Prediction of Static Steering Torque During Brakes-Applied Parking Maneuvers

This paper discusses the use of a simulation model to predict static steering torque during parking maneuvers with the vehicle's brakes applied. Accurate prediction of static steering torque early in the product design cycle is necessary for steering component sizing as well as to assess the impact changes to wheel end geometry will have on static steering torque. The static steering torque is shown to be the sum of three main components: (1) torque required to slide the tire contact patch across the road surface, (2) torque required to overcome friction in the kingpin joints and steering linkage, and (3) torque generated by vertical force moments about the kingpin axis. Each of these components is discussed in detail, with particular attention paid to examining how their magnitude varies with steer angle. Correlation between predicted and measured static steering torque on an actual vehicle is presented for model validation. Also presented is a dimensional analysis of the static steering torque model and an example solution using dimensional analysis.