Guidance and Steering Systems in Precision Agriculture
Types of Guidance and Steering Systems
There are three levels of automation for steering an agricultural vehicle: (1) navigation aids, (2) auto-guidance systems, and (3) autonomous vehicle steering systems (i.e., robots).
Navigation Aids
Relatively inexpensive navigation aids, known as parallel tracking devices or, more commonly, light bars, are being used by operators to visualize their position with respect to previous passes and to recognize the need to make steering adjustments if a measured geographic position deviates from the desired track. Tractor light bar guidance uses LED lights to guide the tractor along a predetermined path. The lights change color to indicate the position and direction of the tractor. The system also considers the size and shape of the tractor, as well as the terrain and environmental conditions, to ensure maximum precision. A manual guidance system provides a less expensive option, ideal for most applications, and minimizes the investment required.
Auto-Guidance Systems
More advanced auto-guidance options include similar capabilities with the additional option of automatically steering the vehicle using either an integrated electro-hydraulic control system or a mechanical steering device installed inside the cab. With current auto-guidance technology, the operator takes control of the steering during turns and other maneuvers, and the auto-guidance system steers the vehicle across the field. Future auto-guidance systems may automate the headland turns and implement controls (e.g., to lower or raise the implement). Additional guidance technologies that are near to commercialization comprise path or mission planning that produces the most effective coverage paths for multiple or single vehicles, sensor fusion that engages a multitude of corresponding positioning sensors to expand system reliability, and leader-follower structures for multiple vehicle navigation and control, as in the situation of combine harvester operation.
Overall Performance of the Auto-Guidance System
When adapting auto-guidance to a particular farm operation, it is necessary to understand that positioning error is one factor causing less-than-perfect field performance. In addition, the ability to maintain desirable geometric relationships between passes is affected by vehicle dynamics, the ability of the field implements to track behind the vehicle, and the actual conditions of the field surface. Therefore, poor quality of the steering control system, sloped terrain, or misalignments in the implement will cause the overall field performance to suffer.
Auto-Guidance System Components
Auto-steering systems generally incorporate a sophisticated mix of technologies that enhance precision farming. The framework of an automatic guidance system often comprises the following components: (1) a positioning sensor (GNSS RTK receiver), (2) an INS (inertial navigation system) for terrain compensation, (3) an ISOBUS, (4) a high-torque electric wheel for efficient steering, (5) an industrial display and intuitive software for productivity, and (6) an ECU (electronic control unit) module for direct steering control. The GNSS RTK technology is used to achieve high-accuracy positioning. GNSS system relies on signals from satellites to determine a precise location within centimeters.
Synchronizing Tablets and Smartphones with Auto-Guidance Systems
Auto-guidance systems can be synchronized with other devices such as tablets and smartphones, which can be used as display terminals. The systems can be portable, allowing farmers to move them between vehicles. The level of sophistication varies, making them accessible to farmers with various skill levels and to farms of various sizes and capital outlays.
Autonomous Vehicle Steering Systems
One of the most prominent trends in precision agriculture has been autonomous tractors and platforms where the operator’s presence on board is not required. In conjunction with other technologies, like automation, artificial intelligence, and IoT, self-driving tractors navigate through fields and challenging terrains autonomously, avoid obstacles, and keep crops intact by reducing the risk of accidents.
Positioning and Navigation Technology
Precise positioning and stable navigation are key in enabling the autonomous operation of agricultural machinery. They mainly involve position tracking, path planning, and motion control. Technologies such as the Global Navigation Satellite System (GNSS), Inertial Navigation Systems (INSs), laser navigation, visual navigation, and multi-sensor information fusion are commonly used to improve positioning and navigation accuracy.
Click on the following topics for more information on guidance and steering systems in precision agriculture.
