Tensor

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cambesol
Posts: 5
Joined: Mon Jan 02, 2017 7:02 pm

Tensor

Postby cambesol » Mon Jan 02, 2017 7:24 pm

Hi Forum,

Work in progress. Four wheel drive, very distributed control, using ROS Indigo and several embedded Linux boards.

Thanks,

Neil.
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RobotsforRoboticists
Posts: 9
Joined: Fri Jul 08, 2016 6:55 pm

Re: Tensor

Postby RobotsforRoboticists » Wed Jan 04, 2017 12:38 am

Cool.

Is this for a particular application, or just for fun/learning?

What controllers and linux boards are you using?

cambesol
Posts: 5
Joined: Mon Jan 02, 2017 7:02 pm

Re: Tensor

Postby cambesol » Wed Jan 04, 2017 1:21 pm

Hi,

I'm building this for several reasons, to list a few:

- Technology demonstrator for my company.
- Attempt to tear my kids away from games/tables/PS4's etc.
- Investigate a novel form of odometry.

I designed and fabricated most of the parts using a home-built CNC router. Other parts are either COTS,
or made in my workshop using a lathe or machined using my mill. Electronics is COTS as far as possible
to save time and overall cost.

The stepper drivers are based on an ST Micro part (6482H). I've found this to be excellent. I use Raspberry Pi Bs for the control of each pair of wheels. They also interface to range measuring (both sonar and IR), a pair of LEM current transducers to determine consumption of each wheel and a servo driver for positioning the range measurement devices. Ethernet is used for the communications backbone.

I will add a picture of one of the driver controllers.

cambesol
Posts: 5
Joined: Mon Jan 02, 2017 7:02 pm

Re: Tensor

Postby cambesol » Wed Jan 04, 2017 1:23 pm

A controller.
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RobotsforRoboticists
Posts: 9
Joined: Fri Jul 08, 2016 6:55 pm

Re: Tensor

Postby RobotsforRoboticists » Wed Jan 04, 2017 2:33 pm

I noticed the machined parts.

cambesol wrote: - Investigate a novel form of odometry.
.


What are you trying for odometry?

cambesol
Posts: 5
Joined: Mon Jan 02, 2017 7:02 pm

Re: Tensor

Postby cambesol » Wed Jan 04, 2017 6:10 pm

I want to use the same principle as an optical mouse, but using a low resolution camera mounted centrally in the chassis facing downwards. I intend to use OpenCV to generate vector data between concurrent frames. I am sure this has been done before, just not by me ;-)

cambesol
Posts: 5
Joined: Mon Jan 02, 2017 7:02 pm

Re: Tensor

Postby cambesol » Wed Jan 04, 2017 6:33 pm

Writing the driver software. Left pane on the left monitor: SSH shell on the RasPi, right pane on the left monitor: build shell for cross compilation. Left pane, right monitor: the driver source, and right pane, right monitor: the data sheet. Typical embedded development environment! A single SPI bus is daisy chained to control both axes. Driver runs in user space and can provide many useful features (programmable accel/decel rates, absolute steps taken, micro stepping, MOSFET gate configuration, etc.). Really pleased with the stepper driver part, although the documentation is lacking in places. Did I mention that it makes wonderful noises, particularly when driving the two motors in quadrature with a sinusoid profile.
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RobotsforRoboticists
Posts: 9
Joined: Fri Jul 08, 2016 6:55 pm

Re: Tensor

Postby RobotsforRoboticists » Fri Jan 06, 2017 2:02 am

cambesol wrote:I want to use the same principle as an optical mouse, but using a low resolution camera mounted centrally in the chassis facing downwards. I intend to use OpenCV to generate vector data between concurrent frames. I am sure this has been done before, just not by me ;-)


There are a bunch of papers on doing visual odometry (via optical flow). I should write a post about that...

A few things to watch out for are:
1. Lighting (levels, uniformity, etc..)
2. Angle of lighting
3. Camera frame rate vs your operating speed
4. Surface that you are operating on


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