Abstract
This study applies nonlinear model predictive control (NMPC) to the torque-vectoring (TV) and front-to-total anti-roll moment distribution control of a four-wheel-drive electric vehicle with in-wheel-motors, a brake-by-wire system, and active suspension actuators. The NMPC cost function formulation is based on energy efficiency criteria, and strives to minimize the power losses caused by the longitudinal and lateral tire slips, friction brakes, and electric powertrains, while enhancing the vehicle cornering response in steady-state and transient conditions. The controller is assessed through simulations using an experimentally validated high-fidelity vehicle model, along ramp steer and multiple step steer maneuvers, including and excluding the direct yaw moment and active anti-roll moment distribution actuations. The results show: 1) the substantial enhancement of energy saving and vehicle stabilization performance brought by the integration of the active suspension contribution and TV; 2) the significance of the power loss terms of the NMPC formulation on the results; and 3) the effectiveness of the NMPC with respect to the benchmarking feedback and rule based controllers.
Highlights
T ORQUE-VECTORING (TV) control, i.e., the modulation of the wheel torque distribution among the four vehicleManuscript received February 22, 2021; accepted April 7, 2021
As the implemented nonlinear model predictive control (NMPC) formulation outputs the front-tototal anti-roll moment distribution factor f, but does not affect the total anti-roll moment generated by the active suspension system, which is only a function of lateral acceleration according to (13), following conversations with the suspension system provider involved in the project, it was decided not to include the suspension actuation power losses in the cost function
The simulation results for an electric vehicle with in-wheel motors (IWMs), active suspension actuators and a brake-by-wire system show the following
Summary
T ORQUE-VECTORING (TV) control, i.e., the modulation of the wheel torque distribution among the four vehicle. TV allows: 1) shaping the understeer characteristic, i.e., the level of lateral acceleration for given steering angle and vehicle speed [1]; 2) enhancing yaw and sideslip damping in extreme transients [1]; and 3) reducing energy consumption during straight line and cornering operation [2]–[6] In this respect, the most recent TV implementations include consideration of the power losses related to longitudinal and lateral tire slip as well as electric powertrains [6]. The case study vehicle, considered in the European project EVC1000 [17], see its main parameters, is simulated with a high-fidelity and experimentally validated simulation model, and is equipped with four in-wheel motors (IWMs), a brake-by-wire system with independent control of the clamping force of each brake caliper, and active suspension actuators.
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