The electromagnetic valve actuator (EMVA) is considered a technological solution for decoupling between crankshaft and camshaft to improve engine performance, emissions, and fuel efficiency. Conventional EMVA consists of two electromagnets, an armature, and two springs has been proved to have the drawbacks of fixed lift, impact noise, complex control method and large power consumption. This paper proposes a new type of EMVA that uses voice coil motor (VCM) as electromagnetic valve actuator. This new camless valvetrain (VEMA) is characterized by simple structure, flexible controllable and low actuating power. VCM provides an almost flat force versus stroke curve that is very useful for high precision trajectory control to achieve soft landing within simple control algorithm. The halbach magnet array and coil structure are specially optimized to provide flux-focused interleaved magnetic circuits for maximizing the actuating force. 2D and 3D magnetic simulation is applied to analyze the performance of VEMA. A cascade feedback with velocity and acceleration feedforward control structure is developed. Two cascade PID feedback controllers are used to realize the position and current loop and the feedforward controller is applied to enhance the trajectory tracking performance by utilizing the information from the repeated precognition reference trajectory. Simulated and experimental results indicate that the proposed VEMA and the control methodology are capable of achieving fully flexible valve motion with low seating velocity and power consumption.
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