Thermal Mapping of HPAS System Based on Steering Kinematic and Tire–Road Contact Patch Sliding Model 2019-26-0225
In hydraulic power assisted steering (HPAS) system higher
steering oil temperature can cause deterioration of oil reservoir,
thermal failure of pump/valves and can diminish system performance.
Thermal analysis is performed for HPAS system architecture
development in order to maintain steering oil temperature within
design limits for optimal performance & increased life of HPAS
steering system. In present study mathematical model of HPAS system
consisting of steering pump, flow and pressure control mechanism,
rotary valve, steering circuit pipes and hoses, thermal interaction
with ambient is developed. The model is able to predict steering
torque-hydraulic pressure dynamics of HPAS system as per design.
Developed HPAS system model is integrated with steering kinematic
and uniquely developed tire-road contact patch sliding model for
estimating non-linear rack force behavior at higher steering angle.
This non-linear rack force has an impact in rack pressure and in
turn on HPAS steering system thermal behavior. The developed model
is validated against 15 cycles of low speed (20 kmph) steering lock
to lock (Figure of 8) standard test. The predicted steering oil
temperature is in close agreement with measurement results.
Aravind Sreekumaran, Shoaib Iqbal
Tata Motors Ltd
Symposium on International Automotive Technology 2019