Author Topic: Need advice about sensors for collision avoidance outdoors.  (Read 872 times)

0 Members and 1 Guest are viewing this topic.

Offline HewhowalkTopic starter

  • Jr. Member
  • **
  • Posts: 14
  • Helpful? 0
Need advice about sensors for collision avoidance outdoors.
« on: February 19, 2010, 07:12:08 AM »
Hi!
I'm working on a robot for outdoor usage. Now I'm reaching the stage were I am supposed to choose some range sensor(s) for collision avoidance and would like some input from a third part (you guys). The robot should be able to work in all kinds of weathers , except snow or perhaps extreme rain, be able to see >3m and have resolution around 1-2cm.

The sensors I am considering so far is:

1. Laser scanner using triangulation, similar to the one used by the neato robotics vacuum-cleaner http://www.neatorobotics.com/

2. Ultrasound with Time Of Filght measurement and signal processing to filter unwanted noise.

3. Millimeter wave radar. Seems incredibly robust, but I can't find any price. Will not try to build one myself.

4. Structured light. Seems interesting.

Vision sensors of any kind will not work I think, since the robot have to able to work nighttime aswell as daytime.

Laser scanners with Time Of Flight measurement is to expensive.

The budget I have is approx. 200 dollars.

Any of you guys have experience of using any of these sensors outdoors? Which of them should I choose?

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Need advice about sensors for collision avoidance outdoors.
« Reply #1 on: February 19, 2010, 08:02:18 AM »
Hi,

I'm working on a robot for outdoor usage. [...] The robot should be able to work in all kinds of weathers , except snow or perhaps extreme rain, be able to see >3m and have resolution around 1-2cm.
What size/weight is it and what's the top speed?


3. Millimeter wave radar. Seems incredibly robust, but I can't find any price. Will not try to build one myself.
Smart move. I guess you might find something if you chat up a technician repairing mall doors and such - some of them use RADAR (I have such a unit, not something you just bang together).


4. Structured light. Seems interesting.
Huh?


Vision sensors of any kind will not work I think, since the robot have to able to work nighttime aswell as daytime.
Infrared and an electronic aperture control (as used in CCTV) might be a choice.


The budget I have is approx. 200 dollars.

Any of you guys have experience of using any of these sensors outdoors? Which of them should I choose?
Black night to heavy sunshine - that's a vast dynamic range for any optical based detector to handle. I'd go with RADAR or ultrasound. The latter will probably be fine and with a couple of units it shouldn't be too hard to cover your range. I assume you need more precision as you get closer, so perhaps add a Sharp distance sensor for close range, but tandem it with the ultrasound, in case it's blinded, or perhaps use one or two cheap photographic ND filters (Neutral Density) for swapping in front of it when the light increases).
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 HewhowalkTopic starter

  • Jr. Member
  • **
  • Posts: 14
  • Helpful? 0
Re: Need advice about sensors for collision avoidance outdoors.
« Reply #2 on: February 19, 2010, 09:08:41 AM »
Thx for your response.

The robot is 80x70x31 cm (LxWxH) and weighs approx. 14 kg and has a top speed of 0,7 m/s.

Structured light is a method were a light source projects a pattern of light (line or grid) and the pattern is observed by a camera. By using triangulation you can calculate the distance to any point in the pattern. And if the light hits an obstacle the pattern will be distorted.
This seems like good way to use the triangulation solution without the need for a motor.

If I choose a filter in front of the camera that filters everything but my wavelength I should be able to use laser. Of course the sun will contain that wavelength as well, but hopefully not of the same instensity as the reflected laser. Especially if the camera is shielded from direct sunlight.

But probably ultrasound is the way to go, since I still haven't got any idea of how much the RADAR units cost, though I would prefer a LASER solution since it's "cooler". :)



 


Get Your Ad Here