This paper presents an optimal control strategy for assigning wheel slips on all of the wheels of a tractor/trailer combination. Most ABS controllers work on a wheel by wheel or an axle by axle basis without consideration for overall system stability. This controller is based on a linear program (LP) and assigns wheel slips for each wheel in accordance with one of the following criteria: 1) During an emergency braking maneuver, optimal wheel slips are determined which maximize stopping while constraining the system to be stable, or 2) During a nonemergency braking maneuver, the controller is used to maximize stability while maintaining an achievable (commanded) deceleration.
Computer simulations, which modeled a full tanker truck, were run to compare the response of the proposed controller with two controllers which incorporated select-low control and individual control ABS systems on various axles. Emergency braking responses in the following maneuvers were compared: constant turn, straight line split mu surface, and constant turn on a split mu surface. The LP controller showed itself to be a superior controller, especially in the last simulation where it was the only controller able to maintain tractor/trailer stability.
Due to the control system complexity and extensive sensor requirements, implementation of the proposed controller would currently be practical only on specialized vehicles. But the simulation results presented here seem to justify the expense.