Nonlinear Regulation of Electromagnetic Valves for Camless Engines

Abstract

Conventional internal combustion engines use mechanical camshafts to command the opening and closing phases of the intake and exhaust valves. The lift valve profile is designed to reach a good compromise among various requirements of the engine operating conditions. In principle, optimality in every engine condition can be attained by camless valvetrains. In this context, electromagnetic valves offer an interesting solution, although there are still some relevant open problems to be solved before they can be introduced in production. In fact, to eliminate acoustic noises and avoid damages to mechanical components, the control specifications require sufficiently low impact velocities between the valve and the constraints (typically the valve seat), so that "softlanding" is obtained. In this paper, the soft-landing problem is translated into a regulation problem for the lift valve profile, by imposing that the valve position tracks a desired reference, while the modeled disturbances are rejected. Both reference and disturbance are generated by an autonomous system, usually called exosystem. The submanifold characterized by the zeroing of the tracking error and the rejection of the disturbance, is determined. Finally, the stabilization problem of the system trajectory on this manifold is solved using state feedback.