基于改进Bi-RRT算法的双臂空间机器人关节角驱动力矩控制

中图分类号:TP241???? 文献标识码:A

摘要:

空间机器人双臂运动涉及非线性动力学效应,关节力矩作用点随机械臂构型动态变化,难以建立关节力矩输入与末端轨迹跟踪的显式解析关系。这种非线性动力学耦合特性使关节力矩与轨迹规划之间的协同优化变得复杂,增加了角偏航的风险,导致双臂关节角驱动力矩控制难度较大。为了解决该问题,提出了基于改进Bi-RRT算法的关节角驱动力矩控制策略。使用改进后的A*算法代价估计函数,优先搜索代价最小路径,提升找到最优或近似最优关节采样点的速率。根据双臂空间机器人关节角驱动转向函数,实现力矩控制轨迹自适应搜索。在全局偏航分数、最短距离计算路径代价得分约束下,计算当前关节配置与全局期望轨迹的关节角偏航角,量化偏航程度并转化为全局偏航分数,准确评估轨迹方向的变化幅度,从而避免偏离全局期望路径。结合PI控制器,设计关节角驱动力矩控制结构,避免出现双臂摆动快速响应任务需求而过度响应的问题,增强控制结构稳定性。由实验结果可知,该方法左、右臂驱动力矩变化范围分别为[-4N.cm-50N.cm]、[-26N.cm-8N.cm],与实验指标一致。双臂运动轨迹也与实验指标一致,说明使用该方法能够抵抗多种复杂干扰影响,双臂在三维空间坐标系的运动轨迹与实验指标一致。

Abstract:

The dual arm motion of space robots involves nonlinear dynamic effects, and the joint torque application point dynamically changes with the configuration of the robotic arm, making it difficult to establish an explicit analytical relationship between joint torque input and end effector trajectory tracking. This nonlinear dynamic coupling characteristic makes the collaborative optimization between joint torque and trajectory planning complex, increases the risk of angular yaw, and makes it difficult to control the dual arm joint angular drive torque. To address this issue, a joint angle drive torque control strategy based on an improved Bi RRT algorithm was proposed. Using the improved A * algorithm cost estimation function, priority is given to searching for the path with the minimum cost, which improves the rate of finding the optimal or approximately optimal joint sampling points. According to the joint angle driving steering function of the dual arm space robot, adaptive search of torque control trajectory is achieved. Under the constraints of global yaw score and shortest distance calculation path cost score, calculate the joint angle yaw angle between the current joint configuration and the global expected trajectory, quantify the degree of yaw and convert it into a global yaw score, accurately evaluate the magnitude of trajectory direction changes, and avoid deviating from the global expected path. Combining PI controller, design a joint angle driving torque control structure to avoid the problem of rapid response to task requirements caused by double arm swing and excessive response, and enhance the stability of the control structure. According to the experimental results, the range of changes in the driving torque of the left and right arms of this method is [-4N. cm-50N. cm] and [-26N. cm-8N. cm], respectively, which is consistent with the experimental indicators. The motion trajectory of both arms is also consistent with the experimental indicators, indicating that this method can resist various complex interference effects. The motion trajectory of both arms in the three-dimensional coordinate system is consistent with the experimental indicators.