Tillett and Hague Past
Projects
Autonomous Crop Treatment Vehicle
Computer vision based,
guidance system for non-chemical weed control
Weed mapping in agricultural crops and on
railway lines
High work rate vision guidance spanning multiple independently drilled bouts
Tillett and Hague Home
Autonomous
Crop Treatment Vehicle (1993-1996)
One way to reduce agrochemical use is through spatially selective
operation; a map of the variability within a field is used to decide
how to selectively treat areas of typically 5 m by 5 m resolution from
a tractor equipped with GPS. We proposed an alternative but complementary approach based
upon real time detection of targets, be they crop or weed. This allowed
a much finer resolution, down to individual plants, and required little
prior knowledge of the field except an estimate of planting geometry.
We named this concept plant scale husbandry, and chose as an example
task the selective application of chemical to a transplanted
cauliflower crop.
Highly targeted individual plant scale operations may be
too slow for manned vehicles. We therefore developed an autonomous
vehicle as a platform for experimental plant scale operation. A
treatment device consisted of an array of solenoid operated nozzles at
50 mm pitch. Selective treatment was achieved by switching each
individual nozzle on or off as the vehicle progressed through the crop.
The planting pattern of the crop, imaged by a vehicle mounted
camera, was tracked using an extended Kalman filter. To allow for
reliable navigation, including headland turns, the Kalman filter also
integrated odometric and inertial sensor data. In addition to providing
guidance information, tracking the crop pattern allowed the
discrimination of crop - which matched the planting pattern - from
weeds which did not.
As the vehicle progressed along the row, the results of crop / weed
classification were accumulated over several views of each area of
ground. The local treatment map constructed was used to select spray
nozzles to give selective treatment - in this example, crop plants were
treated whilst avoiding weeds.
This project was funded by The Douglas Bomford Trust and the BBSRC.
Click on this link to see a 35 second 3MB Windows Media File
format video of the autonomous vehicle in action.
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Computer vision based, guidance system for non-chemical weed control
(1997-2001)
This
project was concerned with reducing agrochemical inputs through the use
of inter-row cultivation to control weeds. This practice goes back to
Jethro Tull's invention of the seed drill in the 18th Century. However,
the advent of herbicides all but eliminated inter-row hoeing in the UK. Our objective
was to reinvigorate this environmentally friendly technique and make it
commercially viable again by the application of modern robotics
technology. Defra funded an investigation into the potential for use in
cereals and with support from the British Beet Research Organisation we
extended the research to cover sugar beet. Within this project we
collaborated with ADAS, IACR, Garford Farm Machinery, Robydome
Electronics and KRM Ltd.
The principle technical problem was to
locate and track the crop rows such that cultivators could be brought
into close proximity to crop plants, thus maximising weed kill, without
reducing yield. We chose to develop a non-contact sensing system using
low cost CCD video cameras and computers. This approach had the
advantage of being very flexible in respect of alternative crops and
growth stages. However, in agricultural fields we were faced with a
number of challenges. These included naturally variable lighting, crop
emergence that may be incomplete and weeds that tend to mask crop rows.
Our
approach had two principle innovative steps. The first was in the
initial image processing in which we exploit prior knowledge of crop
row spacing to identify crop rows. The second was in the application of
a tracking algorithm to track row location between images. Together
these give very reliable performance under a wide range of conditions
typically placing cultivators well within +/-3cm at speeds of up to
10kph and beyond. This performance has proved commercially attractive. Working
with Garford Farm Machinery and Robydome Electronics we brought a
product to market in 2001 under the brand name Robocrop.
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Weed
mapping in agricultural crops and on railway lines
Weeds present a significant maintenance issue on railway lines.
Normal control methods are based on a uniform application of
herbicide even though weeds may be patchy, thus putting more herbicide into
the environment than is strictly necessary. Our vision technology
can be used to identify weed patches so that a precise weed map can be
created either to guide future spray applications, or control
spray nozzles in real time.
We used our ability to accurately locate crop rows to deduce weed
density on the basis that green plant material between rows will be
weed. This technique accurately detects weed density at early
stages of crop growth when rows are discrete. We have used
similar techniques to successfully assess crop density. The illustration above
is of an automatically generated weed map in a field of winter wheat
grown on a 25cm row spacing. The technique could be applied to a
wide range of agricultural and horticultural crops and linked to either
weed map generation or real time sprayer control.
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High work rate vision guidance spanning multiple independently drilled bouts (2002-2005)
Inter-row cultivation and band spraying improve efficiency of
conventional and organic systems alike. However, they are sometimes
difficult to implement due to labour and cost constraints. Vision
guidance has improved this situation, but work rate is still limited due
to the need to span a single drill or transplanter bout widths. In
this project we set out to further improve the generic technology for
precision vision guidance and to develop new technologies for spanning
multiple drill/planter bouts. We chose to demonstrate the
technology on two machines. The first was a specially constructed
12m wide inter-row hoe spanning three cereal drill bouts. The
second was a 20m wide precision band sprayer spanning five planter
bouts based on an adapted trailed sprayer.
The experimental hoe was shown to perform well in a wide range of
conditions at speeds of up to 10kph with high accuracy (S.D 10mm).
An investigation into combined hoeing and on-row application of
selective herbicides and other agro-chemicals suggests that the
potential environmental and economic advantages are substantial.
However, the required very narrow (9cm) spray bands over 25cm
cereal rows are difficult to achieve with existing hydraulic nozzle
technology due to the very low (10L/h per nozzle) volumes desired.
Alternative spray technologies are available and further work is
required to assess their performance in this application. Click
on this link to see a 34 second 5MB Windows Media File format video of
the 12m multi-section inter-row cultivator in action.
Experimental evaluation of vegetable band spraying indicated that
accuracy targets (S.D 25mm at 12kph) were met, providing a cost
effective system for reducing chemical inputs. Click on this link to see a 22 second 4MB Windows Media File format video of the 20m vision guided sprayer in action.
Partners
Silsoe Research Institute, HGCA, Garford Farm Machinery, Robydome
Electronics, AGCO Ltd, Micron Sprayers, Unilever, Sheepdrove Organic
Farm, Robert Montgomery Ltd, Abacus Organic Associates, The Allerton
Research & Educational Trust
Government Sponsor
Defra (LK0928)
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