Adaptive Continuously Variable Compression Braking Control for Heavy-Duty Vehicles

Modern heavy-duty vehicles are equipped with compression braking mechanisms that augment their braking capability and reduce wear of the conventional friction brakes. In this paper we consider a heavy-duty vehicle equipped with a continuously variable compression braking mechanism. The variability of the compression braking torque is achieved through controlling a secondary opening of the exhaust valve of the vehicle’s turbocharged diesel engine using a variable valve timing actuator. A model reference adaptive controller is designed to ensure good vehicle speed tracking performance in brake-by-wire driving scenarios in presence of large payload and road grade variations. The adaptive controller is integrated with backstepping procedure to account for compression braking actuator dynamics, with observers for various unmeasured quantities and with compensation schemes for actuator saturation. In addition to speed tracking, the vehicle mass and road grade are simultaneously estimated if persistence of excitation-type conditions hold. The final version of the controller is successfully evaluated on a high order crank angle model of a vehicle with a six-cylinder engine.