Faster Magnet Tracking for Better Virtual Reality

The faster simultaneous tracking of many magnets is expected to improve head position following and therefore the display of correct graphics in virtual reality (VR) headsets.

The time it takes for headset tracking systems to detect magnet movement, which is head movement, and compute the changes has been an obstacle to better graphic and information display. Magnets are located in headsets and their electromagnetic fields (EMF) allow EMF sensors to detect head movement speed and direction. The challenge in calculating what movement is taking place is that the orientation of the magnet if a head is turned, may not automatically be known, and therefore the direction the magnet is moving in, as the person moves, cannot be recognised. The solution is a special algorithm to accelerate the magnet position computation. 

“If you wanted to step into the virtual reality world and, say, kick a ball, this [algorithm] is super useful for something like that,” said Massachusetts Institute of Technology Media Lab researcher, Hisham Bedri. “This brings that future closer to a reality.” The algorithm is expected to improve the simultaneous tracking of any number of magnets which also means that there is no need for the fixed magnetometer arrays used up to now. 

It is because of the uncertainty surrounding a magnet’s orientation and then its direction of travel that requires the use of magnetometers for EMF sensors. These devices measure magnetism, its direction, strength, or the relative change of the magnetic field at a particular location. But interpreting magnetometers’ readings has its drawbacks.

Magnetic attraction

The algorithm is expected to reduce the time it takes to process the magnetometers’ data to determine the positions and orientations of magnets that are embedded in a headset; or other objects such as the human body or wood, ceramics or other materials. The algorithm also solves a problem with interference from the Earth’s magnetic field. The researchers say that previous methods of eliminating that interference were not practical for a compact, mobile system like a VR headset, or prostheses and exoskeletons. The researchers’ solution was to have the software search for and identify the Earth’s own magnetic field, and to ignore it.

The algorithm has been tested with magnetometer sensors to track up to four tiny, pearl-like magnets. According to the researchers, the tests demonstrated that in comparison to state-of-the-art magnet tracking systems, the new algorithm increased magnetometers’ maximum bandwidths by 336%, 525%, 635%, and 773% when used to simultaneously track one, two, three, and four magnets respectively.

Beyond VR headsets, the faster, more accurate magnet tracking is expected to help robots move more quickly and for better reflexive control of exoskeletons and prostheses; where magnets could be embedded in the human body as part of the prostheses control system. To date, technology has existed to implant into a prosthesis user’s nervous system or muscles, wires that transmit a signal, or that cross the skin boundary, to control the prosthesis’ mechatronics. Small magnets that allow a muscle’s movements to be detected could be a less intrusive solution.