Non-linear position-force control of objects grasped by multifingered mechanical hands

This paper presents a new non-linear position-force control scheme for cont rol of interaction of objects, grasped by multifingered mechanical hands, w ith the environment. Using the theory of input-output linearization, the ha nd-object dynamics in joint space is first projected along the position and force control directions, input-output linearized and decoupled. Along the position control direction(s), a state feedback controller (SFC) is used f or trajectory tracking. A new dynamic SFC, which programs a variable compli ance, is used along the force control direction(s). The variable compliance is appropriately modulated on the basis of the force feedback information to maintain a desired interaction force level. An optimal grasp force decom position scheme is also developed for the control of grasping forces. The p roposed scheme ensures grasp stability under dynamic conditions. The effica cy of the overall control scheme is demonstrated through numerical simulati on.