APPENDIX A Glossary
NEETS MODULE 15-Principles of Synchros, Servos, and Gyros UNCLASSIFIED
A-1 UNCLASSIFIED APPENDIX A GLOSSARY ACCELERATION SERVO SYSTEM—A servo system that controls the acceleration (rate of change in velocity) of a load.
ACCELEROMETER—A device that measures acceleration to which it is subjected and develops a signal proportional to it.
ANGULAR POSITION—The counterclockwise angular displacement of a synchro rotor, measured in degrees from its electrical zero position, as viewed from the shaft extension end of the synchro.
APPARENT DRIFT— The effect of the Earth's rotation on a gyro, which causes the spinning axis to appear to make one complete rotation in one day. Also called APPARENT PRECESSION or APPARENT ROTATION.
APPARENT PRECESSION—See apparent drift.
APPARENT ROTATION—See apparent drift.
AXIS—A straight line, either real or imaginary, passing through a body, around which the body revolves.
BANDWIDTH—The range of frequencies a servo amplifier can amplify without causing unacceptable distortion to the input signal.
CONTROL DIFFERENTIAL TRANSMITTER (CDX)—A type of synchro that transmits angular information equal to the algebraic sum or difference of the electrical input supplied to its stator, and the mechanical input supplied to its rotor. The output is an electrical voltage taken from the rotor windings.
CONTROL SYNCHRO SYSTEMS— Synchro systems that contain control synchros and are used to control large amounts of power with a high degree of accuracy. The electrical outputs of these systems control servo systems, which in turn generate the required power to move heavy loads.
CONTROL SYSTEM—A group of components, systematically organized to perform a specific control purpose. These systems are categorized as either closed- or open-loop systems. The main difference between the two is that the closed-loop system contains some form of feedback.
NEETS MODULE 15-Principles of Synchros, Servos, and Gyros UNCLASSIFIED
A-2 UNCLASSIFIED CONTROL TRANSFORMER (CT)—A type of synchro that compares two signals: the electrical signal applied to its stator and the mechanical signal applied to its rotor. The output is an electrical voltage, which is taken from the rotor winding and is used to control a power amplifying device. The phase and amplitude of the output voltage depend on the angular position of the rotor with respect to the magnetic field of the stator.
CONTROL TRANSMITTER (CX)—A type of synchro that converts a mechanical input, which is the angular position of its rotor, into an electrical output signal. The output is taken from the stator windings and is used to drive either a CDX or CT.
CORRESPONDENCE—Th e term given to the positions of the rotors of a synchro transmitter and a synchro receiver when both rotors are on 0 or displaced from 0 by the same angle.
DAMPING—A mechanical or electrical technique used in synchro receivers to prevent the rotor from oscillating or spinning. Damping is also used in servo systems to minimize overshoot of the load.
DATA TRANSMISSION—The transfer of information from one place to another or from one part of a system to another.
DEGREE-OF-FREEDOM—The number of axes about w hich a gyro is free to precess.
DEMODULATOR—A circuit used in servo systems to convert an ac signal to a dc signal. The magnitude of the dc output is determined by the magnitude of the ac input signal, and its polarity is determined by whether the ac input signal is in or out of phase with the ac reference voltage.
DOUBLE RECEIVER—A fine and coarse synchro receiver enclosed in a common housing with a two-shaft output (one shaft inside the other).
E-TRANSFORMER—A special form of differential transformer u sing an E-shaped core. The secondaries of the transformer are wound on the outer legs of the E, and the primary is on the center leg. An output voltage is developed across the secondary coils when its armature is displaced from its neutral position. This device is used as an error detector in servo systems that have limited load movements.
ELECTRICAL-LOCK— A synchro zeroing method. This method is used only when the rotors of the synchros to be zeroed are free to turn and their leads are accessible.
ELECTRICAL ZERO—A standard synchro position, with a definite set of stator voltages, that is used as the reference point for alignment of all synchro units.
ERECTING (A GYRO)—The positioning of a gyro into a desired position and the maintaining of that position.
NEETS MODULE 15-Principles of Synchros, Servos, and Gyros UNCLASSIFIED
A-3 UNCLASSIFIED ERROR DETECTOR—The component in a servo system that determines when the load has deviated from its ordered position, velocity, etc.
ERROR REDUCER—The name commonly given to the servo motor in a servo system. So named because it reduces the error signal by providing feedback to the error detector.
ERROR SIGNAL— In servo systems, the signal whose amplitude and polarity or phase are used to correct the alignment between the controlling and the controlled element. It is also the name given to the electrical output of a control transformer (CT).
EXCITATION VOLTAGE—The supply voltage required to excite a circuit.
FREQUENCY RESPONSE—The measure of a servo's ability to respond to various input frequencies.
GIMBAL—A mechanical frame, with two perpendicular, in tersecting axes of rotation, used to support and furnish a gyro wheel with the necessary freedom to tilt in any direction.
GYRO—Abbreviation for gyroscope.
GYROSCOPE—A mechanical device containing a spinning mass mounted so that it can assume any position in space.
IC SYNCHROS—Electromechanical devices, used to transmit information, that operate on the same principles of interacting magnetic fields as synchros, but differ in their direction of rotation and the amount of torque obtainable. Because of their construction, they are sometimes called reversed synchros.
INERTIA—The physical tendency of a body in motion to remain in motion and a body at rest to remain at rest unless acted upon by an outside force (Newton's First Law of Motion).
MAGNETIC AMPLIFIER—An electromagnetic device that uses one or more saturable reactors to obtain a large power gain. This device is used in servo systems requiring large amounts of power to move heavy loads.
MILITARY STANDARD SYNCHROS—Synchros that conform to specifications that are uniform throughout the Armed Services.
MODULATOR—A circuit used in servo systems to convert a dc signal to an ac signal. The output ac signal is a sine wave at the frequency of the ac reference voltage. The amplitude of the output is directly related to the amplitude of the dc input. The circuit's function is opposite to that of a DEMODULATOR.
MULTI-LOOP SERVO SYSTEM—A servo system that contains more than one servo loop, each loop designed to perform its own function.
NEETS MODULE 15-Principles of Synchros, Servos, and Gyros UNCLASSIFIED
A-4 UNCLASSIFIED MULTISPEED SYNCHRO SYSTEMS—Systems that transmit data at different transmission speeds; for example, dual-speed and tri-speed synchro systems.
NEWTON’S SECOND LAW OF MOTION—If an unbalanced outside force acts on a body, the resulting acceleration is directly proportional to the magnitude of the force, is in the direction of the force, and is inversely proportional to the mass of the body.
POSITION SENSOR—A component in a servo system that measures position and converts the measurement into a form convenient for transmission as a feedback signal.
POSITION SERVO SYSTEM—A servo system whose end function is to control the position of the load it is driving.
POTENTIOMETER—An electromechanical device, used as a position sensor in servo systems, having a terminal connected to each end of a restrictive element, and a third connected to a wiper contact. The output is a voltage that is variable depending upon the position of the wiper contact. The potentiometer is commonly referred to as a variable voltage divider. It, in effect, converts mechanical information into an electrical signal.
PRECESSION— The rotation of the spin axis of a gyro in response to an applied force. The direction of precession is always perpendicular to the direction of applied force.
PRECESSION VECTOR— In a gyro, a vector representing the angular change of the spin axis when torque is applied. The precession vector represents the axis about which precession occurs.
PRESTANDARD NAVY SYNCHROS—Synchros that are designed to meet Navy, rather than servicewide, specifications.
RATE GYRO—A gyro used to detect and measure angular rates of change.
RESOLVER—A rotary, electromechanical device used to perform trigonometric computations by varying the magnetic couplings between its primary and secondary windings. It is generally used in circuits that solve vector problems, such as analog computers and conversion equipment. The resolver solves three different type problems: (1) resolution— separating a vector into two mutually perpendicular components; (2) composition—combining two components of a vector to produce a vector sum; (3) combination—the process of resolution and composition taking place simultaneously.
RESULTANT MAGNETIC FIELD—The magnetic field produced in a synchro by the combined effects of the three stator magnetic fields.
RIGIDITY— The tendency of the spin axis of a gyro wheel to remain in a fixed direction in space if no force is applied to it.
NEETS MODULE 15-Principles of Synchros, Servos, and Gyros UNCLASSIFIED
A-5 UNCLASSIFIED ROTOR— The rotating member of a synchro that consists of one or more coils of wire wound on a laminated core. Depending on the type of synchro, the rotor functions similar to the primary or secondary winding of a transformer. In a gyro, the rotating member is sometimes called a gyro wheel.
SCALING FACTOR— The term used to describe the use of unequal resistors in a servo's summing network to compensate for differences between input and output signal levels.
SERVO AMPLIFIER—An ac or dc amplifier used in servo systems to build up signal strength. These amplifiers usually have relatively flat gain versus frequency response, minimum phase shift, low output impedance, and low noise level. The dc amplifier is subject to excessive drift and is relatively unstable. However, the ac amplifier is considered drift free and has a constant dynamic gain over a variety of operating points.
SERVO MOTOR—An ac or dc motor used in servo systems to move a load to a desired position or at a desired speed. The ac motor is usually used to drive light loads at a constant speed, while the dc motor is used to drive heavy loads at varying speeds.
SERVO SYSTEM—An automatic feedback control system that compares a required condition (desired value, position, etc.) with an actual condition and uses the difference to adjust a control device to achieve the required condition.
SIGNAL—The angle th rough which a synchro transmitter rotor is mechanically turned.
SPIN VECTOR—In a gyro, a vector representing the angular velocity of the gyro rotor. The spin vector lies along the spin axis of the rotor.
STATOR—The stationary member of a synchro that consists of a cylindrical structure of slotted laminations on which three Y-connected coils are wound with their axes 120 apart. Depending on the type of synchro, the stator's functions are similar to the primary or secondary windings of a transformer.
STEP-TRANSMISSION SYSTEM—A data transmission system that operates on direct current. It consists of a step transmitter (rotary switch) and a step motor interconnected to transmit data (information) between remote locations.
STICKOFF VOLTAGE—A low voltage used in multispeed synchro systems to prevent false synchronizations.
SUMMING NETWORK—A combination of two or more parallel resistors used in servo systems as error detectors. The output of the network is the algebraic sum of the inputs.
SYNCHRO—A small motor -like device that operates like a variable transformer and is used primarily for the rapid and accurate transmission of data among equipments and stations.
NEETS MODULE 15-Principles of Synchros, Servos, and Gyros UNCLASSIFIED
A-6 UNCLASSIFIED SYNCHRO CAPACITOR—A unit containing three delta -connected capacitors. The synchro capacitor is used in synchro systems to increase the system's accuracy by cancelling or reducing phase shift introduced by synchro inductance.
SYNCHRO SYSTEM— Two or more synchros interconnected electrically. The system is used to transmit data among equipments and stations.
SYNCHRO TESTER—A synchro receiver with a calibrated dial. This receiver is used primarily for locating defective synchros. It can also be used for zeroing synchros.
SYNCHRO TROUBLESHOOTING— The locating or diagnosing of synchro malfunctions or breakdowns by means of systematic checking or analysis.
SYNCHRONIZING NETWORK—A circuit used in servo systems, also called a crossover or switching network, to sense how far the load is from the point of correspondence and then functions to switch the appropriate signal into control.
TACHOMETER—A small ac or dc generator, sometimes referred to as a rate generator, which converts its shaft speed into an electrical output. The tachometer is frequently used in servo systems to sense the velocity of a load.
TIME LAG—The delay in a servo system between the application of the input signal and the actual movement of the load.
TORQUE—A measure of how much load a machine can turn. This measurement is expressed either in ounce-inches for torque synchro systems or in pound-feet for heavy machinery.
TORQUE DIFFERENTIAL RECEIVER (TDR)—A type of differential synchro that takes two electrical inputs, one to the rotor and one to the stator, and produces a mechanical output. The output is the angular position of the rotor, which represents the algebraic sum or difference of the two electrical inputs.
TORQUE DIFFERENTIAL SYNCHRO SYSTEM—A synchro system containing either a TDX or a TDR. This system is used in application where it is necessary to compare two signals, add or subtract the signals, and furnish an output proportional to the sum or difference between the two signals.
TORQUE DIFFERENTIAL TRANSMITTER (TDX)—A synchro that is functionally the same as the CDX except that it is used in torque systems rather than control systems.
TORQUE RECEIVER (TR)—A type of synchro that converts the electrical input supplied to its stator back to a mechanical angular output through the movement of its rotor.
TORQUE SYNCHRO SYSTEM—A synchro system that uses torque synchros to mov e light loads such as dials, pointers, and other similar devices.
NEETS MODULE 15-Principles of Synchros, Servos, and Gyros UNCLASSIFIED
A-7 UNCLASSIFIED TORQUE TRANSMITTER (TX)—A synchro that is functionally the same as the CX except that it is used in torque synchro systems.
TORQUE VECTOR—In a gyro, a vector representing the rotary motio n applied to change the direction of the rotor axis. The torque vector represents the axis about which the applied force is felt.
TRANSLATION— In a gyro, a force acting through the center of gravity of the gyro that causes no torque on the gyro rotor. Translation forces do not change the angle of the plane of rotation but move the gyroscope as a unit.
TROUBLE INDICATORS—Signal lights used to aid maintenance personnel in locating synchro troubles quickly.
TROUBLE TABLES— Tables of trouble symptoms and probable causes furnished by many manufacturers, with their equipment, to help technicians isolate synchro problems.
VELOCITY SERVO SYSTEM—A servo system that controls the speed of the load it is driving.
X-AXIS— In a gyro, the spin axis of the gyro.
Y-AXIS— In a gyro, an axis through the center of gravity and perpendicular to the spin axis.
Z-AXIS— In a gyro, an axis through the center of gravity and mutually perpendicular to both the spin (X) and Y axes.
ZEROING—The process of adjusting a synchro to its el ectrical zero position.