Conceptual design of an integrated laser-optical measuring system for flexible manipulator

Design of an integrated laser-optical system is presented, including measurement principle, light travelling route design, sensor-based calculation of robot positioning/tracking errors, error compensation and integrated opto-mechatronic system calibration. To measure the 3D deflection deviations in link position and orientation, a laser beam emitted from a semiconductor laser mounted at one end of the link is directed to three PSDs (position sensitive detector) mounted at the other end and the coordinates of the light spots on the PSD are detected. The basis of the measurement is that the light beam is undeformable. The deflection of a link measured is then transformed into the position and orientation error displacements in the local coordinate frame of the link, which are further translated to the robot positioning errors using a perturbation approach. A compensation scheme is proposed to correct the robot positioning errors by adjusting each joint angle about its nominal value. Neural network implementation of the compensation scheme is also explored where the network is applied to realize a highly nonlinear mapping of the joint angle corrections. For the measuring system to work precisely, the mechanical and optical parameters involved in the system model are calibrated by perturbing the robot end-effector at some desired position and simultaneously recording the corresponding coordinates of the light spots on PSD.