Friday 9 September 2011

Grounding Research - The Presentation...

setting the scene.... stories from the bush....

rainbow serpent festival : a hotbed of experimental art and aesthetic

Robin Mutoid - Australia's anti hero - recycling & repurposing waste into  art & machine



look how far to carry the esky!!




some other examples out there.... simple, effective and functional..

this is the esky in question... 12v low amps compressor portable fridge... only 45$au!

the power train :) ford Laser wiper motors

The big, greasy box of parts.... no two of which are the same...



loyal, reliable and trustworthy.... a true friend!

Ideation: Some alternative ideas...The presentation

a.k.a "some alternative ideas"

#1....

lots of people watching movies / music on laptop, sub-optimal conditions...

why on earth would we bother???

a solution using head tracking.... and consumer parts

-failed because it was before its time, proprietary equipment and hideously expensive..


Reclaim the lanes festival... bringing it all together with radio transmitters/recievers.... communities as community..

idea #2...... 

the concepts of neuro-feedback - real designer drugs!

The technical.... NeuroSky headset~ 300$us

the possibilities.... (see original paper for references)


So its not all about the beer ;)

Preliminary Construction Sketches (will be revisited and refined)

How on earth to track a human?

Improving on a classic design? by having a large conveyor surface area the machine could go anywhere!

Friday 2 September 2011

Grounding Research: Synthesis of Vex Design Principles

As previously promised, here is a synthesis of the Vex Inventors Guide - a basic, clear and concise introduction to the relevant engineering principles for robotics. The forum is a wealth of information also...

Apologies for the point form and brevity... but there is a lot of information in those pages, and to expand on everything would take way too much space...



>> structural
  •   rigidity
  •   centre of gravity (low and over "support polygon" pp. 2-33!)
    • weight of batteries + motors + chassis + tracks
    • weight of payload (ie carton of beer+ice)
  •  safety, bumpers etc to stop injury..
  •  stress / torsional forces / mounting points / material data sheets
    • bracing
    • suspension
  • exposure + vulnerability
Subsystem interactions:  
    
structural - motion 
  • needs to be codesigned, integrated for strength + support for integrals (motor, payload, batteries) 
  • handle rough, uneven terrain

structural - power
  • protect batteries, weight distribution  / centre of grave

structural - sensor
  • mounting and stabilising role
  • correct positioning for sensor tot work

structural - control
  • mounting and protection
  • antennae / rf shielding / range / reception

structural - logic
  • mount and protect (esp impact and h20)
  • wiring loom / connections robust and secure

               
>> motion:
  • speed vs torque
    • gearing / complexity / reliability / access to repair / maintain
    • drive gear / idler / compound gear / ratios 
  • materials for construction / durability
  • non gear, belt is better when motor and wheel is far apart
  • servo/pwm vs dc/h-bridge
    • build vs buy h-bridge or integrated chip
  • current draw (for batteries life and for motor controller integration
  • lasercut parts from cad? http://www.viz.tamu.edu/courses/tutorials/hunter/presentation1.htm
  • wheel size vs acceleration (smaller wheels = more torque)
    • stop / start of natural human gait, esp at party
    • safety, quick stop
    • more revs for regen braking etc
    • size for negotiation over obstacles (rocks, tussocks, hills)
    • clutch / stall protection (natural slip of belt?)
  • increase number of motors = cheap torque boost, but calibration..>?


motion - control - power subsystem interactions:

  • integrated microcontroller / h - bridge (sabretooth or robot claw)
    • regenerative braking / decelleration
    • regulated +5v dc for microprocessor power / protection
    • capacity / current handling capability of system matched



>> power
  • capacity + 20% (heavy contraption, never want to have to carry this beast)
  • discharge rates at full load / no load of motor / estimated Amp Hours (AH)
  • good metering / indication of low current / overcorrect  / regulation
    • possibilities of extending this with software control (similar to laptop power schemes, perhaps hack a laptop power monitor?)
  • li/po or deep cycle or motorcycle or scooter
    • shallow discharge = voltage drop
  • 5-12v or 24v (ohms law, high current/low voltage needs expensive copper) 
    • series / parallel benefits
  • ecology / green benefits of regenerative decelleration far outweighs the step outside the 'budget' construction
  • temperature 
    • batteries location within chassis 
    • heatsinking / fan for conroller


>> sensor
    eyes & ears, detect salient / important features of environment
  • reliability across all conditions expected
    • negative obstacles! cliffs, ditches
  • distance of operation / pickup polar patterns
  • analog / digital
    • analog is difficult to maintain constant / specific signal
    • digital is better for electrically 'noisy' conditions, but just hi/lo
    • combination / backup systems with different types of sensors to alleviate specific weaknesses
  • Tracking options...
    • IR proximity (pros n cons)
      • PWM for data coding (like IR remote control)
    • ultrasonic prox (see MaxBotix)
    • visibile light proximity http://letsmakerobots.com/node/1833
    • gps
      • accuracy? cheap options not hi res/fast enough updates...
    • rfid
      • signal strength (rough n ready!)
    • line detector concepts (hi/low or pattern detect ilke MS surface)
    • kinect depth mapping correlated to other sensor data (overkill, but interesting for future platforms? requires atx-mini-pc? robustness for doof?)
    • kinect mic array / positional audio capabilities (great for vox commands, could even incorporate similar tech to blob tracking code to reduce noise / predict direction)



 structure subsystem needs to accommodate all sensors
  • mount points
  • optimal operating range / dispersion / position
  • microcontroller / microprocessor handles regulated power supply (i.e BEC +5vDC supply from motor speed controllerr
  • perhaps hardwired bumper switch disconnects motors without microprocessor control for safety backup?
logic system requires cleanest data possible, with minimal processing time to make decisions quickly and accurately (necessary for following human)
audio recognition will require perhaps noise reduction / telstra technology ;)
control system will need backup (perhaps ability of manual operation in case of sensor subsystem failure) 
feedback (visual) from sensors and actuators integrated into aesthetics, but very useful for debug / troubleshooting, esp when 'back to nature' or out bush...




*phew*
-&c

Thursday 1 September 2011

Grounding Research: Delving deeper into the machines...

Aw man, ya know i almost completely forgot to mention the afternoon i spent out west with my backpack full of tools in the westie supermarket (again, winks at Andy) known as Pick'n'Payless auto recyclers...

so i'm there, in the eve-of-the-first-day-of-spring sweating under my load of tools, climbing under the hoods of rusty and mangled cars.  Wish i had my camera, as there was so many stories there of death and destruction at high speeds... so many twisted wrecked dreams and [hopefully not] lives...

anyway... after walking the whole yard and poking around looking at the various mechanical parts and linkages, i find two identical timing cases with the perfect setup... the photo on the right is what a timing case looks like out of an engine...


However the problem i had, was all thousand of these beauties in front of me were securely buried deep in the engine and require lifting it out to get to them... all i could ever get to was a tantalising glimpse of the cogs and some beautiful belts.... but never extract them.

on the way out i tripped over two big crankshafts with the timing gear still attached... grabbing them, i dashed the hundreds of meters left to the exit and presented them with glee to the guy at the desk.. who laughed, (as i was later to find out that these parts are usually rubbish), and tried to charge me 89$au!

This was well outside the budget so i had to swallow my pride and leave empty, but greasy handed... the twenty or so engine reconditioners i visited on the way back were a real lesson in the extremes of humanity... of special special note was two individuals / small businesses - one in a mobility scooter shop (Sydney Scooter and Age Care) who went out of his way (after i told him about the idea) to try find me some super-motors, and dis-assembling half the scooters in the shop, and even pulling out his iPhone to show me all the diy projects he had done over the years :)


the other owned a engine reconditioning and machine shop by the glorious name of Unlimited Head Jobs in Ashfield.  Props to this man, a very tidy workshop, he was really interested in the robotics also and had a bucket of old parts there he just gave to me...

THANK YOU BOTH FROM THE BOTTOM OF MY HEART! YOUR CONVERSATION AND COMPANY MADE MY DAY



Show ya the best bits later ;) ....

Grounding Research: Delving into the archives..

Hmm, so i'm going to try collate the various images ideas and research (with regards to the tracked-base) i have so far over the next few posts... Bear with me as i shake the bookmarks and text files into a shape fit for public consumption ;)

The basic idea is (as previously mentioned) to create a high-payload tracked mobility platform that can (for the moment) be controlled via remote or wii nunchuck...

[you can read that last paragraph as: tank base]...

Initial ideas of lasercutting a slick chassis and parts out of aluminium were dashed when i discovered at school we don't lasercut much but ultrathin perspex and timber laminates :(

There goes the hopes of upscaling my little Tamiya track kit in 3d CAD and printing parts....



So, in keeping with my passion for recycled and low budget, we are going to hack one up at home.  First port of call was downloading the VEX inventors guide and reading cover to cover the engineering notes - especially the really valuable theory on structure, motion, control, power and sensors... i really learnt a lot from this, so will save the discourse for another post...
Another great site for beginners mechanics and engineering is Rob Ives...

From here i managed to find a number of really interesting (and not-so-interesting) war and tank-specific documentaries (probably copyright, so i won't link them here), which i devoured in a sunny afternoon... One of the main points i took from this was the different approaches and pros and cons of the historical decisions made. For example, the beautifully engineered German Tiger tanks cost so much and took so long to build - rapidly got destroyed by the cheaper, faster and much more plentiful Russian T34's due to sheer numbers!  Just goes to show there's nothing wrong with a functional backyard job !

the over-engineered German Tiger


The quick-and-lethal Russian
 vs


Seeing these documentaries and the historical development of the tank over the years, I started to delve into the various track systems, and even contemplated making a 3d CAD model to perhaps try lasercut in rubber...

One design stood out amongst the crowd of DIY... the 'plagiarism tank' ... This is exactly the chassis design i had in mind, simplicity plus.  Here is something i can build at home, with minimal tools and time...It will be made to the dimensions of the esky...



The track system and power train is still under research, however i got lucky the other day and scored 2 Ford Laser wiper motors for $10 out west.  These beauties have a low rpm (~40 by my rough count)...and options for a few different wiring schemes affording different voltage/torque/rpm's depending on which of the 5 pins are used.

Another entirely monstrous score from the west (thanks for the hint, Andy ;) was the purchase of a 12v/240v portable fridge! and better than the crappy peltier element that i was thinking about, this Rig has the old-skool, much more efficient compressor... only issue i can see with it is it 's slightly larger than i hoped, and slightly more top heavy (due to the compressor and circuitry mounted in the lid...... Upside is, it's nice and wide, so the centre of gravity should still sit quite low, especially when loaded with cold beers :)

Grounding Research: An alternative proposition...

Listening to the class' great ideas today i was inspired... Of special note here is Luke's bio-feedback mood lamp.

This got me thinking about an old idea i had a few years ago... a presentation i called "Getting High on Your Own Supply".

The basic premise of this idea began with a simple neurofeedback loop between a generative music algorithm ('the machine') and the user (via e.e.g.)... the idea is that after entrainment, and using a bio-feedback loop, the machine should be able to recursively hone in on the sounds / environs makes the user 'happy' or 'content'... whilst moving further and further away from those combinations of sounds that do not...

This is effectively leading to the point where the user effortlessly is tailoring the auditory environment to his or her taste, and hopefully eventually towards stimulation of the musically responsive reward centers in the brain to release dopamine and serotonin and other endorphins.

Here is a link to the paper i wrote back in 2009.... and the associated keynote... have to dl&unzip the archive... sorry if its a little dry and technical, but i think it explains the ideas and a bit of history better than i can do here...


With the cost of these low-channel count e.e.g's falling dramatically recently, it stands that the units with a reasonable channel count should not be far behind... This would enable this idea to be developed further, and perhaps even realised? 

check out Emotiv Systems for details of such a unit, and the incredible  Tan Le on ted.com for a (rather dated now) demonstration...