US3707721A - Servo control system - Google Patents
Servo control system Download PDFInfo
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- US3707721A US3707721A US460295A US46029554A US3707721A US 3707721 A US3707721 A US 3707721A US 460295 A US460295 A US 460295A US 46029554 A US46029554 A US 46029554A US 3707721 A US3707721 A US 3707721A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/02—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical movement of antenna or antenna system as a whole
- H01Q3/08—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical movement of antenna or antenna system as a whole for varying two co-ordinates of the orientation
- H01Q3/10—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical movement of antenna or antenna system as a whole for varying two co-ordinates of the orientation to produce a conical or spiral scan
Definitions
- the present invention relates to servo control systems, and in particular to a servo system for controlling a hemispherical search antenna.
- the present invention is related to the above-mentioned application and is chiefly concerned with a servo-controlled directive antenna for spirally searching the hemisphere as quickly as possible'and with uniform coverage of eachelement of space to insure early detection of the presence of targets.
- the principal object of the present invention is to provide a highly efficient, rapid scanning hemispherical search antenna system.
- Another object of the invention is to provide a directive antenna system for spirally searching the hemisphere in a minimum of time.
- Still another object is to provide a search antenna system that is uniformly responsive to each element of space in a hemisphere.
- a directive antenna system for spirally scanning a hemisphere including a servo system for controlling the rotation of the directive antenna about a vertical axis, and a servo system for controlling the oscillation of the antenna in elevation.
- the speed of rotation and the rate of oscillation of the antenna is varied according to the secant of the elevation angle as the elevation angle varies over a range from to approximately 75.
- a limit switch is provided to reverse the direction of motion of the elevation servo system when the elevation angle is equal to approximately 75 and again when the elevation angle is equal to 0 to produce the desired oscillation of the pointing axis of the antenna.
- FIG. 1 illustrates a block diagram of the servo-controlled hemispherical search antenna system of the present invention
- FIG. 2 is a curve of the secant of the elevation angle of the antenna system
- FIG. 3 is a representation of a beam spirally scanning a hemisphere.
- antenna housing 11 mounted on shaft 12 is supported by'yoke 13.
- the antenna housing 11 may contain a directive paraboloidal radar antenna or a suitable infra-red antenna and detector element.
- a worm wheel 14 is attached to one end of shaft 12 and is driven by worm gear 15 and shaft 16 to vary the directive axis of the antenna in elevation about the horizontal axis definedby shaft 12.
- Shaft 16 is coupled in driving relation to shaft 17 through spur gears 18 and 19 respectively.
- Yoke 13 is mounted on a circular platform 20 whose rim contains teeth engaged with spur gear 21.
- the spur gear 21 is driven by shaft 22 to rotate platform 20 and housing 11 about a vertical axis coinciding with the longitudinal axis of shaft 17.
- a two-phase elevation servomotor 23 coupled to a threaded shaft 24 drives shaft 17 through a differential 25.
- a two-phase azimuth servomotor 26 coupled to shaft 27 drives shaft 22 through bevel gears 28 and 29, and drives shaft 17 through the differential 25.
- the differential 25 prevents the rotation of shaft 16, and accordingly themovement of the directive axis of the antenna in elevation, as the azimuth servomotor drives the platform 20 and antenna housing 11 about a vertical axis.
- the movement of the housing 11 in elevation about the horizontal axis defined by shaft 12, and hence the directive axis of the antenna in elevation is varied according to the magnitude andphase of acontrol voltage supplied to elevation servomotor 23.
- The. speed of rotation of antenna housing 11 about the vertical axis varies according to the magnitude of a control voltage supplied to azimuth servomotor 26.
- Wiper arm 30 of a secant potentiometer 31 is coupled by shaft 32 and bevel gears 33 and 34 to the threaded shaft 24.
- the winding of the secant potentiometer is supplied with an alternating voltage of constant magnitude obtained from a manually adjustable potentiometer 35.
- Potentiometer 35 is supplied with an alternating voltage e, obtained from an external reference generator.
- Resistor 36 cooperates with the secant potentiometer 31 to provide a finite output voltage between the wiper arm of the secant potentiometer and ground when the arm is situated at one end of its range of travel.
- the alternating output voltage between the wiper arm 30 and ground is supplied to the input of elevation servo amplifier 37 and to the input of azimuth servo amplifier 38.
- a cross-field eddy current generator 39 is coupled through spur gears 40, 41, 42, and 43 to the threaded shaft 24.
- the generator produces an alternating output voltage at the frequency of the reference voltage e,.
- the magnitude of the generated voltage varies accord ing to the speed of rotation of shaft 24 coupled to servomotor 23, and the phase of the generated voltage depends upon the direction of rotation of shaft 24.
- a cross-field eddy current generator 44 is coupled through spur gears 45, 46, 47, and 48 to shaft 27.
- the alternating output voltage from generator 44 varies in magnitude according to the speed of rotation of shaft 27 coupled to azimuth servomotor 26.
- the alternating output voltage from generator 39 is applied as a speed feedback voltage to the input of elevation servo amplifier 37 in phase opposition to the alternating voltage obtained from the secant potentiometer 31.
- the difference voltage is amplified by the elevation servo amplifier, and is supplied through a reversing switch 47 to the input of elevation servomotor 23.
- the phase of this difference voltage is established by the larger of the two opposing applied voltages.
- the speed feedback voltage is employed to insure that the speed of the elevation servomotor is controlled according to the magnitude of the alternating voltage obtained from the secant potentiometer.
- Reversing switch 49 is actuated by the guided nut ,50
- the alternating output voltage from the eddy current generator 44 is applied as a feedback voltage to the input of azimuth servo amplifier 38 in phase opposition to the voltage obtained from secant potentiometer 31'.
- the difference voltage is amplified by azimuth servo amplifier 38 and supplied to azimuth servomotor 26.
- the speed of elevation servomotor 23 and azimuth servo-motor 26 is determined by the magnitude of the alternating control voltage applied to these servomotors.
- the magnitude of the applied voltage varies according to the secant of the elevation angle of the antenna as illustrated in FIG. 2. Accordingly, as the directive axis of the antenna moves to search the hemisphere, it moves faster in both azimuth and elevation as the directive axis approaches the zenith.
- the control of the speed of the antenna as a function of the secant of the elevation angle provides uniform coverage of each element ofspace in a hemisphere in a minimum of time.
- This may be understood by referring to the representation of a beam spirally searching a hemisphere illustrated in FIG. 3.
- the peripheral scanning speed of the beam on the imaginary surface of the hemisphere at the horizon is determined by the angular velocity of the beam about the vertical axis and the diameter of the hemisphere.
- the peripheral distance covered for each revolution of the beam is reduced according to the cosine of the elevation angle. Accordingly, with a constant angular velocity about the vertical axis, the peripheral scanning speed is reduced as the elevation angle increases.
- the angular velocity of the beam must be varied according to the inverse of the cosine of the elevation angle, or according to the secant of the elevation angle. For example, the angular velocity of the beam about the vertical axis at an elevation angle of 60 must be twice the angular velocity at the horizon since the beam will have only one-half the peripheral distance to scan.
- the angular velocity will be almost four times the angular velocity at the horizon in order to maintain a constant peripheral speed in azimuth.
- the angular velocity must be varied according to the casecant of the angle between the directive axis of the antenna and the vertical axis.
- the time required for the beam to rotate about the vertical axis reduces. Accordingly, to maintain a constant overlap of the swaths of the beam, it is necessary to increase the scanning speed in elevation as the scanning speed in azimuth increases. Thus, the directive axis must be moved in elevation at a speed proportional to the secant of the instantaneous elevation angle.
- the azimuth and elevation scanning speeds needed to search a hemisphere are determined by the width in elevation of the scanningbeam, the amount of overlap of the swaths, and the speed capabilitiesof the two servo systems.
- the beam searches 2.4 in elevation for each revolution in azimuth.
- the azimuth scanning speed must be fasterthan the elevationscanning speedin the ratio of 360 to 2.4, i.e., 150:1. .This ratio of scanning speeds remains constant at all'elevation' angles.
- the azimuth scanning speed will be a maximum at this elevation angle and will be limited by the speed capabilities of the azimuth servo system.
- the elevation scanning speed is determined by dividing the azimuth scanning speed by 150. The scanning speeds reduce as the elevation angle reduces in accordance with'the secant of the elevation angle, as illustrated in FIG. 2.
- the present invention accomplishes the desired hemispherical search up to elevation angles of approximately 75. Since the secant of the elevation angle approaches infinity at the zenith, it is not possible to scan the entire hemisphere according to the secant of the elevation angle.
- a servo system for controlling the scanning speed of a directive hemispherical search antenna comprising in combination, first servomotor means adapted to be coupled to said antenna for rotating said antenna about a vertical axis whereby to rotate the directive axis thereof in azimuth, the speed of rotation of said antenna varying according to the magnitude of a voltage supplied to said first servomotor means, second ser' vomotor means adapted to be coupled to said antenna for rotating said antenna about a horizontal axis whereby to rotate the directive axis thereof in elevation, the movement of said antenna about said horizontal axis varying according to the magnitude of a voltage supplied to said second servomotor means, means coupled'to said second servomotor means and responsive to the movement of said antenna about said horizontal axis, said means receiving an applied voltage of con- 'stant magnitude and supplying an output voltage varysecant of the elevation angle of said antenna, reversing switch means coupled to said second servomotor means and responsive to the movement of said antenna about said horizontal axis,
- a shaft adapted to be rotated about a vertical axis and whose angular position is adapted to be oscillated about its longitudinal axis, the longitudinal axis of said shaft extending perpendicular to said vertical axis, first servomotor means coupled to said shaft for rotating said shaft about said vertical axis in response to an applied signal, the rotational speed of said shaft varying according to the magnitude of said applied signal, second servomotor means coupled to said shaft for varying the angular position thereof about its longitudinal axis in response to an applied signal, the movement in angular position of said shaft varying according to the magnitude of an applied signal, means coupled to said shaft for movement therewith about its longitudinal axis, said means receiving an input signal of fixed magnitude and providing an'output signal varying in magnitude according to the secant function of the angular position of said shaft about its longitudinal axis, means coupling said output signal to saidfirst servomotor means for varying the movement of said shaft about said vertical axis in accordance with said secant
- a directive antenna adapted to be rotated in azimuth about a vertical axis and whose directive axis is adapted to be varied in elevation about a horizontal axis, whereby said directive axis may be controlled spirally to scan a hemisphere
- first servomotor means coupled to said directive antenna for rotating said antenna about said vertical axis, the speed of rotation of said antenna varying according to the magnitude of an applied voltage
- second servomotor means coupled to said antenna for varying the directive axis thereof in elevation
- the movement of the directive axis of said antenna in elevation varying according to the magnitude of an applied voltage
- a directive antenna adapted to be rotated about a first axisxand whose directive axis is adapted to be varied about a second axis perpendicular to said first axis, the directive axis of said antenna extending perpendicular to said second axis, first servomotor means coupled to said directive antenna forv rotating said antenna about said first axis, the speed of rotation of said antenna varying according to the magnitude of an applied signal, second servomotor means coupled to said antenna for varying the directive axis of said antenna about said second axis, the movement of the directive axis of said antenna about said second axis varying according to the magnitude of an applied signal, means responsive to movement of said directive axis about said second axis for providing an output signal varying in magnitude according to the cosecant of the angle between said first axis and the directive axis of said antenna, and means applying said output voltage to said first and second servomotor means.
- the apparatus as defined in claim 5 further comprising means coupled to said body and responsive to the angular movement thereof about said second axis, said means being coupled to said second servomotor means for periodically reversing the direction of rotation of said second servomotor when the angular movement of said body about said second axis varies through a predetermined angle less than 7.
- second servomotor means coupled to said body .
- the servo control system as defined in claim 7 further comprising means coupled to said body and responsive to the angular movement thereof about said second axis for periodically reversing the direction of rotation of said second servomotor means when the angular movement of said body about said second axis varies through a predetermined angular range.
- a body adapted to be moved about a first axis and about a second axis perpendicular to said first axis
- servomotor means coupled to said body for varying the movement thereof about said first and second axesaccording to the speed of said servomotor means, the movement of said body about said first axis being appreciably faster than the movement thereof about said second axis
- means coupled to said body and responsive to the movement thereof about said second axis for varying the speed of said servomotor means, said means varying the speed of said servomotor means according to the cosecant function of the angle of movement of said body about said second axis relative to said first axis whereby to control the movement of said body about both said first and second axes in accordance with said cosecant function.
- a body adapted to be moved 7 about first and second mutually perpendicular axes
- servomotor means coupled to said body for varying the movement thereof about said second axis
- means coupled to said body and responsive to the movement thereof about said second axis for varying the speed of said servomotor means according to the cosecant function of the angle of movement of said body about said second axis relative to said first axis whereby to vary the speed of movement of said body about said second axis in accordance with said cosecant function.
- a first signalresponsive servomotor means for continuously rotating said antenna in azimuth
- a second signal-responsive ser vomotor means for cyclically, rotating said antenna in elevation between predetermined angular limits, the speed of continuous rotation of said antenna in azimuth being substantially greater than the cyclic speed of rotation of said antenna in elevation whereby the directive axis of said antenna is caused spirally to scan a hemisphere
- means for supplying said signalvto said second servomotor for continuously varying the speed of rotation of said antenna between said angular limits in elevation in accordance with said signal whereby to cause said an tenna uniformly to scan each element of space in said hemisphere in a minimum of scanning time in
- a first single-responsive means for continuously rotating the directive axis of said antenna in azimuth in the same direction a second signal responsive means for cyclically rotating the directive axis of said antenna in elevation between predetermined angueach cycle of rotation thereof in elevation, means for supplying said signal to said first means thereby continuously to vary the speed of rotation of said directive axis in azimuth in ace rdance with s aid signal, and means for simultaneous y supplying said signal to said second means for continuously varying the speed of rotation of said directive axis between said angular limits in elevation in accordance with said signal whereby to cause said directive axis uniformly to scan each element of space in said hemisphere in a minimum of scanning time in elevation.
Abstract
1. A servo system for controlling the scanning speed of a directive hemispherical search antenna, comprising in combination, first servomotor means adapted to be coupled to said antenna for rotating said antenna about a vertical axis whereby to rotate the directive axis thereof in azimuth, the speed of rotation of said antenna varying according to the magnitude of a voltage supplied to said first servomotor means, second servomotor means adapted to be coupled to said antenna for rotating said antenna about a horizontal axis whereby to rotate the directive axis thereof in elevation; the movement of said antenna about said horizontal axis varying according to the magnitude of a voltage supplied to said second servomotor means, means coupled to said second servomotor means and responsive to the movement of said antenna about said horizontal axis, said means receiving an applied voltage of constant magnitude and supplying an output voltage varying in magnitude according to the secant of the elevation angle of said antenna, means coupling said output voltage to said first servomotor means for varying the speed of said first servomotor means according to the secant of the elevation angle of said antenna, reversing switch means coupled to said second servomotor means and responsive to the movement of said antenna about said horizontal axis, means coupling said output voltage varying according to the secant of said elevation angle to said reversing switch means, and means coupling the voltage from said reversing switch means to said second servomotor means for varying the speed of said second servomotor means according to the secant of the elevation angle of said antenna, said second servomotor means and said reversing switch means causing the elevation angle of said antenna to oscillate about said horizontal axis through an angle less than 90*.
Description
United States Patent McCartney ,{451 Dec.26, 1972 [54] SERVO CONTROL SYSTEM [72] Inventor: Earl J. McCartney, Rockville Center, N.Y.
[73] Assignee: The Sperry Rand Corp., Great Neck, N.Y.
[22] Filed: Oct. 5, 1954 [21] 'App1.No.: 460,295
[52] Cl. ....343/759, 343/766, 318/625, 318/627 [51] Int. Cl. ..H01q 3/10 [58] Field of Search ..318/ 19, 282, 286, 466-468, 318/625, 627; 250/33.65l; 343/117, 759
561 References Cited UNITED STATES PATENTS 2,515,248 7/1950 McCoy..... ....34s/ 117 2,648,040 8/1953 Schneide ....3l8/286 Primary Examiner-Benjamin A. Borchelt Assistant Examiner-R. Kinberg Attorney-Reginald V. Craddock EXEMPLARY CLAIM axis-thereof in azimuth, the speed of rotation of said antenna varying according to the magnitude of a volt age supplied to said first servomotor'means, second servomotor means adapted to be coupled to said antenna for rotating said antenna about a horizontal axis whereby to rotate the directive axis thereof in elevation; the movement of said antenna about said horizontal axis varying according to the magnitude of a voltage supplied to said second servomotor means, means coupled to said second servomotor means and responsive to the movement of said antenna about said horizontal axis, said means receiving an applied voltage of constant magnitude and supplying an output voltage varying in magnitude according to the secant of the elevation angle of said antenna, means coupling said output voltage to said first servomotor means for varying the speed of said first servomotor means according to the secant of the elevation angle of said antenna, reversing switch means coupled to said second servomotor means and responsive to the movement of said antenna about said horizontal axis, means coupling said output voltage varying according to the secant of said elevation angle to said reversing 12 Claims, 3 Drawing Figures 16 I3 39 w 20 19 as Z/ /5 4 M GEN. s: a/z 1 4 417 i 4 ,7 er
.42. an 0/: SERVO as m 23 R ta eggs 33 5 27 26 SERVO CONTROL SYSTEM The present invention relates to servo control systems, and in particular to a servo system for controlling a hemispherical search antenna.
ln pending application Ser. No. 517,008, filed Jan. 5, 1944, now U.S. Pat. No. 2,784,402, issued Mar. 5, 1957, in the names of G. E. White and D. S. Pensyl, en-
titled Control-Systemsf and assigned to the same as- I signee as the present invention, there is described and claimed a'servo-controlled tracking antenna system in which the response of the servo system controlling the antenna in azimuth varies according to the secant of the elevation angle of the directive axis'of the antenna. This servo-controlled antenna system provides improved automatic tracking by compensating the azimuth servo control system for the loss in angular sensitivity of the azimuth error detector at high elevation angles of the directive antenna. j
The present invention is related to the above-mentioned application and is chiefly concerned with a servo-controlled directive antenna for spirally searching the hemisphere as quickly as possible'and with uniform coverage of eachelement of space to insure early detection of the presence of targets.
Accordingly, the principal object of the present invention is to provide a highly efficient, rapid scanning hemispherical search antenna system.
Another object of the invention is to provide a directive antenna system for spirally searching the hemisphere in a minimum of time.
Still another object is to provide a search antenna system that is uniformly responsive to each element of space in a hemisphere.
In accordance with the present invention there is introduced a directive antenna system for spirally scanning a hemisphere including a servo system for controlling the rotation of the directive antenna about a vertical axis, and a servo system for controlling the oscillation of the antenna in elevation. To achieve the objects of the invention the speed of rotation and the rate of oscillation of the antenna is varied according to the secant of the elevation angle as the elevation angle varies over a range from to approximately 75. A limit switch is provided to reverse the direction of motion of the elevation servo system when the elevation angle is equal to approximately 75 and again when the elevation angle is equal to 0 to produce the desired oscillation of the pointing axis of the antenna.
The above objects of and the brief introduction to the present invention will be more fully understood and further objects and advantages will become apparent from a study of the following detailed description in connection with the drawing, wherein,
FIG. 1 illustrates a block diagram of the servo-controlled hemispherical search antenna system of the present invention,
FIG. 2 is a curve of the secant of the elevation angle of the antenna system, and
FIG. 3 is a representation of a beam spirally scanning a hemisphere.
Referring to FIG. 1, antenna housing 11 mounted on shaft 12 is supported by'yoke 13. The antenna housing 11 may contain a directive paraboloidal radar antenna or a suitable infra-red antenna and detector element. A worm wheel 14 is attached to one end of shaft 12 and is driven by worm gear 15 and shaft 16 to vary the directive axis of the antenna in elevation about the horizontal axis definedby shaft 12. Shaft 16 is coupled in driving relation to shaft 17 through spur gears 18 and 19 respectively. Yoke 13 is mounted on a circular platform 20 whose rim contains teeth engaged with spur gear 21. The spur gear 21 is driven by shaft 22 to rotate platform 20 and housing 11 about a vertical axis coinciding with the longitudinal axis of shaft 17.
I A two-phase elevation servomotor 23 coupled to a threaded shaft 24 drives shaft 17 through a differential 25. A two-phase azimuth servomotor 26 coupled to shaft 27 drives shaft 22 through bevel gears 28 and 29, and drives shaft 17 through the differential 25. The differential 25 prevents the rotation of shaft 16, and accordingly themovement of the directive axis of the antenna in elevation, as the azimuth servomotor drives the platform 20 and antenna housing 11 about a vertical axis. The movement of the housing 11 in elevation about the horizontal axis defined by shaft 12, and hence the directive axis of the antenna in elevation, is varied according to the magnitude andphase of acontrol voltage supplied to elevation servomotor 23. The. speed of rotation of antenna housing 11 about the vertical axis varies according to the magnitude of a control voltage supplied to azimuth servomotor 26.
A cross-field eddy current generator 39 is coupled through spur gears 40, 41, 42, and 43 to the threaded shaft 24. The generator produces an alternating output voltage at the frequency of the reference voltage e,. The magnitude of the generated voltage varies accord ing to the speed of rotation of shaft 24 coupled to servomotor 23, and the phase of the generated voltage depends upon the direction of rotation of shaft 24. Similarly, a cross-field eddy current generator 44 is coupled through spur gears 45, 46, 47, and 48 to shaft 27. The alternating output voltage from generator 44 varies in magnitude according to the speed of rotation of shaft 27 coupled to azimuth servomotor 26.
The alternating output voltage from generator 39 is applied as a speed feedback voltage to the input of elevation servo amplifier 37 in phase opposition to the alternating voltage obtained from the secant potentiometer 31. The difference voltage is amplified by the elevation servo amplifier, and is supplied through a reversing switch 47 to the input of elevation servomotor 23. The phase of this difference voltage is established by the larger of the two opposing applied voltages. The speed feedback voltage is employed to insure that the speed of the elevation servomotor is controlled according to the magnitude of the alternating voltage obtained from the secant potentiometer.
on threaded shaft 24 at each extreme of its'travel to reverse the phase of the amplified output voltage applied to elevation servomotor 23, and, accordingly, the direction of rotation of shaft 24. This phase reversal occurs when the elevation angle of the directive axis is approximately and 75. Accordingly, the directive axis of the antenna oscillates in elevation between the angles of approximately 0 and 75.
The alternating output voltage from the eddy current generator 44 is applied as a feedback voltage to the input of azimuth servo amplifier 38 in phase opposition to the voltage obtained from secant potentiometer 31'. The difference voltage is amplified by azimuth servo amplifier 38 and supplied to azimuth servomotor 26.
The speed of elevation servomotor 23 and azimuth servo-motor 26 is determined by the magnitude of the alternating control voltage applied to these servomotors. The magnitude of the applied voltage varies according to the secant of the elevation angle of the antenna as illustrated in FIG. 2. Accordingly, as the directive axis of the antenna moves to search the hemisphere, it moves faster in both azimuth and elevation as the directive axis approaches the zenith.
The control of the speed of the antenna as a function of the secant of the elevation angle provides uniform coverage of each element ofspace in a hemisphere in a minimum of time. This may be understood by referring to the representation of a beam spirally searching a hemisphere illustrated in FIG. 3. The peripheral scanning speed of the beam on the imaginary surface of the hemisphere at the horizon is determined by the angular velocity of the beam about the vertical axis and the diameter of the hemisphere. As the axis of the scanning beam is increased in elevation, the peripheral distance covered for each revolution of the beam is reduced according to the cosine of the elevation angle. Accordingly, with a constant angular velocity about the vertical axis, the peripheral scanning speed is reduced as the elevation angle increases. To achieve uniform coverage of each element of space in a hemisphere it is desirable to scan each element of area on the imaginary surface of the hemisphere in the same amount of time. ln other words, it is desirable to provide-a constant peripheral scanning speed of the beam rather than a constant angular'velocity about the vertical axis. To provide a constant peripheral scanning speed in azimuth, the angular velocity of the beam must be varied according to the inverse of the cosine of the elevation angle, or according to the secant of the elevation angle. For example, the angular velocity of the beam about the vertical axis at an elevation angle of 60 must be twice the angular velocity at the horizon since the beam will have only one-half the peripheral distance to scan. At an elevation angle of 75, the angular velocity will be almost four times the angular velocity at the horizon in order to maintain a constant peripheral speed in azimuth. Expressed differently, the angular velocity must be varied according to the casecant of the angle between the directive axis of the antenna and the vertical axis.
With the higher angular velocities provided as the directiveaxis of the antenna approaches the zenith, the time required for the beam to rotate about the vertical axis reduces. Accordingly, to maintain a constant overlap of the swaths of the beam, it is necessary to increase the scanning speed in elevation as the scanning speed in azimuth increases. Thus, the directive axis must be moved in elevation at a speed proportional to the secant of the instantaneous elevation angle.
The azimuth and elevation scanning speeds needed to search a hemisphere are determined by the width in elevation of the scanningbeam, the amount of overlap of the swaths, and the speed capabilitiesof the two servo systems. With a scanning beam having a 3 width in elevation and a 20 percent overlap of the swaths, the beam searches 2.4 in elevation for each revolution in azimuth. Accordingly, the azimuth scanning speed must be fasterthan the elevationscanning speedin the ratio of 360 to 2.4, i.e., 150:1. .This ratio of scanning speeds remains constant at all'elevation' angles. For a selected upper elevation angular limit of 7 5, the azimuth scanning speed will be a maximum at this elevation angle and will be limited by the speed capabilities of the azimuth servo system. Once the azimuth scanning speed at this elevation angle is chosen, the elevation scanning speed is determined by dividing the azimuth scanning speed by 150. The scanning speeds reduce as the elevation angle reduces in accordance with'the secant of the elevation angle, as illustrated in FIG. 2.
The present invention accomplishes the desired hemispherical search up to elevation angles of approximately 75. Since the secant of the elevation angle approaches infinity at the zenith, it is not possible to scan the entire hemisphere according to the secant of the elevation angle.
Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
What is claimed is:
l. A servo system for controlling the scanning speed of a directive hemispherical search antenna, comprising in combination, first servomotor means adapted to be coupled to said antenna for rotating said antenna about a vertical axis whereby to rotate the directive axis thereof in azimuth, the speed of rotation of said antenna varying according to the magnitude of a voltage supplied to said first servomotor means, second ser' vomotor means adapted to be coupled to said antenna for rotating said antenna about a horizontal axis whereby to rotate the directive axis thereof in elevation, the movement of said antenna about said horizontal axis varying according to the magnitude of a voltage supplied to said second servomotor means, means coupled'to said second servomotor means and responsive to the movement of said antenna about said horizontal axis, said means receiving an applied voltage of con- 'stant magnitude and supplying an output voltage varysecant of the elevation angle of said antenna, reversing switch means coupled to said second servomotor means and responsive to the movement of said antenna about said horizontal axis, means coupling said output voltage varying according to the secant of said elevation angle to said reversing switch means, and means coupling the voltage from said reversing switch means servomotor means and said reversing switch means causing the elevation angle of said antenna to oscillate about said horizontal axis through an angle less than 90.
2. In combination, .a shaft adapted to be rotated about a vertical axis and whose angular position is adapted to be oscillated about its longitudinal axis, the longitudinal axis of said shaft extending perpendicular to said vertical axis, first servomotor means coupled to said shaft for rotating said shaft about said vertical axis in response to an applied signal, the rotational speed of said shaft varying according to the magnitude of said applied signal, second servomotor means coupled to said shaft for varying the angular position thereof about its longitudinal axis in response to an applied signal, the movement in angular position of said shaft varying according to the magnitude of an applied signal, means coupled to said shaft for movement therewith about its longitudinal axis, said means receiving an input signal of fixed magnitude and providing an'output signal varying in magnitude according to the secant function of the angular position of said shaft about its longitudinal axis, means coupling said output signal to saidfirst servomotor means for varying the movement of said shaft about said vertical axis in accordance with said secant function, reversing switch means coupled to said shaft and responsive to its angular position, means coupling said output signal to said reversing switch means, and means coupling the signal from said reversing switch means to said second servo motor means, said second servomotor means and said reversing switch means causing the angular position of said shaft to oscillate about its longitudinal axis the oscillatory movement thereof about its longitudinal axis also varying in accordance with said secant-function.
3. ln combination, a directive antenna adapted to be rotated in azimuth about a vertical axis and whose directive axis is adapted to be varied in elevation about a horizontal axis, whereby said directive axis may be controlled spirally to scan a hemisphere, first servomotor means coupled to said directive antenna for rotating said antenna about said vertical axis, the speed of rotation of said antenna varying according to the magnitude of an applied voltage, second servomotor means coupled to said antenna for varying the directive axis thereof in elevation, the movement of the directive axis of said antenna in elevation varying according to the magnitude of an applied voltage, means responsive to movement of the directive axis of said antenna in elevation and receiving an applied voltage of constant magnitude for providing an output voltage varying in magnitude according to the secant of the elevation angle of thedirective axis of said antenna, and means supplying said outputvoltage to said first and second servomotor means for respectively controlling the speeds thereof in accordance with said output voltage.
4. In combination, a directive antenna adapted to be rotated about a first axisxand whose directive axis is adapted to be varied about a second axis perpendicular to said first axis, the directive axis of said antenna extending perpendicular to said second axis, first servomotor means coupled to said directive antenna forv rotating said antenna about said first axis, the speed of rotation of said antenna varying according to the magnitude of an applied signal, second servomotor means coupled to said antenna for varying the directive axis of said antenna about said second axis, the movement of the directive axis of said antenna about said second axis varying according to the magnitude of an applied signal, means responsive to movement of said directive axis about said second axis for providing an output signal varying in magnitude according to the cosecant of the angle between said first axis and the directive axis of said antenna, and means applying said output voltage to said first and second servomotor means.
I 5. in combination, a body adapted to be moved about a first axis and about a second axis perpendicular to said first axis, first servomotor means coupled to said body for varying the movement thereof about'said first axis according to the speed of said first servomotor, second servomotor means coupled to said body for varying the movement thereof about said second axis according to the speed of said second servomotor, and means coupled to said body and responsive to the movement thereof about said second axis, said lastmentioned means being further coupled to said first and second servomotor means for varying the speeds of both said first and second servomotors in accordance with'the cosecant of the angle of movement of said body about said second axis relative to said first axis.
6. The apparatus as defined in claim 5 further comprising means coupled to said body and responsive to the angular movement thereof about said second axis, said means being coupled to said second servomotor means for periodically reversing the direction of rotation of said second servomotor when the angular movement of said body about said second axis varies through a predetermined angle less than 7. A servo control system for moving a body about first and second, mutually perpendicular axes according to its motion about said second axis, comprising in combination, a first servomotor means coupled to said body for varying the movement thereof about said first axis according to the speed of said first servomotor,
second servomotor means coupled to said body .for
varying the movement thereof about said second axis according to the speed of said second servomotor, and means coupled to said second servomotor means and responsive to the movement of said body about said second axis for varying the speed of said first and second servomotors, the speed of said first and second servomotors varying according to the cosecant of the angle of movement of said body about said second axis relative to said first axis.
8. The servo control system as defined in claim 7 further comprising means coupled to said body and responsive to the angular movement thereof about said second axis for periodically reversing the direction of rotation of said second servomotor means when the angular movement of said body about said second axis varies through a predetermined angular range.
9. In combination, a body adapted to be moved about a first axis and about a second axis perpendicular to said first axis, servomotor means coupled to said body for varying the movement thereof about said first and second axesaccording to the speed of said servomotor means, the movement of said body about said first axis being appreciably faster than the movement thereof about said second axis, and means coupled to said body and responsive to the movement thereof about said second axis for varying the speed of said servomotor means, said means varying the speed of said servomotor means according to the cosecant function of the angle of movement of said body about said second axis relative to said first axis whereby to control the movement of said body about both said first and second axes in accordance with said cosecant function.
10. In combination, a body adapted to be moved 7 about first and second mutually perpendicular axes, servomotor means coupled to said body for varying the movement thereof about said second axis, and means coupled to said body and responsive to the movement thereof about said second axis for varying the speed of said servomotor means according to the cosecant function of the angle of movement of said body about said second axis relative to said first axis whereby to vary the speed of movement of said body about said second axis in accordance with said cosecant function.
11. In a scanning system for an antenna, a first signalresponsive servomotor means for continuously rotating said antenna in azimuth, a second signal-responsive ser vomotor means for cyclically, rotating said antenna in elevation between predetermined angular limits, the speed of continuous rotation of said antenna in azimuth being substantially greater than the cyclic speed of rotation of said antenna in elevation whereby the directive axis of said antenna is caused spirally to scan a hemisphere, means for continuously producing a signal proportional within predetermined angular limits to the secant of the angle of elevation of said antenna during each cycle of rotation thereof in elevation, means for supplying said signal to said first servomotor thereby continuously to vary the speed of rotation of said antenna in azimuth in accordance with said signal, and means for supplying said signalvto said second servomotor for continuously varying the speed of rotation of said antenna between said angular limits in elevation in accordance with said signal whereby to cause said an tenna uniformly to scan each element of space in said hemisphere in a minimum of scanning time in eleva-- tion.
12. In a scanning system by means of which the directive axis of an antenna may be caused to scan a hemisphere, a first single-responsive means for continuously rotating the directive axis of said antenna in azimuth in the same direction, a second signal responsive means for cyclically rotating the directive axis of said antenna in elevation between predetermined angueach cycle of rotation thereof in elevation, means for supplying said signal to said first means thereby continuously to vary the speed of rotation of said directive axis in azimuth in ace rdance with s aid signal, and means for simultaneous y supplying said signal to said second means for continuously varying the speed of rotation of said directive axis between said angular limits in elevation in accordance with said signal whereby to cause said directive axis uniformly to scan each element of space in said hemisphere in a minimum of scanning time in elevation.
nnnn Us
Claims (12)
1. A servo system for controlling the scanning speed of a directive hemispherical search antenna, comprising in combination, first servomotor means adapted to be coupled to said antenna for rotating said antenna about a vertical axis whereby to rotate the directive axis thereof in azimuth, the speed of rotation of said antenna varying according to the magnitude of a voltage supplied to said first servomotor means, second servomotor means adapted to be coupled to said antenna for rotating said antenna about a horizontal axis whereby to rotate the directive axis thereof in elevation, the movement of said antenna about said horizontal axis varying according to the magnitude of a voltage supplied to said second servomotor means, means coupled to said second servomotor means and responsive to the movement of said antenna about said horizontal axis, said means receiving an applied voltage of constant magnitude and supplying an output voltage varying in magnitude according to the secant of the elevation angle of said antenna, means coupling said output voltage to said first servomotor means for varying the speed of said first servomoTor means according to the secant of the elevation angle of said antenna, reversing switch means coupled to said second servomotor means and responsive to the movement of said antenna about said horizontal axis, means coupling said output voltage varying according to the secant of said elevation angle to said reversing switch means, and means coupling the voltage from said reversing switch means to said second servomotor means for varying the speed of said second servomotor means according to the secant of the elevation angle of said antenna, said second servomotor means and said reversing switch means causing the elevation angle of said antenna to oscillate about said horizontal axis through an angle less than 90*.
2. In combination, a shaft adapted to be rotated about a vertical axis and whose angular position is adapted to be oscillated about its longitudinal axis, the longitudinal axis of said shaft extending perpendicular to said vertical axis, first servomotor means coupled to said shaft for rotating said shaft about said vertical axis in response to an applied signal, the rotational speed of said shaft varying according to the magnitude of said applied signal, second servomotor means coupled to said shaft for varying the angular position thereof about its longitudinal axis in response to an applied signal, the movement in angular position of said shaft varying according to the magnitude of an applied signal, means coupled to said shaft for movement therewith about its longitudinal axis, said means receiving an input signal of fixed magnitude and providing an output signal varying in magnitude according to the secant function of the angular position of said shaft about its longitudinal axis, means coupling said output signal to said first servomotor means for varying the movement of said shaft about said vertical axis in accordance with said secant function, reversing switch means coupled to said shaft and responsive to its angular position, means coupling said output signal to said reversing switch means, and means coupling the signal from said reversing switch means to said second servo motor means, said second servomotor means and said reversing switch means causing the angular position of said shaft to oscillate about its longitudinal axis the oscillatory movement thereof about its longitudinal axis also varying in accordance with said secant function.
3. In combination, a directive antenna adapted to be rotated in azimuth about a vertical axis and whose directive axis is adapted to be varied in elevation about a horizontal axis, whereby said directive axis may be controlled spirally to scan a hemisphere, first servomotor means coupled to said directive antenna for rotating said antenna about said vertical axis, the speed of rotation of said antenna varying according to the magnitude of an applied voltage, second servomotor means coupled to said antenna for varying the directive axis thereof in elevation, the movement of the directive axis of said antenna in elevation varying according to the magnitude of an applied voltage, means responsive to movement of the directive axis of said antenna in elevation and receiving an applied voltage of constant magnitude for providing an output voltage varying in magnitude according to the secant of the elevation angle of the directive axis of said antenna, and means supplying said output voltage to said first and second servomotor means for respectively controlling the speeds thereof in accordance with said output voltage.
4. In combination, a directive antenna adapted to be rotated about a first axis and whose directive axis is adapted to be varied about a second axis perpendicular to said first axis, the directive axis of said antenna extending perpendicular to said second axis, first servomotor means coupled to said directive antenna for rotating said antenna about said first axis, the speed of rotation of said antenna varying according to the magnitude of an applied signal, second servomotor means coupled tO said antenna for varying the directive axis of said antenna about said second axis, the movement of the directive axis of said antenna about said second axis varying according to the magnitude of an applied signal, means responsive to movement of said directive axis about said second axis for providing an output signal varying in magnitude according to the cosecant of the angle between said first axis and the directive axis of said antenna, and means applying said output voltage to said first and second servomotor means.
5. In combination, a body adapted to be moved about a first axis and about a second axis perpendicular to said first axis, first servomotor means coupled to said body for varying the movement thereof about said first axis according to the speed of said first servomotor, second servomotor means coupled to said body for varying the movement thereof about said second axis according to the speed of said second servomotor, and means coupled to said body and responsive to the movement thereof about said second axis, said last-mentioned means being further coupled to said first and second servomotor means for varying the speeds of both said first and second servomotors in accordance with the cosecant of the angle of movement of said body about said second axis relative to said first axis.
6. The apparatus as defined in claim 5 further comprising means coupled to said body and responsive to the angular movement thereof about said second axis, said means being coupled to said second servomotor means for periodically reversing the direction of rotation of said second servomotor when the angular movement of said body about said second axis varies through a predetermined angle less than 90*.
7. A servo control system for moving a body about first and second, mutually perpendicular axes according to its motion about said second axis, comprising in combination, a first servomotor means coupled to said body for varying the movement thereof about said first axis according to the speed of said first servomotor, second servomotor means coupled to said body for varying the movement thereof about said second axis according to the speed of said second servomotor, and means coupled to said second servomotor means and responsive to the movement of said body about said second axis for varying the speed of said first and second servomotors, the speed of said first and second servomotors varying according to the cosecant of the angle of movement of said body about said second axis relative to said first axis.
8. The servo control system as defined in claim 7 further comprising means coupled to said body and responsive to the angular movement thereof about said second axis for periodically reversing the direction of rotation of said second servomotor means when the angular movement of said body about said second axis varies through a predetermined angular range.
9. In combination, a body adapted to be moved about a first axis and about a second axis perpendicular to said first axis, servomotor means coupled to said body for varying the movement thereof about said first and second axes according to the speed of said servomotor means, the movement of said body about said first axis being appreciably faster than the movement thereof about said second axis, and means coupled to said body and responsive to the movement thereof about said second axis for varying the speed of said servomotor means, said means varying the speed of said servomotor means according to the cosecant function of the angle of movement of said body about said second axis relative to said first axis whereby to control the movement of said body about both said first and second axes in accordance with said cosecant function.
10. In combination, a body adapted to be moved about first and second mutually perpendicular axes, servomotor means coupled to said body for varying the movement thereof about said second axis, and means coupled to said body and responsive to the movement thereof about said second axis for varying the speed of said servomotor means according to the cosecant function of the angle of movement of said body about said second axis relative to said first axis whereby to vary the speed of movement of said body about said second axis in accordance with said cosecant function.
11. In a scanning system for an antenna, a first signal-responsive servomotor means for continuously rotating said antenna in azimuth, a second signal-responsive servomotor means for cyclically rotating said antenna in elevation between predetermined angular limits, the speed of continuous rotation of said antenna in azimuth being substantially greater than the cyclic speed of rotation of said antenna in elevation whereby the directive axis of said antenna is caused spirally to scan a hemisphere, means for continuously producing a signal proportional within predetermined angular limits to the secant of the angle of elevation of said antenna during each cycle of rotation thereof in elevation, means for supplying said signal to said first servomotor thereby continuously to vary the speed of rotation of said antenna in azimuth in accordance with said signal, and means for supplying said signal to said second servomotor for continuously varying the speed of rotation of said antenna between said angular limits in elevation in accordance with said signal whereby to cause said antenna uniformly to scan each element of space in said hemisphere in a minimum of scanning time in elevation.
12. In a scanning system by means of which the directive axis of an antenna may be caused to scan a hemisphere, a first single-responsive means for continuously rotating the directive axis of said antenna in azimuth in the same direction, a second signal responsive means for cyclically rotating the directive axis of said antenna in elevation between predetermined angular limits, the speed of rotation of said directive axis in azimuth being substantially greater than the cyclic speed of rotation of said directive axis in elevation whereby said directive axis is caused spirally to scan said hemisphere, means for producing a signal proportional within predetermined angular limits to the secant of the angle of elevation of said directive axis during each cycle of rotation thereof in elevation, means for supplying said signal to said first means thereby continuously to vary the speed of rotation of said directive axis in azimuth in accordance with said signal, and means for simultaneously supplying said signal to said second means for continuously varying the speed of rotation of said directive axis between said angular limits in elevation in accordance with said signal whereby to cause said directive axis uniformly to scan each element of space in said hemisphere in a minimum of scanning time in elevation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US460295A US3707721A (en) | 1954-10-05 | 1954-10-05 | Servo control system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US460295A US3707721A (en) | 1954-10-05 | 1954-10-05 | Servo control system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3707721A true US3707721A (en) | 1972-12-26 |
Family
ID=23828122
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US460295A Expired - Lifetime US3707721A (en) | 1954-10-05 | 1954-10-05 | Servo control system |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US3707721A (en) |
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2750401A1 (en) * | 1977-09-30 | 1979-04-12 | Bbc Brown Boveri & Cie | ROTATING ANTENNA SYSTEM, IN PARTICULAR FOR SATELLITE SHIP AND GROUND STATIONS |
| US4504836A (en) * | 1982-06-01 | 1985-03-12 | Seavey Engineering Associates, Inc. | Antenna feeding with selectively controlled polarization |
| US4672385A (en) * | 1984-01-03 | 1987-06-09 | Mel-Du Inc. | Satellite tracking system |
| US5153485A (en) * | 1989-12-28 | 1992-10-06 | Kabushiki Kaisha Shinsangyo Kaihatsu | Biaxial rotary drive unit |
| US5656903A (en) * | 1993-10-01 | 1997-08-12 | The Ohio State University Research Foundation | Master-slave position and motion control system |
| US5852423A (en) * | 1992-09-25 | 1998-12-22 | Agence Spatiale Europeene | Variable pointing antenna mount, suitable for satellite telecommunication antennas |
| US6195060B1 (en) | 1999-03-09 | 2001-02-27 | Harris Corporation | Antenna positioner control system |
| US6204823B1 (en) | 1999-03-09 | 2001-03-20 | Harris Corporation | Low profile antenna positioner for adjusting elevation and azimuth |
| GB2405041A (en) * | 2003-08-14 | 2005-02-16 | Smiths Group Plc | Radar apparatus having an antenna which may be rotated at different speeds |
| US20170025752A1 (en) * | 2015-07-20 | 2017-01-26 | Viasat, Inc. | Hemispherical azimuth and elevation positioning platform |
| US11417112B2 (en) * | 2018-11-27 | 2022-08-16 | Hyundai Motor Company | Object sensing apparatus |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2515248A (en) * | 1945-05-10 | 1950-07-18 | Sperry Corp | Servomotor system |
| US2648040A (en) * | 1951-02-08 | 1953-08-04 | Barber Colman Co | Reversible motor control system |
-
1954
- 1954-10-05 US US460295A patent/US3707721A/en not_active Expired - Lifetime
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2515248A (en) * | 1945-05-10 | 1950-07-18 | Sperry Corp | Servomotor system |
| US2648040A (en) * | 1951-02-08 | 1953-08-04 | Barber Colman Co | Reversible motor control system |
Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2404929A1 (en) * | 1977-09-30 | 1979-04-27 | Bbc Brown Boveri & Cie | ROTARY ANTENNA INSTALLATION, IN PARTICULAR FOR SATELLITE COMMUNICATIONS STATIONS ON SHIPS AND ON THE GROUND |
| US4209789A (en) * | 1977-09-30 | 1980-06-24 | Bbc Brown Boveri & Company Limited | Rotatable aerial installation mounted on a mast with remote mechanical drive |
| DE2750401A1 (en) * | 1977-09-30 | 1979-04-12 | Bbc Brown Boveri & Cie | ROTATING ANTENNA SYSTEM, IN PARTICULAR FOR SATELLITE SHIP AND GROUND STATIONS |
| US4504836A (en) * | 1982-06-01 | 1985-03-12 | Seavey Engineering Associates, Inc. | Antenna feeding with selectively controlled polarization |
| US4672385A (en) * | 1984-01-03 | 1987-06-09 | Mel-Du Inc. | Satellite tracking system |
| US5153485A (en) * | 1989-12-28 | 1992-10-06 | Kabushiki Kaisha Shinsangyo Kaihatsu | Biaxial rotary drive unit |
| US5852423A (en) * | 1992-09-25 | 1998-12-22 | Agence Spatiale Europeene | Variable pointing antenna mount, suitable for satellite telecommunication antennas |
| US5656903A (en) * | 1993-10-01 | 1997-08-12 | The Ohio State University Research Foundation | Master-slave position and motion control system |
| US6195060B1 (en) | 1999-03-09 | 2001-02-27 | Harris Corporation | Antenna positioner control system |
| US6204823B1 (en) | 1999-03-09 | 2001-03-20 | Harris Corporation | Low profile antenna positioner for adjusting elevation and azimuth |
| GB2405041A (en) * | 2003-08-14 | 2005-02-16 | Smiths Group Plc | Radar apparatus having an antenna which may be rotated at different speeds |
| GB2405041B (en) * | 2003-08-14 | 2006-02-15 | Smiths Group Plc | Radar apparatus and methods |
| US20170025752A1 (en) * | 2015-07-20 | 2017-01-26 | Viasat, Inc. | Hemispherical azimuth and elevation positioning platform |
| US9917362B2 (en) * | 2015-07-20 | 2018-03-13 | Viasat, Inc. | Hemispherical azimuth and elevation positioning platform |
| US11417112B2 (en) * | 2018-11-27 | 2022-08-16 | Hyundai Motor Company | Object sensing apparatus |
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