A New Shock Absorber Model with an Application in Vehicle Dynamics Studies

The shock absorber plays a vital role in reducing the vertical and horizontal motions of the vehicle in order to have good handling and ride features. A good representation of the damper behaviour is very important in vehicle dynamics studies. The damper force of a shock absorber is indirectly generated by pressure-oil flow relationships through hydraulic valves, which are a part of the inner structure. A completely new aspect is the representation of damper force by mathematical expressions on the basis of a formula. A series of measurements have been carried out with aid of a hydraulic flow bench. The data obtained is fitted on the formula with coefficients, which describe some of the typical quantities of a shock absorber such as damping rate, blow-off factor and secondary damping rate with great accuracy. With the coefficients it is possible to obtain a relationship between the valve setting and shape of the damper characteristic, which is a relationship between damper force and piston velocity. In this way a new and compact empirical model is obtained, enabling vehicle dynamics studies being carried out to optimize shock absorber and vehicle design. This paper is a result of a joined project between ZF Sachs AG and the China Academy of Railway Science (CARS) in Beijing in China.