For the last few years, at about this time of year, the same conversation has taken place at PiDrogen HQ:
Dad: “Let’s enter PiWars, entries are open! We could use last year’s robot to keep things simple.”
Eldest son: “Well, we could… But… A tracked robot would be way better than last year’s robot. And last year’s robot isn’t cool enough. We need a new robot. It should have tracks and look cool. Cooler than last year’s anyway. Tracks would be better over obstacles, wouldn’t they?…”
So, this year, eldest son will have it his way. We want a cool looking robot with tracks. Now, since this year’s competition has a farm theme, there can only really be one choice (at the risk of being too obvious!). So, we present our proposed entry for this year’s PiWars competition: PiDrojon Deer (“PJD”).
PJD has been completely designed in Fusion 360 to be 3D printed (apart from the tracks which are Lego parts). The motors employed by P21 have been used (since the encoders will come in handy), but the track mechanism includes a 4:1 reduction. The track sprockets have a built in crown gear which takes the drive from the motor; this will be an experiment in the longevity of 3D printing for a stressed component.
The front loader has a pair of servos to lift it. It will be one of the attachment points for the game specific implements. The slot in the front loader blade is to allow a front facing time-of-flight (ToF) sensor to “see” forwards.
A Raspberry Pi camera is mounted in the front grille, just below the Raspberry Pi symbol (it’s quite hard to make out in the gif). This will be the primary means of navigation, although the robot will also use odometry and an Inertial Measurement Unit (IMU) when the camera is not possible to use. The Pi is mounted in the top of the bonnet, just below the exhaust pipe.
To be honest, I think this design is risky. To do well this year we are going to need a robot that can whizz about the arena autonomously and accurately. I have the feeling that a tracked machine will neither whizz, nor be accurate with its movements. So, the pressure will be on to upgrade the control system! (But in case that doesn’t work, this design has a trick up its sleeve: but that’ll be the subject of another post).