1.1 Purpose and significance

Thelongitudinal performances and fuel efficiency are important indicators of a vehicle’sperformance. The longitudinal performances are composed of: maximum speed,acceleration time and maximum gradeability, fuel efficiency indicatorsincluding constant speed fuel consumption per 100 km and cycle fuelconsumption. The longitudinal performances are the basic usability of vehicles,they are the most basic type of performance indicators, as well as the mostvalued performances indicators of the customer. Automobile belongs totransportation tools of high efficiency, and its efficiency depends on itslongitudinal performance at a certain extent. Automotive industry is becomingone of the pillar industry of China as it has developed fast in recent years.Further research aiming at longitudinal performance is the basic of designingsafe vehicles, therefore these researches are necessary towards the developmentof automotive industry. The fuel efficiency is an important indicator ofvehicle’s performance just as the longitudinal performances. The financialbenefits of the customer can be directly affected by the fuel efficiency. Asthe pressure due to environmental and energy crisis keeps rising, purchasing amore fuel-efficient car is becoming a trend. With the constant growth offuel-efficient cars on the market, analyzing factors that affect fuelefficiency, finding approaches of lowering the fuel consumption to increasefuel efficiency is becoming more and more important.

The cycle ofacquiring data through actual tests, then modify parameters based on the testresults can be commonly seen during the process of modern vehicle design toachieve expected design goals, or to optimize performance. Data can be acquiredby having field tests or simulations. Field tests can be of low efficiency andhigh cost, since the test model go through series of modification and rebuildbefore the design is complete and the test result can be influenced by unstablefactors due to environment or test driver. Comparing to field tests, simulationbased on cyber world, which enable engineers acquiring test data withoutbuilding a prototype car. Simulations reduced the cost of developing a completeproduct, improved developing efficiency, as well as providing an ideal testenvironment without any unstable factors.

The longitudinal performance andthe fuel efficiency are strongly connected and cannot be optimized at the sametime under most circumstances. Therefore, studying these performance indicatorsas a trade-off problem in a single platform can of significant meaning todesigning products that aim at certain target groups. This project aims atdeveloping a simulation platform that can carry out longitudinal performanceand fuel efficiency simulations, as well as giving optimize advice based onparameter sensitivity.

1.2 Research status

1.2.1 Domestic research status

Domesticsimulation research mostly based on MATLAB language. MATLAB provides a flexibledesigning process with huge amount of built-in functions and powerfulsimulation tool as well as convenient co-simulation port with other software,which significantly simplify the modeling process. Many facilities andresearchers had studied the longitudinal performance and fuel efficiency ofcars with various methodology, such as simulation directly using mathematicalmodels or using regression models instead. Some of them chooseforward-simulation for accuracy, while others choose backward-simulation forefficiency.

For example,Xu Zhongming and his fellows created the engine’s external characteristic anduniversal characteristic models, which based on actual engine dyno data, withleast square method and rules of linear regression. The relationship betweenfuel consumption rate, engine rpm and torque is simulated. With the completemathematical model, parameter sensitivity is calculated. Optimization advicewas given based on a simulation programed with MATLAB.