What Makes Strap-Down INS the Preferred Systems for Aviation?

The aviation industry has been using strap-down inertial navigation system (INS) for positioning and navigation. It provides three-dimensional aircraft velocity and position fix. The self-contained system makes the technology suitable for aircraft. Our inertial simulator can provide a powerful test platform to assess the system, helping you determine the efficiency of strap-down INS.

But what makes the system the top choice for the aviation industry?

Reduced INS Position Errors

The strap-down system uses gyros and accelerometers mounted directly to the aircraft’s frame. The INS platform moves exactly as the aircraft does. The system is more feasible with the aircraft because of its accuracy.

 Today’s strap-down INS may have error rates of 0.6 nm/hr. But the system can further reduce these errors with frequent updates of position from ground-based navigation aids and GPS. Here’s how INS uses GPS data for the correction of some errors, like the following:

• Drift – Such errors exist in stabilized INS within gyro bearings and mass imbalances. Imperfections in the mirrors and their coatings often cause these. Even the tiniest errors in accelerometers result in the slightest imperfections in acceleration sensing.
• Transport Wander – A gyro attempts to maintain its original alignment with the Earth, but as the aircraft moves, the local horizontal reference changes. This turns an angle with a gyro to an error known as Transport Wander or Apparent Drift. The signals derived from the INS Latitude and Longitude corrects this issue.
• Schuler Loop – This error often occurs when the INS tries to compensate for the additional tilt during decelerations. Instead of catching up, the system ends up chasing itself. The position error would be immense after 42.2 minutes, and zero after 84.4 minutes. It grows with each cycle of the Schuler Loop.
• Earth rotation – The INS detects the rotation of the Earth even when moving. The final movement detected combines both the aircraft’s movement and the Earth’s rotation. The errors may be small and can be counteracted.
• Coriolis – The INS detects turning as an aircraft travels from A to B around the globe, following a curved path. This situation can introduce an error.

An INS is a self-contained navigation system that performs better when provided with several data inputs. Using an improved GPS reception can help INS retain useful FMS position accuracy.

Easy Maintenance

Strap-down systems have few moving parts, making them easier to maintain. These systems are also more reliable over time.

The system has three gyroscopes that sense the rate of pitch, roll, and yaw. On the other hand, three accelerometers detect an increase in speed along each aircraft axis. The platform integrates these to record the orientation.

Then, as a gimballed system would, it mathematically calculates the acceleration of the north/south, east/west, and up/down axes.

Such a system needs more accurate gyroscopes and greater computing power. The aviation industry prefers the strap-down system because of its reduced costs, size, weight, as well as its reliability.

The Inertial Simulator for the Pros

At CAST, our CAST-4000 inertial simulator can provide the help that the aviation industry needs. Our powerful test platform generates GPS RF signals to simulate tightly or loosely coupled navigation systems.

Making simulations can be better since CAST-4000 can produce raw IMU measurements to a receiver when directly equipped with an optional interface.  

Contact us today or go through our portfolio for more information.