Symmetric damping bilateral control for parallel manipulators

A symmetric damping bilateral master-slave control scheme is proposed in order to enable the stable contact between the slave manipulator end-effector and the rigid environment. In the conventional force reflecting position control method, control loops in master and slave sides are connected to each other in series and that causes unstable motion when the slave manipulator contacts with rigid objects. The new method has more stable dynamic characteristic, since lag time of the control loop is smaller due to the symmetric structure of the system. The master-slave system consists of two isomorphic parallel manipulators. Good features with parallel manipulator also improve the system stability. The stability of the proposed control method including the simple operator and object dynamics is analysed by using the Hurwitz stability criterion and then compared with the conventional controller. Metal-to-metal contact and peg-in-hole experiments show practical and wide applicability of the control method.