Author Topic: Information required: 3D mapping of surroundings, and motor power?  (Read 904 times)

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Offline FejwinTopic starter

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Hi guys!
It's not like I want to build a robot yet - I try to collect information first.
Now I have two questions:

1) Is there any sensor which could be efficiently be used to map the 3D surroumdings from some point in space to some distance? If yes, what are the distances, speed and accuracy? (Assume a PC is used to process and save the info)

2) How can I astimate the power of a motor or servo from the datasheet in human-understandable dimensions? I mean - to which velocity a motor can speed up a X kg robot at Y Voltage input, or such.

Thank you in advance for any answers!

Cheers,
Fejwin

Offline rbtying

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Re: Information required: 3D mapping of surroundings, and motor power?
« Reply #1 on: January 21, 2011, 08:50:12 AM »
1) Laser distance scanner mounted on a tilting servo, or stereo vision

2) You can't.  At least, not with enough accuracy to make it useful.  Since a slight change in temperature or humidity could significantly change the graph, it's not a reliable open-loop system.  This would be why we like to use a closed-loop system, instead of an open-loop system.

Offline FejwinTopic starter

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Re: Information required: 3D mapping of surroundings, and motor power?
« Reply #2 on: January 21, 2011, 11:23:10 AM »
Thank you very much for your answer rbtying!!

to 1)
It's amazing that such things exist!
Could you give me some link where I could read about these possibilities in detail?
I tried to search google, but I don't seam to find robot-specific results.

to 2)
Ok. So it actually always "depands"...

Offline rbtying

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Re: Information required: 3D mapping of surroundings, and motor power?
« Reply #3 on: January 21, 2011, 03:37:03 PM »
There's a lot of research on it, but this seems to be a working possibility: http://www.ros.org/wiki/laser_pipeline

Offline FejwinTopic starter

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Re: Information required: 3D mapping of surroundings, and motor power?
« Reply #4 on: January 21, 2011, 05:49:37 PM »
Thank you again, rbtying!!

As I see it, these scanning lasers are way too expensive for a hobby robot creator. So have to stick with stereo vision.

Do you perhaps know which cameras are suited best for robot-stereo-vision (processing data on linux)?
I have seen some robot "eyes" some day, a double camera like a binocular (some like wall-E has). Is that thing best? Cant find any clue about it now... How is it called?

Offline AtomHex

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Re: Information required: 3D mapping of surroundings, and motor power?
« Reply #5 on: January 21, 2011, 06:13:21 PM »
You could map out an area using sonic sensors, either scanning or multiple, they are relatively cheap and lots of variations to choose from.


Offline hopslink

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Re: Information required: 3D mapping of surroundings, and motor power?
« Reply #6 on: January 21, 2011, 06:16:25 PM »
Have a look at the Microsoft Kinect hacks. Kinect uses stereo cameras and directly outputs depth of field (distance) data. This will save you a load of work. Open source software libraries for Kinect are available.

Cheapest laser scanner available is the Neato Robotics XV-11 lidar (currently only available with an XV-11 robot vacuum  - $400, but hopefully soon released as a standalone unit). This has also been hacked recently and google will find you all the information you want.

HTH

Offline Soeren

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Re: Information required: 3D mapping of surroundings, and motor power?
« Reply #7 on: January 22, 2011, 01:05:31 AM »
Hi,

Quote
2) How can I astimate the power of a motor or servo from the datasheet in human-understandable dimensions? I mean - to which velocity a motor can speed up a X kg robot at Y Voltage input, or such.

2) You can't.  At least, not with enough accuracy to make it useful.  Since a slight change in temperature or humidity could significantly change the graph, it's not a reliable open-loop system.  This would be why we like to use a closed-loop system, instead of an open-loop system.

What on earth does open- contra closed loop, temperature and humidity have to do with that??
Wheel size and system friction, or rather not knowing those, does make it a bit of a challenge though.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline nickc

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Re: Information required: 3D mapping of surroundings, and motor power?
« Reply #8 on: January 24, 2011, 06:18:00 PM »
for an motor estimate look at the 'calculators' section on this website.  There's a motor calculator that will give an idea of what size motors you need for a given speed,acceleration,weight and incline.
If you think laser scanners are too expensive wait till you cost stereo vision.
Many hobby robots use Sharp analog IR detectors and/or sonar to map their surroundings or at least avoid obstacles. 

Offline FejwinTopic starter

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Re: Information required: 3D mapping of surroundings, and motor power?
« Reply #9 on: February 03, 2011, 02:49:26 PM »
Thank you very much, everyone! Now I have a rough picture of these two matters.
I will stick to selfcompiled stereovision (openCV on c++ should be easy enough)

As you might have concluded from the above statement, I plan on using a laptop as robo-brain (or something other that runs c++). Now, apart from the brain, a robot needs some wheels, a head, and at least one arm (if he is lucky). To connect PC decisions with wheels I obviously need a microcontroller - now a specific question:
I have these two PIC18F2550 microchips lying around from some previous usb project (yes, these PIC18F are USB able) - will I be able to use them as the connectionknot between USB and wheels? Has anyone some experience to share?

 


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