Stereo INS¶
The stereo-vision-aided Inertial Navigation System (INS) module is a base module which is available on every rc_visard and is part of the sensor dynamics module. It combines visual-odometry measurements with inertial measurement unit (IMU) data and provides robust, low latency, real-time state estimates at a high rate. The IMU consists of three accelerometers and three gyroscopes, which measure accelerations and turn rates in all three dimensions. By fusing IMU and visual-odometry measurements, the state estimate has the same frequency as the IMU (200 Hz) and is very robust even under challenging lighting conditions and for fast motions.
Note
To achieve high-quality pose estimates, it must be ensured that sufficient texture is visible during runtime of the stereo INS module. In case no texture is visible for a longer period of time, the stereo INS module will stop instead of providing highly erroneous data.
Self-Calibration¶
During startup of the stereo INS module, it will self-calibrate the IMU using the visual-odometry measurements. For the self-calibration to succeed, it is required that
- the rc_visard is not moving and
- sufficient texture is visible
during startup of the stereo INS module. Failure to meet these requirements will most likely result in a constant drift of the pose estimates.
Parameters¶
The stereo INS module’s node name is rc_stereo_ins.
This module has no run-time parameters.
Status values¶
This module reports the following status values:
| Name | Description |
|---|---|
freq |
Frequency of the stereo INS process in Hertz. This value is shown as Update Rate in the Web GUI Overview tab in the Dynamics area |
state |
String representing the internal state |