Robot Docking Explored
Friday, 31 August 2007

You probably remember C6Jones720's series of articles on 914 docking and charging. Chris mentioned in one of the articles that he had spoken to a member of robots.net named CSchur who was compiling a report about robot auto-docking.

CSchur's report has now been published. You can check out the report via robots.net, which is entitled Robot Docking Explored.


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Dynamite With a Laser Beam!
Wednesday, 29 August 2007

Ok, so there's no dynamite, but there is a laser beam. I've managed to get hold of a SICK PLS101-312 laser proximity scanner. This is very similar to the blue SICK LMS200 lasers that you may have seen on various robots, the only difference being that the PLS range of scanners are designed more for industrial automation as they have programmable zones that can be used to signal to machinery when an object is present, for safety cut-off etc. There's a good comparison table a little way down this page as well as a tutorial in interfacing with the device.

A SICK LIDAR wouldn't have been my first choice of laser scanner to buy, mainly due to it's size and the fact that it runs from 24V. However, this one was very cheap (eBay - no one else bid), so I didn't really have too much choice. I would much rather have had a HOKUYO URG laser as they are about the same size as an IP webcam, run from 5V and have USB on them. However, both types of laser are directly supported by Player/Stage and other various software, so this will give me opportunity to try out some things that I wouldn't otherwise be able to afford to do.

All of these laser scanners work in pretty much the same way - basically a laser is reflected from a spinning mirror outwards in a plane spanning 180 degrees. The device times how long it takes for the light to reflect back from objects that it hits, and works out how far away they are. This provides data which is almost as good as a map of the environment - and it does this ten times a second or more.

Unfortunately the black front visor/screen was missing on the unit I bought, so the one on there now came from a faulty unit, but it's scratched which makes the PLS see things that aren't there, and it also constantly complains that it needs cleaning. The unit works ok without it, but dust contamination is a big issue for these types of device, so I have a new screen arriving shortly. Here are some pictures of the PLS - you can see the mirror inside that rotates when it's turned on as well as the very scratched screen:

Here you can see the PLS dwarfing my IP web cam, which is similar in size to the HOKUYO laser I mentioned above - and also the largest thing I was planning to stick under my 914's lifting head. There are also two pictures that show the scan produced by the PLS, the large blue area on the screen is a distance of 4 metres / 12ft. You can also see that right in the middle of the scan it sees an object very close which isn't really there due to the scratched screen.

My next steps with the PLS will be to (somehow) mount it on the 914 and power it while the robot is mobile. Then I can use the localization, navigation and planning drivers that come with Player/Stage, along with PlayerNav. This will allow for a map of the environment to be supplied and for the Bot to locate itself within the environment, plan a path, then navigate to another location. All this is provided out of the box and seems to be as easy as dragging the Bot in a GUI from point A to point B - then watching it sort everything out and get there itself. Of course it's the laser that makes this possible because it makes it easy to match features of the physical environment to the map, and easy to see obstacles it has to avoid. The Wavefront, AMCL and VFH drivers/algorithms are provided with Player which take care of all the tricky stuff. Of course I can also write my own program that gives the Bot a new x/y grid reference on a map of my house for instance, but not have to worry about programming the actual navigation myself.

Until the next installment I'll leave you with these two YouTube videos. The SICK lasers were used on most of the DARPA Grand Challenge robot vehicles including the winner, Stanley, which has five similar SICK laser scanners on it's roof. The Stanford Racing Team are of course also entering the DARPA Urban Challenge - the first video is a nice run down of their urban robot vehicle which appears to have at least two SICK LMS291's on it. The second video is another laser scanner guided car at the VW test facility in Germany. This video is worth watching until the end where the car drives at top speed around the course by itself.

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Monday, 27 August 2007

We have previously seen a black 914 named Darth Brooks, as well as Tom Burick's personal red 914 named Vincent.

Although it appeared from a recent survey that White was a the most popular 914 colour, Richard Lepack has now sent me some pictures of a GOLD 914 PC Bot which I have added to the image gallery.

Richard had this 914 painted by Dan Lessard of Rembrants Brush. I'm guessing that this is either a custom job for a new proud 914 owner, or a demo piece for industry shows and the like.

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Odometry Man 002
Sunday, 26 August 2007


This week Odometry Man returns with some new characters who use the power of SLAM to solve a simple geometry problem. Please click on the preview above to get this week's episode of Odometry Man full size (300Kb).

I'm still finding my feet with Odometry Man, although I intend that his next appearance will be the start of a multi-part storyline - with a plot and everything!

Comic episodes will still be published each week on Mondays and remain archived in the 914 Comic Series section.

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Rotating and Lifting Head Pt2
Thursday, 23 August 2007

This is the second part of my 914 rotating AND lifting head mod. I'm writing about it as I build it so I can talk about issues I have resolved and show progress as it goes, but it's still looking pretty good so far!. Check out part one if you missed it before.


I've started on the electronics this week, they are based around two PICAXE 18 'high power' project boards which have four power output devices each capable of sinking 1.5A which is fine for my 1A per phase stepper motors. This will be interfaced to the serial port of the mini-itx board so that I can send commands like 'head up/down' etc.

I also built an SMA extension lead for my wireless bridge so it can be mounted in the drive bay area of the Bot - while the aerial is kept in the head where it is not surrounded by metal.

The eye assembly still fits in the head shell along side the lifting mechanism. I've made a small aluminium bracket to hold it in place - both this and the aerial are mounted on the studs/screw threads that originally were the mounting points for the head plastic to the chassis.

The rotating stepper motor is coupled to the turntable part as originally planned. However, since the motors are 1.8 degrees per step, even with stepper motor interleaving for half steps, the motion is a little jerky. I'll be building a custom gear box over the next week or so to bring this down by a ratio of at least 3:1. I also found that the original coupling between the lifting stepper motor and it's threaded drive shaft was not straight. This made the lifting motion kind of move in a 'wave motion'.  I've made a new longer tighter coupling out of a bit of HDPE that holds the two shafts perfectly end to end.

The long and short of it is that it works ok to lift the head up. It’s a little slow, but this is mainly because the stepper motor cannot be driven at more than 880 pulses per second. I’ve been starting at 200 pps right at the bottom of the lifting range to give more torque, but I’m planning to ramp up the speed over the 3800 total steps for the full range of the lift.

There's a picture below of the view up inside the head shell - you can see there is quite a bit of space there to store extra sensors etc which was the original intention of the project.

Next steps are to polish off the electronics and rotating gear train - then do a little cosmetic tidy up. I've still not decided if I will try to hide the lifting mechanism from view when the head is raised, but I think I'll try flooding the area with lots of blue LEDs first.

You can also find all these pictures in the Image Gallery. Watch this space for part three!

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I will develop software for my 914 using...
Tuesday, 21 August 2007

ImageI've started a new survey entitled 'I will develop software for my 914 using...'. This is of course mainly aimed those who want to develop there own software for their PC Bot - although it's not as hard as it used to be to write computer programs, so I'm hoping that the 914 has motivated some people who don't consider themselves programmers to have a go!

We ran this survey before, but I've decided to run it again because it's probably more relevant now - as well as there being extra options to vote for as the product and it's availability has progressed. If there are any major options missing from the survey then let me know or post it in the linked thread below.

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What is your favourite 914 colour?
Tuesday, 21 August 2007

I have now ended the 'My favourite 914 colour is...' survey. The results are great because it just happens that the 914 comes in white!, and because it's white you can paint it any other colour - just as Tom Burick did with his very own 914.


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914 Comic - Electric Sheep
Sunday, 19 August 2007
Image Here's this weeks episode of the online 914 comic book. It's back to C6jones720 this week for something AI related.

Comic episodes are published each week on Mondays and remain archived in the 914 Comic Series section.

Please click on the preview to the right to get this week's episode full size.

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RoboRealm Visual Anchor
Tuesday, 14 August 2007

ImageRoboRealm has another great new module which is of specific use the 914 owners. The Visual Anchor module provides data that would allow a Bot to navigate to a specific location within it's field of view until the camera image matches the given target. I guess this could be used for homing in on a charging dock or other item, you could also detect if the Bot is moving when it should be - or if the wheels are slipping. From the RoboRealm website:

"In RoboRealm's continued investigation of image stabilization the Visual Anchor module has been added. This module allows a robot to know how far it has moved with regards to a known scene. This module uses a technique classified under Visual Odometry. Visual Odometry uses vision to calculate how far you have travelled instead of using encoders. This has the advantage of being more accurate in situations where wheel slippage is expected (such as travelling on the sandy Martian surface!)."

Don't forget, RoboRealm is FREE to download for a fully functioning version with no limitations.

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New 914 Resellers
Monday, 13 August 2007

ImageWhite Box Robotics have now partnered with two new resellers in Japan and Australia - which is quite handy if you live there and want to purchase a 914. These are SMATS Corporation and Zytech.

You can see the full list of resellers on the White Box Robotics corporate website.

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Odometry Man 001
Sunday, 12 August 2007


This week we have a slightly different comic theme, which I've been thinking about creating for some time now, called "The Brand New Adventures of Odometry Man!!"

Odometry Man is intended to be a semi-educational comic related to robotics. Please click on the preview above to get the first episode of Odometry Man full size (243Kb).

C6Jones720's comic will return next week as he has plenty more episodes lined up. Odometry Man will probably make another appearance in a few weeks, mainly because it takes me quite a long time to draw...

Comic episodes will still be published each week on Mondays and remain archived in the 914 Comic Series section.

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