Wednesday, October 2nd, 2013 at 11:25 am - Hang-glide
Went down to the Hidden Earth cavers conference in Monmouth last weekend. After causing much mayhem and ranting regarding lasers and scanning (and that was before I had even trawled through Companies House records) I bagged a Sunday flight on Pandy owing to a rare forecast of easterlies and sunshine. I went to bed early while Becka stayed up forcing everyone, including my designated retrieve driver, to finish the Hilde-schnapps in the car-park at 3am. The retrieve driver not surprisingly had a hang-over in the morning and needed some persuading to come along. (“The fresh air will clear your head; you won’t be able to concentrate sitting here through all these boring lectures.”)
The best use for a football field — mass camping at a caving conference.
We got away at 10:30am, drove to the landing field (full of sheep), looked at the smaller landing field to be used when the first was full of sheep (surrounded by tall trees), then drove up. The wind was blowing between 22 and 29mph on the edge of the hill at take-off. That at least kept all the paragliders away. But there weren’t any hang-gliders either. Felt a little concerned about this. It’s always best to have a local at a new site to point out what’s safe and where not to go, otherwise you’re just guessing and taking chances. But nothing can actually go wrong until you’ve taken off, so we walked down to fetch the glider.
Just then, like the cavalry arriving, a car carrying three gliders with their friendly pilots turned up, and everything was great. They showed me their preferred take-off and told me how high you need to get before crossing over to the main ridge. Asked about top landing near the take-off, they said everyone has done it once, and then vowed “never again”. And don’t worry about the sheep if you can’t make the smaller landing field.
This has got to be an old idea. But I don’t know if it’s been done yet.
The issue is when a ball-nosed cutter of radius r goes over the edge of a part it spends a long time (between points a and b) in contact with the same point on the corner, grinding it away as it follows the green circular path (if it crosses the corner at right angles; otherwise it’s an elliptical path).
If you wanted nice crisp knife-edge corners, you aren’t going to get it.
(At least that’s my guess. I don’t actually know as I am not a machinist and don’t have access to a machine on which to conduct experiments.)
I have recently been doing a lot of curve fitting, which gave me an idea.
How about if I detected these outer circular motions and bulged them out slightly by a small factor e. Then the tool would leave the corner at the top surface when it is at point a, and rejoin the corner when it is at point b — and not grind it down smooth on its way over.
If we did this everywhere, would it make the whole part that little bit sharper and nicer?
Who knows? But I’m not going to spend my time programming it for the general case until I see some evidence that it does make a difference. It would be easy enough for a Process Engineer to directly design some special paths that only work on a test corner and do a set of experiments that involve scientifically quantifying the sharpness of the corners that results from this strategy — and then product tests the feature for desirability.
Now, who do I know who works in a large company that ought to be well enough organized to deploy resources to check up on an idea like this? Never mind. I can’t think of one off the top of my head.
There’s an 80% chance that this idea is garbage. It’s necessary feature of progress that there are many failed experiments along the way, because you don’t know what you are doing. Of course, if you did know what you were doing, you wouldn’t be doing anything new, would you?
If we did do these experiments and they didn’t work out, it would be very important to publish the results accurately so that the next people can either (a) avoid going down this dead end, or (b) spot something in our procedure that we didn’t quite get right.
(Let’s set aside the evil capitalist logic that intends to promote damage and waste external to the organization by ownership control, lying and deliberately withholding technical information.)
I believe I have recognized the hallmark of an innovative system — it’s one that is capable of funding these failures. It might seem efficient to direct all your programmers to work only on “real” projects. But if you do you won’t encounter the sequence of failures, abandoned experiments and learning opportunities that are an utterly essential part of the innovative process. Or worse, you’ll continue to push through on a serious “real” project long after it should have been declared a failure and learnt from.
This critique works on the pharmaceuticals system. New drugs require a great deal of innovation to develop. But we only reward the successes through a government-granted patent monopoly long after the work is fully complete. Who is paying for all the necessary failed drugs along the way? This crucial part of the system is overlooked. It is real work, and it has to be paid for. The official story is that the drugs companies recycle the profits from the successes into future failed experiments. But there’s very little quantified evidence of that.
So here’s to failure. We need more of it. And we need not to be frightened of it.
Monday, September 23rd, 2013 at 2:27 pm - Cave
I just spent a grey sky weekend down in Bristol investigating the cave surveying technology potential of this Hokuyo UTM-30LX-EW, that I bought with my much diminished pocket money.
I bought this one, as opposed to the slightly cheaper UTM-30LX that most robot research teams go for, because it is IP67 rated, as opposed to IP64. The IP Code says the first 6 means “Dust tight”, and second digit 7 means protected against “Immersion up to 1m” rather than 4, protected against “splashing of water”.
I know what caves are like.
I love Python, but its lack of multi-core support is killing us in the Adaptive Clearing strategy.
We’ve divided the algorithm into 8 separate threads that all work in a pipeline. Some of then can be operated in parallel (for example, the swirly Z-constant clearing strategy within an independent step-down level).
The heavy calculation is done in C++, but the high level toolpath planning, reordering, maintenance and selection from categories of start points is undertaken in Python.
While the C++ functions unlock the GIL (the Global Interpreter Lock) on entry, so that Python interpreter can carry on in parallel — and perhaps call another concurrent C++ function, this only gets us so far. Our limit is full use of two cores, which on a 4 or 8 core machine is a little embarrassing.
So we have two options, neither of which are good. One is to port our thousands of lines of Python code into C++ (which is not going to work as it will be too painful to debug this code yet again in another language that is much harder). And the second is to make Python multi-core.
Following my work attempting to create five axis toolpaths using tracking methods, I’ve fallen back to the more conventional techniques used to create 3-axis toolpaths of defining areas theoretically and then computing their boundaries.
For three-axis strategies almost everything is computed on an XY weave an efficient aligned subdividing structure. When things are aligned in this way it’s possible to be totally strict with the floating point calculations about what cell contains each point, and so rely on the topological and geometric reasoning being consistent.
This was the formerly unlisted video of my crash down on the Gyrn in Wales which made me feel quite sorry for myself with my total lack of competence and ability to have a good time with this sport (skip to 2min 30).
Then I went to Austria and life was great, particularly at Greifenburg.
Things weren’t so bad back at Loser either, with a series of take-offs and landings that I loved — all of them.
Back home in Liverpool I wanted to fly some more, but haven’t had the chance. Got offered a dive trip out to Liverpool Bay yesterday, and persuaded Becka to come.
Pretty murky all told, but did the job of dropping us into a thoroughly different universe where we happily swam with the fishes in the dark until the air ran out.
What more could you ask for out of an experience?
We all know how rotten software patents are. Unfortunately, software companies are too often run by idiots who play the game by contributing to the worsening of the situation and doing absolutely nothing to make it any better.
Anyways, 19 months ago in March 2012 we got a press release:
Delcam will preview its new Vortex strategy for high-speed area clearance on stand 4011 at the MACH exhibition to be held in Birmingham from 16th to 20th April…
Vortex, for which Delcam has a patent pending, has been developed by the company specifically to gain the maximum benefit from solid carbide tooling, in particular those designs that can give deeper cuts by using the full flute length as the cutting surface. It can be used for two- and three-axis roughing, three-plus-two-axis area clearance and for rest machining based on stock models or reference toolpaths…
Unlike other high-speed roughing techniques that aim to maintain a constant theoretical metal-removal rate, the Vortex strategy produces toolpaths with a controlled engagement angle for the complete operation. This maintains the optimum cutting conditions for the entire toolpath that would normally be possible only for the straight-line moves. As a result, the cutting time will be shorter, while cutting will be undertaken at a more consistent volume-removal rate and feed rate, so protecting the machine.
Sounded a lot like the Adaptive Clearing strategy which I invented in 2004, and was most accurately replicated in 2009 by Mastercam.
Thursday, August 22nd, 2013 at 8:02 pm - Hang-glide
We walked up the Trisselwand one the morning. Even at 8am there was wind blowing around the shoulder where the thermal updrafts can always be found. I walked back down while Becka bribed Tom and Matt with lunch at Appelhaus for going on a longer walk. They both ordered roast gemse, and then it rained properly for the rest of the day.
I was left alone at base camp for a couple of days to work while more caving and detackling was happening at top camp. Due to a meeting in the afternoon I didn’t get off for my cycle tour round Grimming till 4pm.
First I went to the secret lake which cut through between the mountain and the rest of the range that I had discovered from the air.
Then there was a long stretch on a major highway to get to the eastern end of Grimming and round.
I arrived at bast camp at 9pm as it was getting pitch black after five hours at full speed the whole way on just one apple and two pieces of flapjack.
Today I flew for an hour while the others did the Via Ferrata on the Loser.
The clouds were low and I got into their turbulent sunny edge. It felt like the most natural place to be. Then I headed over to the Tristlevan, and the thermal was missing from the usual spot, so off I bombed, passing over base camp on the way. They saw me from there this time.
We’re driving home tomorrow to face the real world. There is some kind of crazy autumn and winter I have in store coming up. I don’t know what it is but I’d so much rather be flying.
Sometimes you get a feeling when you start an idea that you’re going to spend the rest of your life debugging it to make it work.
The idea behind Adaptive Clearing just worked the first time I implemented it. The theory behind it is fundamentally sound. Trajectories in 2D are unambiguous, and you know when they come close and cross.
Monday, August 19th, 2013 at 4:40 am - Hang-glide
As seen for two seconds over Grundlesee. (Is there another name for it?)
Another very good day. Day before was cancelled due to over the back wind creating an enormous rotor in the valley, according to the locals who said not to fly, because you can always save it for another day. (Did I ever.) It’s good advice to take local advice. They described for me a couple more thermal hot-spots to know about in the different valleys, the kind that haul you up to cloudbase at 3200m and set you on your way. I tested one of them out, and have it in the bag for next year. Cold hands again without gloves. I loved every minute of it.