Communications: radio wave antennas – Antennas – With means for moving directive antenna for scanning,...
Reexamination Certificate
1999-03-09
2001-02-27
Phan, Tho (Department: 2821)
Communications: radio wave antennas
Antennas
With means for moving directive antenna for scanning,...
C343S765000, C343S757000, C343S882000, C248S183300
Reexamination Certificate
active
06195060
ABSTRACT:
FIELD OF THE INVENTION
This invention is related to antenna positioners, and more particularly, this invention is related to an antenna positioner control system.
BACKGROUND OF THE INVENTION
Direct broadcast satellite (DBS) signals are often transmitted to aircraft and other moving vehicles. These transmitted signals are often KU-band television signals that are transmitted to commercial aircraft, trains and other moving vehicles, and are typically UHF and VHF band signals, which can be received on small antennas, such as the common 18″ disks placed on the sides of houses. The antenna can also be formed as a phased array antenna, and designed as a flat plate, as is known to those skilled in the art. Many different types of housings and positioners have been designed to point the antenna's main beam at the desired direct broadcast satellite while an aircraft maintains various commercial cruise flight dynamics. These dynamics include a role of 5°/second and 5°/second
2
; a pitch of 5°/second and 3°/second
2
; and a yaw of 5°/second and 5°/second
2
.
One current method has been to use a mechanical device with an in-line jack screw actuator for elevation and a direct drive azimuth. In most types of controls, an antenna controller receives position commands and directs movement of various motors. However, these type of requirements are not adequate because with a mechanical system, the slew rate is slow and motors often overheat in maintaining positions. Also, the controller does not include a rate feed forward, which is desirable. Also, many prior art antenna positioners have mechanical designs that allow control over azimuth and elevation, but the motors and drive mechanics have excessive backlash. Also, many prior art designs do not fit into low profile housings that are adapted for mobile applications, such as mounting on the fuselage of an aircraft.
U.S. Pat. No. 5,025,262 to Abdelrazik et al. discloses a pedestal with a helical element antenna that is mechanically steered with reference to an azimuth axis and elevation axis. A mechanical steering system includes a supporting frame having an azimuth member and an elevation member that is integral with the azimuth member. It includes a longitudinal axis displaced from the azimuth axis.
U.S. Pat. Nos. 5,689,276 and 5,420,598 to Uematsu et al. disclose an antenna housing for a satellite antenna device, which mounts on a moving body and includes an automatic tracking mechanism. An elevation motor is fixed to a rotary base. A series of pulleys and shafts act as a driving mechanism. A rack has teeth formed along a circle about the rotating axis in elevation direction of the antenna unit A. The teeth of the rack mesh with the pinion gear to be driven circumferentially by the driving torque transmitted to a pinion gear. Thus, the antenna unit is driven for rotation in the elevation direction. An azimuth motor is fixed on the rotary base. Through a sufficient pulley mechanism, the driving torque of the azimuth motor is transmitted to the pinion, which meshes with teeth of a belt such that the driving torque of the azimuth motor is transmitted through the pulleys.
U.S. Pat. No. 5,153,485 to Yamada et al. discloses a high gain antenna that is mounted on board an automobile for reception of satellite broadcasting. The system uses a beam antenna in the form of a flat plate that is secured to an antenna bracket. A turntable has a disk-shaped spur gear that includes a gear around its lateral side. Turntables are rotatably mounted on a stationary base by a bearing. Reduction gearing in a motor is mounted on the support plate and secured to a stationary plate base. The beam antenna can be moved in both azimuth and elevation.
Many of these systems suffer some of the drawbacks noted above.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an antenna positioner control system that allows adequate control over elevation and azimuth with a rate forward.
It is still another object of the present invention to provide an antenna positioner control system that allows adequate control over elevation and azimuth with adequate command signaling and control.
In accordance with the present invention, an antenna positioner control system includes a housing and a hub mounted within the housing. A support plate is rotatably mounted on the hub. An antenna is pivotally mounted on the support plate. At least one elevation drive servomotor is mounted on the support plate and interconnects the antenna for pivoting the antenna a predetermined angle and adjusting elevation of the antenna. At least one azimuth drive servomotor is mounted on the support plate and interconnects the antenna for rotating the support plate relative to the hub a predetermined arcuate distance for adjusting azimuth of the antenna.
An antenna control unit is operatively connected to the elevation drive servomotor and the azimuth drive servomotor. The antenna control unit includes an elevation control circuit operatively connected to the elevation drive servomotor for adjusting elevation and an azimuth control circuit operatively connected to the azimuth drive servomotor for adjusting the azimuth angle of the antenna. Each of the control circuits includes a position feedback control loop and a resolver positioned within each position feedback control loop. Each control circuit also includes a rate feedback control loop and a tachometer positioned within the rate feedback control loop. Also included is a motor feedback control loop within each circuit.
In one aspect of the present invention, a current compensator is positioned within the motor feedback control loop. A position compensator is also positioned within a position feedback control loop. A tachometer compensator can be positioned within the rate feedback control loop.
In still another aspect of the present invention, an antenna subsystem controller is operatively connected to the antenna control unit. The antenna subsystem controller further comprises a circuit for generating azimuth and elevation pointing commands to the antenna control unit. The antenna can include a phased array antenna. An antenna support shaft can be mounted on the antenna such that rotation of the support shaft pivots the antenna and adjusts elevation. The elevation servomotor can be operatively connected to the support shaft. The elevation drive servomotor can include an output shaft and a drive mechanism operatively interconnecting the output shaft and drive shaft.
In still another aspect of the present invention, the antenna control unit includes a circuit for generating a rate feed forward command to each of the azimuth drive and elevation drive servomotors corresponding to an anticipated velocity position.
A method aspect of the present invention is also disclosed. The method controls azimuth and elevation of an antenna and comprises the step of providing a hub mounted within a housing, a support plate rotatably mounted on the hub. The antenna is pivotally mounted on the support plate. The method comprises the step of generating an azimuth pointing command and elevation pointing command within respective azimuth and elevation control circuits to respective azimuth and elevation drive servomotors. The respective azimuth and elevation drive servomotors are driven through respective azimuth and elevation current acceleration loops. The azimuth and elevation voltage commands are generated to the respective current acceleration loops through respective tachometer rate loops that are closed about respective azimuth and elevation tachometers. The respective azimuth and elevation velocity commands are generated to the respective tachometer rate loops through respective azimuth and elevation position loops.
In still another aspect of the present invention, the method includes the step of closing the respective azimuth and elevation position loops about the tachometer rate loops through the use of resolvers. The method also includes the step of generating a rate feed forward command to increase the responsiveness of th
Green Dennis A.
Ostby Amy J.
Spano Dawson P.
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Harris Corporation
Phan Tho
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