ACHIEVING FINE POSITIONING ACCURACY IN LARGE MANIPULATORS WITH APPLICATION IN CANCER PROTON THERAPY

Abstract Important robotic tasks could be effectively performed by powerful and accurate manipulators. However, high accu-racy is generally difficult to obtain in large manipulators capable of producing high forces due to system elastic and geometric distortions. A method is presented to identify the sources of end-effector positioning errors in large manipulators using experi-mentally measured data. The method does not require explicit structural modeling of the system. Both geometric and elastic de-formation positioning errors are identified. These error sources are used to predict, and compensate for, end-point errors as a function of configuration and measured forces, improving the system absolute accuracy. The method is applied to a large high-accuracy medical robot. Experimental results show that the method is able to effectively correct for the system errors