Research On Modeling And Simulation Technology Of Automatic Transmission

Electronic Control Units(ECUs) are widely used in the vehicle to improve vehicle performance, more than 90% of the vehicle technical innovation is related with vehicle elctronic technique in some degree according to the statistic results now, So it is one of the main direction of vehicle R&D technology. The modeling and simulation method is a very common technology during the Electronic Control Units development and test process in international vehicle research and development agencies and manufactures. Although the simulation results of model is only very closer to the reality, but the model provides a very convenient development platform for the design of ECUs and it make a great efficiency development process. It is obviously that the modeling and simulation method has become one of core technologies during the development process of ECUs. In our country, The ECU'products are still in the development stage, we haven't had the ECU products developed by ourself especially for the vehicle main assemblies yet. So it is more meaningful for us to develope our ECU products with the modeling and simulation technology.The type V process of the ECUs development is very common used on the world and there are three development stages during which the modeling and simulation technology have been used.The first stage is function building process of control software, the control strategy model is built on the personal computer and it is intergrated in the vehicle offline model on the same computer. Then the whole model should be run correctly after some debugging and adjustment. The analysis and verification activity of the ECU function can be realized with the model. The second stage is applied for the test and verification of control software code.The control strategy model should be edited as C code and downloaded to the commercial hardware part which is called rapid control prototyping system, then the control strategy can be tested and verficated in the real time vehicle model environment and even on the real vehicle. The last stage is used for test and verification and initial calibrartion of real ECU, The real ECU is integrated into realtime virtual vehicle simulation platform established based on model and partially real loads to execute the closed–loop automatic test and the initial calibration function of control strategy. All of these three stages form the main parts of the Type V process, we can see the modeling and simulation method is an important and key part of the process.The development and application of automatic transmission on the vehicle is still one of hot issues in our country now. it is belong to the mechnical and electrical intergration technology for the vehicle main assemblies. But we haven't automatic transmission product developed and produced by ourself. Some manufacturers are still in the producibility R&D stage of automatic transmission vehicles. The type V process discussed above is a effective plan for us to develop automatic transmission, It can accelerate the development speed and improve the design,test and verification ability of our product. First we should have the modeling and simulation technology on the automatic transmission to realize the plan. The technology includes unreal time model for offline simulation and real time model for hardware in loop(HIL) simulation system. And HIL system has become an effective technique to develop and test the ECUs, so modeling and simulation technology become an important part for the development of Electronic Control Units. The development of Transmission Control Unit (TCU) and the application of HIL system have been researched with modeling and simulation technology for automatic transmission, and some of problems for products have been solved in this paper, it is meaningful work for our automatic transmission product. The main contents of the article are as following:1. The ECU development and application process has been researched. The modeling and simulation technology which is used in the process has been analysised. Then the main and key abroad product technology of automated mechanical transmission (AMT) has been investigated and HIL system have been developed by ourself. The concrete application of modeling and simulation technology has been affirmed in the process. Then the technology direction has been clearly defined.2. Mechanics theories and product of friction model have been analysed, the clutch friction test has been done which is corporated with a foreign R&D company in order to establish a more accurency dynamic model. The influence on the transfer torque of the clutch temperature and slip speed is analysised based on the test results, and the clutch friction model considered the temperature factor has been developed based on the LuGre model.Clutch temperature prediction model has been developed and as a new function the model has been applied to automatic transmission ECU and HIL system. First according to the transmission control unit (TCU)'s requirement of the precise control of the clutch Torque and overheating protection function, the impact of the clutch temperature on the transfer torque and the failure mode of the clutch friction plate are analyzed in Practical applications. Then the clutch temperature model theory has been established and the clutch temperature model been builted with Matlab/Simulink software. Then the clutch temperature had been measured on the test bench, the model parameter calibration and model validation have been done according to the test results The reasonablility of the model has been affirmed according to the test result. At last the model accurancy has been improved and adjusted according to the practical application environment and traffic conditions, the calibration and analysis test of the model on the real vehicle had been realized by rapid control prototyping system.3. The simulation model of automated mechanical transmission has been built. The synchronize process of gearbox has been analysed based on the test results and the synchronizer model has been build at same time, the model has accurently simulated gear shift process, So one of the most difficult part of the gearbox simulation——synchronizer simulation has been resolved.4. The TCU model has been built. According the requirement of offline and online simulation, a basic TCU model has been built. As one of TCU important function——automotive shift schedule technology included structure building process and computation technology have been researched and developed in order to realize the vehicle simulation and automatic test of TCU. First the data conduction program of engine universal characteristic curve has been compiled as the basis of building shift table. Then the factors which have some influence on the shift schedule such as driver behaviors, the traffic environment and the vehicles performance have been anylasised. The shift schedule structure has been built according to all of these factors. The method of defining the priority of different shift tables has been developed. At last the shift schedule calculation programs had been compiled according to demand of real vehicle project, The program include calculation method of the dynamic up and down shifting table and the graphic computation method of economy shift table.5. The integration application of automatic transmission model to the whole simulation system for offline and online usage has been researched. The real time simulation demands the model should be computed with fixed step solver, the stability analysis technology and the stability real time algorithm have been developed according to the requirement.First the vehicle longitudinal dynamic vehicle model for offline intrgration usage has been developed according to powertrain one-dimension model theory. In the model the clutch, gearbox, longitudinal dynamics of vehicle and TCU has been built and intergrated and the simulation result is reasonable; in order to realize automatic function for driver and road model, Automatic transmission model has been also integrated with commercial simulation software in order to get benefit from its simulation environment, such as the commercial software can provide the driver model, road model etc and all of those model is difficult to build, the intergration can expanse the usage of our model and make the commercial software more suitable to application on the vehicle developed by ourself. The online application of automatic transmission model has been realize by integration it to the HIL system.Then the analysis method for simulation stability of discrete model has been detaily researched based on linear system analysis theory, the analysis rule for the simulation stability of discrete model has been provided in the method and it can act as the basic theory of simplify the model. The application method of the rule had been explaniation with vehicle driveline model.At last,the implicit Euler solver of online model has been researched and the algorithm can guarantee online model's accurancy in some degree. The method has been used in the model building process and it is effective according to the model analysis results. The solver not only can application to the development of real time model but also its application provide an effective method for more high order solver.6. Then first whole vehicle HIL system has been built in our country, as one of the project members, the test technology and test plan of atomatic transmission have been researched and developed. The principle and building process of HIL system has been explained intergrated with the HIL project. The HIL system simulation results have been compared with the real test ones,The accurancy of HIL system is enough for the ECUS test. The test process of HIL system has been researched and the main technology of test has been analysed. The test case and test program have been and developed based on the automatic transmission vehicle. The automatic test and the initial calibration technology for automatic transmission have been developed on the HIL system.