Design and experiment on auto leveling control system of agricultural implements

To ensure agricultural implement level can improve the quality of work in agricultural machinery operation process. In order to maintain the level of agricultural implements in the field working, an agricultural implement auto leveling control system was developed. Real-time roll angle of tractor was obtained from tractor roll angle sensing system. The core algorithm of tractor roll angle sensing system was the Kalman filtering algorithm of tractor roll angle, which fused an accelerometer and gyroscope data to obtain the real-time roll angle of tractor. The leveling hydraulic cylinder elongation was measured using a straight-line displacement sensor. And the relative roll angle conversion function between agricultural implements and tractor was established. Then by controlling the electromagnetic directional valve, the agricultural implement was kept leveling. This article introduced the principle and structure of agricultural implement auto leveling control system, and the Kalman filtering algorithm of tractor roll angle and the relative roll angle conversion function were analyzed in detail. The tractor roll angle's Kalman fusion algorithm was tested in SGT320E three-axis turntable platform, and the experiment of agricultural implement auto leveling control system was carried out in the paddy field based on a matching 1PJ-3.0 laser leveler for paddy field. The leveler featured a specially designed leveling plow connected to an ISEKI PG6 transplanter by means of a hydraulically driven three-point linkage. The auto leveling controller used the Proportional-Derivative (PD) control algorithm to calculate pulse width, modulating for driving two ordinary hydraulic solenoid valves as actuators to regulate the plow's leveling. In order to evaluate the precision of tractor roll angle sensing system and auto leveling control system, 2 inertial reference systems (MTi-300) were installed in the transplanter and plow, respectively. Results showed that, the tractor roll angle sensing system could accurately measure the real-time tractor roll angle; the mean absolute error, the root mean square error and the maximum error were less than or equal to 0.15°, 0.18° and 0.33° respectively in SGT320E three-axis turntable platform; and during the working process in a paddy field, the mean absolute error, the root mean square error and the maximum error were less than or equal to 0.40°, 0.46° and 1.27°, respectively. The agricultural implement auto leveling control system could better realize the scraper's leveling control of laser leveler. The mean absolute error, the mean square error and the maximum error of the scraper's tilt angle were 0.52°, 0.24° and 1.15°, respectively, and in more than 80% of the time, the scraper's tilt angle of laser leveler was less than 0.5°, which was improved by 0.5° compared with the control precision of original leveling control system of laser-controlled land leveler for paddy field. The study provides a method for auto leveling controlling of agricultural implement, which can improve the work quality of agricultural machinery. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved.