Lateral Displacement Control for Agricultural Tractor Based on Cascade Control Structure
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ISSN:1598-6446 eISSN:2005-4092 http://www.springer.com/12555
Lateral Displacement Control for Agricultural Tractor Based on Cascade Control Structure Shourui Wang, Chengqiang Yin*, Jie Gao, and Qun Sun Abstract: Path tracking control for the autonomous tractor has been receiving increased attention with the rapid development of modern agriculture. Lateral displacement control is essential for the path tracking effect. The objective of this research is to develop a lateral displacement control system to control the lateral position of tractor. Based on the kinematic model, a cascade control scheme for lateral displacement control system was designed. The two feedback loops in the cascade control structure were implemented using the measurements of the Beidou receiver and gyroscope respectively. The yaw rate controller was designed using IMC-PID technique, and the lateral position controller was devised as a PID form using the method of minimum sensitivity. A set point filter was added in the outer loop to improve the tracking performance. The simulation results demonstrated the efficiency of the proposed control scheme by showing fast response, control accuracy and robust performance for the lateral displacement control system. Keywords: Agricultural tractor, automatic navigation, cascade control, lateral displacement, PID controller.
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INTRODUCTION
Agricultural modernization has been realized in most field operations with the help of the government such as tillage, harvesting, weeding, land preparation etc. [1]. With the development of intellectualization of agriculture technology, automatic navigation technology of agricultural machinery is more important for modern agricultural equipments. It can result in reduced reliance on manual labor, increased product quality and lower production costs, so it has been an active area of study for the automation of agricultural machines [2–5]. The goal of the autonomous navigation in agriculture is to control the trajectory of the vehicle to keep it within a constant distance to the adjacent driving line [6]. Usually, the navigator equipped on vehicles is used to set desired path for the vehicle. Pathtracking algorithm executed in the navigation controller generates the steering angles of the vehicle according to the error both of the heading and the position. To handle variable operating conditions, the path-tracking algorithm should be robust as well as good tracking performance. The control accuracy of path tracking is essential for an agricultural tractor navigation system. As a crucial issue for the navigation controller, path tracking technique has attracted many researchers to propose more and more effective path tracking algorithms [2]. Generally, the path
tracking methods are classified into two types: model-free methods and model-based methods. Model-based method can be further divided into the kinematics model-based method and dynamics model-based method [7]. As for the model-based method, the control performance highly depends on the accuracy of the model de
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