DE102019112148A1 - Device and method for damping or generating micro-vibrations - Google Patents

Abstract

The invention relates to a device for damping and generating micro-vibrations. The invention also relates to a method for operating the device. An inventive device for generating micro-vibrations on all six degrees of freedom is characterized in that a plurality of electromagnetically drivable exciter masses is arranged in a tetrahedral structure, the exciter masses being drivable independently of one another. This means that all three axes of a Cartesian coordinate system can be assigned forces and moments. The forces can be generated without torque and the moments can be generated without force, whereby all three axes of a Cartesian coordinate system can be controlled independently of one another. The tetrahedron arrangement also makes it possible to generate moment-free forces and force-free moments at the same time, to produce a dynamic imbalance with the smallest possible number of actuators. The structure thus offers the possibility of generating or damping a micro-vibration on all six degrees of freedom.

Description

The invention relates to a device for damping and generating micro-vibrations. The invention also relates to a method for operating the device.

So-called micro-vibrations play an increasingly important role in the development and construction of current spacecraft and satellites. Microvibrations are increasingly becoming the limiting factor of a highly precise position control and thus also a highly precise alignment of the spacecraft or satellites and / or of devices such as telescopes that are operatively connected to spacecraft or satellites. An example here are the optical telescope satellites such as the Hubble. The Hubble Space Telescope was created primarily to circumvent the limitations of the Earth's atmosphere when observing objects and phenomena in the universe. The molecules of the earth's atmosphere limit the resolving power of telescopes on the earth's surface, and different spectral ranges are blocked. However, if such a telescope is not aligned very smoothly, the recorded image will “smear” in simple terms. Such alignment errors can be caused by micro-vibrations.

The development of satellites is currently moving in two directions. On the one hand, ever larger and heavier satellites are being developed (e.g. James Webb Space Telescope), which can get micro-vibrations under control solely through their large mass inertia. On the other hand, the satellites are getting smaller and smaller (e.g. CubeSats, 1 kg). The smaller the satellite, the more difficult and / or time-consuming it is to get micro-vibrations under control, since every disturbance has a relatively strong effect here.

Microvibrations are characterized by very low acceleration levels, which are transmitted and / or even intensified through structural components. The micro-vibrations are typically caused by moving mechanical units such as e.g. Reaction wheels, liquid pumps, louvers (blinds), stepper motors, etc ..

There is a lack of effective mechanisms and devices for damping micro-vibrations, in particular those which are also suitable for use on small satellites or spacecraft.

In addition to micro-vibration damping, the defined generation of micro-vibrations is also becoming increasingly important. It is used to a large extent to carry out structural verification tests to prove that a certain structure has sufficient damping properties.

There are currently two different approaches to addressing microvibration. On the one hand via a purely passive spring-mass-damper system and on the other hand, for example, via active piezo actuators.

The main disadvantage of a purely passive spring-mass damper system is that it cannot be adjusted after completion. Adaptation is no longer possible, especially if a satellite is already in orbit. In addition, adaptations in the laboratory structure are only possible to a limited extent, since practically the entire structure has to be replaced. Ultimately, it is therefore very difficult to react to unknown disturbances and to adapt the spring-mass-damper system.

Especially the problem of adaptation can be solved with piezo actuators. These actuators can be adapted relatively easily and thus generate corresponding damping or excitations. Their main disadvantage, however, is the very low amplitude that can be generated or damped with them.

• Unter einem Raumfahrzeug wird in dieser Schrift ein Fahrzeug verstanden, das der Fortbewegung im Weltraum dient. Ein Raumfahrzeug weist einen eigenen Antrieb auf.

The following terms are explained:

• In this document, a spacecraft is understood to mean a vehicle that is used for locomotion in space. A spacecraft has its own drive.

In this document, a satellite is generally understood to mean an artificial spacecraft which orbits a celestial body in an elliptical or circular orbit, the orbit, for the fulfillment of scientific, commercial or military purposes. A satellite can have its own propulsion system, this being primarily designed to correct the attitude and position of the satellite. A special satellite is an optical telescope satellite. This is a satellite that carries an optical telescope and is used to observe celestial bodies such as planets or comets.

The universe or synonymously the universe is the totality of space, time and all matter and energy in it. The observable universe, however, is limited to the found arrangement of all matter and energy, starting with the elementary particles up to the large-scale structures such as galaxies and galaxy clusters.

Vibrations are periodic, mostly medium to high frequency and low amplitude (mechanical) vibrations of materials and bodies that are either elastic themselves or are made of elastically connected items or building blocks exist, understood. Accordingly, micro-vibrations are vibrations with extremely small amplitudes and / or accelerations.

In this document, the term telescope is generally understood to mean an instrument that collects and bundles electromagnetic waves in order to be able to observe distant objects. Depending on the frequency spectrum or wavelength range of the electromagnetic waves, a distinction is made between, for example, gamma telescopes that receive gamma radiation from space, x-ray telescopes that receive x-ray radiation from space, optical telescopes, such as telescopes and mirror telescopes, with which objects that are far away are viewed magnified or with high resolution, infrared telescopes with which infrared radiation emitted by astronomical objects can be observed, and radio telescopes for receiving and measuring the radio frequency radiation coming from space or special celestial objects.

In optics, resolving power refers to the differentiation of fine structures, for example the minimum distance that two point-like objects must have in order to be able to perceive them as separate objects. It can be quantified by specifying an angular distance (angular resolution) or by specifying the distance between structures that are barely separable.

The term position control or synonymously position control denotes the control of the position of a system, for example a telescope that is operatively connected to a spacecraft or satellite.

In this document, a structural component is to be understood as a load-bearing, three-dimensional component.

A spring-mass-damper system consists of masses, mechanical springs and parallel damping elements. The system can store potential and kinetic energy. Mass-spring-damping systems are primarily intended to reduce the transmission of vibrations and structure-borne noise. The elastic elements (springs) ensure a vibrational decoupling of the masses. The mass and spring dynamics must be coordinated with one another. The spring has a spring constant, a rest length, and a decay constant. If the spring is in the rest position, the system is also in the starting position. If a mass is moved, there is potential energy on the spring, which is minimized by shifting the other mass points. The attenuator ensures that the system does not continue to oscillate after the deformation, but rather finds its way back to its rest position. A weak, subcritical damping leads to oscillating decay, while critical or supercritical damping leads to creeping decay.

In this document, an (active) piezo actuator is to be understood as an actuator, that is to say a drive unit, which converts an electrical signal into mechanical movements or changes in physical quantities such as pressure or temperature and thus actively intervenes in a controlled process the mechanical movement by taking advantage of the piezoelectric effect, ie by applying an electrical voltage to a solid body.

The object of the invention is to provide a device with which microvibrations can be actively and effectively damped in a targeted manner on all six degrees of freedom and actively generated, for example, for test purposes, the number of actuators required being minimized. Another object of the invention is to provide a method for operating the device.

The first object of the invention is achieved with a device according to independent claim 1. Advantageous further developments of the device emerge from claims 2 to 6. The second object of the invention is achieved with a method according to the independent claim 7. Advantageous developments of the method result from claims 8 to 14.

An inventive device for generating micro-vibrations on all six degrees of freedom is characterized in that a plurality of electromagnetically drivable exciter masses is arranged in a tetrahedral structure, the exciter masses being drivable independently of one another. This means that all three axes of a Cartesian coordinate system can be assigned forces and moments. The forces can be generated without torque and the moments can be generated without force, whereby all three axes of the Cartesian coordinate system can be controlled independently of one another. The tetrahedral arrangement allows the generation of moment-free forces and force-free moments as well as static or dynamic imbalances with the smallest possible number of actuators. The structure thus offers the possibility of generating or damping a micro-vibration on all six degrees of freedom. The actuators are, for example, linear actuators.

An excitation mass is understood to mean a mass that is able to excite a system with which the mass is actively connected, for example to vibrate. The system can be, for example, a telescope that is operatively connected to a spacecraft or satellite, including its movable mounting. The excitation mass is thus an actuator. According to the invention, the excitation mass can be driven electromagnetically. An electromagnetic drive is understood to mean any drive in which electrical energy is converted into mechanical energy with the aid of the electromagnetic principle.

A rigid body can execute six independent movements in three-dimensional space, namely moving in three independent directions (translation) and turning around three independent axes (rotation). In other words, a rigid body has six degrees of freedom in three-dimensional space.

An arrangement of excitation masses in a tetrahedral structure is present when the excitation masses are arranged in such a way that they lie on the edges or surfaces of an imaginary general tetrahedron, that is to say a body with four triangular side surfaces.

In general, it should be noted that in the context of this document, the indefinite numerals “one”, “two” etc. should not be understood as “exactly one”, “exactly two” etc., but normally as an indefinite article. A statement of the type "one ...", "two ..." etc. is therefore to be understood as "at least one ...", "at least two ..." etc., unless it is clear from the respective context that only "exactly one", "exactly two" etc. are meant.

In an advantageous embodiment, the axes of the excitation masses are arranged on the surfaces of the imaginary tetrahedron. As a result, the tetrahedral structure can be implemented particularly easily.

In a further advantageous embodiment, the axes of the excitation masses are arranged along the edges of the imaginary tetrahedron.

Alternatively, the axes of the excitation masses can also be arranged in such a way that they point orthogonally through the surface centers of the imaginary tetrahedron.

In a further advantageous embodiment, four electromagnetically drivable excitation masses are arranged in the tetrahedral structure. With four excitation masses, it is possible to generate forces, moments and imbalances in all six degrees of freedom with a minimum number of excitation masses, although these cannot all be generated at the same time.

In an alternative advantageous embodiment, at least six electromagnetically drivable excitation masses are arranged in the tetrahedral structure. With six electromagnetically drivable excitation masses, this arrangement allows micro-vibrations to be generated on all six degrees of freedom. At the same time, any number of forces, moments and static and dynamic imbalances can be generated, especially if a plurality of the exciter masses arranged on all three axes of a Cartesian coordinate system are electromagnetically driven independently of one another.

The acceleration of a stored mass, here the exciter mass, in one direction generates a counterforce of the same amount on the system. The force creates a torque around the center of the tetrahedron, proportional to the distance to it. The acceleration of several masses around this center point allows torques or forces to be counteracted in order to generate pure forces or moments depending on the application. It is possible, depending on the control, to simultaneously generate an imbalance that can be static or dynamic depending on the application.

In an advantageous embodiment of the method, the electromagnetically drivable excitation masses are controlled in such a way that torque-free forces are generated.

In a further advantageous embodiment of the method, the electromagnetically drivable excitation masses are controlled in such a way that force-free moments are generated.

It has proven to be advantageous if second micro-vibrations are generated by controlling the electromagnetically drivable excitation masses.

In a particularly advantageous embodiment of the method, first microvibrations are recorded on a system and, via the control of the electromagnetic drive of the excitation masses, second microvibrations are generated, which counteract the recorded first microvibrations. In other words, the first micro-vibrations can be dampened by generating corresponding second micro-vibrations. A corresponding control of the electromagnetic drive of the excitation masses can generate second microvibrations which even completely compensate for the first microvibrations. The system can be, for example, a telescope that is operatively connected to a spacecraft or satellite, including its movable mounting.

In a further advantageous embodiment of the method, an imbalance is generated in a system by activating the electromagnetically drivable exciter masses. Here too, the system can be, for example, a telescope that is operatively connected to a spacecraft or a satellite, together with its movable mounting.

The electromagnetically drivable excitation masses can be controlled via amplitude modulation. Alternatively or cumulatively, the electromagnetically drivable excitation masses can also be controlled via frequency modulation.

Due to the tetrahedral arrangement of the electromagnetically drivable excitation masses, force-free moments and moment-free forces as well as static and dynamic imbalances can be generated with the smallest possible number of actuators. The amplitude of the excitation can be freely selected via regulators within the actuator limits, whereby the unlimited scalability of the actuator only allows the actuator mass to increase linearly. The size of the electromagnetic actuators can be adjusted and the form of excitation (sine, tilting oscillation, etc.) can be adjusted by a controller. The generation of force-free moments is just as possible as the generation of moment-free forces on all three axes of a Cartesian coordinate system. It is also possible to generate a static as well as a dynamic imbalance.

The structure of the electromagnetic actuators can correspond to that of a low-pass filter, so that low frequencies can be attenuated without amplitude modulation, which can be relevant for longer exposure times of optical instruments, for example optical telescopes on spacecraft and satellites. The cut-off frequency can be influenced by the coil structure. Amplitude and / or frequency modulation is possible. The advantage of the electromagnetic contact and frictionless drive consists of in that the drive is mostly noisy and the eddy currents that arise dampen possible vibrations.

It should be expressly pointed out that all numerical values given should not be understood as sharp limits, but rather should be able to be exceeded or fallen below on an engineering scale without departing from the aspect of the invention described.

Further advantages, special features and expedient developments of the invention emerge from the subclaims and the following illustration of preferred exemplary embodiments on the basis of the figures.

• 1a eine schematische Darstellung einer Anordnung von sechs elektromagnetisch antreibbaren Erregermassen in einer Vorderansicht,
• 1b eine schematische Darstellung einer Anordnung von sechs elektromagnetisch antreibbaren Erregermassen in einer Draufsicht,
• 1c eine schematische Darstellung einer Anordnung von sechs elektromagnetisch antreibbaren Erregermassen in einer Seitenansicht von links,
• Fig. Id eine schematische Darstellung einer Anordnung von sechs elektromagnetisch antreibbaren Erregermassen in einer isometrischen Ansicht,
• 2a eine schematische Darstellung einer Anordnung von vier elektromagnetisch antreibbaren Erregermassen in einer Vorderansicht,
• 2b eine schematische Darstellung einer Anordnung von vier elektromagnetisch antreibbaren Erregermassen in einer Draufsicht,
• 2c eine schematische Darstellung einer Anordnung von vier elektromagnetisch antreibbaren Erregermassen in einer Seitenansicht von links,
• 2d eine schematische Darstellung einer Anordnung von vier elektromagnetisch antreibbaren Erregermassen in einer isometrischen Ansicht,

Show it:

• 1a a schematic representation of an arrangement of six electromagnetically drivable excitation masses in a front view,
• 1b a schematic representation of an arrangement of six electromagnetically drivable excitation masses in a plan view,
• 1c a schematic representation of an arrangement of six electromagnetically drivable excitation masses in a side view from the left,
• Fig. Id a schematic representation of an arrangement of six electromagnetically drivable excitation masses in an isometric view,
• 2a a schematic representation of an arrangement of four electromagnetically drivable excitation masses in a front view,
• 2 B a schematic representation of an arrangement of four electromagnetically drivable excitation masses in a plan view,
• 2c a schematic representation of an arrangement of four electromagnetically drivable excitation masses in a side view from the left,
• 2d a schematic representation of an arrangement of four electromagnetically drivable excitation masses in an isometric view,

1 shows a schematic representation of an arrangement of six electromagnetically drivable excitation masses 3 in a front view ( 1a) , a top view ( 1b) , a side view from the left ( 1c ) and an isometric view ( 1d ). The electromagnetically drivable excitation masses 3 are massed linear actuators that run along the edges 2 an imaginary tetrahedron are arranged. This arrangement allows micro-vibrations to be generated on all six degrees of freedom. At the same time any number of forces, moments as well as static and dynamic imbalances can be generated.

2 shows a schematic representation of an arrangement of four electromagnetically drivable excitation masses 3 in a front view ( 2a) , a top view ( 2 B) , a side view from the left ( 2c ) and an isometric view ( 2d ). The electromagnetically drivable excitation masses 3 are mass linear actuators, which are mounted on the corners of an imaginary tetrahedron, whereby the orientation can be freely selected. This second, somewhat simplified, arrangement allows forces, moments and unbalances to be generated, although these cannot all be generated at the same time.

The embodiments shown here are only examples and should therefore not be understood as restrictive. Alternative embodiments contemplated by those skilled in the art are equally encompassed by the scope of the present invention.

List of reference symbols

1

tetrahedral structure

2

Edge of the imaginary tetrahedron

3

Excitation mass

Claims (14)

Device for generating micro-vibrations on all six degrees of freedom, characterized in that a plurality of electromagnetically drivable exciter masses (3) is arranged in a tetrahedral structure (1), the exciter masses (3) being drivable independently of one another. Device according to Claim 1 , characterized in that the axes of the excitation masses (3) are arranged on the surfaces of the imaginary tetrahedron. Device according to Claim 2 , characterized in that the axes of the excitation masses (3) are arranged along the edges (2) of the imaginary tetrahedron. Device according to Claim 2 , characterized in that the axes of the excitation masses (3) are arranged in such a way that they point orthogonally through the surface centers of the imaginary tetrahedron. Device according to one of the preceding claims, characterized in that four electromagnetically drivable excitation masses (3) are arranged in the tetrahedral structure (1). Device according to one of the preceding claims, characterized in that at least six electromagnetically drivable excitation masses (3) are arranged in the tetrahedral structure (1). Method for generating microvibrations, characterized in that a plurality of exciter masses (3) arranged on all three axes of a Cartesian coordinate system are electromagnetically driven independently of one another. Procedure according to Claim 7 , characterized in that the electromagnetically drivable excitation masses (3) are controlled so that torque-free forces are generated. Method according to one of the Claims 7 or 8th , characterized in that the electromagnetically drivable excitation masses (3) are controlled in such a way that force-free moments are generated. Method according to one of the Claims 7 to 9 , characterized in that the control of the electromagnetic drive of the excitation masses (3) generates second micro-vibrations. Procedure according to Claim 10 , characterized in that first micro-vibrations are recorded on a system and second micro-vibrations are generated by controlling the electromagnetically drivable exciter masses (3), which counteract the recorded first micro-vibrations. Method according to one of the Claims 7 to 11 , characterized in that an imbalance is generated in a system by controlling the electromagnetically drivable excitation masses (3). Method according to one of the Claims 7 to 12 , characterized in that the electromagnetically drivable excitation masses (3) are controlled via amplitude modulation. Method according to one of the Claims 7 to 13 , characterized in that the electromagnetically drivable excitation masses (3) are controlled via frequency modulation.

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