Researches On Systems Modeling And Air Fuel Ratio Control For A Spark Ignition Coal-bed Gas Engine

As a kind of new clean source of power, coal-bed gas is an ideal alternative fuel instead of gasoline used for engines. The electronic control techniques are effective ways to meet control demands of the coal-bed gas engine drive-ability, economy and exhaust emission level in equilibrium and optimization. Air fuel ratio control is a main investigation content of integrated control for the coal-bed gas engine. It is important to improve combustion quality and to give full play to advantage of combustion feature and effect of low emission of coal-bed gas.This thesis introduces author's researches on the issues related to air fuel ratio control of the coal-bed gas engine. The achievements are present as follows.(1) A scheme of air fuel ratio control with two-valves is put forward to reform electronically controlled configurations of the coal-bed gas engine. A compression ignition engine is rebuilt into a spark ignition coal-bed gas engine. The required supplementary and a variety of experimental facilities are developed and large numbers of experiments are carried out under different operating conditions.(2) A mean value model of coal-bed gas engine is established based on the steady-status experimental data and the physical characteristics of the engine. A simulation model with graphics is built by means of MATLAB/SIMULINK tools, and verified using the experimental data under different operating conditions.(3) The calibration equipments are developed to test the static and dynamic characteristics of engine Manifold Absolute Pressure (MAP) sensor and thermal type Mass Air Flow (MAF) sensor. The experimental apparatus is configured for evaluating the performances of Exhaust Gas Oxygen (EGO) sensor. The nonlinear dynamic models of both hot wire/film type MAF sensors and EGO sensor with block-oriented structure are established by the two-stage identification method, separately.(4) According to hypothesis of intake average stationary flow, using experimental data on engine test stand, a hierarchical model is built up to use for steady-status air fuel ratio feed-forward control. Three-dimensional original control maps are produced by the model, and data generation problem of non-experiment operation condition points is solved. Adopting iteration learning control techniques, steady-status air fuel ratio correcting algorithms by means of adjusting single valve and adjusting two valves are studied, and the convergence of different algorithms is examined.(5) Aiming at nonlinear dynamic relationship between control input and control output, on the basis of the engine delay between gas charging process and exhausting process, a slide mode observer is constructed to measure intake air flow and fuel gas flow and exhaust air fuel ratio at the same time. Its accuracy is validated by experiment data under dynamic operation conditions. An air fuel ratio parallel control structure is proposed for the coal-bed gas engine, which combines neural network control with PID control. A transient-status air fuel ratio control algorithm is studied, and the control effect is verified by the simulation.