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Previous work has shown power steering boost gains are uniquely determined given a vehicle and a single objective target. The objective target used was steering gain, Sg, vs. lateral acceleration, ay, where steering gain is defined as the slope of the torque vs. lateral acceleration relationship. The previous work is expanded and applied to real world steering systems. Specifically, methods are provided to determine boost gain shapes given a user-defined steering gain vs. lateral acceleration specification or steering gain vs. torque specification. Each specification method is described in detailed steps. Approximations of each method are discussed and analyzed for practical use. The influence of static friction on steering performance is derived. It is shown that the hysteresis of the steering system is due to a coupling between static friction and a vehicle parameter that is easily derived from the bicycle model. Test results are provided to validate predictions.

An approach to electric steering control and tuning is developed using vehicle dynamics and quantitative steering objectives. The steering objective chosen is the torque vs. lateral acceleration target for the driver termed the “steering gain”. Two parameters are derived using vehicle dynamics that substantially determine driver feel: the vehicle’s “manual gain” (total steering torque divided by lateral acceleration) and the vehicle’s lateral acceleration gain (lateral acceleration divided by steering angle). Lateral acceleration gain is a well-known quantity in the literature but “manual gain” is a nonstandard point of view for steering control systems. The total gain inside the controller is the loop gain; generally, the higher the loop gain, the better the controller rejects unwanted effects such as friction. For a typical torque-input electric steering topology, it is shown that the relationship between loop gain and steering gain is unique.