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17th december 2008 Demo IV : Swiitboard magic carpet

Swiitboard magic carpet ride.. Using GlovePie and Google Earth (and a little practice) the board can be used to fly using the Google Earht flight simulator..

The Swiitboard (Footwii/Pedal navigation device)

Hello to my Swiitboard page. I will explain a little about my project. You can find videos and info on the why and how and attain the source code. I put a disclaimer up for nonsense and technical errors, I'm pragmatic ;-).
I have been playing my self made games for a week now, and it really is a good workout, without the usual wear I get from running on hard ground. It is somewhat addictive, and I find the (sometimes quick) balancing of my body during the games also improves overall muscle tone (don't know how to say it any differently).

How it started

First: If you happen to know how to unlock the nunchuck using pywiiuse, please send me some sample code. I have the code, but the values remain zero.
I wondered about a way to get fitter, work out without having to go running outside (although that is very healthy). I didn't think the Wii balance board would do the trick, as the Wii games where reported not to be very intense, and the board itself is to hard for running on it. So what is different about the Swiiboard is that can absorb running effort, measure the effort and perhaps that it can use those measurements to control a virtual environment. It turned out this can be achieved using a Wiimote controller.

The Wiimote

The Wiimote is a bluetooth device (usually) transmitting its data to the Wii console. The data includes 3 axis acceleration, orientation, IR camera data and button input. However, you don't need the console to use the Wiimote. It can be paired with PCs and there is a whole selection of game control options using f.i. glovepie.

Bluetooth

Because the Wiimote has special data on offer you need the newest bluetooth drivers. Bluesoleil offers an update if yours can't capture the accelerometers (test with the software found here).

The interface

The way the Wiimote is used is trictly to measure the impact on the ground you run on. It is attached to a strong wooden plank resting on top of polyethylene absorbers/coushions. Check out the video below. I use a softer and a harder type of absorber to allow for smooth acceleration and a light start. The movements of the plank have some inertia, and this may reduce the stress on the wiimote a little, although it can probably take a lot more abuse.

The software I

There are several wrappers and libraries for accessing the Wiimote. Not all of them work equally well, one f.i. specializes in the Wiimote IR capabilities and the other on the buttons. In the end I settled for PyWiiuse, which seems to have underdeveloped IR functions, but has the accelerometry down. I though I needed IR at first to get a good direction reading. This would be easy if you put two burning candles in front of the board, and measure the height difference between two tracked dots. Because I couldn't figure out how to access the IR tracking I had to find another way to get what I need only from the accelerometers.

The measurement

As you run on the board the Wiimote moves up and down. This generates gforce and orientation signals all over the place. Not all data is usefull, and it seems there is quite some signal processing going on in the console. After some testing and graphing I found that only using the Roll input gave me all the data I need.

The steps

Roll gives a nice readout with every step. You can see it in the Wii Workout video below. The energy expended is in the area below the line graph (see picture). By summing all the readings (thus calculating the area) I measure something I call the 'effort'. It is shown on the right side in green. In white you see time. Notice the Wiimote never realy rolls because it is attached to the board.

The direction

The direction is derived by processing an input called gforce.x . If you hold the Wiimote in your hand it measures something like roll, but only acceleration. The values are positive in both directions. I found it will however go negative or positive dependent on the roll orientation, albeit in a very noisy way. It needs calibration at the start. I used moving window averaging to smooth it out.

What to do next

I created several programs to use the Footwii/Swiitboard. The first above simple measures the energy you put into the absorbers/coushions. Using the direction sensing allows for more emmersive applications. Below some movies of my prototype 3d treeworld. If you are a hardcore programmer you may be able to write a glovepie script so you can run though Wold of Warcraft.
I am working on an IR 'sword' or wand by directing the IR viewangle upwards. This may be easier with a Nunchuck, although it lacks absolute postition (and I don't have one).

Demo I : Big screen

I tried the board with a backprojection screen. I will be able to use another Wiimote in a few days to further interact with the game. Below video als shows how the coushions absorb the movements. The exercize is in between running and cycling. The game set to catch 25 balls is like jogging 15 minutes.

Demo II : No IR use yet, but..

Demo III : Swiitboard soccer

A first stab at soccer.. It is very intuitive, although it is easy to sun past the ball. It takes the direction at the time of contact, and feels somewhat like a combination of jogging and putting (golf).

Calories burned

If someone knows how to calculate the calories burned from the Swiitboard please send your suggestion. A first stab would be to assume stepping on it is like lifting your body weight in the opposite direction. That would make the distance the downstroke. After the downstroke is absorbed that energy is spend. According to the dutch wikipedia the energy to lift a 102 gram apple 1 meter is 1 joule. So if you weigh 80 Kg (like me), it would be 39 joule for 5 cm (the average stroke lets say). Doing this a number of times per second gives the number of Watts dissipated. With 0.7 steps/second this would result in energy used of 27 Watts translating into 1416 Kcal per hour (0.01433 Kcal/W/min), which seems much to high, (please send your opinion). Approaching it from another angle: The exercise is like jogging so we should expect spending 560 Kcal per hour (for an 80 kg person). This translates back to about 0,10 Kcal per step. A calorie expense dial is something to add..

The software II

Now you may be interested in the software and setup info. I will send it to you if you donate 10 euro here, it is for my website dedicated to climate change, Climatebabes.com

The package

Swiiboard Kit