A Gradient Descent Control Approach for 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. In this regard, we 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, a cycle-by-cycle control algorithm is proposed to reduce the landing velocity of the valve against its seat. The idea is to modify a preexisting Sliding Mode Controller (SMC) adding a further control action which is updated at each engine cycle. The extra control action is obtained by exploiting the gradient descent method to derive a control algorithm that allows always to reach the minimum impact velocity despite. The effectiveness of the cycle-by-cycle adaptation strategy is validated in a high predictive numerical simulator of the EMVA system when considering perturbed scenarios.