Research On The Strategy Of Ratio Control Of Metal Belt CVT

Dissertation Title: Research on the Strategy of Ratio Control of Metal Belt CVT Major: Vehicle Engineering Mentor: Professor Zhang Youkun Abstract:The Metal Belt CVT is a type of ideal transmission for passenger cars.Compare with the widely used Automatic Transmission (AT) currently, it has many advantages, such as the function is good, the structure is simple and the price is low, etc. Along with the technological advance, The Metal Belt CVT is acquiring bigger and bigger development with its excellent no class characteristic. The ratio of the Metal Belt CVT can change continuously within the scope of design, enable the engine work in the best appearance, prolong its service life, improve the fuel economy and dynamic performance, reduce exhaust, and carry out integrated control of the engine and CVT.Among CVT's control system, speed ratio control is one of the key technologies. Through control the stability of speed ratio, can make the vehicle according to driver's intention automately realize dynamic optimum matching between vehicle's running resistance and engine's output power. In this way, it can exert vehicle's fuel economy and dynamic performance to limiting condition, meeting its requirement on fuel economy and dynamic performance. The speed ratio control strategy of CVT affects the quality of transmission, the fuel economy, the dynamic performance and the emission. So this paper makes some research on the strategy of speed ratio control of CVT.1. This paper introduces CVT's development condition, internal actuality and development trend. Indicate that in order to guarantee favorable entire car performance, speed ratio control is the key. Finally, confirms this paper's research sense and research content. The no class transmission is an old concept, it has been a target for the people from the automobile appeared. Today, two major types of no class transmissions are actually used, they are Lead to spread the move type and take to spread the move type. Lead to spread the move type is not widely used because its reliability and durability are not resolved. Take to spread the move type can be divided into metal belt type and metal chain type, the former is better than the latter in general characteristic, so it acquires more and more development and use.2. Analyses CVT's basic structure and gearshift theory. Then studies the principle of speed ratio control. Emphasized the rationale and the control technique of transmission, which supplied the rationale for the research of the CVT's behavioral in this paper. To study on the integrated control strategy of the engine and CVT, firstly, the data model of the engine was built up according to the steady experiment data; secondly, the model of the power and the transmission system was built up, and the effect of ratio change rate on the vehicle dynamic performance are analyzed. Controlling CVT's ratio according to the engine division door open degree and current car speed, enable the engine work in the best appearance, thus is the matching principle of the engine and CVT. Confirming the division door's open degree of the engine and the ratio of CVT to change under a certain principle according to the driver's request and the running state of the car, consequently enable the car in best performance.3. Analyses the strategy and the method to realize the speed ratio control. CVT's target ratio is confirmed according to the engine division door's open degree and current car speed, the ratio control must enable the real ratio achieve the target ratio as soon as possibly, and undulate near the target ratio. Concretely analyses thstrategy of speed ratio control according vehicle starting-acceleration and release work condition. Analyses the different arithmetic of the speed ratio control of CVT. Concretely analyses the arithmetic of location PID and increment PID and integral separate PID.4. In order to study the control effect of speed ratio control theory to CVT vehicle, establishes engine simulation model, cvt-power train simulation model and ratio control with PID method model, and combines them together to get the Matlab Simulink model of CVT entire car with PID control method. Then according to the established simulation model adopts different PID control parameter towards CVT entire car at starting-acceleration and release working condition and proceeding contrast simulation analyses, check speed ratio PID controller 's control effect and control law as well as affect on stability of speed ratio of control parameters.5. Test is an important part in the research of the science. Test is to proof if the analysis of the theory is right. In the pedestal test of CVT, I preceded the following test on the constant speed ratio for 0.7, 1.3, 2.2 and the step tracking test of speed ratio for 0.6-1.6 and 1.6-0.6 to demonstrate the rationality of PID controller which was designed in the paper. Because of the confine of the test condition, I haven't done the test of an entire car, and haven't demonstrated the power capability simulation analyses on the entire car.