(A) macro/micro robotic probing system with active compliance

Abstract

Since impact phenomenon is highly nonlinear, the analysis and control of the contact motion has been a challenging subject. Various researches have been carried out mostly for the contact of a rigid robotic manipulator with a stiff and elastic environment. This paper is motivated by a new contact task: the in-circuit test of a printed circuit board. In this process, high speed contact occurs between a rigid probing manipulator and a plastically deformable work environment. Ideal robotic contact motions should be quick and stable with minimal impact forces, minimal plastic deformation, and without bounce. However, these specifications are very difficult to achieve simultaneously for the most common manipulator force control configuration employing just a wrist force sensor and a stiff manipulator position loop. To accomplish the requirements successfully, we propose a new probing mechanism and an impact control strategy that considers force feedback and velocity control predictively obtained from location information of the probing manipulator relative to the surface of the environment to be contacted and then switches to only force control with small gains when the end-effector of the manipulator becomes to contact with the object. Particularly, the probing mechanism is based on the macro/micro manipulator concept. To obtain fast response, the micro motion device utilizes a precision eletromagnetic actuator. Experimental results show the effectiveness of the proposed control strategy and the system performance in the probing task is analyzed. To investigate the dynamic behavior of a robotic manipulator during the contact transition, we presented a new impact model considering the contact between the rigid manipulator and a plastically deformable environment. In order to reduce the initial peak impact force and avoid the slip motion of the probe tip on the surface of the arbitrary shaped object, the probing system has to be capable of changing its approach pos...