| The automatic navigation technology of agricultural machinery is of importance in the modern precision agriculture. Furthermore, it has become not only a key technology but also a research hotspot in the agricultural automation equipment field. Thus, the research on automatic navigation control method and its relevant equipment development were investigated in this paper. Three typical agricultural machineries of tractor, rice transplanter, pipe-laying trencher were employed as research subjects respectively. Technologies including GNSS, mechatronics and computer distribution control were integrated in this research. The sensor monitor network based on CAN bus was constructed for agricultural machinery. The multimode variable structure intelligent control technique and method were investigated. The main contents of this paper are as follows:(1) The foundation of automatic navigation technology for agricultural machinery was discussed. Firstly, the state variables and kinematics model were derived in order to better describe the movement characteristics of agricultural machinery. The basic navigation control rules were established based on the kinematics model of agricultural machinery, and then laid the theoretical foundation of the application of intelligent control technology for the typical agricultural platforms. Secondly, the principle and method of satellite navigation and positioning system were developed. A GNSS positioning module, which was compatible with BD/GPS/GLONASS, was independently developed and tested. The experimental results showed that the horizontal positioning accuracy of the GNSS positioning module is better than 1 cm (RMS) under the RTK positioning mode. Thirdly, the information communication frame of the CAN bus was analyzed in detail on the basis of communication standard and network structure of the international agricultural machinery CAN bus.(2) The navigation control method was studied. The agricultural field work is a complex process. Focusing on the multimode characteristics of agricultural automatic navigation, the multimode variable structure control theory was introduced. The navigation control method, which integrated a variety of intelligent control technologies and methods and took full use of the respective characteristics, was studied. On the one hand, considering time variant property and uncertainty of the process of agricultural machinery navigation, the multimode variable structure intelligent control strategy was proposed and the theoretically researched. On the other hand, the fuzzy control theory and method, self adjustment fuzzy control technology, system identification and adaptive control technology were systematically studied, experimentally simulated, and typically applied on the navigation of agricultural machinery.(3) The model reference adaptive navigation control method was studied. According to the characteristics of the wheeled tractor navigation, a fuzzy adaptive navigation control system was designed. The Kalman state reconstruction algorithm was used in the heading signal processing. The automatic navigation control system was developed for the tractor. The manual / automatic electrohydraulic control was transformed for the tractor steering system. The steering system controller and the front wheel angle sensor system were developed. The navigation path tracking and control software system was developed and tested not only off field but also in field. The tracor automatic navigation control system is stable and accuracy with the straight line operation deviation of less than 5 cm, which can meet the need of precision agricultural operations.(4) To solve the slipping problem of rice transplanter in paddy field operation, the operating slip identification, self-tuning navigation control method, and the relevant simulation experiment were studied. The automatic navigation control technology was carried out for rice transplanter in the paper. The steering transmission system of the rice transplanter was modified from manual control system to electronic control system using servo motor. The steering system controller and the steering wheel angle detection system were designed. The automatic navigation control system based on CAN bus was developed and tested on both pavement and paddy field. The experiment results indicated that the lateral tracking error could be kept within 10 cm under the travel speed not greater than 0.6 m/s. The control system could satisfy the requirment of rice transplanting.(5) The multimode self-adjusting fuzzy control method was studied, and the self-adjusting navigation control rules were further designed. The automatic navigation control system was developed to technically support to operation quality of pipe-laying trencher. The manual / automatic switching was designed in the contol circuit, and then its application on the crawler walking system was modified to electronic control. The vehicle-transportable controller and navigation software system were developed and tested in field. The experiment indicated that under a travle speed of not greater than 0.5 m/s, the lateral tracking error of less than 10 cm could completely satisfy the accuracy requirement of auto-follow row for pipe-laying trencher. |
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