Model-based control of electro-pneumatic intake and exhaust valve actuators for IC engines.

摘要

Variable valve actuation of Internal Combustion (IC) engines is capable of significantly improving their performance. Variable valve actuation can be divided into two main categories: variable valve timing with cam shaft(s) and camless valve actuation. For camless valve actuation, research has been centered in electro-magnetic, electro-hydraulic, and electro-pneumatic valve actuators. This research addresses the detailed modeling and control of a novel electronically controlled, pneumatic-hydraulic valve actuator (EPVA) for both the intake and exhaust valves of an IC engine. The valve actuator's main function is to provide variable valve timing, lift and duration of the intake and exhaust valves of an IC engine. A system dynamics analysis is provided and followed by a mathematical model. This modeling approach uses Newton's law, mass conservation and thermodynamic principles. A control oriented model was developed to reduce computational throughput for real-time model-based control implementation. Simulated model responses were found to be in satisfactory agreement with experimental results. For intake valves, an on-line model reference adaptive system identification technique was employed to estimate system parameters required for closed-loop adaptive control; and an adaptive valve lift control strategy was developed to reduce both transient and steady-state lift tracking error. Unlike the intake valves, the exhaust valve opens against an in-cylinder pressure that is a function of the engine operational conditions with cycle-to-cycle combustion variations. This pressure disturbance slows down the valve actuator response and increases the variation of valve lift and opening delay. The developed control strategy utilizes model based predictive techniques to overcome the randomly varying in-cylinder pressure against which the exhaust valve opens. Both intake and exhaust valve control strategies were performed on a Ford 5.4 liter 3-valve V8 engine head at different operating conditions. Experimental results were used to validate the control strategies.