WO2008135867A2

WO2008135867A2 - Precision weeders

Info

Publication number: WO2008135867A2
Application number: PCT/IB2008/002103
Authority: WO
Inventors: Hans-Werner Griepentrog
Original assignee: University Of Copenhagen
Priority date: 2007-05-08
Filing date: 2008-05-08
Publication date: 2008-11-13
Also published as: GB0708862D0; WO2008135867A3

Abstract

The invention provides a method for intra-row and/or inter-row weeding of crop plants, and a controller and apparatus for achieving the same. The method is for tilling the soil between crop plants using a rotor device with a rotating tine rotor having a tine offset from an axis of rotation, a rotational speed and a translational speed. It includes the steps of: (i) predicting a trajectory of the tine; and (ii) if the minimum distance between the predicted trajectory and a crop plant position is less then a threshold distance, changing the predicted trajectory of the tine by changing the rotational speed of the tine rotor.

Description

PRECISION WEEPERS

FIELD OF THE INVENTION

[0001] This invention relates to the mechanical intra-row and inter-row weeding of crop plants.

BACKGROUND

[0002] In recent times there has been an increasing desire in the agricultural production industry for mechanical weed control within crop rows. This is particularly so within the organic farming industry where hand weeding is an inefficient and expensive alternative to band spraying with chemical herbicides.

[0003] In particular, there is a demand for precision weeders that can perform both inter-row weeding (in the area between crop rows) and intra-row weeding (between crop plants within a crop row).

[0004] Modern seeding processes can result in accurate, even distributions of crop plants. Such even distribution lends itself to mechanical weeding. Further, if seeds are accurately placed in known positions when they are initially sown, then the "seed maps" recorded during sowing can be used to provide mechanical weeders with an in-built map of crop plant locations.

[0005] Such an operation is described in the publication "Autonomous intra-row rotor weeding based on GPS", H. W. Griepentrog et al., CIGR World Congress: Agricultural Engineering for a Better World, 3-7 September 2006. Here, when analysis indicates that a tine will come within a specified distance of a known seed location then that tine is 'switched' to a position in which it is no longer active. A disadvantage of such an arrangement is that the mechanical design of the tine rotor is complex, as is the system required to control the switching.

SUMMARY OF THE INVENTION

[0006] The present invention is generally concerned with a method of intra-row and/or inter-row weeding of crop plants by predicting the trajectory of a tine of a rotating tine rotor and adjusting the rotational speed of the tine rotor if the predicted trajectory is too close to a crop plant position. The design of the tine rotor is therefore simple in comparison with the tine rotor of Griepentrog, described above. Moreover, the tines are fixed, not moving, and so the tine rotor is more robust and less complex.

[0007] In a first aspect, the present invention provides an automated method of tilling the soil between crop plants using a rotor device with a rotating tine rotor having a tine offset from an axis of rotation, a rotational speed and a translational speed, the method including the steps of:

(i) predicting a trajectory of the tine; and

(ii) if the minimum distance between the predicted trajectory and a crop plant position is less then a threshold distance, changing the predicted trajectory of the tine by changing the rotational speed of the tine rotor.

[0008] In this way, a change in the nominal spacing of crop plants can be accommodated and/or a deviation of the position of a crop plant from its nominal position can be coped with. In this context, the change in rotational speed of the tine rotor can be an increase in rotational speed, or a decrease in rotational speed.

[0009] The following are optional and/or preferred features of the present invention, which may be combined, either alone or in combination, with the first aspect, or with any other aspect.

[0010] The method may further include the step of:

(iii) if the translational speed of the tine rotor changes, maintaining the predicted trajectory of the tine by controlling the rotational speed of the tine rotor.

[0011] The tine rotor may have a plurality of tines offset from the axis of rotation and steps (i) and (ii), and optionally (iii), are performed for each tine.

[0012] The method may further include the initial step of selecting the number of tines in accordance with a nominal spacing between the crop plants. In addition, or alternatively, the method may further include the initial step of selecting a distance by which the or each tine is offset from the axis of rotation in accordance with a nominal spacing between the crop plants.

[0013] In some embodiments the method further includes the initial step of detecting a position of a crop plant. In alternative embodiments the method further includes the initial step of determining the position of a crop plant from a mapped seed position.

[0014] The rotor device may further include a second rotating tine rotor having a tine offset from an axis of rotation, the two tine rotors rotating in opposite directions. In some embodiments the two tine rotors are laterally opposed. [0015] In a second aspect, the present invention provides a method of tilting soil around a row of crop plants using a rotor device having a tine rotor with a tine, the tine rotor rotating about an axis of rotation and the tine being offset from the axis of rotation, the method including the steps of:

(i) translating the rotating tine rotor along a path substantially parallel to the row of crop plants such that the tine travels through the soil along a tine trajectory, the extremities of which define a treatment zone;

(ii) determining the position of a crop plant in the treatment zone, predicting a future tine trajectory, and calculating the minimum distance between the future tine trajectory and the position of the crop plant; and

(iii) if the calculated distance is lower than a threshold distance, producing an altered future tine trajectory by controlling the rotational speed of the tine rotor, the altered future tine trajectory having a minimum distance to the position of the crop plant which is greater than the threshold distance.

[0016] In a third aspect, the present invention provides a controller adapted to perform the step of controlling the rotational speed of the or each tine rotor according to the first aspect.

[0017] In a fourth aspect, the present invention provides tilling apparatus for tilling the soil between crop plants, including: a rotor device with a rotatable tine rotor having a tine offset from an axis of rotation; a variable speed drive for the tine rotor; a controller for controlling the variable speed drive, the controller being programmed to change the rotational speed of the tine rotor in response to a detection of a minimum distance between a predicted tine trajectory and a crop plant which is lower than a threshold distance.

[0018] The following are optional and/or preferred features of the present invention which may be combined, either alone or in combination, with the fourth aspect, or with any other aspect.

[0019] The controller may be programmed to control the rotational speed of the tine rotor in response to a change in translational speed of the tine rotor.

[0020] The tine rotor preferably has a plurality of tines offset from the axis of rotation. [0021] In some embodiments the apparatus further includes an image capture device for detecting the position of a crop plant. The image recognition device may be a camera.

[0022] The tine may include a blade portion, a disc portion and/or similar for optimising soil disturbance.

[0023] In some embodiments the rotor device includes a second rotatable tine rotor having a tine offset from an axis of rotation, the two tine rotors rotating in opposite directions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] An embodiment of the invention is now described by way of example, with reference to the accompanying drawings in which:

Fig. 1 is a schematic overview of a weeder according to an embodiment of the present invention;

Fig. 2 illustrates the operation of a single tine rotor weeder according to an embodiment of the present invention;

Fig. 3 illustrates the operation of a double tine rotor weeder according to an embodiment of the present invention;

Figs. 4a and 4b illustrate exemplary tine trajectories of a single tine rotor according to an embodiment of the present invention operating under different conditions; and

Figs. 5a and 5b illustrate exemplary tine trajectories of a double tine rotor according to an embodiment of the present invention operating under different conditions.

DETAILED DESCRIPTION

[0025] The same reference numerals are used to indicate like parts throughout the drawings.

[0026] Fig 1 shows, schematically, a weeder 100 according to an embodiment of the present invention being used for the treating of weeds 200 between crop plants 300. In the figure, the weeder 100 travels from left to right, as indicated by the arrow at the top of the figure. The main constituent parts of the weeder 100 are the tine rotor 10, variable speed drive 20 and controller 30. Weeder 100 also includes a crop plant sensing system 40 for determining the position of crop plants 300. [0027] The tine rotor 10 includes four tines 12. In use, as shown in Fig. 1 , the tips of the tines 12 penetrate the soil surface 400. Rotation of the tine rotor 12 therefore causes the tines 12 to till, or cultivate, the soil and, in doing so, to cut, uproot, or otherwise damage or remove the weeds 200. The tilling process also aerates the soil, thus contributing to increased soil biological activities. Tines 12 can include blade portions and/or discs (not shown) at the tip to optimise soil disturbance.

[0028] The variable speed drive 20 includes motor 22, gearbox 24 and motor encoder 26. The gearbox 24 transmits torque from the motor 22 to the tine rotor 10. The motor encoder 26 transmits data about the tine rotor rotational speed and angular position from the motor 22 to the controller 30. Alternatively the sensor for providing the angular rotor position could be placed at the tine rotor itself (not shown).

[0029] The crop plant sensing system 40 also transmits data to the controller 30. Camera 42 mounted on arm 44 captures images of the ground ahead of (i.e. to the right of, as shown in Fig. 1 ) the tine rotor 10. Crop plant position detector 46 analyses the images captured by the camera 42, uses object recognition techniques to recognise crop plants 300, and determines the position of those recognised crop plants 300. This position data is then transmitted to the controller 30.

[0030] In an alternative embodiment, the crop plant sensing system 40 is replaced by a map of crop plant positions. Such a map could be created from, for example, a "seed map" generated by a seeder during seed sowing. When the geographical position of the seeder is accurately identified, e.g. by use of a GPS system, it is possible to accurately map the position of the sowed seeds so that the generated seed map can be accurately positioned and orientated at a later date by the weeder. The weeder 100 can assume that a crop plant 300 has sprouted from each sown seed.

[0031] In a further alternative embodiment, the weeder 100 includes both a map of crop plant positions and a crop plant sensing system 40. The crop plant sensing system 40 could be used as a back-up, to check for anomalies in crop plant positions.

[0032] Controller 30 thus has as inputs the data from the variable speed drive 20 and crop plant sensing system 40, as described above, and data relating to the translational (i.e. forward) speed of the weeder 100. The latter may be determined in a number of ways, such as by using GPS data or by determining the speed of the vehicle carrying the weeder 100. The output of the controller 30 is a control signal 32. [0033] In use, the controller 30 performs the following steps:

(i) prediction of the trajectories of tines 12;

(ii) analysis of these predicted trajectories to determine whether the minimum distance between each of the predicted tine trajectories and each of the crop plant positions is less than a threshold distance; then, if there is a predicted low minimum distance,

(iii) determination of a new rotational speed of the tine rotor 10 which would result in minimum distances between tine trajectories and crop plant positions which are more than the threshold distance; and

(iv) output of control signal 32, instructing the variable speed drive 20 to change the rotational speed of the tine rotor 10 accordingly.

[0034] Fig. 1 shows a single tine rotor weeder. In an alternative embodiment, the weeder can include two tine rotors, each rotating at the same speed, but in opposite directions. In a preferred embodiment the two tine rotors are synchronised so that the tine trajectories of one rotor is a mirror image of those of the other. In another embodiment, the two tine rotors are laterally opposed. Figs. 2 and 3 show, schematically, the operation of a single tine rotor weeder and double tine rotor weeder, respectively.

[0035] Fig. 2 shows a single tine rotor 10 with four tines 12. The tine rotor rotates clockwise, and moves from left to right, as illustrated. In the wake of the tine rotor 10 is a treated zone 500, and ahead of the tine rotor 10 is a treatment zone 600. The rotational axis of the tine rotor 10 moves along a path substantially in line with the row 310 of crop plants 300.

[0036] Similarly, the tine rotors 10a, 10b of Fig. 3 each have four tines 12, and move from left to right, as illustrated. The tine rotors leave a treated zone 500 in their wake, and approach a treatment zone 600. However, the tine rotors rotate differently: tine rotor 10a rotates clockwise, while tine rotor 10b rotates anticlockwise. The two tine rotors are synchronised so that the positions of the tines 12 on tine rotor 10a is the mirror image of the positions of the tines 12 on tine rotor 10b. This ensures that the trajectories produced by the tines of each tine rotor are mirror images of one another. Also, the point at which the loci of the tines of each tine rotor 10a, 10b meet follows a path substantially in line with the row 310 of crop plants 300.

[0037] Figs. 4a and 4b show the trajectories of four tines 12 of a single tine rotor 10. The tines 12 of the tine rotor 10 are spaced 0.2m apart such that, when the tine rotor 10 has zero translational speed, the locus of the tines 12 is a circle with diameter of 0.2m. In Fig. 4a the crop plants 300 are spaced apart by 0.157m and the ratio of rotational speed to translational speed is 1.0. In Fig. 4b the crop plants 300 are spaced apart by 0.3m. The ratio of rotational speed to translational speed of the tine rotor 10 is reduced to 0.525 to ensure that the tine trajectories do not pass through, or too close to, a crop plant 300.

[0038] Similarly, Figs, 5a and 5b show the trajectories of the tines 12 of two tine rotors 10a, 10b. Each tine rotor has four tines, spaced 0.15m apart such that, when the tine rotor has zero translational speed, the locus of the tines 12 is a circle with diameter of 0.15m. In Fig. 5a the crop plants are spaced 0.12m apart and the ration of rotational speed to translational speed is 1.0. In Fig. 5b the crop plants 300 are spaced apart by 0.3m, and the ratio of rotational speed to translational speed is reduced to 0.391 to ensure that tines 12 do not interfere with crop plants 300, as in Fig. 4b described above.

[0039] Figs. 4a to 5b demonstrate how the rotational speed of the tine rotor(s) can be varied (assuming the translational speed remains constant) in order to change the tine trajectories. This change can be in response to a single crop plant whose position has deviated from the nominal position, or can be in response to a change in the nominal spacing of crop plants.

[0040] Alternatively, or in addition, the design of the tine rotor or tine rotors for a weeder of the present invention may be adapted to the spacing of the crop plants. In particular, the number and/or spacing of the tines may be selected to ensure that, at a particular translational speed and rotational speed, the tine trajectories will not interfere with the nominal positions of the crop plants.

[0041] The skilled person will appreciate that the embodiments described above are just some examples of a weeder incorporating aspects of the present invention. Many variations are possible within the scope of the invention.

Claims

1. An automated method of tilling the soil between crop plants using a rotor device with a rotating tine rotor having a tine offset from an axis of rotation, a rotational speed and a translational speed, the method including the steps of:

(i) predicting a trajectory of the tine; and

2. The method of claim 1 , wherein the method further includes the step of:

3. The method of claim 1 or claim 2, wherein the tine rotor has a plurality of tines offset from the axis of rotation and steps (i) and (ii), and optionally (iii), are performed for each tine.

4. The method of claim 3, wherein the method further includes the initial step of selecting the number of tines in accordance with a nominal spacing between the crop plants.

5. The method of any one of claims 1 to 4, wherein the method further includes the initial step of selecting a distance by which the or each tine is offset from the axis of rotation in accordance with a nominal spacing between the crop plants.

6. The method of any one of claims 1 to 5, wherein the method further includes the initial step of detecting a position of a crop plant.

7. The method of any one of claims 1 to 5, wherein the method further includes the initial step of determining the position of a crop plant from a mapped seed position.

8. The method of any one of the preceding claims, wherein the rotor device further includes a second rotating tine rotor having a tine offset from an axis of rotation, the two tine rotors rotating in opposite directions.

9. A controller adapted to perform the step of controlling the rotational speed of the or each tine rotor according to the method of any one of claims 1 to 8.

10. Tilling apparatus for tilling the soil between crop plants, including: a rotor device with a rotatable tine rotor having a tine offset from an axis of rotation; a variable speed drive for the tine rotor; a controller for controlling the variable speed drive, the controller being programmed to change the rotational speed of the tine rotor in response to a detection of a minimum distance between a predicted tine trajectory and a crop plant which is lower than a threshold distance

11. The apparatus of claim 10, wherein the controller is programmed to control the rotational speed of the tine rotor in response to a change in translational speed of the tine rotor.

12. The apparatus of claim 10 or claim 1 1 , wherein the tine rotor has a plurality of tines offset from the axis of rotation.

13. The apparatus of any one of claims 10 to 12, wherein the apparatus further includes an image capture device for detecting the position of a crop plant.

14. The apparatus of claim 13, wherein the image capture device is a camera.

15. The apparatus of any one of claims 10 to 14, wherein the tine includes a blade portion for optimising soil disturbance.

16. The apparatus of any one of claims 10 to 14, wherein the tine includes a disc portion for optimising soil disturbance.

17. The apparatus of any one of claims 10 to 16, wherein the rotor device includes a second rotatable tine rotor having a tine offset from an axis of rotation, the two tine rotors rotating in opposite directions.