   John Dingley email: self-balancing-skateboard@sky.com
Recent updates:
October 2010: Link (15) shows my attempt to give twin wheeler more "feel" by making it steer using pressure sensors under the griptape
March 2011 New version of economy build arduino twin wheel board
Took to Maker Faire UK 2011. So much RF noise my wireless control did not work so had to revert to cable hand controller.
March 19th 2011: Have just appeared on the New Scientist TV channel!
Next project May 2011: Building a Unicycle....see link 17 on left menu
May 24th 2011: Some video of me talking to Jon Bentley with the skateboard at the 2011 UK Makerfaire has just appeared on the "Gadget Show" Click here
June 24th 2011: Building new twin wheeled compact board with proper pneumatic tyres. Uses lessons learned from all previous machines.
MakerFaire March 2011 video above showing twin wheeler in action. This machine has solid polypropylene wheels and batteries in the deck. Works well, not so good on rough surfaces though.
This one has pneumatic tyres, axle line runs through centre of the deck, steered using pressure sensors under right foot and can be run without any form of hand controller (at last). Will update this video with a better one soon.
LATEST PROJECT
TWIN WHEELED BOARD WITH PNEUMATIC TYRES.
TAKING THIS TO MINI-MAKERFAIRE BRIGHTON UK 3rd September 2011
Previous twin wheeler has e-bike battery in deck. Could ride this all day and it would still show 3/4 battery charge, therefore had excessive battery capacity.
Objectives / improvements for this machine are to make it more like the "i-slide" concept but better. Uses all lessons learned from previous machines:
- Smaller NiMH batteries from RC cars. If need more range - exchange batteries.
- Batteries easy to remove and swap over.
- Must have pneumatic tyres for better ride on non-smooth surfaces.
- Extremely compact design for all the mechanicals
- Symmetrical profile, could ride it either way up. This makes frame much harder to design.
- Integrated carry handle
- Reliable hard wired Nunchuck steering / trim control.
No way I could do this bolting metal sections together. This one is going to need a LOT of cutting and welding.
    Very short chains and motors mounted very close to centre axle line. Getting all this geometry just right was really tricky. Chain clearances are about 2mm in places.
- Pneumatic tyre/wheel/sprocket combination is from a Razor E200 electric scooter replacement rear wheel set.
- These seem to come with 2 potential sizes of sprocket, it looks as if later models had bigger wheel sprocket for lower top speed but more torque. I am using the one with the larger sprocket.
- The drum brake mechanism has been removed from each wheel.
- The alloy holding this mechanism has been sawn off (making sure wheel bearing not damaged) and axle for each wheel has been shortened.
- Axle fixed rigidly at inner end on frame which is why the outer axle mount does not take any side-to-side loads and can be made of flat steel - it only has to carry vertical load.
Plenty of free space in the other end of the frame for future electronics:
Compass module? GPS? LCD display perhaps. Thinking of putting Sharp downward looking infra-red range finders in each end to measure distance to ground. This would make board automatically adjust its "trim" so if for example going up or down a slope, each end would stay same (i.e. equal) distance from the ground for a more natural ride.
Also in previous machines with wheels underneath deck, when deck tips, this moves the wheels off the centre-line, so motors have to do more work to bring deck level. Now the axles are in centre line (rather than under it), then if board tips, wheels are still closer to being under the rider, i.e. not pushed off to one side, so perhaps overall power consumption may go down a little.
 All 4 led's flash at startup, they then all go out apart from LED4 to show it is now OK for you to stand on it (i.e. after gyros have zeroed themselves), and that the power is still on. i) You now tilt it level for first time. When it comes level for first time, the self balancing algorithm goes active. Board is mushy underfoot for a few seconds then "tightens up" to stop initial reflex urge of rider to correct what the board is doing (the "soft-start").
ii) A reading is taken from each pressure sensor under hell/toe of right foot and this becomes set as the normal mid-position setting, i.e. when you want to go straight on and not turn.
iii) The middle 2 LED's now light up when you are going straight ahead.
iv) If you lean back with right foot, the 2 LED's on the same side of board that your heels are on light up.
If you lean forwards onto toes, the 2 LED's on same side of the board as your toes light up.
This allows you to learn how board is reacting to the pressure of your right foot heel and toe on the pressure sensors, in terms of steering.
v) If you roll right foot over to one side (you cannot just start to lift it off else board would tip left side down and shoot off to the left): no pressure on either pressure sensor, deadman is activated, motors are cut. "Countdown" starts - if you put foot back on within about 1 second, motors will restart (i.e. it gives you a slight chance to recover the situation), if not, then deadman switch is permanently engaged, all LED's go out, and you will have to reset board from scratch.
ORIGINAL ONE WHEELED SKATEBOARD AND MACHINES THAT DEVELOPED FROM IT ARE BELOW.
MUCH MORE INFO ON EACH VARIATION CAN BE FOUND USING THE LINKS ON LEFT HAND MARGIN
CARBON PANELLED TWIN WHEEL VERSION May 2010
Here in the 3 images below is the version seen in the video above, completely rebuilt (May 2010) using as many carbon fibre honeycomb sandwich composite panels as possible (shorter, more rounded ends, lighter). More pics of this on links menu on left.
  Carbon fibre self balancing skateboard 3
TWIN WHEELER BEFORE CARBON REBUILD 2009
 The deck of the twin wheeler is essentially one large but thin e-bike LiFePO4 battery.
Video of several self balancers in action at a carnival July 2010 (Cowley Road Carnival, Oxford, UK). Includes one and twin wheeled boards plus the new stand up scooter.
EASY-BUILD SKATEBOARD VERSION (March 2010)
Below is the stripped down easy-build self-balancing platform, make into whatever you like, skateboard, segway clone, R2D2 etc. I built this version after makerfaire. Video and photos below.
Instructions for ths relatively-easy-build machine are also now on Instructables.com here:
 EASY-BUILD VERSION VIDEO.
EASY-BUILD SKATEBOARD VERSION (video above).
The plan:
-Arduino based as low cost plus many forums to help you.
-No welding required. All hardware can come from store such as "B and Q" just need a drill, saw, nuts and bolts, spanners.
-Commercial motor controller, no point skimping on this.
-Ebay electric scooter motors.
-Electric scooter wheels/sprockets
-Everything bolts up onto a wooden flat square to form a self contained self-balancing module. Wheels can be close together for a skateboard or wide for a Segway type build.
-User can bolt anything they like to the top of the self-balancing module i.e. a skateboard deck
-User supplies whatever batteries they can afford starting with a couple of lead-acids on top of the centre of the deck as the lowest cost starting option.
- Accel and gyrosx2 all in one module from Sparkfun. Lowest cost one in their range is used. Has anyone else built one of these twin wheelers since I posted the Instructable?
Oh yes! Ages currently range from 12yrs to 81yrs. This Instructable is over a year old now, so yes indeed, people have. Here are a few I know of: 1) Skateboard: http://www.youtube.com/watch?v=kSW7YXLCjqk 2) Skateboard: http://www.youtube.com/watch?v=u-uUidBZEnM 3) The Velociryder: http://www.youtube.com/watch?v=xvfUIxusPZw&feature=player_embedded 4) Great board video - Buffalo State College senior project: http://www.youtube.com/watch?v=FEaTxahyQxc
5) Another board based on this Instructable: http://www.youtube.com/watch?v=vhbH_AmIKZA&feature=related
6) A board based on old FIRST robotics parts + code from this instructable (FIRST robotics was started by Dean Kamen who also invented the Segway, to encourage youth to get interested in engineering): http://www.youtube.com/watch?v=Vh9LpNQ_S0k&feature=related 7) Carbon fiber racing car seat with 2 wheels also based on this instructable - the SciChair: http://www.youtube.com/watch?v=ZJMY70P1lEk
8) Carey's self-balancing platform, good video: http://www.youtube.com/watch?v=ngMJcxeB7og |
   (Brown County Democrat, December 28, 1900.) - The "Footomobile" of the future!
 With thanks to the inspirational webpages of Ben Smithers, Trevor Blackwell and many others (see links page on left hand sidebar).
Why do this?
- Initially to teach myself microcontroller programming and for the sheer technical challenge of it.
- Most things have been invented. Although the self-balancing skateboard concept has also already been invented, developing an intuitive, easy to ride, compact, practical machine is a really tough challenge requiring good old fashioned building and practical experimentation. Cannot just do all this on a computer design package.
- If you look at the truth of "innovation" there are rarely Eureka moments. Usually they involve reading all around a subject, long periods of experimentation and slow incremental development into a workable device. This is what I am doing here. For example mp3 players existed long before the iPod came out. Edison made the first practical light bulb, but not the first ever light bulb.
- My first effort in 2008 was big and clumsy but it worked. Have been improving the designs ever since!
24/6/2011
The i-slide. This was a computer design study never built as working machine as far as I know
 My aim is to get to a machine about this size but twin-wheeled, a tricky packaging challenge. This project works and balances. Motor covers above and below deck still need to be made. Whole frame needs paint and tidying but all the main design elements work.
Motors have been brought in really tight into centre of frame. This means they can be in same horizontal plane as the wheels, they won't hit ground when tipped and in theory at least the board could be ridden either way up, i.e. board is symmetrical when seen from side, the wheels have not just been bolted up from underneath.
   Batteries are 12V each pack, two packs, 3.7 Amp h for R/C cars. They slide into a rectangular box section in the frame from each end so can easily be replaced without any dismantling of frame. Box section protects batteries completely. They can supply up to 40 amps in short bursts so may not last that long in terms of endurance but should be powerful enough to run the machine.
 Batteries slide in.
 Despite large wheels, ride height is same as the height of axle line from ground, about 10cm. If moving along and hit small obstruction, board less likely to violently tip as centre of lateral momentum is through the axle line.
   July 22, 2011: I have obtained 2 of the new(ish) 1 inch diameter FlexiForce variable resistance pressure sensors. These measure pressure under heel and toe of right foot and will enable board to be steered by leaning, more like a real skateboard. By rolling whole foot to right (so not pressing either sensor) this will cut power to motors and act as the "deadman" switch. If this all works OK I can finally get rid of the hand-held deadman switch /steering controller. It is nearly there, just a case of improving the software a little more.
EARLY MONOWHEEL (2008)
Big and heavy but it balanced - 3m to get to that point. 4 potentiometers in hand controller to adjust all variables in balance algorithm while riding it.
MONOWHEEL (2009)
Redesign with flat wooden deck. Simpler hand controller.
ONE WHEELED FORWARD FACING SCOOTER
Would the "ORBIS" design have actually worked? Well this is an attempt to find out!
Link to the ORBIS design study: Click Here
SCOOTER REBUILD Sept 2010 as the "THING"
 Verdict: It works but it is heavy and slow. I may rebuild it into something else.
AUGUST 2010: Self balancing scooter built into a small rucksack
 Small front wheels are airborne when self-balancing.
 Idea was for something you could actually carry around and use.
Development of all the original monowheel versions has now been moved to link 16 on left hand menu. |
