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This paper will discuss the design and simulation of an electro-mechanical valve timing (EMVT) system for IC engines. The system consisted of a rotary actuator for converting an electric signal to rotary motion and a rocker arm to convert the rotary motion to valve movement. The design of this system included specifying the characteristics of the rocker arm, the actuator's armature moment of inertia, the field windings and the controller. The simulation of the complete system was done using the Advanced Continuous Simulation Language (ACSL) to execute a model that consisted of a controller in a feedback loop with a bond graph model of the actuator and rocker arm. The simulation showed the motion of the valve as a function of actuator input voltage and time for various engine speeds. Performance was measured by the overall time the valve was opened and a comparison was made with an existing valve systems.

The response of an overhead cam valvetrain system has been accurately simulated using the Advanced Continuous Simulation Language (ACSL). This approach is unique by using a software program to solve the system equations while others have derived codes to perform these calculations. Simulation variables include cam lift velocity function, valve spring stiffnesses and damping coefficients, stiffnesses of other valvetrain components, and cam speed. Simulated results closely agree with actual valvetrain test data. Natural frequencies obtained from the valvetrain simulation match those predicted by spring design theory and finite element analysis. Since the cam lift function and other components' properties are easily modified, this computer simulation simplifies the task of designing valvetrain systems by providing meaningful and reliable system response predictions quickly.