Research On Electrically Controlled System And Control Strategy Of CVT

The dissertation mainly focuses on the control system of the metal pushing V-Belt type CVT system.The main research content is as follows:In the beginning the dissertation reviews the development process and the technique of CVT briefly. Through the comparison with other transmission, it shows that the metal pushing V-Belt type CVT can meet the current demand of drivability, economics and emission etc.Because of its special structure, the transmission mechanism of metal pushing V-Belt type CVT is much different from that of the traditional rubber V-Belt. The transmission mechanism of CVT is the foundation of its control system, So the kinematics of the belt, the load distribution and variation of the element compressive force and ring tensile force, and the relationship of the transmitted torque, ratio and clamping force, are discussed thoroughly on the basis of the hypothesized model. And this is the theoretical basis of CVT controlIn CVT, the variable-speed gear function is realized by the hydraulic system which controlled by the Electrically Controlled Unit(ECU). So it is the essential condition for the ECU design and the control software develop to analyse carefully the hydraulic system in the later period. In the paper the hydraulic system principle and the work process has been further analyzed, and the hydraulic system valve body structure, the oil duct as well as each kind of valve of the sample have been analysed under each active status; Meanwhile the proportion solenoid valves which realize the clamping force and the speed ratio control, the high-speed switch solenoid valve which realizes the clutch control are established mathematical model, and are simulated. This has provided the theory basis for the metal pushing V-belt type CVT to design the electrically controlled system hardware and software.The electrically controlled system is one of CVT system core technologies, its software and hardware designs affect directly the CVT operational performance. Through analysing the characteristic of these sensors.in CVT system, has designed the electronically controlled hardware unit and the software control system based on the hardware electric circuit, moreover it has been proven that software and hardware of this electrically controlled unit system are stable after the use.In order to cause the engine to work at the best active status, it's necessary to match the CVT system and the engine. In this paper the best power performance and the best fuel oil efficiency have been matched to this sample CVT, these data obtained about the best power and the best fuel oil efficient are the foundation of the speed ratio and the clamping force control .The powertrain system with the CVT is complexly multi-input's, nonlinear system, and also has the coupling effect between its input and output, therefore it is very complex to design strategy. The CVT control mainly includes the clamping force control and the speed ratio control, in which the clamping force control is the hydraulic system pressure control, which had the very many successful application experience in this aspect PID controller, therefore the traditional PID controller has been used in the clamping force control, and it's very satisfied with the dynamic response. But the speed ratio control is more complex and difficult by reason of its uncertainty, and it is difficult for the traditional control method to solve this problem. The neural network system is the very good to solve uncertainty mathematical model question, in which it is possible for the CMAC (Cerebellar Model Articulation Controller) to solve the non-linear mapping relations, moreover its study speed was also very quick. The designed controller based on the CMAC PID control to the speed ratio has the very good dynamic response ability through the CMAC short time study, and it is satisfied to the speed ratio control request of the CVT system.Finally, the experimentation on the road and the power measurement machine about typical operating performance mode has been carried out through the replace of the original electrically controlled unit, and the test result indicates that the electrically controlled system and the control strategy is satisfied, and is quite close with the original sample vehicle control effect, and the system is applicable in practical system.