Coordinating control for an agricultural vehicle with individual wheel speeds and steering angles [Applications of Control]

Automatic navigation of agricultural vehicles, such as tractors and harvesters, can increase the level of automation in the agricultural process, thereby lessening the human workload. In the agricultural environment, where vehicles move on uneven terrain, achieving maneuverability and mobility can be difficult, particularly when the path curvature is small or vehicle orientation and path tracking must be independently controlled. To obtain the desired maneuverability and mobility, one approach is to individually actuate the drive and steering functions of each wheel on a four-wheeled vehicle. For sensing and navigation, this prototype vehicle uses a combination of machine vision, a differential global positioning system (DGPS), and an inertial measurement unit (IMU). The focus of this work, however, is on path-following control. Although the vehicle is highly maneuverable due to its eight independent actuators, precise control is difficult due to the overconstrained nature of the actuation.