Development of a control scheme for a quarter car test rig

Ehteshum, Mehedi (2018) Development of a control scheme for a quarter car test rig. Masters thesis, Memorial University of Newfoundland.

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Abstract

Road holding performance and vibration isolation of an automobile are some of the most important criteria for human perception of ride quality. For this, the accurate estimation of car body vibration is a prerequisite. A 2-DOF quarter car is a simple, but still reasonable approach to study the dynamic behaviour of a car body. This thesis illustrates the development of control scheme hardware for a quarter car model based on an existing test rig. The test rig parameters are estimated using different static and dynamic tests. The parameters are then used to develop a passive nonlinear model for the test rig. A similar linear model is used to develop an idealized controller. The controller is then applied to the nonlinear simulation model to make it active, and its performance is found to be slightly better at low frequencies for the nonlinear model. The actuator dynamics are then included in the active model to make it realistic. A comparative study of the ideal and realistic model shows that the realistic active model generally shows better ride quality, specially at high frequencies. This model will offer the future researchers a realistic control scheme for the quarter car test rig. The thesis shows the implementation of a new software (20-sim 4C) and hardware system to allow control signals to be sent from the simulation software to the physical quarter car, and verification of the software and hardware by controlling a voice coil actuator using pulse-width modulation to follow a position command signal and then a force command signal. It is observed that as the frequency of the command signal increases, the amplitude loss in the response increases. The actuator can generate only about 5 N force when the frequency of the force command signal is above about 10 Hz. A more robust actuator with higher bandwidth will be required for hardware replication of the maximum potential active suspension benefit predicted by the simulation models.

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