Integrated Vehicle Stability and Power Management Controls for Electric Vehicles
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An integrated vehicle controller is presented for electric vehicles using independently driven wheel motors. This topology takes an optimal control approach to enhancing a vehicle's performance, stability, and energy consumption metrics simultaneously in a unified software structure. The logical output of this algorithm is a set of re-distributed wheel torques, to create torque vectoring for stability-focused yaw rate tracking, and longitudinal biasing to modify motor load for energy savings. A real-time numerical approach to solving the optimization problem is also presented, and shown to offer benefits over a closed form analytic approach. In this, solution constraints are used to link considerations such as nonlinear motor limits, tire friction envelopes, and lower-level traction control loops. To test the efficacy of this control structure, two vehicle test platforms were constructed as retrofits of production gas SUVs for electric drive. For this, the component layout is given, followed by an explanation of the software code structure as performed in a Simulink/Carsim/dSpace environment. Results from these platforms are given, with experimental and simulation data for traction control, yaw performance tracking and drive cycle power consumption. Proven performance over a variety of maneuvers and surface conditions further demonstrate the controller's stability and suitability for mass production.