Computer-controlled synchronization of internal combustion of engine valves by means of a hydraulic actuation.

摘要

An ideally adjustable valve timing could improve the fuel economy, power, torque, idle quality and exhaust cleanness of an internal combustion engine (ICE).; This dissertation proposes and analyzes a new concept of hydraulic actuation and synchronization control for ICE valves. The design goal is to conceive a simple and efficient system to actuate the engine valves in a manner compatible with present automotive applications. The most distinctive feature of the proposed design is that the actuation system itself enforces all the mandatory kinematic features of an ICE valve motion. To achieve this, a specially designed hydraulic actuator limits the ICE valve opening and seating velocity. Noteworthy, a mechanical spring prevents the excessive opening of the engine valve and a hydraulic damping device (a conical edge orifice plate) guarantees smooth seating. Consequently, the control system's sole task is to force the opening and closing of the ICE valves to occur at desired angular positions of the engine shaft. The final result is that the control algorithm becomes extremely simple. The complete system comprises a hydraulic actuation system and the electronic control system. The actuation system's three main components are: (1) a conventional hydraulic power supply; (2) the specially designed linear actuator and; (3) electrically actuated on/off hydraulic valves that interface with the computer based control system. The proposed system offers complete flexibility over the engine valves opening and closing timing, but works with a fixed value of lift.; The hydraulic actuation system is designed with the help of a computer simulation, assuming a common automotive spark ignited (SI)-ICE. The dynamic model includes one actuator and two hydraulic valves, with a total of six states. The compressibility of the hydraulic fluid and pipes are considered and the differential equation describing the hydraulic pressure is solved through a first order backwards differentiation algorithm.; The distinctive charactehistic of the design is that the actuation system carries out tasks that normally would be accomplished by the control system.; Motivated by the self-tuning controller, Chapter V is devoted to the theoretical study of recursive identification of parameters of dynamic systems. (Abstract shortened by UMI.)