DD269451A1

DD269451A1 - LINEAR ACCELERATION KNIFE

Info

Publication number: DD269451A1
Application number: DD31314688A
Authority: DD
Inventors: Michael Naumann; Olaf Hein
Original assignee: Akad Wissenschaften Ddr
Priority date: 1988-02-24
Filing date: 1988-02-24
Publication date: 1989-06-28

Abstract

Die Erfindung betrifft einen linearen Beschleunigungsmesser, der die notwendige Stabilitaet und Empfindlichkeit zur Messung kleiner Beschleunigungen in vertikaler Richtung aufweist und somit beispielsweise in Schweregradiometern bzw. in der Traegheitsnavigation eingesetzt werden kann. Die wesentlichen Merkmale des Beschleunigungsmessers sind die Verwendung der als Tauchanker ausgefuehrten Testmasse innerhalb eines Elektromagneten, der durch eine spezielle konstruktive Gestaltung sowohl des Tauchankers als auch des Ankergegenstueckes die Funktion einer mechanischen Feder uebernimmt. Die Testmasse ist mittels Membranfedern im Elektromagneten gefuehrt, die eine hohe radiale Steifigkeit und eine reibungsarme axiale Bewegung realisieren. Die Bewegung der Testmasse wird durch ein kapazitives Sensorelement detektiert und ueber eine elektronische Regelung durch die Aenderung des Spulenstromes des Elektromagneten rueckgefuehrt. Die Regelgroesse verkoerpert den Messwert, der der wirkenden Beschleunigung proportional ist. FigurThe invention relates to a linear accelerometer, which has the necessary stability and sensitivity for measuring small accelerations in the vertical direction and thus can be used, for example, in gravity gauges or in the context of navigation. The essential features of the accelerometer are the use of the designed as a plunger anchor test mass within an electromagnet, which assumes the function of a mechanical spring by a special structural design of both the plunger armature and the armature Gegenstueckes. The test mass is guided by means of diaphragm springs in the electromagnet, which realize a high radial rigidity and a low-friction axial movement. The movement of the test mass is detected by a capacitive sensor element and returned via an electronic control by the change of the coil current of the electromagnet. The control quantity corroborates the measured value, which is proportional to the acting acceleration. figure

Description

AusfOhrungsbelsplel Fig. 1: Basic structure of the acceleration wet Flg. 2: Side view of the accelerometer - (section) Fig. 3: diaphragm spring variants Flg.4: Design of the plunger anchor (test mass 2) and the armature counterpart 9 and the bottom 10 of the electromagnet. 1 Fig. 5: Qualitative characteristic of the electromagnet due to the Ankerjegenstück- and Tauchankergestaltung

Der Beschleunigungsmessers besteht aus einem mehrteiligen Gehäuse 3 (Flg. 1,2). Innerhalb dieses Gehäuses 3 befindet ülch die als Tauchanker im Elektromagneten 1 geführten 100 g schwere Testmasse 2, die mittels der kreisrunden Membranfedern 4; 5 am Gehäuse 3 gelagert ist. Die ebenen, durchbrochenen Membranfedern 4; 5 (Fig. 3) bestehen aus 0,01 mm starker Messing-Folie mit einem Außendurchmesser von 50mm. Sie sind so gestaltet, daß sie eine reibungsarme axiale Bewegung der Testmasse 2 gewährleisten, aber in radialer Richtung eine hohe Steifigkeit aufweisen. Von den dargestellten Membranfedervarianten wird gleichzeitig immer nur eine verwendet.The accelerometer consists of a multi-part housing 3 (Flg. 1,2). Within this housing 3 is ülch the guided as a dip anchor in the electromagnet 1 100 g test mass 2, by means of the circular diaphragm springs 4; 5 is mounted on the housing 3. The flat, open-ended diaphragm springs 4; 5 (Fig. 3) are made of 0.01 mm thick brass foil with an outside diameter of 50 mm. They are designed so that they ensure a low-friction axial movement of the test mass 2, but in the radial direction have a high rigidity. Of the diaphragm spring variants shown, only one is used at a time.

Der Elektromagnet 1 übernimmt die Funktion einer Feder, so daß eine Gleichgewichtslage der Testmasse 2 relativ zum Gehäuse 3 entsteht. Die Gleichgewichtslage entspricht der unausgeienkten Lage der Membranfedern 4; 5. Um die Funktion einer mechanischen Feder erfüllen zu können, muß der Elektromagnet 1 eine dementsprechende Kennlinie besitzen. Dies wird durch die Gestaltung des Tauchankers 2 und des Ankergegenstückes 9 (Flg.4,5) erreicht. Zu beachten ist dabei, daß beim Tauchanker, der der Testmasse 2 entspricht, nur der mittlere kurze Zylinder 12 aus ferromagnetischem Material besteht. Der Elektromagnet 1 besteht vorzugsweise entweder vollständig aus einer Spule, die 100% der Gewichtskraft der Testmasse 2 trägt, oder aus einem Permanentmagneten und einer kleinen Spule, wobei die Spule dann nur etwa 5% der erforderlichen Kraft für die Gleichgewichtslage aufbringt.The electromagnet 1 assumes the function of a spring, so that an equilibrium position of the test mass 2 is formed relative to the housing 3. The equilibrium position corresponds to the unexposed position of the diaphragm springs 4; 5. In order to fulfill the function of a mechanical spring, the electromagnet 1 must have a corresponding characteristic. This is achieved by the design of the plunger anchor 2 and the anchor counterpart 9 (Flg.4,5). It should be noted that the plunger armature corresponding to the test mass 2, only the average short cylinder 12 is made of ferromagnetic material. The electromagnet 1 preferably consists either entirely of a coil which carries 100% of the weight of the test mass 2, or of a permanent magnet and a small coil, the coil then applying only about 5% of the required force for the equilibrium position.

An der Test-nasse 2 befestigt ist die Mittelplatte des kapazitiven Sensorelementes 6, das der Meßwertaufnahme dient. Es besteht aus einem Differential- und einem Auskoppelkondensator mit einer wirksamen Fläche von etwa 1UOO mm². Es arbeitet nach dem Trägerfrequenzverfahren, wobei die Trägerfrequenz durch einen amplitudenstabilen Generator erzeugt wird, der Teil der Elektronik 7 ist. Die Trägerfrequenz beträgt 1OkHz.Attached to the test wet 2 is the center plate of the capacitive sensor element 6, which serves to record the measured value. It consists of a differential and a decoupling capacitor with an effective area of about 1UOO mm ² . It operates according to the carrier frequency method, wherein the carrier frequency is generated by an amplitude-stable generator, which is part of the electronics 7. The carrier frequency is 10 kHz.

Bei einer auf den Beschleunigungsmesser parallel zu seiner Symmetrieachse wirkenden vertikalen Beschleunigung wird die Testmasse 2 aus ihrer Gleichgewichtslage ausgelenkt. Diese Bewegung wird vom kapazitiven Sensorelement detektiert, so daß in der nachfolgenden Elektronik 7 ein Korrektur- bzw. Rückführsignal entsteht. Dieses stellt einerseits das der einwirkenden Beschleunigung proportionale Meßsignal dar, das in der Anzeige 8 abgebildet wird, andererseits aber gleichzeitig die Stellgröße für den Elektromagneten 1, wodurch die Testmasse 2 wieder in die Gleichgewichtslage gelangt.With a vertical acceleration acting on the accelerometer parallel to its axis of symmetry, the test mass 2 is deflected out of its equilibrium position. This movement is detected by the capacitive sensor element, so that a correction or feedback signal is produced in the subsequent electronics 7. On the one hand, this represents the measurement signal which is proportional to the applied acceleration and which is displayed in the display 8, but on the other hand simultaneously the manipulated variable for the electromagnet 1, whereby the test mass 2 returns to the equilibrium position.

Das Gehäuse 3 wird bei der Realisierung des Beschleunigungsmessers thermosUvtisiert. Dazu wird in Abhängigkeit von der Erwärmung des Elektromagneten 1 das Gehäuse 3 durch eine Kühlschlange mit Kühlflüssigkeit (nicht dargestellt) abgekühlt.The housing 3 is thermosUvtisiert in the realization of the accelerometer. For this purpose, as a function of the heating of the electromagnet 1, the housing 3 is cooled by a cooling coil with cooling liquid (not shown).

Claims

Linear accelerometer with electrostatic data acquisition, electromagnetic feedback and mechanical guidance dec test mass, characterized in that the test mass acts as a dip anchor within an electromagnet, and the test mass or the Tauchanker within the electromagnet by two circular, flat, provided with special openings, perpendicular to Is guided measuring axis lying diaphragm springs, and a capacitive sensor element, the center plate is attached to the test mass, the movements of the test mass detected and the electromagnet the test mass returns to the equilibrium position, wherein the plunger of non-ferromagnetic material and a ferromagnetic center ring is slightly into the angephaste anchor counterpart of the iron core of the electromagnet immersed.

For this 4 pages drawings

field of use

The invention relates to a linear electrostatic accelerometer with electromagnetic feedback and a special mechanical suspension, which achieves the necessary stability and sensitivity for measuring small vertical accelerations, for example in Schwierigkeitsgradiometer or in the inertial navigation.

Characteristic of the known technical solutions

Some solutions for electrostatic accelerometers with electromagnetic feedback are known in the literature (DE 2833915, DE 2164321, DE 2759499, DE 2759500, DE 2840698, DE 2840700, DE 2840652, US 3438265, US 3438266, US 4141765, US 4145929, SU 670896) , Those with a pendulum-like design of the test mass of the accelerometer, which simultaneously embodies the center plate of a capacitive sensor, are not linear accelerometers and thus differ from the solution according to the invention. The accelerometers of US 4144765, US 4145929, DE 2840700 represent solutions, br. which linearly movable test masses are used. These are made by specially developed suspensions, consisting of membranes, linear to the housing. A disadvantage of these accelerometers, however, is that the suspensions are designed and arranged such that they allow tilting of the test mass in the deflected state because of then no longer sufficient rigidity of the suspensions. Furthermore, the electromagnet, which assumes the function of a mechanical spring, does not work with a linear characteristic curve corresponding to the mechanical spring, resulting in systematic measurement errors.
The accelerometer according to the invention avoids the disadvantages of the known technical solutions.

Object of the invention

The aim of the invention is to propose an accelerometer, which has the necessary stability and sensitivity for the measurement of small accelerations in the vertical direction.

Explanation of the essence of the invention

The invention has for its object to provide a linear electrostatic accelerometer with electromagnetic feedback and mechanical suspension of the test mass for the measurement of small accelerations in the vertical direction.

The accelerometer according to the invention (FIG. 1) consists of a test mass guided as a dip anchor in an electromagnet 1

2. The electromagnet 1 assumes the function of a spring, so that an equilibrium position of the test mass 2 is formed relative to the electromagnet 1 and thus to the housing 3. The test mass 2 is guided through the two k-round membrane springs 4; 5, whose undeflected position coincides with the equilibrium position of the test mass 2. The diaphragm springs 4; 5 ensure a smooth axial movement of the test mass 2 with high radial stiffness, without tilting, cross misalignment and torsions occur. Attached to the test mass 2 is the center plate of the capacitive sensor element 6, which serves to record the measured value. It works according to the carrier frequency method. In the case of a vertical acceleration acting on the accelerometer, which occurs parallel to its axis of symmetry when the accelerometer is functioning, the test mass 2 is deflected out of its equilibrium position. This movement is detected by the capacitive sensor element 6, whereby a correction or feedback signal is produced in the subsequent electronics 7. On the one hand, this represents the measurement signal which is proportional to the applied acceleration and which is displayed in the display 8, but on the other hand simultaneously the manipulated variable for the electromagnet 1, whereby the test mass 2 returns to the equilibrium position.