Research on the Pollutant Reduction Control for P2.5 Hybrid Electric Vehicles

The strategy for emission reduction in the P2.5 hybrid system involves the optimization of engine torque, engine speed, catalyst heat duration, and motor torque regulation in a coordinated manner. In addition to employing traditional engine control methods used in HEV models, unique approaches can be utilized to effectively manage emissions. The primary principle is to ensure that the engine operates predominantly under steady-state conditions or limits its load to regulate emissions levels. The main contributions of this paper are as follows: The first is the optimization of catalyst heating stage. During the catalyst heating stage, the system divides it into one or two stages. In the first stage, the vehicle is driven by the motor while keeping the engine idle. This approach stabilizes catalyst heating and prevents fluctuations in air-fuel ratio caused by speed and load changes that could potentially worsen emissions performance. The second stage corresponds to when the engine-driven vehicle heats up its catalyst. The second is the engine control optimization which includes the idle speed control, the minimum intake pressure controls and the oxygen storage capacity control. The third is the motor control optimization. Motor power or power generation can be employed to restrict or stabilize engine load within a certain range so as not to impact original emission levels due to load variations. Start-stop control may also be implemented during this stage but should avoid frequent start-stop cycles until during catalyst heating phase. To prevent emission deterioration caused by frequent start-stop events during the catalyst heating, the calibration of the power threshold in energy management module becomes necessary for minimizing subsequent restarts of the engine; thereby improving overall emissions performance. Experimental results demonstrate that implementing this emission management control approach reduces fuel consumption by 37.6% compared with the traditional vehicles.