High-precision visual control of mobile manipulators

In this paper, we present a high-precision visual control method for mobile manipulators called mobile camera-space manipulation (MCSM). Development of MCSM was inspired by the unique challenges presented in conducting unmanned planetary exploration using rovers. In order to increase the efficacy of such missions, the amount of human interaction must be minimized due to the large time delay and high cost of transmissions between Earth and other planets. Using MCSM, the rover can maneuver itself into position, engage a target rock, and perform any of a variety of manipulation tasks all with one round-trip transmission of instruction. MCSM also achieves a high level of precision in positioning the onboard manipulator relative to its target. Experimental results are presented in which a rover positions a tool mounted in its manipulator to within 1 mm of the desired target feature on a rock. MCSM makes efficient use of all of the system's degrees of freedom (DOF), which reduces the required number of actuators for the manipulator. This reduction in manipulator DOFs decreases overall system weight, power consumption, and complexity while increasing reliability. MCSM does not rely on a calibrated camera system. Its excellent positioning precision is robust to model errors and uncertainties in measurements, a great strength for systems operating in harsh environments.