Research On The Structure And Constant Speed Control System Of A Self-propelled Mini Transporter

The roads in the hilly areas in China are narrow and with steep slope, so the existing agricultural transport machinery is unable to work in the field roads and the security level is low. Planting in the hilly areas requires a lot of labor work for the transportation between the fields and main roads, which will increase the cost of agricultural production. At present, the main problems of the motorized transport machinery used in the field roads on hilly areas are with poor security, poor handling, and low transportation efficiency. With the development of intensified and professional agriculture, the security level of field road transportation machinery used in hilly areas should be urgently improved. To solve this problem, this paper, based on security, adaptability and economy, develops a small self-propelled truck with constant speed. For this purpose, the following work are carried out:① According to the survey of the road conditions and the machinery usage conditions in the planting area of the hilly region, the basic structure of the small field road truck was determined. Surrounding the controllability, power performance, flexibility, efficiency and other design goals, the structures like braking system, steering system, and body itself were designed in detail. Based on the structural parameters of the above subsystems, the three-dimensional model of the truck was built with the modeling software and the interference checking of the moving parts was also conducted. On this basis, a prototype field road truck was made and was tested on the field roads. The results showed that the designed self-propelled field road truck is easy and convenient in operation, such as the completion of turning and other various actions can better adapt to the working environment in hilly areas, thus the transport efficiency has been greatly improved.② The study on the controlling software and hardware systems of constant speed was carried out. After elaborating the principle of direct torque control of brushless DC motors and establishing the mathematical model, the NI-Multisim software was used to design the controller hardware circuit, including the D/A conversion circuit, the speed detection circuit, the energy consumption deceleration circuit and so on. Simulation analysis of circuit then was made, using the simulation module of NI-Multisim, to test the circuit rationality and optimize it. Based on vehicle operation control strategy, the control flow was designed and then the MPLAB software programed according to the flow, debugged and programed it online. The results showed that the design of the constant speed control program could run smoothly.③ Detailed analysis of the vehicle constant speed control strategy and simulation analysis were made, and then the fuzzy PI control algorithm was selected as the basic strategy of constant speed control, and selected PID control algorithm with fuzzy PI control algorithm to compare the constant speed control strategies. Fuzzy PI control rule and its membership then were defined. Using Simulink software, vehicle-driving system was simulated. By addition and subtraction the load to simulate the downhill and uphill working conditions, raise and reduce sharply the resistance on the vehicle thus to illustrate the influences on the constant speed control of the vehicle exerted by different control algorithms and to find the better one. The results showed that the fuzzy PI control, compared to the normal PID control, has a closer response rate, but its overshoot rate is smaller and the fluctuations caused by it is also smaller. Through the Simulink simulation, the parameter variables can obtain the specific output value by fuzzy PI control.④ After making the vehicle control, conducting the test of the constant speed controllability of the real vehicle, and fine-tuning the parameter variables online, then the paper adopted he NIUSB6361 acquisition card to collect the speed pulse and analyzed it. Test results showed that the small truck can have a stable constant speed driving, and the rate of change does not exceed 10% at 15° uphill and downhill roads, speed stabilization is less than 0.5s. Real vehicle tests showed that the small truck has an easy manipulation, and the operator can control easily at the sharp bends, steep slopes and under other complex traffic circumstances.