Intuitive Impedance Modulation in Haptic Control Using Electromyography

Humans have multiple ways to adapt their arm dynamics to the task they have to perform. One way of doing this is through co-contraction of antagonist muscles. In telemanipulation this ability is easily lost due to time delays, quantization effects, bandwidth or hardware limitations. In this work a new concept for telemanipulation is presented. The end-point stiffness of a (simulated) telerobot is controlled via a variable impedance controller. The end effector stiffness scales with an estimate of the co-contraction around the elbow of the teleoperator. The telemanipulation concept was evaluated with ten subjects that performed two telemanipulation tasks in six different conditions. Three impedance levels: Low, high, and variable, and two delay settings. The first task was on positioning accuracy, the second task on impact minimization. We have shown that low and variable impedance performed significantly better on the force task than high impedance. We have also shown that high and variable impedance performed significantly better on the position task than low impedance. This shows that the human ability to control arm stiffness can effectively be transferred to a telemanipulated robot.