Camera-assisted calibration of SCARA arms

Robot calibration is an effective and economical means for enhancing the accuracy performance of a robot manipulator through modification of its control software. This paper reports some research results by applying Lenz and Tsai's approach (1989) to calibrate a SCARA arm equipped with a hand-mounted camera. In order to measure robot poses, a new technique was employed to calibrate the camera at various robot configurations. The camera calibration technique is singularity free even when the image plane is nearly-parallel to the camera calibration board. Second, the modified complete and parametrically continuous (MCPC) model was used to describe the geometry of the SCARA arms because there is no model singularity in the MCPC model for this type of robots. Experimental studies were conducted to demonstrate the feasibility of the present approach for calibrating SCARA arms. Some practical recommendations are also made for robot users who need to calibrate SCARA arms.