Category: Uncategorized

INV 11 – Robot Arm Wrestling – Leaf 1 – Proportional Control

On By cjx07sterIn Automata, Control, Engineering, Innovation, Intelligence, Travel, UncategorizedLeave a comment
Courtesy Aralani

Blogubarra – May ’11

OK Computer – I admit that i am writing this post today, inspired to write this down having seen all sorts of my colleagues come to grief after a few seconds of fun riding mechanical bulls.  These bulls seem to be all the rage in Texas at least.  I’ve just got back from there, and lets face it, felt a bit more than afraid of getting on one, putting myself in the hands of some kind of cowboy operator with a manual  controller, with the crowd screaming:-

“Make it go faster”

And the poor guy falling off after around 3 seconds.  Mechanical bull riding seems all about the embarrassment of novices rather than, actually having fun on the bull..  never mind. !

So this innovation is hypothetical, how would you create an unbeatable robot controller, which could not be beaten at arm wrestling, which was evenly matched in brain and brawn to it’s contestant, man or woman, with a beer in hand.

So innovation 11 is a cautious step down this pathway…

Mark I iRobot wrestler has a strong arm, a hand, and a controller managing the arm and it’s own winning strategy.  The initial controller is just a proportional controller, or servo regulator, and has a strategy relating to the setpoint or angle of the arm from the vertical.

I step up to the arm, have beer, see the lighted buttons, and plan to select “Right ARM” which is the hand I will use to wrestle the robot.

“Got any change mister ?” says the robot

“Sure”, I say

“Up for a challenge then… bet you can’t beat my arm !” says the robot.

“No worries mate, I wrestle tractors all the time, downunder.  You have no chance.” I say.

I sit down, adjust my Akubra, and then just put in the money, select right arm fast, grab the arm and see what happens.

The robot arm instantly starts humming and pushes up to the vertical position.  I let it, ‘cos I want to see what it does.  So the arm is just sitting there at vertical.  I push left, the restoring force on the arm increases directly proportional to the force I use to push it over.  The more I push, the more the robot arm leans over, but the more force I have to apply to get it to lean over.

At about 45 degrees to the left, the robot says ” ah I see you are stronger than I thought, I must apply more effort. ”

“No worries I say, go for it ”

The robot arm strategy engine figures that its proportional gain may not be enough since I got it over to 45 degrees, and I challenged it with “No Worries Mate”, something the robot didn’t understand.  But correctly guesses it had something to do with confidence, purely by the tone.

So suddenly the force increased and it had pushed my arm back to 22 degrees from centre.

I figured ok, proportional control being used here, because I can just keep on pushing and the robot can never win. I wondered what other tricks it had up it’s sleeve.

after 1 minute the robot says impatiently “Look buddy, I don’t have all day, so I am going to finish this off in about 30 seconds”

I quickly think, 30 seconds, the robot must be going to change the setpoint to 90 degrees against me.  So I have 30 seconds to figure out how to defeat this.

I figure, since the robot is currently set to drive the arm to the vertical before the ‘coup de grace’ all I have to do it trick it into driving the arm my direction, and then suddenly I can win.

“Hey Robot, I exclaim, in 10 seconds you will be defeated!”

Before the robot has time to reply, I gradually relax my arm and the robot arm pushes it to vertical, right up in the middle, and at that point there is no force from either me or the robot. I suddenly pull the robot arm past vertical to the point where it is about 10 degrees from winning, I move fast so that the momentum of the arm moving helps move it further before the restoring force catches up.  Since it is proportional control, and the robot hasn’t changed the setpoint, the robot controller immediately applies a restoring force to push the arm back to vertical, i.e. going my way, with full force.  I suddenly reverse direction and both the robot controller and I are both pushing the arm at full force in my direction.

“Geronimo” I exclaim, the robot arm moves rapidly past vertical in my direction and the momentum of the heavy arm and my force push it over further and further until it hits the table.

“Uncle !” says the robot.. – who taught this thing language ? who the hell is “Uncle” ?

“Mate !.. see thats how it is done. Cheers “.

Proportional Control

In proportional control, the controller generates an output or restoring force proportionally equal to the difference between the setpoint and the actual position multiplied by some gain factor.

Generally speaking proportional control is kind of ok, but depending on the disturbance pushing the controlled variable away from the setpoint, you will always have an error, since it is the error which creates the control output.  No error, equals no output.

This calculus belies a sharp need for love, simple.

On By cjx07sterIn UncategorizedLeave a comment

Ferodo slammed his left fist down on the table, his right was holding a diamond ring in his coat pocket, so tightly it was starting to hurt.  Now he decided it was too late to make his proposal, couldn’t possibly do that right now, not when Alice was fighting with him.  He had carefully calculated the day, the time, the scene, the location, and what on earth got into him that he had to invite one of Alice’s best friends along.  IT was just becoming a mess as usual.  He loved Alice, but never seemed able to let her know how his heart really felt.

He had graduated in Astronomy and his speciality, the solar system was as always pretty close to the top of his mind.  He had chosen this room, the Kepler room, because of the modern leather seats, coupled with the polished mahogany table.  Dinner here would be special, on the occasion of his graduation.  He had invited his two most special friends in the universe, Kate and Alice.  He had on hand some champagne called in for the occasion, courtesy his old man, a professor at the university itself.

Alice took the champagne, opened it, and poured some for all of them, the crystal glasses glinted in the light and after the wine was poured it just sat there, sparkling with no real purpose.

Kate sat there embarrassed, she had some colored paper from other presents given earlier in the day.  She asked Alice for some scissors, which she knew Alice always kept with her, along with tape measures and other things in that purse of hers. Kate started to cut all the different colored paper into squares and then slits.  This took a bit of time, but it kept her busy while Ferodo and Alice were fighting silently, patiently  like this.   After a while she started to assemble the squares of paper into a slightly spherical construction like a 30 sides polyhedron, made of colored paper.

It was Kepler who figured out that elliptical orbits were ok and our planets all had them, and that there was a calculus that could describe the ellipse based on the observed speed of the moving body.  That wonderful calculus like any belied the basic need he had to prove the love of God and the natural order of the universe.

Alice sat there, waiting, empty handed.  Kate gave her back the scissors.  So it was that they all sat there in a kind of sparkly threatening silence with the champagne poured.

  • Alice with the Scissors.
  • Kate with the Paper.
  • Ferodo with the Rock.

All in orbit around the table, and around the champagne, and around the real issue.

They all three understood their sharp need for love.

Simple

A Paper Diamond cut with Scissors

Notes:

Title attributed to Cait S. from Twitter @legerdenez,

Polyhedron Photo attributed to fdecomite from Flickr  – with permission

Calculus photo attributed to Peter Rosbjerg from Flickr – with permission

A love line in the sandy sky

On By cjx07sterIn UncategorizedLeave a comment
B72 Snake Nebula

It was getting late in the afternoon at the caravan park.  Tents flung all over the place, with spaces of grass and sand between them.  The beach not far away, flocks of seagulls tearing bits of food apart and squabbling as usual.  For most of the people there too, it was getting time to eat.

Alice was sitting on a rock, overlooking the ocean, and the waves.  Sunburnt a bit, she was munching on an apple, a nice red one and considering her palm, a mystery, but she had been told about love lines, marriage lines, heart lines.  It was mystery to her.  It was cooling down and so she got up and walked back to the tent on the beach, and met up with Ferodo, that infuriating guy boyfriend, whatever.

Alice and Ferodo took off up the track together.  Alice offered Ferodo a bite of her apple, and he took one, but was still thinking of fish and chips after all. He thought of holding hands perhaps.  Who would go first, the woman or the man in the equation ? They often thought about crossing the line, that marks the balance point in a relationship.  When tension increased, the strength and straightness of the line as well.  It appeared impassable sometimes, but other times it relaxed into a kind of curvature not starting or ending, but eminently crossable. Still, her hand was all sticky with apple.  Perhaps he would just kiss her instead.

“Ferodo !. Quick, look, what IS that ? ”

“Can’t see a thing mate !”,…  “where ?” he asked..

“Just there, you idiot !” “Look, It’s a snake!”  she said.

“Na, theres no snakes around here !, it’s the beach, don’t worry” he said.

“OK OK I see it !” he added.

There on the path in the darkening, was a curved black line in the sand,  the line was fixed in the sand but the front extended and the back contracted so that the line seemed to move forward in perfect formation.  It was a Taipan by the way, one of Australia’s most deadly snakes, a bit off track, and who knows where it had come from or why, but too dark to make it out clearly….

Alice screamed, “It is headed for that tent over there”. “quick kill it ! Or something !”

Ferodo, didn’t know too much about snakes.  He figured it was dangerous, and that he should take care, but as the light was fading was pretty sure he didn’t want to jump on it.

“Keep your eye on it, and don’t get too close !.  I’ll be back ” he said.

He quickly ran back to his own tent and looked around for a weapon.  There on the bed, where he had left it, was a hammer, perhaps that would do.  He snatched up the hammer and ran back to where Alice was following the snake up the path slowly but surely without deviation advancing on the lighted tent further on.

Ok, so with hammer in hand Ferodo looked at the snake saw that even though the snake was curved and snaking it’s way up the path, and even though he was kind of shaking all over, vibrating with adrenalin, and not knowing really if this was ok, he got the hammer in his hand.  His right hand. Should he use his left ? Wasn’t real sure, his mind started to optimise the situation, but then he realized he just had to go for  broke, forget the optimization.  If he had had a chance to pre-meditate killing the Taipan he certainly would not have chosen a hammer.

His right hand swung out, with the hammer at the smallish head moving in a dead straight line at constant velocity forward, slightly raised off the ground, and with the little minute tongue flicking the air occasionally.

Whack ! Smash, and then a violent eruption in the sand, of fury of the headless snake, whose head had clean come off all mashed on the end of the hammer.  The snake was thrashing around, and it was not clear it was dead, even though it’s head seemed to have come off.  Ferodo relived the last 200ms of it’s life to assure himself, that that was all he had to do.  He was shaking all over, possibly more than the snake itself.  He felt sick, like , way too much excitement that was unplanned and not part of expectations for this holiday.

Alice was standing there… ” what on earth !” she said, you could have got bitten ” what if you had missed the thing, you can hardly see it even now in this light”

Ferodo got his breath back, and said ” ok, ok but well, it’s dead now and at least it’s not going to get into the other people’s tent, whoever they are. ”

Alice and Ferodo looked at each other with a kind of new understanding.  The line had shifted in the sand between them.  Alice stepped forward to meet Ferodo, and stood with her foot clear on the still thrashing body of the snake.  She was standing there like it didn’t count anymore, with a half eaten apple,  and that there in front of her was another mystery to fathom.

After a while, the stars were coming out, as they turned, with apple and hammer in hand and walked off to get fish and chips.

Attribution : Featuring the Photo of the B2 snake nebula http://www.howardedin.com/wp/ creative commons.

The Internet : A Terrestrial Climate Controller ?

On By cjx07sterIn Automata, Innovation, Intelligence, UncategorizedLeave a comment

Global warming is a result of a set of complex feedback systems on a planetary scale. The earth has an extraordinary number in of feedback mechanisms and energy transfer systems that tend to balance energy storage worldwide, both in terms of oceanic heat, atmospheric heat and the heat in the more solid components of the earth.  It is a relatively closed system with not much coming in and out except perhaps energy from the sun, black body radiation to space.

Models have been developed to simulate and forecast the rise of the heat capacity and temperature of the earth and it’s systems, and the local effects on sea level, and great work of many scientists is starting to reveal the uncomfortable truth that the globe is warming, and we, humans might just be associated with it’s cause. What science now tells us is that global warming is big in scale and has time factors relating to centuries, or many generations, rather than one or even a fraction of a generation.

Let’s say we readers and all few billions of us on the planet know, that we have a causal relationship to the rate of warming, and that as the planet warms further, our children are likely to suffer on mass as a result.

This knowledge is enough for us to be concerned, but not enough to change our behaviour.  Our evolution is not that way inclined.  We tend to change behaviour based on experience, and generally only if we believe a change in behaviour results in a fairly immediate observable impact on our lives and the lives of those around us.

Global warming is big, its’ long term, and for human endeavour to try to change the outcome for the better, we would all need to act.  All people, towns, cities, states, countries, regions.

We have seen that classic governmental lines of control do not cause massive coordinated change in human behaviour worldwide.  However we have also seen that social networking is universal, carried by the internet, and does provide some means of at least coordinating thought in the right direction.

We have seen evidence of global coordination with the rise of ‘earth hour’ which now travels around the planet, country by country, one day a year to promote reduction of power.  The internet allows for this kind of coordination and action, whereby people can get some kind of feedback related to their behaviour.

Is it possible then, that with global internet availability, that this provides people with an opportunity to coordinate globally in terms of global requirements and resolutions.  That the internet would provide at least a mechanism to allow like minded people to gather global support for a particular urgent behaviour.

There is a new campaign to make an immediate behavioural change in Australia, for a carbon tax.  This is sponsored by a #sayyes campaign also as a tag on twitter.  It remains to be seen whether it can get enough steam to cause a revolution, but it is on the Internet, and anyone, Australian or otherwise could have a say.