What sonar system(s) are you using?

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What sonar system(s) are you using?

Postby roadknightlabs » April 2nd, 2007, 4:35 pm

I'm wondering what sort of sonar sensors people out there are using in their Roomba projects. Anybody have any particular favorites or opinions re: The Devontech SRF04 vs. the Maxbotix LV-EZ1 or the Parallax Ping))) ?

Is there a particular type/system that is better for object detection vs. ranging? (I'm more interested in object detection at this point).
Let's get quibbling... :)
Thanks...
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Postby vic7767 » April 2nd, 2007, 6:26 pm

I'm gonna try the MaxSonar?-EZ1? because of good object detection and the fact that there are two of them sitting on the desk. Don't know whether to use the rs232 output or the D to A. Not sure if I'm gonna use the roomba red and a Basic Stamp or use the Create CM and the ATMega168 ports.

As you can see all the stuff is in place I'm just not committed to either robot platform yet....

Where are you headed.
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Postby roadknightlabs » April 2nd, 2007, 7:29 pm

vic7767 wrote:I'm gonna try the MaxSonar?-EZ1? because of good object detection and the fact that there are two of them sitting on the desk. Don't know whether to use the rs232 output or the D to A. Not sure if I'm gonna use the roomba red and a Basic Stamp or use the Create CM and the ATMega168 ports.

As you can see all the stuff is in place I'm just not committed to either robot platform yet....

Where are you headed.


I like that I can get the Devontech pair for the price of one Maxbotix, although the RS-232 on the EZ1 is also tempting. I'll let you know what I get.

I've got a bunch of different controller options. I've got an Arduino, B.O.E. and a Sharp Zaurus. The Zaurus lacks multiple IO ports though, so I will probably end up using the Arduino.

I'm not going to be needing a circumferential array of them, just one or two aimed right ahead.

I'll keep you all posted on what I do.
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Postby roadknightlabs » April 10th, 2007, 1:52 am

roadknightlabs wrote:
vic7767 wrote:I'm gonna try the MaxSonar?-EZ1? because of good object detection and the fact that there are two of them sitting on the desk. Don't know whether to use the rs232 output or the D to A. Not sure if I'm gonna use the roomba red and a Basic Stamp or use the Create CM and the ATMega168 ports.

As you can see all the stuff is in place I'm just not committed to either robot platform yet....

Where are you headed.


I like that I can get the Devontech pair for the price of one Maxbotix, although the RS-232 on the EZ1 is also tempting. I'll let you know what I get.

I've got a bunch of different controller options. I've got an Arduino, B.O.E. and a Sharp Zaurus. The Zaurus lacks multiple IO ports though, so I will probably end up using the Arduino.

I'm not going to be needing a circumferential array of them, just one or two aimed right ahead.

I'll keep you all posted on what I do.


Okay, so just to bump this thread up a bit, I thought I'd let you know I ordered a pair of the MaxBotix LV-EZ1s from Sparkfun this afternoon.

I decided not to go with the Devontech because I figured it would probably be more than the EZ1s with postage from the UK.

I also decided to buy the MaxBotix rather than just the transducers themselves because I want to work on the range-finding project as a whole more than I want to build a circuit from scratch.
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Postby vic7767 » April 10th, 2007, 12:18 pm

Range finding and object recognition are a couple of things I'd like to try also.
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Postby roadknightlabs » April 11th, 2007, 4:16 pm

w00t!
My sensors are here :)
I'll post a review/some notes probably after the weekend when I've had some time to experiment with them.
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Postby roadknightlabs » April 26th, 2007, 4:21 pm

roadknightlabs wrote:w00t!
My sensors are here :)
I'll post a review/some notes probably after the weekend when I've had some time to experiment with them.


Okay, so I've had some time to mess with these and have to say I like what I've seen so far. They are trivial to hook up and use if you just want to use them singularly. Using them in parallel requires a bit more work, but there are ways to do that.
I won't go into too much detail on that, there's plenty of documentation elsewhere, like on the
MaxBotix website.
I have attached a couple images below of my setup on "Mack", my Sage, with the one sensor and the output of letting it sweep around in our living room area for about 10 revolutions. The data was read off the analog output into an Arduino board and then sent over a BlueSMiRF to my laptop in the other room, which caught it and then piped the output into gnuplot.

I think Rosie, our Discovery, is the blob of solid hits up around Y=100 X=50 at around 330 or so degrees. The doorway going back down the hall towards the entrance I think is that gap near 180-190 deg. The rest of it is kind of hard to make out. There's random bits of furniture around the room but since Mack can zip under it, the only thing that he's going to "see" are the legs, which kind of get lost in the clutter.
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Roomba Radar. Results of a single Maxbotix sonar sensor sweeping a room for about 10 revolutions to get a good set of readings.
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Postby vic7767 » April 26th, 2007, 6:36 pm

roadknightlabs, that is really some nice work ! Is there a way to possibly slow down the sweep revolution and get more detail, like more pings per degree ? Also with two will you be able to get higher resolution and/or 2 dimensions ?
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Postby roadknightlabs » April 26th, 2007, 7:27 pm

vic7767 wrote:roadknightlabs, that is really some nice work ! Is there a way to possibly slow down the sweep revolution and get more detail, like more pings per degree ? Also with two will you be able to get higher resolution and/or 2 dimensions ?


Thanks. There will be more to come to be sure. This is really just a sort of "First light" image with very little post-processing. There's no hysterisis in the code or filtering for artifacts. The image is readable to me because I was very conscious of the Roomba's orientation and position in the room when I started the sweep and I'm already quite familiar with where things are so I knew how to set up the graph. It looks cool enough that I just had to post it though and I think shows a pretty realistic picture of the room.

I want to get a second sensor working, but need to get some additional parts (74HC04 Hex inverter among other things) in order to be able to hook two together because they have to be chained off the sensors' TX ports.

I'll post code(Arduino sketch and UNIX shell) when I get things a bit more refined.
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Postby ambrus » May 4th, 2007, 3:07 pm

Roadknight, that's a sweet setup! You could get some pretty detailed mapping done with that sonoar. Having played with a Devantech SRF04 and looked at your images, it looks to me like the inner ring of sonar returns might be coming from the ground itself. Have you considered mounting the sonar on some sort of stalk to give it more ground clearance?
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Postby roadknightlabs » May 4th, 2007, 3:20 pm

ambrus wrote:Roadknight, that's a sweet setup! You could get some pretty detailed mapping done with that sonoar. Having played with a Devantech SRF04 and looked at your images, it looks to me like the inner ring of sonar returns might be coming from the ground itself. Have you considered mounting the sonar on some sort of stalk to give it more ground clearance?


Thanks! I'd love to hear about your experience with the Devantech sensor as that's something I looked at before going with the Maxbotix one.

You're correct in that some of the readings I was getting were due to wobbling during movement.
I noticed that the mount I had it on was wobbling quite a bit, even when the Roomba was moving slowly. I've anchored it down with an additional piece of velcro and that seems to have cured some of the erroneous returns I was getting.

I'm going to add a second one soon so I can get stereo sensing looking forward.
I'd like to add additional ones to the side so I can do some wall-following/wall-sensing(since it appears that the wall-following IR sensors are note exposed to use/reading via SCI).
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Postby ambrus » May 7th, 2007, 9:52 pm

You can access the wall sensor via the SCI; it's the second byte in sensor packet 1, but only reads 0 or 1. Mine works just fine on the Roomba Red through the SCI, but the range on it is only about 8cm so trying to wall-follow using it means very close-quarters. A sonar would be much better :)

As for the SRF04, I used one for my work briefly last year, mounted on the front of an RC car chassis. The idea was to approach a target (usually a rock/boulder) using vision guidance and have the vehicle automatically stop at a specified distance. We used the sonar for close-in range measurements, but the major problem we had was that the sonar would give "false" returns from uneven ground just in front of the vehicle, rather than receiving a return from a the rock.

I was looking at the SRF08 just yesterday....it's a sweet, sweet system. It'll sense up to 16 returns from various objects on a single ping (that way you can see what's "behind" the first return). The price tag's a little hefty for a single unit though so I opted for three SRF02's for the same price instead.

I'm looking forward to seeing more of your results :)
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Postby roadknightlabs » June 20th, 2007, 4:10 pm

I just thought I'd give you all a bit of an update here.
I've crafted a Maxbotix mount for my iRobot Create that I got about a month ago. I made it out of a few DB9 connectors, some hex standoffs, heat-shrink and electrical tape. This mounts on the center ePort and takes pins 5, 4, and 2 respectively up to the Maxbotix sensor's GND, +5V and AN pins so it uses the sensor's free-run analog ranging mode.

It's probably going to pick up a bit of a reflection from the deck of the Create, but I think I can probably filter that it out. I wanted it to be high enough that it wouldn't pick up the IR dome on the front of the 'bot, but low enough that it could get under things like tables, chairs, etc.
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Maxbotix sonar sensors

Postby pohwder23 » June 27th, 2007, 3:22 pm

Hey roadknight!

This is my first time up here on this forum :D and I'm doing a project where I have to connect 4 Maxbotix sonars to a Create robot. The robot will have a mini-ITX computer on it and a Creative Labs Live! Motion Webcam as well. The mini-ITX will be connected to the serial port of the robot and the camera connected to the USB port of the computer. I was wondering if you could go into detail on how you came up with and wired the printed board setup for the Maxbotix sensor you used? Not the sensor mount rack one, but the one with the Maxbotix in a little clear case and connected to the mini breadboard in the yellow container. I looked at the picture, but they were hard to see exactly how you wired them together.

Also, if you have any suggestions for wiring the four sensors to the robot, feel free to give detailed information on that as well.


Thanks a bunch!

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Re: Maxbotix sonar sensors

Postby roadknightlabs » July 1st, 2007, 2:38 pm

pohwder23 wrote:Hey roadknight!

This is my first time up here on this forum :D and I'm doing a project where I have to connect 4 Maxbotix sonars to a Create robot.


Hi!
Welcome!
[...]
I was wondering if you could go into detail on how you came up with and wired the printed board setup for the Maxbotix sensor you used? Not the sensor mount rack one, but the one with the Maxbotix in a little clear case and connected to the mini breadboard in the yellow container. I looked at the picture, but they were hard to see exactly how you wired them together.


Okay, so the little white case is my own hack. It's basically using the carrier/holder for an SD memory card as a holder for the Maxbotix sensor.
It came together with the help of some right-angle header pins, an X-acto for cutting out a space for the sensor's card-edge, some #26 wire and some electrical tape.

The breadboard itself is attached to an Arduino board with a prototyping "Shield" module stacked on top of it. I'm actually taking the AN, PWR and GND pins from the sensor and hooking them up to the A0, +5V and GND sockets on the Arduino board.

Also, if you have any suggestions for wiring the four sensors to the robot, feel free to give detailed information on that as well.


Thanks a bunch!

pohwder23


Well, what I'm doing isn't actually hooking the sensor up to the 'bot so much as I'm hooking the sensor up to the Arduino board and then that is connected to the SCI(serial) port. There's some code running on the Arduino that takes readings off the analog port, then based on those readings makes decisions about what commands to send down the serial port to the 'bot.

For wiring multiple sensors to a controller there are a couple things you can do. First, if your sensors are spread/oriented widely enough apart from each other(say, 90 degrees or so), you can let them run free by just pulling readings off the analog port. If they're closer than that, it gets a little tricky because you need to worry about reflections, echoes, etc.
The Maxbotix does have a pair of RS232 pins on it to operate the sensor in "triggered" mode, where you would send a signal down the TX line on your side to the RX pin, telling it to fire. The Maxbotix FAQ and User guide have a lot more detail about how to use that mode than I could type up here.

Hope that helps...
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Postby pohwder23 » July 1st, 2007, 3:46 pm

Thanks a lot! That helped me out tremendously...and thanks for welcoming me to the group...I felt right at home! :oops:

I let you know how things turn out with the project. Thanks again!

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Postby roadknightlabs » July 16th, 2007, 3:08 pm

So here's the latest update:
I, unfortunately, have not had much time for the 'bots over the past couple weeks until this weekend. The good news is that I have my Create scooting about our apartment fairly autonomously, navigating by sonar and not running into things.
This is using the "eyestalk" mount for the single sensor I've posted about a few weeks back. Any concerns I had about the sonar sensor being mounted too low and possible picking up reflections off the deck/shell of the Create itself have been put to rest. If anything, it might be a bit too high up as it tends to miss things within the immediate 12" or so of it.

For example, it ran into the Roomba Sage that sits next to it when they're both charging, but had no problems picking it out from further away upon re-entering the room.

There's still some work to be done on the software and I need to add lateral sensors on the side for manuevering in hallways, but I thought I'd share a couple clips of it out and about yesterday afternoon.
[youtube]http://www.youtube.com/watch?v=qIzjD1mmed0[/youtube]
[youtube]http://www.youtube.com/watch?v=Sy22NYQXxmg[/youtube]
[/youtube]
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Postby THX-1138 » July 16th, 2007, 5:07 pm

:D This great progress!!! Have you thought of using a 'sweeping' tecnique by swiveling the sonar sensor instead? Also, a bit more advanced, will it be able to store the mapping for future use by the robot? I am asking since I am working on something similar but with Mindstorm NXT kit. :wink:
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Postby roadknightlabs » July 27th, 2007, 5:16 pm

THX-1138 wrote::D This great progress!!! Have you thought of using a 'sweeping' tecnique by swiveling the sonar sensor instead? Also, a bit more advanced, will it be able to store the mapping for future use by the robot? I am asking since I am working on something similar but with Mindstorm NXT kit. :wink:


That's the general direction I'm heading in. Now that I've been able to reliably sense and process sonar readings for sometime, I'm interested in using those readings to see if it can recognize objects or features. I think I'm going to be repurposing my Zaurus again for a whole 'nother project in the not too distant future.

The rotating platform idea is interesting, but a bit more complex than I'd like to get into right now. Is that what you're doing w/ your NXT set?
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Postby THX-1138 » July 27th, 2007, 8:42 pm

The rotating platform idea is interesting, but a bit more complex than I'd like to get into right now. Is that what you're doing w/ your NXT set?


Yes, this is what I am working on and these are what inspired me to do so:

[youtube]http://www.youtube.com/watch?v=XLXOrxLfNFo[/youtube]

[youtube]http://www.youtube.com/watch?v=eQakxSRt37I[/youtube]

Here is more info on the first video Radar project:

NXT ROBOT DESIGN - RADAR


PS:

RKL, is this what you are trying to do?

[youtube]http://www.youtube.com/watch?v=ifFc9JW-iFM[/youtube]
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