergency stop command to the robot's servo drive system, controlling the robot to stop all movement. At the same time, it triggers the light and sound alarm device and generates grinding abnormality alarm information on the human-machine interface of the robot control cabinet, recording the time of the abnormality, the type of abnormality, and the corresponding contact force value, which facilitates the operator's troubleshooting.

[0074] In some embodiments, existing grinding methods do not take into account the continuous wear of grinding tools during operation. Tool wear will cause the actual contact depth between the end effector and the workpiece to gradually decrease, which in turn will cause the contact force to continuously decay, ultimately resulting in defects such as insufficient grinding and poor surface uniformity. Traditional stop measurement compensation methods will significantly reduce production efficiency.

[0075] By establishing a model in advance through calibration experiments to establish the correspondence between the wear of the grinding tool and the cumulative grinding time and the average contact force attenuation, the cumulative grinding time and the average contact force attenuation are calculated in real time during the grinding operation. Based on the above model, the current tool wear is estimated online, and the wear is converted into the corresponding position compensation amount and superimposed on the position correction amount output by the admittance controller to achieve real-time automatic compensation for tool wear.

[0076] For example, before starting the grinding operation, the operator conducts a calibration experiment using a brand-new grinding tool, setting multiple sets of different preset constant contact force values ​​and grinding feed speeds. Under each set of parameters, a standard test block is continuously ground, and the actual wear of the grinding tool is measured at fixed time intervals, while the average contact force value at the corresponding moment is recorded. The experimental data is fitted using the least squares method to establish a binary linear regression model between the wear of the grinding tool and the cumulative grinding time and the average contact force attenuation. The model parameters are stored in the non-volatile memory of the robot control cabinet.

[0077] After the grinding operation starts, the system starts a timer to record the cumulative grinding time, and simultaneously calculates the average actual external contact force within the most recent preset time window in each control cycle. The system substitutes the cumulative grinding time and average contact force attenuation into a pre-established binary linear regression model to calculate the cumulative wear of the grinding tool. The system converts the cumulative wear value into a position compensation value for the robot end effector in the grinding contact direction, and adds this position compensation value to the corresponding position correction value output by the admittance controller to generate the final position correction value. The motion control module adjusts the grinding trajectory according to the final position correction value to compensate for the loss of contact depth caused by tool wear, ensuring that the actual contact force remains at a preset constant value throughout the grinding process.

[0078] When the cumulative wear of the grinding tool reaches the preset maximum allowable wear, the system generates a tool replacement prompt message to remind the operator to replace the grinding tool. After replacement, the system automatically resets the cumulative grinding time and cumulative wear value, and restarts the wear compensation calculation.

[0079] In some embodiments, existing admittance control methods mostly perform overall force control in the Cartesian coordinate system. During the grinding process of complex curved surfaces, the frictional force generated by the tangential motion will seriously interfere with the measurement and control of the normal contact force, resulting in large fluctuations in the normal force and making it impossible to ensure that the grinding depth at each position of the complex curved surface is uniform.

[0080] By pre-planning the grinding trajectory based on the 3D model of the workpiece to be ground and calculating the surface normal vector corresponding to each trajectory point, the surface normal vector corresponding to the current position of the robot end is obtained in real time during the grinding operation. A local task coordinate system that dynamically changes with the contact point is established. The real external contact force collected by the six-dimensional force sensor is decomposed into the normal and two orthogonal tangential directions of the local task coordinate system. Admittance control is performed only on the normal force component to generate the normal position correction, and position control is performed on the two tangential components to maintain the preset trajectory accuracy, thereby achieving decoupled control of normal force and tangential position.

[0081] For example, before the grinding operation starts, the operator imports a 3D model of the workpiece to be ground, plans a complete grinding motion trajectory based on the 3D model, and generates a series of discrete trajectory points. For each trajectory point, the operator calculates the surface normal vector and two orthogonal tangent vectors of that point in the workpiece coordinate system, and stores the trajectory point coordinates, normal vector, and tangent vector information in the trajectory storage unit of the robot control cabinet.

[0082] After the grinding operation starts, the motion control module executes each trajectory point sequentially according to a preset order. Within each control cycle, the system matches the corresponding trajectory point based on the current position of the robot's end effector, obtains the surface normal vector and tangent vector information corresponding to the trajectory point, and converts the surface normal vector and tangent vector into vectors in the robot's base coordinate system through coordinate transformation, thus constructing a local task coordinate system with the contact point as the origin, the normal vector as the Z-axis, and the two tangent vectors as the X-axis and Y-axis.

[0083] The data processing module converts the extracted actual external contact force values ​​into force components in the local task coordinate system using a rotation matrix, resulting in a normal force component and two tangential force components. The admittance control module compares only the normal force component with the preset desired normal contact force value, calculates the normal force deviation, and generates a normal position correction in the local task coordinate system based on a mass-damped spring model. The motion control module converts the normal position correction into a position correction in the robot's base coordinate system and superimposes it onto the position coordinates of the current trajectory point to generate an adjusted trajectory point. For the two tangential directions, the motion control module maintains the preset trajectory point coordinates unchanged and controls the robot's end effector to move tangentially only according to the preset feed rate.

[0084] When the robot end effector moves to the next trajectory point, the system automatically updates the local task coordinate system and repeats the above force decomposition and control process to ensure that the normal contact force is always maintained at a preset constant value and the tangential trajectory accuracy meets the process requirements throughout the entire process of grinding complex curved surfaces.

[0085] In some embodiments, for large and complex workpieces, the working range and load capacity of a single robot cannot meet the grinding requirements. When multiple robots work together to grind, it is difficult to guarantee the motion synchronization and force control consistency between the robots, which can easily lead to grinding overlap or omissions.

[0086] By constructing a master-slave dual-robot collaborative control architecture, the master robot is responsible for clamping the workpiece to be polished and performing high-precision position control, driving the workpiece to move according to the preset trajectory; the slave robot is responsible for carrying the polishing tool and performing admittance constant force control, dynamically adjusting its own polishing trajectory and contact force according to the real-time pose information sent by the master robot, so as to realize the motion synchronization and force control collaboration of the master and slave robots.

[0087] For example, before starting the grinding operation, the base coordinate systems of the master robot and the slave robot are calibrated, and the transformation relationship between the master robot's base coordinate system and the slave robot's base coordinate system is established. The workpiece to be ground is fixedly mounted on the end effector of the master robot, and the grinding tool and the six-dimensional force sensor are mounted on the end effector of the slave robot. The operator plans the workpiece motion trajectory of the master robot and the relative trajectory of the grinding tool of the slave robot based on the 3D model of the workpiece, and stores the two trajectories in the master robot control cabinet.

[0088] After the grinding operation starts, the main robot moves according to the preset workpiece motion trajectory, and at the same time sends the real-time pose information of the main robot end effector to the slave robot control cabinet at fixed intervals via industrial Ethernet. After receiving the real-time pose information of the main robot, the slave robot control cabinet calculates the desired position and orientation of the grinding tool relative to the workpiece at the current moment by combining it with the pre-established coordinate system transformation relationship.

[0089] The robot performs constant force grinding control according to the method described in steps S101 to S103: the original signal is collected from the six-dimensional force sensor at the end of the robot, and the real external contact force is extracted after calibration and gravity compensation; the real external contact force is input into the admittance controller to generate position correction and speed correction; the preset relative trajectory of the robot is adjusted according to the position correction and speed correction to keep the contact force between the grinding tool and the workpiece at a preset constant value.

[0090] During the polishing process, the master robot and the slave robot maintain real-time communication. The master robot dynamically adjusts its movement speed based on the contact force feedback from the slave robot. When the contact force fluctuates significantly, the movement speed is appropriately reduced to ensure a stable polishing process. The polishing operation ends once the master robot completes the entire workpiece movement trajectory.

[0091] In some embodiments, during high-speed grinding operations, the high-speed rotation of the grinding tool and the flexibility of the robot structure will generate high-frequency vibrations, resulting in a large amount of vibration noise in the signal collected by the six-dimensional force sensor. This causes fluctuations in the correction amount output by the admittance controller, ultimately causing vibration marks on the grinding surface and severely affecting the surface quality.

[0092] By establishing a vibration dynamics model of the robot end-effector grinding system, an extended Kalman filter observer is designed to collect real external contact force and robot end-effector motion state information in real time during the grinding operation. The force disturbance component caused by vibration is estimated by the extended Kalman filter observer, and the vibration disturbance component is converted into the corresponding velocity compensation quantity and superimposed on the velocity correction quantity output by the admittance controller to actively counteract the influence of vibration on the contact force.

[0093] For example, before the grinding operation starts, the mass, damping, and stiffness parameters of the robot's end-effector grinding system are obtained through a system identification experiment, and a second-order linear vibration dynamics model including vibration modes is established. Based on this model, an extended Kalman filter observer is designed, the observer's state vector, observation equation, and noise covariance matrix are determined, and the observer parameters are stored in the robot control cabinet.

[0094] After the grinding operation starts, within each control cycle, the data processing module extracts the actual external contact force value and simultaneously obtains the real-time position and velocity information of the robot's end effector from the robot control system. The extended Kalman filter observer uses the actual external contact force value as the observation input and the real-time position and velocity information of the robot's end effector as the state input to perform filtering calculations and estimate the force disturbance component value caused by vibration at the current moment, including force disturbance and torque disturbance in three orthogonal directions.

[0095] After the admittance control module generates the position and velocity correction values, the system converts the estimated force disturbance component values ​​into corresponding velocity compensation values. The conversion relationship is obtained through pre-calibration, i.e., the velocity compensation value corresponding to a unit force disturbance. The system then adds the velocity compensation value to the corresponding direction velocity correction value output by the admittance controller to generate the final velocity correction value.

[0096] The motion control module adjusts the robot's trajectory and speed based on the final position and velocity corrections, actively counteracting contact force fluctuations caused by vibrations and making the actual contact force more stable. Experiments show that using the method in this embodiment, the fluctuation amplitude of the contact force can be reduced by more than 60%, effectively eliminating vibration marks on the polished surface.

[0097] In some embodiments, existing admittance control methods often employ fixed virtual mass, damping, and stiffness parameters, which cannot adapt to changes in workpiece surface stiffness or grinding tool wear during the grinding process. When the working conditions change, the response speed and stability of force control will decrease significantly.

[0098] By designing a dual-input single-output fuzzy controller, the contact force error and the rate of change of the contact force error are used as the inputs of the fuzzy controller, and the adjustment of the virtual damping parameters and virtual stiffness parameters of the admittance controller are used as the outputs of the fuzzy controller. During the grinding operation, the admittance parameters are adjusted online according to the real-time contact force state, so that the control system always maintains the optimal dynamic and steady-state performance.

[0099] For example, before starting the grinding operation, the operator sets the initial virtual mass parameter, initial virtual damping parameter, and initial virtual stiffness parameter of the admittance controller according to the grinding process requirements. The input and output universes of discourse of the fuzzy controller are designed, dividing the contact force error into seven fuzzy subsets: negative large, negative medium, negative small, zero, positive small, positive medium, and positive large. The rate of change of the contact force error is also divided into seven fuzzy subsets: negative large, negative medium, negative small, zero, positive small, positive medium, and positive large. The adjustment amounts of the virtual damping parameter and the virtual stiffness parameter are also divided into seven fuzzy subsets: negative large, negative medium, negative small, zero, positive small, positive medium, and positive large.

[0100] Fuzzy control rules were formulated based on expert experience, following these principles: when the contact force error is large and its rate of change is large, the virtual damping parameter is increased to suppress overshoot; when the contact force error is small and its rate of change is small, the virtual damping parameter is decreased to improve response speed; when the steady-state contact force error is large, the virtual stiffness parameter is increased to reduce steady-state error. The fuzzy control rules were optimized through offline simulation, generating a fuzzy control lookup table which was then stored in the robot control cabinet.

[0101] After the grinding operation starts, the system calculates the contact force error and the rate of change of contact force error at the current moment within each control cycle. The contact force error and the rate of change of error are then fuzzified to obtain the corresponding fuzzy subsets. The fuzzy values ​​of the virtual damping parameter adjustment and the virtual stiffness parameter adjustment are retrieved from the fuzzy control lookup table, and then defuzzified using the center-of-gravity method to obtain the precise adjustment values.

[0102] The system superimposes the virtual damping parameter adjustment onto the initial virtual damping parameter to obtain the actual virtual damping parameter at the current moment; similarly, it superimposes the virtual stiffness parameter adjustment onto the initial virtual stiffness parameter to obtain the actual virtual stiffness parameter at the current moment. The admittance control module uses the updated virtual damping and virtual stiffness parameters to perform calculations, generating position and velocity corrections. Through this online adjustment process, the admittance controller can adapt to different grinding conditions and maintain excellent force control performance at all times.

[0103] In some embodiments, existing admittance control methods mostly only control the position of the robot end effector, ignoring the influence of torque on the grinding posture. When the workpiece surface is tilted or uneven, an additional torque will be generated between the grinding tool and the workpiece, causing the grinding tool and the workpiece surface to not maintain perpendicular contact, which in turn causes problems such as uneven grinding depth and inconsistent edge chamfering.

[0104] By expanding the control dimensions of the admittance controller, a six-degree-of-freedom attitude admittance model is established. The real external contact force and torque collected by the six-dimensional force sensor are simultaneously input into the admittance controller. The force component is mapped to the position correction quantity, and the torque component is mapped to the attitude correction quantity. This enables synchronous and compliant adjustment of the robot end position and attitude, ensuring that the grinding tool always maintains perpendicular contact with the workpiece surface.

[0105] For example, before starting the grinding operation, the operator pre-sets the virtual parameters for position control (virtual mass, virtual damping, virtual stiffness) and attitude control (virtual moment of inertia, virtual rotational damping, virtual rotational stiffness) of the admittance controller. The attitude admittance model and the position admittance model use the same mass damping spring structure, simulating the relationship between torque and attitude angle deviation as a moment of inertia-rotational damping-rotational spring system.

[0106] After the grinding operation begins, the data processing module extracts the actual external contact force values, which include three orthogonal force components and three orthogonal moment components. The admittance control module inputs the three force components into the position admittance model to generate position corrections in three orthogonal directions; it inputs the three moment components into the attitude admittance model to generate attitude angle corrections in three orthogonal directions, including roll angle corrections around the X-axis, pitch angle corrections around the Y-axis, and yaw angle corrections around the Z-axis.

[0107] The motion control module adds the position correction to the position coordinates of the current trajectory point to generate the adjusted position coordinates; it also adds the attitude angle correction to the attitude angle of the current trajectory point to generate the adjusted attitude angle. The motion control module combines the adjusted position coordinates and attitude angles into a complete robot end-effector pose command, which is then sent to the robot's servo drive system to drive the robot to adjust both the end-effector position and attitude simultaneously.

[0108] Through the aforementioned attitude-force coordinated control, when an additional torque is generated between the grinding tool and the workpiece surface, the robot automatically adjusts its end effector attitude to ensure that the axis of the grinding tool remains aligned with the normal vector of the workpiece surface, thus guaranteeing a constant grinding contact area and uniform grinding depth. This embodiment is particularly suitable for grinding workpieces with complex curved surfaces, chamfers, and edge features.

[0109] Please see Figure 3 As shown, Figure 3 This is a schematic diagram of the structure of a robotic compliant constant-force polishing system 200 based on admittance control, provided in an embodiment of this application. The robotic compliant constant-force polishing system 200 based on admittance control is used to execute the steps of the robotic compliant constant-force polishing method based on admittance control shown in the above embodiments. The robotic compliant constant-force polishing system 200 based on admittance control can be a single server or a server cluster, or it can be a terminal, such as a handheld terminal, a laptop computer, a wearable device, or a robot.

[0110] like Figure 3 As shown, the robotic compliant constant force grinding system 200 based on admittance control includes: The signal acquisition unit 201 is used to continuously acquire the raw signals output by the six-dimensional force sensor at the end of the robot during the entire grinding operation, and simultaneously acquire the real-time pose information of the robot end; perform calibration processing on the acquired raw signals to remove zero-point drift values, calculate and eliminate the gravity component generated by the end load in combination with the real-time pose information, and extract the real external contact force on the robot end. The speed adjustment unit 202 is used to input the real external contact force into the admittance controller based on the mass damping spring model in real time. The admittance controller maps the real external contact force into the position correction amount and speed correction amount of the robot end effector. The robot's preset grinding motion trajectory is adjusted according to the position correction amount, and the robot end effector running speed is adjusted according to the speed correction amount. The grinding completion unit 203 is used to continuously and cyclically perform the acquisition and calibration processing of the original signal and real-time pose information, the mapping of position correction amount and speed correction amount, and the adjustment of the preset grinding motion trajectory, so that the contact force between the robot end and the workpiece being ground is always maintained at a preset constant value, thus completing the compliant constant force grinding operation.

[0111] In some embodiments, the step of continuously acquiring the raw signal output by the six-dimensional force sensor at the robot end of the grinding operation and simultaneously acquiring the real-time pose information of the robot end includes: fixing the six-dimensional force sensor at the robot end, completing the initial zero-point calibration of the six-dimensional force sensor before the grinding operation starts, acquiring the raw force signal and raw torque signal output by the six-dimensional force sensor at a fixed sampling frequency throughout the grinding operation, and simultaneously reading the real-time position information and real-time attitude information of the robot end from the robot control system.

[0112] In some embodiments, the calibration process performed on the acquired raw signal to remove zero-point drift values, the calculation and elimination of the gravity component generated by the end-effector load in combination with real-time pose information, and the extraction of the actual external contact force on the robot end-effector include: calculating the zero-point drift value of the six-dimensional force sensor based on the initial zero-point calibration result; calculating the gravity component value generated by the end-effector load in the six-dimensional force sensor coordinate system based on the real-time position information and real-time attitude information of the robot end-effector; and subtracting the corresponding zero-point drift value and gravity component value from the acquired raw force signal and raw torque signal, respectively, to obtain the actual external contact force value on the robot end-effector.

[0113] In some embodiments, the step of inputting the real external contact force into an admittance controller constructed based on a mass-damped spring model in real time, and mapping the real external contact force into position and velocity corrections for the robot end effector through the admittance controller, includes: pre-setting virtual mass parameters, virtual damping parameters, and virtual stiffness parameters corresponding to the admittance controller; inputting the real external contact force value into the admittance controller; and having the admittance controller perform calculations based on the equivalent model of the mass-damped spring to obtain the position and velocity correction values ​​of the robot end effector in three orthogonal directions.

[0114] In some embodiments, adjusting the robot's preset grinding motion trajectory according to the position correction amount includes: obtaining the end position coordinates of the robot's pre-planned grinding motion trajectory at each moment, superimposing the position correction values ​​in three orthogonal directions onto the end position coordinates at the corresponding moments to generate the adjusted grinding motion trajectory, and sending the adjusted grinding motion trajectory to the robot control system.

[0115] In some embodiments, adjusting the robot end effector speed according to the speed correction amount includes: while generating the adjusted grinding motion trajectory, superimposing the speed correction values ​​in three orthogonal directions onto the preset running speed value of the robot end effector at the corresponding moment to generate the adjusted end effector running speed value, and sending the adjusted end effector running speed value to the robot control system.

[0116] In some embodiments, the continuous cyclic execution of acquiring and calibrating the original signal and real-time pose information, mapping the position correction amount and velocity correction amount, and adjusting the preset grinding motion trajectory, so that the contact force between the robot end effector and the workpiece being ground is always maintained at a preset constant value, and the compliant constant force grinding operation is completed, includes: performing signal acquisition, data processing, correction amount mapping and trajectory speed adjustment operations in a fixed cycle throughout the grinding operation; maintaining the preset grinding motion trajectory when the robot end effector is not in contact with the workpiece being ground; dynamically adjusting the end effector motion state to suppress contact force oscillation during the process of the robot end effector contacting the workpiece being ground; and stably outputting the preset constant contact force after the robot end effector fully contacts the workpiece being ground.

[0117] In some embodiments, the method further includes: pre-storing preset constant contact force values ​​and admittance controller parameter combinations corresponding to various different workpiece materials being ground; identifying the material type of the current workpiece being ground before the grinding operation starts; and automatically matching and loading the corresponding preset constant contact force values ​​and admittance controller parameter combinations according to the identified material type.

[0118] In some embodiments, the method further includes: determining in real time whether the actual external contact force value exceeds a preset safety threshold range during the grinding operation; if the actual external contact force value exceeds the preset safety threshold range, immediately sending a stop command to the robot control system and generating grinding abnormality alarm information.

[0119] It should be noted that those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process of the admittance-controlled robotic compliant constant force polishing system and its modules described above can be found in the corresponding contents of the various embodiments of the admittance-controlled robotic compliant constant force polishing method, and will not be repeated here.

[0120] The aforementioned robotic compliant constant force grinding method based on admittance control can be implemented as a computer program, which can be used in, for example... Figure 3 It runs on the system shown.

[0121] Please see Figure 4 , Figure 4 This is a schematic block diagram of the structure of a computer device provided in an embodiment of this application. The computer device includes a processor, a memory, and a network interface connected via a device bus, wherein the memory may include a storage medium and internal memory.

[0122] The storage medium can store operating devices and computer programs. The computer program includes program instructions that, when executed, cause the processor to perform any admittance-based robotic compliant constant-force grinding method.

[0123] The processor provides computing and control capabilities, supporting the operation of the entire computer device.

[0124] The internal memory provides an environment for the execution of computer programs in non-volatile storage media. When the computer program is executed by the processor, it enables the processor to perform any robotic compliant constant force grinding method based on admittance control.

[0125] This network interface is used for network communication, such as sending assigned tasks. Those skilled in the art will understand that... Figure 4 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the terminal to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0126] It should be understood that the processor can be a Central Processing Unit (CPU), but it can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Among these, a general-purpose processor can be a microprocessor or any conventional processor.

[0127] In one embodiment, the processor is configured to run a computer program stored in memory to perform the following steps: Throughout the grinding process, the raw signals output by the six-dimensional force sensor at the end of the robot are continuously collected, and the real-time pose information of the robot end is obtained simultaneously. The collected raw signals are calibrated to remove zero-point drift values. Combined with the real-time pose information, the gravity component generated by the end load is calculated and eliminated, and the real external contact force on the end of the robot is extracted. The real external contact force is input in real time into the admittance controller built based on the mass damping spring model. The admittance controller maps the real external contact force into the position correction and velocity correction of the robot end effector. The robot's preset grinding motion trajectory is adjusted according to the position correction, and the robot end effector running speed is adjusted according to the velocity correction. The robot continuously and cyclically performs the acquisition and calibration processing of the original signal and real-time pose information, the mapping of position correction and speed correction, and the adjustment of the preset grinding motion trajectory, so that the contact force between the robot end and the workpiece being ground is always maintained at a preset constant value, thus completing the compliant constant force grinding operation.

[0128] In some embodiments, the step of continuously acquiring the raw signal output by the six-dimensional force sensor at the robot end of the grinding operation and simultaneously acquiring the real-time pose information of the robot end includes: fixing the six-dimensional force sensor at the robot end, completing the initial zero-point calibration of the six-dimensional force sensor before the grinding operation starts, acquiring the raw force signal and raw torque signal output by the six-dimensional force sensor at a fixed sampling frequency throughout the grinding operation, and simultaneously reading the real-time position information and real-time attitude information of the robot end from the robot control system.

[0129] In some embodiments, the calibration process performed on the acquired raw signal to remove zero-point drift values, the calculation and elimination of the gravity component generated by the end-effector load in combination with real-time pose information, and the extraction of the actual external contact force on the robot end-effector include: calculating the zero-point drift value of the six-dimensional force sensor based on the initial zero-point calibration result; calculating the gravity component value generated by the end-effector load in the six-dimensional force sensor coordinate system based on the real-time position information and real-time attitude information of the robot end-effector; and subtracting the corresponding zero-point drift value and gravity component value from the acquired raw force signal and raw torque signal, respectively, to obtain the actual external contact force value on the robot end-effector.

[0130] In some embodiments, the step of inputting the real external contact force into an admittance controller constructed based on a mass-damped spring model in real time, and mapping the real external contact force into position and velocity corrections for the robot end effector through the admittance controller, includes: pre-setting virtual mass parameters, virtual damping parameters, and virtual stiffness parameters corresponding to the admittance controller; inputting the real external contact force value into the admittance controller; and having the admittance controller perform calculations based on the equivalent model of the mass-damped spring to obtain the position and velocity correction values ​​of the robot end effector in three orthogonal directions.

[0131] In some embodiments, adjusting the robot's preset grinding motion trajectory according to the position correction amount includes: obtaining the end position coordinates of the robot's pre-planned grinding motion trajectory at each moment, superimposing the position correction values ​​in three orthogonal directions onto the end position coordinates at the corresponding moments to generate the adjusted grinding motion trajectory, and sending the adjusted grinding motion trajectory to the robot control system.

[0132] In some embodiments, adjusting the robot end effector speed according to the speed correction amount includes: while generating the adjusted grinding motion trajectory, superimposing the speed correction values ​​in three orthogonal directions onto the preset running speed value of the robot end effector at the corresponding moment to generate the adjusted end effector running speed value, and sending the adjusted end effector running speed value to the robot control system.

[0133] In some embodiments, the continuous cyclic execution of acquiring and calibrating the original signal and real-time pose information, mapping the position correction amount and velocity correction amount, and adjusting the preset grinding motion trajectory, so that the contact force between the robot end effector and the workpiece being ground is always maintained at a preset constant value, and the compliant constant force grinding operation is completed, includes: performing signal acquisition, data processing, correction amount mapping and trajectory speed adjustment operations in a fixed cycle throughout the grinding operation; maintaining the preset grinding motion trajectory when the robot end effector is not in contact with the workpiece being ground; dynamically adjusting the end effector motion state to suppress contact force oscillation during the process of the robot end effector contacting the workpiece being ground; and stably outputting the preset constant contact force after the robot end effector fully contacts the workpiece being ground.

[0134] In some embodiments, the method further includes: pre-storing preset constant contact force values ​​and admittance controller parameter combinations corresponding to various different workpiece materials being ground; identifying the material type of the current workpiece being ground before the grinding operation starts; and automatically matching and loading the corresponding preset constant contact force values ​​and admittance controller parameter combinations according to the identified material type.

[0135] In some embodiments, the method further includes: determining in real time whether the actual external contact force value exceeds a preset safety threshold range during the grinding operation; if the actual external contact force value exceeds the preset safety threshold range, immediately sending a stop command to the robot control system and generating grinding abnormality alarm information.

[0136] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, causes the processor to perform the steps of the robotic compliant constant force polishing method based on admittance control as provided in any embodiment of this application.

[0137] The computer-readable storage medium may be an internal storage unit of the computer device described in the foregoing embodiments, such as the hard disk or memory of the computer device. The computer-readable storage medium may also be an external storage device of the computer device, such as a plug-in hard disk, SmartMedia Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the computer device.

[0138] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A robotic compliant constant force grinding method based on admittance control, characterized in that, include: Throughout the grinding process, the raw signals output by the six-dimensional force sensor at the end of the robot are continuously collected, and the real-time pose information of the robot end is obtained simultaneously. The acquired raw signals are calibrated to remove zero-point drift values. Combined with real-time pose information, the gravity component generated by the end-effector load is calculated and eliminated to extract the real external contact force on the robot end-effector. The real external contact force is input in real time into the admittance controller built based on the mass damping spring model. The admittance controller maps the real external contact force into the position correction and velocity correction of the robot end effector. The robot's preset grinding motion trajectory is adjusted according to the position correction, and the robot end effector running speed is adjusted according to the velocity correction. The robot continuously and cyclically performs the acquisition and calibration processing of the original signal and real-time pose information, the mapping of position correction and speed correction, and the adjustment of the preset grinding motion trajectory, so that the contact force between the robot end and the workpiece being ground is always maintained at a preset constant value, thus completing the compliant constant force grinding operation.

2. The method according to claim 1, characterized in that, The process of continuously collecting raw signals from the six-dimensional force sensor at the robot's end effector throughout the grinding operation, and simultaneously acquiring the robot's real-time pose information, includes: A six-dimensional force sensor is fixedly installed at the end of the robot. The initial zero-point calibration of the six-dimensional force sensor is completed before the grinding operation starts. During the entire grinding operation, the original force signal and original torque signal output by the six-dimensional force sensor are collected at a fixed sampling frequency. The real-time position information and real-time attitude information of the robot end are read from the robot control system at the same time.

3. The method according to claim 1, characterized in that, The process of calibrating the acquired raw signals to remove zero-point drift values, calculating and eliminating the gravity component generated by the end-effector load in conjunction with real-time pose information, and extracting the actual external contact force experienced by the robot end effector includes: The zero-point drift value of the six-dimensional force sensor is calculated based on the initial zero-point calibration results. The gravity component value generated by the end-effector load in the six-dimensional force sensor coordinate system is calculated based on the real-time position and attitude information of the robot end-effector. The corresponding zero-point drift value and gravity component value are subtracted from the acquired original force signal and original torque signal, respectively, to obtain the actual external contact force value of the robot end-effector.

4. The method according to claim 1, characterized in that, The process of inputting the real external contact force into an admittance controller based on a mass-damped spring model in real time, and mapping the real external contact force into position and velocity corrections for the robot end effector, includes: The virtual mass parameters, virtual damping parameters, and virtual stiffness parameters corresponding to the admittance controller are preset. The actual external contact force values ​​are input into the admittance controller. The admittance controller performs calculations based on the equivalent model of the mass damping spring to obtain the position correction and velocity correction values ​​of the robot end effector in three orthogonal directions.

5. The method according to claim 1, characterized in that, The step of adjusting the robot's preset grinding motion trajectory according to the position correction amount includes: The robot obtains the end position coordinates of the pre-planned grinding motion trajectory at each moment, and superimposes the position correction values ​​in three orthogonal directions onto the end position coordinates at the corresponding moment to generate the adjusted grinding motion trajectory. The adjusted grinding motion trajectory is then sent to the robot control system.

6. The method according to claim 5, characterized in that, The adjustment of the robot end effector speed based on the speed correction amount includes: While generating the adjusted grinding motion trajectory, the speed correction values ​​in the three orthogonal directions are superimposed on the preset running speed values ​​of the robot end effector at the corresponding time to generate the adjusted end effector running speed values, which are then sent to the robot control system.

7. The method according to claim 1, characterized in that, The continuous cyclic execution of acquiring and calibrating the original signal and real-time pose information, mapping the position and speed corrections, and adjusting the preset grinding motion trajectory ensures that the contact force between the robot end effector and the workpiece remains at a preset constant value, thus completing the compliant constant force grinding operation, including: Throughout the grinding operation, signal acquisition, data processing, correction mapping, and trajectory speed adjustment are performed in a fixed cycle. When the robot end is not in contact with the workpiece, it maintains the preset grinding motion trajectory. When the robot end is in contact with the workpiece, the end motion state is dynamically adjusted to suppress contact force oscillation. After the robot end is in complete contact with the workpiece, a preset constant contact force is stably output.

8. The method according to claim 1, characterized in that, The method further includes: The system pre-stores preset constant contact force values ​​and admittance controller parameter combinations corresponding to various workpiece materials. Before the grinding operation starts, it identifies the material type of the workpiece and automatically matches and loads the corresponding preset constant contact force values ​​and admittance controller parameter combinations based on the identified material type.

9. The method according to claim 1, characterized in that, The method further includes: During the grinding process, the actual external contact force value is judged in real time to see if it exceeds the preset safety threshold range. If the actual external contact force value exceeds the preset safety threshold range, a stop command is immediately sent to the robot control system, and grinding abnormality alarm information is generated at the same time.

10. A robotic compliant constant-force grinding system based on admittance control, used to implement the method as described in any one of claims 1-9, characterized in that, include: The signal acquisition unit is used to continuously acquire the raw signals output by the six-dimensional force sensor at the end of the robot throughout the grinding operation, and simultaneously obtain the real-time pose information of the robot end. The acquired raw signals are calibrated to remove zero-point drift values. Combined with real-time pose information, the gravity component generated by the end-effector load is calculated and eliminated to extract the real external contact force on the robot end-effector. The speed adjustment unit is used to input the real external contact force into the admittance controller based on the mass damping spring model in real time. The admittance controller maps the real external contact force into the position correction and speed correction of the robot end effector. The robot's preset grinding motion trajectory is adjusted according to the position correction, and the robot end effector running speed is adjusted according to the speed correction. The grinding completion unit is used to continuously and cyclically perform the acquisition and calibration processing of the original signal and real-time pose information, the mapping of position correction and speed correction, and the adjustment of the preset grinding motion trajectory, so that the contact force between the robot end and the workpiece being ground is always maintained at a preset constant value, thus completing the compliant constant force grinding operation.

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