Mode Transition Control of a Power-Split Hybrid Electric Vehicle Based on Improved Extended State Observer

In order to improve the mode switching stability of a power-split hybrid electric vehicle (HEV), a torque coordinated control strategy based on disturbance observation and compensation is proposed. Aiming at the problem of engine torque disturbances caused by engine modeling error, torque control error, working environment interference and other factors, and vehicle load torque interference caused by changes in vehicle driving conditions, an improved linear extended state observer (ILESO) is designed at first. According to the deviation control principle, the state variable regulation mechanism using the same error term in the traditional linear extended state observer (TLESO) is revised, and improved by adding the corresponding deviation between the state variable and its observed value separately. Then the Lyapunov stability of the error system for the ILESO is proved gradually. On this basis, a torque redistribution algorithm of two motors based on disturbances compensation is put forward. After that, simulation verification and road adaptability analysis are carried out subsequently. The results show that the coordinated control strategy based on ILESO, compared with the TLESO, has higher observation accuracy, and makes the HEV have better vehicle speed tracking stability and mode switching smoothness when the vehicle is subject to the same external disturbance, as well as excellent adaptability under a wide range of road conditions.