Ring laser gyroscope is the result of over 100 years of research, development, and experimentation in the field of navigation technology. They are essential to flight safety, reduced human error, accuracy, and more, in both manned and unmanned aerial vehicles.
While the first laser gyro was experimentally demonstrated in 1963, by W.M. Macek and D.T.M. Davis, the very first usable gyrocompass goes back as far as 1904 and was invented by German inventor Hermann Anschütz-Kaempfe.
Gyroscopes have come a long way since then, evolving from mechanical to optical self-contained laser technology such as the Honeywell Ring Laser Gyroscope or RLG.
Ring laser gyroscopes are today’s industry standard and abide by the Sagnac effect to sense orientation, which manifests itself in a ring interferometer. The interferometer is where a ring laser gyro is initially set up.
Interferometers are investigative tools that operate by superimposing two or more light sources to create an interference pattern, which is then tracked and analyzed.
Interferometers are typically used for highly sensitive measurements which cannot be achieved in other ways, such as identifying variations on microscopic organisms or detecting gravitational waves and have wide applicability.
Ring laser gyroscopes for inertial navigation
Ring laser gyroscopes are lightweight, compact, and self-contained, which allows for no friction. This is a major benefit, especially for inertial navigation systems (INS). Having no moving parts and being lightweight, prevents them from producing extra drag for the system in which they are set up.
Moreover, today’s laser ring gyroscopes are significantly smaller than previous models, which makes them the perfect choice for complex and sensitive technologies like inertial navigation systems, where accuracy, reliability, and efficient use of space, are key.
Ring laser gyroscopes for transportation systems
Ring laser gyroscopes are gaining more and more attention in the transportation systems industry given their unique attributes. Ring laser gyros are small, compact, lightweight, and radiation tolerant.
To date, they are mainly used in air and space vehicles, however, there is growing interest in INS in other transportation systems enabling the gyroscope market to develop faster than ever before.
Due to their superior accuracy and performance stability, ring laser gyros are also extensively used in military operations, specifically in missile navigation, but also in military aircraft and ground vehicles.
Types of Gyroscopes
The following are the three types of gyroscopes:
- Mechanical gyroscope.
- Optical gyroscope.
- Gas-bearing gyroscope
1- Mechanical Gyroscope
The working principle of the mechanical gyroscope is based on the conservation of angular momentum. This is also one of the most commonly known gyroscopes. The mechanical gyroscope is dependent on the ball bearing to spin.
These gyroscopes are replaced with modern forms of gyroscopes as they are noisier. They find applications in the navigation of large aircraft and missile guidance.
2- Optical Gyroscopes
These gyroscopes are dependent on the ball bearing or the rotating wheel. They are also not based on the conservation of angular momentum. Optical gyroscopes use two optic fiber coils spun in different orientations.
Since there is no movement in the optical gyroscopes, these are considered to be durable and find applications in modern spacecraft and rockets.
3- Gas-Bearing Gyroscopes
In a gas-bearing gyroscope, the friction between the moving parts is reduced by suspending the rotor with the help of pressurized gas. NASA used a gas-bearing gyroscope in the development of the Hubble telescope. Compared to the other gyroscopes, gas-bearing is quieter and more accurate.
When the Boeing 757-200 entered service in 1983, it was equipped with the first suitable ring laser gyroscope. This gyroscope took many years to develop, and the experimental models went through many changes before it was deemed ready for production by the engineers and managers of Honeywell and Boeing.
How does a ring laser gyroscope work?
The interferometer used for the ring laser gyro comprises narrow tunnels that form a closed circle surrounding a block of zero expansion glass, which is made of lithium oxides, aluminum, and silicon.
To create the interference pattern for the Sagnac effect, three mirrors are placed at each vertex and two counter-propagating laser beams are formed in the active cavity.
Although the beams run in different, opposite directions, they enter and exit at the exact same point, which enables the interferometer to measure the reassembled signal at the moment of the exit.
When a ring laser gyro is in motion, the beams of light travel different distances. The difference in frequency is proportional to the rotation rate. The frequency difference is measured via an interference fringe pattern whose phasing contains the directional information.
In addition to being used in compasses, aircraft, computer pointing devices, etc., gyroscopes have been introduced into consumer electronics. The first usage or application of the gyroscope in consumer electronics was popularized by Steve Jobs in the Apple iPhone.
Since the gyroscope allows the calculation of orientation and rotation, designers have incorporated them into modern technology. The integration of the gyroscope has allowed for more accurate recognition of movement within a 3D space than the previous lone accelerometer within a number of smartphones.
Gyroscopes in consumer electronics are frequently combined with accelerometers for more robust direction- and motion-sensing.
Examples of such applications include smartphones such as the Samsung Galaxy Note 4, HTC Titan, Nexus 5, iPhone 5s, Nokia 808 PureView, and Sony Xperia, game console peripherals such as the PlayStation 3 controller and the Wii Remote, and virtual reality sets such as the Oculus Rift.