Close your eyes. Now walk around randomly for an hour (try not to hit anything). Don’t open your eyes yet. Can you mentally map your path over the last sixty minutes? Where are you now?
That was an impossible task for humans, and it’s surprisingly difficult for computers as well. Sure, computers can tap into GPS and other satellite tracking systems, but those systems aren’t perfect. Tunnels stump them. So do buildings. And even if you stay outside and in the open, your phone’s GPS is only accurate within a roughly 5 meter radius.
Another option is to use an electronic device called an inertial measurement unit (IMU). IMUs track their position over time using a combination of accelerometers, gyroscopes, magnetometers, or lasers. But IMUs aren’t perfect either. Tiny measurement errors add up to cause a difference between where the IMU thinks it is and where it actually is, a problem called drift. Drift gets worse as time goes on.
All IMUs suffer from drift to some degree, but that may be about to change. Canadian company Micron Digital Corp has developed a new IMU, called ROMOS, which founder and CTO Rohit Seth claims is the world’s first drift-free tracking chip.
The Problem of Drift
There are two types of position tracking systems: outside-in and inside-out. Outside-in tracking uses external references, like GPS satellites, to track the position of a system. Inside-out tracking uses internal sensors like IMUs. For the best of both worlds, systems often combine outside-in and inside-out tracking. For example, your smartphone has an integrated IMU, but it also checks in with GPS continuously to correct for the IMU’s drift error.
Not all IMUs are created equal. Consumer-grade IMUs, like those found in your phone, have the highest amount of drift—up to 7900km/hour. You read that number right. In the worst case scenario, the IMU in your phone could think you’ve tunneled more than halfway through the planet in the space of an hour. Thankfully, with proper calibration, that error can be reduced by a couple orders of magnitude. Even so, it’s clear why it’s necessary to check in with GPS.
At the top of the IMU food chain are marine-grade IMUs, which help submarines navigate underwater. Even these IMUs—which cost around $1M a piece—drift by up to 1.8km/day, forcing submarines to routinely check in with GPS.
If it weren’t for drift, a system could track its position in any environment and for any length of time using only an IMU. A drift-free IMU is exactly what Micron Digital is claiming with ROMOS. Shorthand for RealMotion, ROMOS is a MEMS-based IMU that, according to Micron Digital, eliminates the problem of drift. Not reduces—eliminates.
ROMOS: A Drift-Free IMU
When British surveyors first determined the height of Mt. Everest, they found it to be exactly 29,000 feet. Not wanting the public to assume this round figure was an approximation, the surveyors falsely reported the height as 29,002 feet. Micron Digital can relate to those surveyors. “Zero drift” sounds too much like an approximation for “low drift,” according to Seth.
“Every time we talk to anyone about ROMOS, they expect an answer of bias drift,” he said. “They don’t believe it [that there is no drift].”
Considering the fact that $1M marine-grade IMUs haven’t eliminated drift, this skepticism is understandable—especially considering that, when ROMOS comes out of development and hits mass production, it’s set to be priced at the consumer level of roughly $5/unit.
To back up its claims, Micron Digital showed engineering.com two demonstrations of ROMOS at the company’s Mississauga office. The first demonstration was set up over a year ago for a potential client whose name you would recognize, but whom Micron can’t disclose. Micron set up a static ROMOS alongside a custom application reflecting its position and displaying its cumulative drift. A camera pointing at the scene broadcasts a live feed to the potential client. After 454 days and counting, the total drift remains at (0.0, 0.0, 0.0).
The second demonstration highlighted one of ROMOS’s most immediate applications: automotive navigation. Automotive IMUs are typically consumer grade, high-drift units that must constantly check in with GPS. With a drift-free IMU, cars could track their position more accurately and in more environments. This is especially important for autonomous vehicles, an area Micron Digital is actively exploring.
For the demonstration, I was taken out in Micron Digital’s test car by the company's chief engineer and scientist. The car is equipped with a ROMOS chip that wirelessly sends its tracking data to a tablet mounted on the windshield. I sat in the back and gave random directions—left, right, and so on—as we drove around Mississauga. There was no GPS involved. ROMOS tracked our journey in real-time, with enough precision to see lane changes. As far as I could tell, ROMOS never wavered.
ROMOS has spent a lot of time on the road. In one test, the IMU undertook a 40km journey through Mississauga. In the data below, you can see how cleanly it kept track of its position.
This pinpoint accuracy is simply not possible with GPS. Here’s what a direct comparison looks like for a simple loop around Micron Digital’s parking lot:
How ROMOS Works
It’s natural to wonder how ROMOS achieves its unprecedented performance, but Micron Digital is protective about the details. The most they could tell me was that ROMOS performs core calculations in a higher dimensional space before dropping down to three dimensions. I wasn’t told how many dimensions are used in the calculations.
At a high level, there are several steps in the ROMOS process. First, the raw sensor data is generated as in any other MEMS-based IMU. This data then goes through primary filter algorithms, a static calibration filter, the proprietary RealMotion algorithm, and an AI smoothing function before ROMOS outputs its final position data.
ROMOS is still under development, but Micron Digital has spoken with several large companies that are interested in the technology. If it lives up to its drift-free promise, ROMOS could improve virtually any application that requires position tracking. It could serve as what Micron Digital calls a terrestrial positioning system (TPS), a system that can navigate on or under the Earth with equal precision. The company is even looking at a potential blockchain application.
Unfortunately, due to the global COVID-19 pandemic, production of ROMOS has hit a stall. However, Seth and the Micron Digital team aren’t sitting still: the company is hard at work on an application that uses its geospatial positioning technology to help trace the spread of COVID-19. More details to follow as that story develops.
If Micron Digital can reach mass production and sell ROMOS for the projected $5/unit, there’s really no limit to the impact the new IMU could make. We’ll certainly be keeping an eye on ROMOS to see how this technology develops. You can learn more about ROMOS at romos.io.