KEITH Evolution Introduction
02 Sep 2015PiWars 2015 Blog
Welcome to the first post in our blog following the development of KEITH Evo, our entry for PiWars 2015. We are Harry and Andy Merckel, a son and father team. Harry provides the brains, coding, electronics and geeky stuff required for the project while Andy does the CAD, chassis design, silly ideas and funds! Harry is 16 years old and is just embarking on his A Levels in Maths, Further Maths , Physics and Computer Science, so it is expected that this project will become more complicated as we proceed…
Background
The original KEITH (as seen elsewhere on this website), in his various incarnations, performed better and worse than we wanted or expected. In the first PiWars he exceeded expectations in some challenges and fell down on others. For example, in the obstacle course, which he should have had an easy clean run, one of the drive wheels slipped off its axle leaving us with one-track-drive. By the time we had realised why KEITH could not climb over the blocks we had wasted a load of time and then incurred a penalty for fixing the problem. A clean demo-run afterwards proved the point… However, with an overall third in the over £75 class we were delighted with our performance in the competition. Afterwards, on the drive back up to Leeds, we talked the issues through and decided that the next robot would have to be called ‘KEITH Evolution’.
Initial Thoughts…
We applied for the 2015 competition not sure if we would get an entry and didn’t think too hard about what we could build. On holiday, we talked the whole thing through and weighed up the pros and cons of various configurations. As this robot is an evolution of the original we have decided that we will create a new tracked robot with a wooden chassis and attachments for the various challenges. As with KEITH, there will be a Raspberry Pi at his heart (obviously!), a motor controller of some sort and probably an LED controller. We have decided to enter the A4 class so KEITH Evolution will be significantly larger than KEITH, who fitted on an A5 sheet.
KEITH ran a couple of small, very cheap, 6v dc motors through a Tamiya gearbox and tracks. The motors lacked torque and the tracks stretched as they got older. The arrangement worked well on hard surfaces, but not so well on carpet. Also the motors were very hard to balance as they differed in output, with different differences between forwards and reverse! Our attempts at PID failed so we devised a trial and error empirical system instead. We just about got away with that…
At PiWars we talked to the PiBorg people and were impressed with the motors they used – and the torque they have. KEITH Evo will utilise similar motors to power the tracks.
With KEITH Evo being bigger, we are currently researching tracks. We feel that metal ones will not have enough friction on hard surfaces and will introduce errors in the skid-steer system, so plastic or nylon appears to be the way we are heading.
Once we have sorted tracks and motors the chassis design will begin. As with KEITH, this will be done on AutoCad and built from laser-cut 3mm ply (courtesy of whichever obliging school teacher we can persuade to cut it for us!). Harry is keen to incorporate living hinges in the chassis design.
We used a 7.2v battery with KEITH which worked well as long as it was fully charged between challenges. As the battery drained we experienced some very odd behavioural problems! We will determine battery type once we have the motors sourced.
Sensors will be along similar lines to KEITH’s for proximity and line-following. We will expand on what we did for wheel encoders and look at various other options for location and straight-line management.
KEITH was remotely controlled using a Wiimote. We’d like to try radio control with proportional control of the motors and attachments – we’ll see about that!
We will also devise a few new Heath-Robinson-esque attachments for the various challenges in due course. Expect servos, bent wire and rubber-bands again!
Expect more news as we progress.
~Andy
Why not follow us on Twitter @KEITHtheRobot for the latest updates!
Back to KEITH Evolution Blog Archive