The first build: Slider v01

slider disassembly
To set off my research in a hands-on fashion, I am building a system that enables a haptic connection between two (or more people). The system consists of modules each containing a motorfader, where each motorfader tries to follow the position of the other. Central idea of this system is that action and (haptic) feedback is collocated. (ref. Wensveen)(expand with theory?: Lenay, Deckers, Gibson, Merleau-Ponty)

The goal at the outset of this building project on the one hand is to learn new and hone existing tinkering and prototyping skills, on the other hand it is to literally get a feel for what it means to create a haptic connection between two and more people and to explore the feel of different variables in that connection, e.g. elasticity/firmness, friction. time-delay.

To some extent this system echoes inTouch, a classic tangible interaction system built by Scott Brave, Andrew Dahley, and Professor Hiroshi Ishii of the Tangible Media group, MIT Media Lab.

(more details after the jump)

First Build
Here’s a foggy intro video to this work in progress…

The system in this video runs on a quickly hacked together way of getting one slider to follow the other.

Initial version consists of 2 motorfaders controlled by one Arduino-uno (through an H-bridge).

The motorfaders are built into rectangular boxes. A 10mm diameter bead is fixed to the handle of the fader and placed under a funky 3d-weave fabric in such a way that the moving bead is only visible as a small bump in the fabric surface. These slider boxes resemble somewhat the screen of an old fashioned CRT TV.

Specs:
controller: Arduino Uno
H-bridge: L298N
motorfaders: ALPS RSA0N11M9 10k Lin
Vin(motors)=12Vdc

The circuit:

circuit diagram of Arduino Uno, l298 and 2 ALPS motorfaders

slider v001

You can view/get the Arduino code I wrote for this here. Any comments welcome….

So What?
It does something! You can feel it in one slider if the other is moved.
Control loop speed:
The system is rather noisy -as in- it makes a lot of noise, probably from the speed of the control loop (if no serial output is sent to processing) the program does a loop in approx. 750µs.
The haptic feedback feels rather gritty, for the same reasons that the system is noisy
Power/Force:
The motors of the sliders are powere with 12Vdc (though rated at 10Vdc, 600mA for  max 10 secs (stalled), this results in approx. 2 N of force (very rough measurement).
The force is definitely tangible, but it is to little force to be able to really play with the feedback between people.
Result:
My preliminary conclusion is that the combination of the speed of the position control loop now has to be tuned to a a spongy feel: the power of the motors is tapered-off proportional to the distance of the slider to its setpoint. With a higher ‘sample rate’ and thus control rate of the feedback-control loop, the gritty feel and audible noise would be of a higher frequency, but also, the spongy feel would be less, because the tapering off of the power could be across a shorter range.
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