A perturbation/correlation method for force guided robot assembly

Force guided robot control is a control scheme based on the interpretation of measured force acting on the robot end effector. A functional map relati ng the correction of motion to force measurements is generated based on the geometry of the workpiece and its kinematic behavior in interacting with t he environment. In the traditional force-guided control schemes, the contac t force measured by a force sensor is directly fed back to a feedback contr oller to generate a motion correction signal, In this paper, instead of sim ply measuring contact forces, we take positive actions by giving perturbati on to the end effector and observing the reaction forces to the perturbatio n in order to obtain much richer and more reliable information. By the corr elation between the input perturbation and the resultant reaction forces, w e can determine the gradient of the force profile and guide the part correc tly. By applying a type of direct adaptive control, the contact force is ma intained at the lowest level. This algorithm is applied to a pipe insertion task, in which the insertion force is minimized during the insertion, Base d on the process model and stability analysis using the Popov stability cri terion, conditions for stable, successful insertion despite nonlinearities and uncertainties in the environment are obtained. The theoretical results are verified using the experimental data. To generate high frequency pertur bation, a vibratory end effector using piezoelectric actuators is designed and built. Through both simulations and experiments, the feasibility and us efulness of these methods are demonstrated.