Multivariable Control of the Space Shuttle Remote Manipulator System Using H2 andH Infinity Optimization

摘要

Three linear controllers are designed to regulate the end effector of the SpaceShuttle Remote Manipulator System (SRMS) operating in Position Hold Mode. In this mode of operation, jet firings of the Orbiter can be treated as disturbances while the controller tries to keep the end effector stationary in an Orbiter-fixed reference frame. The three design techniques used include: the Linear Quadratic Regulator (LQR), Hsub2 optimization, and Hsub infinity optimization. The nonlinear SRMS is linearized by modelling the effects of the significant nonlinearities as uncertain parameters. Each regulator design is evaluated for robust stability in light of the parametric uncertainties using both the small gain theorem with an Hsub infinity norm and the less conservative micron analysis test. All three regular designs officer significant improvement over the current system on the nominal plant. Unfortunately, even after dropping performance requirements and designing exclusively for robust stability, robust stability cannot be achieved. The SRMS suffers from lightly damped poles with real parametric uncertainties. Such a system renders the micron analysis test, which allows for complex perturbations, too conservative.