Optimal regenerative torque control to maximize energy recapture of electric vehicles

Battery-powered electric vehicles may capture regenerative energy to extend driving range. However, while larger regenerative braking torque attains more regenerative power, excess braking torque may lock up the wheel and result in safety issues. In effect, maximization of the regenerative torque and in turn the energy recapture is subject to the safety requirements. This paper translates the energy recapture problem into a wheel-slip control problem then develops an optimal regenerative torque controller to achieve the goal. The design employs a sliding mode control to manipulate the operating point and resist uncertainties, and an optimal linear control to maintain the longitudinal wheel slip at the desired value. The efficacy of the optimal regenerative torque control system is verified for critical operating conditions of the electric vehicle.