AMT SHIFTING SCHEDULES

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THE RESEARCHS OF
AMT SHIFTING SCHEDULES


Vehicular Automatic Transmission can be divided into three types: Automatic Transmission (AT), Automated Mechanical Transmission (AMT) and Continuously Variable Transmission (CVT). AMT has become a kind of transmission that is full of potentiality, due to its high transfer efficiency, low cost and easiness to manufacture.
The research on AMT shifting performance is key technology in the developing. Shifting performance directly influence the market competition and industrialization of AMT.
AMT has good market expectation, but during the shifting procedure, the power must be cut off which causes the poor shifting performance than AT and CVT. Only through improving the shifting performance can the commercial competence be established. So the virtual important thing is to find the way to improve shifting performance.
The development of AMT can be divided into three phases: semi-automatic, automatic and intelligent. The two major part of AMT are: the hardware including the mastered object, executor, sensors and TCU; and the software performing the control strategy.
The performance of AT shift influences greatly the performance of the vehicle. So the research on at shift quality is an important problem in the domain of AT researching. Shift quality control of AT is accomplished by electronic and hydraulic system. To shift smoothly, according the real time throttle valve opening and vehicle speed signal, the controller sends electronic signals to control oil pressure changing curve of the applying elements. this paper analyzes and research detailed shift quality control system，the analyzing model of shifting process and pressure changing curve of the applying elements
Firstly this paper summarizes the existing evaluated quota of shift quality, and fully analyzes and introduces the existing control manner of AT shift quality.
To meet the needs of research of vehicle starting and the real time control of shift, this paper puts forward a simplified model of engine-torque and a dynamics model of AT shifting process. Through the applying of the established model, this paper fully analyzes the process of the AT shifting.
This paper drafts the proper oil pressure changing curve of the applying elements which can improve the AT shift quality, and gives the material calculated methods of the AG4 AT. This paper simulates the AG4 AT’s shifting process of 2H to 3H.The results of the simulation validate the established simplified models and the expected oil pressure changing curve.
This paper fully analyzes the mechanism of the pressure regulating and flow controlling system of the AG4 AT, and preparatory discusses the design of the block-diagram of the shift quality control. This paper test the control system and hydraulic system of the AG4 AT by the AT hydraulic-electronic testing-bed. The result of the test validates the correction of these analyses.
Automated Mechanical Transmission, as so called AMT, is a new-style transmission system.  AMT technology applies the automatic technology to the manual mechanical transmission and makes the selection-gear, shift, clutch and throttle implement automatically. AMT technology is suitable for the situation of our country, and has an expansive market and development foreground. Shift schedules decide the time to shift and are the soul of the AMT. When the AMT is working, by comparing the states of the vehicle with the optimal shift schedules, the AMT decides the optimal shift time and achieves the shift automatically.  This will lessen the tiredness of the driver and improve the safety.  At the same time, the power and fuel-economy of the vehicle can also be improved.  The author chooses the shift schedule as the key technology problem to be researched and the main study aim of this thesis is to get the optimal shift schedules for the AMT and so improve the power and fuel-economy of the vehicle. Through analyzing the influence factors of power and fuel-economy for the automobile, the author get the establishment methods for the optimal-power shift schedule and optimal fuel-economy shift schedule. In order to solve the influence of mass on the shift schedule, the author presents a variable-structure-controlled shift system. This enriches the theory of shift schedules. Because the computer simulation can save a lot of manpower and material resources comparing with the true-car test, so in this thesis, the author uses the simulation toolbox MATLAB/Simulate to setup the simulation model for shift schedules. Using this model, the optimal-power shift schedule and optimal fuel-economy shift schedule above are simulated and proved to be reasonable.
Shifting performance is defined as the extent of swiftness and softness during the procedure of non-power shifting and to extend the life of the power train. The index is comfort of passenger, time duration and shock, nine factors maybe influence the shifting performance, and two experimental methods can be used to investigate the nature of this performance: one is collecting real-time data during road experiment and analyzing them, the other is the simulation of the operation conditions of the vehicle.
The core of the AMT system is the control strategy, the principle of the clutch engagement, shifting procedure, the choice of control method and the CAN communication between TCU and ECU can influence the shifting performance.
Shifting schedule is the schedule of auto shifting time between two shifts with controlling parameters. It includes economical and dynamical shifting schedule. At present, shifting schedule of two controlling parameters (vehicle speed and opening on throttle) is mainly used. If shifting schedule is not good, shifting will not happen at right time and the working condition of engine will be severe. It will make the sound of engine abnormally and stability badly through the whole shifting procession. Sometimes even flame out Schedule of clutch engagement is determined by releasing journey of clutch, opening of throttle, shifting, vehicle speed and loading. The main
Controlling goals are engaging quantity and engaging speed. The engaging control of clutch is mainly referred to the control of engaging speed. It is divided into three stages: fast, slow, fast.  Shifting quality is directly influenced by the second stage. If engaging harder, it will make shifting concussion, even flame out; if engaging more slowly, it will make the friction time longer and reduce its longevity.  The main controlling parameters are difference between initiative and passive and torques on both sides. When torques being approximately equal, it is proved by experiments that it  can guarantee shifting time and not make concussion through the procession of engagement at the time of difference of rotating speed below some value. Meanwhile, the abrasion of clutch is not severe.
Shifting procedure is the procedure through working harmoniously among engine, clutch and transmission. Their cooperation will affect shifting time heavily.  In order to decrease the shifting time,   the time that is spent on the friction of the clutch should be decreased first.  If we intend to increase the time of non-load stage, which helps to minimize the difference of the rotary speed between the driving disc and the driven disc. If we intend to shorten the time of the non-load stage, engage the clutch immediately after the gear change. The clutch can engage in a satisfying period if the new method of controlling the engaging speed of the clutch is realizable. And the time that is spent on synchronizing the gears should also be shortened. It can be realized in the following two ways.  The first is to decrease the difference of the driving gear and the driven gear.  The second is to increase the shifting force.  If realizing the union control between ECU and TCU by CAN bus, AMT has the best control and the best shifting performance by use of communication strategy between TCU and ECU.
Influence on shifting performance by hardware
The elements in hardware system are the basis of proper functions of AMT. Executors, sensors, electronic components, hydraulic systems have influences on shifting performance, the choice of hardware parameters is of vital important to improvement of shifting performance.
With the development of the theory and technology of vehicle, the technical increasingly mature of microprocessor and the extensive application of electronic technique on the car, people have no limit at satisfying the automotive means of transportation only, facing gradually from the request of the car power, economy and easily manipulating, flexibility, safety, an d the intelligent type of car becomes the focus in the vision of people increasingly. Company’s publicity slogan of" person, car, life"," make people the center" etc.  On the side exhibit the expectation of people to the automotive individuation, humanity.
In the development direction of the car intelligence, the intelligence of the automatic gearbox has important effect. But the intelligence of the automatic gearbox embodies at the establishment of the shift regulation. For the fashion, for satisfying people to the new automotive request, for competitive advantage of the car type, at present, each big factory in world worked very much in shift regulation of new car type.  Among those, the most arresting is AL4 automatic gearbox developed by PEUGEOT/CITROEN and RENAULT in that there unexpectedly are the 10 kinds of so many shift regulations. In the big system of person— car — road, the good and bad of the car control, reflect primarily in the coordination of the vehicle and environment (road), the coordination of the vehicle and person. And so,  the electronic automatic control system can save various regulations to provide the driver to choose to use, not only having the economic regulation, motive (call to sport the type again) regulation, but also still having the general (usual) regulation,  environment temperature and regulation with the outsider condition variety etc. Namely, the point of shifting can be freely enacted for every kind of regulation.  In the intelligence direction of the shift regulation, everyone has made much work up to now,  parts of the results has been applied on the car. But the work that developing this intelligent shift regulation still is hard, this is mainly because of:
1. The intelligence degree of the current intelligent gearbox needs to be increased, and it expresses at that accurate degree to identify environment is not high and to identify the driver’s driving can't give satisfaction.
2. The intelligence function is still not perfect. The intelligent automatically shift system is an open system; it must be continuously perfect and plentiful on the current foundation. Only this way, it can adapt to the driving request of the different drivers, reducing the driver’s labor strength, increasing the performance of the whole vehicle.
Conventional design method which used in the structure parameters' design of automobile gear box and synchronizer is a time-wasting job and hard work, and it is difficult to get idea design parameters and no good to the enhancement of products qualities. The optimum design of automobile gearbox and synchronizer which take the advantage of computers seeking the best structure parameters within constrains is a perfect and high-quality design method. The main target of this article is to set up a optimum mathematical model of structure parameters of the truck's gearbox and synchronizer, the auth or use a optimum method based on K-T equation to improve the design level of automobile gearbox and synchronizer. Gear box is a important part of transmission, so the optimization of automobile gearbox is very important because the transmission is a main part of automobile.  According to the design request and character sofa sort of truck, the optimum mathematical model of truck's gearbox is analyzed and set up in this article to decrease its weight and volume when the strength, stiffness, and lifetime of parts are permitted. And we can receive a satisfaction result through optimizing it's parameter for instance.
Synchronizer is a important part of automobile gearbox, it make drive gear and driven gear engaged after their synchronized, so it can decrease engaged shock and noise, it can decrease shift forcing and make it comfort to gear shift and increase the life of synchronizer.  The synchronized process of synchronizer is analyzed in this article; we can receive a satisfaction result through optimizing its influence parameter for instance when the synchronized time is the shortest. The optimum toolbox of MATLAB is a convenient of ware of modern optimization with fast speed and powerful function. The algorithms of different mathematical subsets are divided into different librarians in the form of functions in MATLAB optimum toolbox. When we use them, we just call the functions and give special parameters to solve the problems and this will be fast and accurate. The author gives an optimum design for automobile gearbox and synchronizer by using the optimum toolbox of MATLAB and receives a satisfaction result.

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