On Robust Control Laws Trade-off Analysis for Space Manipulators with Uncertain Parameters and Flexible Appendages*

To accurately accomplish on-orbit tasks using Space Manipulator Systems (SMS), advanced model-based controllers, dependent on the knowledge of SMS parameters, can be employed. However, these parameters may change on orbit for several reasons. Also, during an SMS task, excitation of flexible appendages, such as solar panels, or fuel sloshing may introduce significant end-effector errors. Therefore, controllers robust to parametric uncertainty and disturbances are needed. A robust controller attractive due to its small computational effort is the Linear Parameter Varying (LPV) gain-scheduled controller. However, its design for spatial SMS is not trivial and has not been studied yet. Therefore, the aim of this work is to study and compare robust controllers and examine their applicability to SMS. An LPV plus H
∞
controller is compared with a Model-Based PD, and a Model-Based PD plus H
∞
controller, in the presence of parametric uncertainty, noisy measurements and disturbances, using a planar example. The criteria considered include: (i) Design Complexity, (ii) Trajectory Errors, (iii) Required Torques, and (iv) Computational Effort.