Electro-Mechanical Continuously Variable Transmission Control System And Control Strategies

The metal belt continuously variable transmission compared with other types of transmissions, can keep the engine running at optimal operation condition, for its ratio speed changes continuously and the power transffers uninterruptedly. The key technoledges to realize the superior performance of it are its control system and control strategies. The electro-mechanical controlled metal-belt pushed Continuously Variable Transmission (EMCVT) will largely improve the fuel economy, comparing with the traditional one which is controlled by the electro-hydraulic control system. But so far no any matured layout or design of this type of CVT has been seen at home or abroad. In this dissertation a type of electrical motor drive controlled CVT control system is accomplished and the mothed to analyse and establish the control strategies systematically is proposed. The main research work of the dissertation is as follows:(1) Though the mathematical model of the EMCVT, the variational characteristic of CVT is investigated, and then the control logic is put forward. Afterwards, the influence how different ratate velocity of the CVT's ratio control moter affects the vehicle's acceleration is researched. Based on this study, the theoretical evidence to choose the control moter is brought forward.(2) The system analysis method for control tasks is established. According to the method, the control tasks are divided into three hierarchies i.e. working condition recognition, control strategies and system executing. By this method the logical relation of the control system is simplified, and the theoretical foundation to realize the control strategies is established. Furthermore, owing to the complex operation conditions of CVT, the working condition recognition is subdivided into three parts i.e. recognitions for driver intent, vehicle circumstance and transmission status. Also the bases and rules used for fuzzy control of EMCVT are put forward. As the result, the working conditons recognition method is systemically and theoretically formed.(3) The dynamic model of engine-EMCVT powertrain is established and the simulation model based on Simulink is build up. Then the control strategies of the start clutch and CVT ratio change are preliminary validated by using the models. Through simulation the control parameters in fuzzy controller are initially adjusted. The simulation results prove that the control strategies can make the engine working in the economical speed at the most working conditions, and can deal with complex working conditions.(4) The control system software and hardware of electrical motor drive controlled CVT are integrated, with which a test-bed of engine-EMCVT powertrain is built up. On this test-bed some sensors are demarcated and their parameters revised. Also the basic functional tests of the control system are carried out on the test-bed. Through the tests, the control strategies are preliminary verified.The following conclusions can be achieved from above study:(1) Compared with traditional electro-hydraulic controll system, the EMCVT offers the possibility to further improve the economy of vehicles equipped with this type of transmission. It is indicated from the tests that the electric motor drive controlled CVT control system is a practical and feasible way, and the new type of CVT transmission will represent CVT developing direction in the future.(2) By using the hierarchical method proposed in this dissertation for working condition recognition and control strategy classification, the tasks that need to fulfil for control system can be resolved and integrated easily and completely. As a result, with this method the research foundation is established for EMCVT control system design and control strategy development.(3) By means of fuzzy control method, better control effects can be obtained and the benefit of EMCVT can be achieved even better.(4) It is proved from simulations and test-bed experiments that the EMCVT control system and control strategies developed in this dissertation can effectively accomplish the basic control function, and the control system worked out can satisfy the main. requirements for real vehicle tests.