MECHANICALLY STABILIZED PLATFORM SYSTEM

Abstract: A compositely statically balanced mechanically stabilized platform system including a stabilized platform (14) having at least one pivotal axis (45, 56), a supporting structure (12), a pendulum (62), a non-rigid connection (52, 53) for orienting the platform with respect to the pendulum, a gyro assembly (30, 39) mounted for rotation about a precession axis perpendicular to a pivotal axis of the platform. The gyro assembly itself is statically balanced about its precession axis and has restraining springs (59, 60) for orienting the spin axis of the gyro with respect to the gyro assembly supports. The system further includes an equipment platform (13) preferably mounted remotely from the platform and mechanically connected thereto by a linkage assembly (26-29) which transmits motion of the stabilizing assembly to the equipment platform. In one embodiment the system is constructed as a single integrated unit (Fig. 8). In several embodiments the gyro azimuth frame is supported on bearings (40, 41) which permit unrestrained rotation in the azimuth plane. Another embodiment (Fig. 11) utilizes the combination of a non-rigidly coupled auxiliary pendulum (469) and a bias spring (470) coupled to the support structure (477) for orienting the statically balanced platform system with respect to the support structure.

Description: MECHANICALLY STABILIZED PLATFORM SYSTEM Technical Field This invention relates generally to gyrosco- pically stabilized platforms, and more specifically to combination-element gyro stabilized platform systems, and specifically to statically balanced, mechanically stabilized platform systems, such as might be used to support antennas in mobile applications. A mechanically stabilized platform system is one in which a gyroscopic torsional impulse absorption system alone is used to absorb torsional impulses caused by vehicle motions. As used herein a gyrosco¬ pic torsional impulse absorption system is defined as comprising gyroscopic apparatus including a pair of gyroscopic rotors, means for independently mounting each of said rotors for rotation about one axis and for precession about another axis at an -angle to said one axis, said axes of each rotor being respectively parallel and perpendicular to said axes of said other rotor, and centering means operatively connected to each of said axes mounting means. Background Art Mechanically stabilized platform systems can provide a stable mounting platform for devices such as cameras, directional antennas, and sensing and recor¬ ding instruments when these devices are used on ships, aircraft, and land vehicles. However, direct mechan¬ ically stabilized platforms have had only limited use in the past in such applications because they suf- fered from three major shortcomings: (1) they were relatively inaccurate, (2) they had large and awkward OMPI configurations, and (3) they were susceptible to destabilization from yaw/turning and other azimuth motions combined with roll or pitch motions. Regarding the first problem of poor accu- racy, numerous prior art patents taught that the plat¬ form system should be pendulous so as to orient the platform to the vertical. That result was obtained, but the pendular characteristic also caused the plat¬ form to be responsive to horizontal accelerations. Pendulous platforms having this undesirable character¬ istic are described by U.S. Patents 1,645,079 - • Titterington, 1,083,370 - Luyken, 1,186,856 and 1,236,993 - Sperry, 1,999,897 - Fieux, 2,199,294 - Selig ann, and 4,020,491 — Bieser, et al, among others. Making the platform system pendulous as taught by these patents created the interesting, and undesirable, paradox that the pendular effect used to provide the system with a long-term reference orienta¬ tion was responsible for the largest short-term dis- turbances to platform orientation. These short-term disturbances, although attenuated by gyroscopic action, constitute one of the two major effects which limit the accuracy of such previously known mechanic¬ ally stabilized platform systems of the pendulous type. The other major accuracy-limiting effect is discussed later. The problems of pendulosity were avoided by other systems, such as those disclosed in U.S. Patents 1,032,022 - Petravic, 1,573,028 - Bates, and 2,811,042 - Kenyon by making such systems statically balanced. However, each of these systems require periodic manual adjustment to establish a desired reference orienta¬ tion. Still other patents including 1,906,719 - Richter, 1,324,477 - Tanner, and 3,472,770 - Flannelly f QMPI describe statically balanced gyroscopic systems which are oriented with respect to their support frame by mechanical springs. Again, the pendulosity problems were avoided, but in each of these systems the orien- tation of the stabilized element changed in correspon¬ dence with long-term changes in support frame orientation. U.S. Patent 2,537,772 - Dawson differs from the above noted patents in that it relies upon some unspecified "self-erecting" characteristic of a gyro¬ scope in a statically balanced position-stabilizing device to eliminate the need for establishing any par¬ ticular reference direction. The existence of any such self-erecting characteristic is contrary to the most fundamental property of a gyroscope, namely that when there is no moment of force acting upon the gyro¬ scope, the axis of rotation maintains a fixed direc¬ tion in inertial space. U.S. Patent 4,193,308 - Stuhler, et al describes a system which is statically balanced as a whole but in which the gyro assemblies are made indi¬ vidually pendulous. Regarding sensitivity to horizon¬ tal accelerations the result of this arrangement is the same as if the platform were made pendulous and disturbing horizontal accelerations were applied at right angles to those acting on the actual system. The second major problem associated with the prior art, namely large and awkward configuration, resulted from constructing the platform system inclu- ding the operating equipment as a single integrated assembly. Such systems typically were structurally inefficient and required large amounts of dead coun¬ terweight. As a result they were characterized by low structural resonant frequencies, which resulted in poor tolerance to vibrations and consequent high vibration stresses on platform equipment. While U.S. Patent 2,924,824 - Lanctot proposed to solve this problem in a servo-stabilized system, it requires a large, cylindrical, clear volume of space for push-rod assemblies as they are rotated together with a scan¬ ning antenna about a requisite common axis in an inte¬ grated assembly. U.S. Patent 1,621,815 - Schueller proposes an arrangement which separates the overall system into two interconnected assemblies, but its embodiments are such that yaw and turning motions will be superimposed on both the roll and pitch axes of the "stabilized" platform. The third major problem area in the prior art, destabilization from yaw/turning motions combined with roll or pitch motions, resulted from such motions being converted into platform disturbing torques by the gyros whenever the gyro spin axes were not exactly vertical. If the gyro's spin axis is exactly ver- tical, then rotations of the gyro support frame about that vertical axis, as in yawing or turning, will have no effect. However, if the gyro spin axis has preces- sed some angle away from vertical as a result of reac¬ ting to a disturbing torque about the roll or pitch axis, then a component of the gyro's angular momentum will exist in the horizontal plane. If there are no motions in the horizontal plane then nothing will happen, but if the horizontal rotations do occur they will be coupled into the platform by the gyro's hori- zontal component of momentum and will tend to mis- level the platform. Significant errors in platform orientation can occur, and in extreme cases the plat¬ form will become completely destabilized. U.S. Patent 2,199,294 - Seligmann recognized and solved the prob- lem of combined motions by stabilizing the entire platform system about a vertical axis relative to the meridian. While technically valid, this arrangement has the serious practical disadvantage of requiring the use of slip-rings or rotary joints on all connec¬ tions to equipment mounted on the stabilizing plat¬ form. U.S. Patent 4,020,491 - Bieser, et al describes embodiments comparable to those of patent 2,199,294 - Seligmann regarding turntable mounting of the entire system, and suggests that structural means be employed to lock the gyro pivot axis during rapid turning man¬ euvers to minimize torquing errors. Such locking has the undesirable effect of disabling the stabilization system during maneuvers when it might be needed most. U.S. Patent 4,193,308 - Stuhler, et al describes a fluid dashpot caging system for use in stabilized platforms in which the entire system may be rotatably mounted on a pedastal to permit azimuth orientations of the platform. Such azimuth orientation motions, if occuring simultaneously with roll or pitch motions, would of course cause the above-described torquing errors. Summary of the Invention The first main feature of this invention provides for the platform system to be statically compositely balanced about its support axis and to include automatic reference orienting means which include an auxiliary non-rigidly coupled pendulum. The differences between previously known systems which are rigidly pendulous and a system constructed in accordance with the present invention which is both statically balanced and non-rigidly coupled to an auxiliary pendulum, heretofore overlooked by all of the prior art, are fundamental to the unforeseeable improvements discovered by me. In rigidly pendulous systems of the prior art, the dynamic characteristics are essentially immutable, whereas almost any desired set of dynamic characteristics can be designated and built into systems constructed in accordance with the present invention. To illustrates if a rigidly pendulous system of given weight/inertia is to have a given torque gradient-toward-vertical then there exists only one value for the pendular length. But this pendular length - pendular weight/inertia combi¬ nation will have a characteristic natural period of oscillation over which the designer has no control. Torque gradient as used herein is defined as having the dimensions of inch-pounds per degree, or other equivalent units. By contrast, in a statically balanced-plus-auxiliary pendulum system a given torque gradient-toward-vertical can be obtained with an infi¬ nite variety of pendulum weight/pendulum length combi- nations. And makes possible a combination which pro¬ duces any pre-selected value for the period of natural oscillation. This has important consequences for practical stabilization systems because such systems should have natural oscillation periods which will not be excited in their operating environment. For example, ship vibrations fall into two separate bands in the frequency spectrum; those with periods in the range of about 0.02 to 0.25 seconds caused by the propulsion system and other machinery, and those in the range of about 4 to 100 seconds caused by gross ship and wave motions. Between these two bands there is a "window" in the frequency spectrum, from about 0.25 to 4 Hz, which is almost free of vibrations. The auxiliary pendulum with its suspension and coupling in O PI the present invention is designed to have a natural period which falls within this band so that it is left essentially free of shipboard excitations. In con¬ trast, rigidly pendulous systems as taught in the prior art characteristically have natural periods in the range of 10 to 30 seconds which make them suscep¬ tible to excitation, and hence orientation inaccura¬ cies, from gross ship and wave motions. This is, in fact, the second major effect referred to above which limits the accuracy of pendulous mechanically stabil¬ ized platform systems as taught in the prior art. It should be noted that a statically bal¬ anced stabilized platform system does not require the continuous application of reference orienting means; such means need be applied only long enough and fre¬ quently enough to prevent the accumulation of drift and wandering errors. The present invention allows for reducing the coupling effect between platform and auxiliary pendulum under conditions when the pendulum is subject to orientation errors, such as from hori¬ zontal accelerations induced by ship motions. Such de-coupling is not possible in rigidly-pendulous plat¬ form systems. This feature in the present invention is used in conjunction with the other features described herein and accordingly allows constuction of much more accurate mechanically stabilized platform systems than were heretofore possible. The phrase "statically compositely bal¬ anced", or simply "compositely balanced", as used above refers to the condition in a system wherein the pivotal members will remain at any initial orientation in the presence of an accelerating field, such as gravity. For an assembly pivotally mounted to a supporting structure about a single axis this condi- O PI tion will exist if the center of gravity of the system lies on the pivotal axis. For a system composed of two interconnected rigid assemblies, each of which is separately supported on its own pivotal axis, this condition will exist if any unbalance of one assembly about its pivotal axis is compensated by an equal but opposite unbalance of the other assembly about its pivotal axis. Arranging for the system to be static¬ ally compositely balanced makes it insensitive to all accelerations. The advantages therefrom have been noted above. In the present invention the long-term ref¬ erence orientation established by the auxiliary pendu¬ lum is transferred to the stable platform by non-rigid coupling means therebetween. The components used for this coupling can be designed to provide many kinds of torque restoration functions through selection and design of combinations of various devices which pro¬ duce forces or torques, such as linear springs, non- linear springs, dash-pots, magnets and other magnetic devices, and various other pneumatic, hydraulic, elec¬ tric and mechanical devices. Inclusion of viscous damping or other energy-absorbing mechanisms in the torque restoration function for the purpose of damping out platform oscillations is desirable. An example of a desirable torque restoration function is one which creates an increasing torque with increasing angular displacements for small dis¬ placements, and which maintains that torque at a con- stant value for all larger displacements, and which includes a damping factor. Another example of a desirable torque restoration function is one which provides strong coupling during periods when the pendulum has small vertical errors, and which provides only weak or even no coupling at all when the pendulum has large vertical errors. A second feature of this invention provides for the stabilization system to be constructed as two separate but inter-connected assemblies, each part of which is optimally designed for its particular func¬ tions. The two assemblies comprise the stabilizing assembly, and the stabilized platform including its operating equipment. These two assemblies are inter- connected with any variety of position or motion transmitting means such that the stabilized platform always has the same angular orientation with respect to a reference plane as does the stabilizing assembly. Significant improvements in size, weight, and stiffness characteristics result from this feature of the present invention. It also allows stable plat¬ forms not originally designed for direct mechanical stabilization to be economically converted to that type. A further advantage of this feature is that it permits the stabilizing assembly to be placed at a location where its operating environment is less severe than that imposed on the operating equipment which it stabilizes. For example, the assembly could be mounted below deck rather than on a mast exposed to the elements. Still another advantage of this feature is that larger disturbing impulse absorbing capacity can be obtained from a given amount of gyro momentum as a result of having greater spacial design freedom, hence allowing larger gyro precession axis operating ranges. Another main feature of this invention pro¬ vides for the gyro assembly support frame to be rota- tably mounted on its own independent azimuth bearings within the stabilizing assembly. This arrangement minimizes the problems associated with yaw/turning combined with roll or pitch motions described above because the gyro assemblies experience only slight azimuth motions with respect to inertial space. Hence as far as the gyro assembly support frame is concerned yaw or turning motions effectively do not occur. An observer could note relative motion occuring between the gyro support frame and the ship but it would in fact represent the support frame remaining static in inertial space while the ship turned under it. From the above description it should be clear that this invention involves three independent but inter-related features. An optimum stabilized system according to the teachings herein would be (1) statically balanced with auxiliary pendulum cen¬ tering means, (2) would be constructed as two separate but interconnected assemblies, and (3) would utilize a gyro assembly support frame mounted on its own azimuth bearings. Other configurations may of course be con- structed which do not incorporate all three of these features, nevertheless use of any one feature alone, or with either or both of the others represents sub¬ stantial and unexpected improvements over the prior art. For a fuller understanding of the pinciples which apply to this invention and of the descriptions which follow, it will be noted that a mechanically stabilized platform system operates on the equivalency and convertibility of torsional impulse and angular momentum. Torsional impulses which tend to disturb the platform are resisted by changes in the angular momentum of the system. These changes appear in the form of gyro spin axis reorientation, usually referred to as precession. When a disturbing torque occurs the gyro first goes through a transient oscillating motion about its precession axis, and then begins to rotate about that axis at a constant rate. In the process a small angular offset occurs to the platform. Preces- sion will continue until either the torque is removed, or the gyro reaches a precession angular limit, which¬ ever occurs first. When the disturbing torque is removed precession ceases and the platform's angular offset is corrected by the reference orientation means employed. These effects can be described and analyzed by means of the general equations for rotation of a body about its mass center. Brief Description of the Drawings Figure 1 is a partially broken away and sectioned side elevational view of one embodiment of the present invention. The upper portion of Figure 1 represents the stabilized platform of such a system and the lower portion represents the stabilizing assembly portion; Figure 2 is a horizontal section taken along line 2-2 in Figure 1 showing the right angled gimbal mounting detail; Figure 3 is a horizontal section taken along line 3-3 in Figure 1 showing the right angled gimbal and gyro mounting detail; Figure 4 is a partially broken away and sectioned side elevation view of a second embodiment of a mechanically stabilized platform system in which there is a single stabilized pivotal axis; Figure 5 is a horizontal section taken along line 4-4 of Figure 4 showing the gyro mounting gimbal; Figure 6 illustrates a portion of a third embodiment in which a single coil spring is used as part of the system's reference orientation means; Figure 7 is a horizontal section taken along line 7-7 in Figure 6; Figure 8 is a partially broken away and sec¬ tioned side elevation view of another embodiment in which the equipment being stabilized is mounted directly on the stabilization assembly; Figure 9 is a partial front elevation of the embodiment shown in Figure 8; Figure 10 is a partially broken away and sectioned detail of one of the auxiliary pendulum non- rigid support members shown in Figures 8 and 9; and Figure 11 is a partially broken away and sectioned partial view of another embodiment wherein a reference orientation for the stabilized portion of the system is established by a non-rigidly coupled auxiliary pendulum acting in combination with a single coil spring mounted on the support structure. Description of the Preferred Embodiments Referring first to Figure 1, it can be seen that platform structure 10 of equipment platform 13 supports operating equipment 11 such as a directional microwave antenna or radar apparatus. The equipment platform is defined herein as including all operating equipment mounted thereon. Operating equipment 11 is rotatably mounted on platfora structure 10 and typic¬ ally is slaved to follow the ship's gyro compass. Platform structure 10 itself is supported by the upper gimbal ring 19, which is pivotally mounted on the upper spider spindles 22 and 23- Referring now to Figure 2, upper spider 20 is pivotally mounted on upper support spindles 15 and 16, which are supported by upper trunnions 17 and 18, which in turn are attached to the support structure 12. The axes of OM spindles 22 and 23 are shown to be co-linear and per¬ pendicular to the co-linear axes of spindles 15 and 16. Both of these co-linear axes lie in the same plane. Gimbal brackets 24 and 25 attached to upper gimbal ring 19 support pivotally-mounted upper ball joints 26 and 27 with their pivotal centers lying respectively on spindle axes 22 and 23, and 15 and 16. Push-rods 28 and 29 are attached respectively to ball joints 26 and 27 at one end, and as shown in Figure 3, to lower ball joints 48 and 49 at their other end. Gimbal clips 50 and 51 support lower ball joints 48 and 49 and are themselves attached to lower gimbal ring 42 which is supported on lower spider spindles 56 and 57. Lower spider 43 supports spindles 56 and 57 and itself is pivotally supported by lower support spindles 44 and 45 which are supported by lower trunnions 46 and 47. The pivotal axis repre¬ sented by spindles 56 and 57 is perpendicular to the pivotal axis represented by spindles 44 and 45. Both of these axes lie in the same plane. Lower trunnions 46 and 47 are mounted at another place on support structure 12 from that which supports upper trunnions 17 and 18. The axes represented by lower support spindles 44 and 45, and 56 and 57, are parallel respectively to the axes represented by upper support spindles 15 and 16, and 22 and 23. Azimuth bearings 40 and 41 are supported by lower gimbal ring 42 and themselves rotationally support gyro azimuth frame 39 on which are mounted gyro mounting frames 34 and 38. Gyro motor 30 and rotor 31 are pivotally supported on gyro pivot spindles 32 in gyro mounting frame 34. Gyro motor 35 and rotor 36 are pivotally supported on O PI pivot spindles 37 in the gyro mounting frame 38. The pivot axis of gyro motor 30 is perpendicular to the pivotal axis of gyro motor 35. Although pivot spindles 32 are shown parallel to pivot spindles 56 5 and 57, these axes need not necessarily be so oriented. Gyro motor with rotor 31 is statically balanced about pivot spindles 32; gyro motor 35 with rotor 36 is also statically balanced about pivot spindles 37. 10 Gyro spring 59 is connected to eccentric extension 33 of spindle 32 at one end, and to spring clip 58 at its other end. Spring 60 is similarly connected between spindle 37 eccentric extension 55 and spring clip 61. Stabilized platform assembly 13 15 is statically balanced about the axis of spindles 15 and 16 and also about the axis of spindles 22 and 23. Stabilizing assembly 14 including push-rods 28 and 29 and ball joints 26, 48, 27, and 49, is statically balanced about the axis of spindles 44 and 2045 and also about the axis of spindles 56 and 57. Gimbal springs 52 and 53 are connected between lower gimbal ring 42 and pendulum 62 so as to orient lower gimbal ring 42 with respect to gravity about the axis of spindles 44 and 45. Two other springs, not shown, 25 are similarly connected to a second pendulum, not shown, to orient gimbal ring 42 about the axis of spindles 56 and 57 with respect to gravity. In an unillustrated variation of the embodi¬ ment shown in Figure 1, gimbal springs 52 and 53 are 30 attached to trunnion 46 rather than to pendulum 62, and pendulum 62 is eliminated from the system. In Figure 4, an embodiment of this invention is shown in which a single-axis stabilized platform is employed. Pivot axis spindles 15' are rotationally supported in trunnions 17' mounted on support struc¬ ture 12'. Gyro motor 35' is statically balanced with respect to its support spindles 22' and 23' which are rotationally mounted in lower gimbal ring 42' . Ring 542' is supported on spindles 44' and 45' which in turn are supported in lower trunnions 46* and 47' as shown in Figure 5. Gyro pivot spring 60' is connected to eccentric extension 33' of spindle 23* at one end and at its other end to spring clip 58' which is attached to lower gimbal ring 42*. Gimbal springs 52' and 53' are connected between eccentric extension 21' of spindle 45' and tabs on pendulum 62*. The stabilized platform assembly 13* and the stabilizing assembly 14' including push-rod 28' and ball joints 26' and 48' are statically balanced about their respective support spindles 15* and 44' and 45', either individually or compositely. In Figures 6 and 7, trunnions 46" and 47" carry gimbal spindles 63" which pivotally support inner gimbal 73 which in turn pivotally supports outer gimbal ring 72 on spindles 75. Pendulum ring 69 is rigidly connected to outer gimbal ring 72 by means of struts 68. This overall arrangement provides pendulum ring 69 with pivotal freedom about two mutually per- pendicular axes. Coil spring 70 rests in a groove in the upper surface of outer gimbal ring 72 at its lower end, and in a grooved ring 71 which is attached to lower gimbal ring 42" at its upper end. Excluding pendulum ring 69 with struts 68 and coil spring 70, stabilization assembly 14" is statically balanced about both orthogonal axes of spider 43". Thus the composite assembly comprised of stabilization assembly 14" and the stabilized platform assembly 13", not OMP shown, including push-rods 28" and 29", is non-rigidly oriented with respect to gravity in two dimensions by pendulum ring 69 as a result of the coupling provided by coil spring 70. In Figure 8 an embodiment of this invention is shown wherein the stabilized system is constructed as one integrated assembly. In the Figure post 77 mounted on support structure 12" carries a universal joint consisting of lower yoke 80, upper yoke 32, and hidden internal cross 81. Yokes 80 and 82 pivot on the right-angled spindles of cross 81 so as to com¬ prise a gimbal assembly. The upper extension of yoke 82 constitutes a stable platform on which operating equipment 11'" is mounted. The upper extension of yoke 82 also supports azimuth bearings 40'" and 41'" which in turn rota¬ tionally support gyro frame 39"*. The entire assem¬ bly comprised of upper yoke 82, operating equipment 11'", and gyro frame 39'" including all components attached thereto, is statically balanced about the two orthogonal axes of internal cross 81. Gyro frame 39'" is provided with two gyro assemblies comparable to those shown in Figures 1 and 6. Cable clips 67, attached at diametrically opposite positions on upper yoke 82, rigidly support pendulum cables 66 at their upper ends. At their lower ends pendulum cables 66 are pivotally connected to clips on pendulum ring 69* in the plane of Figure 8, but are rigidly connected to pendulum ring 69' in the plane shown in Figure 9. Thus the steady-state, or average, orientation of pendulum ring 69" is imparted symmetrically and with equal coupling stiffness in two orthogonal planes to upper yoke 82. P Referring now to Figure 10, pendulum cable 66 is shown to be comprised of an inner flexible core 64, such as a multi-strand steel cable, and an outer cover consisting of a closely wound coil spring case 65. The annular space between core 64 and case 65 is filled with a viscous medium, such as a petroleum grease. Relative motion between core 64 and case 65 which occurs whenever pendulum cable 66 flexes creates shearing displacements throughout the viscous medium which thereby absorb a portion of the energy causing cable flexure in the first place. In Figure 11 an embodiment of this invention is shown wherein the reference orienting effect of pendulum ring 469 is complimented and modified by the reference orienting effect of coil spring 470. Grooved ring 483, which is rigidly attached to support post 477, supports coil spring 470 at its lower end while the upper end of coil spring 470 rests in a groove in ring 471 which itself is attached to upper yoke 482. Coil spring 470 may be constructed so as to possess pre-selected non-linear stiffness-versus- deflection characteristics. The advantages of such construction are discussed below. Description of Operation In operation, gyro motors 30 and 35 drive their respective rotors 31 and 36 in opposite direc¬ tions at some nominal design speed, typically in the range of 600 to 6,000 rpm. The two motors need not operate at the same speed. In the absence of any dis- turbance the system will find and maintain the orien¬ tations indicated in Figure 1. Note however that gyro azimuth frame 39 is essentially unrestrained in azi¬ muth and hence is free to take any azimuth orienta- O PI tion. For the sake of illustration that gyro frame 39 initially is in the position shown in Figures 1 and 3. Now suppose structure 12 oscillates about an axis parallel to the axis of trunnion 15 as would be caused by a ship's rolling motion. Lower gimbal ring 42 and upper gimbal ring 19 will tend to remain in their original orientations as a consequence of their mass moment of inertia. Any accelerations which accompany the oscillations of support structure 12 or any other extraneous accelerations which may occur will have no effect on the statically balanced por¬ tions of the system, which is the entire system except for the reference orienting pendulum, because they are compositely statically balanced about all motion axes. However, varying torques tending to disturb lower gimbal ring 42 orientation will be induced by springs 52 and 53 whenever pendulum 62 has been deflected by horizontal accelerations. These disturbing torques, acting over finite periods of time, become torsional impulses which tend to re-orient lower gimbal ring 42 about spindles 45 and 46. Such re-orientation is resisted, however, by the process of gyro precession; gyro motor with rotor 31 absorbs the imposed torsional impulses by undergoing angular momentum changes, spec- ifically by changing its spin axis orientation about spindle 32. The speed of motor 30 with rotor 31 is essentially unaffected. Gyro motor 30 will be gently urged back toward its initial center position during and after any precession motion by spring 33 acting on eccentric extension 33 of spindle 32. When oscillations of support structure 12 occur in the orthogonal direction to that described above, comparable to a ship's pitching motion, the same effects will occur but the disturbing torques OMPI will be induced by the orthogonal counterparts to springs 52 and 53 and pendulum 62, and the resisting torques will be generated by gyro motor 35 with rotor 36 by its precessing about pivot spindles 37. Motion of support structure 12 simultaneously in both direc¬ tions, corresponding to a ship experiencing both roll and pitch motions, will result in the simultaneous occurence of both of the consequential effects described above. When support structure 12 rotates about a vertical axis, comparable to a ship's turning motion in azimuth, gyro azimuth frame 39 will tend to remain static in its initial position as a consequence of its mass moment of inertia. If support structure 12 now rolls as this new azimuth position any disturbing torsional impulses induced by springs 52 and 53 from penduliim 62 will be resisted by precession motions of both gyro motor with rotor 31 and gyro motor 35 with rotor 36 as each assembly reacts to its components of the disturbing torsional impulses. If operating equipment 11 is rotated in azi¬ muth on platform structure 10 no disturbing torques will be induced in the system because any torques accompanying such motion will be reacted by spindles 22 and 23, and thence to spindles 15 and 16, to trunnions 17 and 18. If the system's annular momentum change capacity is exceeded, such as can occur if support structure 12 rotates beyond the platform's angular operating range, one or both of the gyro motors 30 and 35 will rapidly drive itself to a precession angular motion limit position and the system will thereupon become completely unstable. The system will immedi¬ ately begin to erect itself however, and within one or two minutes after the operating angular motion limit was last exceeded the system will become essentially stable again. This graceful re-stabilization charac¬ teristic of the present invention is markedly differ- ent from the re—stabilization behavior of rigidly pendulous mechanically stabilized systems which, after once having been tumbled will continue to be destabil¬ ized until, by fortuitous circumstances, the angular motion limits and the integrated disturbing impulse correcting capacity of the gyros are not exceeded over one complete oscillating cycle of the ship. The aforesaid fortuitous circumstances typically will occur- for rigidly pendulous systems within ten to one hundred oscillating cycles of support structure 12, depending on how closely the total motion amplitude of support structure 12 approaches the useful operating range of the stabilized platform system. The embodiment shown in Figure 4 does not have immunity to azimuth motions of the support struc- ture as is provided by the embodiment shown in Fig¬ ure 1. This embodiment is therefore most useful in those applications which have negligibly small motions about one axis, e.g. pitch, and which also experience only slow yaw/turning rates. This situation exists for very large crude oil carrying ships. In the embodiment illustrated in Figures 1, 4, 6, and 8 it will be noted that horizontal accelera¬ tions caused by ship rolling and pitching motions, and which cause the reference orienting pendulum 62, 62', 69 or 69* respectively to be non-vertical, will tend to mis-orient the stabilized portions of the system in a direction which is opposite to the motion itself. For example, in a rolling motion of a ship to the right from vertical the pendulum will tend to create an error toward the left in stabilized platform orien¬ tation. It will be noted further that coil spring 470 in Figure 11 will tend to mis-orient the stabilized platform in the same direction as ship motion; in a rolling motion to the right from vertical the coil spring will tend to create an error also to the right in stabilized platform orientation. These opposite effects are combined in the embodiment shown in Figure 11 to minimize the mid-orienting effects of either the pendulum, or the spring-to-support post reference orienting means taken by itself. It also will be noted that horizontal accel¬ erations acting on the auxiliary pendulum 469 in Figure 11 can be represented by trigonometric expres- sions, as proposed in U.S. Patent 1,083,370 - Luyken, for example. Further, approximations to such trigono¬ metric expressions, but of the opposte sense, can be obtained for the force versus deflection relationship of coil spring 470 by winding it, for example, to have both taper and non-uniform coil spacing. Thus, the embodiment shown in Figure 11 allows significant reductions in the error causing effects of the refer¬ ence orienting pendulum under operating conditions involving appreciable ship motions having attendant appreciable horizontal accelerations. Although the embodiments of this invention shown in the Figures and described herein indicate the use of one or two gyros with their spin axes oriented to be nominally vertical, it should be understood that other gyro arrangements are equally applicable. Among such permissible alternative arrangements is a four- gyro array generally in a form as described in U.S. Patent 1,236,993 - Sperry or 1,083,370 - Luyken, the horizontal spin axis arrangements described in U.S. Patent 1,645,079 - Titterington or 1,573,028 - Bates and the over/under arrangement suggested in U.S. Patent 1,324,477 - Tanner. Also, an end-to-end arrangement generally as described in U.S. Patent 3,742,770 - Flannelly can be substituted for the gyro arrangements depicted above. All such alternative arrangements would, of course, in accordance with my invention, be statically balanced and non-rigidly coupled to an auxiliary reference orienting pendulum as described above. So, it should be understood that although the word "invention" has been used in a singular sense, it may include a number of separate and dis¬ tinct features. These features may be practiced in various combinations, as exemplified by the disclosed embodiments, but it should be appreciated that each may also be practiced independently of the others. For example, a stabilized platform system according to this invention may include a statically balanced, integral-type unit in which the gyro azimuth frame 39 is rigidly attached to lower gimbal ring 42 rather than mounted on its own azimuth bearings 40 and 41. Also, a rigidly pendulous stabilized system as pres¬ ently known in the art may be modified according to this invention to include free—azimuth mounting of the gyro support frame. Finally, the embodiments shown in the fig¬ ures are intended to be representative and not inclu¬ sive. For example, the addition of damping means, caging means, or power transmission means such as slip rings or rotary air gap transformer would not change the basic character of this invention. Accordingly, while only five specific embodiments of this invention have been illustrated and described, it is understood that various modifications and changes will become obvious to those skilled in the art. Such modifica¬ tions and changes may be made without departing from the true scope and spirit of this invention. -^UREA O PI

Claims: WHAT IS CLAIMED IS: 1. In combination, a gyroscopic torsional impulse absorption system, pivotal supporting means, a pendulum, and non-rigid coupling means operatively connected between said pendulum and said gyroscopic torsional impulse absorption system. 2. The system of Claim 1 wherein said non- rigid coupling means includes a spring. 3. The system of Claim 2 wherein said pen- dulum includes elastic suspension means. 4. The system of Claim 1 wherein said pen¬ dulum is elastically suspended from said gyroscopic torsional impulse absorption system. 5. The system of Claim 1 wherein said non- rigid coupling means includes energy absorbing means. 6. The system of Claim 1 wherein non-rigid coupling means are discontinuously operatively con¬ nected between said pendulum and said gyroscopic torsional impulse absorption system. 7. In combination, a gyroscopic torsional impulse absorption system, supporting means, and a platform, said gyroscopic torsional impulse absorption system mounted on a pivotal axis on said supporting means and including rotatable means whereby rotational motion in inertial space of said supporting means about an axis at right angles to said pivotal axis is isolated from said gyroscopic torsional impulse absorption system with respect to inertial space about said axis, said rotatable means being independent of said platform, and said platform is pivotally mounted on said supporting means and oriented with respect to said gyroscopic torsional impulse absorption -system by connection means therebetween. 8. In combination, a gyroscopic torsional impulse absorption system, supporting means, a plat¬ form, and a pendulum, said gyroscopic torsional impulse absorption system mounted on a pivotal axis on said supporting means and including rotatable means whereby rotational motion in inertial space of said supporting means about an axis at right angles to said pivotal axis is isolated from said gyroscopic tor¬ sional impulse absorption system with respect to iner¬ tial space about said axis, said rotatable means being independent of said platform, said platform being pivotally mounted on said supporting means and oriented with respect to said gyroscopic torsional impulse absorption system by connection means there¬ between, and non-rigid coupling means operatively con- nected between said pendulum and the gyroscopic tor¬ sional impulse absorption system. 9. A mechanically stabilized platform system for mounting on a supporting structure comprising: an equipment platform pivotally mounted about a second pair of orthogonal intersecting axes, each of said second pair of axes being parallel to and spaced apart from a corresponding member of said first pair of axes; a stabilizing assembly pivotally mounted about a first pair of orthogonal intersecting axes, said assembly including a gimbal ring, a gyro azimuth frame rotatably mounted on said gimbal ring for rota¬ tion in a plane parallel to said intersecting axes, a pair of gyro assemblies pivotally mounted about a corresponding pair of perpendicular precession axes, " 5 each of said gyro assemblies including means for orienting said gyro assemblies with respect to said gyro assemblies with respect to said azimuth frame; a pendulum suspendable from said supporting structure; 0 means interconnecting said equipment plat¬ form and said stabilizing assembly for maintaining a predetermined relative angular orientation therebe¬ tween; means for compositely statically balancing 5 said stabilizing assembly and said equipment platform about their pivotal axes; and means for orienting said stabilizing assembly including non-rigid coupling means extending between said stabilizing assembly and said pendulum. 0 10. The system of Claim 9 wherein said non- rigid coupling means includes a spring. 11. The system of Claim 9 wherein said pendulum includes elastic suspension means. 12. The system of Claim 9 wherein said 5 pendulum is elastically suspended from said stabil¬ izing assembly. 13. The system of Claim 9 wherein said non- rigid coupling means includes energy absorbing means. 14. The system of Claim 9 wherein non-rigid coupling means are discontinuously operatively con¬ nected between said pendulum and said stabilizing assembly. 15. The system of Claim 8 wherein said non- rigid coupling means includes a spring. 16. The system of Claim 8 wherein said pendulum includes elastic suspension means. 17. The system of Claim 8 wherein said pen- dulum is elastically suspended from said gyroscopic torsional impulse absorption system. 18. The system of Claim 8 wherein said non- rigid coupling means includes energy absorbing means. 19. The system of Claim 8 wherein non-rigid coupling means are discontinuously operatively con¬ nected between said pendulum and said gyroscopic torsional impulse absorption system. 20. A mechanically stabilized platform sys¬ tem adapted to be mounted on a supporting structure comprising: a stabilizing assembly pivotally mounted about a first pair of orthogonal intersecting axes, said assembly including a gimbal ring, a gyro azimuth frame rotatably mounted on said gimbal ring for rota- tion in a plane parallel to said intersecting axes, a pair of gyro assemblies pivotally mounted about a corresponding pair of perpendicular precession axes, each of said gyro assemblies including means for orienting said gyro assemblies with respect to said azimuth frame; an equipment platform mounted about a second pair of orthogonal intersecting axes, each of said second pair of axes being parallel to and spaced apart from a corresponding member of said first pair of axes; means interconnecting said equipment plat¬ form and said stabilizing assembly for maintaining a predetermined relative angular orientation there¬ between; means for compositely statically balancing said mechanically stabilized platform system about its support axes; and means for orienting said stabilizing assembly including spring means extending between said platform assembly and the supporting structure. 21. The system of Claim 20 including spring means extending between said stabilizing assembly and the supporting structure for orienting said stabili¬ zing assembly. 22. In combination, a gyroscopic torsional impulse absorption system, pivotal supporting means, a pendulum, non-rigid coupling means operatively con- nected between said pendulum and said gyroscopic tor¬ sional impulse absorption system, and resilient means operatively connected between said gyroscopic tor¬ sional impulse absorption system and the supporting means. 23. The system of Claim 1 including means for compositely statically balancing said gyroscopic torsional impulse absorption system about said pivotal supporting means. 24. The system of Claim 1 wherein said pen¬ dulum, in combination with said non-rigid coupling means, includes means whereby the natural period of oscillation of said combination falls in the range of 0.25 to 4.0 seconds.

Inventors: MATTHEWS ROBERT J
Applicants: MATTHEWS ROBERT J
Application year: 1982
Main classification: F16M13
IPC codes: F16M11, F16M13, G01C19, G12B5