Adaptive observer for the calibration of the force-moment sensor of a space robot

A procedure for the calibration of the force-moment sensor of a space robot is reported. In terrestrial applications, such sensors can be calibrated by measuring the sensor output while under known static loads, which are most easily applied using known weights. In zero-g environment, such an approach does not work. A viable alternative is to use the dynamic effects of the motion of a carried payload to load the sensor. For a rigid robot, the displacement of the payload can be inferred from joint-angle measurements using the robot kinematics. However, major space robots are structurally flexible, in which case establishing a similar inference is difficult. Therefore, it is assumed here that a payload with known mass properties is handled by the end-effector, and that the payload displacement is measured directly using a laser vision system. Then, considering the end-effector and the payload to be one rigid-body, their dynamics equations, which are the Newton-Euler equations, are used to design an adaptive observer that simultaneously generates estimates of the motion of the body and identities the calibration matrix of the sensor. In this paper, as a first step, the problem would be solved for planar robots. The performance of the adaptive observer would then be evaluated through simulations