Tuning!

 Tuning!

So we build solutions, they should work, and then the real world gets in the way. 

Lava Palaver progress

We'd gone for a camera sensor for the Lava Palaver challenge, not because it was a better option for following a line, but because it was automatically immune to the hump in the course. However, this threw up new issues. The competition course is 7m long and painted black, the only surface available for testing is a light wooden floor which makes for very poor contrast.

 Early testing was plagued with phantom readings from reflections which confused the robot, so testing moved to using a black line instead, with the intention of switching over to white for the competition day. This was much more successful, but space is a limit again. To make a test worthwhile, we're going to have to go for a bigger course outside, using a long roll of black art paper with white electrical tape down the middle and hope for dull days!

Illumination was oddly a very important feature. Off the shelf line follower attachments tend to be IR sensor based and have built in illumination which tends not to be noticed, but for the camera, even illumination is essential to get good contrast for the line, so the robots headlights have to be used to light up the track ahead, together with an overhead light illuminating from above. 

The result is a fairly simple bit of code at the end, but beneath it is a lot background code doing the heavy lifting and interfacing. 

One of the items outdoor testing might help with is coping with bright sunlight and shadow. Watching the competition from previous years, it's obvious that this can have a detrimental impact on robots using optical sensors so we'll be looking at that. It's hasn't been done yet but we'll be experimenting with a sunshade for the robot to give more even lighting for the camera and hopefully reduce errors.

Zombie Shooting

For the Zombie Apocalypse, we've had an idea to use a butchered standard nerf gun which looked very promising out in bits on a table, see an earlier blog post, but we discovered a weakness. Using the servo method of pushing the nerf pellet into the gun worked a lot of the time, but then would jam the gun requiring it to be dismantled to clear the jam, it wasn't suitable for the competition. This held us up for quite a while but an obtuse solution using a stepper motor and a rotating cam came to the rescue, so now we're back in business.

The video shows the cam operating and firing off a magazine of pellets. We then got a cat laser toy and pressed it into service to help with aiming, now how many competitors will be aiming at butterflies?

As the video shows, the gun fires to the left, a bit more work to do but on our way.:) 

Minesweeper

Again, this is one we had a solution to some time ago, but when we come to use it, there's a surprise for us. We're using an overhead camera, but processing the image in memory leaves off a lot of the arena, a 'feature' of the camera.

 The image was always going to be distorted but missing bits is a problem we haven't time to overcome, we'll just have to code round it. This means that the robot will have to search for the red square sometimes instead of just being able to see it and move to it. 

The algorithm for this will be basic, something like the following.

Just how accurate the movement will be isn't known, we were expecting to just move to the red square wherever it was, but this now requires some idea of where the centre of the arena is. Only testing will tell. We're doing this challenge on mecanum wheels. As the arena is 4 x 4 matrix, all red squares will be within it and so a map can be built of the arena based on squares that have already been red. Will this be good enough for the minimum 20 moves required we'll have to see. Anyway, signing off with an errant robot which finds it's square, and then ignores it, ho hum.