Force control and nonlinear master-slave force profile to manage an admittance type multi-fingered haptic user interface

Natural movements and force feedback are important elements in using teleoperated equipment if complex and speedy manipulation tasks are to be accomplished in remote and/or hazardous environments, such as hot cells, glove boxes, decommissioning, explosive disarmament, and space to name a few. In order to achieve this end the research presented in this paper has developed an admittance-type exoskeleton like multi-fingered haptic hand user interface that secures the user's palm and provides 3-dimensional force feedback to the user's fingertips. Atypical to conventional haptic hand user interfaces that limit themselves to integrating the human hand's characteristics just into the system's mechanical design, this system also perpetuates that inspiration into the designed user interface's controller. This is achieved by manifesting the property differences of manipulation and grasping activities as they pertain to the resilient human hand into a nonlinear master-slave force relationship. The results presented in this paper show that the admittance-type system has sufficient bandwidth such that it appears nearly transparent to the user when in free motion. Also, when executing a manipulation or grasping task, increased performance is achieved using the nonlinear force relationship compared to the traditional linear scaling techniques implemented in the vast majority of systems.