柔性机械臂试探前行的碰撞响应控制策略

摘要

针对柔性机械臂在碰撞过程中的安全问题,仿照人类在黑暗环境中摸索前进的行为提出了一种试探前行的安全碰撞响应控制策略.控制器采用变刚度阻抗控制策略,先根据碰撞对象来调节系统刚度,以实现与被撞对象的软接触,然后控制器以当前位置为起点进行试探运动,若通过上一次碰撞点且无碰撞发生时,控制器恢复高刚度阻抗控制方式,以较高的精度到达目标位置.为了验证提出的控制策略,在4自由度机械臂上进行了碰撞试验,结果表明,该控制策略在无碰撞时具有良好的位置跟踪性能,在发生碰撞时能够有效地保护机械臂本体及被撞对象,从而克服了传统控制策略在碰撞时中止任务的缺点.因此,提出的控制策略是有效可行的.%Focusing on the safety in the collision process between the manipulator and the environment, a safe collision reaction control strategy for tentative moving is proposed by imitating human groping behavior in dark environment. The manipulator is controlled in the impedance control mode with variable stiffness. Contacting with the environment, the controller adjusts its stiffness to realize soft-touch according to the environment stiffness, then the controller utilizes the current position as the starting point for small range trajectory planning and gropes. If the groping movement can pass through the last collision position and no collision occurs again, the controller resumes its high stiffness impedance control mode and eventually reaches the target position accurately. For validating the proposed reaction control strategy, some collision experiments are implemented on the platform of HIT 4 degrees of freedom manipulator. The experiment results show that the proposed controller is endowed with good position tracking accuracy in the absence of colliding, and protects the manipulator and the contact object effectively in collision cases. The reaction control strategy enables to overcome the shortcoming of terminating task once a collision occurs in the conventional controller.