Energy Analysis of Power Steering Systems During a Newly Developed Driving Cycle 2011-01-0230
Developments in power steering systems have been concentrated on the energy consumption as the environmental issues intensified in recent years. After the widely used hydraulic power steering system, the introduction of electric and electro-hydraulic power steering systems has shed light on the energy saving of the power steering system.
In order to evaluate the energy consumption of the systems, firstly a new driving cycle was developed taking into account of both longitudinal and lateral driving behaviour. By comparing the vehicle response to the customer driving behaviour, the most similar sections on different traffic conditions were chosen therefore form the new driving cycle.
Steering models of these three different types, hydraulic, electro-hydraulic and electric power steering systems, were developed and the new driving cycle was used as the inputs to the models so that the energy consumption of the three steering systems can be calculated and compared under the same condition. Typically one of the inputs to the steering models is the lateral acceleration instead of steering angle because different vehicle setup can be simulated and compared using the same lateral acceleration and velocity profile.
The steering models are modelled in a way that a mechanical module and a power assistance module interact with each other. The mechanical module provides steering velocity and rack velocity to the power assistance module while the power assistance module feeds back the assisting force and the friction caused by the power assistance module such as the sealing friction caused by the pressure in hydraulic powered system (HPS). The models predict accurate energy consumption of the steering systems with the new driving cycle.
Accurate power consumption of the systems was predicted due to the inclusion of the lateral dynamics in the new driving cycle. The power consumption of steering systems increases up to 48% compared to the conventional driving cycle. The steering models under the new driving cycle provide very useful information about the energy consumption of the three steering systems. This information can be an essential criterion for future optimisation of new steering systems.