motters is currently certified at Master level.

Name: Bob Mottram
Member since: 2002-06-08 19:03:04
Last Login: 2016-05-02 21:25:52

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I'm a self-styled robot addict living in Sheffield, England. Over the years I've built a couple of humanoids, and am mainly interested in building 3D occupancy grids for mobile robot navigation using SLAM algorithms and stereo vision.


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So, it's a very long time since I last posted here, and it looks as if the site will be closing. What happened with my projects?

Well, I stopped doing robotics stuff around about 2013. It was a deliberate choice to re-focus my effort on other things which I thought were of higher priority - those being more general internet service self-hosting along the lines of FreedomBox.

Between 2011 and 2013 I did a lot of development on the Turtlebot and also GROK2 - a very large robot about as tall as myself. Those projects were outrageously successful compared to anything I'd done previously, mainly thanks to the ROS operating system and the Kinect sensor. I devised a simple home navigation system which used a combination of button presses and text-to-speech so that you could direct the robots to particular locations in the house. Navigating through doorways was sometimes hazardous, but most of the time it worked.

I didn't completely lose interest in robotics or AI in 2013, and I think it's still very likely that in the coming years I'll return to some new robotics project. There are many challenges still to be overcome.

Fitted a D525MW mini-ITX motherboard to the robot, and installed Linux Mint 11 and ROS onto a 16GB USB flash drive.

This makes a good minimalist onboard computer, and was considerably cheaper than buying an equivalent netbook. To set everything up I connected a keyboard, mouse and monitor as usual, but once the motherboard was installed on the robot it only requires the wifi adaptor and USB drive to be connected. I deliberately didn't want to use a hard drive (although I have a couple of old ones available) based upon bad experiences with mobile robots and hard drives in the past. Also I reused some old PC speakers which havn't seen the light of day for probably more than a decade. You never know when such things may come in useful.

One trick with running the OS from a flash disk is to delete the existing casper-rw file, then create a partition labelled casper-rw. This enabled me to make use of the full USB drive, rather than being limited to 4GB of persistent storage.

The user interface of the robot currently consists of buttons and audio. When you press buttons the robot says something appropriate, so it's not so much a graphical user interface as an audio user interface. For the sorts of tasks I envisage the robot doing this is quite adequate, although if more elaborate instructions were needed I could add a small screen of some sort (finances permitting).

With the robot running I can then use either VNC or ssh to debug code or run different programs.

There's some tidying up remaining to be done on the head of the robot, Since the Kinect sensor's circuit boards are exposed and vulnerable to collisions. I'll devise some sort of covering to go over that.

An initial localising test run done earlier today indicates that everything seems to be working as expected, and the new computer can handle the processing demand. Even for a relatively simple differential drive robot like this there are a considerable number of electrical connections, and there's always some degree of trepidation over whether I've connected them back in the right order. Labelling everything helps a lot.

13 Jun 2011 (updated 13 Jun 2011 at 11:59 UTC) »

After a day of hacking, bashing and drilling I've slimmed down the GROK2 robot, reducing its width by 40mm on either side. This robot has an AL-101 chassis (Zagros robotics) and fortunately it's made from 3mm aluminium, which is just about sawable with some exertion.

This should give the robot more clearance when passing through doorways. It's still wide enough for a netbook, mini-itx or even a full sized motherboard but it's no longer wide enough to carry the laptop - at least not in the usual orientation.

It's always been in the plan to eventually have some permanent onboard PC, and at present it looks as if netbooks are just not quite up to the job unless they're the latest and most powerful devices (which are expensive). So I might have a go at installing a mini-itx, which are much cheaper than a high end netbook. I could then use a laptop or netbook to ssh into the robot. I have a couple of spare SATA hard drives which could be used, and also a couple of USB wireless adaptors. Another advantage of the mini-itx boards is that they can be run off of a 12 volt supply, which avoids the wasteful DC->AC->DC conversion.

All in all the future for robotics is looking very good, particularly for low hanging fruit applications, such as fetch and carry or just hawling stuff around. I think it would be quite feasible to build a prototype shop/supermarket shelf stacker robot, and also to add an autopilot feature to mobility scooters or wheelchairs.

9 Jun 2011 (updated 9 Jun 2011 at 23:07 UTC) »

It has been a while since my last blog entry here. As far as ambient events are concerned I continue to be an unemployed software engineer, with the prospects of re-employment looking increasingly remote, but in terms of robotics projects things are going very well indeed. In the last six months using ROS and the Kinect sensor I've made more progress than I'd made over the previous five years of SLAM and stereo vision development.

The GROK2 robot is now navigating well from one room to another. Tuning the localisation parameters took a while, but now the movement looks quite smooth and decisive. I've been able to have the robot navigate reliably to various locations in the kitchen, such as sink, kettle and table. It doesn't have any arms presently, but if I can get some object recognition going then adding an arm would be the next logical step. It's easy to become complacent, but the current level of navigation performance was, until only a few months ago, merely a vague ambition somewhere in the future.

One problem is that it looks as if the robot in its current form is just too wide to get through one particular doorway. This might mean that I need to do some mechanical hacking to thin it down a little and provide more clearance. The small amount of clearance currently available is just too narrow to realistically expect the localisation to be able to handle it reliably. As part of the redesign I may also add a dedicated onboard PC, rather than using a laptop.

Using this sort of system with a PC of some description and RGBD sensor the prospects for robotics over the next decade look far better than at any previous time. 2011 is probably going to be a watershed year in which both the software and the sensor technology became good enough for break-even navigation at a reasonable cost.

I've now added a Kinect sensor to the GROK2 robot, which is described here:

I think that 2011 could be quite an exciting year for robotics, with some real progress being made on age-old problems.

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