Rate Gyro Board

H Scientific has developed Compass/Attitude Sensing Systems which allow a ship or underwater vehicle to navigate more precisely than with conventional sensors. The systems make use of datafusion algorithms that take rate gyro sensor information (providing an indication of rate-of-turn about the axis of interest) and fuse this with the primary sensor data (e.g. fluxgate compass for heading) to provide a more accurate angular reference.

The system corrects for:

Transient linear acceleration errors e.g. Northerly turning or Sea State errors;
Compass deviation;
Finite compass data latency and update rate.

In its simplest form, the system is used for providing accurate heading data on surface vessels, where it may be needed as a heading reference for ARPA RADAR or an autopilot. The datafused heading exhibits greatly reduced lag, compared to the primary source data; when used as a reference for ARPA RADAR, this can help the system to keep track of targets during fast turning manoeuvres. The system includes, as an option, a compass deviation calibration module. This module maps out the compass deviation errors, which can then be subtracted from the compass data to provide a corrected magnetic heading.

The same datafusion process has been used for roll and pitch sensors. The resulting datafused signals are available on a quasi continuous basis. The datafused signals are more accurate than pure tilt sensor data as they are corrected for:

Transient acceleration errors;
Tilt sensor nonlinearity;
Clipping errors.

The system may be used to extend the effective range of a tilt sensor for certain applications. Indeed, if no tilt sensor is used at all, the system may be used to provide very cost-effective tilt indication e.g. for measuring sea state motions. The datafusion algorithms are incorporated into the rate gyro PCB.

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