F2010A075
Anti-jerk Control Strategy for Parallel Hybrid Electric Vehicles
The parallel hybrid electric vehicle(HEV) which employs a clutch between an internal combustion engine and a transmission-mounted traction motor is regarded as one of effective HEV configurations since it can reach a high level of hybridization with relative small modifications of the layout and components from conventional vehicles. In this configuration, EV(Electric Vehicle) mode can be realized by disengaging the clutch. The EV mode, in which propulsive or regenerative torque is delivered by the traction motor through the transmission, plays an important role in improving efficiencies of low load driving and regenerative braking. In the EV mode, however, jerk can be induced by backlash since there are insufficient physical damping elements in the driveline. Though the jerk gives demoralizing influence upon driving comport in the form of shock and oscillation, adding a physical damper is not applicable due to constraints of the layout. This study suggests an anti-jerk strategy to suppress the jerk in the EV mode driving without any modification of the hardware. The strategy is composed of three approaches; passive damping, active damping and torque profiling method. The passive damping method generates the physical damping elements by controlling the clutches of the automatic transmission. For a moment when the jerk is expected, clutch slip can be generated by reducing clutch control pressure and the slip friction force can absorb the jerk. The active damping method gives absorbing torque in the opposite direction of the oscillation using the traction motor. In this method, the amplitude and direction of the oscillation can be estimated by comparing the observed speed from the motor resolver with the target speed from the vehicle load model. The last approach, the torque profiling method deforms traction torque to reduce the jerk itself. The moment the direction of the traction torque is reversed, the jerk can be reduced by limiting the gradient of the input torque since the magnitude of the jerk is proportional to an impulse which occurs during the contact of mated gear teeth is re-established in reverse direction, Since the suggested methods are based on system parameter modification, feed-back control and feed-forward control respectively, they are expected not to give interferences one another. In this study, tests on jerk reduction performance, torque response and robustness are carried out for the each method and possible combinations of the methods. Through the tests, each method is tuned to show the best performance and the most effective combinations are suggested. The suggested anti-jerk strategy is expected to improve driving comport with minimum cost.
This abstract is supplemented by a PDF, which can be viewed here.
Session: Alternative Drivelines