This MIT Project Tracks Movement in 3D Space Using Magnets

Tracking movement in three-dimensional space is incredibly useful, and has applications in a number of industries. Devices like Microsoft’s Kinect have proven its usefulness in gaming, motion capture has been a major development in CGI, and it can even be useful in medicine and fitness. There are many technological means to accomplish that tracking, but they all have their pros and cons. Filmmaking-style motion capture, for example, requires serious camera setups and a lot of processing, and is completely impractical for something like a home computer interface. Researchers from the MIT Media Lab have recently developed a small, portable tracking system that relies on magnets.

Permanent magnets, as the name suggests, always produce a magnetic field. Those magnetic fields can be detected and used to track the magnets as they move. This principle isn’t new, and has been used for several decades. In the 1950s, for example, doctors were able to track ingestible magnet pills as they moved through a patient’s body. But that was the sort of movement that happened slowly over the course of days. The kinds of applications where magnetic tracking today, such as controlling virtual reality gestures, needs to happen much more quickly— a challenge that has been difficult to overcome until now.

To tackle that challenge, the MIT research team used everyday hardware combined with clever mathematical algorithms. The hardware was an Apple Macbook Air from early 2014 with modest specifications, a Teensy 3.6 board, and an array of 16 STMicroelectronics LSM9DS1 iNEMO inertial modules connected via I2C. Those modules can detect the presence of a magnetic field, and the direction it is. To actually track the magnets, they programmed mathematical optimization algorithms. Those work like the classic “warmer or colder” game to find the magnets, and were further improved with directionality. The did have to correct for the Earth’s own magnetic field, but found that that could be achieved by essentially canceling out the common magnetic field seen by all of the sensors. This allowed them to track magnets in 3D space quickly enough to be useful for modern applications.