摘要
并联机器人是一种多支链、多关节、强耦合非线性系统,具有高速、高刚度和大负载等明显优势而被广泛应用到工业领域。然而,随着关节数量的增加导致该类机器人运动学解耦和高精度平稳控制的难度较大。为实现大范围平动3-RRRU并联机器人自动化轨迹跟踪和控制的平稳性,针对运动学解耦和速度自适应规划方法展开了系统、深入地研究。首先,应用DH法建立了机器人运动学模型,基于结构约束条件完成运动学解耦计算,并在S型控制策略中加入速度自适应修正机制,依据不同轨迹可自动计算并修正最大速度参数,实现自适应优化;其次,采用激光跟踪仪对机器人轨迹进行动态跟踪,对比分析了S型速度和梯型速度控制策略下的跟踪精度,梯型速度规划下其最大误差高达4.513 mm,是S型控制策略的3倍,且位置误差曲线出现多个尖峰值,说明因速度突变导致运动平稳性较差;最后,测试S型速度规划下采用自适应修正机制前、后机器人的平稳性以及轨迹跟踪精度。实验结果表明:当规划路径难以实现机器人加速到原预设最大速度时,在轨迹末端存在较大的惯性速度,产生位置尖峰误差为2.676 mm,是修正后最大误差的2.4倍,且伴随着明显的冲击效应。引入自适应修正机制后圆轨迹的起点和终点位置误差分别为0.722 mm和0.382 mm,二者相对位置偏差仅为0.34 mm,且末端定位误差相比修正前降低了一个数量级,有效解决了机器人存在惯性冲击效应的难题,大幅提高了机器人整体轨迹跟踪的精度和控制的平稳性。
Parallel robot is a kind of nonlinear strong coupling system with many branches and joints.It has obvious advantages of high speed,high stiffness and large load.So,it is widely used to industrial field.However,with the number of joints increasing,it becomes more difficult to finish kinematic decoupling and precision control.In order to realize automatic trajectory tracking and stable control of 3-RRRU parallel robot,kinematic decoupling and velocity adaptive planning method are systematically and deeply researched.The kinematic equations are derived by DH theory and space vector method.Inverse kinematics calculation is completed based on structural constraints.The velocity correction mechanism is added to the S-type control strategy,and the maximum speed parameters can be calculated and revised automatically according to different trajectories.It realizes the adaptive optimization ofthe speed control strategy.The laser tracker is used to track the robot's path,and the accuracy is compared and analyzed under control of standard S-type and ladder type.The maximum error reaches to 4.513 mm,which is 3 times of the S-type control strategy.There are several error peaks on the position curve which shows that the motion stability is poorer due to the sudden change of speed.On this basis,the second experiment is carried out.We test the stability and tracking error of the robot before and after adopting correction mechanism for the S-type speed control under the circular trajectory.The experimental results have shown that when robot can't achieve the maximum speed on the preset path,the original max speed is still control parameter which cause the asymmetric distribution of the speed control curve.Therefore,when the robot reaches the end of the trajectory,it also owns a large inertia speed and results in a peak error of 2.676 mm which is 2.4 times of the after correction.Robot stops accompanied by obvious shaking.After adaptive correction,the position errors of the starting point and the ending point are 0.722 mm and 0.382
作者
赵新华
刘培昌
赵磊
李彬
ZHAO Xin-hua;LIU Pei-chang;ZHAO Lei;LI Bin(Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control,School of MechanicalEngineering,Tianjin University of Technology,Tianjin 300384,China;National Demonstration Center for Experimental Mechanical and Electrical Engineering Education Tianjin University of Technology,Tianjin 300384,China;School of Mechanical Engineering,Tianjin Unirversity of Technology,Tianjin 300384,China)
出处
《光学精密工程》
EI
CAS
CSCD
北大核心
2021年第2期305-315,共11页
Optics and Precision Engineering
基金
国家重点研发计划资助项目(No.2017YFB1303502)
国家自然基金面上项目资助(No.51975412)
天津市自然科学基金资助项目(No.18JCYBJC87900).
关键词
大范围平动
并联机器人
运动学解耦
自适应控制
精度
large overall translation
parallel robot
kinematic decoupling
adaptive control
accuracy
