Study On The Control Strategy Of Metal Belt Type CVT

Continuously variable transmission ( CVT ) a new and advanced kind vehicle transmission. So that, the integrated Control of engine and transmission comes true. In all the running conditions of the vehicle , in order to meet its economic and power requirements, the ratio should be able to ensure the engine output enough power ,according to the driver's intent to match the best dynamic automatically, The economy of the vehicle, power-play to the limit, which called for the CVT transmission ratio control.People must look it as one assemble with the engine, and use the controller to combine the two parts.This paper studies the following areas:This paper introduces CVT's development condition, internal actuality and finally, confirms this paper's research sense and research content. 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.It is basic to establish the model of ratio of the continuously variable transmission control systems, they are the model of the main, driven pulley axial clamping force, the transmission power model of control system, the mathematical model of engine torque outputting.It is not difficult to control the CVT ratio simply, but it is difficult in accordance with the requirements of CVT on the car, and the driver's intention, in different working conditions, appropriate changes in the rate of speed ratio control to achieve the best performance. since the clamping force controlling and speed ratio controlling is coupled with each other, that is, changes in the clamping force is bound to cause changes in the ratio [5], so you want to maintain the speed ratio unchanged If changes in the delivery of torque, while the main round of the follower of the clamping force should be changed at the same time; In addition, if the follower round of the clamping force remains unchanged, a separate initiative to change the wheel clamping force can change the speed ratio. And the ratio in the event of a changing, change will be driven round the countries of origin of the fuel tank pressure balance. As a result, the proper ratio to control the rate of change, so that the car's performance to reach the optimal, it has become the focus of the CVT ratio control and difficulty.To determine the CVT controlling strategy .you must think about the coupling relations of the clamping force and speed ratio and carry out the analysis of speed ratio control strategy as the accelerating , driving stability, deceleration, the cycle.PID controller can be a simple analog circuit, without the use of accurate model systems, such as a prerequisite, has become the most widely used of the controller. PID controller was among the first developed one of the control strategy. Because it is controlled with a simple control structure, in practical applications and easier-tuning it in practice a wide range of applications. At present, most of the world's CVT products are used PID controller. According to the CVT in the form of control to study of PID control method and designing PID controller.When the CVT transmission transfer the torque, with metal force distribution and metal belt pulley on the axial force on the determination of a certain ratio. In the general analysis of the process, the pulley is large enough to provide the clamping force for the preconditions, that is, assuming Pulley with the metal band clamping force of the pulley axial force balance as a precondition. In practical applications, according to the size of the input torque, the main control, the clamping force from the pulley to transmit input torque and speed ratio adjustment, it is necessary to determine the pulley clamping force. Because of the axial force and torque delivery which was related to the transmission ratio, it should analysis the pulley clamping force.To determine the driven wheel clamping force control strategy, you must analysis the influence of the axial force of the pulley to the torque transfer , design the clamping force controller and study of the clamping force controlling in combinating of speed changes, changes in the load, speed ratio changes in working conditions one the test platform. In this paper, it is the target to control rate parameters of clamping force. In the analysis of the slip rate changes on the basis of the analysis were changes in speed, load changes, changes in conditions step ratio of clamping force changes in the law.The controlling is the core issues throughout the CVT technology development. As the incomparable advantages of electronically controlled, the use of electro-hydraulic control is popular. CVT's electronic control system research and development, improve China's domestic car of the self-development capacity and shorten the gap with the developed countries have important practical significance. With the energy and environmental issues have become increasingly prominent through the engine of the vehicle and technical performance continued to improve in order to meet consumers and the requirements of national policies and regulations will determine automakers market share. It is the meeting point of the interests of all parties.