go_away

Author Topic: Looking for the right sensor  (Read 463 times)

0 Members and 1 Guest are viewing this topic.

Offline HongKongCVTopic starter

  • Beginner
  • *
  • Posts: 2
  • Helpful? 0
Looking for the right sensor
« on: May 17, 2012, 11:21:28 AM »
Was playing with my cat and a laser pointer the other day, and thought that would be a fun thing to do with a robot.  I've got the laser pointer... heck, you can buy them almost anywhere.  What I need is the correct sensor to mount on the robot to let it detect the laser dot on whatever surface it happens to be.  What sensor can I use to detect a laser dot on a remote surface?  And though the dot could be close by, let's open it up a little and allow for distance detection, too.

Any suggestions?

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Looking for the right sensor
« Reply #1 on: May 17, 2012, 09:48:41 PM »
Hi,

Was playing with my cat and a laser pointer the other day, and thought that would be a fun thing to do with a robot.  I've got the laser pointer... heck, you can buy them almost anywhere.  What I need is the correct sensor to mount on the robot to let it detect the laser dot on whatever surface it happens to be.  What sensor can I use to detect a laser dot on a remote surface?  And though the dot could be close by, let's open it up a little and allow for distance detection, too.

Any suggestions?
A camera and some extremely clever software will be your best bet (at a total price range of at least around 1000 x the price of a LASER pointer) - and no matter what, it won't work on "whatever surface"... Just imagine a red LASER shining on a red and a green surface respectively. On a red surface it will be bright, on a green surface it will be very dim or completely "black" (try swiping your pointer over a bookshelf to get an idea of the effect).

Better keep that cat handy for when you need to be entertained, neither sensors nor processors are a match (even) for a cat (and I consider cats quite stupid, no offense meant) and won't be for any foreseeable time ;D

Robots can (so far) only be programmed to a certain degree of pseudo-autonomy (lucky us) - living creature OTOH are fairly autonomous by default (a gross simplification IK), but it can be "programmed" (conditioned) out of them to a very high degree (unlucky us, perhaps :-\).
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 HongKongCVTopic starter

  • Beginner
  • *
  • Posts: 2
  • Helpful? 0
Re: Looking for the right sensor
« Reply #2 on: May 18, 2012, 08:26:25 AM »
I know the robot won't be as versatile or smart as a cat, it was just an idea to have a little fun with.  I can try to do visual processing to identify the laser dot in the picture and then navigate towards it, but image processing is usually processor intensive.  Isn't there a sensor that can detect the laser dot?

Offline mstacho

  • Supreme Robot
  • *****
  • Posts: 360
  • Helpful? 10
Re: Looking for the right sensor
« Reply #3 on: May 18, 2012, 12:42:33 PM »
as far as I know there is no pre-made thing you can buy that does "detect a red dot".  HOWEVER, a really simple solution does present itself (although it will admittedly cost a bit of money):

Buy a microsoft Kinect, a small netbook, and buy or build a mobile robot that can be controlled over USB (Uh...COMPUTER -> ARDUINO -> ROBOT).

Using Robot Operating System and Ubuntu, and a nicely lit, white floor (it IS hard to segment images :-P) you get an image stream from the Kinect and a point cloud.  the image is used to find which point in the point cloud corresponds to the red dot, compared to where you are.  then just move to that point.

it's not really MUCH harder than making a mobile robot, since most of the algorithms to, say, segment out the red dot are simple enough as long as your scene is otherwise uncluttered (from your description, I get the sense that you want it to work in a simple manner first, then maybe build in some complexity).  ROS has some great tutorials on how to do something almost identical.

For what it's worth, I'm doing something ALMOST the same with this exact setup: I have a Kinect that detects a blue object, uses the point cloud data to find where it is in the world, then tells a robot arm where to move.  Our robot arm is a bit more expensive than a simple mobile robot, but the principles are the same and it didn't take me more than a few weeks to get the system going.

Of course...it's really hard if you're new to this  ;D  AND, Like Soeren said, you won't get anywhere near the responsiveness of a cat.  But it's a great hobby platform to play around with.

MIKE


Current project: tactile sensing systems for multifingered robot hands

 


Get Your Ad Here