On Parameter Estimation of Space Manipulator Systems with Flexible Joints Using the Energy Balance*

The parameter estimation of space manipulator systems on orbit is studied, whose manipulators are subject to joint flexibilities. To improve path planning and tracking capabilities, advanced control strategies that benefit from the knowledge of system parameters are required. These parameters include the system inertial parameters as well as the stiffness and damping parameters, which describe joint flexibilities. During operation some of these parameters may change or be unknown. Estimation methods based on the equations of motion are sensitive to noise, while methods based on the angular momentum conservation, while they are tolerant to noise, they cannot estimate the parameters that describe joint flexibilities. A parameter estimation method, based on the energy balance, applied during the motion of a space flexible-joint manipulator system in the free-floating mode, is developed. The method is tolerant to noise and can reconstruct the system full dynamics. It is shown that the parameters estimated by the proposed method can describe the system dynamics fully. The application of the developed method is valid for spatial systems; it is illustrated by a planar 7 degrees of freedom (DoF) example system.