Control of Electromechanical Actuators: Valves Tapping in Rhythm

Abstract

Electromechanical valve (EMV) actuators can replace the camshaft allowing for electronically controlled variable valve timing (VVT) on a new generation of engines. Through the use of VVT, engine operation can be optimized to allow for improvements in fuel economy, performance, and emissions. Before EMV actuators can be used in production vehicles two critical problems need to be resolved. First, impact velocities between the valve, valve seat, and the actuator itself need to be small to avoid excessive wear on the system and ensure acceptable levels of noise. Second, the opening and closing of the valve needs to be both fast and consistent to avoid collision with the piston and to reduce variability in trapped mass. An extensive control analysis of the EMV actuator and the control difficulties are presented. Finally, a linear, a nonlinear, and a cycle-to-cycle self-tuning controllers are designed and demonstrated on a benchtop experiment.