Using multiple IMUs for sensing deformation

I made this video today to quickly document some work I’ve been doing using multiple inertial measurement units (IMUs) for tracking the orientation, bending, and twisting of deformable objects. Intertial measurement units generally contain 3-axis accelerometers, gyroscopes, and magnetometers – the data can be cleverly combined to obtain an estimate of orientation (as long as the IMU is being used in an environment with constant gravity and magnetic field, and not in free-fall).

This particular object has two Mongoose IMUs embedded inside it, running some custom firmware I wrote for complementary filtering/sensor fusion for estimation of orientation.

Introducing the MiniBee

is a small, arduino-like circuit board I designed for the SenseStage project, a collaboration between the IDMIL and Chris Salter‘s lab at Concordia University. The boards include the footprint for a XBee mesh-networking wireless transceiver, creating compact, low-cost sensing nodes which we are now using for investigating ubiquitous computing in the media arts.

The first batch of 100 MiniBee Rev.A boards have been manufactured, assembled and tested 🙂

SensorWiki 2.0

After quite a lot of fiddling around I finally finished porting the SensorWiki.org website from its old MediaWiki version to the new DokuWiki version. This afternoon we pulled the switch and it’s working almost perfectly (except for some new user registration issues to be worked out later). The old version was spammed daily, but it should be much more manageable now 🙂

Live@CIRMMT – Steven Schick

Last Wednesday I was involved with another concert: Pieces for solo percussion and live electronics performed by UCSD’s Steven Schick. This amazing performance was part of the Live@CIRMMT performance series, and also has another connection to the IDMIL and me. One of the pieces performed was Chatter/Clatter, part of composer Roger Reynolds‘ Sanctuary Project, which was initially workshopped in the IDMIL as part of a project exploring gesture control of sound spatialization. We developed a sensing system using piezo-electric contact microphones on the percussionist’s fingertips, a technique which is now used in the piece.

I also drove the computer for this performance, which was running software in Pure Data (pd) which handled  processing of the live sound and 12-channel sound spatialization.

Mango sensors

During my endless search for digital compasses for use in a current project, I recently found a reference to an entirely original technique for sensing direction:

The discrete sensing elements employed in such sensor modules are generally called magnetometers and/or mango-inductive sensors.

(emphasis mine) I guess it senses the Earth’s mangetic field 😉

Seriously though, good/cheap/fast digital compasses are hard to find – I’ve been playing around with the Robot Electronics CMPS03, but it’s crazy power-hungry and not tilt-compensated. I’ve got some Honeywell HMC6343’s with breakout boards on the way, but the datasheet says they max out at 10Hz. I’ll probably just use accelerometers for fast movements, and calibrate continuously to the slower compass.