Friday, December 30, 2011

11 Electronically Balanced Bicycles & Unicycles

"..The wheel consists of a ring of small rubber wheels overlapping a single large wheel. When the large wheel rotates, the U3-X moves forward or backward.."
Hundreds of years ago and approaching the Industrial Revolution, we had all sorts of genius and madmen tinkering with devices to propel an age of moving devices by virtue of mechanics. Plethora of gears, linkages and energy conversion schemes gave us the printing press, the mechanical wristwatch, the steam engine, the bicycle and calculators.

We're now quite deeply embedded in the Age of Electronics, where smart, sensible electronics in the form of boards, kits, controllers, sensors etc seem to be well within the affordability of average Joe. Has the age of invention really died? I argue not. Did you check next door?

Anyway...there is something existential in seeing a machine able to balance itself, isn't it? Well that's the topic for today.

Some years back while in college, I saw the murata boy riding his bicycle and smirked - that's it, the Japanese are going to take over the world. The motto behind the design effort was 'when you fall off a bicycle, get right back on' and so Murata Manufacturing packed gyro tilt angle sensors, power giving capacitors and other position sensing hardware into the robot to ride a bike. Two wheels.

To give company to the 'male' robot came an agile murata 'girl' and her stance was on one wheel saying 'ha, look at me' and out she came out more looking more heroic than her cousin balancing a unicycle while managing to avoid obstacles.

A video from Hacked Gadgets shows the impressive capabilities of the two creations.

The principles behind these electronics for basic work are not that hard to understand. And for an average guy to get his hands wet in application, you don't have to go far these days. LEGO has for a number of years been marketing the Mindstorms NXT kit which comes with a microprocessor, motors and several sensors to teach you motor control, object detection and so on.

Then if you listened to Cornell prof. Andy Ruina's wise words and had an itch to create, you could take that NXT to the next level :

Elsewhere, people were doing challenging work. The question probably was - could you extend this idea of robot-ism to humans and create a unicycle for propulsion? Dean Kaman's Segway seems to have inspired a string of inventors from all over the world to do exactly that.

The concept would be similar to the Segway - so you would take a chassis and mount an electronic gyroscope capable of measuring vertical angle. If you leaned far forward or back, an electronic motor controller would send a signal to the motor to rev it up or slow down so as to to put the bike back in balance.

The challenge would be to get your filtering right or you'll be leaning forwards and the sluggish machine would toss you off, or there would be introduction of positional errors, gyroscopic "drift" in your system and so on which would also not be good for tracking. Sampling rate is the other thing that's quite important. 100 Hz means sampling every .01 seconds, but on an electric unicycle, is that good enough?

An electrical engineer from Slovenia seemed to have got it right with his Enicycle. Works quite like a Segway and if you wanted to turn left or right, you simply put pressure on the left or right side footrests, then watched where you were going as the 1000 W motor raced the device to 15 kmph. A prototype was featured on the Gadget Show :

Perhaps Honda didn't want to run out of publicity as well and displayed the Honda U3-X, also a personal mobility electric unicycle, to a throng of reporters in Tokyo (2009-ish).

The uninteresting bit was, yeah they  had tilt sensors for balance control and so on. What really captivates is the portability of the machine - the bit looks like a sleek boombox and you can haul it around like a pullman. And then came the closely guarded "omnidirectional wheel" in the device.What was that?

A writer for the electronics journal IEEE described the legend of the wheel as such : 'The wheel consists of a ring of small rubber wheels overlapping a single large wheel. When the large wheel rotates, the U3-X moves forward or backward. When the small wheels rotate, the machine moves left or right. And when both the large and small wheels turn at the same time, the U3-X moves diagonally."   How does Honda come up with stuff like this?

So here's that video demonstration that Honda did for IEEE reporter in NY. Its a good one.

Focus Designs from Washington was probably inspired by the Enicycle to create something very similar - the SBU (self balancing unicycle).  Other than the fact that it costs 1400 cold cash, it can go 12 miles single charge with its 1000W motor and has the capacity for regenerative braking, something I'll have to look more into to assess its potential. (In the past, I wrote a post looking into the regenerative capabilities of MIT's Copenhagen Wheel)

Stephen Boyer, a computer science student at MIT also flexed his creative muscles to see what he can come up with. He validates the fact that anyone these days with decent electronics knowledge can make a forward-backward balancing unicycle. He didn't complete his project since he was unsuccessful at sideways balancing but he's brought some fresh ideas into the picture, like a pressure actuated killswitch that the rider would hold in his hand to kill the machine. Lots more interesting details into the engineering of his "Bullet" and a video of Stephen riding that bike can be found on his blog entry.

Steve Jobs may have passed on with a final look at an iPhone. And Segway's owner J. Heselden may have met his end over a cliff riding a Segway. But these individuals and technologies inspire hundreds of derivative technologies daily. But some part of me wants to see progress from investigative tinkering.

I can't wait for the day when the local pizza joint dishes away with their automobiles and hires a Murata Girl to deliver my pizza. Boy, I think if Google cars can drive around Nevada for 200,000 miles without a single accident, perhaps robots on electric unicycles can do a better job of delivering pizza without fatality. I mean, I do think of how many kittens were killed in the process of getting my pizza, you know.

Happy new year! Here's hoping we see more interesting things in 2012.

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  1. Lauren8:20 PM

    Happy new year Ron!

  2. Anonymous2:05 AM

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  3. Happy New Year to you, too, Ron!

  4. I have no link to the individual, but my uncle met a guy on a DART (Dallas area rapid transit) electric train carrying a home built self-balancing unicycle. Instead of sitting on a seat, the device had a broomstick handle and the rider stood on footpegs. This was a year or two ago. The rider said his machine used a wheelchair motor for propulsion and a nintendo wii controllers for balance/motion sensing. Like the MIT student, there was only front-back stabilizing.

    The newest iPhone has impressive tilt sensing abilities. I have heard of them being used to set car wheel alignment. I wonder if it would be enough to balance a unicycle?

  5. Hey Ron, you know what works better then one wheel? Two weels, you can use one for propulsion and the other for steering.

  6. BLondon - Very cool. Do throw us a link if you find something about this bike on the interwebs.

  7. The U3-X from Honda is amazing. Were can I buy one and will I have to remortgage my house to do so?

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