Development and Application of Heavy-lift Drones for Agricultural Spraying
Drones have been used for agricultural spraying in many countries. Pro Agrotech’s team have been working on technologies related to aerial spraying of agrochemicals since 2015. An integrated platform, Drone-based Agricultural Spraying System (DASS) has been developed to connect the growers, the spraying service providers, the agrochemical suppliers, and crop protection professionals. An array of aerial spraying facilities have been tested including drones, manned light aircrafts, and land machineries, of which, drone sprayers proved to be the most versatile, flexible and scalable tool and may become the next generation agricultural spraying equipment.
The downside of the using drones for agricultural spraying is the limited payload, currently at around 15 kg, determined by the mass ratio of lithium ion battery power pack. This makes drone spraying less competitive in terms of both adaptability and cost effectiveness.
Therefore, we initiated a project developing heavy-lift drone for agriculture spraying, through integrating advanced technologies of different disciplines. A number of pilot tests have been conducted for concept verification in the past few years. Recently, we have entered into collaboration with University of Birmingham to develop a prototype heavy-lift drone for agricultural purposes, utilizing Pro Agrotech’s expertise in agricultural application of drones and the innovative technology developed by High Performance Turbo-machinery Research Centre, the University of Birmingham.
The power system of Heavy Payload Agricultural Drone
Schematic diagram showing the general design of the power and lift system of the heavy-lift drone.
TREX engine 45 CC 58 HP
Test of different types of frame design
The purpose is to identify a frame design most suitable for the specific application of the heavy-lift drone. Weight, strength, structure, maintenance, cost are the factors taken into consideration in designing and testing process.
Development and test of flight control system
The flight controller (FC) interprets navigation can command and calculate the required position with the current GPS location. Velocity, altitude and course are well-calculated and the aircraft moves to the next position. FC automatically applies attitude control by sensing the difference between the aircraft frame and a 3D horizon. Minor corrections due to turbulence can be automatically managed to ensure a stable flight system. The spraying control system is linked with FC to ensure accurate application.
Development and test of Radio Communication system
C&C systems are to be adopted in Radio communications. They can provide typically 2km and up to within 20km line of sight control within the 868-915MHz frequency bands. Besides, the mature and reliable telemetry & video technologies will be integrated into the flight system, which will achieve the mapping accuracy at Centimeter level and upload the mapping data via wireless transmission.
Development and test on Object detection and avoidance
Biovular vision, 3D sensing system, infrared sensing system, ultrasonic obstacle avoidance module has been each tested and the combination will be used in the object detection and avoidance system.
It is under designing that at the front, rear and base part, the MMW radar obstacle avoidance system is to be installed each to identify obstacles with a radius greater than 3cm beyond 25m and avoid autonomously.
Due to the complication in field, the drone is also to be designed to hover autonomously when unexpected obstacles encountered. The forward function will be locked automatically before the danger is removed or relieved.
The test of mission planning in field
The Mission Planning (MP) has been under designing. The automated and optimized grid pattern algorithms have been under testing to minimize the flight times, and it will allow a programmed overlap between paths.
Our purpose is to make the MP smarter, more functionality and stronger adaptability in multiple field conditions.
The MP can be done on its flight control computer and ground station software and allow specific operator command and control functions and data displays. It can be performed at office before the mission and stored for re-use later.
With ground site double check, the MP will be quick and accurate as well as repeatable. In addition, the already known no-fly zones can be marked before flight and newly NFZ can be manually added during operation.
The design and test of rotary sprayer and flow controller
The spraying system has been under a long-time research and field tests. We adopt the rotary sprayers to ensure the chemicals droplets at required sizes and to be evenly distributed on the foliage.
To deal with the complications of field conditions where the drones fly at various speed and acceleration rate, a versatile flow controller and pump system need to be tested to ensure even spraying.
The location, speed and flow rate also need to be monitored continuously for future review and quality control purposes.
