Design and experiment of a self-propelled target spraying machine for walnut orchards based on infrared laser sensing

Spraying is an important operation for walnut orchards. To solve the problems of serious liquid waste, low operation efficiency and efficacy, high labor intensity and risk of health impact that existed in current spraying operations in walnut orchards in Xinjiang, a self-propelled target spraying machine was designed, fabricated and tested. Using the method of infrared laser ranging, the walnut tree canopies were detected and an automatic target spraying control system was developed. The structure, operation principle and design of key components of the machine were introduced. To improve the spraying accuracy, an operating speed-based time delay control strategy was designed and implemented. Field experiments showed that compared with continuous spraying, target spraying could save liquid consumption by 22.0%, 24.1% and 26.1% when the operating speeds were 0.4 m/s, 0.7 m/s and 1.0 m/s, respectively. The droplet deposition amounts at all seven sampling points reduced as the machine’s operating speed increased and the orifice diameter of the nozzles decreased. However, the sprayed liquid was able to cover the whole canopy region of the walnut trees under all speed and orifice diameter combinations. When the operating speed varied, the delay distances for nozzle opening and nozzle closing were kept stable, with average values being 0.135 m and 0.184 m, respectively, which indicates that the operating speed-based time delay control strategy was effective.