4 ms·
What's novel here is that it is a compact, pretty accurate solid-state inertial navigation unit. https://en.wikipedia.org/wiki/Inertial_navigation_system https
by Isamu 9y ago
What's novel here is that it is a compact, pretty accurate solid-state inertial navigation unit.
https://en.wikipedia.org/wiki/Inertial_navigation_system https://en.wikipedia.org/wiki/Inertial_navigation_system
[edit] Here's a paper from 2017 to give some context to the problem of inertial navigation using the solid-state gyros and accelerometers you find in smartphones:
https://arxiv.org/pdf/1703.00154.pdf https://arxiv.org/pdf/1703.00154.pdf
> Abstract— Building a complete inertial navigation system
using the limited quality data provided by current smartphones
has been regarded challenging, if not impossible. We present
a probabilistic approach for orientation and use-case free
inertial odometry, which is based on double-integrating rotated
accelerations. Our approach uses a probabilistic approach in
fusing the noisy sensor data and learning the model parameters
online. It is able to track the phone position, velocity, and
pose in real-time and in a computationally lightweight fashion.
The information fusion is completed with altitude correction
from barometric pressure readings (if available), zero-velocity
updates (if the phone remains stationary), and pseudo-updates
limiting the momentary speed. We demonstrate our approach
using a standard iPad and iPhone in several indoor deadreckoning
applications and in a measurement tool setup.
Also: Apple is reportedly working on a full inertial navigation solution, probably for indoor use.
- blt 9y agoWhat is novel about that? Phones have had them for years
- jtuente 9y agoThe ones in phones generally use GPS corrections when tracking movement.
- blt 9y agoYes, but this paper is all about incorporating prior knowledge of human locomotion in a corrective step. There is no innovation in the field of pure inertial navigation; this would not help e.g. a quadrotor.
- nomel 9y agoNo, it’s that a cheap compact unit can be used accurately by using an understanding of the foot-planting gait of a human to remove low frequency drift in that cheap unit. The whole concept is that, using a foot, which is only moving quickly or still, you can filter out the the low frequency component of all of the signals. These sensors are relatively accurate under movement and large signals, just not so much when stil, since their signal strengths become relatively low to the offsets and noise in the system.
- mapmap 9y agoSo it measures the difference from zero in the accelerometer signals when the foot is planted and then accounts for that when the foot is moving?
- IshKebab 9y agoYes, but that technique isn't new either. Here's a 2014 paper that cites a 2009 paper about it (I didn't follow the trail): https://www.omicsonline.org/open-access/understanding-the-performance-of-zero-velocity-updates-in-memsbased-pedestrian-navigation-0976-4860-5-53-60.pdf https://www.omicsonline.org/open-access/understanding-the-pe...
- mapmap 9y agoBut there is still going to be cumulative error and drift, right? Has this system reduced the cumulative error so that in some pedestrian use cases it is accurate enough?
- AstralStorm 9y agoBoth. Long term drift will be extra challenging to correct as the cumulative error is staircase. (Beta distribution) What this is is actually a step counter, combined with step length and heading estimate from an accelerometer w/ gyroscope plus compass. When the counter makes a mistake, the effects will be catastrophic.
- thescriptkiddie 9y ago> What's novel here is that it is a compact, pretty accurate solid-state inertial navigation unit. Per the article, there is nothing special about the IMU they're using. What's novel here is the use of a foot-mounted pressure sensor and inverse kinematics to correct for accelerometer noise.
- Isamu 9y agoAgreed, but to clarify my comment, an IMU is not an inertial navigation system. I'm saying they constructed a pretty accurate inertial navigation system. The paper I cited helps to point out the difference between taking inertial measurements and putting together a reasonable navigation system.