Thursday 23 January 2020

PiWars 2020: Making the cut

Before I can best plan out how to convert the Thunderbird 2 toy into a successful PiWars competing robot I need to open it up and see what I'm working with. Happily the toy opens up quite nicely, just a case of removing every screw you can see on the underside of the chassis and popping the two halves apart. Most of the internal items also unscrew easily with the notable exception of the tail. Whilst it looks to just be held in place by 2 screws either side, it appears that the manufacturer also glued it into place for extra strength, and by the time I realised this I'd snapped off one of the supports...

Opening up the chassis
The pod themselves open up nicely too, just remove a couple of screws and pop it apart. Remove a few more screws and the launching mechanism for Thunderbird 4 comes out as well.
And opening up a Pod.

In terms of usable space the main two areas of interest are the inside of the cockpit and pod. These can both house a full size Raspberry Pi, barely in the case of the cockpit, and with room to spare in the pod. As my plans are to swap out the pods for different challenges this means the controlling Raspberry Pi must be housed in the cockpit (to comply with the rules of PiWars), leaving the Pod to house the motors and any additional hardware required to complete the challenges.
Tight squeeze on the left, roomy on the right.
With the toy opened up what's the next step? Well, those who read through my PiWars application details in the last posting may have spotted the line at the end stating that the Thunderbird 2 model is too long and needs cutting down to size...
So the length limit is 300mm...
Last year, in PiWars 2019, I made an effort to keep Wall-E looking like the original toy, which turned out to be a challenging task, but at the end I was happy with my decision (Apart from maybe the gear box failures!). With Thunderbird 2 that just isn't going to be an option, so with the cockpit ear marked for holding a Raspberry Pi then its the tail that will have to be chopped off. I had hoped to keep the battery compartment, which is towards the rear, but the vast majority of that also fell outside the 300mm length limit.

Big and cutty
But how to remove it? As I have recently started attending a MakerLab, I've gained access to a variety of big cutting tools  and I decided to give one of those a go. After all a mains powered, table mounted bandsaw thingie should have no trouble cutting through toy grade plastic...
Well technically it had little trouble cutting through Thunderbird 2, however it generated so much heat that the plastic melted back together again afterwards! Requiring a bit of wiggling and hacking at until the tail could be broken away, plus a bunch of post processing to tidy up the cut.
Transitioning from scruffy to nice and smooth.
The tail section has quite a lot of weight to it, so now its been removed Thunderbird 2 gets a little front heavy, and will get even more so when the battery and Raspberry Pi are installed. So the plan is to install counter weights to balance things out. Where I can I hope to reconnect the tail section as an 'attachment' for some of the challenges, and Mike has helpfully confirmed its okay for the attachment section to be on the back. Hopefully a few magnets will be strong enough to hold it in place, whilst also allowing for easy removal. However this isn't strictly necessary and will be in the 'nice to have' list of features.
Thunderbird 2 - Compact edition
With the chassis cut down to size the next step will be installing the brains!


Tuesday 14 January 2020

PiWars 2020 : Calling International Rescue!

Wall-E from PiWars 2019
Its a New Year and a new PiWars. PiWars 2020 is coming in March and once again I've managed to get selected as a competitor! After the success of last years' Space themed event (My entry being the lovable robot Wall-E) Mike and Tim decided to repeat it for 2020, this time going for a 'disaster' theme, either natural or man-made, with a leaning towards disaster related movies.

I can come up with a lot of ideas for disaster themed robots, one with a volcano on it, or a bursting dam (pumping water back behind the dam so it can burst again), or just an alien robot come down to Earth to destroy and invade.

All fun projects, but there was a toy conversion I've had on the back burner for a while and this seemed an appropriate time to use it. After checking that 'rescue' themed robots were included in the 'disaster' category I submitted my application for Thunderbird 2. After all, where there's a disaster International Rescue won't be far behind!

Thunderbird 2!

As this is the 5th time I've entered PIWars you'd think I'd have a good handle on what to do. However, in reality, I'm still making a lot of this stuff up as I go along. But.... as long as I write down my ideas it becomes 'planning' which is a much more responsible sounding word.

So what sort of ideas did I write down? Mmmm rather a lot!  Here's a copy of my application (Might also be of interest to anyone wondering what to put in a future Pi Wars application)

Robot will be built around the Thunderbird 2 Supersize toy (From 2015).

The main chassis will contain a RPi 3A+ as the main controller, as well as a battery, camera and multiple ToF sensors (One under each air intake on the front, plus one on either side). Other sensors/components may be added as the build progresses..

Actual propulsion will be contained inside the Pod (As this is the only section that touches the ground) and it is planned that the Pod will be swapped out for the various challenges. Initially the RPi 3A+ will be connected physically to the motor driver inside the Pod (e.g. via i2c), but if development goes well this will change to a wireless communication (NFC, bluetooth, WiFi, something else?). Ideally I’d want to get to the point where the Pod can just be swapped out, the RPi 3A+ automatically detects this (via NFC) and the software updates as appropriate.

Current plans for Pods are

Pod 1: This will be the standard Pod that will be used in the majority of challenges. Current plan is that it’ll contain a twin set of tracks, that come through the floor of the pod, which also includes some limited vertical movement. So for the obstacle course the ‘bottom’ of TB2 can be raised by 1 or 2 cms to clear obstacles, ramps etc. It may also contain a line following sensor for the ‘Lava palaver’ challenge, if that doesn’t end up being carried in the main chassis.

Pod 2: This pod will be targeted at the ‘Zombie Apocalypse’ challenge. It will have a much simpler motor mechanism to free up space inside the pod (prob. Just a couple of wheels to allow movement over flat terrain). This extra space will be used to house a rotating turret to fire foam darts at the targets. Expectations are that this will rotate left and right to allow more precise targeting, compared to moving the entire robot, as well as some limited up and down movement to fire up and down. A laser will be installed to improve aiming.

Pod 3: This pod will be targeted at the ‘Eco-Disaster’ challenge. Again this will have a simpler motor mechanism, probably a match for Pod 2, but this time the space will contain a gripper arm that will be deployed out the front of the Pod (The main TB2 chassis will be raised to accommodate this). This will have to be fairly long, as TB2’s nose can’t clear the barrel height, and will be used to grip and capture the barrels. Holding them in place as they are delivered to the target areas. Expectation is to use an IR beam, or physical button, in the gripper to detect when it should close. As well as a second camera that will be used to verify the colour of the barrel (This will be streamed to the RPI 3A+ over WiFi for processing).

If time permits, and it turns out to be practical, a mask will come out the top of the Pod and hold a third camera that points downwards (With a wide lens) to better detect barrels in all directions, instead of having to rotate around until one crosses the LoS of the front mounted camera (Or this may end up coming out of the top of the TB2 cockpit for ease of connecting up)

This camera mask mechanism may also be used for the ’Minesweeper’ challenge, to detect which square is lit up.

Control will be done via a simple UI accessed via VNC or web page from a wrist mounted device (vaguely matching how remote control of TB2 is done in the newer ‘Thunderbirds Are Go’ series). This is liable to be another RPi with a touch screen display.

Note: As the TB2 model is too long, the engines and tail have been cut off to meet the max length in the rules. Outside of the challenges this will prob. Be attached via magnets for appearances sake.

Will I complete all these tasks? Well I've never managed it before! But only time will tell...