Transient Control Strategy of Hybrid Electric Vehicle during Mode Change 2009-01-0228

Transient control for EV/HEV mode change takes an important role in the system of the parallel HEV, which consists of internal combustion engine (ICE), electric motor (EM), integrated starter & generator (ISG), battery, automatic transmission and clutch (that replaces the torque converter), not only ICE/EM control but also clutch engagement control are the key of it. To improve the mode change performance, this study proposes clutch slip control methods. Method 1. focuses on the open loop clutch pressure control so as to adjust target clutch transfer torque. The main idea of Method 2. is to control the clutch pressure in order to achieve the desired speed difference(Method 2-1) from each side of clutch when motor speed is faster than engine idle speed and keep target engine speed(Method 2-2) when motor speed is slower than engine idle speed. This paper defines control sequence which is scheduling the behavior of powertrain components as well. Vehicle dynamic model was implemented and simulation was carried out regarding the various driving circumstances. By means of selecting better control method with respect to the driving atmosphere based on the simulation result, transient control strategy could be built. Consequently, control stability and drivability were able to be achieved through this strategy.