US3517563A

US3517563A - Gyroscopic platform assembly

Info

Publication number: US3517563A
Application number: US541874A
Authority: US
Inventors: Christian H Will Jr
Original assignee: Lear Siegler Inc
Current assignee: Lear Siegler Inc
Priority date: 1966-03-02
Filing date: 1966-03-02
Publication date: 1970-06-30
Anticipated expiration: 1987-06-30

Description

June 30, 1970 c. H. WILL; JR 3,517,563

GYROSCOPIC PLATFORM ASSEMBLY Filed March 2, 1966 4 Sheets-Sheet 1 FIG. j

a) a) a) INVENTOR.

CHRISTIAN H. WILL, JR.

' ATTORNEYS June 30, 1970 c. H. WILL, JR

GYROSCOPIC PLATFORM ASSEMBLY 4 Sheets-Sheet 3 Filed March 1966' JNVENTOR. CHRISTIAN H. WILL.JR.,

ATTORNEYS.

June 30, 1970 C. H. WILL, JR

GYROSCOPIC PLATFORM ASSEMBLY 4 sheets sheet 5 Filed March 2, 1966 6lb 64b FIG.54

' ATTORNEYS June 30, 1970 c. HQWILL, JR

GYRO SCOPIC PLATFORM ASSEMBLY Filed March 2, 1966 4 Shets-Sheet 4.

. mm mm 00 INVENTORY v CHRISTIAN H. WILL, JR.

y v ATTORNEYS United States Patent 3,517,563 GYROSCOPIC PLATFORM ASSEMBLY Christian H. Will, Jr., Grand Rapids, Mich., assignor to Lear Siegler, Inc. Filed Mar. 2, 1966, Ser. No. 541,874 Int. Cl. G01: 19/02 US. Cl. 745.34 11 Claims ABSTRACT OF THE DISCLOSURE This invention relates to gyroscopic platform assembhes utilizing an inside-out gimballing arrangement wherein the component mounting platforms are individually and independently rotatably affixed to a pair of axially aligned supports. The relative rotational positions of the platforms are maintained by aflixing a circular rack gear to the inner face of each of the platforms. A pair of spur gears each having a diameter substantially less than that of the rack gears are carried by the succeeding outer gimbal frame so as to transmit the rotational thrust of one of the platforms directly to the other platform.

This invention relates to gyroscopic platform assemblies and, more particularly, to such assemblies utilizing an inside-out gimballing arrangement.

There are two major modes of gimballing which may be utilized in the design and fabrication of stabilized platforms. These are traditionally denoted as the outside-in and the inside-out gimballing arrangements. The outside-in is, perhaps, the more conventional of the two gimballing arrangements. The gyros and accelerometers are mounted in a compact package and the gimbal rings required to give the necessary degrees of freedom are wrapped around this center. When utilizing this arrangement, all of the gimbal rings must be of sufficient dimension to clear the instrument package when they are rotated. This factor results in platforms of relatively large size.

In the inside-out gimballing arrangement, the gyros and accelerometers have traditionally been mounted in dumbbell fashion, connected by a stiff post. Gimbals are 7 built up around the post to provide freedom of movement about the required area. The dumbbell arrangement of instruments is born within the next outer gimbal (usually the inner roll gimbal) such that it is free to rotate about one of the positional axes (usually the azimuth axis). The inside-out gimballing arrangement results in a potentially more compact package since only the outer gimbal need be of sufficient size to clear the instrument package.

When four-gimbal platforms are necessitated by the particular working environment, the inside-out gimballing arrangement has the additional advantage of positioning the sensitive components such that access to them may be gained easily without disassembling the entire gimballing structure. This important feature allows interchange and repair of components with relative ease and with down periods of relatively short duration.

As will be appreciated by those skilled in the art, one of the major problems in stabilized platform design is the effective incorporation within the system of torquers, resolvers, pick-offs, switches and the like. The major problem which heretofore has plagued designers of inside-out gimballing arrangements is the incorporation of these sensing and control elements into the gimbal joint between the dumbbell-shaped gimbal or component support platform and the succeeding outer gimbal. Because of balance considerations, the weights at the opposite ends of the dumbbell shaft must be approximately equal. It has been customary to connect these weightsi.e. the

"ice

component mounting platforms and the components thereon-by means of a solid shaft which extends through and is rotatably born by the succeeding outer gimbal. This arrangement does not permit the utilization of conventional axially symmetrical slip rings, brush blocks, torquers, resolvers and the like. Therefore, complicated gear trains are necessary to transmit rotational position signals to and from the dumbbell-shaped gimbal. Gear trains of this type rapidly become very complicated. In addition to being extremely expensive to fabricate, any slight discrepancy in the gear surfaces results in a cumulative error which well may render the system unusable. Modern day space requirements necessitate gyroscopic platforms which are capable of functioning continually with a very slight error. It follows, therefore, that any component such as a gear train which inherently introduces positional errors into the system must be avoided. Therefore, the tendency of manufacturers has been to accept the relatively large instrument packages and difficult access procedures inherent in the outside-in gimballing arrangements in order to reduce positional errors to within acceptable limits.

It is an object of this invention to provide a gimballing arrangement for utilization in three and four gimball platforms which capitalizes on the inherent advantages of an inside-out gimballing arrangement and, yet, is not subject to the disadvantages which have been previously associated therewith.

More particularly, it is an object of this invention to provide a gimballing arrangement which provides a relatively small component package.

It is an object of this'invention to provide a gimballing arrangement wherein access to the critical components may be gained without disassembling the entire gimballing system.

It is an object of this invention to provide an insideout gimballing arrangement which does not require the utilization of complicated gear trains to transmit rotational position signals to and from the innermost gimbal, and thus to reduce both the expense and inherent cumulative error of the system.

These and other objects of this invention will be clearly understood by reference to the following specifications and accompanying figures in which:

FIG. 1 is a stick diagram of a representative 3 gyro four-gimbal platform;

FIG. 2 is a fragmentary repspective, partially in crosssection, of a four-gimbal platform embodying the gimballing arrangement which is the subject of this invention;

FIG. 3 is a perspective view of the inner roll-azimuth axes platform assembly;

FIG. 4 is a side-elevational view, partially in crosssection, of the inner roll gimbal; and

FIG. 5 is a cross-sectional view taken along line VV of FIG. 3.

Briefly, this invention comprises an inside-out gimballing arrangement wherein the component mounting platforms are each rotatably affixed to a distinct one of a pair of axially aligned sleeves projecting from opposite sides of the succeeding outer gimbal. Brush blocks are affixed to the inner peripheries of the sleeves and a slip ring inserted thereinto. The slip ring has a mounting cap affixed to the adjacent platform whereby it rotates with respect to its associated brush block when that platform experiences rotation relative to the succeeding outer gimbal. Means are provided whereby stationary components of resolvers, torquers, and the like may be affixed to the succeeding outer gimbal symmetrical to the mounting sleeve. Similarly, the rotating components of these devices may be aflixed to the component bearing platform symmetrical about the support sleeve.

The rotational positions of the two platforms are maintained by providing a circular flange aflixed to each of the component supporting platforms. The flanges converge into the space between the two platforms and have circular rack gears on their facing surfaces. A pair of spur gears having diameters substantially less than the diameter of the rack gears are carried by the succeeding outer gimbal frame in such a manner that they transmit the rotational thrust of one of the platforms directly to the other platform, thus insuring that the relative angular positions of the two platforms with respect to the succeeding outer gimbal will always be identical.

Referring now to the figures, a preferred embodiment of this invention will be described in detail. FIG. 1 is a stick diagram of a conventional 3 gyro, four-gimbal platform. This diagram will be utilized as a means of presenting a typical environment in which the subject matter of the present invention finds usage. This diagram is not intended to illustrate the details of the inventive gimballing arrangement, nor does it do so. On the contrary, it is virtually impossible to accurately depict an inside-out gimballing arrangement in stick form. Therefore, the diagram is functional, rather than structural, in nature.

As will be seen by reference to FIG. 1, the frame has an outer roll gimbal 11 pivotably joined thereto. Proceeding inwardly, pitch gimbal 12 is jointed to outer roll gimbal 11, inner roll gimbal 13 is pivotably jointed to pitch gimbal 12, and azimuth gimbal 14 (also commonly referred to as the component mounting platform) is pivotably jointed to inner roll gimbal 13. Azimuth gimbal 14 carries three accelerometers 15 and three gyros 16-. These components, as is well-known in the art, are positioned such as to provide positional signals within the coordinate system defined by azimuth axis 17, pitch axis 18, outer roll axis 19 and inner roll axis 20.

As is also well-known, the gyroscopic components 16 each have leveling axes with torquers and pickoffs mounted thereon. Thus, azimuth leveling axis 21 has torquer 22 and pickoif 23 associated therewith, roll leveling axis 24 has torquer 25 and pickoff 26 associated therewith and, pitch leveling axis 27 has torquer 28 and pickoif 29 associated therewith.

As is similarly well-known, the gimbal joint between the outer roll gimbal and the pitch gimbal incorporates a torquer 30, a synchro 31, and a pitch segment switch 32. The gimbal joint between the azimuth gimbal and the inner roll gimbal incorporates a torquer 33, a synchro 34, and one or a plurality of resolvers 35. The gimbal joint between the inner roll gimbal and the pitch gimbal incorporates torquer 36 and synchro 37. Finally, the gimbal joint between roll gimbal 11 and frame 10 incorporates torquer 38, synchro 39, and a roll segment switch 40. Merely by way of example, the pitch leveling axis may be limited to rotational movement of a plus or minus five degrees, the azimuth leveling axis to plus or minus five degrees, the roll leveling axis to plus or minus five degrees, and the inner roll axis to a plus or minus ten degrees. The remainder of the axes-Le. the outer roll, azimuth and pitchare, of course, free to rotate a full 360 degrees.

All of the functional interrelationships of the component shown in FIG. 1 are well-known in the art. The problem, as pointed out previously, is one of packaging and structurally interrelating these components such that thedesired degree of accuracy may be obtained from a structure which is as small as possible and within which access may be gained to the critical components with relative ease. Referring now to FIGS. 2 through 5, the insideout gimballing arrangement which is the subject of this invention will be illustrated.

FIG. 2 shows a housing having mounting means 51 whereby it may be afiixed to the vehicle within which its components are to function. The housing 50 encloses an outer roll gimbal 52, a pitch gimbal 53, and an inner roll gimbal 54. The reference numeral 55 indicates generally the housing-outer roll gimbal joint, the reference numeral 56 the outer roll-pitch gimbal joints, and the reference numeral 57 the pitch-inner roll gimbal joints. A plurality of balancing lugs 58 are positioned throughout the system in a well-known manner such that the overall structure may be balanced prior to insertion in the vehicle.

The inner roll-azimuth axis platform assembly 60 comprises a pair of axially aligned sleeves 61a and 61b which project from the circular planar midsection 62 of inner roll gimbal 54. The reference letters a and b will be utilized hereinafter to indicate those corresponding components on opposite sides of inner roll gimbal 54, however, these reference letters may henceforth be omitted in the discussion of any component part of the instant invention for the sake of brevity and clearness. As will become apparent, the platform structures on opposite sides of inner roll gimbal 54 are identical, the overall structures differing only in the types of components and controls which are associated therewith. The circular planar midsection '62 of inner roll gimbal 54 has a pair of circular upstanding flanges 63a and 63b extending from opposite sides thereof. Each of these flanges includes a

detent

64a and 64b respectively. Planar midsection 62 is carried by a pair of conventional mounting wheels 65 aflixed to opposite symmetrical extremities thereof.

The component support platforms 74a and 74b are circul-ar and each has an inner depending circular flange 75 associated therewith (see FIG. 5). Flanges 75 have detents 76 and bearing retainer notches 77 for-med integrally therewith. Spaced radially outwardly from inner depending circular flange 75 on component platform 74 is an outer depending circular flange 78. Flange 78 also has a detent 79 integrally associated therewith. A circular gear flange 80 is radially displaced from flanges 75 and 78 and, conveniently, forms the outer boundary of component support platforms 74. Circular gear flanges 80a and 8% have circular gear racks cut in their facing surfaces as will become apparent hereinafter.

The component support platforms 74 are rotatably mounted to support sleeves 61 by means of inner and outer bearing assemblies 66 and 67. Each of these bearings has an inner race 68 and an outer race 69 and the two assemblies are spaced by means of an inner spacer 71 and an outer spacer 72. As will be seen by reference to FIG. 5, inner spacer 71 is associated with inner bearing races 68 and outer spacer 72 is associated with outer bearing races 69. By varying the lengths of these spacers, minor imperfections in the width of the bearing races may be compensated. The bearing assemblies are positioned adjacent to the inner roll gimbal 54 by means of a bearing retainer notch 73 on sleeve 61 and bearing retainer notch 77 on component support platform 74. Circular bearing locks 82 and 95 are screwed into their respective threaded receviers on sleeve 61 and cap 74. Bearing locks 82 and 95 function to control and maintain the axial displacement of platform '74 with respect to inner roll gimbal 54. Shims 99a and 99b are used to set the axial position of gears 80a and 8% so that minimum gear tooth clearance can be maintained between

gear teeth

80a and 80b, and the working faces of spur gears 91 and 92.

Mounted between circular planar midsection 62 of inner roll gimbal 54 and platform 74 by means of detents 64, 76, and 79 are a series of resolvers and torquers. For example, resolver rotor 83 is aflixed to platform 74 while its adjacent stator 84 is aflixed to inner roll gimbal 54. Similarly, a torquer winding 85 might be affixed to platform 74 while its associated permanent magnetic field 86 is aflixed to inner roll gimbal 54. As is well-known in the art, the relative rotation between the associated compo nents of these devices is controlled by or controls particular functions within the platform and vehicle with which it is associated. As a rule, in devices of the type shown, three resolvers and only one torquer are utilized. Therefore, both of the control component spaces in the a section of the assembly might contain resolvers while only one of the control spaces in the b section contains a resolver, the other such space being reserved for a torquer.

A conventional slip ring 87 is positioned within brush block 88 by means of a slip ring retainer cap 82 which is aifixed to platform 74. Thus, electrical signals may be transmitted from the 360 degree pivotable support platform 74 without necessitating the use of flexible leads. It will be appreciated by those skilled in the art that all of the components shown in FIG. are circular or cylindrical in plan view whereby they may be mounted symmetrically about sleeves 61.

It is, of course, necessary that the two support platforms 74a and 7 4b be slaved in some manner to insure that their relative radial displacements with respect to. inner roll gimbal 54 always remain the same. As pointed out previously, past devices have utilized a solid shaft extending through inner roll gimbal 54 and connecting the facing support platforms 74 for this purpose. The presence of this shaft, however, made it impossible to utilize conventional Slip ring and brush block connections and thus necessitated the use of complicated gear trains to transmit the rotational information to and from the components mounted on platforms 74. That is to say, the use of the solid shaft foreclosed any possibility of axially symmetrically mounting the control and signal components atthe gimbal joint. It will be obvious from an examination of FIG. 5 that-the present invention obviates this problem.

The relative rotational displacements of platforms 74a and 74b with respect to inner roll gimbal 54 is maintained constant by means of two spur gear assemblies 90 which are carried by opposite sides of inner roll gimbal 54. These spur gears engage the circular gear rack faces of flanges 80 on platforms 74 and transmit any rotational displacement of one such platform to the other. While it would be possible to utilize only one spur gear assembly 90, it has been found that the tendency for these gears to jam or be pulled free from their intermeshing relationships with flanges 80 is alleviated by utilizing two such assemblies displaced 180 degrees from one another. Conveniently, spur gear assemblies 90 may be carried at points on circular planar midsection 62 of inner roll gimbal 54 which are displaced 90 degrees from the mounting Wheels 65. Thus, when one of the platforms 74 experiences any slight degree of rotation, that same degree of rotation is positively transmitted to its mating platform, assuring that the two will maintain an identical angular displacement with respect to inner roll gimbal 54.

It is important that the diameter of spur gears 91 and 92 be kept relatively small in relation to the diameter of the circular gear racks 80. If, for example, a ratio of 5 to l is utilized, any slippage tendency within the spur gear assemblies 90 will be reduced by a factor of 5 prior to the time that this slippage has been transmitted to the in dividual component mounting platforms 74.

The bearing construction shown in FIG. 5 whereby the component mounting platforms may rotate about sleeves 61 has a number of distinct advantages; For example, the sizes of these spacers 71 and 72 may be individually determined so as to compensate for varying width bearing races. The thickness of shims 99 may be varied so as to insure that the axial displacement of

circular gear racks

80a and 80b will precisely accommodate

spur gears

91 and 92, thus preventing any slippage in the mechanical servoing connection. Any tendency towards overall axial bearing play may be eliminated by controlling the size of spacers 71 and 72 and the individual tightness of bearing caps 82 and 95.

Once the platforms 74a and 74b have been mounted, the gyroscopic instrument packages 93a and 93b may be atfixed thereto in any conventional manner. In addition to gyroscopes and accelerometers, instrument packages 93a and 93b will undoubtedly include electronic modules and other types of conventional components. In the device shown, for example, two of the gyros might be placed on platform 74a while one gyro and the three accelerometers are positioned on platform 74b.

From an examination of FIG. 2, it will be apparent that the present construction enables components to be utilized at the inner roll-azimuth axis joint which are highly similar, if not identical, to those utilized at the other gimbal joints within the system. What this invention has accomplished effectively, is to allow the utilization of two conventional gimbal joints such as indicated at 57 in back to back servoed relationship whereby the gyroscopic components may be mounted on diverging, instead of facing, sides thereof. The sleeves 61a and 61b allow usage of conventional slip rings and brush blocks at the inner roll gimbal-azimuth axis joint. Thus, platforms 74a and 74b and the components mounted thereon may rotate 360 degrees about the azimuth axis without requiring the utilization of complicated gear trains to control and power them. The construction shown in this invention retains the advantages of utilizing integral components on the axes of the gimbal joints without sacrificing the size reduction and easy access to parts inherently associated with inside-out gimbal structures.

In operation, as the vehicle experiences a maneuver about the azimuth axis, platforms 74a and 74b rotate about their respective mounting sleeves 61a and 61b to maintain the position dictated by the azimuth gyro. The spur-gear assemblies 90, in conjunction with the circular gear racks 80, insure that the two facing platforms 74a and 74b will not tend to experience a radial displacement relative to one another. This construction is desirable even when separate torquers are utilized for each of the gyro platforms and absolutely essential when, as usual, only one torquer is utilized to control the position of both of the platforms.

Signals are transmitted to and from the instrument packages by means of slip rings 87 and brush blocks 88. These signals, as is well-known in the art, are transmitted to various components within the system such that positioned signals may be derived at the outputs thereof.

While a preferred embodiment of this invention has been described in detail, it will be apparent to those skilled in the art that a number of modifications thereof may be executed without departing from the spirit and scope of this disclosure. Such modifications are to be deemed as included in the following claims unless these claims, by their language, expressly state otherwise.

I claim:

1. An inside-out gimballing arrangement comprising:

a gimbal having a pair of axially aligned sleeves extending from opposite sides thereof; and

a component mounting platform rotatably connected to the outer circumference of each of said sleeves such that said gimbal lies between said platforms, said platforms being rotationally slaved together by means of circular gear racks affixed to the surfaces thereof, said gear racks having their toothed surfaces positioned in parallel planes, and gear means coupling said gear racks.

2. The combination as set forth in claim 1 which further comprises slip ring and brush block components positioned within each of said sleeves, one of said components being aflixed to said gimbal and the other being affixed to the adjacent platform.

3. The combination as set forth in claim 1 wherein said gear means comprises two sets of spur gears rotatably mounted on said gimbal, each of said sets consisting of two spur gears which intermesh with each other and with the circular gear racks on said platforms, said sets being positioned at diametrically opposite locations on said gear racks.

4. The combination as set forth in claim 3 wherein the diameter of said spur gears is substantially less than the diameter of said circular gear racks.

5. A gimballing system comprising:

a gimbal having a pair of aligned supports extending from opposite sides thereof;

a component mounting platform rotatably connected to each of said supports such that said gimbal lies between said platforms;

circular flanges affixed to the surfaces of each of said platforms, said fianges each having circular gear racks thereon; and I gear means coupling said gear rack surfaces whereby said platforms are rotationally slaved.

6. The combination as set forth in claim 5 wherein said aligned supports are hollow, said platforms being mounted to the outer peripheries thereof.

7. The combination as set forth in claim 6 wherein said supports have slip ring and brush block components inserted in the hollow sections thereof, one of said components being affixed to said gimbal and the other being affixed to the adjacent platform.

8. The invention as recited in claim 7, wherein each of said pair ofaligned supports is fixedly connected to said gimbal.

9. In an inertial platform having an outer roll gimbal, a pitch gimbal and an inner roll gimbal, the combination comprising:

a pairof axially aligned sleeves extending from opposite sides of said inner roll gimbal;

a component mounting platform rotatably connected to the outer circumference of each of said sleeves, said platforms serving as azimuth gimbals having gyroscopic accelerometer components mounted thereon; and

means coupling said platforms whereby said platforms are rotatably slaved together.

10. The combination as set forth in claim 9 which further comprises slip ring and brush block components positioned within each of said sleeves, one of said components being affixed to said inner roll gimbal and the other being aflixed to the adjacent platform.

. 11. In an inertial platform having a gimbal, the combination including: a

a pair of oppositely-directed supports rigidly connected to said gimbal; and

a pair of component mounting platforms, each connected to one of said supports and rotatable with respect thereto, said platforms serving as azimuth gimbals having gyroscopic and accelerometer components mounted thereon wherein said component mounting platforms are slaved together preventing relative movement therebetween.

References Cited UNITED STATES PATENTS 12,949,785 8/1960 Singleton et al 74 5.34

ROBERT F. STAHL, Primary Examiner