Study On The Control Of Hill-starting For AMT

There are many merits in the AMT which is suitable to China's national conditions,and it becomes an important study and exploitation direction in automated transmission.In our country,there are many universities and manufactures who are studying the AMT system increasingly.Therefore,the farther method study of AMT system control and the appropriate summarization method of AMT design can provide excellent ideas and methods for the AMT development and father exploitation,and offer great utility value;it is important for the AMT industrialization and improving the self-determination exploitation capability of our country's automatic transmissions.Automatic mechanical transmission(AMT) is based on the structure of the traditional mechanical transmission,through the installation of computer-controlled automatic control agencies,makes the traditional transmission achieve the high efficiency,low cost automatic control.Regarding the hill-start,the mechanical transmission depends on the driver's skilled driving technology to coordinate the brake releasing,the clutch engagement and the engine refueling to achieve a smooth start.But the AMT system has cancelled the clutch pedal,the driver can not apperceive the clutch's position,so that the control of hill starting is to be more difficult.Thus,the control of hill starting becomes one of the key technologies for AMT's commercialization,and the clutch engagement control is difficulty,and difficulty in uphill start is its disadvantage compared to torque convert type automatic transmission.At present,regarding the AMT's hill starting problem,the solution is to install the hill-start assist system(HAS).So the study on the AMT vehicle starting ramp control with HAS has an important practical significance.The role of HAS is:With the adoption of ECU control,even if the driver does not step on the brake pedal also keep the vehicle power system under the parking state,and the vehicle will not back away.At the starting of an automatic discharge system power,the process of the vehicle starting is completed successfully.The basic principle of HAS working is:The electromagnetic check valves are equipped in the pipes between the main hydraulic cylinder and hydraulic brake wheel-cylinder,and the control unit controls the electromagnetic coil ON / OFF to open and close the circuit.When the electromagnetic coil is non-excited,the HAS valve is in open status and the brakes work normally.When the power of electromagnetic coil is in ON status,the HAS valves turn off to maintain the braking pressure of the hydraulic wheel-cylinder.If the driver feels that the braking pressure isn't full, he can step the brake pedal further and supply the wheel cylinder with oil to improve braking through the check valve.In the automobile starting process,when the clutch engages to a certain extent,the transferred torque is just able to overcome the initial resistance and the power of the solenoid valve is off,so the electromagnetic coil is at OFF status and open the hydraulic circuit to reduce the hydraulic pressure.The power of braking system is released rapidly in order to avoid flameout of the engine or down of the vehicle to achieve the starting smoothly of the vehicle at the hill.This article first recalls the development course of the AMT,and analyzes the key technologies needed to improve on the control of AMT starting ramp,and the research on AMT's structure and control principle is carried out,which has laid a theoretical foundation for the below research.According to the bonding process of the clutch I set up a dynamics model with the master clutch,slave disk at the core for ramp starting,and analyze the model in order to get the control law of clutch.I analyze the main factors which effect clutch engagement rules more detailed.And the clutch engagement speed control program is putted forward,while the paper uses clutch fuzzy control.The driver intentions,the main and follower disk rotational speed differential and joint length of clutch are considered as the input signal,so the clutch engagement process can be controlled more accurately.And then it puts forward the improving of the structure of power source for the clutch hydraulic cylinders.That is to say that it does not affect the steering system at work,when the conventional continuous supplying to the clutch by the electric pump is replaced with supplying intervally by a common oil source with the steering gear system.This method can improve energy conservation,and simplify the system structure,and reduce costs,too.And then the article analyzes the structure and working process of the HAS system,and design a slope sensor based on the kinetics and resistor strain theory which is simple structure and convenience of installation and measuring.It can measure the longitudinal gradient when the vehicle is running.The measured maximum is 30°,and the lower limit is 1°of this sensor. The sensor has small non-linear error and enough sensitivity.Thus it puts forward a program of an automatic control logic of HAS system,which is the HAS function automatic trigger based on the gradient-sensor identifying the gradient and the HAS valve released control based on the gradient-sensor identifying the initial resistance.Finally this article uses the MATLAB / Simulink software to set up a whole vehicle simulation model of a AMT vehicle with the HAS system starting-hill,which is based on the relevant data of the beach car with AMT in our research projects.Through simulation it demonstrates the feasibility and effectiveness of the clutch pressure control and the HAS system based on gradient-sensor that are discussed in the former paper;and also demonstrates that the program of use the fuzzy control method to control the clutch is reasonable.