Optimal and skyhook - controlled suspension for a 4-axle heavy off-road vehicle

This paper deals with advanced suspension systems of heavy vehicles. An analytical 6-DOF heavy off-road vehicle model was developed and applied to study the behavior of semi-active skyhook, groundhook and hybrid control schemes. Controllers were coded as on/off controllers and were compared with continuous optimally controlled semi-active and optimally controlled fully-active suspension systems. Actuators were assumed to be ideal. In derivation controllers' frequency domain analysis was used. The actual simulation runs with different suspension systems were carried out with random road excitation modeled from the desired spectral characteristics. RMS values were calculated from body heave and pitch acceleration. Vibration signal was also filtered with ISO2631 frequency weighting to calculate the frequency-weighted acceleration RMS values. Calculated RMS values were used as a measure of passenger/driver comfort. Tire deflection was used as a measure of vehicle handling. These parameters and comparison of different controllers are presented as a result. The values for a conventional, passive suspension are also presented and compared to advanced suspension systems.