University of Twente Student Theses


Compensation of Friction in the Flight Simulator Stick using an Adaptive Friction Compensator

Seters, Nathan van (2001) Compensation of Friction in the Flight Simulator Stick using an Adaptive Friction Compensator.

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Abstract:Friction deteriorates the performance of many controlled systems with moving parts. It introduces not wanted phenomena to the system, such as stick-slip. steady state errors and tracking errors nearby velocity reversals (the so-called reversal bumps). However, it is possible to compensate for the friction in order to reduce the not wanted friction phenomena. In previous research at the Control Laboratory the friction, in particular the reversal bump, has been compensated for with learning friction compensators. These compensators were able to reduce the reversal bump significantly. Besides learning friction compensation there are other compensation techniques. One of them is adaptive friction compensation. The use of adaptive friction compensation seems well suited because it is known that friction will vary in time, due to wear and temperature changes. An adaptive friction compensators is capable of following these variations in friction. In this thesis three adaptive friction compensators are presented. One is based on the Coulomb friction model and two of them are based on the LuGre friction model. In simulations the adaptive Coulomb friction compensator was able to reduce the reversal bump by a factor 6. The LuGre based adaptive compensators where able to eliminate the reversal bump in simulations, this mainly caused by the fact that the 'real' friction was also represented by the LuGre model. In order to verify the results of the simulations, the adaptive friction compensators are implelrented on the control loading system (flight simulator stick) of FCS. This system is available at the Control Laboratory and also used to implemented the learning friction compensators, so the performances of both techniques could be compared easily. First the friction on the control loading system has been identified (i.e. the LuGre model parameters), for both the simulations and the initial values of the compensators. The three adaptive compensators have been implemented on the Control Loading System The Coulomb based compensator was also in experiments able to reduce the reversal bump, by a factor 7. The first LuGre based compensator was also able to reduce the reversal bump, however due to computation difficulties this was not what was hoped for. The last adaptive compensator was not capable of reducing the reversal bump at all. When both friction compensation techniques, learning and adaptive, are compared to eachother one could say that both techniques are able to reduce the reversal bump. Even the simplest adaptive compensator, the Coulomb friction compensator, is not inferior to the learning friction compensators. And this compensator is easy to implement on a system and requires no a-priori knowledge (which is the main advantage of learning compensation).
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering MSc (60353)
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