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Non-linear control of electromagnetic valves for camless engines

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 in order 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 appear to be promising, although there are some relevant open problems. In fact, in order to eliminate acoustic noises and avoid damage to the mechanical components, the control specifications require sufficiently low impact velocities between the valve and the constraints (typically the valve seat), so that “soft-landing” 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 modelled disturbances are rejected. Both reference and disturbance are generated by an autonomous system. 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 such a manifold is solved.