SATELLITE MOMENTUM WHEEL SPEED CONTROL WITH DRY ROLLING FRICTION COMPENSATION

Friction compensation is necessary for many mechanical systems in order to reduce cost, improve safety and increase performance. When problem avoidance techniques are not applicable, a friction compensation controller is used instead. Most friction compensation controllers require an accurate friction model. However, in reality it is very difficult to obtain the accurate model information; consequently the performance of these controllers is limited and dependent on the accuracy of the model. Using a control structure that is based on the form of the problem rather than the specific model coefficients, this thesis presents a new friction compensation technique that is able to estimate and compensate friction in real time. This control structure is robust, less sensitive to the system’s dynamic variations, and can be generalized and applied to other systems with different types of friction. A nonlinear-based speed controller is also proposed, which can be applied to systems with high stiction, limited control effort, or applications that employ a flexible coupling. Hardware implementation results of these controllers are presented as they have been applied to a speed control problem with a high coefficient of dry rolling v friction and other hardware constraints, some of which are: reduced processor bandwidth, limited control effort, and measurement noise. The problem originated from the need of precisely controlling the speed of the momentum wheels for attitude control purposes, an integral part of the first lab-based satellite at Cleveland State University (VikSat1). The engineering design of VikSat1’s Attitude Determination and Control Subsystem is also presented.