Vehicle gear shifting strategy optimization with respect to performance and fuel consumption

Abstract

Based on the movement resistance forces, the vehicle longitudinal dynamics is related to power demand for a specific route. The vehicle gear shifting influences significantly the acceleration performance and fuel consumption because it changes the engine operation point and the powertrain inertia. This paper presents a study based on the US06 velocity profile which involves high speed and high acceleration phases, where the vehicle performance is limited by both the engine power and the tire traction limit. For improving A c c e p t e d M a n u s c r i p t the vehicle performance without increasing fuel consumption, a genetic algorithm (GA) technique is used.

Energy storage and control optimization for an electric vehicle

“…The main reason for the rear propelling EMs be used as primary drive system is related to the tire traction limit that varies according to the vehicle accelerations (by the EMs) that transfer load from the frontal to rear vehicle axis, decreasing the transmissible torque in the frontal wheels and increasing the limit for the rear wheels. This decrease in the frontal drive transmissible torque was pointed out in a previous study 30 as the principal cause of poor performance in frontal drive vehicles when they are submitted to high accelerations (especially at the startup) as in the US06 cycle. Therefore, the use of the rear drive system presents a better strategy regarding performance, once the frontal EMs only fulfill the remaining torque demand, a condition in which the traction limit is not frequently reached.…”

Fuel consumption and emissions analysis for a hybridized vehicle

“…The vehicle traction limit is modeled as proposed in [11], as a function of the weight force acting on the vehicle axes, which may vary with the load transfers when the vehicle accelerates or brakes. Equations 7and (8) show the maximum transmissible torque at the front N5OP ) [Nm] and rear 5OP ) [Nm] wheels, according to the tire-ground peak coefficient of friction (C) and to the parameters related to the vehicle geometry.…”

“…The PHEV model also respects the tire traction, the clutch transmissible torque and the torque constraints of the propelling systems. For the PHEV, the calculation is similar to the one presented for the conventional vehicle, but the Equation 5is replaced by the Equation 14, and the acceleration is then calculated by the Equation 15 (13) and the maximum transmissible torque at the vehicle rear wheels calculated by the Equation (8). In this case, the interactive algorithm that defines the vehicle acceleration uses the Equations (7), (8), (12), (13), (14), (15) and (16).…”

“…The gear shifting strategy influences the vehicle acceleration performance and also fuel consumption because it changes the powertrain inertia and the engine speed [8]. During the simulations, a standard gear shifting strategy proposed by [12] defines the vehicle speeds for which the changes of each gear must happen.…”

“…During the simulations, the gear shifting time of 1 second was adopted, as proposed by [7]. The gear shifting process is defined by [8] that set 0.3 s to complete engine decouple from the gearbox, followed by 0.2 s to change the gearbox transmission ratio, and 0.5 s to gradually recoupling the clutch discs, increasing the transmittable torque until it reaches the engine output torque. The clutch transmissible torque during the gear shifting process ( @A ) [Nm] is defined by the Equation (6), as given by [9].…”