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This paper presents an overview of the LucasVarity Vehicle Simulation Laboratory and its capabilities and benefits to the company's development of brake and brake control systems for the automotive industry. LucasVarity has been using simulation in its product development process since 1991. Two types of simulation are currently used: open loop and closed loop. The Open Loop Simulator (OLS) is a sensor signal design tool and real-time transmitter used primarily to test brake control system algorithms. Closed loop simulation (CLS) includes two levels: non-real-time desktop simulation (CLSDT) or real-time with hardware in the loop simulation (CLSH). Both levels use a vehicle model, designed by LucasVarity engineers, which is currently solved for eighteen degrees of freedom representing three-dimensional vehicle dynamics. Hardware in the loop simulation is performed on the CLSH and may include a brake fixture mounted in a laboratory hydraulic chamber or an entire vehicle.

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.