A modified impedance control design for tele-operational coordinated multiple robot manipulators

在本研究中，提出了一种稳定的远程机器人控制系统的设计，其中远程机器人机械手可以抓取和移动物体。由于用于主系统的操纵杆只有3个运动自由度和2个力反馈自由度，因此从控制系统必须具有自主力控制或阻抗控制，以防止从操纵器与物体因不可避免的接触而损坏。在该系统中，从控制器可以很容易地将运动控制转换为力控制和阻抗控制。通过几个工作实验，验证了该控制系统的有效性。实验一：多个机器人协调举起并搬运一个物体。当左右机械手的运动不一致时，物体就不能保持平衡，也就不能沿着期望的轨迹运动。采用双侧控制系统，操作者可以通过操纵杆的力反馈感受左右从机的接触力，重新调整操作信号。然后从系统可以保持对象的平衡。实验二：多机械手协调抓取弹性物体。当两个机械手抓取一个弹性物体时，各个轴向的接触力和力矩发生复杂。然而，由于操纵杆只呈现力和力矩两个自由度，操作人员对接触感受的理解不足。实验三：协调多个机器人机械手抓取、提升和移动一个刚性物体。如果从机械手的工具方向受到约束，可能会产生过大的接触力和力矩。因此，从控制器修改了姿态的顺应特性。这样操作者就可以在不产生过大的接触力和接触力矩的情况下操纵刚性物体。

In this study, a design of a stable remote robot control system is proposed, where remote robot manipulators can grasp and move an object. Because a joystick used for master system has only 3 degree of freedom of motion and 2 degree of freedom of force feedback, the slave control system must have autonomous force control or impedance control that prevents slave manipulator and the object from being damaged caused by unavoidable contact. In proposed system, the slave controller can switch motion control to force control and impedance control easily. By performing several working experiments, the usefulness of the control system is investigated.Experiment I : coordinated multiple robot manipulators raise and convey an object. When right and left manipulators move inconsistently, an object can not be balanced and not be followed to a desired trajectory. Using bilateral control system, operator can feel the contact force of right and left slave manipulators through force feedback of joysticks and readjust the operational signal. Then slave system can keep balance of the object.Experiment II : coordinated multiple robot manipulators grasp an elastic object. When both manipulators grasp an elastic object contact forces and moments for each axial direction occur complicatedly. However, an operator understood insufficient contact feelings because the joystick only presents two degree of freedom of force and moment.Experiment III : coordinated multiple robot manipulators grasp, lift and move a rigid object. If the orientation of tools of slave manipulators is constrained, excessive contact force and moment may occur. Therefore slave controller modifies the compliance characteristic of the orientation. Then operator can manipulate a rigid object without excessive contact force and moment.