Symmetric dumping master-slave method for parallel manipulators

In this paper a bilateral master-slave method is proposed which enables a slave manipulator to contact maintain with a rigid environment stably. In the conventional force-reflecting position control method, control loops on the master and slave sides are connected in series, which causes unstable motion when the slave manipulator comes into contact with rigid objects. The new method is much more stable, since the phase lag of the control loop is smaller due to the symmetric structure of the system. Our system consists of two parallel manipulators. Advantages of the parallel manipulator such as simple inverse kinematics, a light movable body, and stiffness, also improve the system stability. The stability of the proposed method is evaluated by the Hurwitz method and compared with that of a conventional controller. Metal-to-metal contact and peg-in-hole experiments demonstrate the practical and wide applicability of the method.