Modelling of an Active Suspension System for an Anti-Roll Bar in a Passenger Car

Chong, Ming Lun (2017) Modelling of an Active Suspension System for an Anti-Roll Bar in a Passenger Car. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

An anti-roll bar is a type of automobile suspension that helps reduce the load transfer of a vehicle towards the outside of a turn while keeping the tyres in contact with the road. Anti-roll bar also helps the vehicles tyres stay nearer to the vehicles when passing through potholes. This help increase the comfort of riding when the vehicles went through potholes. An anti-roll bar normally consist of two mounting clamps to fix the anti-roll bar to the chassis, two arm connector to connect the anti-roll bar to the left and right side of the suspension arm and the most important the anti-roll bar itself. There are three type of anti-roll bar available in the markets nowadays which are passive, semi-active and active anti roll bar. A passive anti-roll bar is easy and cheap to obtain in the market and easy to install to the vehicles as well but for the semi-active and fully active anti-roll bar is quite expensive and need to give to mechanic to install because it is quite complicated and require some professional skill to tweak the controller. A passive anti-roll bar cannot change the stiffness of the bar according to the needs because the stiffness of the bar is depend on the material use to make the bar but a semi-active and active anti-roll bar is able to change the stiffness of the anti-roll bar according to the road profile and force needed to balance the vehicle. This thesis is about to model an active suspension system which will help reduce the roll angle and the roll rate when the vehicles passing through a pothole and compare the result of a vehicles without anti-roll bar, with passive anti-roll bar as well as with active anti-roll bar. The simulation is done in MATLAB Simulink to investigate the response of the system. Before putting into MATLAB Simulink, the half-car mathematical modelling is converted from a free body diagram into mathematical equation. After converting the free body diagram into mathematical equation, all the mathematical equation will be build using block diagram in MATLAB Simulink. The controller that used for active anti-roll bar is PID. The parameter of the PID is auto tune using the MATLAB auto tuning system for the best result. It is found that the active anti-roll bar have the highest reduction on the roll-angle (0.25 rad) as well as the roll rate (2.2 rad/s) follow up by the vehicle with passive anti-roll bar roll-angle (0.57 rad), roll rate (4.1 rad/s) and last the vehicle without anti-roll bar roll-angle (0.83 rad), roll rate (6.3 rad/s).