基于二阶前馈外力观测器的机械臂碰撞策略

Manipulator collision strategy based on second-order feedforward external force observer

针对人机协作过程中的安全问题,提出基于改进广义动量的外力观测器进行外力检测的方法。建立了外力干扰下的简化柔性关节机械臂动力学模型,通过受力分析证实模型能够识别发生碰撞时的机器人关节等效外力。设计了一种二阶前馈外力观测器用来检测外力,并依据观测器的观测值设定了动态阈值,当观测值超过动态阈值的限定范围时,控制系统即认为碰撞发生,为保证操作人员和机器人的安全,将立刻切换到碰停模式,实现不同运动速度下的安全反应。通过UniversalRobot5(UR5)轻量机械臂实验平台,验证了外力观测器和动态阈值的有效性与可行性。

Aiming at the safety in the process of human-me cooperation, an external force observer based on improved generalized momentum was proposed to detect external forces. The simplified flexible manipulator model under external force was established, and the force analysis was carried out to identify the equivalent joint force of robot when the collision occurred. A second-order feedforward external force observer was designed to detect external forces, and the dynamic threshold was set according to the observed value of the observer. When the observed value exceeded the limited range of dynamic threshold, the control system confirmed that the collision had occured. To ensure that the operator and robot safety, the touch-stop mode would be switched immediately to achieve the safety of the reaction at different speeds. The validity and feasibility of the external force observer and the dynamic threshold with Universal Robot 5(UR5)lightweight manipulator experimental platform was verified.