Computer simulation of controlled impedance robot hand

Robot grippers have previously been designed primarily without consideration of the dynamic responses that are sometimes required for delicate operations. In particular, the manipulation of fragile objects such as eggs or lightbulbs requires the gripper to be able to close on the object with minimal impact forces and yet maintain a static grip force sufficient to firmly handle the object. This paper describes a computer simulation of a two-fingered mechanical gripper with electronically controlled impedance. The analog control system allows independent control of the effective mechanical mass and damping of each finger as well as additional control of common-mode vs. differential mode response. The computer simulation models the gripper as set of nonlinear differential equations with time varying feedback parameters. The final form of the model has 10 degrees of mechanical freedom and 8 electrical poles, i.e., an 18th order nonlinear differential equation must be solved. This paper will describe the dynamic equations in detail and discuss results of the analysis. An appendix details the state equations used to solve the nonlinear differential equations. This analysis has resulted in the design of a gripper control system capable of providing controlled compliance and reduced finger impact forces while maintaining a quick response and firm grasp.