IL127828A - Homing gimbal system - Google Patents

Description

ηνϊ? D^ J rniun HOMING GIMBAL SYSTEM HOMING GIMBAL SYSTEM FIELD AND BACKGROUND OF THE INVENTION The present invention relates to a homing gimbal system and, more particularly, to a gimbal system enabling homing of dual payloads, such as radar setters and charge coupled device (CCD) sensors in, for example, flying objects, such as, guided missiles.

Various seeking and guiding payloads, both active (e.g., radar systems) and passive (e.g., InfraRed based guiding systems), frequently found mounted in the nose of flying objects, such as, but not limited to, guided missiles and airplanes, require a homing gimbal system to enable rotation of their antennas in desired directions.

Typically, the nose diameter of aerodynamically shaped (e.g., flying) objects, such as missiles, is small, nevertheless, it is desired that a gimbal system installed in such objects would enable to assemble as large as possible payload onto it.

Furthermore, as these objects are, in most cases, required to perform large maneuvers, it is desired that a gimbal system would have a wide field of regard.

In addition, in many cases, the payload mounted onto a homing gimbal system is an electro-optical system, which electro-optical system requires high spatial stability for accurate functioning, therefore, it is further desired that a homing gimbal system would have a high spatial stability.

Homing gimbal systems are typically characterized by two orthogonal axes enabling homing and may be categorized to external and internal axes homing gimbal systems and to virtual axis type homing gimbal system, shown in Figures l a-c, respectively.

With reference to Figure la, an external axes homing gimbal system 10 is typically characterized by an external gimbal 20 rotating around an outer axis 22, outer axis 22 is fixed in both of its ends to an external frame 24. An internal payload 26 is rotatably and internally affixed to gimbal 20 via an inner axis 28, inner axis 28 is orthogonal to outer axis 22. Therefore, axes 22 and 28 enable homing of internal payload 26 in both axial directions.

Referring now to Figure lb, an internal axes homing gimbal system 12 is typically characterized by an internal gimbal 30 rotating around a first axis 32, which is fixed to the external frame 24. An external payload 34 is rotatably and externally affixed to internal gimbal 30 via a second axis 36, second axis 36 is orthogonal to first axis 32. Therefore, axes 32 and 36 enable homing of external payload 34 in both axial directions.

Referring now to Figure lc, a virtual axis type homing gimbal system 14 is typically characterized by an arc-shaped gimbal 38 slideable on sliding devices, rollers (or pulleys) 39 relative to an external frame 40, so as to form a rotational movement around an imaginary (i.e., virtual) centroidal axis 42. A payload 44 is rotatably and internally (as sown in Figure lc) or, alternatively, externally (not shown) affixed to arc-shaped gimbal 38 via an axis 46, axis 46 is orthogonal to imaginary centroidal axis 42. Therefore, axes 42 and 46 enable homing of payload 44 in both axial directions.

External and internal axes homing gimbal systems have numerous limitations. These include limited payload diameter and limited field of regard, both due to mechanical interferences of the payload with the gimbal, with the external frames and/or with the envelope of the object in which the system is enclosed. For example, in a common design of an electro-optical seeker, assembled in a guided missile nose, using external or internal axes homing gimbal system, the diameter of the electro-optical seeker (i.e., the payload) is limited to 30% - 50% of that of the missiles nose at the location of installation and, the field of regard is limited to ΓΓ 30-35° (i.e., total of 60-70°) in each axial direction.

Virtual axis type homing gimbal systems provide nearly a maximal payload diameter and a less limited field of regard (e.g., rr 55-60°), since there are much limited mechanical interferences of the payload with the arc-shaped gimbal and with the external frame and/or the envelope of the object in which the system is assembled, as compared with the internal and external axes homing gimbal systems, described hereinabove. Nevertheless, virtual axis type homing gimbal systems do not provide the level of spatial stability required from a gimbal system used as a homing device of electro-optical payloads due to the relatively high friction associated with peripherally located rollers, especially when exposed to external vibrations.

A homing gimbal system utilizing two axes of rotation which are not orthogonal was described in U.S. Pat. No. 4,802,640. However, this system, beside being very complex for manufacturing, assembly and disassembly, and being space consuming, is, like internal and external axes homing gimbal systems, limited in its field of regard.

There is thus a widely recognized need for, and it would be highly advantageous to have, a homing gimbal system devoid of all of the above limitations and, therefore, to provide a system enabling to mount larger payloads, having a wide field of regard and, high stability to enable mounting of stability sensitive payloads, such as electro-optical systems. Hence, the homing gimbal system of the present invention can be efficiently used as a homing device for stability sensitive electro-optical systems in, for example, guided missiles.

SUMMARY OF THE INVENTION According to the present invention there is provided a homing gimbal system which can be used for dual homing of payloads, such as radars and electro-optical payloads, in guided missiles. The homing gimbal system of the present invention enables to mount payloads which are limited in size, in many applications, substantially only by the diameter of the object in which the system is installed, to mount stability sensitive payloads and, to provide the payload with a wide field of regard in all directions.

According to further features in preferred embodiments of the invention described below, the homing gimbal system includes (a) a first gimbal rotating around a first axis for homing in a first axial direction; (b) an intermediate gimbal being pivotally connected in a first connection to the first gimbal, the intermediate gimbal rotating around a second axis, the second axis being orthogonal to the first axis for homing in a second axial direction, the second axial direction being orthogonal to the first axial direction; and (c) a payload being pivotally connected in a second connection to the intermediate gimbal, the payload rotating around a third axis, the third axis being orthogonal to the second axis for further homing in a third axial direction.

According to still further features in the described preferred embodiments the homing in said second axial direction and said further homing in said third axial direction are low in friction.

According to still further features in the described preferred embodiments the first gimbal is an arc-shaped gimbal, the first axis is an imaginary axis and the rotation of the arc-shaped gimbal around the imaginary axis is by sliding the arc-shaped gimbal on sliding devices.

According to still further features in the described preferred embodiments the first connection of the intermediate gimbal to the first gimbal is selected from the group of connections consisting of an internal connection and an external connection.

According to still further features in the described preferred embodiments the second connection of the payload to the intermediate gimbal is selected from the group of connections consisting of an internal connection and an external connection.

According to still further features in the described preferred embodiments the second connection of the intermediate gimbal to the first gimbal is internal.

According to still further features in the described preferred embodiments the intermediate gimbal is a closed or an open member.

According to still further features in the described preferred embodiments the closed member has a shape selected from the group of shapes consisting of oval shapes, polygonal shapes and shapes including oval sections and polygonal sections.

According to still further features in the described preferred embodiments the homing gimbal system further includes (d) first means to rotate the first gimbal around the first axis; (e) second means to rotate the intermediate gimbal around the second axis; and, (f) third means to rotate the payload around the third axis.

According to still further features in the described preferred embodiments the first means is a first gear or belt transmission.

According to still further features in the described preferred embodiments the second means is a second gear or belt transmission.

According to still further features in the described preferred embodiments the third means is a direct drive motor.

According to still further features in the described preferred embodiments the homing gimbal system further includes (g) a control system controlling the rotation of the first gimbal, the intermediate gimbal and the payload around the first, second and third axes, respectively.

According to still further features in the described preferred embodiments the control system includes a correlating function to correlate between the rotation of the payload around the third axis and the rotation of the first gimbal around the first axis.

The present invention successfully addresses the shortcomings of the presently known configurations by providing a homing gimbal system suitable to mount payloads which are, in many applications, limited in size substantially only by the diameter of the object in which the system is installed; to mount stability sensitive payloads and, to provide the mounted payload with a wide field of regard in all directions.

The present invention discloses a novel homing gimbal system having two nominally parallel or coinciding axes, around which a first gimbal and a payload are rotated, and an additional orthogonal axis, around which an intermediate gimbal is rotated. Stabilization of the system is performed via the second and third axes characterized by low friction. Field of regard coverage is obtained by virtue of the first (high friction) and second (low friction) axes, thus, stability as well as wide field of regard are obtained. Furthermore, the built-up of the invented homing gimbal system enables to mount payloads limited in their size, in many applications, substantially only by the diameter of the object in which the system is installed.

BRIEF DESCRIPTION OF THE DRAWINGS The invention herein described, by way of example only, with reference to the accompanying drawings, wherein: FIG. l a, lb and l c are, a cross-section and an end view of an external axes homing gimbal system, a cross-section and an end view of an internal axes homing gimbal system and, a perspective view of a virtual axis type homing gimbal system, respectively, all systems are prior art; FIGs. 2a and 2b are perspective views of the basic components of a homing gimbal system according to the present invention; FIGs. 3a, 3b and 3c are side and end views of some of the connection types employed to connect and rotation means employed to rotate the basic components of a homing gimbal system according to the present invention; and FIG. 4 is a perspective view of rotation means employed to rotate the basic components of a homing gimbal system according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is of a homing gimbal system which can be used for dual homing of payloads such as radar and electro-optical payloads assembled in, for example, guided missiles. Specifically, the present invention can be used to mount large payloads, provide them with a wide field of regard and with high stability, therefore, to enable mounting of stability sensitive apertures such as electro-optical systems and/or a large apertures such as radar systems.

The principles and operation of a homing gimbal system according to the present invention may be better understood with reference to the drawings and accompanying descriptions.

Referring now to the drawings, Figures 2a-b, illustrates the basic components of a homing gimbal system according to the present invention, generally referred to hereinbelow as system 50. As shown in Figures 2a-b, system 50 includes three major components. These are: (1) a first gimbal 52 rotating around a first axis 54 for homing in a first axial direction; (2) an intermediate gimbal 56 which is pivotally connected to first gimbal 52, in a first connection at locations 58 and 60, intermediate gimbal 56 rotates around a second axis 62 which is orthogonal to first axis 54, for homing in a second axial direction; and, (3) a payload 64 pivotally connected in a second connection at locations 66 and 68 to intermediate gimbal 56, the payload is rotating around a third axis 70 which is orthogonal to second axis 62 for further homing in a third axial direction.

In a preferred configuration, exemplified in Figures 2-4, first gimbal 52 is an arc-shaped gimbal, and therefore first axis 54 is an imaginary axis and the rotation of the arc-shaped gimbal around imaginary axis 54 is by sliding arc-shaped gimbal 52 on sliding devices 72 (pulleys, in the example given in Figures 2a-b, or, rollers, similar to those shown in Figure lc) which are pivotally connected to an external frame (not shown).

In the preferred configuration, exemplified in Figures 2a-b, 3a and 4, intermediate gimbal 56 is connected internally to arc-shaped gimbal 52 and, payload 64 is connected internally to intermediate gimbal 56. Nevertheless, it is understood to those with skills in the art that intermediate gimbal 56 may alternatively be connected externally to arc-shaped gimbal 52 (as shown in Figures 3b-c), and that, in both cases payload 64 may be connected either internally (as shown in Figures 2a-b) or alternatively externally (as shown in Figure 3b) to intermediate gimbal 56.

At present it is preferred that intermediate gimbal 56 would be a closed (e.g., ringed) structure, preferably oval (e.g., circular) shaped. Nevertheless, other shapes, such as, for example, polygonal shapes or, shapes including oval sections and polygonal sections, are also possible. Furthermore, regardless of its shape, intermediate gimbal 56 may alternatively acquire an open structure.

The built-up of the homing system 50 of the present invention enables dual homing in wide fields of regard, which may reach n 60° (i.e., total of 120°) on all directions, depending on the specific installation. This wide field of regard is similar to the field of regard characterizing virtual axis type homing gimbal systems, nevertheless it is substantially wider than the fields of regard characterizing external and internal axes homing gimbal systems, as described above in the field and background section.

As mentioned hereinabove, when the homing system 50 of the present invention operates, axis 54 enables movement of payload 64 in a first axial direction, axis 58 enable movement of payload 64 in a second axial direction which is orthogonal to the first axial direction and axis 70 enables movement of payload 64 in a third axial direction, which third axial direction is orthogonal to the second axial direction. In the preferred configuration, exemplified in Figures 2a-b, by being pivotal, the rotational movements of intermediate gimbal 56 and payload 64 about axes 58 and 70, respectively, are characterized by low friction, whereas the rotational movement of arc-shaped gimbal 52 around imaginary axis 54, by nature, is characterized by relatively high friction, especially during acceleration. As mentioned above in the field and background section, the major limitation of virtual axis type homing gimbal systems is a high friction generated between the arc-shaped gimbal and the sliding devices (rollers 39, in the example given in Figure lc) when rotated one relative to the other, which high friction is hard to control, limiting the types of .payloads that may be mounted on such gimbal systems to ones that are stability insensitive. Nevertheless, most seeking and guiding electro-optical systems mounted on gimbal systems in, for example, guided missiles, are stability sensitive and, therefore, do not operate efficiently when installed on virtual axis homing type gimbal systems. Therefore, electro-optical systems are typically mounted on either external or internal axes homing gimbal systems and are, therefore, limited to size and field of regard meeting the limited performances of external and internal axes homing gimbal systems in these two aspects.

As will shortly be explained hereinbelow, the use of two axes in the first and third axial direction (i.e., axes 54 and 70) both of which being orthogonal to a mutual (i.e., the second) axial direction (and therefore may be defined as nominally parallel or coinciding), wherein movement around one of which (i.e., axis 70) is pivotal and therefore characterized by low friction combined with a low friction movement in the second axial direction (around axis 62), provides the homing gimbal system of the present invention with characteristics enabling mounting and controlling stability sensitive payloads (e.g., electro-optical systems) in spite the fact that the rotational movement around the other axis (i.e., axis 54) is characterized by high friction. Yet, the use of this type of assembly enables payloads to be large and have a diameter which is substantially limited only by the diameter of the object (e.g., guided missile nose) in which the system is installed.

When the homing system 50 of the present invention operates, initially, homing is performed only by rotational movements of intermediate gimbal 56 around axis 62 and pay load 64 around axis 70. As explained hereinabove these rotational movements are pivotal and, therefore, characterized by low friction. As sown in Figures 2a-b, the rotation of payload 64 around axis 70 is limited to a predefined relatively low angle 74. When homing around axis 70 is reaching a point in which angle 74 limits further homing in this direction, homing by arc-shaped gimbal 52 around axis 54 is initiated. The rotational movement performed by arc-shaped gimbal 52 is aimed at enabling payload 64 to further rotate around axis 70. Thus, arc-shaped gimbal 52 performs a follow-up motion characterized by high friction which does not affect the level of stabilization. Moreover, rotation of arc-shaped gimbal 52 is limited in its duration and, therefore, most of the time, the rotational movements characterizing system 50 are low friction. Hence, the homing gimbal system of the present invention enables mounting and efficient operation of stability sensitive payloads such as electro-optical systems.

The homing system of the present invention, therefore, enjoys the following advantages relative to the prior art configurations. As far as external and internal axes homing gimbal systems are concerned, the homing system of the present invention is less limited in payload size and in field of regard. As far as virtual axis type homing gimbal systems is concerned, the homing system of the present invention is not limited to stability insensitive payloads and may, therefore, be employed for homing of payloads such as electro-optical systems. As shown in Figures 3a-b and 4, the homing gimbal system 50 of the present invention employs three separate means to rotate each of its three basic components, arc-shaped gimbal 52, intermediate gimbal 56 and payload 64.

A first means is employed to slide first gimbal (e.g., the arc-shaped gimbal) 52 around its axis 54. The first means includes a first gear transmission 76. First gear transmission 76, as is understood to those with skills in the art, may acquire various forms, one of which is exemplified in Figures 3-4 and includes an external gimbal driving axis 78 attached to the external frame (indicated in Figures 3a-b by closed triangles), around which an external gimbal driving gear 79 rotates, driven by the operation an external transmission motor 80. Further rotating around external gimbal driving axis 78, is a first static balancing gear 82, itself connected to a second static balancing gear 84 which includes a static balancing weight 86 and rotates around a static balancing gear axis 88 connected to the external frame. Motor 80 provides the driving force to rotate external gimbal driving gear 79 around external gimbal driving axis 78 and, therefore, to rotate arc-shaped gimbal 52 around axis 54. First 82 and second 84 static balancing gears, and static balancing weight 86 provide the rotational movement of arc-shaped gimbal 52 around axis 54 with balance required to minimize susceptibility of stabilization level to external vibrations imposed by the carrying vehicle. It is however clear to those with skills in the art that first means employed to slide first gimbal (e.g., the arc-shaped gimbal) 52 around its axis 54 may alternatively employ a first belt transmission (not shown).

A second means is employed to rotate intermediate gimbal 56 around second axis 62. The second means includes a second gear transmission 90.

Second gear transmission 90 also may acquire many forms, one of which is exemplified in Figures 3-4 and includes a gear segment 92 fixedly attached to intermediate gimbal 56 and an intermediate transmission motor 94 fixedly attached to arc-shaped gimbal 52, and a gear 96 driven by motor 94 around an axis 98. Transmission of rotational movement from motor 94 to gear 96 and, from gear 96 to gear segment 92, enables rotating intermediate gimbal 56 around second axis 62. It is however clear to those with skills in the art that first means employed to rotate intermediate gimbal 56 around second axis 62 may alternatively employ a second belt transmission (not shown).

A third means is employed to rotate payload 64 around third axis 70.

The third means may acquire many forms, nevertheless, it is presently preferred and exemplified in Figures 3-4 that the third means would be a direct drive motor 100.

The rotation of each of the three basic components, arc-shaped gimbal 52, intermediate gimbal 56 and payload 64 of the homing gimbal system of the present invention is controlled by a control system. A special function of the control system is to correlate between the rotation of arc-shaped gimbal 52 around its axis 54 and, of payload 64 around its axis 70. This correlation enables system 50 to perform homing which is characterized by low friction most of the time and, therefore, to enable mounting and efficiently operating stability sensitive payloads such as electro-optical systems.

The homing gimbal system of the present invention is a novel system having two nominally parallel or coinciding axes around which a first gimbal and a payload are rotated and, an additional orthogonal axis around which an intermediate gimbal is rotated. When the homing gimbal system of the present invention operates, most of the time homing is performed by rotating the payload and the intermediate gimbal around their axes which are orthogonal to one another. These rotations are characterized by low friction. In a small part of the time homing is assisted by rotating the first gimbal around its axis. This rotation is characterized by high friction. Since in a majority of the time, homing is characterized by low friction, the homing gimbal system of the present invention is suitable to mount and efficiently operate stability sensitive pay loads. Furthermore, the built-up of the invented homing gimbal system enables, in many applications, to mount payloads limited in their size substantially only by the diameter of the object in which the system is installed. In addition, the homing gimbal system of the present invention provides the mounted payload with a wide field of regard.

Hence, the homing system of the present invention have profound advantages. When compared with the external and internal axes homing gimbal systems of the prior art, the homing system of the present invention is less limited in payload size and in field of regard, whereas when compared with the virtual axis type homing gimbal systems of the prior art, the homing system of the present invention is not limited to stability insensitive payloads and may, therefore, be employed for homing of payloads such as electro-optical systems. When the homing system of the present invention is compared with the homing gimbal system utilizing two axes of rotation which are not orthogonal (U.S. Pat. No. 4,802,640), the homing system of the present invention is less complex to manufacture, assemble and disassemble, less space consuming, yet, due to its built-up, provides a wider field of regard.

While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made.

Claims (26)

WHAT IS CLAIMED IS:

1. A homing gimbal system characterized by high spatial stability, wide field of regard and, large mounted apertures, the system comprising: (a) a first gimbal rotating around a first axis for homing in a first axial direction; (b) an intermediate gimbal being pivotally connected in a first connection to said first gimbal, said intermediate gimbal rotating around a second axis, said second axis being orthogonal to said first axis for homing in a second axial direction, said second axial direction being orthogonal to said first axial direction; and (c) a payload being pivotally connected in a second connection to said intermediate gimbal, said payload rotating around a third axis, said third axis being orthogonal to said second axis for further homing in a third axial direction.

2. A homing gimbal system as in claim 1, wherein said homing in said second axial direction and said further homing in said third axial direction are low in friction.

3. A homing gimbal system as in claim 1, wherein said first gimbal is an arc-shaped gimbal, said first axis is an imaginary axis and said rotation of said arc-shaped gimbal around said imaginary axis is by sliding said arc-shaped gimbal on sliding devices.

4. A homing gimbal system as in claim 1, wherein said first connection of said intermediate gimbal to said first gimbal is selected from the group of connections consisting of an internal connection and an external connection.

5. A homing gimbal system as in claim 1, wherein said first connection of said intermediate gimbal to said first gimbal is internal.

6. A homing gimbal system as in claim 1, wherein said second connection of said payload to said intermediate gimbal is selected from the group of connections consisting of an internal connection and an external connection.

7. A homing gimbal system as in claim 4, wherein said second connection of said payload to said intermediate gimbal is selected from the group of connections consisting of an internal connection and an external connection.

8. A homing gimbal system as in claim 5, wherein said second connection of said intermediate gimbal to said first gimbal is internal.

9. A homing gimbal system as in claim 1, wherein said intermediate gimbal is selected from the group consisting of a closed member and an open member.

10. A homing gimbal system as in claim 9, wherein said closed member has a shape selected from the group of shapes consisting of oval shapes, polygonal shapes and shapes including oval sections and polygonal sections.

A homing gimbal system as in claim 1, further comprising: first means for rotating said first gimbal around said first axis; second means for rotating said intermediate gimbal around said second axis; and third means for rotating said payload around said third axis.

12. A homing gimbal system as in claim 1 1 , wherein said first means is selected from the group consisting of a first gear transmission and a first belt transmission.

13. A homing gimbal system as in claim 1 1, wherein said second means is selected from the group consisting of a second gear transmission and a second belt transmission.

14. A homing gimbal system as in claim 1 1 , wherein said third means is a direct drive motor.

A homing gimbal system as in claim 1 1, further comprising: a control system controlling said rotation of said first gimbal, said intermediate gimbal and said payload around said first, second and third axes, respectively.

16. A homing gimbal system as in claim 15, wherein said control system includes a correlating function to correlate between said rotation of said payload around said third axis and said rotation of said first gimbal around said first axis.

17. A homing gimbal system as in claim 3, wherein said first connection of said intermediate gimbal to said arc-shaped gimbal is selected from the group of connections consisting of an internal connection and an external connection.

18. A homing gimbal system as in claim 17, wherein said second connection of said payload to said intermediate gimbal is selected from the group of connections consisting of an internal connection and an external connection.

19. A homing gimbal system as in claim 3, wherein said intermediate gimbal is selected from the group consisting of a closed member and an open member.

20. A homing gimbal system as in claim 19, wherein said closed member has a shape selected from the group of shapes consisting of oval shapes, polygonal shapes and shapes including oval sections and polygonal sections.

21. A homing gimbal system as in claim 3, further comprising: (d) first means to slide said arc-shaped gimbal around said imaginary axis; (e) second means to rotate said intermediate gimbal around said second axis; and (f) third means to rotate said payload around said third axis.

22. A homing gimbal system as in claim 21, wherein said first means is selected from the group consisting of a first gear transmission and a first belt transmission.

23. A homing gimbal system as in claim 21, wherein said second means is selected from the group consisting of a second gear transmission and a second belt transmission.

24. A homing gimbal system as in claim 21, wherein said third means is a direct drive motor.

25. A homing gimbal system as in claim 21, further comprising: (g) a control system controlling said sliding of said arc-shaped gimbal, and said rotations of said intermediate gimbal and said payload around said imaginary, second and third axes, respectively.

26. A homing gimbal system as in claim 25, wherein said control system includes a correlating function to correlate between said rotation of said payload around said third axis and said sliding of said arc-shaped gimbal around said imaginary axis. /j mark M. Friedman / Advocate, Patent Attorney Haomanim 7 street Beit Samueloff, 1st floor 67897 Tel Aviv