Research And Development On Electromechanical Valve Actuation

Future requirements of the legislative on the reduction of exhaust emissions of motor vehicles combined with the demand of automotive clients for lower fuel consumption and excellent noise, vibration and harshness (NVH) behavior force the automotive industry to realize the pressing need for clean and efficient internal combustion(IC) engine. Conventional internal combustion engines use mechanically driven camshafts to actuate intake and exhaust valves. While this system is convenient and reliable, the fixed timing of the valve events with respect to the piston motion is typically selected as a compromise among fuel economy, emissions, maximum torque output and NVH. The well-tuned mechanically connected parts in IC engine of the past are transformed to electronically controlled mechanisms that provide many degrees of freedom for performance optimization. Electromechanical valve actuation(EMVA) as a promising camless valvetrain can completely eliminate the cam-crank shaft mechanical linkage allowing for a wide continuously variable valve timing(VVT).Through the use of VVT, engine operation can be optimized in fuel economy, performance and emissions. Abroad vast researches have been made in the area of EMVA at structure design and control strategies and still being continuing due to some problems to deal with. It is far away from production.This dissertation investigates EMVA on the basis of large numbers of references and experiences,and combines the real situation of the project which is cooperating with Wuxi Fuel Injection Equipment Research Institute.A comprehensive research pattern,the integration of analysis,simulation.test and manufacturing^ applied to develop EMVA with high performance which establishes a basis for the practicability and production.Main works are as following:(1) Static mathematic model of solenoid valve is provided by use of approximate magnetization curve.The static model is advantageous to the structure, mechanism design and parameter optimization of solenoid valve.(2 ) The dissertation builds the dynamic model of solenoid valve and combines the digital simulation to design high-speed solenoid valve for EMVA. The design principle of solenoid valve is put forward. The factors are analyzed which affect the dynamic response such as driving voltage, moving mass, spring stiffness, spring preload force, coil turns, coil resistance and armature stroke. The effective methods for solenoid valve switching with high speed andpowerful force are provided.(3) Based on analyzing operating principle and working process,A two-magnet,two-spring EMVA system is firstly developed whose core is made of rectangular overlapping silicon sheets so as to reduce the effects of hysteresis and eddy currents of ferromagnetic materials and fall down the coils' heat.Holes are bored in the armature to decrease moving mass and reduce air damped effects.Additionally,residual air-gap is considered to lessen the influence of mechanical err and leakage inductance on EMVA.(4) Dynamic experimental setup matching with EMVA is developed and static and dynamic test are conducted.A control strategy which is open-loop control by adjusting coil current is used to decrease landing velocity.Experiments are performed to investigate the current sequence and its effect on the landing velocity. The practicability of EMVA and the feasibility of control system are furture validated.(5) A basic nonlinear model for EMVA is developed allowing for magnetic material properties including magnetic saturation,hysteresis and mutual induction and using magnetization curve of magnetic material.The sliding mode methodology is used since it is nonlinear,robust to uncertainties,and easier to design and implement to control landing velocity of EMVA. Simulation results show that the sliding mode control can accomplish quick and accurate tracking to the desired trajectory ,achieve soft-landing.The metrical problems of valve position and velocity are resolved by using of silding mode observer.electromechanical valve actuation(EMVA); camless engine;variabl...