| Automated Mechanical Transmission (AMT) is formed by adding electrical manipulation and control system to traditional Manual Transmission (MT). The power train (including engine, clutch, transmission) was controlled consonantly through Transmission Control Unit (TCU) by using electric control technology based on dry clutch and fixed-shaft MT. TCU, as the core of AMT system, realizes automatic shifting by controlling clutch and actuator in using of pneumatic, hydraulic and motor system. AMT not only has the advantages of Automatic Transmission (AT), but also inherits the merits of MT, such as high efficiency, compaction low cost. Especially for heavy commercial vehicle, AMT of heavy-duty vehicle is the most suited to the conditions of our national automotives industry.The design and optimization of shift actuator are key and difficult point during the development of AMT of heavy type vehicle. The characteristics of shift actuator directly affect the quality of starting and shifting process, and also the reliability of the whole system. This paper was mainly focused on the design of shifting actuator and the system characteristics of pure electric type AMT based on Jiefang CA6T123 MT equipped on Junwei truck.The main contents of the paper were as followed:1) The developing situation through out the whole world, the structure, the working principle and the key technologies of AMT were analyzed separately, the advantages and disadvantages of three kinds of shifting actuators with electronic controlled and dynamic type actuator as their representative were analyzed.2) Dynamics analysis were conducted on each phase of AMT shifting process. The working principle of synchronizer was analyzed in detail and its dynamics model was established. The shifting quality and three evaluating indicators were discussed, and their influence of shift actuator's property on the shifting quality was pointed out.3) Based on the MT of Jiefang Junwei CA6T123 truck, the pure electric shifting actuator was designed. After determining the structure of shifting actuator, the max resistance exerted on shifting actuator of each gear was calculated through the given shifting schedule, and the obtained result was treated as the basis for choosing motor type and determining the parameter optimization. Comparing stepper motor and direct current motor, the direct current motor was chosen as the power source of shifting actuator according to the design requirement of structure for AMT shifting actuator, for it has the advantages of high control precision and fast response. Lastly, the type of the motor and the parameter were decided.4) The shifting actuator was simulated by established models including dynamic motor model, motor model with load, and control system model. For motor model with load, the resistance model out of gear and shifting resistance model were discussed in detail, and the load curve was acquired. The three close loops control system was selected as control model for actuator control system based on the analysis of speed governing characteristics of motor.5) According to the system property of actuator, three close loops controller based on fuzzy self-adaptive PID was designed. In associate with the related structure parameter of the entire vehicle and its transmission, the shifting actuator was simulated by using the simulation model. The advantage of fuzzy adaptive PID control method was verified by comparing its simulation result with that of common PID control method. Two kinds of working conditions: two to one and two to three were chosen to be simulated. The simulation result showed that better dynamic characteristics of shifting actuator could be obtained in using of the control method and control strategy this paper proposed, and the shifting quality was improved at certain level.The contents of this paper have theoretical and practical value for further improving the characteristics of shifting actuator and shifting quality. |
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