Autonomous robotic vehicle development for greenhouse spraying

Application of nutrients, fungicides, and pesticides is one of the most important processes in agricultural production and can have a significant impact on yield, quality, and ultimately profitability. However, fungicide and pesticide application can create significant environmental and human safety concerns. The motivations behind the development of an autonomous vehicle for greenhouse sprayer applications are to improve chemical delivery, reduce labor requirements, and minimize labor hazards. This research focuses on the development of a prototype vehicle platform that can be used in greenhouse sprayer applications. A six-wheel differential steering vehicle was designed and built to act as a greenhouse sprayer. Power was transmitted from two independent DC drives to the wheels through chain and sprocket transmission. A fuzzy logic-based proportional-derivative controller was developed to navigate the vehicle through simulated greenhouse aisles using range information provided by ultrasonic sensors. The vehicle was tested on sand and concrete surfaces using two modes of operation. In self-contained mode, the vehicle carried a self-contained spraying system, while in trailer mode, the spraying system was mounted on a pull-behind trailer that was towed down the aisle. Results show that the self-contained mode performed better than the trailer mode on both sand and concrete. There was an average RMS path error less than 2.5 cm for an aisle width of 61 cm and an instantaneous average error less than 6.4 mm. The robotic sprayer successfully navigated 45.7 cm, 50.8 cm, and 61.0 cm aisle widths.