Periodic Servo-loop Control Of Heavy-duty Trucks For Minimizing Fuel Consumption

Optimizing the fuel consumption of heavy-duty trucks by Adaptive Cruise Control systems gains focus regarding to worldwide increasing demands on road freight transportation.Since trucks are on the one hand use intensive resulting in a large number of vehicle miles traveled,and on the other hand energy intensive,small improvements have a strong impact.The fuel consumption of heavy-duty trucks is strongly influenced by the technique it is operated.Periodic Pulse-and-Glide operation,in which the vehicle is accelerated in the engine's efficient load point and then coasts in neutral or higher gear,has shown promising fuel saving potentials.To address these,this research studies cooperative control of engine and powertrain in a Pulse-and-Glide control framework,and further evaluates the controller performance by simulation.Succeeding the design of fuel optimal engine operation,the algorithm of the Pulse-and-Glide controller is designed to ensure operation in the most fuel economic region in pulse mode,glide in neutral mode,and to guarantee that a desired range boundary is met depending on given preceding vehicle speed,acceleration and intervehicle range.The controller handles gear selection and engine torque to periodically accelerate and decelerate in fuel optimal way.(1)For the purpose of defining fuel optimal engine operation,the special characteristics of the given engine map and the definition of optimal brake specific fuel consumption operation points are taken into account.An injective line consisting of most fuel efficient operating points is designed and employed in the controller algorithm.(2)The optimal gear and torque algorithm scheme is based on the average power used to maintain a given constant speed determined by vehicle longitudinal dynamics.The optimal gear and torque for the accelerating pulse mode are then found in such a way that the average fuel consumption of Pulse-and-Glide operation is less at equal average power used.As further improvement,a torque optimizer is used to lock up engine operation along the most fuel efficient operating points for the entire pulse operation.(3)A two dimensional hysteresis to switch from pulse to Glide mode and vice versa is build depending on discrepancy from desired inter-vehicle distance and preceding vehicle velocity.The switching logic takes the longitudinal dynamics of the vehicle itself,the preceding vehicle speed and acceleration as well as the velocity depending desired inter-vehicle distance into account.To address model mismatch,the controller range bounds of the Pulse-and-Glide maneuver are adjusted by a regulator in order to meet the driver desired range bounds.Additionally,a preceding vehicle velocity prediction scheme improves switching performance for varying preceding vehicle speed situations.(4)The Pulse-and-Glide controller performance is evaluated with regard to scenarios where the preceding vehicle maintains a constant speed and to scenarios where the preceding vehicle follows a modified HHDDT drive cycle.The respective range bounds are met by the controller in both cases.It is found that the designed line of fuel optimal operation is outperforming a manufacturer given operation line in speed range up to 82.5 km/h.The torque optimizer generally improves fuel economy.In comparison to constant speed cruising,the fuel consumption of Pulse-and-Glide is improved by almost 5 % for a preceding vehicle speed of 80 km/h.In case of the preceding vehicle tracking the modified HHDDT drive cycle at a mean velocity of 80 km/h,the fuel improvement of Pulse-and-Glide operation reaches a level of 2.3 %.