Controller for agricultural sprayers

Details Controller for agricultural sprayers Controller for agricultural sprayers

1997-04-24

1999-07-20

Price, Thomas

Plant husbandry

Material distributor with plant manipulating, cultivating or...

A01C 1500, A01G 1500

Patent

active

059242396

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

THIS INVENTION relates to agricultural sprays used to spot spray weeds and the like. In particular the invention relates to a controller by which the spot sprays are selectively activated on determination of the existence of a weed.


BACKGROUND ART

AU-B-37775/89 (618377), the Australian national phase of PCT/AU-89/00267 (WO-89/12510), The Minister for Agricultural and Rural Affairs of the State of New South Wales, discloses a controller for agricultural sprayers where sensors measure the irradiance and radiance (or irradiance and reflectance) of a target area in two bands (eg. red and near infra-red) of the electromagnetic spectrum. The measurements are used to control the spray. Control involves a determination of the relationship between the ratios of the radiance (or reflectance) to the irradiance in each band respectively. The major flaw in this system is that it does not cope with changing light conditions or partly shaded areas in the viewing area. Further it does not provide a size selection function. The plant or weed size at which the controller acts is not able to be adjusted.
Colour analysis is the basis of a variety of discrimination systems operating in a range of circumstances. Examples are seen in U.S. Pat. No. 4,653,014 (Omron) and U.S. Pat. No. 4,797,738 (Tohken). These operate with video signals, operating on components therein to establish the existence of a target condition. In Omron there is seen a totally digital system which uses the R/S, G/S, and B/S signals (where S=R+G+B and R, G, and B are the red, green and blue components of the video signal). This system defines specific colour by analyzing its three signals with reference to upper and lower limits. In Tohken the signals Y (luminance), R-Y and B-Y are compared each with two limit values and analysis determines specific colour. Neither of these systems enables use with sprays in the field where an area which is predominantly green, a weed or other target plant, is to be found in an area of another colour, usually colours such as brown which return a green component in a camera output.


OBJECT OF THE INVENTION

It is an object of the present invention to provide a controller for agricultural sprays, which controller is able to function at normal operational speeds and under varying light conditions, to efficiently locate weeds and other target plants in the field. Other objects and advantages will hereinafter become apparent.


BRIEF SUMMARY OF THE INVENTION

In one aspect, the present invention resides in an agricultural spray controller by which detection of plants on a surface being treated is effected so as to enable the spot application thereto of a spray, said, spray controller comprising: spraying of a plant; effect spraying on detection of a plant; for viewing an area of the surface to be treated and generating an output representative of the field of view; and control circuitry in the control means coupled to the output of the detector, said control circuitry analyzing the detector output and generating said control signal depending on the detection of a plant; colour components of the video signal, noting pixels which are predominantly green, and generating the control signal when the number of predominantly green pixels in an area of the field of view indicates the existence of a green plant.
Evaluation of various plants of interest and their typical backgrounds (soil, rock, stubble, etc) has shown that green foliage has a Green content higher than the Red and Blue content. The same also holds true for the so called colour difference signals, typically denoted as R-Y, B-Y, and G-Y, where Y is luminance. There are some advantages to working with the colour difference signals. The first is that by using the difference signals the effects of ambient light levels can be largely ignored. A second advantage is that CCD cameras with colour difference outputs are more likely to be available. In the ensuing discussion where the system is described without specific reference to luminance either form o

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Saunders,Frederick A., "A Survey of Physics for College Students", Range of Electromagnetic Waves, Chapter 35, 550-566, Sep. 1930.

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