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.