DESIGN OF AUTOMATIC NAVIGATION CONTROL SYSTEM FOR AGRICULTURAL VEHICLE

Abstract

The tractor automatic navigation technology is one of the hottest research fields of precision agriculture as well as a major means for realizing intelligent operating of agricultural vehicle in future. This paper presents a thorough research on GPS automatic navigation technology of agricultural vehicle considering that working conditions and field conditions for the tractor are complex and that there is a high requirement on the precision of the driving path of the tractor. Major contents of the research are as follows: The hydraulic control valve was selected by testing. A hydraulic control valve test platform specific to navigation was designed. The test platform can gather information about the flow and pressure of each measured hydraulic valve in a real-time manner. A navigation valve block was developed. Finally, the navigation valve block was used in electro-hydraulic transformation of model vehicle, realizing the control of electrical signal in tractor steering. A hardware platform for the automatic navigation system was built. A navigation controller based on ARM chip, the RTK-GPS positioning system and the angle sensor constitute the hardware platform of the autopilot system of the tractor. The hardware platform is the basis for realizing automatic navigation of the tractor. The navigation control algorithm was studied, pure pursuit model tracking algorithm were analyzed; the navigation decision-making control system based on the pure pursuit model tracking algorithm was designed; the kinematics model of the tractor was established. The pure tracking model has been simulated by MATLAB software, and the system has good stability and sensitivity. The experimental research on the automatic navigation system of the tractor was conducted. Based on the automatic navigation platform developed above, experiments on the control of the tractor walking straight at the flat road have been done. The results proved that the automatic navigation system has the capability of tracking the straight path of the tractor in a real-time and stable manner and meets the requirements of precision agriculture.