Why is a gyroscope called a gyroscope

When the wheel isn't spinning, gyroscopes are effectively over-engineered paperweights. If you try to stand one up, it will simply fall over obviously. The key to them is in their spin. Perhaps you've played with gyroscopes as a child? Maybe you have a fidget spinner? If so, you'll remember how they can perform lots of interesting tricks. You can balance one on a string or your finger whilst it is in motion, for example.

Another noticeable property of them, if you've ever held one, is that it will try to resist attempts to move its position. You can even tilt it at an angle when suspended from a stand, and it will appear to levitate, albeit whilst orbiting the stand.

Even more impressively, you can lift up a gyroscope with a piece of string around one end. The explanation for this phenomenon is tricky to understand intuitively.

Their ability to seemingly defy gravity is a product of angular momentum , influenced by torque on a disc, like gravity, to produce a gyroscopic precession of the spinning disc or wheel.

This phenomenon is also known as gyroscopic motion or gyroscopic force, and it has proved to be very useful indeed for us humans. These terms refer to the tendency of a rotating object, not just a gyroscope, to maintain the orientation of its rotation. As such, the rotating object possesses angular momentum, as previously mentioned, and this must be conserved.

Because of this, t he spinning object will tend to resist any change in its axis of rotation, as a change in orientation will result in a change in angular momentum. Another great example of precession occurs with the planet Earth too. As you know, the Earth's rotational axis actually lies at an angle from the vertical which, owing to its angle, traces a circle as the rotational axis itself rotates.

While not entirely relevant to this article, the reason for Earth's odd tilt is actually pretty interesting. This effect is enhanced the faster the disc or wheel is spinning, as Newton's Second Law predicts. This seems pretty obvious to anyone with a basic knowledge of physics. The main reason they seem to defy gravity is the effective torque applied to the spinning disc has on its angular momentum vector. The influence of gravity on the plane of the spinning disc causes the rotational axis to "deflect".

This results in the entire rotational axis finding a "middle ground" between the influence of gravity and its own angular momentum vector. Now, factoring in the fact that the gyroscope is being stopped from falling towards the center of gravity by something in the way leads to the fascinating properties we see in these devices.

A picture -- well video -- is worth a thousand words, so we'll delegate a more in-depth explanation to the following video:. In order to fully answer this question, we need to assess how each device works. Since we have already covered the gyroscope in some detail above, let's check out what an accelerometer is and how it works. Open in a separate window. Figure 1. Mechanical Gyroscopes A mechanical gyroscope essentially consists of a spinning mass that rotates around its axis.

Principle of Mechanical Gyroscopes: Gyroscopic Effects The basic effect upon which a gyroscope relies is that an isolated spinning mass tends to keep its angular position with respect to an inertial reference frame, and, when a constant external torque respectively, a constant angular speed is applied to the mass, its rotation axis undergoes a precession motion at a constant angular speed respectively, with a constant output torque , in a direction that is normal to the direction of the applied torque respectively, to the constant angular speed [ 14 ].

Figure 2. Mechanical Displacement Gyroscopes The primary application of gyroscopic effects consists in the measurement of the angular position of a moving vehicle. Mechanical Rate Gyroscopes Rate gyros measure the angular speed of a vehicle during rotary motion. Figure 3. Description of Common Mechanical Gyroscopes A mechanical gyroscope consists of: 1.

Optical Gyroscopes Optical gyroscopes operate by sensing the difference in propagation time between counter-propagating beams travelling in opposite directions in closed or open optical paths. Figure 4. Sagnac Effect The underlying operating principle of almost all optical gyroscopes is the Sagnac effect. Figure 5.

Figure 6. Lock-In Effect The lock-in effect occurs only for conditions of weak mutual coupling between the two counter-propagating laser beams. Critical Parameters for RLGs The critical parameters for ring laser gyroscopes are: Size: Larger ring lasers gyroscope can measure lower rotation rates. Figure 7. Figure 8. Intensity I of the output photo-current of the photo-detector. Figure 9.

Key Gyro Performance Factors In this section, five critical parameters for consumer grade gyros will be overviewed: 1. Angle Random Walk In the output of a gyro, there is always a broadband white noise element.

Bias Offset Error When input rotation is null, the output of the gyro could be nonzero. Bias Instability Bias Instability is the instability of the bias offset at any constant temperature and ideal environment.

Temperature Sensitivity Gyro performance changes over temperature. Shock and Vibration Sensitivity Noise and Bias offset of gyros also degrade under vibration and shock input. Gyro Technology Comparison The evolution of modern gyros technology, performance and application could be understood through an overview of its history starting from midth century. Table 1 Gyro technology comparison in terms of Bias Stability.

Companies Involved in the Development of Gyroscope Technologies In this section, with reference to the previous gyroscope technologies, we report in Table 2 the companies, divided for geographic area, that actually are the main players in the gyroscope market.

Table 2 Main players for gyroscope market. Conclusions In this review, we reported the currently more diffused gyroscope technologies. Author Contributions All authors have contributed in writing this review paper, discussing the main technology features and performance. Conflicts of Interest The authors declare no conflict of interest. References 1. Wexford College Press; Kiel, Germany: King A. Inertial Navigation—Forty Years of Evolution. GEC Rev. Inertial Labs.

Ezekiel S. Springer-Verlag; Heidelberg, Germany: Fiber-Optic Rotation Sensors. Tutorial Review. Dakin J. Volume 4. Artech House; London, UK: Lefevre H. The Fiber Optic Gyroscope. Aronowitz F. The laser gyro. In: Ross M. Laser Applications. Volume 1. Macek W. Rotation rate sensing with travelling wave ring lasers. Greiff P. Yazdi N. Micromachined inertial sensors. Barbour N. Inertial sensor technology trends. IEEE Sens. Halliday D. Fundamentals of Physics.

Britting K. Inertial Navigation Systems Analysis. Robertson H. Postulate versus observation in the special theory of relativity. Page L. Juang J. Semiconductor Ring Laser Apparatus. Kiyan R. Bidirectional single-mode Er-doped fiber-ring laser.

Cai H. IEEE Trans. Mignot A. Single-frequency external-cavity semiconductor ring-laser gyroscope. Schwartz S. Solid-state ring laser gyro behaving like its helium-neon counterpart at low rotation rates. Hurst R.

Experiments with an m 2 ring laser interferometer. Fan Z. Direct dither control without external feedback for ring laser gyro. Laser Technol. Korth W. Passive, free-space heterodyne laser gyroscope. Quantum Gravity. High-accuracy absolute rotation rate measurements with a large ring laser gyro: Establishing the scale factor. Vali V.

Fiber ring interferometer. Kim H. Air-core photonic-bandgap fiber-optic gyroscope. Lightwave Technol. Quantum Electron. Sanghadasa M. Lloyd S. Wang Z. Dual-polarization interferometric fiber-optic gyroscope with an ultra-simple configuration. Lei M. Current modulation technique used in resonator micro-optic gyro. Xie H. Integrated Microelectromechanical Gyroscopes. Maenaka K. Analysis of a highly sensitive silicon gyroscope with cantilever beam as vibrating mass.

Actuators A. Clark W. Juneau T. Zhanshe G. Research development of silicon MEMS gyroscopes: a review. Mochida Y. Seshia A. Zaman M. Sharma A. IEEE J. Solid-State Circuits. A mode-matched silicon-yaw tuning-fork gyroscope with subdegree-per-hour Allan deviation bias instability. Microelectromechanical Syst. How Gyroscopes Work. Precession " ". Click here to download the second full-motion video showing precession at work. In figure 1, the gyroscope is spinning on its axis.

In figure 2, a force is applied to try to rotate the spin axis. In figure 3, the gyroscope is reacting to the input force along an axis perpendicular to the input force. The Cause of Precession " ". As forces are applied to the axle, the two points identified will attempt to move in the indicated directions.

Uses of Gyroscopes The effect of all this is that, once you spin a gyroscope, its axle wants to keep pointing in the same direction.

Gyroscope FAQ What is a gyroscope used for? Gyroscopes are built into compasses on ships and aircraft, the steering mechanism in torpedoes, and the guidance systems installed in ballistic missiles and orbiting satellites among other places.

Why do gyroscopes defy gravity? They may seem to defy gravity, but they don't. That effect is due to the conservation of angular momentum. What is the gyroscopic effect? This effect refers to the way a rotating object wants to maintain the axis of its rotation. In Heading indicators : Gyroscopes are used in heading indicators, also known as directional gyros.

The heading indicator has an axis of rotation that is set horizontally, pointing north. But unlike a magnetic compass, it does not seek north. In an airliner, the heading indicator slowly drifts away from north and needs to be reoriented at regular intervals, using a magnetic compass as a reference. As gyrocompass : The directional gyro may not seek out north, but a gyrocompass does. It does so by detecting the rotation of the earth about its axis and then seeking the true north, instead of the magnetic north.

Usually, they have built-in damping to prevent overshoot when re-calibrating from sudden movement. With accelerometers : Gyroscopes are also used along with accelerometers, which are used to measure proper acceleration.

While a simple accelerometer consists of a weight that can freely move horizontally, a more complicated design comprises a gyroscope with a weight on one of the axes. For more information about accelerometers, check out our blog on accelerometers. In Consumer Electronics : Given the fact that the gyroscope helps calculate orientation and rotation and is used for maintaining a reference direction or providing stability in navigation, designers have incorporated them into modern technology.

In addition to being used in compasses, aircraft, computer pointing devices, gyroscopes are now also used in consumer electronics. In fact, Apple founder Steve Jobs was the first one to popularize the usage or application of the gyroscope in consumer electronics; he did so by using them in the Apple iPhone. Since then, gyroscopes have come to be commonly used in smartphones. Moreover, a few features of Android phones - think PhotoSphere or Camera and VR feature - can not work without a gyroscope sensor in the phone.

It is the Gyro sensor in our smartphones that senses angular rotational velocity and acceleration. This is what makes it possible for us to play using motion senses in our phones, tablets. When we move our phone, the photo or the video moves due to the presence of a tiny gyroscope in the phone.

In toys : Gyroscopes are also used in toys, in fact there are toy gyroscopes which make for great educational tools as they help kids understand how gyroscopes work. In bicycles : Electric powered flywheel gyroscopes inserted in bicycle wheels are said to be a good alternative to training wheels.