While we're all busy with different things, somehow we get new ideas for PiWars challenges. So we have a new Hungry Cattle hopper design, this time both a measure, and also a funnel to direct the feed to the trough.
Wednesday, December 1, 2021
Always something new
Tuesday, November 23, 2021
When will we five meet again
Lots of things happen when we get together, lots of ideas passed around and a few demonstrations.
First up was the Hungry Cattle hopper and filler. This had been interrupted by a dodgy 3D printer hotend, but soon fixed and construction completed.
The wooden bit is just for demonstration. It was duly loaded with the cheapest rice we could find and tested out. This is a video of a couple of runs, the first in real time, the second in slow motion.
so we all know what we are designing to, and basically its four mounting holes on an 80mm grid on an 90mm plate.
Sunday, November 14, 2021
Not according to plan
It's not plain sailing, just running through an idea from end to end. A story from our chassis maestro who's been lent a StereoPi to test
On trying to set up WiFi on the StereoPi I got an error message: "No wireless LAN interfaces found". So I went on the Internet and found dozens of different 'solutions', and tried several of them without success. Then I had a cup of coffee, and, while drinking it I had a thought. I checked the spec. of the StereoPi and discovered that this version just doesn't HAVE any wireless LAN interfaces. I plugged in an old WiFi dongle, and it worked instantly. Aaaaargh
But how did it do...?
Using openCV on StereoPi V1 (=CM3, +3B+) in stereo with minimal processing
1280x480 9fps
640x240 18fps
384x144 18fps
And the compute module 4 is available from Radio Spares, hang on, for 22/May/2022
In other news the Hungry Cattle challenge test attachment was under construction, the first 3D print produced a hopper.
Thursday, November 11, 2021
Chassis
With four of us involved we're doing bits in parallel, but one blog, so here's some other progress on the chassis. I must take a picture for next time because this is being built as I write.
This is the fundamental chassis, which is in two parts, primarily for the fourth challenge, The Farmyard Tours, where we think a bit of suspension might come in handy. Currently its a big wheel robot, getting it's speed from lower rotation motors that are easier to control, though we may switch to stepper motors in the future, it's not planned yet. We do have to keep in mind the 500mm/s average competition speed.
The next picture is bulking the design out a bit, again subject to change, but taking shape.
The wheels are 3D printed and have now been covered in a rubber solution to give them grip.
Apples
The Nature's Bounty challenge has apples, and what the apples should look like and how we get them off the 'tree' is of interest.
I've posted a picture of the apple picker idea, but it is just an outline.
This bit is about that jaw on the picker and how it might work with different apple shapes.
Some thoughts on apples, spherical or otherwise, The
pictures show two designs of apples for the PiWars 2022 Nature’s Bounty
challenge, one spherical and one made up of intersecting circles, together with
some apple picker ideas. The apples have a maximum diameter of 40mm, the
minimum gap between apple and trunk for the topmost apple is 10mm.
A. This is a spherical apple with plain grippers.
The grippers hold the apple at only one position each forming an axle about
which the apple can rotate. The grippers have to apply sufficient force to
ensure that enough friction is generated at the touch pints to grip the apple.
The apple can be held by any point on the gripper, reducing the need for
accuracy.
B. This is a spherical apple with parallel bar
grippers. The apple is held at four points and cannot rotate. The force
required to hold the apple is much less than A as there is some support for the
apple provided by the lower gripper arm, but significant accuracy is required
to position the gripper. The gripper requires less space to operate than plain
grippers.
C. This is a spherical apple with a finger gripper.
The apple is held at 8 points and cannot rotate. The force required to hold the
apple is much less than A as there is some support for the apple provided by
the lower gripper arms. The apple can be gripped at multiple points reducing
the need for accuracy.
D. This is a spherical apple with a modified
gripper. The apple is held over a continuous area and cannot rotate.
Significant accuracy is required to position this gripper and the size of the
gripper may be too large to be able to grip the top apple on the tree due to
the gap between apple and tree trunk.
E. This is an apple made of intersecting circles
with plain grippers. The grippers hold the apple at only one position each
forming an axle about which the apple can rotate. The grippers have to apply
sufficient force to ensure that enough friction is generated at the touch points
to grip the apple. The apple can be held by any point on the gripper, reducing
the need for accuracy. The apple is lighter than the spherical apple so the
gripper requires less force.
F. This is an apple made up of intersecting circles and parallel bar gripper. The apple is held at four points and cannot rotate. The force required to hold the apple is much less as there is some support for the apple provided by the lower gripper arm, but significant accuracy is required to position the gripper. The gripper requires less space to operate than plain grippers.
G. This is an apple made up of intersecting circles and finger gripper. The apple is held at 8 points and cannot rotate. The force required to hold the apple is much less as there is some support for the apple provided by the lower gripper arms, but significant accuracy is not required to position the grippe, as with F.
H. This is an apple made up of intersecting circles and a plain gripper. The gripper can apply a force over a wide area, provided it is positioned with a small amount of accuracy, and while the apple can rotate, this may be limited by the position of the gripper. There is some increase in torque on the gripper due to holding the apple away from the centre of gravity.
I. This is an apple made up of intersecting circles with plain grippers, but the apple is rotated 45 degrees. The apple is held at 4 points and cannot rotate. The apple can be held at any point on the gripper vertically, but the gripper must extend beyond the far edge of the apple.
J. This is an apple made up of intersecting circles and a parallel bar gripper, the apple is rotated 45 degrees. The apple is held at 8 points and cannot rotate. Significant accuracy is required to ensure that the gripper locates both vertically and horizontally. The gripper requires less space to operate than plain grippers.
K. This is an apple made up of intersecting circles and a finger gripper, the apple is rotated 45 degrees. The apple is held at 16 points and cannot rotate. Significant accuracy is not required as with J.
L. This is an apple made up of intersecting circles and a modified gripper, the apple is rotated 45 degrees. The apple is held over a continuous area and cannot rotate. There is a degree of self-alignment in the gripper but does require some basic accuracy. The gripper may be too large to be used with the topmost apple, as with gripper C.
Hoppers
More thinking, will have to start doing soon!
A bit of design thought on the Hungry Cattle challenge. We needed at hopper to supply feed so the following has been sketched up. It's basically a box, the hopper, with a funnel and valve mechanism underneath, opened with a simple servo movement.
That isn't the real chassis, just something to get an idea of how it will fit together. As a first design its not to bad but needs a lot more in the way of components. The hopper separating from the mechanism, so we can just make three and reuse them between designs. The valve and hopper mechanism will likely be remade several times, as they have to accommodate the servo and the attachments between the two. The valve also has to be reasonably tight fitting and still move. Next update on this will be pictures of a real one, maybe even a working video!
Sunday, November 7, 2021
A first get together
Lots of small activities done to clarify what we need and how we might move forward and eventually we all met up at a local Raspberry Jam in Exeter library which was a bit naughty as we sort of dominated it with PiWars. Separate meeting arranged for two weeks later to talk robots and nothing else.
What have we done this week?
Collected cardboard for mock-ups.
We still need large cardboard sheets to make an arena, but that will be remade several times so a steady source needed, though we have an Ikea table wrapping in store.
A first mock-up of a tree.
This is a cardboard version as per the instructions, but we suspect we will make a more substantial version out of acrylic sheet when we are further down the line. These things have to be made so we have an idea of the actual challenges in front of us, not just a theoretical of paper based exercise.
Navigation is key and being in the Advanced category, it should be good. One idea is to create reference points in the arena which an imaging system can recognise and create positioning information based on that. The following are a sequence of pictures of a basic version, coloured lights hard wired to display a pattern in the arena wall.
Well it looks good, but needs lots of coding to use, and permission from the organisers!
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