The unnamed (yet) quatruped spider project

[tinhead]

Hello all,

Been a few years since I actually built a robot and since I have never really tried to build anything with legs here we go.

Here is the plan so far:

- 12 DOF using MG90S microservos
- rpi zero w as brainz
- PCA9685 16 channel pwm driver for the many servos
- custom built battery pack out of two 3.6v li-ion cells with BMS
- an ubec to provide the 5v
- sensors TBD

I have all the parts in stock for a while now which is cool

Software wise (still in planning):
- the pi will run a custom build linux image
- the control software will be spawned from an earlier project I've been playing with written in golang using a framework called gobot.io
- more TBD

Currently I'm designing the chassis in FreeCAD, and I think I have a base to work with.

bot_base.png (25.25 kB . 859x751 - viewed 108 times)
Of course this is all going to be 3d printed as usual

I'm going to create a github project and add all goodies in there once progress is made.

Enough for now I'll update once I have something to show.

27-11-2019 - First twitch

Ok so it's been a while time for some updates.

Software

Custom linux - check !

I have managed to create a docker based buildroot system that eventually spits out a sdcard image with all the following goodies:

- by default the image boots configured as a WiFi AP mode so you can easily connect to it.
- you can set it up to connect to your own network by adding a file with network name and password in the boot vfat partitions (details in the readme in the repos I'll amb dd below)
- current filesystem size is about 250 MB
- it's fairly fast to boot I think under a minute
- it will automatically grow the root filesystem to use all the space available on the sd card
- it uses systemd as the init system so you get all the nice stuff
- it has the docker daemon built in in case you want to run docker images  - to be figured out if it really helps on a single core system but it might do very well when I manage to build for the raspberry pi 3
- ssh daemon so you can ssh inside
- all the raspberry pi drivers are available however some tweaks are needed in the configuration of the raspberry bootloader to enable them

Now I'm sure I'll be forgetting stuff from the list but there you go.
The build system is hosted here: https://github.com/TinHead/rpi-sd-builder
The actual sd card image is generated here: https://github.com/TinHead/rpi-zero-w-generic-docker-sd-card and you can download the latest build here: https://github.com/TinHead/rpi-zero-w-generic-docker-sd-card/releases

So far I only got to write a small test program in golang to check all works so no detail on control software for now.

Hardware

Ok so currently I have the electronics connected, 4 motors (well 5 ish) on. Wiring is a mess but hey it's only the beginning

Pics:

Base and stuff:

DSC_0031.JPG (71.37 kB . 1024x576 - viewed 48 times)

Current state:

DSC_0180.JPG (78.75 kB . 1024x576 - viewed 48 times)

DSC_0181.JPG (79.53 kB . 1024x576 - viewed 49 times)

And it does move

Till the next one ...

Cheers!
TH

[Nemesis]

Sounds nice ! I'm looking forward to see this project going
If I may, I have a pretty good knowledge about walking robot, tell me if I can be of any help Regarding your chassis, I would put more fillets in the corners, because this is plastic, you have to take care about weak points, especially in corners...

[tinhead]

Hi,

It does not even try to compare to your Animabot that's a work of art
It's just a toy I'm working on and off and it's far from being even close to functional.

Regards,
TH

[Nemesis]

Starting to take shape ! nice job it took me soooo much time to get at your point the first time... reminds me a lot of things 
Now, make a 2nd chassis with PCB and battery holder to make it neat and some cable management and you will have a very nice base to work on !

Good job !
After you can do this: https://www.youtube.com/watch?v=jWP3RnYa_tw
and this: https://www.youtube.com/watch?v=ss4c_nFdbDw

[Bajdi]

Nice to see somebody is still building robots 
I just had a look at gobot.io, looks interesting. Maybe I should try it out on of my old dusty robots.

[tinhead]

Now, make a 2nd chassis with PCB and battery holder to make it neat and some cable management and you will have a very nice base to work on !

Ya that's on the list for next revision. I actually did some mounts for the electronics already but I have realized they would not work out in the end adding way too much height so I need to revise both those and the holder for the battery. Another fight for another time.

Right now I'm trying to have all 12 servos mounted so I can figure out if this setup works out or not. If it does work I can refine the base later on and start figuring out how to implement things on the software side... Lots of work I guess


Thanks for the input!
TH

[Nemesis]

It is a good thing to go step by step and try various versions of components (chassis, holder, legs, etc..).
One thing I noticed, try to keep the coxa length as small as possible in order to keep the servo's torque and minimize the leg flexion

[maelh]

Nice build! Looking forward to when it's fully built and you can make it walk.

Maybe a genetic algorithm or some neural net could be used to teach it?