On the use of virtual springs to avoid singularities and workspace boundaries in force-feedback teleoperation

A force-force controller of a master-slave force-feedback teleoperation system is proposed. This scheme is especially suitable for non-backdriveable manipulators. Forces and torques exerted by the operator and the environment and measured by a six axis force sensor are used to compute in real time a desired trajectory which is tracked by a PD controller. This system has been applied to a master-slave system, in which the master robot is a Stewart platform. The use of virtual springs prevents the platform from running into singularities and from getting close to workspace boundaries. Experimental results the satisfactory performance of control algorithm with virtual springs