Attitude Control and Parameter Optimization: A Study on Hubble Space Telescope

Abstract

In this work, we build a satellite attitude PID controlled system by using the Hubble Space Telescope parameters as a reference and tune its controller parameters using various tuning methods. First, we give the equations for the motion of a satellite. We elaborate the control structure as controller, actuator, dynamics and kinematics subsystems and construct an external disturbance model. We use a reaction wheel assembly used in the Hubble Space Telescope with the same configuration as the actuator. We evaluate the performance of the linearization by comparing it with the nonlinear model output. By working on the linearized model, we tune the PID controller parameters using two different methods: "Model-Based Root Locus Tuning” and "Genetic Algorithm Based Tuning". First, we obtain the controller parameters by manipulating the poles on the root locus plot of the linearized system. In addition, we use genetic algorithms to find the optimized controller values of the system. Finally, we compare the performances of the two methods based on their cost function values and find that the Genetic Algorithm-based tuned parameters are more fruitful in terms of the cost function value than the parameters obtained by the Root Locus-based tuning. However, it is found that the Root Locus-based tuning performs better in disturbance rejection.