The Non-steady-state Simulation Of Engine Output Torque And Mounting Loads

Vehicle dynamic simulation technique is a powerful tool for autodesign and production. As a general technique to increase nationalcompetition, it's the international research focus for decades.The simulation technique key part is that vehicle dynamic modelhas RTS (real time simulation) and high fidelity. The engine is not onlythe source of power but also the primary NVH source of the car. So wemust build a real time engine dynamic model before building a precisevehicle dynamic model.When driving the driving simulator, the driver will change theaccelerate pedal and shift leveler according to the traffic conditionssubconsciously, so the engine run randomly and continuously. At thesame time, the working cycle of the engine is a transient course ofwhich the periodicity is 720 degrees of the crank angle and in oneworking cycle, the engine output and rotator speed will change with thechange of the crank angle. So only when building the transient enginemodel, can we supply the vehicle dynamic model with precise powerand simulate the influence of the engine vibration on the vehicledynamic with transient excitation force which the engine acts on the carbody or frame.The dynamic model of the complex system can be built usingmulti-body dynamic theory, and there are lots of commercial soft wareslike ADAMS, DADS. But multi-body programs employ nonlineardifferential-algebraic equations that require iterative solution methodsthat run slowly and with variable time steps. It usually wastes someweeks to solve one condition. So this kind model is not suitable for fullvehicle dynamic design and optimization. So the dissertation tries tobuild a non-steady engine dynamic model that can real-time simulateand is suitable for our Driving-Simulator. The main contents andconclusions of the dissertation are as follows: (1) Based on the character of the engine burning pressure signal, thedissertation proposed the three-dimension interpolate algorithm withaccelerate aperture, engine rotator speed and crank angle position usingengine burning pressure of the neighbor engine rotator speed andaccelerate aperture in the typical operating condition to obtain thepressure in the non-typical operating condition. This kind of interpolatealgorithm ensured the continuity and periodicity of the change ofengine burning pressure according to the change of the crank positionsand supply the engine dynamic model with precise input of pressure. (2) For real time simulation and based on complex constraint, thedissertation converted the mass of connecting rods using the principleof dynamic equivalent and made the piston dynamic and the crankshaftdynamic uncoupled. Comparing traditional multi-body model, themodel solves the Differential Algebraic Equations problem, so thesimulate speed is improved. At the same time, the dissertation also didsome research on real time simulation algorithm and used linearADAMS-BASHFORTH algorithm solving engine dynamic equationsand realized real time simulation. For structure-oriented simulation, the dissertation defined the singlecylinder engine as a subsystem and a multi-cylinder engine consist ofsome subsystems through connections in the crankshaft. All subsystemswere built in the relative reference frame. So we can build differentkinds of engine dynamic models through adding or reducingsubsystems and modifying some parameters. Although the mechanical efficiency of engines changes with thechange of the structures and operating conditions, it is not very high.For improving simulating precision the dissertation built a transient...