Recently, directional antennas for communication with one or more satellites have been mounted on vehicles. A directional antenna has a relatively narrow beam and, therefore, must be pointed with relatively high precision at the satellite. Combining a pointing feature on a moving vehicle creates problems with multiple degrees of freedom.
Conventionally, electric motors attached to a gimbal have been used, for instance, to rotate antenna platforms such that the azimuth angle of the antenna is properly aligned with the satellite. Some antenna platforms may include an antenna with a wide enough elevation beam that the platform may be able to be configured with a fixed-look elevation angle. However, even with these wide elevation beams, some elevation angle adjustments may be needed if the antenna is to be placed in very different latitudes. In addition, any deviation from optimal elevation pointing will impact antenna performance.
With moving vehicles, that can cover a variety of latitudes and elevations, adjusting the azimuth angle is typically not sufficient. The elevation angle also must be adjusted. An additional motor attached to an additional gimbal for adjusting the elevation angle has been used conventionally. However, using multiple motors means more complexity and additional cost.
There is a need for systems, methods, and apparatuses for dual-angle adjustments of a satellite-tracking antenna that use only a single motor to accomplish both azimuth angle adjustments and elevation angle adjustments.
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.
The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention can be practiced. The term “exemplary” used throughout this description means “serving as an example, instance, or illustration,” and should not necessarily be construed as preferred or advantageous over other exemplary embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the exemplary embodiments of the invention. It will be apparent to those skilled in the art that the exemplary embodiments of the invention may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the novelty of the exemplary embodiments presented herein.
Exemplary embodiments of the present invention are directed to systems, methods, and apparatuses for dual-angle adjustments of a satellite-tracking antenna that use only a single motor. With a single motor, embodiments of the present invention can still accomplish both azimuth angle adjustments and elevation angle adjustments.
A movable body 120, as used herein, may include any type of body that is transportable. Some non-limiting examples are vehicles, boats, airplanes. In addition, a bracket or other mounting hardware to which the satellite-tracking antenna 200 is mounted for the purpose of mounting on a fixed object may be considered a movable body 120. For ease of description, for the most part, the movable body 120 may be referred to herein as a vehicle 120. However, those of ordinary skill in the art will recognize that the movable body may be stationary. Furthermore, adjustments made to the pointing of the antenna may be made simply to point to a satellite when the movable body is stationary or to point to additional satellites.
In
Also shown in the second coordinate system 104 is an azimuth angle 170, which defines the angle between a north direction and the body-direction vector 152. An azimuthal relationship 172 is the angle between the current body-direction vector 152 and the satellite-direction vector 112 in a plane that is parallel with the horizontal axis H. Thus, as the vehicle 120 moves, the satellite-direction vector 112, the body-direction vector 152, and the azimuthal relationship 172 therebetween will change.
In
The satellite-direction vector 112, body-direction vector 152, elevation angle 160, and azimuth angle 170 have been defined relative to a geographic location and a fixed coordinate system. However, those of ordinary skill in the art will recognize that for embodiments of the present invention these vectors and angles may be defined in other fixed coordinate systems. Specifically, a moving coordinate system relative to the vehicle 120 may be used.
As the vehicle 120 moves, the satellite tracking antenna 200 attached to the vehicle must adjust the direction it points to remain pointed at the satellite 110.
The embodiments described herein are described with respect to an electric motor, commonly used to rotate antenna platforms. However, it should be understood that the motor could alternatively comprise any type of motor, including those driven by means other than electrical signals. In addition, the embodiments described herein may be used in applications other than antenna assemblies, such as in automotive applications, and computer applications.
In
The term conveyor, as used herein, may include elements for coupling rotational motions between two spindles, such as, for example, belts, chains, and engaged gears.
The elevation adjuster 260 includes an elevation spindle 264 at the center of an elevation gear 262. The elevation gear is engaged with a first gear 252, which is fixedly attached to the motor housing. Of course, the first gear may be attached to any suitable fixed portion of the antenna aiming apparatus 200.
A screw mechanism 270 is attached to the elevation spindle 264. The screw mechanism 270 includes a lead nut 274 attached to the elevation spindle 264 and a lead screw 272 threaded through the lead nut 274. The lead screw 272 is attached to a linkage 275, which is attached to the directional antenna 210.
Thus, as the elevation gear 262 turns, so does the lead nut 274, which drives the lead screw 272 up or down depending on the direction of rotation for the elevation gear 262. As the lead screw 272 moves up, it pushes the directional antenna 210 up through the linkage 275. Similarly, as the lead screw 272 moves down, it pulls the directional antenna 210 down through the linkage 275.
A spring (not shown) may force the lead screw 272 against the lead nut 274 to allow the mechanism to over travel in both the up extreme and down extreme without locking up. When at an extreme, the lead screw 272 threads disengage and the minor diameter of the lead screw 272 contacts the threads of the lead nut 274.
Referring to
In operation, as the motor 240 turns, it turns the platform 256, and the directional antenna 210 about the azimuthal axis 280 and the stationary first gear 252. In addition, because the elevational gear 262 is engaged with the first gear 252, the elevational gear 262 will also turn as it orbits about the first gear 252. Rotation of the elevational gear 262 causes the lead screw 272 to turn, which pivots the directional antenna 210 about the elevational axis. Thus, a complete turn of the directional antenna 210 about the azimuthal axis 280 causes a small pivot up or down of the directional antenna 210 about the elevational axis 290, while also enabling the directional antenna 210 to point at any azimuth angle within the complete turn. Thus the azimuth adjustment and the elevation adjustment are coupled together and based on rotation amounts of a single motor. A more detailed explanation of pointing the directional antenna 210 is given below.
The exemplary embodiment of
In operation, as the shaft of the motor 240A turns, it turns the platform 256A, and the directional antenna 210A about the azimuthal axis and the stationary first gear 252A. In addition, because the intermediate gear 268 is engaged with the first gear 252A, the intermediate gear 268 will also turn as it orbits about the first gear 252A. Rotation of the intermediate gear 268 causes rotation of the bevel gear 262A. As the bevel gear 262A turns, the elevation spindle 264A turns the lead screw 272A forcing the lead nut 274A out or in, which pushes or pulls on the linkage 275A, which pushes or pulls on the back side of the directional antenna 210A. Pushing and pulling on the backside of the directional antenna 210A causes the directional antenna 210A to pivot down or up about the elevational axis.
Thus, as with the embodiment of
With reference to
In some embodiments, a position may be determined without using GPS location. These embodiments may use an additional satellite at which the directional antenna can point. By pointing at two different satellites, at different locations, the processor can determine the geographic location based on the difference between the vectors to each of the two different satellites.
Using various combinations of the geographical location, the elevation, the satellite-direction vector 112, and the body-direction vector 152, the processor 310 can cause the motor to rotate to adjust both the elevation angle 160 and the azimuth angle 170 to point the directional antenna 210 at the satellite.
In some embodiments, inertial sensors 240 may be included to communicate inertial information to the processor 310. As non-limiting examples, the inertial sensors 240 may include accelerometers, gyroscopes, wheel motion from the vehicle, or other motion-sensing devices. The controller 300 can keep track of position, velocity, and direction of the movable body 120 by integrating the inertial information. Thus, the controller 300 can rotate the motor the desired amount to accurately point the directional antenna 210 based on GPS information, inertial information, or a combination thereof.
In some embodiments, a signal monitor 350 may be included. The signal monitor 350 may monitor the strength of the signal from the directional antenna 210. The processor 310 may use this signal strength information to determine how accurately the directional antenna 210 is pointed and form a closed-loop system to repeatedly make adjustments, through the motor 240 and mechanical system 370, to adjust the pointing direction of the directional antenna 210.
The process 400 performs a loop, which is described with reference to
Decision block 406 tests to see whether inertial information will be used on this pass through the loop. If so, operation block 408 acquires new inertial information from the inertial sensors 340.
Decision block 410 tests to see whether signal strength information will be used on this pass through the loop. If so, operation block 412 determines the current signal strength.
Operation block 414 determines the current body-direction vector 152 based on the GPS information, inertial information, or a combination thereof. If no new information is available, a previous body-direction vector 152 may be used.
Operation block 414 determines the current satellite-direction vector 152 based on information in the controller about the current satellite position, GPS information, inertial information, or combinations thereof. If no new information is available, a previous satellite-direction vector 152 may be used.
If needed, operation block 418 causes the directional antenna 210 to rotate a number of full-turns to modify the elevation angle 160 to more accurately point at the satellite based on the elevational relationship 162 between the body-direction vector 152 and the satellite-direction vector 112. Due to the mechanical gain from the gears and linkages, one full rotation of the directional antenna 210 only causes a small change in the elevation angle, as is explained below. Thus, a number of turns may be needed to cause the desired elevation angle change.
Operation block 420 then causes the directional antenna 210 to rotate a partial-turn amount (i.e. less than or equal to a full-turn amount) to modify the azimuth angle 170 to more accurately point at the satellite based on the azimuthal relationship 172 between the body-direction vector 152 and the satellite-direction vector 112.
If signal strength is being used in the process, the full-turn amounts and partial-turn amounts created in operation blocks 418 and 420 may be determined by a closed-loop feedback algorithm based on current signal strength, previous signal strength, and anticipated future signal strength.
Operation block 422 tests to see if the movable body 120 has completed a full circle. For example, perhaps the vehicle 120 has gone completely around a block. If the vehicle completes full circles, the process may cause full turns to occur as the azimuth angle is corrected. These full turns cause a change in the elevation angle. If a full turn of the movable body 120 has occurred, operation block 424 “unwinds” the full turn by making a full-turn of the directional antenna 210 in the opposite direction to correct the elevation angle back to where it is desired.
The process 400 then repeats. While not shown, the directional antenna may be “zeroed” to an extreme angle of all the way up or all the way down. These extreme angles will be known by the process and can be used as initial conditions to determine the number of turns required to achieve the desired elevation angle.
Similarly, curve 620 shows the elevation angle for the exemplary embodiment of
Of course, as a person of ordinary skill in the art will recognize, the low and high extremes, as well as the number of degrees per full-turn may be modified in various embodiments of the invention by changing the mechanical system 370 (
The azimuth adjuster 250B couples the motor 240B to the platform 256B via a clutch plate 420. The azimuth adjuster 250B includes a clutch arm 410 coupled to the motor spindle 244B. The clutch arm 410 holds a ball (not visible) against one of the holes in an inner ring of holes 424 in the clutch plate 420. The clutch arm 410 and ball may be held against one of the holes with a biasing agent, such as, for example a spring. Thus the azimuth adjuster 250B forms a detent between the clutch plate 420 and the motor spindle 244B.
In operation, as the motor 240B spins, the detent between the clutch arm 410 and the clutch plate 420 causes the clutch plate 420, platform 256B, and directional antenna aperture 210B to rotate.
The elevation adjuster 260B couples the motor 240B to the linkage 275B via a conveyor 252B. As a non-limiting example, the conveyor 252B is shown as a cable 252B. The cable 252B is wrapped around the motor spindle 244B and extends out through a hole 460 in a side of the platform 256B. The cable 252B wraps up through a notch 462 and attaches to an arm of the linkage 275B. The cable then returns to the motor spindle 244B to form a loop that is wrapped around the motor spindle 244B. Of course, other conveyors coupling the motor spindle 244B to the linkage 275B, such as combinations of belts, cables, and gears may be used in other embodiments of the present invention.
In operation, as the motor spindle 244B turns, the cable will move back and forth in such a way as to slide the linkage 275B back and forth. Sliding the linkage 275B back and forth causes the directional antenna aperture 210B and directional antenna (not shown) to pivot about the elevational axis.
The elevation adjuster 260B also includes a solenoid 440. When the solenoid 440 is activated, a plunger (not visible) engages in one of the holes in an outer ring of holes 422 in the clutch plate 420.
To adjust the elevation angle, the solenoid 440 is activated causing the plunger to engage with one of the holes in the outer ring of holes 422. This engagement prevents the clutch plate 420, platform 256B, and directional antenna (not shown) from rotating. Thus, as the motor turns, the cable will move back and forth, which slides the linkage back and forth, which pivots the directional antenna aperture 210B. While the elevation angle adjustment is happening, the platform 256B is held stationary by the activated solenoid 440. As a result, the torque of the motor 244B overcomes the detent of the clutch arm 410 holding the ball in one of the holes in the inner ring of holes 424 and the ball will slip to the next hole in the inner ring of holes 424. This slippage will occur to successive holes while the motor 240B is turning and the solenoid 440 is activated such that the clutch arm 410 rotates, but does not cause rotation of the clutch plate 420.
To adjust the azimuth angle, the solenoid 440 is deactivated causing the plunger to disengage from one of the holes in the outer ring of holes 422. Thus, the clutch plate 420 is not held stationary and the detent from the clutch arm 410 holding the ball against one of the holes in the inner ring of holes 424 will cause the clutch plate 420, platform 256, and directional antenna (not shown) to rotate about the azimuthal axis.
Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.
Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the exemplary embodiments of the invention.
The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), flash memory, Read Only Memory (ROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.
In one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
The previous description of the disclosed exemplary embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these exemplary embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.