Patent Grant
9882276
The present invention relates generally to articulating sensors, and more specifically, to scanning antenna systems and methods of operating the same.
Antennas and other sensors, such as RF beam scanning arrays used in radar systems, typically utilize a large area antenna array mounted on a rotating platform to revolve the antenna in the azimuth direction. These rotatable platforms allow the array to be oriented at a particular azimuth angle, or to sweep through an entire range of azimuth angles at a predetermined angular rate. In traditional rotating radar systems, one end of the array is pivotally mounted to the rotating platform, forming a cantilevered arrangement in which the array can be tilted to a desired elevation angle by, for example, a hydraulic linear actuator. In this cantilevered configuration, the array often has a center of mass offset vertically and/or horizontally from the center of the rotating platform.
These systems suffer significant drawbacks resulting from their use of traditional rotational motion (i.e. fixing a desired angle of elevation and rotating the array around a single axis) to sweep the array through a range of azimuth angles. Such problems include primary support bearing failures, power limitations and reduced reliability resulting from the use of slip-rings and rotary fluid joints, as well as the need for heavy, complex leveling sub-systems. Further, rotated antenna arrays typically suffer from a cylindrical “dead-zone” generally oriented directly above the rotating array and in which coverage by the scanning antenna array cannot be achieved.
Alternative systems and methods are desired.
In one embodiment of the present disclosure, a system includes a sensor mounted to a pivoting support frame, such as a structural sphere. The support frame is configured to be pivoted about at least two axes with respect to a common pivot point. At least one actuator, such as a friction drive, is configured to alter both the elevation and azimuth angle of the sensor by pivoting the sensor about the pivot point. The frame may be metallic and configured to conduct at least one of power and electrical signals from external sources to the sensor via the at least one actuator or a frame support.
Another embodiment of the present disclosure includes a method of articulating a sensor. The method comprises the steps of applying a first force on a first surface of a sensor support frame supporting a sensor with a first friction drive actuator for pivoting the sensor support frame about a first axis and a pivot point. A second force is applied on a second surface of the sensor support frame with a second friction drive actuator for pivoting the sensor support frame about a second axis and the pivot point. The pivot point is defined at an intersection of the first axis and the second axis. Pivoting the sensor support frame about the first and second axes provides the sensor with 360 degrees of azimuth revolution at a plurality of elevation angles.
In another embodiment, a method of articulating a sensor includes applying a force on a three-dimensional curved surface having a constant radius of a sensor support frame with a friction drive actuator. The force is operative to pivot the sensor support frame about a common pivot point defined at an intersection of at least two axes. The sensor is maintained at a predetermined elevation angle while the sensor support frame is pivoted about the pivot point to alter an azimuth position of the sensor with the friction drive actuator.
In another embodiment, a method of articulating a sensor comprises the step of pivoting a sensor support frame about at least two axes and a common pivot point for altering an elevation and azimuth angle of the sensor. The sensor support frame is pivoted by applying friction force on a surface thereof with a friction drive actuator. The sensor is maintained at a predetermined elevation angle while the sensor support frame is pivoted about the at least two axes and the pivot point with the friction drive actuator for altering an azimuth angle of the sensor.
In one aspect of the present disclosure, a system includes an arrangement that does not require separate sub-systems for leveling the system's base, tilting, and/or rotating the sensor.
It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating, for purposes of clarity, many other elements found in articulating sensors, such as antennas used in scanning radar systems. However, because such elements are well known in the art, and because they do not facilitate a better understanding of the present invention, a discussion of such elements is not provided herein. The disclosure herein is directed to all such variations and modifications known to those skilled in the art.
In the following detailed description, reference is made to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. It is to be understood that the various embodiments of the invention, although different, are not necessarily mutually exclusive. Furthermore, a particular feature, structure, or characteristic described herein in connection with one embodiment may be implemented within other embodiments without departing from the scope of the invention. In addition, it is to be understood that the location or arrangement of individual elements within each disclosed embodiment may be modified without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, appropriately interpreted, along with the full range of equivalents to which the claims are entitled. In the drawings, like numerals refer to the same or similar functionality throughout several views.
As described above, and referring generally to
As discussed, conventional systems are limited in both functionality and reliability. For example, traditional array rotation creates a virtual dead-zone directly above the array where scanning coverage cannot be achieved. Further, the hydraulic actuator(s) and pivoting arrangements used to set the elevation angle can create inaccuracies in the positioning of the antenna array, introducing pointing errors.
Regarding system reliability, conventional cantilevered large-area array systems are subject to significant forces placed on the bearings, outriggers and tie-downs, support and articulation assembles, as well as the radar face itself. In addition to creating problems securing the radar assemblies to a surface (e.g. ground), these added stresses may lead to premature failure of the components. For example, the main support bearings of the rotatable platforms are subject to significant loads from the weight of the cantilevered antenna arrays, as well as the large forces acting thereon at least in part due to dynamic imbalances and environmental forces (e.g. wind/ice/snow) acting on the exposed surfaces of the antenna array due to above-described offset of the center of mass. These forces can result in fatigue and eventual failure of the bearings and other driveline components. Further, array deflection may reduce system performance by introducing additional pointing error.
The rotational motion of the antenna array necessitates the use of components such as slip-rings for providing the array with power, as well as rotary fluid joints for providing liquid coolant. In addition to raising reliability issues, slip-rings impose significant power limitations on the system. Likewise, rotary fluid joints are prone to leaking. These arrays also typically require long cooling paths, thereby creating cooling challenges.
Further still, positioning these rotating arrangements on an uneven and/or unlevel surface necessitates additional systems to level the base, increases setup (and teardown) time and reduces operating time. Furthermore, radar base leveling is relatively complicated and difficult to perfect. In the case of a mobile radar system mounted to a vehicle, the vehicle is often fitted with heavy and expensive outriggers and actuators to provide this leveling function.
Embodiments of the present invention may improve upon these shortcomings by providing a system (e.g. a radar antenna system) which does not utilize traditional rotating motion to alter the azimuth position of a sensor (e.g. an antenna array). Furthermore, embodiments of the present invention may provide a system which does not cantilever the sensor to alter its elevation angle. In one embodiment, a system is provided comprising a sensor mounted to a support frame, for example, a structural sphere. The frame is pivotally mounted to a base such that at least one actuator may be provided for pivoting the assembly into a plurality of azimuth and elevation angles with respect to the base. The at least one actuator may comprise, for example, one or more friction drives configured to apply a drive force on a surface of the frame, pivoting the sensor to virtually any azimuth and elevation angle. In one embodiment, the actuators and/or other support members may also be used to transfer power and signals from external sources to the sensor.
As a result of the non-traditional motion of the system, many of the above-described drawbacks the prior art are eliminated. For example, power, fiber optic and cooling connections may be fed to the sensor by conduits extending through the center of the non-rotating frame, eliminating the need for rotatable connections such as slip rings and rotating fluid joints. The pivoting motion of the system can also be altered in real-time in order to correct for any leveling or positioning deficiencies, eliminating the need for a separate base leveling system, as well as reducing the pointing error of the system. Further still, full hemispherical coverage may be achieved through sensor scanning operations.
Referring generally to
Referring generally to
In one embodiment, frame 22 is supported on base assembly 21 by at least one support, such as a bearing assembly, while the elevation and azimuth angles may be controlled by at least one drive assembly, such as a friction drive, arranged on base assembly 21. In the exemplary embodiment, base assembly 21 includes two bearing assemblies 26 for supporting frame 22, and two drive assemblies 25 for altering its position.
Bearing assemblies 26 may include a plurality of bushings or bearings 28, such as ball bearings, and are configured to support and/or secure frame 22 with respect to base 21. In one exemplary configuration, bearings 28 are resiliently mounted, such that they may apply a force on frame 22 in a direction toward an opposing respective drive assembly 25. More specifically, in the embodiments of
While
Still referring to
The friction drive assemblies may be used to pivot the sensor in any number of ways. In one embodiment, for example, each drive assembly may provide a force in a single direction relative to the surface of the frame support for pivoting the frame support around a single axis. For example, one drive may apply a force in a vertical direction, and a second in a horizontal direction for creating rotational forces around the x or y and z axes. In another embodiment, both drives may apply a force in the same direction (e.g. both in the vertical direction for rotation around the x and y axis). In yet another embodiment, each drive assembly may contain more than one actuator, or a multi-axis actuator (e.g. a spherical motor), such that an individual drive assembly can impart force in multiple directions.
Referring generally to
Similarly, the embodiment of
The ability to route all connection hardware, such as wiring, fiber optics, pneumatic or hydraulic lines, and coolant piping through the interior, or proximate the center of the frames according to embodiments of the present invention may be advantageous. In addition to simplifying routing, this arrangement centralizes critical systems, and improves balance by centralizing weight. As described above, because the sensor of the present invention is not utilizing traditional rotational motion (i.e. fixing a desired angle of elevation and rotating the sensor 360° around a single axis), the wires, piping, and associated connections may only have to be fitted with conventional strain relief to withstand the pivoting of the sensor, rather than more expensive and unreliable couplers such as slip rings and rotary fluid joints.
While embodiments of the present invention generally describe power and control connections to the sensor being made through wire and/or fiber optic connections routed through the pivoting frame, alternate embodiments of the present invention may utilize the drive assemblies, actuators, frame support members, or other conductive components to transfer power and/or control signals from external sources, through the outer surface of the pivoting frame, to the sensor. More specifically, and referring generally to
With respect to any of the above-described embodiments, all or part of the support frame and/or the contact surfaces thereof may be comprised of corrosion-resistant materials, or may have corrosion-resistant coatings applied thereon, to reduce the effects of exposure to the operating environment over extended periods of time. Moreover, additional features, such as surface wipers and heating elements, may be fitted to the drive and/or support assemblies to maintain a sufficiently clean contact surface during operation, including preventing the buildup of, for example, dirt, ice or other precipitation.
The sensor of any of the above-described embodiments may be supported on a telescoping or otherwise extendable frame moveable between a first retracted position, a second extended position, and any intermediate position therebetween. For example, a center portion 74 of the frame or rotor of
In another embodiment telescoping counterbalances may be provided and arranged between the base and the sensor. The counterbalances are configured to provide additional support to the sensor, by, for example, counteracting forces placed on the surfaces of the sensor by loads generated by environmental forces (e.g. wind/ice/snow), as well as any dynamic imbalances caused by the articulation of the sensor. In this way, the counterbalances can be used to alter the stiffness of the sensor, adjusting its natural frequency, thus allowing the system to compensate for a variety of operating conditions and desired operating parameters. The counterbalances may be most effectively arranged proximal to the outer edges of the sensor, supporting the portions of the sensor likely to experience the most deflection. However, the counterbalances may be placed anywhere support is deemed most effective, and/or dictated by packaging constraints. The counterbalances may comprise linear actuators, but may also comprise dampeners, springs, or other suitable components, with or without telescoping ability. In an alternative arrangement, the counterbalances may be utilized to provided additional motion control, for example, dampening the motion of the sensor as it is pivoted. This may be particularly important during high-speed sweeps of the sensor, wherein the forces generated in the sensor due to quickened acceleration and deceleration of the sensor are greater. In either configuration, the use of counterbalances provides for the active dynamic adjustment of the sensor, providing significant tuneability and stability control over the arrangements of the prior art.
In any of the above-described embodiments, a control system may be provided for altering the position of the sensor mounted onto the drive system (e.g. an antenna array). The control system may utilize, for example, an array mapping routine to correlate the sensor's rotational orientation to the system's reference coordinate system. Referring generally to
In the exemplary embodiment, each channel 84,86 features a feedback system comprising, for example, a position sensor in communication with motion controller 82. Position sensor 94 may comprise an encoder or optical sensor operative to measure, for example, the displacement (e.g. rotation) of each of the actuators during use. In other embodiments, position sensors 94 may be implemented in other configurations, such as, for example, part of an optical sensing system used to determine the position of the antenna array, or the position of actuator relative to the surface of the array. In particular, the real-time array position monitoring and feedback may be achieved using other means in addition to, or in place of encoders. For example, an optical positioning system, including one or more sensors and/or reflectors located on the base, frame or on the array itself, and an accompanying light source may be provided. In other embodiments, inclinometers and/or an inertial navigation unit (INU) located within the antenna array may be provided for monitoring the angular position of the array. In one embodiment, a two-axis inclinometer 88 may be provided for measuring the real-time tilt angle of the array. It should also be understood that this inclinometer, and/or the motion controller may be calibrated (e.g. zeroed) to correct for unlevel ground. Additional sensors may be implemented into the system for more precise control of the array. As indicated above, alterations to array orientation or scanning path may be made in real-time, to correct for, for example, temperature or thermal effects, wind/weather loads, and other environmental conditions. Accordingly, sensors operative to detect these conditions may be fitted to the system and input into the motion controller for increasing the operational accuracy of the array.
Referring again to
The above-described embodiments utilize a control system (
While this disclosure describes a limited number of frame and support arrangements, it is envisioned that numerous alternate configurations may be utilized between the sensor and the base to provide a similarly pivotal system. For example, spherical bearings, such as pedestal air bearings may be used for providing low friction operation, a high degree of articulation in all directions of the sensor, and a high load-carrying capacity. Further still, flexures, hinges, or bushings may all be used without departing from the scope of the present invention.
Systems according to the above-described embodiments provide improved sensor coverage compared to conventional systems, without resorting to traditional rotational movement, and the above-described drawbacks associated therewith. Further, both the elevation angle and the azimuth position of the sensor in the embodiments described herein are controlled by the same drive components. This is unlike traditional systems which employ separate systems, for example a set of at least three linear actuators to level the base, a linear actuator to control the elevation angle of the sensor, and a rotational drive mechanism to alter the azimuth orientation. In accordance with embodiments of the present invention, complexity, cost, and weight reductions may be realized over the prior art arrangements.
While embodiments of the present invention have generally been described in the context of radar systems having articulating antenna arrays, it should be understood that embodiments of the drive system may be applied more generally to articulating sensors or antenna systems without departing from the scope of the present invention.
While the foregoing invention has been described with reference to the above-described embodiment, various modifications and changes can be made without departing from the spirit of the invention. Accordingly, all such modifications and changes are considered to be within the scope of the appended claims. Accordingly, the specification and the drawings are to be regarded in an illustrative rather than a restrictive sense. The accompanying drawings that form a part hereof, show by way of illustration, and not of limitation, specific embodiments in which the subject matter may be practiced. The embodiments illustrated are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. This Detailed Description, therefore, is not to be taken in a limiting sense, and the scope of various embodiments is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled.
Such embodiments of the inventive subject matter may be referred to herein, individually and/or collectively, by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any single invention or inventive concept if more than one is in fact disclosed. Thus, although specific embodiments have been illustrated and described herein, it should be appreciated that any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations of variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the above description.
This application is a divisional application of co-pending U.S. patent application Ser. No. 13/205,261, entitled PIVOTING SENSOR DRIVE SYSTEM, filed Aug. 8, 2011, the entire contents of which is herein incorporated by reference for all purposes.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4378709 | Chitayat | Apr 1983 | A |
| 4490724 | Bickman | Dec 1984 | A |
| 5419521 | Matthews | Mar 1995 | A |
| 6034643 | Nishikawa et al. | Mar 2000 | A |
| 6111542 | Day et al. | Aug 2000 | A |
| 6218999 | Bousquet et al. | Apr 2001 | B1 |
| 6404385 | Croq et al. | Jun 2002 | B1 |
| 6407714 | Butler et al. | Jun 2002 | B1 |
| 6486845 | Ogawa et al. | Nov 2002 | B2 |
| 6512490 | Lee | Jan 2003 | B1 |
| 6812904 | Tietjen | Nov 2004 | B2 |
| 7969375 | Blalock | Jun 2011 | B2 |
| 20090315795 | Blalock | Dec 2009 | A1 |
| 20100092179 | Bunch et al. | Apr 2010 | A1 |
| 20100245196 | Miron | Sep 2010 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13205261 | Aug 2011 | US |
| Child | 14695586 | US |
