Development of Force Compensation Models for the Cycle-by-Cycle Soft-Landing Control of an ElectroMechanical Valve Actuator

A type of Electro-Mechanical Valve Actuator (EMVA) formed by two opposed electromagnets and two balanced springs has been widely studied in literature in the last decade since it seems to be a promising solution for implementing advanced engine combustion concepts based on VVA (Variable Valve Actuation) systems. In fact, their use can increase engine power, reduce fuel consumption and pollutant emissions, improving significantly engine efficiency Nevertheless, strongly nonlinear behavior characterizing these actuators coupled to variations of plant parameters and external forces as well make the control problems very challenging. Among other, we have focussed the attention on the Soft Landing Control (SLC) guaranteeing a soft approach of the engine valve to its valve seat with limited impact velocities. In this report, the results of a numerical study aimed for making more robust a pre-existing closed-loop SLC strategy are presented. Different force compensations approaches are explored and the analysis is done in the basis of a nonlinear map that characterizes the system output (i.e. seating velocity) with respect to an adimensional gain under study. The idea behind our approach is to identify a new control knob that an external cycle-by-cycle control adaption law uses to reduce valve seating velocities. Finally, a PI-based cycle-by-cycle learning algorithm is proposed to show the effectiveness of the compensation approach via numerical simulations.