Modeling Of Engine In All Operating States Applied To Simulation Of Vehicle Dynamics

Development-oriented automobile driving simulator is an important part of vehicle dynamics simulation technology. Based on the requirements of subjective evaluation, it needs to develop performance model to the quality model, the key is to improve the fidelity of vehicle dynamics model. To establish an accurate vehicle dynamic model, it is necessary to establish the precise real-time engine dynamic model.Engine as the car's power source, the output torque through the transmission drives the vehicle. During the actual operation of the car, the driver according to the traffic environment, improvisation operation of the vehicle engine throttle, the clutch pedal, transmission pole, is making the actual engine operating conditions change in the moment. Therefore, the engine model in the vehicle dynamics simulation model, on the one hand requires precise torque output in real time, on the other hand needs to reflect the real situation of the operation of the driver of the vehicle. The driver accelerator pedal, clutch and transmission state linked to the driver to Driver to achieve simulate realistically in a variety of engine operating conditions that may arise under various working conditions. It requires the engine model can be simulated to achieve full working condition.Currently engine model which used in the China's first development-oriented automobile driving simulator is developed before 2003. Modeling methods: steady state model with a load, use engine universal characteristics of the modeling methods. There are experimental data Obtained through the bench test about different throttle opening and engine speed of the torque output characteristics, using least square surface fitting these data, establish throttle opening, speed and torque outputs relationship. For dynamic model with a load, as the engine was accelerating or decelerating, the mixed gas concentration change, causing the engine output torque is not equal to steady-state condition. Fluctuations in the torque and crank angular acceleration of change is proportional to approximately, using a linear load correction based on steady-state model establish a dynamic model with load. The model has two shortcomings need to be improved: 1. Modeling of vehicle dynamics simulation engine usually uses the modeling methods based on engine universal characteristics. In the actual tests mutations occur in some regions in diagram of engine universal characteristics. Fitting method will smooth out the torque, thus it can not display the characteristics of mutations. 2. Model does not considering engine anti-drag condition and start condition. For engine anti-drag and start condition and there are not characteristics of experimental models as a support. Thus it needs to make the appropriate experimental conditions to achieve the characteristics of the acquisition parameters. According to the above questions, this has made some improvements following:1.This paper analyzes the actual operation of the engine in the vehicle in a variety of working conditions, proposed the idea of modeling the whole working conditions. According to the different engine operating conditions and the status of transmission, The engine model is broken down into five interrelated conditions: steady-state with load conditions, dynamic with load conditions, no-load conditions, anti-drag conditions, starting conditions. Depending on different conditions, the establishment of a different engine rotation dynamics, and discuss with each other when switching between the model dynamic switching mode rotary engine.Engine steady-state model with load, non-steady-state model with load, no-load models are based on engine universal characteristics. Engine steady-state modeling with load used engine universal characteristic diagram obtained by interpolation method. Non-steady-state engine with load modeling is mainly on account of air flow and cylinder combustion throttle lag and other factors, using a dynamic correction on the basis of steady-state model. Engine in no-load conditions mean shift occurred in the transmission gap or in the case when the engine idling. At this point the engine state of motion of is rotating through the establishment of dynamic calculation. Engine anti-drag model is established based on the engine anti-drag experiment, when the input is engine speed and the output is the engine torque. The premise of establish the start engine model is to create a starter motor model. Taking into account the vehicle simulation engine accessories on the engine power consumption, also set the engine fan, air conditioning, starters and accessories such as vacuum booster pump model.2.The interpolation algorithms based on engine universal characteristics of this model are discussed and researched. Analyse the characteristics of the engine universal characteristics field. Describe the characteristics of the field and analyze surface fitting algorithm to the fit will smooth over all properties of field in some regions where should have mutations in the torque. Propose that interpolation algorithm should be used to interpolate the engine universal characteristics field. Then systematically discussed and compared the characteristics of several sub-interpolation algorithm, and extended to two-dimensional. Finally, several sub-interpolation algorithm ware used to interpolate the engine universal characteristics field, and interpolation results were compared qualitatively and quantitatively. Ultimately choose bi-cubic spline interpolation algorithm.3,Use C programming language to implement the model and the simulation program. Built models of the engine, then embed it in vehicle dynamics model for simulation, and compare vehicle dynamics software simulation results with Carsim simulation results. Final validation results showed that the engine model can be established to effectively carry out simulations at all conditions, the precision meets the needs of vehicle dynamics simulation.