工程科学与技术2025，Vol.57Issue(3)：278-286,9.DOI:10.12454/j.jsuese.202300718
多补偿融合的气动末端柔顺机构非线性自抗扰控制
Pneumatic Compliant End-effector Using Multi-compensation Integrated Nonlinear Active Disturbance Rejection Control
摘要
Abstract
Objective In robotic polishing operations,an end-effector polishing mechanism is typically used to achieve constant force control.Therefore,the performance of this control directly affects the quality and efficiency of the polishing process.Among various end-effector mechanisms,the pneu-matic type is widely adopted due to its lightweight structure,low cost,robustness,and ease of maintenance.This paper focuses on achieving con-stant force control in a pneumatic end-effector compliant mechanism. Methods Achieving constant force control in this mechanism is challenging due to nonlinear factors within the pneumatic system(such as gas compression,proportional valve dead zones,and cylinder friction)and the effects of posture changes on output force.A novel control algorithm is proposed,integrating five components:nonlinear active disturbance rejection control,gravity compensation,dead zone compensation,LuGre fric-tion model compensation,and data filtering.Nonlinear active disturbance rejection control:A tracking differentiator preprocesses the input signal to reduce overshoot,yielding a tracking signal and its derivative.An extended state observer estimates total system disturbance in real time.A nonlinear state error feedback law performs error correction and compensates for the observed disturbance.Gravity compensation:A gravity com-pensation strategy is developed based on the relationship between gravitational force on the mechanism and its output force at different polishing angles.Dead zone compensation:Minimum and maximum working voltages of the proportional valve are experimentally determined.These volt-ages are used to design mid-position compensation,reducing the dead zone's impact on control performance.LuGre friction model compensa-tion:Friction data is collected under varying cylinder speeds.LuGre model parameters are fitted,and a compensation strategy is developed to off-set frictional disturbances during piston movement.Data filtering:A first-order low-pass filter is integrated into the controller to reduce high-frequency noise in the force sensor readings and enhance control accuracy.The control algorithm is implemented on an STM32F103 microcon-troller operating at 50 Hz.Supporting circuits for the pneumatic actuator are designed,and a test bench is constructed to simulate robot polishing conditions.To mimic posture changes during polishing,the platform angle is manually adjusted using a screw.In addition,to simulate the posi-tion errors that may occur during the robot's motion trajectory planning,a stepper motor with a ball screw is used to control the movement of the connection end of the pneumatic end-effector compliant polishing mechanism closer to or further away from the polishing surface.A variety of working condition simulation experiments were conducted,including:1)constant force loading experiments and sinusoidal force loading experi-ments with the pneumatic end-effector compliant mechanism in a vertically downward position;2)variable-angle constant force loading experi-ments involving changes in the polishing posture of the pneumatic end-effector compliant mechanism;3)external disturbance loading experi-ments involving vertical movement of the connecting section of the pneumatic end-effector compliant mechanism. Results and Discussions Under a set force of 50 N,the designed controller exhibited an average error of 0.21 N and a standard deviation of 0.18 N.This performance is better than that of PID control,which had an average error of 0.27 N and a standard deviation of 0.21 N.In two sinusoidal force tracking experiments with periods of 8 s and 4 s,the results showed that for the 8 s period,the designed controller's tracking performance was comparable to PID control,but with smaller tracking error at extreme points.For the 4 s period,the PID-controlled tracking curve exhibited distortion,whereas the designed controller showed some lag but remained closer to the desired values.Under a 50 N loading with polishing angles varying from 0° to 75°,the controller with gravity compensation had a maximum error of 1.44 N.In contrast,the controller without grav-ity compensation showed a significant decline in end-effector output force as the polishing angle increased,with a maximum error of 8.82 N.Un-der the same loading with disturbances present,the designed controller achieved a maximum error of 7.24 N,compared to 11.79 N with conven-tional disturbance rejection control and 14.77 N with PID control.These results indicate that the designed controller performs better in the pres-ence of disturbances. Conclusions The experimental results demonstrate that the proposed control algorithm offers superior robustness,tracking performance,and dis-turbance rejection compared to traditional PID control.In addition,it effectively compensates for changes in polishing angle,thereby improving the constant force control performance of the pneumatic end-effector actuator.关键词
力控制/气动系统/LuGre摩擦模型补偿/重力补偿/自抗扰控制Key words
force control/pneumatic system/LuGre friction model compensation/gravity compensation/active disturbance rejection control分类
机械工程引用本文复制引用
张树忠,吴乾新,戴福全,王亚兵,张弓..多补偿融合的气动末端柔顺机构非线性自抗扰控制[J].工程科学与技术,2025,57(3):278-286,9.基金项目
国家自然科学基金项目(62073092) （62073092）
福建省自然科学基金项目(2021J011051) （2021J011051）
福建省高校产业合作项目(2020H6025) （2020H6025）
福建省2022年中央引导地方科技发展资金项目(2022L3014) （2022L3014）
2022年省级科技创新重点项目(2022G02007) （2022G02007）
福建省智能加工技术及装备重点实验室开放基金项目(KF-01-22005) （KF-01-22005）
福建理工大学海洋研究专项基金项目(GY-Z23087) （GY-Z23087）
