犁耕作业大马力拖拉机驱动轮滑转率控制方法.

In north China, the ploughing operation of high-power tractor based on electro-hydraulic suspension system is the most common and important agricultural process in the field agricultural production. Due to the complex field working environment, the change of tillage depth and the fluctuation of soil specific resistance, the working load of tractor unit fluctuates greatly during ploughing operation, which is easy to cause excessive sliding of driving wheel， and seriously affects the traction efficiency and traction of the operation unit. In order to solve the problem of excessive driving wheel slip of high-power tractor for ploughing, taking the high-power tractor ploughing unit with electro-hydraulic hitch system as the research object, a sliding rate control method based on sliding mode variable structure control was proposed this paper. Firstly, in view of the strong nonlinear characteristics of the complex system of "tractor-farm tools-soil", the nonlinear dynamics model of tractor driving wheel sliding for ploughing was established based on tractor motion characteristics and the theories of vehicle dynamics. Then, the exponential reaching law was used to design the sliding rate nonlinear control algorithm based on sliding mode variable structure control theory. Especially, taking the hydraulic pressure of hydraulic cylinder as the equivalent control quantity, the control law of sliding mode variable structure control was derived after simplifying the hydraulic system. Through MATLAB/Simulink simulation, the reliability of the nonlinear dynamic model and control algorithm in the step change of soil specific resistance was verified. According to the soil data obtained from a specific site, the soil specific resistance was set as pulse signal, and the stable value was 30 000 N/m². At the beginning of the simulation, a soil specific resistance with an amplitude of 8 000 N/m², a period of 10 s and a duty cycle of 50% was added to block the impulse signal. The results showed that the slip rate of the driving wheel was always near the sliding surface, the steady-state error was 0.002, and the control overshoot was 0.008. Furthermore, the field test platform for automatic slip rate control system was built on Lovol-TG1254 tractor, and the field comparison tests between SMVSC control and Fuzzy PID control were carried out under the tractor speed of 2.17 m/s. The test results showed that compared with the fuzzy PID control, the mean absolute deviation of slip rate under the SMVSC control decreased by 27%, the maximum deviation decreased by about 49%, and the fluctuation range and control deviation of slip rate were smaller. The change of depth was 5.26 cm, which decreased by about 27% compared with that of the fuzzy PID control, the change of hydraulic cylinder displacement was 1.15 cm, which decreased by about 36%, and the adjustment change of traction was 1 293.35 N, which decreased by about 42%. The control deviation of the driving wheel sliding control method proposed in this paper was small, it can provide theoretical basis and technical support for improving the quality of ploughing operation. [ABSTRACT FROM AUTHOR]