Study on auto-control method and experiment for tractor depth based on fuzzy control

Abstract: There are many ways to control depth of tractor's electro-hydraulic lift hitch at home, however, force control or position control takes the main place and force-position combined control was studied less. The force-position combined control based on fuzzy control was brought forward in this article, and it can achieve the goal of depth's multi parameters control. Firstly, the structure of tractor's electro-hydraulic lift hitch and principle of the system are introduced. Then, the introduction of force-position combined control based on fuzzy control was proposed, the comprehensive coefficient was defined as the proportion of position control in force-position combined control. Actual value was calculated in advantage of depth value and resistance. The actual value was compared with the target value and then fuzzy control algorithm works. The essence of this control was that system transforms force-position combined control to depth fuzzy control in use of comprehensive coefficient. Besides, the depth fuzzy controller was designed. At last, the effect of resistance on depth in different comprehensive coefficient was studied through experiments. The results showed that the response of depth from 0 to 20 cm was less than 1.7 s. When comprehensive coefficients were 0.7, 0.5, 0.3, the depth's decrease showed as 3.2, 3.8 and 5.6 cm respectively. Meanwhile, the adjusting time showed as 0.79, 0.93 and 1.21 s respectively. It met the requirement of quick response of hydraulic lift hitch. When the comprehensive coefficient gets bigger, the effect of resistance to depth is less conversely. When the comprehensive coefficient is not zero, the system can keep depth and engine load stable at the same time. Driver can set the value of comprehensive coefficient to make electro-hydraulic lift hitch system adjust to many kinds of soils. Compared with the force control or position control, force-position combined control has more advantages. In the article, force-position combined control based on fuzzy control was presented and studied. The results reflect the dynamic characteristics of the electronically controlled hydraulic hitch system for ploughing depths control; and provide a theoretical basis for the controller design of the tractor's electro-hydraulic lift hitch system according to force-position combined control.