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Electro-pneumatic valve actuators are used to eliminate the cam shaft of a traditional internal combustion engine. They are used to control the opening timing, duration, and lift of both intake and exhaust valves. A physics based nonlinear mathematical model called the level one model was built using Newton's law, mass conservation and thermodynamic principles. A control oriented model, the level two model, was created by partially linearizing the level one model for model reference parameter identification. This model reduces computational throughput and enables real-time implementation. A model reference adaptive control system was used to identify the nonlinear parameters that were needed for generating a feedforward control signal. The closed-loop valve lift tracking, valve opening and closing timing control strategies were proposed.

This paper addresses the design and detailed modeling of a novel electronically controlled, pneumatic/hydraulic valve actuator (EPVA) for both the engine intake and engine exhaust valves. The valve actuator's main function is to provide variable valve timing and variable lift in an automotive engine. The design of the combination of pneumatic and hydraulic mechanisms allows the system to operate under low pressure with an energy saving mode. A system dynamics analysis is provided and is followed by a mathematical model. This modeling approach uses the Newton's law, mass conservation and thermodynamic principles. The air compressibility and liquid compressibility in the hydraulic latch are modeled. The discontinuous nonlinearity of the compressible flow due to choking is carefully considered. Provision is made for the nonlinear motion of the mechanical components due to the physical constraints.