Inertial Navigation System

An inertial navigation system (INS) is a navigation aid that uses a computer, motion sensors (accelerometers) and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position, orientation, and velocity (direction and speed of movement) of a moving object without the need for external references. It is used on vehicles such as ships, aircraft, submarines, guided missiles, and spacecraft. Other terms used to refer to inertial navigation systems or closely related devices include inertial guidance system, inertial reference platform, inertial instrument, inertial measurement unit (IMU) and many other variations.

An inertial navigation system includes at least a computer and a platform or module containing accelerometers, gyroscopes, or other motion-sensing devices. The INS is initially provided with its position and velocity from another source (a human operator, a GPS satellite receiver, etc.), and thereafter computes its own updated position and velocity by integrating information received from the motion sensors. The advantage of an INS is that it requires no external references in order to determine its position, orientation, or velocity once it has been initialized.

One example of a popular INS for commercial aircraft was the Delco Carousel, which provided partial automation of navigation in the days before complete flight management systems became commonplace. The Carousel allowed pilots to enter a series of waypoints, and then guided the aircraft from one waypoint to the next using an INS to determine aircraft position and velocity.

Notes: 1) dead reckoning the position – точний обрахунок положення обєкта; 2) velocity of a moving object - швидкість обєкта, що рухається; 3) inertial guidance system – інерціальна система наведення; 4) inertial reference platform – інерціальна платформа; 5) inertial measurement unit- гиростабилизатор; 6) motion-sensing devices – прилади, що реагують на рух, 7) waypoints- пункт маршруту.

Computer system of an autopilot

The hardware of an autopilot varies from implementation to implementation, but is generally designed with redundancy (резервування) and reliability as foremost considerations (прогресивні думки). For example, the Rockwell Collins AFDS-770 Autopilot Flight Director System used on the Boeing 777, uses triplicated (потрійний) FCP-2002 microprocessors which have been formally verified and are fabricated in a radiation resistant process (радіаційно стійкий процес).

Software and hardware in an autopilot is tightly controlled, and extensive test procedures are put in place.

Some autopilots also use design diversity. In this safety feature, critical software processes will not only run on separate computers and possibly even using different architectures, but each computer will run software created by different engineering teams, often being programmed in different programming languages. It is generally considered unlikely that different engineering teams will make the same mistakes. As the software becomes more expensive and complex, design diversity is becoming less common because fewer engineering companies can afford it. The flight control computers on the Space Shuttle uses the following design: there are five computers, four of which redundantly run identical software, and a fifth backup running software that was developed independently. The software on the fifth system provides only the basic functions needed to fly the Shuttle, further reducing any possible commonality (уніфікованість) with the software running on the four primary systems.