Human induced instability in powered hand controllers

The dynamic behavior of a hand controller when it is maneuvered by a human is described. A general control architecture is developed which guarantees various impedances on the hand controller. It is shown that some compliancy either in the hand controller or in the human arm is necessary to achieve stability of the hand controller and the human arm taken as a whole. The actuators´ backdrivability and the dynamics of the hand controller mechanisms are discussed as they relate to system stability. A set of experiments performed on a prototype hand controller is presented to show the system performance