Robust Design of a Valve Train Cam Phasing Controller using Virtual Prototyping Techniques

Cam phasing, or Variable Valve Timing (VVT), is an electro hydraulic and mechanical camshaft control concept managed by the vehicle's microcontroller engine management system. Development and implementation of cam phasing mechanisms is pursued by the automotive industry today because it gives measurable increase in performance, and reduction in undesired engine emissions. This paper illustrates the usage of virtual prototyping techniques to efficiently investigate cam phasing architecture control algorithm implementation to permit more robust cam phasing design. The control algorithm implementation resides in Simulink, and the virtual prototype of a complete hydraulic vane cam phaser system resides in a selected analog mixed technology simulator. Co-simulation enables the two different simulation engines to communicate, hence dynamic controller development can commence against virtual hardware. Cam phaser response is heavily dependent on engine oil temperature and pressure. As a specific conceptual example, a simple initial controller is developed that does not consider oil temperature and pressure fluctuations. An enhanced more robust controller is then implemented to account for these system variances. The ability to develop the entire control algorithm in a tool suited for that purpose, and then to test the controller with a highfidelity system plant modeled in another simulation environment is illustrated using robust engineering techniques.