Susan and I were walking in the park this weekend and saw an abandoned animal carrier lying on the ground. It was a hot day and the carrier was in direct sun. The door was open but when I looked inside there were three cats; a mother and two kittens. They were too frightened to leave the carrier despite the heat and obviously being badly in need of food and water. It was impractical too carry a large plastic box full of cats 2 miles back to the house so we decided to walk home and drive back to pick them up.
When we returned in the car we noticed an SUV parked on the street nearby. It turned out someone else had noticed the cats and while they were looking at them, one of the kittens got spooked, made a run for it and lodged itself up under the rear wheel well of the SUV. I managed to crawl underneath and, after a bit of fumbling around in crevices, retrieved the kitten. We returned it to the carrier and loaded the lot of them into our car.
They were all pretty terrified initially. We moved them from the tiny carrier into our garage and gave them some food and water. They’re all very skinny and both kittens have injuries. One had completely lost its tail (I suppose it’s possible this is a natural mutation and not an injury?). The other was missing part of a rear foot. It looked as if it had been bitten off. The injuries weren’t life-threatening and appeared mostly healed. The kittens are still nursing but will also eat solid food.
The mother cat is a beautiful combination of pure white and a range of browns. It has blue eyes and looks like a mix between a Siamese and something else. The tailess kitten looks like a Calico and is still very frightened of humans. The kitten with the injured foot is mostly black with some white highlights and, along with the mother cat, has become quite friendly with us. The little black kitten also likes to explore and get into trouble at every opportunity. The personalities of the kittens made me suggest Zippy and Griffy as names but Susan prefers Trouble and Callie. We haven’t thought of a name for the mother cat.
We can’t keep them, of course, though it is tempting; particularly the mother cat. I’ve never seen such an amazing looking cat before. They’ll probably be headed to the DFW Humane Center this weekend and from there, hopefully, to a new home where they’ll be well taken care of.
Advogato has been down for something like three weeks now. I’m beginning to wonder if it will ever come back! I asked around on the Gimp IRC channel and learned that the server lost a power supply.
Meanwhile, the nigritude ultramarine page is hovering around 12-15 in the Google results. There just aren’t enough inbound links from high PR pages to compete with all those link farms and other black hat tricks. Just over two weeks to go.
I mentioned how bad Van Helsing was in my last entry. Since then we saw The Day After Tomorrow, which was pretty good. If you liked Independance Day, and can overlook the compression of a multi-hundred year sequence of weather events into one week, you’ll probably like this one. The Dick Cheney vice president look-alike is good for a few laughs. The movie remined me of the old Fritz Leiber story, A Pail of Air – though it got a bit colder in his story.
We also recently saw the latest Harry Potter movie, which was not as good as the previous ones, and The Chronicles of Riddick, which was also okay. These two were see once at the matinee price movies but still enjoyable. Next up, the release of the original, uncut, subtitled Godzilla; maybe this weekend.
I recieved the four 350 F capacitors (yes, I said 350 Farad) from Maxwell and we’ve been playing with them down at the DPRG Lab. It takes a few minutes to charge one from the bench supply at several amps. Once charged, we were able to run a small motor (no load) on one for over two hours. And they’re designed to be exactly the same size as a standard D-Cell battery. Just the thing for a BEAM über-photovore I think.
At the DPRG RBNO last night, I worked out the basic design for my robot power supply with the help of a few other DPRG folks. The plan is to use 4 of the Maxwell 350F caps to store power from solar cells. (Someone was asking about the cost – the single unit price of the caps is $25). One hitch to using multiple ultracaps is that you have to dynamically balance the voltage between caps. To do this you need a simple circuit made of an op-amp and a couple of resisters. You need one balancer at each connection between caps so, for four caps in series, you need three balancers. John Drummond helped me track down the TLC25L4CN low-voltage op-amp. It works on as little as 1.4v (which equates to .7v per cap). That gives me an operating range of 2.5v to .7v per cap or 10v to 2.8v for the entire power supply. Once I get the parts and test it, I’ll post a schematic.
In other DPRG news, the DPRG mailing list upgrades have been completed. The list now has better spam and virus filters, email address munging, and a shiny new searchable list archive going all the way back to 1997.
This review was originally written for the robots.net blog
MIT Press recently sent their latest book on mobile robotics, Introduction to Autonomous Mobile Robots by Roland Siegwart of EPFL and Illah R. Nourbakhsh of CMU. The book provides a load of useful information on mobile robot locomotion and navigation issues. If you’re struggling with the problem of how to make your robot get from point A to point B quickly and efficiently while avoiding obstacles, this book may have your answer. Read on for the full review.
Introduction to Autonomous Mobile Robots provides a succinct overview of mobile robotics with an emphasis on mobility. After a brief, general introduction to mobile robots, the book proceeds to break down the field into specific topics, such as kinematics, locomotion and navigation. Each topic begins with more summary of the problems faced by mobile robots, then presents the most common solutions or approaches. Almost everything covered by the book is useful and I would definitely recommend this book as an addition to any serious robot builder’s library.
The book almost reads like Cliff Notes for the robotics student. You can quickly pick up most of the current ideas and buzzwords found in the field of robot mobility, without having to read hundreds of pages of dry technical material. Need to know the six types of robot locomotion? See page 14. Want to see a chart of every possible wheel geometry for wheeled robots? See page 34. How about a breakdown of robot sensors by active vs. passive and proprioceptive vs. exteroceptive? See page 91. A list of just about every known obstacle avoidance algorithm? See page 287. Well, you get the idea. There are a couple of curious omissions, however, including a complete lack of information on subsumption (as well as behavioral robotics in general) and BEAM technologies. There is also no discussion of common standardized robot operating systems such as Orocos or Player/Stage. It would have been useful to see a comparison of the technologies and algorithms supported by off-the-shelf software.
The book includes enough detail that it should be easy to understand and implement the strategies described. There are also frequently references to further information on selected topics.
Because the book is aimed at college-level readers, it doesn’t hesitate to present the math associated with the subject when necessary. The technical detail puts this book a notch above the average hobbyist level introductory robotics book. Almost anyone building robots has searched, at one time or another, for an algorithm or formula that can easily be found in this book. For a hobbyist who has built a few simple robots and would like to learn more advanced technologies, this book would make a great introduction to the methods and algorithms being used in university-level mobile robot research institutions like CMU and EPFL.