摘要
SSRMS构型机械臂被广泛应用于空间在轨服务,但是由于冗余自由度以及肩、轴、腕部偏置的存在,导致逆运动学求解困难。关节角参数化方法虽然能求得逆运动学的解析解,但是求解成功与否高度依赖于参数的给定值。基于雅可比矩阵的求解方法考虑避奇异时会损失机械臂的运动性能。为此,提出了一种基于循环坐标下降法与关节角参数化方法联合的逆运动学求解方法(CCDJAP-IK),该方法具有对雅克比矩阵奇异不敏感,避免关节极限以及求出多组逆运动学精确解的优点。将采用循环坐标下降法求得的近似解作为关节角参数化方法中参数的给定值,减少了参数取值的盲目性,增加了求解的成功率。将末端执行器的运动转化为关节6末端点仅y轴方向受约束的达点运动,简化了目标函数以及算法的迭代步骤,提高了计算效率。以HIT-SSRMS构型机械臂为例开展了仿真实验,结果表明:在当前构型和期望位姿均在工作空间内随机选取的情况下,CCDJAP-IK方法的平均计算时间为4.86 ms,求解成功率为99.32%,是一种有效且可靠的求解SSRMS构型机械臂逆运动学的方法;在跟踪笛卡儿路径时,CCDJAP-IK方法的跟踪精度、关节空间连续性以及实时性均满足任务要求,因此可应用于机械臂的实时路径跟踪任务。
The SSRMS-type manipulators are widely used in space on-orbit services,but the inverse kinematics is difficult to solve due to redundancy and the existence of shoulder,axis,and wrist offsets.Although the joint angle parameterization method can obtain the analytical solution of inverse kinematics,the success rate is highly dependent on the given value of the parameter.The method based on the Jacobian matrix will reduce the kinematics performance of the manipulator when considering singularity avoidance.To solve these issues,an inverse kinematics solution method(CCDJAP-IK)based on the combination of the cyclic coordinate descent method and the joint angle parameterization method is proposed.This method has the advantages of being insensitive to Jacobian matrix singularities,avoiding joint limits,and finding multiple exact solutions.The approximate solution obtained based on the cyclic coordinate descent method is used as the given value of the parameter in the joint angle parameterization method,which reduces the blindness in determining parameter value and increases the success rate of the solution.The movement of the end effector is converted into the movement of the endpoint of the sixth joint restricted only in the y-axis direction,which simplifies the objective function and the iterative steps of the algorithm,and improves the calculation efficiency.Taking the HIT-SSRMS manipulator as an example,simulation experiments are carried out.The results show that:under the condition that the current configuration and the desired pose are randomly selected in the workspace,the average calculation time and the success rate of the CCDJAP-IK method are 4.86 ms and 99.32%,respectively,which is an effective and reliable method for solving the inverse kinematics of SSRMS-type manipulator.When tracking the Cartesian path,the tracking accuracy,joint space continuity,and real-time performance of the CCDJAP-IK method meet the task requirements,so it can be applied to the real-time path tracking task of the manipulators.
作者
赵智远
赵京东
赵亮亮
杨晓航
刘宏
ZHAO Zhiyuan;ZHAO Jingdong;ZHAO Liangliang;YANG Xiaohang;LIU Hong(State Key Laboratory of Robotics and System,Harbin Institute of Technology,Harbin 150001)
出处
《机械工程学报》
EI
CAS
CSCD
北大核心
2022年第3期21-35,共15页
Journal of Mechanical Engineering
基金
国家自然科学基金资助项目(91848101,91848202)。
关键词
冗余机械臂
逆运动学
循环坐标下降法
关节角参数化方法
redundant manipulator
inverse kinematics
cyclic coordinate descent method
joint angle parameterization method
