Load torque analysis based on the integrated model of HPAS systems

In this paper, we attempt to show the load effect of a typical HPAS system which is widely equipped in the heave duty vehicles. Firstly, a unit by unit modeling procedure is presented for the four fundamental components: steering column, vane pump, rotary valve and pinion-rack unit. Then, an integrated model of HPAS system is set up. For such a complex model, we find that the vane pump is the key element of the link between the engine and the steering system. Due to the mechanism of the vane pump, the load torque is a periodic varying force. Furthermore, we show that the load torque is also related to the engine speed and the steering operations. In order to illustrate the load effect of the HPAS system, numerical examples are carried out. In the simulations, we also use the engine model and the tire model to realize the external circumstances. The results show that itpsilas necessary to compensate the additional load torque during the steering operations so as to improve the performance of the engine speed regulation.