Utilization of motor current based torque feedback to improve the transparency of haptic interfaces

In this paper motor current based torque feedback compensator is utilized in actuator space together with a closed loop impedance control algorithm instead of model based compensator to improve the transparency performance of haptic interfaces; moreover, a novel transparency evaluation metric is developed to evaluate the transparency performance of these devices. The proposed control algorithm is experimentally tested on a 1 DOF haptic device by employing a low-cost current sensor. It is also tested on a MATLAB/Simmechanics® model of a 2 DOF serial planar elbow type haptic manipulator to show that it is applicable to multi-DOF haptic systems. Free-motion, virtual-load and virtual-wall performance tests are conducted to compare the performance of the proposed control algorithm with the alternative algorithms by means of apparent inertial effects. The results show that the proposed algorithm significantly improves the transparency of the haptic devices.