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WEEDINATOR 2018

The WEEDINATOR project continues .... The inevitability of robots working on farms draws ever nearer ....

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In the world of professional agriculture, a lot of focus has been put on large, incredibly expensive machines that work in huge open fields where just one crop is grown. Whilst this is incredibly efficient and produces very cheap food, it's not good for pretty much everything else!
There does exist a substantial backlash against this farming model where small farmers grow 'organic' vegetables on small farms with respect to the environment and indigenous wildlife.
Although robots have a bad rep for stealing our jobs, there are some jobs that most people just don't want to do. Not only are these tasks boring, but they can often tip the wage scales over the minimum threshold and make small farms financially unviable.
Here I introduce the Weedinator - an autonomous agricultural electric tractor that can be used on small farms to cultivate, till and weed seed beds. It will travel up and down 56 inch wide beds, several times a day if necessary.

License: Attribution-NonCommercial-ShareAlike 2.5 Generic (CC BY-NC-SA 2.5)

2018 sees the project moving forwards with the addition of a side project managed by Jonno which uses a skid steer system and higher powered drive motors. It will use the same control system as the WEEDINATOR.

This year we've also got more people on the team, including Tristan Lea, a successful open source entrepreneur, who apart from having superb technical skills, has actual open source business experience.

Also, the WEEDINATOR will be exhibited at the Liverpool MakeFest, 30th June 2018 https://lpoolmakefest.org/ and myself and Jonno will be available for intelligent conversation.

Project logs will be updated soon with development of the control system, featuring a 3 core MCU, ultra precision GNSS and more ...... so please subscribe!

Project challenges:

  • Designing steering geometry that does not impinge on the planted crop - I did not want to use skid steer so a more complicated steering system is required with full 'differential' where speeds of steering and drive motors individually change according to steering and drive parameters eg forwards, backwards, clockwise etc.
  • Selecting suitable motors and gearboxes - Cost is a major factor and the minimum requirement was that there should be optical encoders for monitoring 'steps' and speed. Other similar skid steer designs would use 24v truck windscreen wiper motors but these were thought to be too basic.
  • Preventing abrasion and jamming of the CNC mechanism due to soil and dust - gaiters, rubber boots, wipers, delrin bearings ..... the list of solutions goes on!
  • Selecting suitable power supply for motors - The obvious solution is batteries but lightweight lithium batteries are extremely expensive and are only good for a limited number of re-charges.
  • Autonomous navigation - the nav system needs to be accurate to at least +-25mm to get accurate positioning on the crop beds. Think 'error correction'!
  • Object recognition - The machine needs at least some basic OR. The weeding process is preventative so there's no need to distinguish weeds from crop. It's more about telling the difference between brown soil and green plants so the cameras are more likely to see green blobs on brown background. Objects can also be placed on the soil to aid navigation, enhancing the accuracy. But what about bright glaring sunshine?
  • Cost - The machine needs to be built within a sensible budget so that in stands a chance of being commercially viable. The mechanical design needs to be as simple as possible with appropriate compromises with functionality. How close to the crop can the drive gearboxes be? How big is the crop going to be? Most weeding needs to be done when the crop is more vulnerable at the early stages. How 'ideal' does the steering need to be? The steering bearing does not necessarily have to be in the middle of the wheel - it can be offset to one side and changing the relative speeds of the drive wheels can aid the steering motors.
  • Multi-purposing - How to design the machine in such a way as to allow different implements to be changed over from one another in less than 5 minutes? For example, the weeding apparatus should be a bolt on assembly rather than bolted on individual components.
  • Collision avoidance - Many new cars on the road (2018) have collision avoidance modules which prevent people being run over and the car hitting other obstacles. Can such systems be easily created or bought cheaply?

Danish Weeding machine 01.pdf

Mobile Robot for Weeding Tommy Ertbølle Madsen & Hans Lavdal Jakobsen Master Thesis Project January 31st 2001 Department of Control and Engineering design Technical University of Denmark

Adobe Portable Document Format - 7.25 MB - 06/12/2018 at 09:33

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All Claw Mechanism Drawings.zip

Claw mechanism DWG files for laser cutting

x-zip-compressed - 177.48 kB - 04/25/2018 at 10:32

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weedinator 18 v2.zip

This is the CAD design from which dimensions of the steelwork etc. can be obtained. The file is saved in 5 different types, but it's highly recommended to open Weedinator 18 v2.F3D in Autodesk Fusion 360.

x-zip-compressed - 35.59 MB - 04/22/2018 at 10:19

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Weedinator Main Controller INO files 01.zip

These files include the programming of the TC275, the MEGA 2560 and the NANO and will be updated periodically.

x-zip-compressed - 15.65 kB - 04/22/2018 at 10:18

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Current sensor 01.pcb

Opens with 'Design Spark' software.

pcb - 142.50 kB - 04/22/2018 at 09:25

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View all 10 files

View all 16 components

  • Cable Management

    TegwynTwmffat☠3 days ago 0 comments

    I've always found the chunky cable drag chains on CNC machines rather sexy so getting the cables to move properly was a major priority, right from the initial design concept. 

    Unlike all other CNC machines to date, the 'Y' axis motor for the WEEDINATOR runs inside the chassis of the machine rather than on top, which results in a massive reduction in overall height of the machine. How the cables within the chassis would behave was indeed a major concern. Would the drag chains have enough room to swivel around within the narrow confines of the chassis? In the end, I need not have worried as the cable management performs perfectly.

    The photo below shows the CNC in maximum 'Y' axis travel with the drag chain curled up nicely on the far right.

  • WEEDINATOR Hit the Road

    TegwynTwmffat☠3 days ago 0 comments

    In the true spirit of open source, the WEEDINATOR is going to be exhibited at various exhibitions / hack fests around the UK, including Liverpool Makefest on 30th June 2018.

    I spent a couple of days making a special trailer for transportation. I'm not sure exactly what the machine weighs, but it's definitely under the 750 kg weight limit for braked trailers in the UK.

    It will be interesting trying to get it into Liverpool central library, but we'll take an angle grinder and sledge hammer just in case!

  • WEEDINATOR navigating using Pixy2 line tracking camera

    TegwynTwmffat☠06/10/2018 at 13:50 0 comments


    The WEEDINATOR uses advanced, super accurate GPS to navigate along farm tracks to the start of the beds of vegetables with an accuracy of about plus/minus 20 mm. Once on the bed, accuracy needs to be even greater - at least plus/minus 5 mm. 

    Here, we can use object recognition cameras such as the Pixy2 which can perform 'on chip' line recognition without taxing our lowly Arduinos etc.

    This test was done in ideal, cloudy conditions and eventually the lighting would need to be 100% controlled by extending the glass fibre body of the machine over the camera's field of view and using LEDs to illuminate the rope. Other improvements include changing the rope colour to white and moving the camera slightly closer to the rope.

  • More Test Beds Planted

    TegwynTwmffat☠05/23/2018 at 12:33 0 comments

    As the season continues, the ground dries out a bit more and it's possible to get a much finer tilthe in the soil, which provides a different environment in which to test the machine.

    Blue ropes are laid down for the machine to use as an even more accurate guide than GPS. Cameras can pick up on the rope and translate it into x, y coordinates which can then guide the machine's steering.

  • WEEDINATOR Team Test the Machine

    TegwynTwmffat☠05/22/2018 at 08:45 0 comments

    Team members put the weeding claw into action.

  • Project Milestone Reached: Seamless Satelite Navigation

    TegwynTwmffat☠05/20/2018 at 08:01 0 comments

    Since the project was first started, it's taken one whole year to get to this stage: satellite navigation through a series of waypoints, accurate enough to stick to a conventional farm track (plus or minus 25mm).

    I never thought we would get to this stage so quickly and the CNC mechanism was never meant to be built this year either ….. But it's done! Also, we've started exploring advanced object recognition (deep learning, Ai, neural networks etc) with the Nvidia Jetson TX2. Please join the project if you have relevant skills!

  • Improved Navigation Code Tested on Machine

    TegwynTwmffat☠05/11/2018 at 10:35 0 comments

  • Making Doughnuts in the Field

    TegwynTwmffat☠05/10/2018 at 16:57 0 comments

    WEEDINATOR now runs really well when going up hill or on the flat:

    But struggles to go downhill! Maybe needs some mechanical braking or something?

  • Torque control now in place!

    TegwynTwmffat☠05/09/2018 at 16:04 0 comments

    When the machine was driving over rough ground the wheels would lose synch with each other and get positional errors showing on the motor drive displays. A current sensor PCB was built to override positional control when necessary by effectively monitoring the torque instead:

    The machine was made to drive over a ramp under one of the wheels to simulate uneven ground and the MCU code was tweaked to get the torque balanced throughout the operation.

  • First Weeding Test

    TegwynTwmffat☠05/05/2018 at 14:08 0 comments

    The components for the weeding claw mechanism have arrived!

    ..... And the removable sub assembly welded together:

    This is bolted onto the Z axis travel plate, the motor tuned in Leadshine Protuner and the machine is ready for the first test, literally, in a field:

View all 24 project logs

  • 1
    Chassis Build

    The central part of the chassis, which is also going to be the CNC machine, is laid out on an extremely flat surface plate so that the pieces of box section can be positioned as accurately as possible, enabling the CNC components to run nice and smoothly. The pieces are welded up on the table taking great care not to get hot splatter on the table itself, which would ruin it.

    The box section itself needs to be cut with an accuracy of about 0.2 mm and I chose the best steel supplier in my location with a saw that used automated feed to get an accuracy to 0.1 mm. Other steel suppliers cut to +- 5mm which is useless!

    The sections are checked for squareness to each other and carefully tacked together in diagonal sequences to avoid distortion.

    At this stage the construction seems to be wildly heavy and very much over engineered, but in the later stages the plasma cutter is going to be used to remove as much mass from the structure as possible.

  • 2
    Buidling the Swivelling Front Axle

    The front drive units are positioned relative to the main chassis and wooden blocks are used to level it up. This enables the front axle to be measured. It is then drilled each side with a diameter 60mm hole in it's centre using a broaching drill. The 600 mm long box is drilled diameter 40mm.

    The small 100 x 100 box sub frame is welded onto the main chassis, getting it as level and square as possible and the suspension tube is inserted and welded into the 60 mm holes.

    The low profile 50 mm bearings are inserted into the tube and the shaft is carefully positioned and welded in.

    The 970mm axle box section is then welded to each of the drive units in turn.

  • 3
    Building the Back Axle Assembly

    The back axle is a temporary fixture to enable testing of the main front drive units. The dimensions of the 100 x 100 mm box sections used are given by setting the rest of the chassis level and making measurements.

View all 9 instructions

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Discussions

elad orbach wrote 06/03/2018 at 09:39 point

looks very similar to this project  (2001)

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.431.3255&rep=rep1&type=pdf

hope it can assist you to achieve your goal faster

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TegwynTwmffat☠ wrote 06/04/2018 at 16:29 point

Looks like a good system .I'd certainly love to have in-wheel motors one day!

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TegwynTwmffat☠ wrote 06/04/2018 at 16:35 point

yes and I'd love to be able to use in wheel motors sometime soon!

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miltongiordano wrote 04/25/2018 at 12:20 point

love your project, following closely

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TegwynTwmffat☠ wrote 04/25/2018 at 13:59 point

Thanks - We're making a lot of good progress at the moment.

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miltongiordano wrote 05/09/2018 at 11:55 point

anything to share? about your progress

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TegwynTwmffat☠ wrote 05/09/2018 at 16:21 point

Yes ..... I've just updated the logs section with videos etc.

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RandyKC wrote 04/17/2018 at 16:26 point

Enjoying your project! 

Where did you get your tire(tyre)/wheel/hub/axel from?

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berryfarm wrote 03/04/2018 at 18:34 point

Can your motor controller be used on other motors besides stepper motors?

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TegwynTwmffat☠ wrote 03/05/2018 at 07:03 point


 Yes, we are using the controller on other motors including servo and cargo

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