Autonomous robots for precision crop protection in vegetables and fruit production

In fruit growing, spray application is a time consuming operation, mostly consisting of driving back and forth through the orchard. The same situation is valid in vegetable production where repeated spray applications are required to keep for example strawberries in good condition. Therefore, a reduction in time consumption for spray operations directly influences the costs of spray operations by not having an operator on the tractor. Though, autonomous spraying is quite a challenge as has been shown in former projects throughout the world. Handling the variability in growth stages, crop types and biomass quantity is a requirement to spray autonomously in crops. Technological breakthroughs in automated spraying and in autonomous navigation were required to realise true autonomous robots for precision crop protection.
Our project was started to develop sensor based spraying systems for fruit orchards and strawberry fields and to operate these systems autonomously in the field. In fruit orchards the investigated automated sprayer was based on a laser ranger system as sensor. In strawberry fields the sensor system used was based on the near infrared difference vegetation index. Sensor data was gathered and algorithms were made to convert raw signals into spray application actions. The algorithms work in real time operations and sensor and application data was recorded for tracking and tracing purposes.

The autonomous operations are performed by a tractor driving on RTK-GPS. In developing this autonomously operating tractor the steps of driving by wire, navigation control and safety system were performed. Finally the autonomous operation was linked to the spraying operations to realize precise control in the field. The tractors used in these projects were a Fendt vario 209 for the fruit orchard, and a New Holland Boomer tractor for the strawberry field operations. To operate safely in the unstructured environment special effort was put into the safety and monitoring systems of the autonomous vehicles. Sensor systems were developed to determine whether obstacles are in the path of the tractor. Emergency stop systems were applied to realize a safe system that can be put into practical applications and can be marketed by commercial partners in agricultural business.

At the end of the projects successful demonstrations were given to the public domain. Growers and industry were shown the achievements and the feasibility of the technology developed. Currently the technology is brought from the prototype and research stage to the production and marketing stages. The developments and results achieved with both spraying and autonomous operation systems are explained in this abstract.