Automatic steering and guidance systems for tractors and farm machinery have developed rapidly during the last ten years and sales are increasing, but the search for guidance systems that assist or even replace the driver began almost 50 years ago.
The first successful driverless tractor was built by engineers at Reading University in 1958. A standard International Harvester tractor was fitted with sensors that followed a network of wires buried below the ground surface. Safety systems stopped the tractor if it strayed from the guide wires or hit a solid object, and the equipment worked so well that a commercial version was developed. At least two guidance systems were sold, both to fruit growers for grass cutting in orchards.
Experiments with driverless tractors operated by radio control followed but, like the buried wires, these had limitations for field work and it was not until the early 1990s that new technologies became available to make guidance systems commercially acceptable. Most of the equipment on tractors and field machinery is based on one of three different technologies and these are signals from the Global Positioning System (GPS) network of space satellites, laser beams and using a computer to analyse photographs of the field surface.
Many salad and vegetable crop growers already use picture analysis, a system developed by Bedfordshire based Silsoe Research Institute (SRI) and demonstrated for the first time in 1996. They built an experimental robot vehicle with a driver’s seat that was needed for guiding it to and from the field. Within the field it worked without a driver in crops growing in rows.
A closed circuit television (CCTV) camera mounted on the front of the vehicle filmed the ground ahead of the wheels, producing images that were scanned by a computer to detect the plant rows. Information from the picture analysis automatically controlled the steering, guiding the wheels between rows of cauliflower plants, the crop used in the development programme.
Work on the robot vehicle was later abandoned, but an improved camera based automatic guidance system is used to steer the frame of the Robocrop tractor-mounted hoe built by Garford Farm Machinery. The hoe, available since 2001, is popular for controlling weeds in field scale vegetables and salad crops as well as other row crops. Its success is helped by pressures faced by growers to reduce herbicide use or switch to organic production.
The hoe’s guidance system analyses 25 pictures every second, allowing the hoe to work at up to 12 km/hr with the blades adjusted to as little as one cm from the crop plants. Users say that it can outperform even a skilled operator, maintaining high levels of accuracy indefinitely.
Garford offers the Robocrop hoe in widths from 1.8m to 12m with the guidance system an optional extra. Vegetable and salad crop growers are easily the biggest customers in the UK, but sales for other crops including organic cereals are growing. There is also an expanding export market that helps to make Garford easily the market leader for this type of equipment in Europe, says Philip Garford. The price of the Robocrop guidance kit is £9,892 to fit a Garford hoe, and kits are also available to convert other makes of steerage hoe to automatic guidance.
Laser technology is used to provide automatic steering for combine harvesters. A laser beam locates the edge of the standing crop while the control system positions the combine to fill the cutting width. Benefits are said to include improved efficiency and, with the steering under automatic control, the driver has more time to concentrate on other aspects of combine operation.
Combine harvesters were also the first farm machines to use GPS technology. This started in the early 1990s with the development of yield mapping systems by Massey Ferguson, but using signals from space satellites to identify the position of a tractor or machine with great accuracy opened a long list of other possibilities. They include soil mapping, varying seed, fertiliser or spray rates automatically to match differences in soil or crop yields plus new guidance systems for tractors and machinery.
The guidance systems have shown the biggest sales increases over the last four years or so. This is partly because many farmers were initially cautious about adopting such unfamiliar technology, partly because many of the early problems over lack of compatibility between different makes of equipment have been resolved and also because prices for the GPS based equipment have fallen as more manufacturers have moved into the market.
Richard Reed, managing director of LH Agro, distributor for the CentreLine range of GPS based equipment, says lower prices are the main reason for the sales increase. List prices for his equipment start at £1,195 plus VAT for their simplest guidance units for parallel tracking. With this equipment the driver operates the steering manually, but a light bar guidance system on an in-cab display unit shows when a steering adjustment is needed.
This type of equipment is accurate to within plus or minus 30cm, enough to improve efficiency by avoiding overlap when working with a tractor and a fertiliser spreader or wide boom sprayer. For many farmers and contractors this is the principle reason why they need guidance equipment, Reed explains, and basic equipment meets their needs.
Vegetable growers who use GPS guidance to improve accuracy for jobs such as seed drilling or bed formation need greater accuracy with prices for suitable LH Agro systems in the £16,000 to £20,000 range. This includes a control unit that operates the tractor’s steering automatically within plus or minus 5cm. It uses a portable field station to enhance the accuracy of the standard GPS signal. Greater accuracy with year-to-year repeatability is available with an RTK type system with a fixed mast as a reference point giving +/- 2cm accuracy.
One of the first companies with GPS based guidance for farm equipment was Patchwork Technologies, and their BlackBox range is popular with farmers and contractors. Prices start at £1,500 for their BBGuide system, and the next stage up is the BBPro at £1,800. As well as guidance for spraying and spreading jobs, these can also improve efficiency by helping to set out a field in convenient blocks for cultivating - and the guidance equipment works in the dark as well as in daylight, says Richard Price.
An optional extra for BlackBox systems is a printer that can be used either in the farm office or in the field to download work data, providing records for future reference and to satisfy protocols on chemical applications.
Some of the leading tractor companies also offer GPS guidance systems, generally through a link with one of the specialist manufacturers. The Claas eDrive system introduced in 2004 is an example. It is available under an agreement with SOYL, a company specialising in precision farming equipment, but fitting is handled by Claas dealers. Like other equipment of this type, eDrive can be fitted to any make of tractor and to self-propelled machines.
Claas eDrive is available in a wide range of versions including a simple GPS linked Outback display unit for parallel tracking. It uses lights to show the driver when a steering correction is needed. At the other end of the scale is an RTK system with a fixed reference point and full steering control.
Trimble equipment is used for the Auto-Guide systems on AGCO’s Challenger and Fendt tractor ranges, and New Holland includes the EZ-Guide equipment on the list of dealer-fitted options for some of their latest tractor models.
John Deere was among the first tractor manufacturers to offer GPS guidance systems as an option. They offer a full range from guidance for manual steering to various AutoTrac automatic systems with hands-free steering. The range includes AutoTrac RTK using a base station to help eliminate small variations in the Standard GPS signal, and this can be equipped with RTK Extend, an exclusive John Deere feature. RTK Extend maintains full accuracy for up to 15 minutes if the signal from the base station to the tractor is temporarily obstructed.
The grading system published by John Deere for the accuracy of their guidance system is a handy reference. Their basic system, AutoTrac SF1, is accurate to +/- 30 cm and is suitable for cultivation work, spraying and lime or slurry spreading. The intermediate SF2 systems give +/- 10cm for harvesting operations, spraying, seeding and spreading, while AutoTrac RTK at the top of the list with +/- 2cm is for the most accurate planting and bedding jobs with repeatability for future operations. l
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