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97 Global Unmanned Spray System | In operation – such as one of the poles carrying the cables that power irrigation pumps – that it decides it cannot drive around. He will then drive the pick-up to the obstacle, wait for the UGV to stop automatically a safe 15 ft away, as it is programmed to do, switch it to manual and use the remote control to drive it around the obstacle, then hit Resume. “It takes him maybe a minute at most, whereas if he had been at the other side of the field it might have taken him five minutes,” he says. If the pole is offset from the centre of the row, the GUSS will drive around it autonomously if it judges that it has enough room. If the obstacle is in the middle of the row, however, it will stop and wait for the supervisor. “Basically, we don’t want it to drive into the trees,” Thompson says. “Typically, when there is a power pole situation like that, the grower will leave out a few trees just to give the tractors some space to drive around it, but we decided that we don’t want the machine to try to make a drastic turn inside the orchard with all the trees around.” He adds that this typically only happens three times a day at most, a frequency that’s likely to fall anyway as growers develop orchards that are more friendly to robotic equipment, for example by ensuring that the power poles are in line with the trees instead of on the paths. The GUSS can operate 24/7 when the weather allows, stopping to be refuelled every 13 hours. All spraying stops in high winds because of drift, and in rain because that will wash the chemicals off the plants. However, the vehicle will drive safely in the rain, Thompson says. Safe and sound Safety is of course a high priority, and using an unmanned vehicle for spraying provides some inherent advantages here. Only the operators are allowed in the orchards because of the chemicals, the GUSS moves very slowly by design to ensure good coverage of the trees, and its fan is very loud. The vehicle is also fitted with a horn that it honks every time it decides to start moving, providing a 4 s warning. It also has ISO-standard lights that are on continuously when the GUSS is in manual mode but flash in autonomous mode. The Lidar is its active collision avoidance sensor, and the vehicle will automatically stop if it detects an obstacle within 15 ft in front of it. As the Lidar covers only the front segment – to keep costs down – the software will not permit the GUSS to reverse automatically; it has to be done manually. If all else fails, the touch-sensitive front bumper has a direct link to the engine, independent of the software, that will shut down the engine if it comes into contact with anything. There is also a switch on the machine to switch it from automatic to manual mode, an emergency stop button on the back, and an earth connection through the fuel cap that prevents the GUSS from moving if the cap is not securely in place. Putting the GUSS to bed is also straightforward for the operator. It involves spraying any residual material out of the tank, driving the vehicle to where he wants it to stop, switching to manual mode and turning it off with a key and a battery kill switch. The boxes that house the vehicle- mounted remote control hardware and its onboard computer are then locked. GUSS Automation incorporated feedback from CFS tractor mechanics to ensure ease of maintenance, so it uses components such as the engine and hydraulic pumps that can be easily replaced or overhauled when they wear out. “There’s no reason why you can’t operate the GUSS – one machine – for 20 or 30 years,” Thompson says. The company has supplied 10 machines to CFS and six to customers in California, as well as some in Florida with more on order and international interest from Australia, Chile, Brazil, Argentina, Peru, Portugal, Spain and South Africa. The plan is to meet demand from California first, building one machine per week in its newly commissioned factory, then focus on Australia, where it expects to have the first machines in place by the middle of the year. Electrifying the GUSS is a possible future development. However, a more immediate focus is on a smaller version for vineyards, which have smaller plants in more tightly spaced rows, as well automating more tasks, such as pruning, mowing and harrowing, Thompson says. “The hardest part was getting the machine to drive itself with no GPS signal, then turning into the next row,” he says. “As far as what it is doing while it’s in the field, we figure we can develop anything.” Unmanned Systems Technology | February/March 2020 Dimensions: 6 ft 4 in height, 24 ft long, 7 ft 6 in wide Spray tank capacity: 600 US gallons Fan: 36 in, direct drive Sprayer: 32-nozzle manifold with individual shut-offs Engine: 6.7 litre 173 hp diesel Fuel capacity: 90 US gallons Materials: stainless steel tank, hood, roof, engine doors and fan housing, mild steel chassis Control: autonomous with manual remote control option, custom software Comms: cellular Navigation/collision avoidance: GNSS, Lidar, cameras, bumper engine cut-out Some key suppliers Spray dispersal fan: Breeza CNC laser-cut steel sheet: Cencal Engine fan: Clean Fix Engine: Cummins Tubing: Excelsior Metals Gearbox: Funk Manufacturing (John Deere) Sprayer pump: Myers GNSS: Trimble Lidar: Velodyne Specifications