ABSTRACT
Real world applications of an active suspension system in commercial vehicles are very
limited because this system is mostly designed for passenger cars, which are more stable. In
this study, a commercial vehicle with 7 degrees of freedom (DOF) was employed as the
vehicle ride model, including body displacement (Zb), body roll (  ) and body pitch (  ).
This study also presented a 7-DOF commercial vehicle ride dynamics modelling
verification. This model was developed to study the dynamics of vehicles, i.e. the movement
of vehicles, including the vertical vibration, and roll and pitch moments. The parameters for
the model were obtained from CarSim software by selecting the utility truck configuration
with the chassis twist road ride test procedure as a benchmark. This simulation model was
developed by using the MATLAB Simulink software. This model was used to consider all
the important parameters in the analysis of vehicle dynamics for describing motion, and it
was verified by using the CarSim software. The study also incorporated the performance of
a controller for an active suspension system for commercial vehicles. A 7-DOF commercial
vehicle ride model was used to control the dynamic responses of the vehicle, especially in
terms of the body displacement, body roll and body pitch, by using a simple Proportional
Integral Derivative (PID) controller. The simulation result was obtained and analysed by
means of the automatic tuning of the PID value. The road disturbance from the step input
was applied to the tyres of the commercial vehicle. The location of the input was varied for
each tyre and sometimes at both tyres for analysis purposes. Based on this road disturbance,
the performances of the passive and active suspension systems were investigated. The results
indicated that the graphs of the roll angle, pitch angle and body displacement had a similar
trend, although there was an error in the magnitude due to the simplified model in Simulink.
The verification results showed a high percentage of similarity with the CarSim simulation.
In conclusion, the results obtained indicated that the active suspension system gave a better
performance, whereby the offset value decreased to almost zero with an improvement of
90% when hitting a bump.
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