Analysis and Compensation Control of Engine Valve Response Delay Based on the Electro-Hydraulic Variable Valve Actuator

The time delay of variable valve actuators has a significant influence on engine valve lift tracking performance. For camless hydraulic valve actuators, engine valve response is affected by many factors, such as friction and control valve response. In this paper, engine valve response delay is investigated in depth. Experiment results show that engine valve motion delay can be divided into valve open delay and valve close delay. They are different even in the same engine cycle. Complicated delay characteristics make it difficult to build an accurate delay model. In this paper, a data-based delay observer is developed. To compensate the nonlinear valve delay, the virtual desired valve lift is designed. By synthesizing the virtual valve lift into the backstepping procedure, an engine valve lift tracking controller with delay compensation is developed. Compared with the P controller, the backstepping controller with delay compensation improved the engine valve lift tracking performance significantly. The experiment results show that the valve open error can be reduced by 18.33% and the valve close error can be reduced by 4% at least both at stable conditions and transient conditions. At stable conditions, the valve open error is not more than 0.39 °CA, and the valve close error is not more than 0.44 °CA.