Feedback and Feedforward Control for Electrohydraulic Valve Systems Using a Novel System Identification Technique

Abstract

ElectroHydraulic Valve Systems (EHVS) have the ability to vary valve profiles of internal combustion engines on a per cycle basis, thus allowing one to optimize the combustion process and improve its efficiency and emissions characteristics. Such a capability makes an EHVS system a very suitable actuation mechanism for novel combustion strategies. However, designing a controller which ensures that the EHVS executes the desired valve profiles is challenging due to the required fast response time, the inherent non-linearity of the system, and the time delays associated with the servo valves, actuators and the interconnections. In this paper, we explore a systematic and semi-automatic way to design a controller for an EHVS. The controller has a feedforward and feedback structure. The feedforward controller is obtained by using an on-line system identification scheme, while the feedback controller is based on an off-line system identification model. This procedure is applied successfully to a laboratory EHVS engineered by Team Corporation covering the full range of engine operating speeds from 500 to 4000rpm.