A typical location update rate of indoor positioning systems or GPS is ~8-16Hz, which is enough for the majority of industrial applications, but not for all.
A practical way to increase the location update rate to 100Hz and more is to use IMU and ultrasound sensor fusion that combines the best of both sources of data: a very fast update rate and robustness of IMU and absolute coordinates and no drift of the ultrasound indoor positioning system.
Typical applications of the fast indoor positioning system with sensor fusion:
The same is true for our ultrasound-based Indoor Positioning System – Indoor “GPS”:
As a result, the typical update rate for a typical-size submap of 10-15m is ~8Hz when only ultrasound is employed for positioning.
To achieve the highest update rate, see the article: How to increase location update rate and reduce latency?
It is possible to increase the update rate further by specifically tuning the system for this requirement, for example, for the expense of the level of filtering or even accuracy. But the main limiting factor – time of flight of ultrasound – is impossible to eliminate until you reduce the size of the submap.
For tiny submaps of 2-3 meters, for example, air hockey, it is possible to have up to a 40Hz update rate. But this is a very special case.
There are several ways to increase the location update rate:
1) Do post-processing interpolation in the Dashboard using the Realtime Player:
2) Do post-processing of sensor fusion in the Dashboard:
3) Do real-time processing of sensor fusion either on the external computer or onboard:
IMU + Ultrasound sensor fusion post-processing is a real sensor fusion mechanism because two sources of location data are combined:
Each of the sources of location data has strong and weak points:
Ultrasound indoor positioning system’s strong points:
Let’s now see in practice how sensor fusion works.
Process in short:
Characteristics of the track below:
Characteristics of the track below:
The track is now real native 100Hz, and it became more robust against short-time obstructions at the same time
One can see how the IMU dots decelerate near the angle and accelerate after passing the angle.
Conditions are the same as for the example above. But the shape of the track is different to show the performance.
Notice that when there are too few ultrasound positioning points – either the object is too quick or the location updates are too rare – the Realtime Player clearly “cuts corners”. That leads to higher positioning errors.
Currently available implementation of IMU + Ultrasound Sensor Fusion – Post-Processing functionality shows about 10+0.12sec/1sec post-processing speed. Thus, for example:
The figures above are the results of calculations on a Win11 and Intel i5 laptop. Faster desktop computers will provide post-processed results much quicker.
Future code optimization may significantly reduce the post-processing time without needing new hardware or a new license.
Sensor fusion for positioning is a complex task because the location in the inertial positioning system is calculated based on the double integration of the accelerometer data. It isn’t easy to clearly distinguish between the actual acceleration of a tracked mobile object and the impact of the Earth’s gravitation. Thus, inertia-based indoor positioning systems without sensor fusion can’t work.
At the same time, sensor fusion for angle is a significantly more manageable task. We have been commercially offering this functionality for years. Read more:
Sensor fusion is a complex functionality but enables the best possible performance for precise indoor positioning systems because it efficiently combines data from several sources.
Thus, for example, instead of the typical update rate of ~8Hz for a standalone indoor positioning system, the indoor positioning system with IMU sensor fusion achieves an update rate of 100Hz while keeping the same or higher accuracy than a system without IMU sensor fusion and showing even additional robustness against short non-line of sight events or external acoustic noise.
The Realtime Player is sufficiently good for smooth curves or curves with a high enough update rate compared to the curve’s sharpness.