Autonomous speedsprayer using differential global positioning system, genetic algorithm and fuzzy control

A fuzzy controller was developed for the autonomous operation of a speedsprayer in an orchard. The autonomous operation with a fuzzy controller was graphically simulated under the real orchard conditions. A differential global positioning system (DGPS) receiver was used to determine the direction of travel and four ultrasonic sensors were used to detect obstacles during operation. The results of the simulation showed that the speedsprayer could be operated autonomously with the fuzzy controller combined with the DGPS receiver and the ultrasonic sensors. The DGPS receiver signal, and the signals from the ultrasonic sensors, were processed in real time. The speedsprayer was modified to be steered by two hydraulic cylinders. The fuzzy controller has two inputs: direction of travel and distance from obstacles. The operating time of the hydraulic cylinders was inferred as output of the fuzzy controller. The results of the field test showed that the speedsprayer could be autonomously operated within 50 cm deviation. The ultrasonic sensors did not contribute to the improvement of guidance performance. The speedsprayer, however, could avoid trees or obstacles in emergency situations with them. According to a computer simulation, performance of the fuzzy controller was improved by 68% using a genetic algorithm. However, according to the field test, performance of the fuzzy controller using the genetic algorithm was not improved much because of tyre slip and response time gap of the hydraulic system. (C) 2000 Silsoe Research Institute.