The Simulation Design And Control Optimization Of The Electro-Hydraulic Camless Valvetrain System

As a new combustion mode, Homogeneous Charge Compression Ignition not only hascombined the benefits of the gasoline engines and the diesel ones and overcome thedisadvantage of the low efficiency caused by non-homogeneous diffusion combustion intraditional engines and made the mixture well evenly distributed, but also has reduced thefuel consumption and has the potential to improve both the efficiency and emission ofengines, especially can reduce nitrogen oxides (NOX) emissions by90%–98%.The technology of electro-hydraulic control camless valvetrain is one of the methodsto achieve HCCI combustion mode by controlling the inner exhaust gas recirculation(EGR) rates. This paper took the modified ZS1105single cylinder engine as the test bed,and HCCI combustion mode was achieved through replacing the camshaft valvetrainactuator with electro-hydraulic variable valvetrain actuator system. The flexible control tothe valvetrain and the accomplished switch between the sparker ignition (SI) combustionmode and the homogeneous charge compression ignition (HCCI) combustion mode werevalidated through experiments.First of all, the development of variable valvetrain was summarized and introducedbriefly in this paper. The electro-hydraulic control camless valvetrain was theoreticallyanalyzed combining with the test model, and the parameters that can effect the valvetrainmovement were derived. A hydraulic simulation model was built by AMESim andparameters of this model were given. The model was validated by experiment data andsuitable hydraulic components were chosen through the demands of the experiment.Secondly, a simulation test bed had been set up by Matlab-GUI (Graphical UserInterface), and the effect parameters had been listed in this interface. The aim to controlthe model was realized by setting the parameters, and the greater effect coefficients thateffect the valvetrain movement were analyzed, including diameters of the upper piston,large diameter of the lower piston, diameters of the orifices, position of the oil port. Theeffects of different parameters were obtained by the function of Design Exploration ofAMESim, and this could be useful for the future optimization.Finally, according to the higher speed of the valve during opening and closing, closedloop PID control of the valve speed was raised. The closed loop was based on the originalopen loop control system, and realized the closed loop control to the valve speed throughcontrolling diameters of the orifices. The reasonable PID parameters had obtained byoptimization design function of AMESim, and also had been applied to the model. Thesimulation results had showed that the speed was0.097m/s at the moment of opening fully,0.096m/s at the moment of landing, both below0.1m/s, and justified that the optimizedPID parameters could meet the demands of the engine. Moreover the reasonable PIDparameters were obtained by the function of the optimization of AMESim, and thisprovided a convenient solution to the future choice for PID parameters.