APPLICATION OF GYROSCOPES IN TECHNOLOGY

Application of gyroscopes in technics.

Properties of gyroscope are used in devices - gyroscopes, basic part of which is a quickly running around rotor that has a few degrees of freedom. Gyroscopes, a barycenter of wich coincides with the center of hanger of O, are named astatic, otherwise - static gyroscopes. The special gyromotors are used for providing high-speed rotation of the rotor of gyroscope. The sensors of corner and sensors of moment are used for controlling of gyroscope and recording the information from it. Gyroscopes are used as components both in the systems of navigation (artificial horizon, gyro-compass) and in the systems of orientation and stabilizing of space vehicles. The indications of gyroscope must be corrected by a pendulum at the use in gyrovertical, as there is deviation from the truth of vertical line because of daily rotation of earth and movement of gyroscope. Besides that, displacement of its centre of mass can be used in mechanical gyroscopes, that is equivalent to the direct affecting of pendulum gyroscope.

Great application is found by gyroscopic devices for automatic control of motion of airplanes and ships. For maintenance of the set course of ship serves the "gyropilot", for airplane - "autopilot". Free gyroscope with the large own moment of impulse and small force of friction in the places of gimbal is applied in a device the "gyropilot". Direction of motion of ship is set by direction of axis of free gyroscope. At any deviations of the ship’s course, the axis of gyroscope saves the former spatial direction, and gimbal turns in relation to a hull. The turn of frame of gimbal is watched through the special devices that give out commands to the automats to turn of helm and return the ship on the set course.

A "autopilot" is provided with two gyroscopes. At one of them an axis is disposed apeak and in such position gyroscope is untwisted. The apeak located axis of gyroscope sets a horizontal plane. The axis of the second gyroscope is disposed horizontally, orienting it along the axis of airplane. This gyroscope "knows" the course of airplane constantly. Both gyroscopes give corresponding commands to the management mechanisms that support flight of airplane on the set course. Presently all modern airplanes intended for the protracted flights are equipped with autopilots. A gyroscope is an important component in control system of space vehicles.

Gyroscopes are also applied in the systems of navigation. Inertial navigation refers to such method of determining the location in space, that doesn’t use any data of some external sources. All sensor elements are directly aboard a transport vehicle. Inertial measuring devices of linear accelerations – accelerometers are set on the gyrostabilized platform. This platform, using the properties of gyroscope - to save unchanging the orientation of the axis in space, provides directly horizontal position of axes of sensitiveness of accelerometers. The measured accelerations are integrated twice, and, thus, the information about the moving object location increment turns out. United by the common objective of determining the coordinates of moving object, gyroscopes and accelerometers form an inertial navigation system. Besides that it supplies with information about the angular orientation of object : angles of roll, pitches and yawing and the speed of object.

The construction of the modern inertial navigation system incorporates the last achievements of precision mechanics, theory of automatic control, electronics and computer facilities. Structurally an inertial navigation system can be divided into two classes: platform and cardan-less. In the first class a gyrostabilized platform is realized physically as a frame of three-step gimbal. In such systems traditional gyroscopes with a running around rotor are used. These systems are the part of the board navigation equipment of heavy airplanes.

The other class - strapdown differ in that the plane of horizon is realized mathematically, using data of gyroscopes and accelerometers. Laser and fiber-optic gyroscopes can be used in these systems. There are no running around parts, and the angular velocity is measured by the phase delay of laser ray that runs about the continuous loop. They are substantially structurally simpler and cheaper than platform. A gyroscope is mostly used as a sensitive element of indicative gyroscopic devices and as a sensor of angle of rotation or angular velocity for the automatic control devices. On some occasions, gyroscopes are used as generators of moment of force or energy, for example, in gyrostabilizers.

Simplest gyroscope

The simplest gyroscope is an ordinary child's whipping top quickly running around about the axis. The axis of whipping top can change the position in space, as it’s upper end is not fixed. At the gyroscopes applied in a technique, the free turn of axis can be provided, fastening it within the framework of gimbal, allowing the axes of whipping top to take any position in space. Such a gyroscope has three degrees of freedom. Properties of gyroscope are manifested at implementation of two terms : the axis of rotation of gyroscope must have the opportunity to change the direction in space, and the angular velocity of rotation of gyroscope about the axis must be very great as compared to that angular velocity that an axis will have while changing the direction.

The first property of gyroscope with three degrees of freedom is that it’s axis strives to save the primary direction in outer space steadily. If this axis is directed at some star in the beginning, then at any moving of the base of device and casual pushes it would continue to specify on this star, changing the orientation of relatively earthly axes. First this property of gyroscope was used by French scientific L. Foucault for experimental proof of rotation of the Earth about it’s axis in 1852. That is why it’s called "gyroscope", it means "look after a rotation" in translation. The second property of gyroscope reveals, when the force or pair of forces, aspiring to set an axis in motion, start acting on this axis. Under the action of force the end of axis of gyroscope would deviate in the direction perpendicular to this force; as a result a gyroscope together with a framework would begin to rotate around the axis, besides not speed-up, but with a permanent angular velocity. This rotation is called a precession; it goes the slower, than quicker a gyroscope runs around about the axis. If at some moment the action of force would stop, then a precession ceases simultaneously and axis stops instantly, i.e. precessional motion of gyroscope is fast-response. Along with a precession under the influence of forces an axis of gyroscope can make a nutation - small, but rapid, usually invisible to eye, vibrations of axis near it’s middle direction. The scopes of these vibrations at a quickly rotating gyroscope are very small and damp quickly because of the presence of resistance.

Precessional motion can be observed in child's whipping top.

If the axis of such whipping top is put at an angle corner to the vertical line and release, then it would deviate in perpendicular direction under the action of gravity, and starts to precess round a vertical line.

The precession of whipping top is also accompanied by invisible to eye nutation vibrations that damp quickly because of air resistance. Under the air resistance the own rotation of whipping top is gradually slowed, and speed of precession increases. When the angular velocity of rotation of whipping top becomes less certain size, it loses stability and falls.

Nutation oscillation of the slowly running around whipping top can be quite noticeable and, composed with a precession, nutation vibrations can change the pattern of motion of axis of whipping top : the upper end of axis would move in waves or loop-like.

Stabilization systems

There are three basic types of stabilization systems:

1.                   Power stabilization system (on two-stage gyroscopes).

One gyroscope is needed for stabilizing around each axis. Stabilizing is carried out by a gyroscope and unloading engine, a gyroscopic moment operates at the beginning, and then an unloading engine is connected.

2.                   Indicatory-power stabilization system (on two-stage gyroscopes).

One gyroscope is needed for stabilizing around each axis. Stabilizing is carried out by unloading engines, but a small gyroscopic moment appears at the beginning that it is possible to ignore.

3.                   Indicator stabilization system (on three-stage gyroscopes)

One gyroscope is needed for stabilizing around two axis. Stabilizing is carried out only by unloading engines.

New types of gyroscopes

The ever-increasing requirements for accuracy and performance descriptions of gyro devices compelled scientists and engineers of many countries of the world not only to improve the classic gyroscopes with a rotating rotor, but also to search for fundamentally new ideas that would solve the problem of creation of sensible sensors for measuring and displaying the parameters of angular motion of object.

In the USA, EU, Japan, Ukraine and Russia thousands of patents and author's certificates for the corresponding discoveries and inventions are issued. Since precision gyroscopes are used in long-range strategic missile guidance systems, information on research in this area was classified as secret information during the cold war.

Prospects for the development of gyroscopic instrumentation

A third-generation navigation satellite system is presently being developed. It will determine the coordinates of objects on the earth's surface with an accuracy of units of centimeters in differential mode, at being in the zone of coverage of correcting signal of DGPS. At the same time allegedly there is no need to use course gyroscopes. For example, the installation of two receivers of satellite signals on the wings of the airplane , allows to obtain information about the rotation of the aircplane around the vertical axis.

However the systems of satellite navigational appear incapable to determine position in urban conditions, with poor visibility of satellites. Similar problems reveal in wooded areas.

In addition, the passage of the signals of the navigation system depends on the processes in the atmosphere, obstacles and signal reflections. Autonomous gyroscopic devices work in anywhere- under earth, under water, in space. In airplanes the satellite navigation system is more accurate in long areas than inertial navigation system. But the use of two satellite navigation receivers to measure the angles of inclination of the airplane gives errors up to several degrees. The calculation of the course by determining the speed of the airplane with this system is also not accurate enough. Therefore, in modern navigation systems, the optimal solution is a combination of satellite and gyroscopic systems, called an integrated system.

In recent decades, the evolutionary development of gyroscopic technology has reached the threshold of quality changes. That is why the attention of specialists in the field of gyroscopy is now focused on finding non- standard applications of such devices. Completely new interesting tasks have been occurred: geological exploration, earthquake prediction, ultra-precise measurement of the positions of railways and oil pipelines, medical equipment and many others.

Conclusion

Almost every sea-going vessel is equipped with a gyrocompass for manual or automatic control of the vessel, some are equipped with gyrostabilizers. There are a lot of additional gyroscopes in control systems for naval artillery fire, providing a stable reference system, or measuring the angular velocity. Automatic control of torpedoes is impossible without gyroscopes. Aircraft and helicopters are equipped with gyroscopic devices that provide reliable information for stabilization and navigation systems. Such instruments include the attitude indicator, the vertical gyroscope, the gyroscopic pointer and roll twist. The gyroscopes can be as a pointing devices, and sensors of the autopilot. A lot of the planes provides for gyro-stabilized magnetic compasses, and other equipment and navigation signs, cameras with gyro. In military aviation gyroscopes are also used in the sights of aerial shooting and bombing. Gyroscopes for different purposes (navigation, power) are available in different sizes depending on the operating conditions and the required accuracy. In gyroscopic devices the rotor diameter is 4-20 (cm), and the smaller value refers to aerospace devices. The diameters of the rotors of the ship's gyrostabilizers are measured in meters.