In order to reduce road damage and improve vehicle ride beyond that which can be achieved by passive dampers, various hardware options have been looked at. One option available is semi-active dampers, which can sink energy from the system, but cannot source energy to it - they provide a good compromise between performance and weight. Dampers with continuous variability and with a response time of 20 ms or less are required for a significant improvement in heavy vehicle ride performance. This paper investigates the design of a controller for semi-active dampers fitted to tri-axle trailer group, based on available inputs, using full-state feedback (FSF) techniques. A vehicle model is developed that captures the dynamics of a semi-active tri-axle air-suspension system with load sharing between three axles. This model represents many semi-trailer air suspensions in use today. It includes a sprung mass and three unsprung masses, all of which are assumed to move in the vertical direction only. Linear control systems are designed for both 'modified skyhook damping' (MSD) and optimal FSF control. Nonlinearities in the damping elements are modelled. The performance improvements of the control strategies are quantified by measuring the percentage reduction in dynamic body acceleration (BA) and dynamic tyre force (TF) compared to the optimal passive damping case. It is found that the FSF control offers the best theoretical performance when used with the nonlinear damping element, achieving reductions relative to the optimum passive case of 38% in RMS BA and 20% in RMS dynamic TF. This optimum is found only when a gain amplification factor is added into the control loop.
Optimal control of a semi-active tri-axle lorry suspension
Optimale Regelung einer halbaktiven dreiachsigen Lkw-Federung
2006
12 Seiten, 7 Bilder, 1 Tabelle, 13 Quellen
Conference paper
English
Optimal control of a semi-active tri-axle lorry suspension
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