MIL_G_81168.pdf

MIL-G-81168 ( WP )

9 October 1964

MILITARY SPECIHCATION

GYROSCOPE, RATE INTEERATING

This s p e c i f i c a t i o n has been approved by t h e Bureau of Naval Weapons, Department of t h e Navy

1. SCOPE

1.1 This specification covers the general requirements for rate integrating gyroscopes for use in inertial navigation, shipboard and airborne fire conkrol system.

2. APPLICABUWcUbrlENTs

2.1 The following specifications, standards and drawings of the issue in effect on date of invitation for bids shall form a part of this specification to the extent specified herein.

SPECIFICATIONS

FEDERAL

QQ-C-320 Chromium Plating (Electrodeposited) a - N - 2 9 0 Nickel Plating (Electrodeposited) m-P-416 Cadmium Plating (Electrodeposited) PPP-B-621 Boxes, Wood, Nailed and Lock-corner

MILITARY

MIL-A-8625 Anodic Coatings, for Aluminum and Aluminum Alloys MIL-C-5541 Chemical Films for Aluniinun and Aluminum Alloys MIL-1-16910 Interference Measurement, Methods and Limits MIE-M-317lA Magnesium Alloy, Corrosion Protection MIE-M-45202 Magnesium Alloy, Anodic Treatment of M I L - P - ~ ~ ~ Preservation, Methods of MIL-Q-9858 Quality Control System Requirement

FSC 6615

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Licensed by Information Handling ServicesLicensed by Information Handling Services

MIL-O- 81168 (WP)

MIL-S-6872

MïL-W-16878/4 Wire, Electrical, Type E, 200.C

Soldering Processes, General Specifications for

STANDARDS

MILITARY

MIL-S!lD-l29 Marking of Shipments

MIL-STD-143

MIL-STD-202

MS-33586 Metals, Definition of Dissimilar

Specifications and Standards, Order of Test Methods for Electronic and Electrical Component P a r t s

DRAWINGS

(Copies of specifications, standards, and drawings required by contractors in connection with specific procurement functions shall be obtained from the procuring activity. )

2.2 Other publications. The following documents form a part of Unless othelwise indicated, the issue in effect this specification.

on date of invitation for bids shall apply.

NATIONAL BuREAIf OF STAMIARDC

Handbook H-28 Screw-Thread Standards for Federal Services

(Applications for copies should be addressed to the Superintendent of Documents, Government Printing Office, Washington 25, D. C.)

CONSOLIDATED CLASSIFICATION CCMMITPEE

Consolidated Freight Classification Rules

(Application for copies should be addressed to the Consolidated Classification Conanittee, 202 Chicago Union Station, Chicago 6, Illinois. )

3. R G Q u I m s

3.1 Detail specifications for individual gyro types. All

requirements specified herein are applicable to all, types of integrating gyros covered by military specifications. Detail requirements or c exceptions applicable to individual types will be specified in the detail gyro specifications. In the event of any conflict between

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requirements of t h i s specification and requirements of the de ta l l gyro specification, the l a t t e r shal l govern.

3.2 Definitions and Conventions.

3.2.1 Rate integrating gyro.

degree of freedom gyro having primarily viscous res t ra in t of i t s spin axis about the output axis.

produced by gimbal angular displacement, re la t ive t o the case, which is proportional t o the integraJ. of the angular r a t e of the case about the input axis.

scope for t h i s specification.

A rate integrating gyro is a single

In t h i s gyro an output signal i s

The t e m gyro i s synonymous with gyro-

3.2.2 Rotor moment of inertia. Rotor moment of iner t ia i s the moment of i ne r t i a of a gyro m t o r about its spin axis.

3.2.3 Spin axis (SA).

3.2.4 Spin reference axis (SRA). The spin reference axis is

the nominal direction of the spin axis, indicated by external case marking, when the gyro output has specified values; usually nuU.

The spin axis is the axis of rotation of the rotor.

3.2.5 Degree of freedom. A degree of freedom is an allowable

mde of angular motion of the spin axis with respect t o the case.

The number of degrees of freedom is the number of orthogonal aces about which the spin axis i s free t o rotate.

3.2.6 Axis of freedom. A n axis of freedom i s an axis about

which a gimbal provides a degree of freedom.

3.2.7 Gimbal.

3.2.8 Input axis ( I A ) . An input axis is an axis about which

A gimbal i s a support which provides the spin axis with a degree of freedom.

a rotation of the case causes a maximum output.

the spin axis.

It is no,mal -i%

3.2.9 Input reference axis. A n input reference axis i s the

nominal direction of an input axis as indicated by external case markings. It i s nominally normal to the spin reference axig.

3.2.10 Output axis (OA).

providedwith a pickoff which generates an output signal as a function of the output angle.

An output axis is an axis of freedom

. . Licensed by Information Handling ServicesLicensed by Information Handling Services

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3.2.i l Precession. Precession is a rotation of the spin axis produced by a torque, T, applied about an exis mutually perpendicular t0 the spin axis and the axis of the resulting rotation.

precession rate, W, is related to rotor angular momentum, H, and applied torque, I, by the equation Wñ = T.

3.2.12 Coimnand rate. conmiand mte is the input rate equivalent to a precession rate caused by a torquer conmrand signai.

3.2,13 Capturing.

one or more gyro axes or glmbal axes to a specified reference pasition.

3.2.14 Slewing.

an axis parallel to that of the applied torque causing the rotation.

3.2.15 Earth's rate correction, M h f s rate correction i s a csnrmand rate applied to a gyro ia compensate for the drift rate of t h e gym spin axis with respect t o i ts case caused by the rotation of the earth.

A constant

Capturing is the use of a torquer t o restrain

Slewing i 6 the rotation of the spin axis about

52.16 Pickoff* A pickoff is a device which produces a signal

output, generally a voltage as a f'unction of the relat ive angular displacement of two elements. This angular displacement is usualiy between 'ho gimbals o r between a gimbal and the case.

3.2017 Torquer. A torquer i s a device which exerts torque on a gimbal i n response to 8n input signal.

3.2*18 cross coupling errors. cross coupling errors are errors i n the gym output resulting from gyro sensit ivity to inputs about axes normal to an input reference axis.

3.2.19 Electrical zero. Electrical zero is the angular reference position of a pickoff where, with a certain excitation applied to the pickoff, i ts ín-phase fundamental output w i l l be zero.

flowing in bra windings of a microsynr (i.e., 11 12 COS Ø = MA ).

3.2.20 Current product (MA2). The in-phase product of the gurrent

Where Il = Reference w i a n g current

12 = Control winding current fi = Phase angle of 11 to I2

Positive current product is the product of reference and control winding currents of the same sign and produces positive torque.

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3.2.21 Scale factor. Scale factor is the ra t io of a change

in output t o a change i n the input intended t o be measured.

factor is generally evaluated as the slope of a straight l ine t h a t can be f i t t e d by the method of least squares t o input - outpial;

data obtained by varying the input cyclically over the input range.

Scale factors of interest for the gyros include; torquer scale factor (dyne-cm per milliamp) , pickoff scale factor (volts per deg~ee output angle), comand rate scale factor (degrees per hour per milliamp), and gyro scale factor (volta per degree input angle).

Scale

3.2.22 Output range. Output range is the product of input range and scale factor.

3.2.23 Input limits. Input limits are t h e extreme values of the input, generally plus and minus, within which performance is of the specified quality. Input limits are generally expressed either as angular displacements o r angular rate, or both.

3.2.24 Input range. Input range is the absolute value of the

difference between the input limits.

3.2.25 Linearity error. Linearity error is a measure of the

greatest variation of the input output data from the l e a s t squares straight line.

squares straight l ine expressed as a percent of one-half the output ran@e

3.2.26 Hysteresis. Hysteresis is the difference between output signals for increasing and decreasing inputs at tha t input f o r which the dlfference is maximum, measured after cycling through the input m e

It is the maximum output deviation from the least

3.2.27 Composite error. Composite error is the maximum deviation of the output data frm the specified output function.

error is due t o the composite effects of hysteresis, resolution, non-linearity, repeatability, and other uncertainties i n the output data.

Composite

It is expressed as a percentage of one-half the output range.

3.2.28 Error band. Error band is a band about the specified

The error band output function which contains the output data.

contains the composite effects of hysteresis, resolution, non-lineayity, repeatability and other uncertainties i n the output data.

3.2.29 Drif t rate. D r i f t rate I s the time rate of angular deviation of the spin axis from the desired orientation i n space.

It consists of random and systematic dr i f t ra te components. It i s expressed as an equivalent input angular rate i n degrees per unit time.

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3.2.30 Acceleration insensitive drift rate. Acceleration insen-sitive drift rate consists of those components of systematic drift rate that have no correlation with acceleration. It is ascribable to such effects as temperature gradients and reaction torques.

It is expressed in degrees per unit time.

drift rate consists of those components of systematic drift rate that are correlated with translational acceleration applied to the gyro case. The relationship of these components of drift rate to acceleration can be statedby means of coefficients having units such as degrees per unit time per ''g" (e.g. mass unbalance) and degrees per unit time per "g" squared (e.g. drift caused by aniso-elasticity).

rate to the product of the components of the instantaneous value of the acceleration resolved along the principle axes of the gyro.

3.2.31 Acceleration sensitive drift rate. Acceleration sensitive

The acceleration 'squared coefficient relates the drift

3.2.32 Masa unbalance. Mass unbalance is the characteristic

. of the gyro resulting from lack of coincidence of the center of suspension and the center of mass. It gives rise to torques caused by translational accelerations which lead to acceleration sensitive drift rates .

3.2.33 Anisoelasticity. Anisoelasticity is the inequality of

compliance of the rotor and gimbal assembly in different directions.

When the gyro is subjected to undirectionai. or vibratory accelerations at an angle to a principal axis of compliance anisoelasticity leads to torques proportional to the squwe of the applied accelerations.

This torque results in acceleration sensitive drift rate proportional to acceleration squared.

. 3.2.34 Reaction torques. Reaction torques are torques exerted '.=-on a gimbal as a result of electrical excitations applied to the

. ~ s u l t s in an acceleration insensitive &iffi rate.

'output to a change in an undesirable or secondary input, For 'example, the drift rate temperature sensitivity of a gyro is the

:'ratio of the change in drift rate to a change in temperature.

I- 52.36 Viscous restraint. The viscous restraint coefficient (C) refers to the viscous restraint of the flotation fluid in dyne-cm/ radian/second.

.for necessary comanodities and services not specified herein shall be selected in accordance with MIL-STD-143 except as provided in .3.3,1 and 3.3.2.

gyro exclusive of torquer command signals. This torque usually

3.2.35 Sensitivity. Sensitivity is the ratio of a change in

3.3 Selection of government documents. Specification and standards

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3.3.1 Commercial parts. Comercial parts having suitable

properties may be used where, on the date of invitation for bids, there are no suitable standard parts. In any case, commercial u t i l i t y parts, l i k e screws, bolts, nuts, cotter pins, having suitable properties may be used provided:

' Y ( a ) They can be replaced by the standard par t s (MS or

A N ) without alteration.

( b ) The corresponding standard part numbers are referenced i n the parts list and, i f practical, on the contractor's drawings.

3.3.2 Standard parts. With the exception of 3.3.1, M S and AN standard par ts s h a l l be used where they su i t the purpose.

sha l l be identified on the drawings by t h e i r part numbers.

They

3.4 Parts , materials, processes and workmanship. Materials

shall conform to applicable specifications and s h a l l be as specified herein. Materials for which there are no applicable specifications, o r which are not specifically described herein, sha l l be of the best quality, of the l igh tes t practicable weight, and suitable for the purpose intended. A detailed description of the materials, design and manufacturing processes must be submitted as part of the quality assurance procedure i n compliance w i t h MIL-Q-9858.

3.4.1 Cri t ical materials. Non-critical materials shall. be used where practicable.

essential t o meet specification requirements, the material used s h a l l be the leas t c r i t i c a l of those which are adequate for the purpose.

Where the use of a c r i t i c a l material i s

3.4.2 Metals. Metals s h a l l be of the- corrosion-resistant type, o r sha l l be suitably protected as specified herein to r e s i s t corrosion due t o salt spray or atmospheric conditions to which the gyroscope may be subjected when i n storage or during normal service life.

corrosion dissimilar metals, as defined i n MS-33% shall not be used i n intimate contact w i t i each other.

Unless suitably protected against electrolytic

3.4.3 Nonmagnetic materials. Nonmagnetic materials sha l l be used for all parts of the gyroscope except where magnetic matero i d s are essential.

3.4.4 Fungus-proof materials. Materials which are nutrients

for fungi sha l l not be used where it is practicable to avoid them.

Where used and not hermetically sealed, they shall be treated w i t h a fungicidal agent acceptable t o the procuring activity.

However, if they w i l l be used i n a hermetically sealed enclosure, fungicidal treatment w i l l not be necessary.

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3.4.5 Corrosive fumes, The materials as installed in the

gyroscope and under the service conditions specified herein, shall not liberate deleterious fumes.

3'4.6 Finish. Protective coatings, potting compounds and finishes which will, crack, chip or scale during normal service life or due to extremes of atmospheric conditions shall not be used.

shall be covered with an anodic film conforming to MIL-A-8625.

Aluminum alloys which do not anodize satlsfact;orijy, shall be coated with a chemical film in accordance with MIL-C-5541.

3.4.8 Magnesium parts. Where practical, magnesium alloy parts shall be plated in accordance with MIL-M-317U or MIL&-45202 and of a class that is adequate to achieve the necessary degree of protection in accordance with 68- N-416, QQ-N-290 or QQ-(2-320, and of a class that is adequate to achieve the degree of protection required,

3.4.7 Aluminum parts. Where practical, aluminum alloy par ts

3.4.9 Steel partB. Where practical, steel parts shall be plated

3.4.10 Soldering, Soldering shall be accomplished in accordance

3*4*13. Workmanship. The gyro, including all parts and accessories, With MIL-s-~~~s.

shall be contructed and finished in a thoroughly workmanlike manner.

Particular attention shall be given to neatness and thoroughness of soldering, brazing, painting, riveting, machine screw assemblies and freedom of parts f r o m burrs and sharp edges.

3*4*12 Cleaning. The gyro shall be thoroughly cleaned and loose spattered or excess solder, flux, metal chips and other foreign material shall be removed.

3.4.13 Wire. Electrical wire used for terminal leads shall conform

3.5 Dielectric strength. Gyroscopes shall display no evidence of to MIL-W-16878/4 (Navy ) insulation breakdown or internal arcing when tested in accordance with 4.13 at the test pointa specified in the detail specification.

3.6 Insulation resistance. Insuìation resistance measurements The resistance shall shall be performed in accordance with 4.14, be at least 100 megohms.

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3.7 Spin motor.

3.7.1 Type.

3.7 . 2 Winding configuration. The spin motor winding configuration

3.7.3 Rated excitation. The spin motor excitation voltage md

3.7.4 T e s t excitation. ?e spin motor test excitation voltage

The spin motor shall be the type specified i n the detai l specification.

shal l be as specified i n the de ta i l specification.

frequency shal l be as specified i n the applicable de ta i l specificattion.

and frequency sha l l be as specified i n the applicable detai l specifi-cation.

3.7.5 Angular velocity. The spin motor angular velocity when

running at synchronous speed sha l l be as specified i n the applicable detail specification.

3.7.6 Rotor angular momentum. Rotor angular momentum, H, i s

the product of spin angular velocity and rotor moment of inertia.

It is a measure of the ab i l i ty of a gyro rotor t o maintain the spin axis fixed i n space.

specified i n the de ta i l specification.

expressed i n gram centimeters squared per second.

for the gyro rotop to reach a specified speed from stand still.

When tested i n accordance w i t h 4.15.1, the run-up time sha l l be within the limits specified i n the applicable detail specificatton.

The angular momentum sha l l be as Angular momentum is

3.7.7 Run-up time. Run-up time i s the time interval required

3.7.8 Parer consumption. When tested i n accordance with

4.15.2, the power consumption of the spin motor shal l not exceed the value specified i n the de ta i l specification.

3.7.9 Starting current. The starting current.shal1 not exceed the value specified i n the de t a i l specification when tested i n accordance w i t h 4.15.3.

3.7.10 Running current. The spin motor " l i n g current sha l l be within the value specified i n the detail specification when tested i n accordance w i t h 4.iSm4.

3.8 Pickoff.

3.8.1 Type. The pickoff shall be the type specified i n the

de ta i l specification.

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3.8.2 Rated excitation, The pickoff excitation shal l be as

3.8.3 Test excitation. The pickoff t e s t excitation sha l l be

3.8'4 Impedance. When tested i n accordance with 4.16, the specified i n the applicable de ta i l specification.

as specified i n the de ta i l specification.

impedance of the pickoff windings shal l be within the limits specified in the de ta i l specification.

null voltage s h a l l not exceed the value specified in the de ta i l speclf ication,

3.8.6 Phase shift . Phase s h i f t is the difference between the time phase of the fundemental component of the primary voltage and the time phase of the secondary voltage of the pickoff with the gimbal at the positive stop. When tested i n accordance with 4.17.2, the value of phase sh i f t shal l be as specified i n the detai l specification, the l inear i ty error of the angle input to voltage output of the pickoff shall be as specified In the de ta i l specification.

3.8.5 Nul l voltage. When tested i n accordance with 4.17.1, the

3.8.7 Linearity error, When tested i n accordance w i t h 4.17,3,

3.9 Torquer.

3.9.1 Type. The torquer shall be the type specified i n the

applicable de ta i l specification.

3.9.2 Reference winding excitation. The maximum reference winding excitation shal l be as specified i n the de ta i l specification.

3.9.3 Control winding excitation. The maximum control winding excitation s h d l b e as specified in the de ta i l specification.

3.9.4 Test excitatisn. The torquer test excitation of the

reference winding s h a l î be as specified i n the detail specification.

3.9'5 Command rate scale factor. The command ra te scale factor Command is the ra t io of output angular velocity to torquer input, rate scale factor I s evaluated as the slope of the least squares straight l ine of input-output data obtained by varying the input cyclically over the input range. When tested in accordance with L18.1, the camnand rate scale factor shal l be as specified i n the detai l specification.

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3.9.6 Linearity error. When tested i n accordance with 4.18.1, the m a x h u m torquer l inear i ty error shal l be as specified i n the detail specification.Wnearity error is defined i n 3.2.25.

309.7 Hysteresis. When tested i n accordance w i t h 4.18.1, the hysteresis shal l not exceed the value specified i n the de ta i l specification. Hysteresis i s defined i n 3.2.26.

3.9.8 Maximum cornand rate. The maximum connnand ra te shal l be

3.9.9 Impedance. When tested i n accordance with 4.16, the impedance as specified i n the de ta i l specification.

of the torquer windings s h a l l be as specified i n the de ta i l specifi-cation.

3.9.10 N u l l voltage. When tested i n accordance with 4.18.2, the nul l voltage shal l not exceed the value specified i n the detai l specification.

3.9.ii Reaction torque. Torquer reaction torque is the unwanted torque produced on a gimbal as a result of e lectr ic current in the reference winding. When tested i n accordance with 4.18.3, the torquer reaction torque shal l not exceed the l i m i t specified in the detail specification.

3.10 Temperature sensor.

3.10.1 me. The temperature sensor s h a l l be of the type specified i n the applicable de ta i l specification .

3.10.2 Scale factor. The temperature scale factor is the change in resistance per degree fahrenheit.

i s positive when the resistance increases with temperature.

scale factor of the temperature sensor shal l be as specified i n the de ta i l specification when tested i n accordance with 4.19.1.

The sign of the scale factor The

3.10.3 Operating temperature resistance. The operating temperatwe resistance shal l be as specified i n t h e de ta i l specification.

See 4.10.3 stabil ized operatlng temperature.

the induced voltage shal l not exceed the value specified i n the' de ta i l specification.

3.10.4 Induced voltage. When tested i n accordance with 4.19.2,

3.10.5 Test excitation. The temperature sensor t e s t excitation shal l be as specified i n the de ta i l specification.

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3.10.6 Operating temperature. The operating temperature is

t h a t temperature at which the temperature sensing element sha l l s tabi l ize at the nominal value of operating temperature resistance specified i n 3.10.30 When tested i n accordance with 4.19.3, the operating temperature shal l be within the limits specified i n the de ta i l specification.

3.10.7 Over temperature sensor. The over temperature sensor

s h a l l be as specified i n t h e de ta i l specification.

3.11 Heaters.

3 J l . l Power. When tested i n accordance with 4.20, .the power consumed by the heaters at specified operating voltage sha l l be within the limits specified i n the applicable de ta i l specification.

3.11.2 Test excitation. The standby heater shal l be excited

with the type of parer specified i n the detail specification.

The gyro shal l be maintained a t operating temperature by main-taining the temperature sensing winding a t operating temperature resistance as specified i n 3010.3. The temperature sensing winding is connected to a temperature control devlce which regulates the gyro temperature by controlling the parer to the standby heater.

is the r a t io of resultant pickoff secondary voltage (Eo) t o a gyro input axis displacement (Ø); When tested i n accordance with 4.21, the gyro scale factor sha l l be as specified i n the de ta i l specifi-cation.

3.12 Gyro scale factor. The gyro scale factor (Eo/Øi)

3.13 Input angular freedom. The input angular freedom is the

munt of input axis angular rotation required to precess the gimbal against its mechanical stop.

f o r positive and negative input angles. When tested i n accordance with ht22 the input angular freedom shal l be as specified i n the detai l specification.

Input angular freedom is measured

3.14 Gyro phasing. Gyro axes and positive rotation are defined i n Figure 1.

positive rotation about the input axis produces positive rotation of the gimbal about the output axis.

torquer also causes a positive output about the output axis. When tested in accordance with 4.23, the e='ro phasing sha l l be 8s specified i n Figure lwhen the spin motor, pickoff and torquer are excited and phased as specified i n the de ta i l specification.

Fbr positive wheel rotation about the spin axis, a

Positive torque f r o m the

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Input Axis

Figure 1 GYRO PHASRG DIAGRAM

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3.15 Null repeatability, The nul l repeatability test gives an indlcation of f r ic t ion and constancy of reaction torques. When tested i n accordance with 4.24, the nul l repeatability shal l not exceed the value specified i n the de ta i l specification.

3.16 Characteristic time. Characteristic time i s the time re-quired for the output .t;o reach 63 per cent of its f i n a l value f o r a step input, When tested i n accordance with 4.25, the characteristic time shall not exceed the value as specified i n the detai l specifi-catione

%17 Axis aligment, The input axis misalignment about the output axis and the spin reference axis shal l not exceed the value specified i n the detai l specification when tested i n accordance With

3,18 Acceleration insensitive d r i f t rate. When tested in accordance wi th the method specified i n the de ta i l specification the acceleration insensitive drift ra te shall conform to the requirements i n the de ta i l specification. D r i f t rate test methods are described i n 4.27 through 4.30 of t h i s document.

3 b 19 Acceleration sensitive drift rate.

3.19.1 Mass unbalance. When tested i n accordance wi th the method specified i n t h e detai l specification, drift ra te correlated to the first power of l inear acceleration shal l not exceed the value specified i n the detai l specification. Mass unbalance t e s t methods are described i n kb27 through 4.29 of t h i s document.

519.2 Anisoelasticity. When tested i n accordance w i t h the method specified i n the de ta i l specification, drift rate correlated to the second pater of l inear acceleration shal l not exceed the value specified i n the de ta i l specification. T e s t methods f o r measuring anisoelasticity are described i n 4.29 and 4,31 of this document.

3.20 Random drift rate. Random drif t rate is the time varying component of drift ra te under specified operating conditions. It is expressed i n degrees per uni t time. When tested i n accordance with the method specified i n the de ta i l specification, the random drift ra te shal l not exceed the value specified i n the applicable detai l specification.

described in 4,29 and 4 . 3 of this document.

Test methoda f o r measuring random d r i f t are

3.21 Elastic res t ra int coefficient. Elastic rest raint coefficient is the ra t io of gimbal restrainiag torque about the output axis to output angle expressed i n degrees per hour per degree. When tested i n accordance with 4.32, the elastic r e s t r d n t coefficient shall not exceed the value specified i n the de ta i l specification.

3.22 Day t o day s tabi l i ty . The change of the average value of d r i f t ra te i n the same gyro orientation measured on three successive days, shall not exceed the value specified i n the de ta i l specificatfsba when tested i n accordance w i t h 4.33.

3.23 Environmental sensitivity. The sensit ivity of a gyro to variations i n environmental conditions of air currents, magnetic fields, thermal radiation, ambient change, ambient pressure, spin motor excitation variation, spin motor excitation frequency varia-tion, pickoff excitation variation, and torquer excitation variation shal l not exceed the values specified i n the de ta i l specification.

Testing shal l be i n accordance with 4.34.

3.24 Vibration. The gyroscope shal l be capable of withstanding harmonic vibrations a t frequencies up to 2000 cycles per second at a force of 15 g% without damage o r loosening of parts.

i n accordance with 4.35, the gyroscope sha l l meet the requirements of 3.5, 3.6, 3.15, 3.18, 3.19, and 3.20 as applicable.

After testing

3.25 Shock. The gyro sha l l be capable of withstanding shock impacts at an acceleration of 50g and 11 flmil l isecond duration without damage, loosening of parts or degradation of performance characteristics.

After testing i n accordance w i t h 4.56, the gyro shal l meet the require-ments of 3.5, 3.6, 3.15, 3.18, 3.19, and 3.20 as applicable.

3.26 Altitude. The ,gyro shal l be capable of operation from sea level t o 100,000 feet.

shall meet the requirements of 3.6.

When tested i n accordance with 4.37 the gym

3.27 Moisture resistance. Gyros shal l be capable of operation and storage i n climates of high relat ive humidity.

ance with 4.38, gyros shal l meet the requirements of 3.5 and 3.6.

After testing in accord-

3.28 Sa l t atmosphere resistance. This test i s intended to detemine whether or not salt laden a i r w i l l damage the exterior of the gyro case by corrosion, or short c i rcu i t to the terminals, etc. After testing in accordance with 4.39, the gyro shal l be cleaned with d i s t i l l ed water and then dried. There shal l be no visible evidence of corrosion or other damage on the gyro exterior.

ments of 3.5 and 3.6, The gym shal l then meet the require-

3.29 Ambient temperature. When required by detail specification &ros shal l be capable of storage at the ambient temperature range specified i n the de ta i l specification.

with 4.40, gyros shal l meet the requirements of 3.5, 3.6, 3.15, 3.18, When tested i n accordance

3.19, and 3.20.

MIL=G- 81168 (w)

3.30 Radio noise, When tested in accordance with 4.41, radio

interference radiated into space shaïl be less than 2.5 peak microvolts per meter per kilocycle bandwidth from 0.15 to 65 megacycles and less than 5.0 peak microvolts per meter per kilocycles banãwidth from 55 to 150 megacycles.

not be in excess of the limlts in MIL-1-16910 and applicable detail specifications.

Radio interference conducted into the line shall

3.31 Operating life. Gyros shall be capable of operation for the period specified in the detail specification without failure. After testing in accordance with 4.42, gyros shall meet the requirements specified in 3.5, 3.6, 3.7, 3.8, 3.9, 3.12, 3.15, 3.18, 3.19, and 3.20.

3.32 Nameplate. The nameplate shall be of the size, location and contain the nameplate data as specified in the detail specification.

4. QUALITY ASSURANCE PFOVISIONS

4.1 Responsibility for inspection. Unless otherwise specified, quaïity control system requirements are per MIZ-&-9858.

is responsible for the performance of all inspection requirements as specified herein. Except as othemise specified, the supplier may utilize his awn or any other inspection facilities and services acceptable to the Government.

to perform any of the inspecfAons set forth in the specifications where such inspections frre deemed necessary to assure supplies and services conform to prescribed requirements.

The supplier

The Government reserves the right

4.2 Classification of inspections. Inspections of the rate integrating gyro shaU be classified as follars: qualification; preproduction;

periodic production; and acceptance inspection.

gyros manufactured in accordance with the requirements of the detail specification shall be subjected to the qualification tests detailed in Schedule 1 of Table I at an activity designated by the procuring activity. Production of the rate integrating gym prior to approval of the qualification sample, shall be at the supplier's risk. Each rate integrating gyro submitted shall be plainly identified by secure-ly attached durable tags marked with the following information;

4.3 Qualification. A qualification sample of four rate integrating

NIL-G-BLL68 6 6 W 7797706 OL42872 4 m '

MIL- G- 81168(W)

TABU I SCHEUULF, OF TESTS

Schedule 1 No. 1 - No. 40 Schedule 2 No. 1 - No. 29 Schedule 3 Asterisked

Test

1.

2.

3.

4.

5.

6.

7.

8.

9.

10 .

11 .

12 .

i 4 .

15.

16.

18.

19 * x).

21 .

22.

23 e

24.

25.

26.

28.

29.

32.

34.

36.

39 0

40 o

Visual and Mechanical Inspection Dielectric Strength Insulation Resistance Scale Factor Operating Temperature Run-up Time Parer Consumption Running Current Starting Current Impedance impedance N u l l Voltage Phase Shif t Pickoff Linearity Error N u l l Voltage Induced Voltage Gyro Scale Factor Input Angular Freedom Gyro Phasing N u l l Repeatability Cormnand Rate Scale Factor Torquer Linearity Error Hystersis Axis Alignment Reaction Torque Acceleration Insensitive Drift Acceleration Sensitive Drift Random D r i f t Day t o Day Stabi l i ty Characteristic Time E l a s t i c Restraint Environmental Sensitivity Vibration Shock Altitude Moisture Resistance Sal t Atmosphere Resistance Ambient Temperature Radio Noise Operating Life

NOTE: Test methods m.zy be found i n 4

Requirement

3.5 3.6 3.10.2 3.10.6 3.7.7 3.7.8 3.7010 3.7.9 3.8.4 3.9.9

. 3.8.5

3.8.6 .

3.8.7 3.9.10 3.10.4 3.12 3.13 3.14 3.15 3.9.5 3'9.6 3.9.7 3.17 3.9.11 3.18

3.22

3.19 3.20

3.16

3-23

3.25

3.21

3.24

3.26 3.28 3.28

3.29 3.30 3.31

Igh 4.31. T

Test Method

4.8 4-13 4.14 4.19.1 4.19.3 4.15.1 4.15.2 4.15.4 4.15.3 4.16

4.17.1 4.17.2 4.17.3 4.18.2 4.19.2 4.21 4.22 4,23 4.24 4.18.1 4.18.1 4.18.1 4.26 4.18.3 See note See note See note 4.33 4.25 4.32 4 . 9 4 . A 3 5

4. % 4.37 4.39

4.40 4.41 4.42

4.16

4.39

? specific method w i l l be i n the de ta i l specification.

MfL-G- $1168 (WP)

SAMPIX RIR QUALIFICATION INSPECPION

Gyroscope, mte Integrating Submitted by (manufacturer f s name, date )

Under authorization (reference letter authorizing tests )

(type number, if any) for

Qualification tests in accordance with MIL-G- (wp 1

4.3.1 Qualification Inspection. Qualification tests. shall be performed on rate integrating gyros that are representative of the equipnent to be supplied under the contract.

sample that has satisfactorily completed the tests detailed in Schedule 3 of Table I shall be submitted as required by 4.3 for the performance of the qualification tests described in Schedule 1 of Table I of this specification. The manufacturer shall submit cert-ified test results sharing satisfactory completion by the sample of al1 the Schedule 3 Table I tests. Failure of any sample to satisfactorily pass any of the tests shall require the manufacturer to follow the procedure described in 4,8.

4.3.2 Changes, After samples have been submitted for qualifica-tion, no change shall be made in the materials, design or manufacturing processes without approval of the qualifying activity, qualification inspection will be sufficient evidence for quali-fication approval and will place the supplier's name on the Qualified Products List for a period of two years, Re-evaluation of qualifica-tion approval will take place every six months, or when any of the foliowing conditions occur:

a. The supplier has modified the gym design.

b. The supplier has instituted a change in the

The specification requirements for the gyro have

The qualification

4.3.2 Qualification approval, Satisfactory completion of the

material used, or in the processing (see 4.5.8).

. been amended or revised to the extent that the qualifying activity believes that re-evaluation is necessary,

4.3.4 Disposition of sample units. Sample units subjected

to qualification tests shall not be delivered on any contract or order c.

c

4.4 Requalification, Qualification tests in accordance

with 4.3 shall be repeated every two years, or more frequently, a6 directed by the procuring or qualifying activity, i8

L Li

MIL-G-81168 b b m 777770b 0142874 8 I)

MIL-G- 81168 (WP)

4.5 Preproduction inspection. When requested by the procuring agency, sample gyros taken f r o m the f i r s t production l o t of each contract shal l be submitted for testing t o the qualification t e s t s of 4.3.

4.6 Periodic production inspection. Periodic production inspection samples shal l be selected from units tha t have sat isfactor i ly passed the quality conformance inspections of Schedule 3 as follows:

Step 1 - Three r a t e gyros selected a t random from the first lot .

Step 2.- One ra t e gyro selected at random f r o m each succeeding lot , unless,

a. A major change i n design occurs, a t which time, required by the procuring'activity, samples shal l be sutjmitted f o r 'preproduction inspection of the approved new design.

b. A unit fails to pass the tes ts . When a defective uni t is found i n any group, acceptance of all uni ts on hand shal l be withheld and the contractor shall:

(1) determine the cause of the defect

(2 ) take the necessary actions to correct o r eliminate the defect from a l l uni ts on hand, and, i f CO directed by the procuring activity, from those uni ts previously shipped.

( 3 ) submit t o ' t h e procuring activity f o r approval the proposed corrective action t o prevent recurrence of the defect.

The samples sha l l be forwarded to . the testing act ivi ty and be subjected t o a l l the tests described i n Schedule 2 of t h i s specification.

a securely attached durable tag marked with the following inform-ation;

Samples submitted sha l l be plainly identified by

MIL-G- 81168 (WJ?)

SAMPLE FOR PFOmfCMON INSPECIIION

Gyroscope, Rate Integrating submitted by (manufacturer's name, date) f o r production testing in accordance with M I M - Under contract number

4.7 Quality conformance inspection, Each production rate integrating gyro t o be delivered under the contract shall be subjected to thequality conformance tests of Schedule 3.

ments therein shall be cause for rejection.

tests shall be 100 rate gyros or any fraction thereof remaining on t h e contract.

(type, number, serial number)

(wp 1

Failure t o meet any of the require-

4.8 Production l o t size. The l o t size for the purpose of sampling

4.9 Failure. A gyro fai lure is any malfunction which causes

the gyro t o fa i l to meet the m i n i m u m performance requirements specified herein. Failure of any gyro i n any t e s t (except insu-lation t e s t s ) sha l l be cause f o r withholding approval. Whenever the ra te of insulation failures of gyros i n a production run (100 units) exceeds two per cent the entire run shal l be held f o r review by the procuring or qualifying activity. When a defective uni t i s found the contractor shall :

a.

b.

determine the cause of the failure.

take the necessary actions t o correct o r eliminate the defect from ail units on hand.

C. submit to the procuring activity for approval the proposed corrective action to prevent recurrence of the defect.

4 , i O Test conditions.

4.10*1 Standard test conditions. Unless otherwise specif led herein, a l l measurements and tests sha l l be made at an ambient temperature of 72 f 59., atmospheric pressure of 30 f. 2 inches Hg., and a relative humidity no greater than 55 per cent, temperature sha l l not exceed 5'F. per hour.

specified i n 3.7.4.

3.8.3. Iiorquer excitation shal l be as specified i n 3.9.4. Temperature sensor excitation Shall be as specified i n 3.ll.2.

Rate of change of

4.10.2 Test excitations. Spin motor excitation s h a l l be as Pickoff excitation shall be as specified i n

1 - - MIL-G-BLLbB 6 6 7997906 0342876 3

4.10.3 Stabilized operating temperature. The stabil ized operating temperature is the temperature of the gym when the temperature seasing element resistance is within t h e limits specified i n 3.10.3 and has stabil ized a t t h a t temperature for a period of one hour.

4.10.4 Gyro mounting accuracy. Unless specified otherwise, the test unit should be mounted i n such a w a y that the alignment of its three reference axes w i t h the test f ixture is maintainedwithin the limits specified i n the detail specification under a l l specified test conditions.

no undue stress can be exerted on the mounted gyro.

axes of the test unit are those defined by external case markings or mounting surfaces.

4.11 T e s t equipaent and inspection fac i l i t i es . Test equipment

The mounting f ixture should be designed such tha t The three reference and inspection f a c i l i t i e s sha l l be of sufficient accuracy and quality to permit perfomance of the required tests. Generally, t e s t equip-ment accuracy should be ten times greater than the measured tolerance.

The contractor shal l establish adequate calibration of test equipnent to the satisfaction of the procuring act ivi ty o r approved testing laboratory.

generally:

The function tests performed f a l l i n one of two categories

a. Servo turntable loop. Tes ts on a single axis turntable where the gyro output signal controls a servo rotating the turntable and w i t h it the gyro case about its input axis, and

b. Servo rate loop. Tes ts in which the gyro output signal controls the gyro torquer directly such as to maintain the output axis at nul l ( see Figure 2 and Figure 3).

4.11.1 General precautions and recmendations. In both types of function tests the gyro should be mounted on a test stand sufficiently stable and isolated from disturbing torques and forces i n the surround-ing structure o r building.

design of servo loops should be based on accuracy requirements compatible with the performance specifica%ions. Similarly, the bandpass of the meters used should be chosen such as to provide fnformation within the frequency spectrum of interest for the tests, especially i n the case of drift tes ts . Since most rate integrating gyros are high precision units, special care is required to maintain proper operating conditions and t o eliminate external disturbing influences such as temperature gradients and fluctuations. Magnetic fields, stress on the unit due t o mounting conditions, etc. A l l tests should be per-formed i n a w e l l controlled laboratory environment.

The selection of test equipnent and the

4.11.2 Description of test equipnent. In addition to a stable base structurally independent of the adjacent floor and a gyro mounting fixture, each of the following is required i n one o r more of the tests specif led:

a.

f r o angaar readout . Single-axis servo driven turntable which can be t i l t ed horizontal to vert ical and which i s equippedwith a precision

MIL-G- 81168 (w)

I t r-- I I I I I I I I

I I I I I I I I I t I

I r I l t I I I I I I I I I I I t I I c

C .

NIL-G-ôLLb8 bb W 7777706 0342878 5 I

I

M

b. Single-axis angular displacëment inputs (such as dividlng head).

c.

de

Single-axis turntable with precision rate &iver

Single-axis oscil lating table w i t h means of driving it sinusoidally at known variable frequencies.

by passing the pickoff signal output through and amplifier and phase sensitive demodulator into the torquer control f i e l d with the gyro normally excited (see Figure 2).

that the d - c demodulator signal be modulated and f i l t e red t o provide an a - c sine wave rebalance current to the torquer (See Figure 3) .

The servo gain s h a l l be as specified i n t h e detai l specification. The current measuring system normally consists of a precision fixed resis tor i n series with t h e torquer control winding, the rebalance current is then propoi*t;ional to the voltage drop across the resistor. For a - c torquers a current product resolver may be used to obtain a direct measurement of current product. A - c torquers require that the output impedance of the s e m be at leas t 25,000 ohms. Unless otherwise specified the input impedance load of the servo amplifier on the pickoff shall not be less than 0.5 megohm shunted by not more than 350 picofarads.

4.12 Visual and mechanical inspection. The gyro shall be carefully inspected to determine t h a t the dimensions and finishes conform to the applicable detai l specification.

of the magnitude specified by 3.5 shal l be applied to the indicated t e s t points.

3 seconds) to the specified value and held at t h a t value f o r one minute;

then reduced slowly (minimum time 3 seconds) to zero, of the test potential through out t h i s test shal l not exceed 1.5 times the specified test potential. The gyro shal l be maintained at operating temperature as specified i n 4.10.3. A failure shal l be indicated by a winding leakage current i n excess of one peak milliampere or the indica-t ion of internal arcing o r corona dischwge. Inmediately a f te r success-ful ly completing the dielectric strength t e s t the insulation resistance t e s t (4.14) shall be performed.

4.14 Insulation resistance test. The d -c. resistance between spebi-f ied t e s t points s h a l l be measured with 500 volts d - c applied.

temperature of the gyro shal l be the operating temperature as specified i n 4.10.3.

er Servo ra te loop. The servo rate loop is the servo loop formed

For a - c torquers the system requires

4.13 Dielectric strength. Dielectric strength test. A t e s t potentiaï

The t e s t potential shal l be raised slowly (minimum time

The peak value

The

4.15 spin motor tests.

4'15.1 Run up time. With the gyroscope a t operating temperature, the spin motor shal l be excited as specified i n 3.7.4.

required for the spin motor t o reach synchronous speed shall be deter-mined by observing a drop i n l ine current and s h a l l not exceed the value specified i n 3.7.7.

The run up time

_ - 24 c

MIL-G-83168 hh 7997906 O342880 3 9 c-3b-o\ --

MIL-G-8LI-68 (WP)

4.15.2 Power consumption. The spin motor parer consumption shal l be measured with the gyroscope energized and stabil ized as specified i n 4.10.2 and 4.10.3 and shal l not exceed the value specified i n 3.7.8.

4.15.3 Starting current. The gyroscope sha l l be energized and stabil ized as specified i n 4.10.2 and 4.10.3.

t o the spin motor and allow the motor t o stop.

excitation is reapplied and current i n esch phase measured during run-up time from zero t o synchronous speed.

phase shal l not exceed the value specified i n 3.7.9.

Remove the excitation The spin motor

The peak current of any

4.15.4 Running current. The spin motor .running current shal l be measured with the gyroscope energized and stabil ized as specified i n

4.10.2 and 4.10.3.

i n 3.7.10.

Running current shal l not exceed the value specified

4.16 Impedance. The gyroscope shal l be stabil ized as specified i n 4.10.3.

winding sha l l be within the limits specified i n 3.8.4 and 3.9.9.

Measure the inductance using an excitation of 2 milliamperes IPUIS at

The inductance and d - c resistance of the pickoff and torquer

1000 cps.

4.17 Pickoff tes ts .

4.17.1 Null voltage. The gyroscope sha l l be mounted i n a dividing head and t e s t stand as specified i n 4.11with the input reference axis paral le l to the axis of rotation of the dividing head, within f1.5 degrees.

Excite and s tabi l ize the gyro as specified i n 4.10.2 and 4.10.3.

nul l voltage is the minimum pickoff voltage obtained by rotating the dividing head.

average value of the voltage wave i n terns of the EF.IS value of an equivalent sine wave and sha l l have an input impedance of a t l ea s t 1 megohm resistance shunted by capacitance of 30 picofarads.

The

The voltage measuring devices used sha l l indicate the

4.17.2 Phase shif t . The gyroscope sha l l be mounted, energized, and stabil ized as i n 4.17.1 above.

by applying a torquer current o r rotation about the IA.

sh i f t between the pickoff primary and secondary voltages shal l be measured using a device which indicates o r compares the phase s h i f t t o an accuracy of i.15 minutes and does not a l t e r the open c i rcu i t voltages by more than 0.1 per cent.

Rotate the gimbal t o the positive l i m i t The phase ß

4.17.3 Pickoff l inear i ty error. The gyroscope shal l be mounted, energized, and stabil ized as i n 4.17.1. Apply the input angular displacement specified i n the de ta i l specification t o the gyro.

Measure the corresponding gyro pickoff output.

reading shal l not exceed 1 second i n order t o minimize the effects

The time fo r each

MIL-G- 81168 (W)

of earth's ra te and systemstic drift rate.

of the input-output data from the least squares straight line.

error i n per cent equals the value of t h i s deviation times 100, di-vided by one-half the input range.

Find the maximum deviation Linearity

4.18 Torquer tests.

4.18.1 Comand rate scale factor, l i n e w i t y error and hystersis.

T e s t equipment includes base mounting fixture, excitation supplies, single-axis servo driven turntable, associated servo amplifier and electronics, precision current supply and timer.

with the input reference axis vertical , Energize and s tabi l ize as specified i n 4.10.2 and 4.10.3.

t h e turntable servo t o maintain the gyro pickoff output within 5 millivolts of null.

specification to the gyro torquer. Measure the correspondin@; rate outputs of the servo driven turntable for each of the input currents i n the following sequence.

to zero, increase to negative input limit, return to zero, and increase to positive input limit.

variations of performance characteristics w i t h output angle are of interest.

be specified for the t e s t series. In order to operate the gyro at; an output angle other than zero, a properly phased constant bias vol twe s h a l l be inserted i n ser ies with the g y m pickoff output.

operational perfornance characteristics l i s t e d below are based on the terns 3.2.25 and 3.2.26. Cormnand rate scale factor is t h e slope of the straight l i n e t h a t can be f i t t e d by the method of least squares to the input-output data obtained from the t e s t above.

Torquer l inear i ty error.

output data from the leas t squares straight line.

i n per cent equals the value of t h i s deviation times 100, divided by the maximum command rate.

Hysteresis is the difference between outputs for increasing and decreasing input a t tha t input for which the difference i s maximum, measured after cycling through the input range and expressed as a per cent of one half of the output range.

4.18.2 N u l l voltage. With the gyro pickoff maintained a t n u l l

as. Specified i n 4.17.1 the output voltage of the torquer control winding shal l be measured w i t h a voltage measuring device as speci-f ied i n 4.17.1.

Mount the t e s t uni t

Connect t h e gyro pickoff output t o

Apply the input currents specified i n the detail

Start w i t h positive input l i m i t , return

In some applications Repeat t h i s cycle 3 times.

In such cases, t h…