DE3033281A1 - ARRANGEMENT FOR DAMPING NUTATIONAL VIBRATIONS IN DYNAMICALLY ADJUSTED, TWO-AXIS POSITIONER - Google Patents

Description

PATENT LAWYERS Dipl.-Phys. JÜRGEN WEISSE · Dipl.-Chem. Dr. RUDOLF WOLGAST

BOKENBUSCH41 D 5620 VELBERT H- LANGENBERG Box 110386 Telephone: (02127) 4019 Telex: 8516895

^ Patent application

Bodenseewerk Geräteechnik GmbH, D-7770 Überlingen (Lake Constance)

Arrangement for damping nutation vibrations with dynamically coordinated, two-axis position circle eln.

The invention relates to an arrangement for damping nutation vibrations in dynamically tuned, biaxial Attitude gyroscopes with a first and a second input axis perpendicular thereto, a first and a a second position tap, which reacts to relative movements between the gyro rotor and the housing around the first or address second input axis, and a torque generator that is effective around the first input axis.

A two-axis position gyro seeks to maintain its orientation in space in the absence of external torques. Movements of the gyro housing with respect to the gyro rotor, i.e. opposite measured in inertial space. The tap signals can be used, for example, to stabilize a Platform can be switched to servomotors. at

^OJ such positional gyroscopes, it is essential that as few moments as possible be effective via the bearing on the gyro rotor. It is known to design such two-axis position gyros as so-called "dynamically coordinated gyroscopes".

BATH ORIGINAL

^ Λ- to form. In such dynamically tuned gyroscopes, the rotor is connected to the drive shaft of the motor via a cardan ring, which is connected on the one hand to the drive shaft via a spring joint and on the other hand to the rotor via a spring joint arranged perpendicular to it. When the gyro housing was deflected in relation to the gyro rotor, the spring joints would normally cause a moment on the gyro rotor, which would cause it to change its reference position in space. In the case of a dynamically tuned gyro, the tuning is chosen so that the moments caused by the spring joints are compensated for by dynamic moments. These dynamic moments are caused by an oscillating movement of the gimbal that occurs when the gyro housing is deflected relative to the fixed gyro rotor.

DE-OS 25 ^ 5 025 is a navigation device for Navigation of land vehicles known with a north-looking merisian gyro to determine the north direction and a free gyro that can be aligned with the meridian gyro as a course reference device. A speed sensor generates a signal proportional to the driving speed. A computer determined from the course angle of the course reference device and the signal of the speed sensor the position of the vehicle. A correction signal that is dependent on the geographical latitude is generated from the position signals and switched to the free gyro or taken into account in the computer, which is caused by the rotation of the earth Emigration of the free gyro compensated for relative to the earth-fixed coordinate system.

In a practical implementation of such a navigation device a dynamically tuned gyro was used as a two-axis attitude gyro. It

BATH ORIGINAL

it was found, with the navigation device usually functioning perfectly, that with a certain Driving speed of the vehicle the gyro began to wander out of a correct position and ran against the stop.

Similar phenomena have also been observed in other applications of dynamically tuned attitude gyros.
10

The invention is based on the object of avoiding such a migration of the position gyro.

According to the invention, this task becomes dynamic in the case of a matched position gyro of the type mentioned above solved in that the signal of the first Tap via an essentially differentiating attenuation network on the one around the first input axis effective torque generator is switched.

The invention is based on an investigation of the causes of the disruptive effect described and the knowledge that this undamped nutation vibrations are responsible, which are stimulated to resonance.

The invention provides a circuit for the position gyro before, which on the one hand dampens the nutation vibrations but on the other hand those which are important for the function Properties of the position gyro are unaffected.

An embodiment of the invention is shown below with reference to the accompanying drawings explained in more detail.

Pig · 1 schematically shows the structure of a

two-axis attitude gyro.

BATH ORIGINAL

Figure 2 is an idealized block diagram

and illustrates the interaction of moments and deflections around the two input axes.

Fig. 3 is a perspective, schematic Representation of a dynamically coordinated two-axis attitude gyro.

Fig. U- is a longitudinal section through a structural design of a dynamically coordinated two-axis position gyro

Fig. 5 shows the arrangement of such. Gyro in a course reference

device.

Fig. 6 shows the structure of the damping network.
20th

7 shows as a block diagram the type and arrangement of the damping network in FIG a course reference device.

in Fig. 1 is for better understanding and definition of the designations used, a two-axis position gyro is shown schematically. The gyro rotor 10 revolves around its twist axis 12. The twist is denoted by H. The gyro rotor 10 is around a ' to the twist axis 12 perpendicular axis. 1A- in one Inner frame 16 stored. The inner frame 16 is in one about an axis 18 perpendicular to the axis 14 Centrifugal housing 20 stored.

The axis 18 forms the first input axis or x-axis of the position gyro. The axis 14 forms the second input axis or y-axis of the attitude gyro.

BATH ORIGINAL

A first position tap 22 and a first torque generator are seated on the first input axis 18 A second position tap 26 and a second torque generator are seated on the second input axis 14

The moments acting around the first input axis 18 and the second input axis 14 are denoted by Mm and M ^, ^α and P are the deflections of the housing 20 relative to the inertial space around the first and the second input axis 18 and 14, respectively Taps 22 and 26 become tap signals. or β . tapped. The deflections of the gyro rotor 10 with respect to the inertial space around the first and second input axis 18 and 14 are denoted by « _R

or ß -n denotes.

Fig. 2 shows the relationship between the moments M _m , M _rn and the deflections ^a , P and <* _Ώ , B _n

XX IJ ti ^r K

and β β . A deflection P "of the gyro rotor 10 about the second input axis or y-axis causes a moment about the first input axis or x-axis with a transfer function Hs, and vice versa causes a deflection ■ _{R of} the gyro rotor 1.0 about the first input axis or x-axis Moment about the second input axis or y-axis with the same transfer function. In this, H is, as I said, the twist and s the Laplace operator. A moment M _m or Μφ about an input axis causes a deflection α _R or P _R about the same input axis with the transfer functions

respectively-

VI s ²

^x 'y

BAD ORSai ^ Ä

2033281

where I and I are the moments of inertia around the x and χ y, respectively

y-axis are. The tap signals supply the differences β- · «or P- β _{R of} the rotary movements of the housing 20 and the gyro rotor 10 with respect to the
inertial space.

If there are no moments Mg,, My acting around the input axes 18 and 14, ^α _R = P _R = 0, and the tap signals ·. and P. immediately deliver the
Rotational movements α and P of the gyro housing 20 with respect to the inertial space.

However, due to imperfections in the gyro that are always present as well as due to environmental influences, disturbance torques always occur which stimulate an undamped characteristic oscillation of the two-axis gyro, the so-called "nutation oscillation". These
Nutation vibration has the frequency

(Ό - " -

This oscillation caused by the nutation oscillation in the pick-up signals of the position gyro

parts are usually filtered out by comb filters. The system consisting of the gyro rotor 10 and the inner frame 16, however _{, carries out these vibrations t}

Fig. 3 is a schematic perspective view

setting of a dynamically coordinated, two-axis attitude gyro.

The position gyro 30 contains a motor fixed to the housing

32 with an elongated drive shaft 3 ^ · With 35

the drive axle 34 is a gimbal ring 36 over a inner spring joint 38 connected. The gyro rotor is in turn connected to the cardan ring 36 via an outer, connected to the inner perpendicular spring hinge 42.

-A- With regard to the kinematic conditions, the inner spring joint 38 corresponds to the input axis 18 of FIG. 1, the cardan frame 36 to the inner frame 16 and the outer spring joint 42 to the second input axis 14. The drive axis 34 of the motor 32 is mounted fixed to the housing with this and fulfills at the same time the function of the "gyro housing" in the schematic representation of Fig. 1 and the rotor drive. The system is coordinated in a known manner so that the moments exerted by the spring joints 38 and 42 by their spring force on the gyro rotor 40 are compensated for by dynamic moments which are caused by an oscillating movement of the gimbal ring 36 when the gyro housing 44 is deflected relative to the fixed gyro rotor 40.

The structural design of such a dynamically coordinated position gyro 30 is shown in FIG Longitudinal section shown. The motor 32 with an external stator is seated on the gyro housing 46 and an internal rotor 48. The rotor is connected to the drive axle 3 ^ via bearings 50, 52 in the Housing 44 mounted. At the end of the drive axle facing away from the motor 32, the (not shown) Spring joint and gimbal arrangement of the gyro rotor 40 supported. The location of the gyro rotor 40 relative to the gyro housing 44 is tapped in two mutually perpendicular planes by taps 5 ^, which correspond in their function to the taps 22 and 26 of FIG. 1 * In addition, they are torque generators 56 is provided, through which, in a known manner, torques about the two to one another vertical input axes are exercisable and which

* "the torque generators 24 and 28 of the schematic 1 correspond to the representation of FIG.

BATH ORIGINAL

In the moment equations for the two input axes, x-axis and y-axis, shown in the housing fixed In the system, the terms specified using the example of the x-axis in equation (2) occur:

(2) σ Μ _Τχ = 2c (β _A cos 2 ω t + ß _A sin 2 ω t) +

"C" is a residual spring constant of the spring joint 38 (FIG. 3) as a result of the imprecise dynamic coordination of the position gyro with a cardan ring 36 ^ and ^ω is the angular frequency of the gyro rotor 40.

Assuming angular vibration results in a sinusoidal housing deflection such that

(3) » _A = α _ο sin

this leads to the following torque component in equation (2):

= C * α ₀ ^Sin ( ^{2w + Q} ) - ^c «o ^Sin

The nutation oscillation of the position gyro 30 is undamped. Every periodic excitation from outside with the frequency ω "of the nutation vibrations increases them Amplitude further. The nutation oscillation of the position gyro is then excited in its natural resonance, which causes the deflection due to the lack of damping dec circle ;; elrotors 40 increases steadily until the Kreisirc tor sweeping the stops is running.

BATH ORIGINAL

The nutation frequency ω _N is less than twice the angular frequency ω of the gyro rotor 40 in the dynamically tuned position gyros under consideration here

(5) Q = 2 ω - ω _Ν

so it turns out

(6) ■ (2 _ω - Q) = ω _Ν .

If the gyro housing 44 executes angular vibrations at the frequency Q given by equation (5), disturbance torques occur around the x-axis, the frequency of which is equal to the nutation frequency ω _N. The undamped nutation oscillation is excited in resonance, which has the consequences described above.

The order of magnitude of the frequency ß should be based on a numerical example explained:

When a two-axis attitude gyro is used

-1

_{ω w} = 2 ir * 461 sec, 30th

ω = 2 π * 240 sec " ¹ or

2 ω = 2 η ' 480 sec " ¹ .

This results in

Q = 2 »- ω _N = 2π * 19 sec" ¹ ,

BATH ORIGINAL

Since excitation frequencies of 19 Hertz are to be expected in practice, this results in many Cases with devices that contain such attitude gyros as sensors, dynamic problems. Sample wines was in a vehicle navigation device according to the type of DE-OS 25 45 025, which is in a tracked vehicle was used, an emigration of the Lagekreiselfi was observed when extending from the length of a Chain link and the vehicle speed resulting frequency reached the value of 19 Hertz.

Since os is a systematic effect in the described phenomenon, it cannot be switched off with dynamically coordinated position gyros with only one gimbal ring. The only countermeasure could be to reduce the impact of this effect by attenuating the nutation frequency through external wiring. Care must be taken to ensure that the gyro is a position gyro with the transfer function "1" between β and <^. or ß and ß _A (Fig. 2) largely retained. It must also be ensured that the gyro shows the correct tracking behavior, for example in a vehicle navigation system according to DE-OS 25 45, if it is to be kept in the "grid north" direction to take into account the rotation of the earth by a tracking signal, as described above .

It has been shown that such a circuit is possible (but only one). This is shown in FIGS.

In Tig. . · ^Γ is scheraatisch perspective inch · a share price "reffrenzperät with a biaxial dynamically abgesiimmten attitude gyro in the manner of Fig. 4.

BATH ORIGINAL

The course reference device contains an outer frame 58 which is rotatably mounted about an axis 60 in a device housing 62. An inner frame 64 is mounted in the outer frame 58 so as to be rotatable about an axis perpendicular to the axis 60. In the inner frame 64, a platform 68 is rotatably mounted about an essentially vertical azimuth axis 70 which is perpendicular to the axes 60 and>■■>&. The platform 68 can be rotated about the azimuth axis 70 by an azimuth servomotor 72.

^{The position gyro 3 ()} is arranged on the platform 68 in such a way that the spin axis H runs horizontally and essentially radially to the azimuth axis 70, the x-axis is arranged vertically and the y-axis is horizontally perpendicular to the spin and x-axes.

A servomotor 74, by means of which the housing 4-4- of the position gyro oO can be rotated about the y-axis, is also seated on the platform 68.
20th

Like from Pig. 5 and 7 is the signal of the x-tap 54-A via a preamplifier 76, a Demodulator 78 and a suitable network 80, which is indicated in FIG. 5 by the amplifier 82, to the Azimuth servomotor 72 switched. The signal of the y-tap 54- B is via a preamplifier 8 ^, a Demodulator 86 and a network 88 connected to servomotor 74. In this way, the housing 44 the gyro rotor 4-0 is always tracked. The gyro rotor 4-0 remains fixed in space with respect to the inertial one Space. Through a moment on the moment generator 56 B acting about the y-axis, the twist arbor H can with it an angular velocity with respect to the inertial space around the x-axis, which

^OD compensates the flow of the earth's rotation and keeps the twist axis H in a fixed relationship, for example, to the "grid north" direction of a UTM grid. From a pilot sensitive about the y-axis (not shown in Pig. 5)

. sor 90 (Fig. 7) »e.g. a dragonfly, a signal via a demodulator 92 and a filter 94- the torque generator 56 A effective about the x-axis is given. This ensures that the The spin axis of the position gyro 30 is always horizontal. The structure of the course reference device described so far is known per se.

For damping the nutation vibrations, the signal from the tap effective around the x-axis is now 5 ^ - A Also connected via a damping network 96 to the torque generator 56 A which is effective about the x-axis. As can be seen from FIG. 7, this is preamplified by the preamplifier 76 and through the tap signal demodulated by the demodulator 78.

via the attenuation network 96 of a summing circuit 98 and added to the signal of the pilot sensor 90, the sum on the torque generator 56 A is switched on.

The damping network 96 is detailed in FIG shown.

An input voltage Ug of the damping network 96 is connected to the input of an operational amplifier via a capacitor C and an ohmic resistor Rg 100 on. The output voltage U. of the damping network = plant 96 at the output of the operational amplifier 100 is via a negative feedback resistor and R ^ - on the Input of the operational amplifier fed back.

The transfer function of this damping network 96 is

(7) U _A (s) K _K C * ε

(s) 1 + R _E Cs

BATH ORIGINAL

where s is again the Laplace operator. if

(8th) will ^R E C s <£ 5 is, (9) U. Cs) ^U E (s)

i.e. the network 96 has a differentiating character and operates at a sufficiently high corner frequency of the Denominator as an ideal differentiator and thus as an ideal attenuator.

As mentioned above, the choice of the damping network allows the normal behavior of the attitude gyro 30 cannot be falsified too much. There have been attenuations for the nutation frequencies of

2Q 0.1 to 0.2 proved to be suitable. For a damping factor of 0.1, the associated gain V of the damping circuit formed from damping network 96 and torque generator 56 A results in V = 36 ρ cm see. If the time constant R _x , ^# 0 is selected to be sufficiently small, the value of the product R - ^ - C is also determined by the value of V found. The circuit according to FIG. 6 is thus dimensioned.

Claims (2)

Claims Arrangement for damping nutation vibrations in dynamically coordinated, two-axis position gyroscopes with a first and a second input axis perpendicular thereto, a first and a second position pick-up, which reacts to relative movements between the gyro rotor and the housing address the first and second input axis, and a torque generator around the first Input axis is effective, characterized in that the signal of the first tap (54 · A) has an essentially differentiating one Damping network (96) on the torque generator effective around the first input axis (x) (56 A) is switched. 2. Arrangement according to claim 1, characterized in that
30th (A) the attitude gyro (50) with a course gyro horizontal twist axis (H) and (b) the first input axis (x) is vertical. BATH ORIGINAL 3. Arrangement according to claim 1 or 2, characterized in that the damping network (96) contains an operational amplifier (100) at the input of which there is an input voltage (Up) via the series connection of a capacitor (C) and a resistor (Rg) and its output voltage , which forms the output voltage (U.) of the damping network (96), is fed back to the input of the operational amplifier (100) _{via a negative feedback resistor (R K).}