DPRG
DPRG List  



[DPRG] RE: How much do our choices effect our results?

Subject: [DPRG] RE: How much do our choices effect our results?
From: Randy M. Dumse rmd at newmicros.com
Date: Sat Aug 11 13:59:31 CDT 2007

 
dan michaels said: Friday, August 10, 2007 8:25 PM
> It's possible they were having the sidelobe problem I 
> mentioned last time, if they didn't have the Rx transducer 
> pointing upwards into space. As I mentioned, I found the 
> SRF04 sidelobe to be pretty bad.
> 
> I haven't tried the maxbotics sonar yet. Actually, I'm not 
> sure sonars are very good below 6" anyways. Problem is they 
> send out such powerful pulses that you can get multiple 
> reflections at close distances and which read out as a much 
> longer distance. I had this problem with my walker
> Nico-6 when turning close to a wall, when it was at certain 
> oblique angles. I think what was happening is the beam would 
> reflect off the wall to the bot frame and back to the wall 
> and then to the Rx transducer.
> 
> A smarter sonar would be able to limit its output power for 
> near-on distances, to prevent multiple reflection problems.

Yes, I am sure the false near sensings were side lobe related.

Last summer I tried to use a SRF10 on the Queen of Jordan
project. They were even worse. Found this interesting site about
using tubes to direct them. I didn't try it, but it has some
interesting ideas of what might be done.

http://www.robot-electronics.co.uk/htm/reducing_sidelobes_of_srf
10.htm

I too was thinking the right approach might be to have variable
power transmission. Most rangers have variable gain, which turns
up with time. The idea of having tunable power seems very
desirable in robotics applications where often the closest thing
is the most important. Also tunable frequencies or coded
transmissions might help, where a pulse can be distinguished
from the previous sent. That way the sensor could be cycled more
quickly for close objects, without having to worry about
multipath returns of longer duration.

Anyway, there are many possibilities. Who is working on them
today? To me it seems the market place is rather static, quiet.
Maybe breakthroughs will happen, which are just out of sight,
but I have to wonder if we as the robot enthusiasts aren't
making our voices heard, that we want better sensors to build
better robots.

Randy
www.newmicros.com



More information about the DPRG mailing list