Position and stiffness modulation of a wrist haptic device using myoelectric interface.

Modulation of stiffness provides a great deal of advantage in the way humans interact with the environment, and is very important in successfully performing activities of daily living. In the context of human-machine interactions, stiffness control could provide a safer interaction, especially when dealing with unpredictable environment. In this paper we propose a user-modulated stiffness and position control for the wrist flexion/extension degree of freedom while physically coupled to a haptic device. A virtual position tracking experiment in a varying external force field is designed in order to test the performance of the control strategy with and without co-contraction techniques. Tracking accuracy and smoothness of motion indicate better performance when subjects use co-contraction techniques, and the difference in the two types of experiment is also statistically significant.