A Method to Evaluate Impact of Power Steering on Fuel Economy and Optimization

Vehicle manufacturers strive hard to achieve best in class fuel economy. Apart from light weighting of the structures, driveline optimization and reduction of tire rolling resistance, tapping of parasitic losses is also important and helps to optimize the design of auxiliary power consuming systems. One of such system studied in this work is power steering system. The effect of parasitic losses on fuel economy is predominant for small commercial vehicle compare to heavy vehicles. The evaluation of deterioration in the fuel economy due to implementation of power steering system on one of the small commercial vehicle is carried out using multiple virtual simulation tools. Virtual route profile is modelled using longitude, latitude and altitude data captured through GPS and steering duty cycle is mapped in terms of steering rotation angle. A system level model of hydraulic power steering system is developed. This model is used to calculate transient hydraulic pump operating power for the given steering rotation angle as input, which provides power steering pump duty cycle. This time based power consumption of steering pump over a given duty cycle is used to calculate deterioration in fuel economy of the vehicle. This approach is used to select and optimize the power steering pump to improve fuel economy of the vehicle. Simulated fuel economy is validated with testing.