Dynamics of Manipulator Collision with Its Work Environment and an Approach to Evaluation of Tip Collision of Manipulators in Assembly Operations

由于机械臂是由多刚体串联而成的，机械臂与工作环境的碰撞是一种高度复杂的非线性现象，这给机械臂的控制带来了很大的困难。将机械臂碰撞问题视为串联多体机械臂的等效质点与其工作环境之间的碰撞问题。利用机械臂动力学方程的惯性矩阵逆，从理论上引入了从碰撞点看机械臂的等效质量。利用平面机器人在工作环境中进行碰撞实验，得到了碰撞的等效质量和恢复系数。通过机械手碰撞实验，得到了以下结论：1.理论等效质量与实验等效质量吻合较好.机械手末端连杆的恢复系数随碰撞点与撞击点之间的距离而变化，从而将撞击中心诱导到关节上.机械手末端与工作环境的恢复系数取0.5 ~ 0.65。结果表明，机械手与工作环境的碰撞模型可以很容易地预测和评价碰撞冲击效应，如作用在环境上的冲击力和作用在各关节上的冲击力矩。

As a manipulator consists of serial-linked rigid multibodies, the manipulator collision with its work environment is a highly complex and nonlinear phenomenon, which makes controlling of a manipulator very difficult. The study deals with the manipulator collision as a collision between an equivalent massive particle of a serial-linked multibody manipulator and its work environment. The equivalent mass of the manipulator viewed from a point of collision is theoretically introduced by using an inverse inertial matrix of a manipulator dynamic equation. Experiments of collision by the use of planar manipulators with a work environment are conducted to reveal the equivalent mass and the coefficient of restitution. From the experiments of manipulator collision, the following results are obtained :1. The theoretical equivalent mass coincides with the experimental equivalent mass accurately.2. The coefficient of restitution of the final link of manipulator changes with respect to the distance between the point of collision and the percussion point to induce the center of percussion on the joint.3. The coefficient of restitution of the manipulator tip with its work environment takes a value from 0.5 to 0.65.As the consequence it is revealed that the model of a manipulator collision with its work environment can easily predict and evaluate the collision impact effects such as the impulsive forces acting on the environment and the impulsive torques exerted on the each joint.