Control algorithms to reduce dissipated power and temperature in magnetorheological fluid dampers

Magnetorheological fluid dampers with semi-active control policies have shown performance benefits compared to standard passive dampers in road going applications. However in off-road applications, the dampers dissipated too much heat for the fluid and the seals to handle. Rather than attempt costly vehicle redesigns for hardware cooling solutions, this thesis examines the question of whether the damper temperatures can be effectively reduced by changing the dampers' control strategy.;To simulate the damper temperature response to dissipated power, a thermal model was developed and calibrated against temperature data provided by Lord Corporation. A nonlinear heave/pitch model of the vehicle was also developed and used in conjunction with the thermal model to simulate the temperature response to various control strategies. Terrain data which was collected and provided by Lord Corp. was used as the road disturbance input to the vehicle model.;Model reference controllers as well as predictive controllers were developed and tested against the standard skyhook control policy. Due to a dependence on characteristics of the terrain, an algorithm was not found that always outperformed the others. The new algorithm that most often performed better than the standard skyhook policy was a simple modification to its logic. Rather than mimic an imaginary skyhook damper, the most successful algorithm used only the extremes of available damping force and the same on/off logic as skyhook.;Though it was shown possible to reduce the damper temperatures by changing their control strategy, the savings were too small to be considered effective. Other solutions will be needed in conjunction with the modified control strategy to significantly reduce temperatures.