DE102022130886A1 - DIRECTION MEASURING METHODS AND DIRECTION MEASURING DEVICE - Google Patents

Abstract

The invention relates to a method for determining the direction of an object in a rotating reference system and to a device for carrying out the method. According to a first aspect, the stated object is achieved by a method for measuring the direction of a linearly accelerated and/or rotationally accelerated object in a rotating reference system, wherein the movement of a first test mass and a second test mass, which are suspended at a distance from one another in a rotating gyroscope serving as a reference system, is recorded as a sum signal, wherein the distance between the two test masses is less than 10 mm, preferably less than 5 mm and particularly preferably less than 2 mm, and in addition a difference between the movement of the first test mass and the movement of the second test mass is measured.

Description

The invention relates to a method for determining the direction of an object in a rotating reference system and to a device for carrying out the method. In particular, the invention relates to a method and a device for determining the direction of an object in a rotating reference system for navigation applications.

Direction measurement is a fundamental task of geodesy, geometry, astronomy, navigation and other areas of technology. It consists of an oriented angle measurement to determine horizontal angles or oriented measuring rays in a defined reference system. The reference system can be absolute. For example, many direction measurements on Earth refer to geographic or astronomical north, namely the horizontal direction that leads to the geographic North Pole. In many other cases, a reference to an absolute reference system is not useful or even impossible. One example of such a case is space travel. In these cases, a relative reference system can be defined to which the direction measurement refers.

Knowing the direction of an object is essential for navigation applications, for example. For example, when navigating flight paths, especially over long distances, such as in spacecraft navigation, the direction must be determined very precisely, since even the smallest deviations from a certain direction to the actual direction of an object can lead to large deviations in reaching a predetermined destination.

In the state of the art, gyroscope instruments, also called gyroscopes or gyros for short, are known for measuring direction, especially in a relative reference system. A rapidly rotating, symmetrical gyroscope rotates in a movable bearing. The bearing can be, for example, a gimbal suspension or a frame in the form of a cage. Due to the conservation of angular momentum, the gyroscope has a high degree of inertia with regard to changes in position in space. Gyros are used as navigation instruments and for active attitude control, especially in aviation and aerospace. When controlling the attitude of spacecraft such as satellites, it is exploited that the overall system of spacecraft and gyroscope maintains its angular momentum and thus the position can be controlled by transferring angular momentum between the two. A gyroscope system can be viewed as a closed system whose angular momentum remains constant. If an external force tries to tilt the axis of rotation of the gyroscope, a torque perpendicular to the force results, which the angular momentum strives to match according to the rule of parallelism in the same direction. The angular momentum tilts perpendicular to the applied force. The axis of rotation is coupled to the angular momentum via the inertia tensor, which is why the gyro axis follows the angular momentum and orbits it in a narrow cone. In a symmetrical gyro, the opening angle of the cone is inversely proportional to the square of the speed and the ratio of the axial to the equatorial main moment of inertia of the gyro.

The term gyro is now used in a figurative sense for a variety of angular rate sensors that do not contain gyros but serve the same purpose as an actual gyroscopic instrument.

(Grad pro Quadratwurzelstunde). Dabei beschreibt ARW das weiße Rauschen am Ausgang eines Gyros, wobei weißes Rauschen ein Rauschen mit einem konstanten Leistungsdichtespektrum in einem bestimmten Frequenzbereich ist und häufig verwendet wird, um Störungen in einem sonst idealen Modell zu beschreiben. Auf der Messung der Corioliskraft basierende Winkelkreisel für Navigationszwecke erreichen derzeit nicht die Leistung von faseroptischen Kreiseln (FOG), die auf dem Sagnac-Effekt beruhen und eine Leistung von $\mathrm{0,0001}°/\sqrt[2]{h}$

erreichen können, dafür aber mit bis zu 12 kg schwerer und größer sind.A rotating reference frame generates three so-called fictitious forces, namely the Coriolis force, the centrifugal force and the Euler force. The overwhelming majority of commercial gyro designs are based on the Coriolis force, which measures the rate of rotation of the reference frame. This angular velocity must be integrated once to obtain the angular orientation of the frame. Angle gyros based on the measurement of the Coriolis force for navigation purposes vary in performance and size, with some of the smallest measuring 12 mm × 12 mm × 6 mm and having an Angle Random Walk (ARW) of $0.001°/\sqrt[2]{H}$

(degrees per square root hour). ARW describes the white noise at the output of a gyro, where white noise is noise with a constant power density spectrum in a certain frequency range and is often used to describe disturbances in an otherwise ideal model. Angle gyros based on the measurement of the Coriolis force for navigation purposes currently do not reach the performance of fiber optic gyros (FOG), which are based on the Sagnac effect and have a performance of $0.0001°/\sqrt[2]{H}$

but are heavier and larger, weighing up to 12 kg.

Dieser Fehler akkumuliert sich mit der Zeit. Er kann zwar kompensiert werden, wenn man über eine stabile, langfristige Referenz verfügt, mit der man vergleichen kann. Dies kann der Schwerkraftvektor der Erde in Kombination mit dem magnetischen Nordvektor der Erde sein. Diese Vektoren werden dabei mit separaten Beschleunigungsmessern und einem Magnetometer gemessen. Außer bei MEMS-Kreiseln, also Kreiseln basierend auf mikroelektromechanischen Systemen, bei denen die Beschleunigungsmesser und Magnetometer Millimeter voneinander entfernt auf demselben Chip untergebracht werden können, sind die anderen Sensoren separat verpackt verpackt und befinden sich in einem gewissen Abstand zueinander, der durch die individuellen Abmessungen für jeden Sensor begrenzt ist. Dies führt zu einer erhöhten Empfindlichkeit gegenüber Umgebungseinflüssen wie Temperaturschwankungen oder Vibrationen, da die Sensoren nicht denselben Punkt im Raum abtasten und die gemeinsame Befestigungsstruktur nicht vollkommen starr ist. Mit anderen Worten können der Abstand zwischen den Sensoren und ihre Ausrichtung zueinander driften, also sich zumindest vorübergehend verändern. Zwar kann durch Kombination der Daten der einzelnen Sensoren mit einem Filteralgorithmus der Kreisel-ARW kompensiert werden. Unabhängig davon führt das Ergebnis aber letztlich zu einer Hochpassfilterung des Kreiselsignals, wodurch der Kreiselbeitrag für Zeitintervalle eliminiert wird, die länger sind als eine Cut-on-Frequenz des Filters. Die Unterdrückung von Signalen mit langer Zeitskala aus den Kreiseldaten bedeutet, dass die ARW-Kennzahl nicht die Leistung korrekt darstellt, da vom Kreisel zumindest bei terrestrischen Navigationsanwendungen nicht erwartet wird, dass er von sich aus eine Winkelorientierung über Stunden hinweg liefert.Regardless, all of these gyros measure angular velocity. In order to generate an angular orientation of the reference system required for navigation applications, they must perform an integration over time. However, any residual error in the angular rate measurement, for example due to sensor noise, leads to a random walk, i.e. a random movement of the angular orientation after integration with a performance indicator ARW already mentioned above in the order of magnitude of $0.001°/\sqrt[2]{H}.$

This error accumulates over time. It can be compensated for by having a stable, long-term Reference with which to compare. This can be the Earth's gravity vector combined with the Earth's magnetic north vector. These vectors are measured using separate accelerometers and a magnetometer. Except for MEMS gyros, i.e. gyros based on microelectromechanical systems, where the accelerometers and magnetometers can be housed millimeters apart on the same chip, the other sensors are packaged separately and are located at a certain distance from each other, which is limited by the individual dimensions for each sensor. This leads to increased sensitivity to environmental influences such as temperature fluctuations or vibrations, since the sensors do not scan the same point in space and the common mounting structure is not completely rigid. In other words, the distance between the sensors and their orientation to each other can drift, i.e. change at least temporarily. It is true that the gyro ARW can be compensated for by combining the data from the individual sensors with a filter algorithm. Regardless, the result ultimately leads to high-pass filtering of the gyro signal, eliminating the gyro contribution for time intervals longer than a cut-on frequency of the filter. The suppression of long timescale signals from the gyro data means that the ARW figure does not accurately represent performance, since the gyro is not expected to provide angular orientation for hours on its own, at least in terrestrial navigation applications.

The present invention is based on the object of providing an improvement or an alternative to the prior art.

According to a first aspect, the stated object is achieved by a method for measuring the direction of a linearly accelerated and/or rotationally accelerated object in a rotating reference system, wherein the movement of a first test mass and a second test mass, which are suspended at a distance from one another in a rotating gyroscope serving as a reference system, is recorded as a sum signal, wherein the distance between the two test masses is less than 10 mm, preferably less than 5 mm and particularly preferably less than 2 mm, and in addition a difference between the movement of the first test mass and the movement of the second test mass is measured.

• Es sei ausdrücklich darauf hingewiesen, dass im Rahmen der hier vorliegenden Patentanmeldung unbestimmte Artikel und unbestimmte Zahlenangaben wie „ein...“, „zwei...“ usw. im Regelfall als mindestens-Angaben zu verstehen sein sollen, also als „mindestens ein...“, „mindestens zwei...“ usw., sofern sich nicht etwa aus dem Kontext oder dem konkreten Text einer bestimmten Stelle ergibt, dass etwa dort nur „genau ein...“, „genau zwei...“ usw. gemeint sein soll. Weiterhin sind alle Zahlenangaben sowie Angaben zu Verfahrensparametern und/oder Vorrichtungsparametern im technischen Sinne zu verstehen, d.h. als mit den üblichen Toleranzen versehen zu verstehen. Auch aus der expliziten Angabe der Einschränkung „wenigstens“ oder „mindestens“ o.ä. darf nicht geschlossen werden, dass bei der einfachen Verwendung von „ein“, also ohne die Angabe von „wenigstens“ o.ä., ein „genau ein“ gemeint ist.

The following terminology is used to explain this:

• It should be expressly pointed out that in the context of this patent application, indefinite articles and indefinite numerical statements such as "one...", "two...", etc. should generally be understood as at least statements, i.e. as "at least one...", "at least two...", etc., unless the context or the specific text of a particular passage indicates that only "exactly one...", "exactly two...", etc. are meant there. Furthermore, all numerical statements and statements on process parameters and/or device parameters are to be understood in the technical sense, i.e. as subject to the usual tolerances. Even the explicit specification of the restriction "at least" or "at least" or similar must not be used to conclude that "exactly one" is meant when "one" is simply used, i.e. without specifying "at least" or similar.

A "directional measurement" consists of an oriented angle measurement to determine horizontal angles or oriented measuring rays in a defined reference system. The reference system can be absolute. For example, many direction measurements on Earth refer to geographic or astronomical north. In many other cases, a reference to an absolute reference system is not useful or even impossible. One example of such a case is space travel. In these cases, a relative reference system can be defined to which the direction measurement refers.

In this text, an “object” is a body whose direction is to be determined.

A "test mass" is a mass whose linear acceleration and/or angular acceleration is measured. A test mass can be intended for this purpose only in an object. However, it is also possible to use a mass that was originally intended for another purpose in the object as a test mass.

A "gyroscope" is a body that rotates around an axis. The terms "gyroscope" or "gyro" for short are used in this document as synonyms for a gyroscope. The terms are also used for a measuring instrument that performs a similar task to a gyroscope, even if it does not contain a rotating gyroscope. Examples are laser gyroscopes, fiber optic gyroscopes or vibration gyroscopes. In the measuring instrument mentioned, a symmetrical gyroscope rotates in a bearing, the "frame". Due to the conservation of angular momentum, the gyroscope has a high degree of inertia with regard to changes in position in space. If the rotational speed between the gyroscope and the frame is measured, it is called a gyroscope. ter. Gyroscopes are used as navigation instruments and for active attitude control, especially in aerospace. Attitude control of spacecraft such as satellites takes advantage of the fact that the entire system consisting of the spacecraft and the gyroscope retains its angular momentum and thus the attitude can be controlled by transferring angular momentum between the two.

angegeben.The “Angle Random Walk” or “ARW” describes the white noise at the output of a gyro, where white noise is noise with a constant power density spectrum in a certain frequency range and is often used to describe disturbances in an otherwise ideal model. The ARW is defined in $1°/\sqrt[2]{H}$

specified.

A “magnetometer” is a sensory device for measuring magnetic flux densities.

The term "laser" is used in this document for a device that generates laser beams. Laser beams are electromagnetic waves of high intensity in a very narrow frequency range - so-called monochromatic light - where the beam has a sharp focus and a long coherence length. Lasers have numerous applications in technology and are used in particular in distance measuring devices.

According to the invention, the gyroscope and the accelerometer are the same sensor. The method according to the invention uses two test masses that are suspended at a distance of a few millimeters, i.e. at a distance of less than 10 mm, preferably less than 5 mm and particularly preferably less than 2 mm. The movement of the common test mass (sum signal) represents the linear acceleration. The difference in the test mass movement (difference signal) represents the angular acceleration. The two measurements record exactly the same point in space, namely the center of mass of the two-mass system, whereby the previously explained disadvantages of the measuring methods known from the prior art with different mounting locations of test masses can be avoided.

- skaliert er mit der Quadratwurzel der kubierten Zeit kubiert - $\sqrt[2]{h^3}$

-. Dies führt unter Umständen jedoch zu zwei Vorteilen gegenüber dem Stand der Technik.The test masses can be suspended from a suspension device, for example a frame, in the rotating gyroscope. According to the invention, the Euler force is measured to determine the angular orientation of the test masses or the suspension device instead of the Coriolis force, as is known in the prior art. The Coriolis force measures the angular velocity, while the Euler force measures the angular acceleration. This means that the Euler force must be integrated twice over time to read out the angular orientation of the test masses or the suspension device, instead of simply being integrated, as is necessary when determining the angular orientation via the Coriolis force. However, this leads to an unfavorable change in the time scaling of the ARW. Instead of scaling with the square root of time - $\sqrt[2]{H}$

- it scales with the square root of the cubed time cubed - $\sqrt[2]{H^3}$

-. However, this may lead to two advantages over the state of the art.

The first advantage may be that no resonant structure is required, as is required for a Coriolis force measurement. This is important because the gain of the Coriolis force sensor is directly proportional to the resonance amplitude. Leakage of the acoustic energy from the resonant structure is inevitable and may interfere with nearby sensors, such as physically close linear accelerometers, especially when the gain is maximized. Since the acoustic energy is always electrically driven, it may also result in EMF (inductively coupled electromotive force), which is problematic for certain precision measurements, such as quantum measurements. One example where this is relevant is atom interferometry, which is extremely sensitive to external magnetic fields, but also has accelerometers and gyroscopes for stabilization.

bedeutet, dass es einen Teil der Zeit gibt, in dem sich das ARW kaum ändert, weil der Kubus einer sehr kleinen Zahl eine noch kleinere Zahl ist.The second advantage can be that the precision on short time scales is increased. This can be seen from the different scaling law for the ARW mentioned above. Scaling with $\sqrt[2]{H^3}$

means that there is a portion of time where the ARW changes little because the cube of a very small number is an even smaller number.

The signals from the acceleration sensors can be referenced to determine the position using a magnetometer, as is known to those skilled in the art.

In an advantageous embodiment of the method according to the invention, the ARW is changed by a filter algorithm. This can lead to advantages, especially for long time scales. A long time scale is understood here to mean times in the order of 1 second. On such a long time scale, the scaling according to the invention can become unfavorable. This can be compensated by the filter algorithm. The key is to keep the measurement noise as low as possible, so that after double integration the overall performance is better over a period of about 1 second. The filter algorithm can then compensate for the deterioration that occurs over longer periods. dreams occurs by referencing the acceleration and magnetometer measurements.

In a further advantageous embodiment of the method according to the invention, the motion of the first test mass and the second test mass is measured by an accelerometer device included in the gyroscope. The inclusion of the linear acceleration sensor together with the gyroscope means that the fusion algorithm is implicit in the design. The performance of the gyroscope can be improved on long time scales by the accelerometer, while on short time scales the performance can be improved by measuring the Euler force instead of the Coriolis force.

In a further advantageous embodiment of the method according to the invention, the movement of the first test mass and/or the second test mass is measured using cavity-enhanced interferometry. In order to measure the angular orientation by measuring the Euler force, the underlying precision of the measurement must be exceptional. Otherwise, the ARW drifts in milli- or microseconds. Even if this were compensated by a filter algorithm, this would not bring any significant advantage over the state of the art, at least not in terms of pure performance. Therefore, in this embodiment, cavity-enhanced interferometry is proposed as the measurement method, since this is currently the best method of precision displacement measurement.

According to a second aspect, the stated object is achieved by a device for measuring the direction of a linearly accelerated and/or rotationally accelerated object in a rotating reference system, wherein a first test mass and a second test mass are suspended at a distance from one another in a rotatable gyroscope and the device has a length measuring device, wherein the distance between the two test masses is less than 10 mm, preferably less than 5 mm and particularly preferably less than 2 mm, and wherein the device further has an angular acceleration measuring device with which an angular acceleration of the first test mass and the second test mass can be measured.

Let there be two test masses m ₁ and m ₂ , which are separated by a distance r. The two test masses experience a change in length ΔL ₁ and ΔL ₂ for a given linear acceleration a and/or rotational acceleration Ω about an axis perpendicular to the direction of motion.

Since a sudden change in the angular rate causes each test mass to move in opposite directions, the sum of their length changes for pure angular rate changes is zero, i.e. ΔL ₁ + ΔL ₂ = 0. However, their difference is proportional to the change in angular velocity, i.e. ΔL ₁ - ΔL ₂ ∝ Ω.

Conversely, an input acceleration causes both test masses to move in the same direction and therefore the difference in their length change is zero for pure linear acceleration, i.e. ΔL ₁ - ΔL ₂ = 0. However, their sum is in this case proportional to the linear input acceleration, i.e. ΔL ₁ + ΔL ₂ ∝ a.

Using these conditions, the method according to the invention described above can be used to determine the direction of a linearly accelerated and/or rotationally accelerated object in a rotating reference system.

In one embodiment of the device according to the invention, the length measuring device has a laser. Lasers have proven to be useful for precise length measurements.

In a further embodiment of the device according to the invention, the angular acceleration measuring device has a laser. Lasers have also proven to be useful for the precise measurement of angular accelerations.

In a further embodiment of the device according to the invention, both the length measuring device and the angular acceleration measuring device have a laser, whereby the length measuring device and the angular acceleration measuring device have a common laser. The common laser allows the device to be built particularly compactly, whereby at the same time no special precautions have to be taken for synchronizing several lasers.

The embodiments described above can be used individually or combined with each other as desired.

• 1 eine schematische Darstellung des Messprinzips für je eine Achse der linearen Beschleunigung und der Drehbeschleunigung,
• 2 eine schematische, perspektivische Darstellung einer Ausführungsform der erfindungsgemäßen Vorrichtung,
• 3 eine schematische, perspektivische Darstellung eines 6-Achsen-Sensors unter Verwendung eines kubischen Abstandshalters.

The invention will be explained in more detail below using exemplary embodiments with reference to the drawings.

• 1 a schematic representation of the measuring principle for one axis each of linear acceleration and rotational acceleration,
• 2 a schematic, perspective view of an embodiment of the device according to the invention,
• 3 a schematic perspective view of a 6-axis sensor using a cubic spacer.

wobei v die Laserfrequenz und Δv die optische Frequenzverschiebung des Hohlraums ist. Da eine plötzliche Änderung der Drehrate dazu führt, dass sich jede Testmasse m₁, m₂ in entgegengesetzte Richtungen bewegt, ist die Summe ihrer Längenänderung bei reinen Drehratenänderungen gleich Null: $$\mathrm{\Delta }{\text{L}}_1+\mathrm{\Delta }{\text{L}}_2=0$$

Ihre Differenz ist jedoch proportional zur Änderung der Winkelgeschwindigkeit: $$\mathrm{\Delta }{\text{L}}_1-\mathrm{\Delta }{\text{L}}_2\propto \mathrm{\Omega }.$$

Umgekehrt bewirkt eine Eingangsbeschleunigung, dass sich beide Prüfmassen m₁, m₂ in dieselbe Richtung bewegen und daher ist die Differenz ihrer Längenänderung bei reiner Linearbeschleunigung gleich Null: $$\mathrm{\Delta }{\text{L}}_1-\mathrm{\Delta }{\text{L}}_2=0$$

Ihre Summe ist jedoch in diesem Fall proportional zur linearen Eingangsbeschleunigung: $$\mathrm{\Delta }{\text{L}}_1+\mathrm{\Delta }{\text{L}}_2\propto \text{a}.$$

1 shows a schematic representation of the measuring principle for one axis each of the linear acceleration a and the rotational acceleration Ω. Two test masses, m ₁ , m ₂ are separated by a distance r. The two test masses m ₁ , m ₂ experience a change in length AL ₁ or AL ₂ for a given linear acceleration a and/or rotational acceleration Ω about an axis perpendicular to the plane of the drawing. A three-way split laser with a first laser beam 10, a second laser beam 11 and a third laser beam 12 is simultaneously in resonance with three optical cavities 20, 21, 22, whereby the optical cavities 20, 21, 22 are each on an axis with the first laser beam 10, the second laser beam 11 and the third laser beam 12. The first optical cavity 10 is formed by the first test mass m ₁ , while the second optical cavity 11 is formed by the second test mass m ₂ . The third optical cavity 12 represents a reference cavity. The first partial laser beam 10 intersects the first optical cavity 20, while the second partial laser beam 11 intersects the second optical cavity 21. The third partial laser beam 12 intersects the third optical cavity 22, which serves as a reference. The third optical cavity 22 is optional. If a third optical cavity is provided, the laser frequency noise common to all optical cavities 20, 21, 22 can be cancelled out if the same laser source is used. Independent optical frequency tuning for each optical cavity 20, 21, 22 can be achieved, for example, with three acoustic-optical modulators, three electro-optical modulators or three phase-locked lasers. Each optical cavity 20, 21, 22 is resonant at a different optical frequency depending on its length L ₁ , L ₂ , L ₃ , where the cavity lengths L ₁ , L ₂ , L ₃ are nominally the same for all three optical cavities 20, 21, 22 until they are disturbed by an acceleration or a sudden change in the rotation rate. The readout is made as a frequency shift of the optical cavity resonance and is directly related to the change in the length of the cavity: $$\mathrm{\Delta }\text{L}/\text{L}\propto \mathrm{\Delta }\text{v}/\text{v}$$

where v is the laser frequency and Δv is the optical frequency shift of the cavity. Since a sudden change in the rotation rate causes each test mass m ₁ , m ₂ to move in opposite directions, the sum of their length changes for pure rotation rate changes is zero: $$\mathrm{\Delta }{\text{L}}_1+\mathrm{\Delta }{\text{L}}_2=0$$

However, their difference is proportional to the change in angular velocity: $$\mathrm{\Delta }{\text{L}}_1-\mathrm{\Delta }{\text{L}}_2\propto \mathrm{\Omega }.$$

Conversely, an input acceleration causes both test masses m ₁ , m ₂ to move in the same direction and therefore the difference in their length change is zero for pure linear acceleration: $$\mathrm{\Delta }{\text{L}}_1-\mathrm{\Delta }{\text{L}}_2=0$$

However, in this case their sum is proportional to the linear input acceleration: $$\mathrm{\Delta }{\text{L}}_1+\mathrm{\Delta }{\text{L}}_2\propto \text{a}.$$

2 shows a schematic representation of an embodiment of the device according to the invention. An optical cavity spacer block 25 with three holes 26 for receiving the three optical cavities 20, 21, 22 is flanked on its first end face 26 by a first mirror substrate 30. On its second end face 27, the optical cavity spacer block 25 is flanked by a second mirror substrate 40. The term mirror substrate is understood here to mean a substrate on which flat and/or concave and/or convex mirrors are arranged. The second mirror substrate 40 has three curved mirrors 41, 42, 43, one for each optical cavity 20, 21, 22. The curved mirrors 41, 42, 43 enable stable optical resonator modes for each optical field in each optical cavity 20, 21, 22. On the first mirror substrate 30 there are a first mechanical oscillator 31 and a second mechanical oscillator 32. The first mechanical oscillator 31 has at its center a test mass m ₁ which is attached to the first mirror substrate 30 with six springs 35, and the second mechanical oscillator 32 has at its center the second test mass m ₂ which is also attached to the first mirror substrate 30 with six springs 35. The six springs 35 are divided into three springs 35 on the front and three springs 35 on the back of the first mirror substrate 30, whereby the springs 35 on the back of the first mirror substrate are not all visible in the perspective shown. For reasons of clarity, the springs 35 are only designated for the first mechanical oscillator 31. The number of springs 35 can vary depending on the design. An empty part of the first mirror substrate 30 is used for the reference cavity 22. Stable optical resonators are possible with concave and/or convex mirror combinations.

3 shows a schematic, perspective view of a 6-axis sensor using a cubic cavity spacer block 25. A cubic cavity spacer block 25 with orthogonal facets forms a coordinate frame. The device comprises three first mirror substrates 30, each with a first mechanical oscillator 31 and a second mechanical oscillator 32, and correspondingly three second mirror substrates 40, each with a first, second and third curved mirror 41, 42, 43. The linear scanning directions for acceleration are along the normal vector of the cube faces. The direction of rotation of the mechanical oscillators 31, 32 on each side of the cube is important for determining the axis of rotation of the gyroscope. The rotation vector sensed by each test mass pair m ₁ , m ₂ is represented in the figure by a circular arrow winding around the axis of rotation. This rotation axis lies in the mirror plane of the test masses m ₁ , m ₂ . The linear acceleration axis is orthogonal to the rotation axis.

The embodiments shown here are only examples of the present invention and should therefore not be understood as limiting. Alternative embodiments considered by those skilled in the art are equally included within the scope of the present invention.

List of reference symbols used

a

linear acceleration

IL

Input Laser

L1

Length of the first optical cavity

L2

Length of the second optical cavity

L3

Length of the third optical cavity

m1

first test mass

m2

second test mass

r

Distance

v

Laser frequency

Δv

optical frequency shift of the cavity

ΔL1

Length change of the first test mass

ΔL2

Length change of the second test mass

Ω

Rotational acceleration

10

first partial laser beam

11

second partial laser beam

12

third partial laser beam

20

first optical cavity

21

second optical cavity

22

third optical cavity, reference cavity

25

Cavity spacer block

26

drilling

30

first mirror substrate

31

first mechanical oscillator

32

second mechanical oscillator

35

Feather

40

second mirror substrate

41

first curved mirror

42

second curved mirror

43

third curved mirror

50

third mirror substrate

Claims (8)

Method for measuring the direction of a linearly accelerated and/or rotationally accelerated object in a rotating reference system, characterized in that the movement of a first test mass (m ₁ ) and a second test mass (m ₂ ), which are suspended at a distance from one another in a rotating gyroscope serving as a reference system, is recorded as a sum signal, wherein the distance between the two test masses (m ₁ , m ₂ ) is less than 10 mm, preferably less than 5 mm and particularly preferably less than 2 mm, and in addition a difference between the movement of the first test mass (m ₁ ) and the movement of the second test mass (m ₂ ) is measured. Procedure according to Claim 1 , characterized in that the ARW, in particular for long time scales, is modified by a filter algorithm. Procedure according to Claim 1 or 2 , characterized in that the movement of the first test mass (m ₁ ) and the second test mass (m ₂ ) are measured by an acceleration measuring device included in the gyroscope. Method according to one of the preceding claims, characterized in that the movement of the first test mass (m ₁ ) and/or the second test mass (m ₂ ) is measured by means of cavity-enhanced interferometry. Device for measuring the direction of a linearly accelerated and/or rotationally accelerated object in a rotating reference system, in particular for carrying out the method according to one of the preceding claims, characterized in that a first test mass (m ₁ ) and a second test mass (m ₂ ) are suspended at a distance from one another in a rotatable gyroscope and the device has a length measuring device, wherein the distance between the two test masses (m ₁ , (m ₂ ) is less than 10 mm, preferably less than 5 mm and particularly preferably less than 2 mm, and wherein the device further has an angular acceleration measuring device with which an angular acceleration of the first test mass (m ₁ ) and the second test mass (m ₂ ) can be measured. Device according to Claim 5 , characterized in that the length measuring device comprises a laser. Device according to one of the Claims 5 or 6 , characterized in that the angular acceleration measuring device comprises a laser. Device according to Claim 5 , characterized in that the length measuring device comprises a laser and the angular acceleration measuring device comprises a laser, wherein the length measuring device and the angular acceleration measuring device comprise a common laser.

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