Variable motion mapping to enhance stiffness discrimination and identification in robot hand teleoperation

In robot hand teleoperation system, force feedback is critical for operator to perceive the physical property of grasped objects. However, it is challenging to implement accurate force feedback if the force accuracy of a haptic device is limited. This paper proposes a variable motion mapping method to enhance stiffness discrimination of the remote object. In this method, the motion mapping coefficient is regulated according to the object stiffness so that the operator can perceive the stiffness difference of the remote objects. To validate the proposed approach, we conducted two experiments on a three-finger robot hand (BarrettHand BH8-280) teleoperation system. In the first experiment, we measured the minimum relative change in feedback stiffness that could be detected by the operator. The result shows that the relative change should be 70% for a correct detection rate of about 91%. Based on the result, the motion mapping coefficient was selected for the system. In the second experiment, the variable motion mapping method was compared to a constant motion mapping method. The experimental task in the comparison is identifying four objects through stiffness perception alone. The experimental results show that the variable motion mapping method enhances the discrimination of the objects. The operator can identify individual object within a group of four without visual feedback with the variable motion mapping method.