U.S. patent application number 12/616100 was filed with the patent office on 2010-05-06 for modular interface for damping mechanical vibrations.
This patent application is currently assigned to Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V.. Invention is credited to Holger Hanselka, Sven Herold, Michael Matthias, Tobias Melz.
Application Number | 20100109219 12/616100 |
Document ID | / |
Family ID | 34105470 |
Filed Date | 2010-05-06 |
United States Patent
Application |
20100109219 |
Kind Code |
A1 |
Melz; Tobias ; et
al. |
May 6, 2010 |
Modular interface for damping mechanical vibrations
Abstract
Interfaces for damping mechanical vibrations are used, for
example, for damping vibrations in the automotive or aerospace
industry. The interfaces have a base connection element, a load
connection element and a support element, with the support element
being connected to the base connection element via a pretensioning
device. A first energy converter system extends between engagement
points on the base connection element and engagement points on the
load connection element. A second energy converter system extends
between engagement points on the support element and engagement
points on the load connection element.
Inventors: |
Melz; Tobias; (Herdweg,
DE) ; Matthias; Michael; (Herdweg, DE) ;
Hanselka; Holger; (Heinrich-Delp-Str., DE) ; Herold;
Sven; (Jahnstrasse 7, DE) |
Correspondence
Address: |
IPxLAW Group LLP
95 South Market Street, Suite 570
San Jose
CA
95113
US
|
Assignee: |
Fraunhofer-Gesellschaft zur
Foerderung der angewandten Forschung e.V.
Muenchen
DE
|
Family ID: |
34105470 |
Appl. No.: |
12/616100 |
Filed: |
November 10, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10565469 |
Jan 19, 2006 |
7637359 |
|
|
PCT/EP04/07986 |
Jul 16, 2004 |
|
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|
12616100 |
|
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Current U.S.
Class: |
267/140.15 ;
267/140.5 |
Current CPC
Class: |
F16F 2228/08 20130101;
F16F 15/007 20130101 |
Class at
Publication: |
267/140.15 ;
267/140.5 |
International
Class: |
F16F 9/53 20060101
F16F009/53; F16F 6/00 20060101 F16F006/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 22, 2003 |
DE |
10333492.0 |
Dec 23, 2003 |
DE |
10361481.1 |
Claims
1. An interface for reducing mechanical vibrations, comprising: a
base connection element, a load connection element at least one
support element, at least a first energy converter system which is
embodied as an actuator system extending between at least one
engagement point located on the base connection element and at
least one engagement point located on the load connection element;
at least one second energy converter system which is embodied as an
actuator system extending between at least one engagement point
located on the support element and at least one engagement point
located on the load connection element; at least one elastic
pretensioning device connecting said base connection element to
said support element for exerting a compressive preload on the
first energy converter system and on the second energy converter
system, wherein the engagement points of said energy converter
systems establish punctiform points of contact, and wherein said
pretensioning device is embodied in such a way that a defined
adjustment of said preload exerted on said energy converter systems
is possible.
2. The interface as recited in claim 1, characterized in that the
energy converter systems include at least one of the following
elements: a piezoactuator, a shape memory alloy actuator, an
electrorheological or magnetorheological fluid actuator or fluid
damper, or an electrostrictive or magnetostrictive actuator.
3. The interface as recited in claim 1, characterized in that at
least one sensor system is connected to the load connection element
for determining at least one of the following parameters: travel,
velocity, acceleration, force.
4. An arrangement for reducing mechanical vibrations, characterized
by an interface as recited in claim 1, at least one system which
acts as at least one of the following: a movement sensor, an
acceleration sensor, a velocity sensor, a force sensor, and an
electronic circuit which generates, from a signal developed by the
at least one system, a target function for actuating the energy
converter systems of the interface.
5. An arrangement for reducing mechanical vibrations, characterized
by an interface as recited in claim 1, and an electronic circuit
operatively associated with said interface for providing passive or
semiactive vibration reduction.
6. An arrangement for reducing mechanical vibrations, characterized
in that a plurality of interfaces as recited in claim 1 are
connected in series, with the base connection element of each
following interface being connected to the load connection element
of the preceding interface.
7. An interface for reducing mechanical vibrations, comprising: a
base connection element; a support element separated from the base
connection element by an intermediate space; a load connection
element having a first part and a second part, said first part
being located in said intermediate space and said second part being
located outside of said intermediate space; a first energy
converter system extending between a first engagement point located
on the base connection element and a second engagement point
located on the load connection element, and a second energy
converter system extending between a third engagement point located
on the support element and a fourth engagement point located on the
load connection element; and an elastic pretensioning device
connecting the base connection element to the support element for
exerting a compressive preload on the first energy converter system
and on the second energy converter system, the pretensioning device
being embodied as an elastic pipe which surrounds said first and
second energy converter system.
8. An interface as recited in claim 7, characterized in that said
first and second energy converter systems include at least one
active element selected from the group consisting of a
piezoactuator, a shape memory alloy actuator, an electrorheological
fluid actuator, a magnetorheological fluid actuator, a fluid
damper, an electrostrictive actuator, and a magnetostrictive
actuator.
9. An interface as recited in claim 7, characterized in that at
least one sensor system adapted to determine at least one physical
quantity chosen from the group consisting of travel, velocity,
acceleration and force is connected to the load connection
element.
10. An interface as recited in claim 7, characterized in that at
least one of said first and second energy converter systems can
convert mechanical energy into electrical energy.
11. An arrangement for reducing mechanical vibrations, comprising:
an interface as recited in claim 7, at least one system which acts
as a movement sensor and/or acceleration sensor and/or velocity
sensor and/or force sensor, and an electronic circuit which
generates, from a signal of said one system, a target function for
actuating the energy converter systems of the interface.
12. An arrangement for reducing mechanical vibrations, comprising:
an interface as recited in claim 11, wherein said electronic
circuit cooperates with said energy conversion systems to
accomplish passive or semiactive vibration reduction.
13. An arrangement for reducing mechanical vibrations,
characterized in that a plurality of interfaces as recited in claim
7 are connected in such a way that in each case the base connection
element of the following interface is connected to the load
connection element of the preceding interface.
14. An interface for reducing mechanical vibrations, comprising: a
base connection element; a load connection element; a first support
element affixed to said base connection element by a first elastic
pretensioning device; a second support element affixed to said base
connection element by a second elastic pretensioning device; a
first energy converter system supporting said load connection in a
first direction and including at least one energy converter
extending between an engagement point located on the base
connection element and an engagement point located on the load
connection element, and at least one energy converter extending
between an engagement point located on the first support element
and an engagement point located on the load connection element; and
a second energy converter system supporting said load connection in
a second direction angularly disposed relative to said first
direction and including at least one energy converter extending
between an engagement point located on the base connection element
and an engagement point located on the load connection element, and
at least one energy converter extending between an engagement point
located on the second support element and an engagement point
located on the load connection element; said first elastic
pretensioning device being operative to exert a compressive preload
on the first energy converter system, and said second elastic
pretensioning device being operative to exert a compressive preload
on the second energy converter system.
15. An interface for reducing mechanical vibrations, comprising: a
base connection element; a load connection element; a first support
element affixed to said base connection element by a first elastic
pretensioning device; a second support element affixed to said base
connection element by a second elastic pretensioning device; a
first energy converter system supporting said load connection in a
first direction and including at least one energy converter
extending between an engagement point located on the first support
element and an engagement point located on the load connection
element; a second energy converter system supporting said load
connection in a second direction angularly disposed relative to
said first direction and including at least one energy converter
extending between an engagement point located on the second support
element and an engagement point located on the load connection
element; and a third energy converter system supporting said load
connection in a third direction angularly disposed relative to said
first and second directions and including at least one energy
converter extending between an engagement point located on the base
connection element and an engagement point located on the load
connection element; said first elastic pretensioning device being
operative to exert a compressive preload on at least the first
energy converter system, and said second elastic pretensioning
device being operative to exert a compressive preload on at least
the second energy converter system.
Description
RELATED APPLICATIONS/PRIORITY CLAIM
[0001] This Application is a Divisional Application of pending U.S.
patent application Ser. No. 10/565,469 filed Jan. 19, 2006 entitled
"Modular Interface for Damping Mechanical Vibrations", and which is
a National Phase Application of PCT Application PCT/EP2004/007986
filed Jul. 16, 2004, which claims priority to German Application
No. 103 33 492.0 filed Jul. 22, 2003 and German Application No. 103
61 481.1 filed Dec. 23, 2003; the disclosures of all the above
being expressively incorporated herein by reference, and to all of
which, priority is hereby claimed in this Application.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to an interface for damping or
isolating mechanical vibrations by means of a plurality of energy
converter systems. Such interfaces are used, for example, for
damping vibrations in the field of general machine engineering, the
automotive industry, the construction industry or the aerospace
industry.
[0004] Dynamic mechanical interference in the form of vibrations
which are excited, for example, by the operation of assemblies (for
example power supply assemblies) or by other ambient conditions,
are produced in machines, vehicles and similar modules. The
frequencies of these vibrations extend into the relatively high
frequency acoustic range and bring about undesired dynamic and/or
acoustic effects locally at the location where the interference is
produced or applied, or further away after transmission over
mechanical load paths. This results in losses of comfort, safety
problems, damage to components owing to structural fatigue,
shortened service life, reduced functionalities etc.
[0005] 2. Description of the Related Art
[0006] What is referred to as material damping, in which the
mechanical energy of the vibration is converted directly into
thermal energy, is frequently used to damp or isolate mechanical
vibrations. Examples of this are elastic or viscoelastic damping
systems.
[0007] In addition, measures which are based on other energy
converter systems are increasingly used. These energy converter
systems generally convert mechanical energy into electrical energy
and vice versa. Both effects are used to damp mechanical
vibrations. The distinction is generally made here between active,
semiactive and passive vibration dampers.
[0008] In the case of passive and semiactive vibration damping, the
mechanical energy of the vibrations is firstly converted into
electrical energy using an electric/mechanical energy converter
(for example a piezoceramic). This electrical energy is then
dissipated, i.e. converted into thermal energy, in a passive
electrical circuit (e.g. an ohmic resistor) in the case of passive
vibration damping, or diverted using an active electric circuit
(for example electric damper) in the case of semiactive vibration
damping. Such systems are described, for example, in N. W. Hagood
and A. von Flotow: Damping of Structural Vibrations with
Piezoelectric Materials and Passive Electrical Networks, Journal of
Sound and Vibration 146 (2), 243 (1991).
[0009] In the case of active vibration isolation, at least one
actuator system is connected between an interference source (base
side) and a connection side. In this context, "actuator" refers to
an energy converter which, for example, can convert electrical
signals into mechanical movements, for example a piezoactuator or a
pneumatic actuator. What is decisive is that the characteristic
(for example extent) of the actuators can be varied in a controlled
fashion by means of an actuation signal. An example of a system for
active vibration isolation using actuator elements is disclosed in
U.S. Pat. No. 5,660,255. Actuator elements and a small additional
mass are interposed between a base housing and a useful load which
is to be isolated. Sensors which record the displacement of the
small mass are mounted on said small mass. An actuation signal for
the actuator elements is generated from the displacement using an
electronic closed-control circuit and an external electrical energy
source. The actuator elements are actuated in such a way that the
vibration movement at the location of the useful load is largely
eliminated.
[0010] FIG. 1 shows a satellite as an example of active isolation
of interference sources and sensitive components which should be
protected from mechanical interference. The satellite contains
internal interference sources 1, for example mechanical coolers,
motors etc. Mechanical interference from these interference sources
1 is damped by active elements 2, 3, 4 so that the interference
from the interference sources 1 does not act on the sensitive
components 5 (cameras, reflectors, etc.) via transmission paths 3,
4.
[0011] In addition to the use for active, passive and semiactive
vibration damping, the electric/mechanical energy converters can
often simultaneously be used as actuating elements for mechanical
positioning of a useful load. This may be done, for example, by
virtue of the fact that an annular arrangement of a plurality of
actuators is integrated into a vibration-damping interface which
can bring about, for example, selective tilting of a structure with
respect to a base. Such a system is disclosed, for example, in DE
195 27 514 C2.
[0012] For structural reasons, actuator systems are frequently
operated in practice with a preload. This is frequently a
mechanical preload in the form of compressive loading or tensile
loading on the actuator system. For example in the case of
piezoactuators in which extension beyond the length at rest (i.e.
length of the actuator without voltage applied) would lead to
mechanical damage to the actuator, operation without preloading is
in practice inappropriate or not possible. However, the structural
implementation of a device for exerting a preload presents
problems, in particular in the case of the actuator or actuators
whose extension direction extends parallel to the force (for
example the force of the weight) exerted by the useful load, and
has a frequently negative effect on the effectiveness of the
actuator. U.S. Pat. No. 5,660,255 does not disclose a satisfactory
solution to this problem.
[0013] DE 195 27 514 C2 discloses an interface for reducing
vibrations in structural dynamic systems in which vibration
insulation occurs between a structure-side component and a
base-side component by means of a plurality of actuators which have
a main direction. Pressure pretensioning on the actuators is
ensured by anti-fatigue bolts between the base-side component and
the structure-side component. However, such a rigid mechanical
connection between the base-side component and the structure-side
component has the disadvantage that as a result a bridge is
provided via which vibrations can propagate from a base-side
interference source to the structure-side component.
SUMMARY OF THE INVENTION
[0014] The object of the present invention is to disclose an
interface for vibration reduction which transmits as little sound
as possible and which can be used for active, semiactive and
passive vibration isolation as well as for mechanically positioning
a load.
[0015] This object is achieved by means of the invention having the
features of the independent claim. Advantageous developments of the
invention are characterized in the subclaims.
[0016] An interface for reducing mechanical vibrations is proposed
which has a base connection element, a load connection element and
at least one support element. In this context, at least a first
energy converter system extends between at least one engagement
point located on the base connection element and at least one
engagement point located on the load connection element.
[0017] The energy converter system can be based on various physical
principles depending on the application and requirements. In
particular piezoactuators have proven to be particularly
advantageous. However, actuators which are based on what are known
as shape-memory alloys or other materials with a memory effect as
well as magnetostrictive or electrostrictive actuators, pneumatic
or hydraulic actuators, magnetorheological or electrorheological
fluid actuators and damping elements can be advantageously used.
Combinations of different energy converter systems are also
possible, for example the combination (for example a series or
parallel circuit) of a piezoactuator with a "conventional" damping
system, for example a spring system or a rubber damper.
[0018] Spring systems or elastic materials can also be used in
combination with piezoactuators in order to generate a preload on
the piezoactuator or to increase an existing preload. Vibrations in
different frequency ranges can also be compensated by combining
different operative principles and energy converter systems, that
is to say for example high-frequency vibrations due to active or
passive damping by means of piezoactuators, low-frequency
vibrations due to conventional damping elements (for example
viscoelastic dampers).
[0019] At least one second energy converter system extends between
at least one engagement point located on the support element and at
least one engagement point located on the load connection element.
The descriptions stated above relating to the first energy
converter system apply appropriately for the selection and the
composition of this second energy converter system.
[0020] The base connection element is connected to the at least one
support element via at least one pretensioning device in such a way
that the pretensioning device can exert a preload on the first
energy converter system and on the second energy converter system.
This preload may be, for example, mechanical compressive loading or
tensile loading. It is optionally also possible to operate with a
preload of zero, that is to say an operating mode in which force is
not exerted on the energy converter systems. This preload (also the
preload of zero) can also be combined, for example, with an initial
electrical load. The pretensioning device may be elastic or
inelastic. The preload can be exerted directly or indirectly on the
energy converter systems, that is to say for example also
indirectly by means of an additional spring system.
[0021] The load connection element is to have a part which is
located in an intermediate space between the base connection
element and the support element and a part which is located outside
the intermediate space between the base connection element and the
support element.
[0022] Intermediate space is to be understood here as not only a
closed-off cavity but also any space between the base connection
element and the load connection element.
[0023] This condition ensures the advantage that the load
connection element is easily accessible for mounting a load. The
vibration insulation is provided, for example, by means of the part
located between the base connection element and the support
element, as a result of which compressive pretensioning can be
exerted on the energy converter systems. On the other hand, a load
is mounted on that part of the load element located outside the
intermediate space between the base connection element and the
support element. Said part is then no longer restricted by the
spatial dimensions of the intermediate space, that is to say may be
configured as desired in terms of shape and size and as a result,
for example, take into account specific requirements of the
connection geometry of the load.
[0024] The base connection element and the load connection element
may have, for example, a planar mounting face. This facilitates the
installation of the interface in existing structures for isolating
a vibration-sensitive load from one or more interference sources.
Furthermore, in this way it is possible to easily connect a
plurality of interfaces in series.
[0025] The described interface can be integrated into
structures
[0026] as a bearing element,
[0027] as a modular transmission element and/or
[0028] as an actuation element.
[0029] The proposed arrangement is characterized in particular by
the fact that the load connection element is generally connected to
the support element or the base connection element only via the
first and second energy converter systems. In this way, the number
of sound bridges between base-side interference sources and a
useful load is reduced to the technically necessary minimum.
[0030] Despite this reduction in the sound bridges, the rigid or
flexible pretensioning device, which produces a connection between
the base connection element and the support element, permits a
defined setting of a pretensioning of the energy converter systems.
This may be done, for example, by virtue of the fact that the
pretensioning device used is an elastic element, anti-fatigue
screws or similar elements with a variable length.
[0031] It is possible to use energy converter systems with a common
preferred direction or with different preferred directions, the
latter option having the purpose, for example, of isolating
vibrations in different spatial directions. A separate support
element and a separate pretensioning device is then advantageously
used for each spatial direction. Preferably in each case at least
one energy converter system which extends between the base
connection element and the load connection element and at least one
energy converter system which extends between the load connection
element and the support element is used for each spatial direction.
In turn, pretensioning can then be exerted on the energy converter
systems without sound bridges being provided between the base
element and the load connection element.
[0032] Furthermore, it is also possible to use more than two energy
converter systems for one spatial direction. This may be
advantageous in particular if the energy converter systems are
actuator systems which are intended to bring about not only pure
translation of the load connection element but also, for example,
tilting. If, for example, two pairs of actuator systems are
arranged in parallel, unequal extension of the two pairs leads to
tilting of the load connection element about an axis perpendicular
to the preferred direction of the two pairs of actuator systems. In
analogous fashion it is possible to use a plurality of pairs of
actuator systems to bring about tilting of the load connection
element about a plurality of axes. In this way it is possible, for
example, also to isolate torsional vibrations in the base
connection element from the load connection element.
[0033] In a further advantageous refinement of the invention, the
base connection element and the load connection element each have
standardized connection geometries. These connection geometries may
be, for example, threads, flanges, screwed bolts etc. This permits
rapid and cost-effective exchange or supplementation of existing
elements and structures by the described interface for reducing
vibration. For example, in satellite engineering it is easily
possible to connect the interface between the main body, which
contains, for example, interference sources in the form of motors,
and a position-sensitive antenna without structural changes being
necessary to the entire arrangement. It is possible, for example,
to resort to standardized flange geometries.
[0034] The pretensioning device advantageously has a pipe which
surrounds the actuator systems. The pipe may have circular,
rectangular or any desired cross-sectional geometry.
[0035] This is advantageous in particular if all the energy
converter systems have a common preferred direction. The enclosed
pipe may be of rigid or flexible design and is particular designed
in such a way that the tubular axis is oriented approximately
parallel to the preferred direction of the actuator systems. The
pipe protects the actuator systems against environmental influences
such as, for example, moisture, dirt or the like. Furthermore, the
pipe stabilizes the energy convert systems against effects of
forces perpendicular to the preferred direction (for example
shearing forces) which could cause mechanical damage to the energy
converter systems.
[0036] In different methods for damping vibrations it is
advantageous to generate information about the actual vibration of
the load connection element. For this reason, a sensor system for
determining, for example, travel, velocity, acceleration or force
can be connected or intermediately connected to an element of the
interface. In particular it is advantageous if a sensor is
connected to the load connection element. Further sensors systems
may be connected, for example, to the base connection element.
[0037] The sensor systems may be, for example, capacitive or
piezoelectric acceleration or force sensors or magnetic,
electrostatic or interferometric position or velocity sensors.
[0038] The information of the at least one sensor system may be
used, for example, for active vibration damping. In this context,
actuator systems may be used in particular as energy converter
systems. The signals of the sensor system are made available to an
electronic closed loop control system. The electronic closed loop
control system generates control signals (target function) from the
sensor signals, said control signals being converted into actuation
signals for the actuator systems by means of a power supply. These
actuation signals are used to excite the actuator systems to
vibrate, said vibrations being, for example, in antiphase with
respect to the vibrations to be isolated and eliminating or damping
said vibrations at the location of the load.
[0039] In one development of the invention, at least one energy
converter system is embodied entirely or partially as an actuator
system. In this context, part of this actuator system will be in
turn capable of being used at the same time as an energy converter
which can convert mechanical energy into electrical energy.
[0040] In this development, both energy conversion directions are
therefore used simultaneously. Whereas electrical energy is
typically converted into mechanical energy in an actuator, in this
embodiment of the invention mechanical energy is converted
simultaneously into electrical energy at least in part of an
actuator. Actuators which are capable of carrying out this reversal
of the converter principle are also referred to as multifunctional
converter systems. The materials used in this context, which can
simultaneously bear mechanical loads and act as an actuator or
sensor (see below) are referred to as multifunctional
materials.
[0041] The conversion can be carried out, for example, by utilizing
the piezoelectrical effect, for example by means of a piezoceramic.
In this context, a pressure on a piezoceramic or fluctuations in
pressure in a piezoceramic are converted into electrical signals.
Since piezoactuators are frequently composed of stacks of a large
number of piezoceramic layers, it is possible, for example, to use
a layer from this stack simultaneously for converting mechanical
energy into electrical energy.
[0042] This development has various advantages. On the one hand, it
is possible to dispense at least partially with the use of
additional sensors. The electrical signals which are generated by
the actuator system serve simultaneously as sensor signals and can
contain, for example information about the acceleration or velocity
of the movement of a useful load.
[0043] In this way it is possible to determine the system response
of the entire system to interference, for example by means of the
interface. For example the actuator systems of the interface can
have a specific reference structure stimulation applied to them.
This reference structure stimulation brings about a structure
response by the entire system in the form of mechanical vibrations.
By recording the electrical signal of an actuator which acts as an
energy converter between mechanical energy and electrical energy it
is possible to record the structure response by means of measuring
equipment. The measured structure response, e.g. of the
transmission properties, between the actuator-induced reference
stimulation and sensor or the determination of impedance permits
conclusions to be drawn about the current structural state of the
entire system, for example by comparing the measured structure
response or determining structure characteristic values with
reference structure responses or reference structure characteristic
values stored in a database.
[0044] A further advantage of the simultaneous use of at least part
of an actuator system as a mechanical/electrical energy converter
is the possibility of using it as a passive or semiactive vibration
damper. In this context, an electronic circuit is used to dissipate
the electrical energy.
[0045] In the simplest case, this electronic circuit is composed of
ohmic resistor in which the electrical energy is converted
partially into heat. Even more efficient vibration damping can be
achieved by additionally using one or more coils and/or one or more
capacitors. For example, the mechanical vibrations of the interface
can thus result in periodic fluctuations in the charges on the
surfaces of a piezoceramic of a piezoactuator of the interface.
This corresponds to periodically fluctuating charges on the plates
of a capacitor. If the two plates of the capacitor (that is to say
the two surfaces of the piezoceramic) are connected to one another
by means, for example, of an ohmic resistor and a coil, the mode of
operation of the arrangement corresponds to the effect of a damped
electrical oscillatory circuit.
[0046] A further increase in the efficiency of the vibration
damping can be achieved by using what is referred to as a
"synthetic inductor" instead of at least one coil. This synthetic
inductor is generally composed of a combination of a plurality of
ohmic resistors with one or more operational amplifiers. In this
way it is possible to achieve higher inductances than with
conventional coils. As a result, the damping of the oscillatory
circuit is increased further. This technology is described, for
example, in D. Mayer, Ch. Linz and V., Krajenski: Synthetic
Inductors for Semipassive Damping, 5. Magdeburger Maschinenbautage,
2001.
[0047] The efficiency of the vibration damping can be further
increased by connecting in series a plurality of the interfaces
described above in one of the described configurations and wiring
arrangements in cascades. In this context, in each case the base
connection element of the following interface is connected to the
load connection element of the preceding interface.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0048] In the text which follows the invention will be explained in
more detail with reference to exemplary embodiments which are
illustrated schematically in the figures. However, it is not
restricted to the examples. Identical reference numbers in the
individual figures relate to elements which are identical or
functionally identical or which correspond to one another in terms
of their functions. In particular:
[0049] FIG. 1 shows a satellite with active isolation of
interference sources and sensitive components in accordance with
the prior art;
[0050] FIG. 2 shows a structural mechanical interface for vibration
damping;
[0051] FIG. 3 shows a simplified electrical wiring arrangement for
active vibration damping of the interface illustrated in FIG.
2;
[0052] FIG. 4 shows a means of actuating the actuator systems of
the interface in FIG. 2 for the selective tilting of a useful
load;
[0053] FIG. 5 shows the possible tilting axes for an interface with
actuators which are arranged with 120.degree. rotational
symmetry;
[0054] FIG. 6 shows an alternative embodiment of a structural
mechanical interface for vibration damping;
[0055] FIG. 7 shows a further alternative embodiment of a
structural mechanical interface for vibration damping;
[0056] FIG. 8 shows a structural mechanical interface for vibration
damping in a perspective partial illustration with a cut-out
segment;
[0057] FIG. 9 shows a structural mechanical interface for vibration
damping in two spatial directions which are perpendicular to one
another;
[0058] FIG. 10 shows a structural mechanical interface for
vibration damping in three spatial directions which are not
perpendicular to one another;
[0059] FIG. 11 shows an arrangement for the partial use of a
piezoactuator of a structural mechanical interface as a sensor for
a structural analysis;
[0060] FIG. 12 shows an electrical wiring system of part of a
piezoactuator of a structural mechanical interface for passive
vibration damping; and
[0061] FIG. 13 shows an electrical wiring system of part of a
piezoactuator of a structural mechanical interface for passive
vibration damping which is an alternative to FIG. 12.
DETAILED DESCRIPTION OF THE INVENTION
[0062] FIG. 2 illustrates a preferred embodiment of the described
interface for vibration damping. A base connection element 10 is
connected to a support element 14 via a pretensioning device 12. A
first energy converter system, which is composed of the
piezoactuators 16 and 18, extends between the engagement points 20
and 22 on the base connection element 10 and the engagement points
24 and 26 on the load connection element 28. A second energy
converter system which is composed of the piezoactuators 30 and 32
extends between the engagement point 34s and 36 on the support
element 14 and the engagement points 38 and 40 on the load
connection element 28.
[0063] The illustrated arrangement shows merely a cross section
through the structural mechanical interface. The arrangement of
this example is symmetrical with the indicated axis 42 of symmetry,
with the exception of the piezoactuators 16, 30, 18, 32. The base
connection element 10 is therefore a circular disk and the support
element 14 an annular disk. The load connection element 28 is in
the shape of a cylindrical cap, with part of the load connection
element being located in the intermediate space between the
pretensioning device 14 and the base connection element 10 and part
being located outside. The pretensioning device 12 is composed of
an elastic pipe with a diameter which is identical to the external
diameter of the circular disk of the base connection element 10 and
to the external diameter of the annular disk of the support element
14. The pretensioning is carried out by virtue of the fact that the
length of the elastic pipe is selected such that the pipe is
expanded in the state of rest of the arrangement. As a result
compressive pretensioning is exerted simultaneously on all the
piezoactuators.
[0064] Instead of the illustrated four piezoactuators it is also
possible to use more than four actuators. These piezoactuators are
preferably arranged in a rotationally symmetrical fashion with
respect to the axis 42 of symmetry.
[0065] The base connection element 10 and the load connection
element 28 are configured in such a way that simple and rapid
mounting of the interface between a base side which is excited to
oscillate by interference sources 1 and a load which is to be
isolated can take place. For this purpose, the base connection
element 10 and the load connection element 28 are provided with
threaded bores with standard dimensions.
[0066] If the piezoactuators 16 and 18 are lengthened by
simultaneous electric actuations and the piezoactuators 30 and 32
are shortened to the same degree by suitable electrical actuations,
the distance between the load connection element 28 and base
connection element 10 is increased. Correspondingly, shortening the
piezoactuators 16 and 18 and simultaneously lengthening the
piezoactuators 30 and 32 reduces the distance between the load
connection element 28 and base connection plate 10. The electric
actuations of the piezoactuators are not illustrated in FIG. 2.
[0067] If the piezoactuators 16 and 30 and 18 and 32 are each in
antiphase, for example actuated with sinusoidal alternating voltage
of suitable amplitude and frequency, the load connection element 28
swings up and down in relation to the base connection element 10.
This can be used, for example, for active vibration damping.
[0068] FIG. 3 illustrates an electric wiring system for the
interface according to FIG. 2. An acceleration sensor 60 which is
secured to the load connection element 28 is connected to the input
of an electronic closed loop control system 64 via a phase shifter
62. An output of the electronic closed loop control system 64 is
connected to the piezoactuators 30 and 32 via a post-amplifier 66.
Furthermore, the output of the electronic closed loop control
system 64 is connected to the piezoactuators 16 and 18 via a
180.degree. phase shifter 68 and a second postamplifier 70.
[0069] If vibrations of the base connection element 10 are to be
isolated from the load connection element 28, these vibrations are
detected using the acceleration sensor 60. The sensor signal is
then converted into suitable antiphase actuation signals for the
piezoactuators 16 and 30 and 18 and 32 using the electronic closed
loop control systems 64 and the first phase shifter 62. The first
phase shifter 62 can serve, for example, for compensating phase
shifts between the actual movement of the load connection element
28 and the sensor signals. This necessity depends, inter alia, on
the method of operation of the sensor 60. For example in the case
of sinusoidal vibrations in which a phase shift of 90.degree.
occurs between the acceleration and velocity and between the
velocity and position, the signal of a velocity sensor would have
to be phase shifted by 90.degree. in order to be able to bring
about a suitable change in length of the piezoactuators. Delays in
the electronic closed loop control system 64 and resulting phase
shifts can also be compensated by the phase shifter 62.
[0070] The signals generated in the electronic closed loop control
system 64 are amplified further in the postamplifiers 66 and 70 and
fed to the actuators 30 and 32 and 16 and 18. The second phase
shifter 68 is necessary since the two actuator systems 16, 18 and
30, 32 generally have to be actuated in antiphase.
[0071] The piezoactuators 16 and 30 and 18 and 32 are each excited
to undergo antiphase vibrations by which the vibrations are
transmitted to the load connection element 28. In the load
connection element 28 the vibrations excited by the piezoactuators
are superimposed on the vibrations of the basic connection elements
10 in a destructive fashion if the phase is selected suitably so
that the vibrations of the load connection element 28 are
damped.
[0072] In the illustrated arrangement, the piezoactuators 16, 18 of
the first actuator system and the piezoactuators 30, 32 of the
second actuator system are each configured in the same way, i.e.
identical actuation signals bring about identical changes in
length. For this reason, in each case a single postamplifier 66 or
70 can be used for the actuators of an actuator system. If
different actuators are used within an actuator system, different
postamplifiers would have to be used for each of the actuators.
[0073] The actuation of the piezoactuators is illustrated in a
highly simplified form. As a rule, each piezoactuator has two
electrical terminals to which different voltages have to be
applied. The difference in voltage between the electric terminals
determines the extension of the length of the piezoactuator.
[0074] FIG. 4 illustrates how tilting oscillations of the base
connection element 10 can also be compensated or damped by
selective actuation of the piezoactuators of the arrangement in
FIG. 2. By virtue of the fact that the piezoactuator 30 is set, by
a suitable electric actuation signal, to a greater length than the
piezoactuator 32, and the piezoactuator 16 is correspondingly set
to a smaller length than the piezoactuator 18, the load connection
element 28 is tilted relative to the plane of the base connection
element 10. For this purpose, the piezoactuators 16, 18, 30, 32
require individual electric actuation means (not shown).
[0075] If tilting vibrations occur in the base connection element
10, they can be detected, for example, by comparing the signals of
different sensors which are mounted at different locations on the
surface of the load connection element 28. The signals are then
converted into suitable actuation signals of the piezoactuators
using an electronic closed loop control system 64 So that the load
connection element 28 carries out a tilting vibration relative to
the base connection element 10, and said tilting oscillation is
superimposed in a destructive fashion on the tilting oscillation of
the base connection element 10 and thus damps it in the load
connection element 28.
[0076] The electronic closed loop control system 64 can, for
example, be constructed in such a way that a sum signal and a
difference signal are formed from the signals of two sensors which
are secured to the load connection element 28 and said sum signal
and difference signal are converted in separate controllers to form
actuation signals for the piezoactuators. The actuation signal for
each piezoactuator is then a superimposition of signals from the
two controllers.
[0077] In this exemplary embodiment in which only two actuator
pairs 16 and 30 and 18 and 32 are used, the load connection 28 can
only be tilted about an axis perpendicular to the axis 42 of
symmetry. If, as described above, more actuator pairs are used,
tilting about a plurality of axes perpendicular to the axis 42 of
symmetry is possible. FIG. 5 illustrates in sketch form in a plan
view an interface with three actuator pairs 80, 82, 84 as an
example. Only the actuator pairs 80, 82, 84 and the tilting axes
are illustrated. Each of the actuator pairs 80, 82 and 84 is
respectively composed of an actuator which extends between an
engagement point on the base connection element 10 and an
engagement point on the load connection element 28, and an actuator
which extends between an engagement point on the support element 14
and an engagement point on the load connection element 28. The
actuators of, in each case, one actuator pair are arranged linearly
and perpendicularly with respect to the plane of the drawing in
this embodiment and therefore cannot be seen individually. The
actuator pairs 80, 82, 84 are arranged in a rotationally
symmetrical fashion through 120.degree. about the axis 42 of
symmetry which is perpendicular to the plane of the drawing.
[0078] The arrangement allows the load connection element 28 to
tilt about the three tilting axes 88, 90 and 92 which are each
arranged perpendicularly to the axis 42 of symmetry.
[0079] The invention provides the advantage that in addition to
tilting vibrations about various axes it is also possible to damp
torsional vibrations of the base connection element 10. This can be
done, for example, by cyclically actuating the actuator pairs 80,
82 and 84.
[0080] FIG. 6 illustrates an example which shows that the
engagement points of one of the actuators of an actuator pair do
not need to be arranged in a line. The load connection element 28
is embodied in this design in such a way that the sum of the
distances between the engagement points 34 and 36 and 38 and 40 and
the distances between the engagement points 24 and 26 and 20 and 22
is greater than the distance between the base connection element 10
and the support element 14. In other words, the load connection
element 28 can be configured in such a way that the sum of the
lengths of an actuator pair 16, 30 and 18, 32 does not need to
correspond to the distance between the base connection element 10
and support element 14. Configurations in which the length of an
individual actuator exceeds the distance between the base
connection element 10 and support element 14 are also possible.
[0081] As a result, it is possible to make use of the different
lengths of actuators without the external design, which is
determined essentially by the distance between the base connection
element 10 and support element 14, having to be significantly
changed. Since the maximum change in length of a piezoactuator
depends on the overall length of the piezo, it is thus possible to
lengthen the actuation path of the interface by using relatively
long piezoactuators. Furthermore, by using different piezoactuators
it is possible to damp vibrations with different vibration
frequencies since the resonant frequency of the piezoactuators also
depends significantly on the overall length of the
piezoceramic.
[0082] FIG. 7 illustrates an exemplary embodiment which shows that
the actuators 100 which extend between the engagement points on the
base connection element 10 and the load connection element 28 and
the actuators 106 which extend between the engagement points on the
support element 14 and on the load connection element 28 do not
need to be arranged on the same side of the axis 42 of symmetry. A
piezoactuator 100 extends between an engagement point 102 on the
base connection element 10 and an engagement point 104 on the load
connection element 28. A further piezoactuator 106 extends between
an engagement point 108 on the load connection element 28 and an
engagement point 110 on the support element 14.
[0083] In many cases, the actuators are arranged in such a way that
overall the torques which are exerted on the load connection
element 28 cancel one another out. This ensures that all the
actuators are always subjected to pressure pretensioning. In the
arrangement illustrated in FIG. 7, this can occur, for example, by
further piezoactuators (not illustrated in this sectional view)
being adjacent to the piezoactuator 106, said further
piezoactuators extending between engagement points on the base
connection element 10 and engagement points on the load connection
element 28 and thus compensating the torque which is exerted on the
load connection element 28 by the piezoactuator 106. For example,
the arrangement can have six piezoactuators which are rotationally
symmetrical through 120.degree. Said piezoactuators are arranged in
such a way that in each case one actuator of the first actuator
system (i.e. extending between engagement points on the base
connection element 10 and the load connection element 28) and one
actuator of the second actuator system (i.e. extending between
engagement points on the support element 14 and the load connection
element 28) lie opposite one another relative to the axis 42 of
symmetry. Adjacent actuators are associated with different actuator
systems.
[0084] FIG. 8 illustrates an interface for vibration damping in a
perspective partial illustration with a cut-out segment. A
piezoactuator 130 extends between an engagement point 132 on the
base connection element 10 and an engagement point 134 on the load
connection element 28. A further piezoactuator 136 extends between
an engagement point 138 on the load connection element 28 and an
engagement point 140 on the support element 14.
[0085] In this illustration it is apparent that both the base
connection element 10 and the surface of the load connection
element 28 are freely accessible for mounting purposes. The
pretensioning device 12 is embodied as an elastic, cylindrical pipe
which completely encloses the actuator systems and thus protects
them against undesired loading by shearing forces perpendicular to
their preferred direction and against environmental effects. The
electrical feedlines to the piezoactuators can be routed to the
piezoactuators 130 and 136 through an opening 142 in the base
connection element 10, for example.
[0086] FIG. 9 illustrates a plan view of an arrangement which shows
the use of the invention for vibration damping in various spatial
directions. An actuator system which is composed of the
piezoactuators 160 and 162 extends between the engagement points
164 and 166 on the base connection element 10 and the engagement
points 168 and 170 on the load connection element 28. An actuator
system which is composed of piezoactuators 172 and 174 extends
between the engagement points 176 and 178 on a first support
element 180 and the engagement points 182 and 184 on the load
connection element 28. The actuators 160, 162, 172 and 174 have the
same spatial direction (referred to below as the X direction) as
the preferred direction.
[0087] An actuator system which is composed of the piezoactuators
190 and 192 extends between the engagement points 194 and 196 on
the base connection element 10 and the engagement points 198 and
200 on the load connection element 28. An actuator system which is
composed of the piezoactuators 202 and 204 extends between the
engagement points 206 and 208 on a second support element 210 and
the engagement points 212 and 214 on the load connection element
28. The actuators 190, 192, 202 and 204 have the same spatial
direction (referred to below as the Y direction) as the preferred
direction, with this spatial direction being perpendicular to the
abovementioned preferred direction of the actuators 160, 162, 172
and 174.
[0088] In this exemplary embodiment, the support element 14 is
composed of two separate support elements 180 and 210. They are
each connected to the base connection element 10 with a
pretensioning device 216 or 218 (for example a rubber cube).
[0089] The load can be mounted on the load connection element 28
having, in this example, a cross-shaped cross section, by virtue of
the fact that the load connection element additionally has a planar
mounting plate which is mounted on the cross of the load connection
element.
[0090] The arrangement has various advantages. On the one hand,
transverse vibrations of the base connection element 10 in the X
and Y directions can be damped by suitably actuating the
piezoactuators. In this context it is possible, for example, to
use, for each spatial direction, an electronic circuit for active
vibration damping in a way which is analogous to the circuit
described in FIG. 3. In addition, tilting vibrations of the base
connection element 10 toward the X axis or Y axis can also be
compensated by suitable actuation of the piezoactuators in a way
which is analogous to FIG. 4.
[0091] The piezoactuators are pretensioned differently in the two
spatial directions by the pretensioning devices 216 and 218. This
may be advantageous for applications in which different types of
piezoactuators are to be used in the X and Y directions owing, for
example, to different vibrations being expected in these two
spatial directions.
[0092] In addition to the actuators which are illustrated here in
the X and Y directions, it is also possible to use additional
actuators in an analogous fashion in the spatial direction which is
perpendicular to the X and Y directions. A separate support element
is also appropriate for this again. This support element is
preferably embodied again in such a way that the load connection
element 28 is freely accessible for mounting purposes.
[0093] FIG. 10 illustrates an arrangement for vibration damping in
various spatial directions which is an alternative to FIG. 9. The
arrangement has, like the arrangement in FIG. 9, in turn a base
connection element 10 and two support elements 180 and 210 which
are connected to the base connection element 10 via the
pretensioning devices 216 and 218. A first piezoactuator 230
extends between an engagement point 232 on the base connection
element 10 and an engagement point 234 on the load connection
element 28. A second piezoactuator 236 extends between an
engagement point 238 on the support element 180 and an engagement
point 240 on the load connection element 28. A third piezoactuator
242 extends between an engagement point 244 on the support element
210 and an engagement point 246 on the load connection element
28.
[0094] The arrangement shows that it is not absolutely necessary
for in each case an actuator which extends between the base
connection element 10 and the load connection element 28 and an
actuator which extends between a support element and the load
connection element 28 to have the same preferred direction.
[0095] As an alternative to the arrangement illustrated in FIG. 10
it is also possible to use further piezoactuators for damping
vibrations in further spatial directions. Thus, for example four
piezoactuators and three support elements could be arranged in such
a way that the piezoactuators each point into the corners of a
tetrahedron which is standing on one of its tips.
[0096] FIG. 11 illustrates how a piezoactuator can be used as a
sensor for a structural analysis. Said figure is a detailed view of
any piezoactuator from one of the abovementioned exemplary
embodiments, that is to say for example the piezoactuator 16 in
FIG. 2. The piezoactuator is composed in this example of a stack of
a plurality of piezoceramic elements.
[0097] A specific voltage is applied to the piezoactuator 16 by
means of a variable voltage source 260, with the switch 262 being
initially closed. If the switch 262 is then suddenly opened, the
length of the piezoactuator 16 changes suddenly. The entire system,
that is to say also the other elements which are not illustrated
here such as, for example, the load connection element 28, starts
to vibrate. This is referred to as the structural response of the
entire system to the stimulation by opening the switch 262.
[0098] The vibrations of the entire system in turn bring about a
periodically changing pressure on the piezoactuator 16. Owing to
the piezo effect, these pressure fluctuations result in
fluctuations in the electrical voltage between the electrodes 264
and 266 of a piezoceramic element 268 of the piezoactuator 16.
These voltage fluctuations can be registered and recorded using a
measuring device 270.
[0099] Instead of simply switching off the voltage which is applied
to the piezoactuator 16 it is also possible to stimulate the entire
system by means of other voltage profiles. For example, a simple
sinusoidal voltage can be used or a voltage pulse. The respective
structural response of the entire system to various types of
stimulations can be used for a system analysis of the entire system
by comparison with simulation values or by comparison with
reference structural responses. If, for example, the structure
interface is integrated into a carrier arm of a satellite system or
into a spring-damper system in the region of the chassis of a motor
vehicle, for example defects (for example due to material fatigue,
etc.) can be detected and suitable countermeasures taken early by
means of regular structural analyses.
[0100] Furthermore, the piezoceramic element 268 which acts as a
sensor in FIG. 11 can also be used for active vibration damping
according to FIG. 3. Instead of the signal of the acceleration
sensor 60 in FIG. 3, the voltage which occurs between the
electrodes 264 and 266 (after suitable phase shifting in the phase
shifter 62) is then used as an input signal for the electronic
closed loop control system 64. In this way it is possible to
dispense with additionally providing a sensor in the interface.
[0101] FIGS. 12 and 13 show possible wiring arrangements of the
energy converters for vibration damping. These are again any
piezoactuator of the interface, and a plurality of actuators can
also be wired simultaneously in this way or a similar way. In the
text which follows it is assumed that the actuator is the actuator
16 which extends between the base connection element 10 and the
load connection element 28. The base connection element 10 and the
load connection element 28 are illustrated in highly simplified
form and the engagement points 20 and 24 and the other components
of the interface are not illustrated for reasons of
simplification.
[0102] The piezoactuator 16 in FIGS. 12 and 13 is, similar to the
arrangement illustrated in FIG. 11, configured again as a stack of
a plurality of piezoceramic elements (sixteen in this case). The
piezoceramic elements 7 to 13 (counted from the side where the
basic connection element 10 is) are combined to form a unit 280 in
such a way that the electrical potential of this unit can be tapped
off between a terminal 282, near to the base connection element 10,
of the unit 280 and a terminal 284, near to the load connection
element 28, of the unit 280.
[0103] In FIG. 12, the terminals 282 and 284 are each connected to
one end of an ohmic resistor 286. Furthermore, the terminal 282 is
connected to ground potential. In FIG. 13, the terminal 282 is
connected to an inductor 288. This inductor 288 is connected to an
ohmic resistor 286 which is in turn connected to the terminal 284.
Furthermore, the terminal 282 is connected to ground potential. If
the load connection element 28 carries out mechanical vibrations
relative to the base connection element 10, this results in
periodically fluctuating pressure on the piezoactuator 16. Owing to
the piezoelectric effect, these pressure fluctuations lead to
fluctuations in the charge on the surfaces of the unit 280 lying
opposite. These charge fluctuations result in a fluctuation of the
voltage between the terminals 282 and 284, which leads to a
periodic flow of current through the electric wiring
arrangement.
[0104] The arrangement in FIG. 13 acts as a damped series
oscillatory circuit composed of a capacitor, an inductor and an
ohmic resistor. The terminals 282 and 284 act here like the plates
of a capacitor whose charge varies periodically. At each
oscillation, some of the electrical energy in the ohmic resistor
286 is converted into thermal energy and the vibration is thus
damped. The selection of suitable ohmic resistors and inductors is
made in accordance with the method described in N. W. Hagood and A.
von Flotow: Damping of Structural Vibrations with Piezoelectric
Materials and Passive Electrical Networks, Journal of Sound and
Vibration 146 (2), 243 (1991).
LIST OF REFERENCE NUMERALS
[0105] 1 Internal interference sources [0106] 2 Active element
[0107] 3 Active element [0108] 4 Transmission paths [0109] 5
Sensitive elements [0110] 10 Base connection element [0111] 12
Pretensioning device [0112] 14 Support element [0113] 16
Piezoactuator of the first actuator system between base connection
element 10 and load connection element 28 [0114] 18 Piezoactuator
of the first actuator system between base connection element 10 and
load connection element 28 [0115] 20 Engagement point of the
actuator 16 on the base connection element 10 [0116] 22 Engagement
point of the actuator 18 on the base connection element 10 [0117]
24 Engagement point of the actuator 16 on the load connection
element 28 [0118] 26 Engagement point of the actuator 18 on the
load connection element 28 [0119] 28 Load connection element [0120]
30 Piezoactuator of the second actuator system between support
element 14 and load connection element 28 [0121] 32 Piezoactuator
of the second actuator system between support element 14 and load
connection element 28 [0122] 34 Engagement point of the
piezoactuator 30 on the support element 14 [0123] 36 Engagement
point of the piezoactuator 32 on the support element 14 [0124] 38
Engagement point of the piezoactuator 30 on the load element 28
[0125] 40 Engagement point of the piezoactuator 32 on the load
element 28 [0126] 42 Axis of symmetry [0127] 60 Acceleration sensor
[0128] 62 Phase shifter [0129] 64 Electronic closed loop control
system [0130] 66 First postamplifier [0131] 68 180.degree. phase
shifter [0132] 70 Second postamplifier [0133] 80 First actuator
pair [0134] 82 Second actuator pair [0135] 84 Third actuator pair
[0136] 88 Tilting axis [0137] 90 Tilting axis [0138] 92 Tilting
axis [0139] 100 Piezoactuator [0140] 102 Engagement point of
piezoactuator 100 on the base connection element [0141] 104
Engagement point of the piezoactuator 100 on the load connection
element [0142] 106 Piezoactuator [0143] 108 Engagement point of the
piezoactuator 106 on the load connection element [0144] 110
Engagement point of the piezoactuator 106 on the support element
[0145] 130 Piezoactuator [0146] 132 Engagement point of the
piezoactuator 130 on the base connection element [0147] 134
Engagement point of the piezoactuator 130 on the load connection
element [0148] 136 Piezoactuator [0149] 140 Engagement point of the
piezoactuator 136 on the load connection element [0150] 142
Engagement point of the piezoactuator 136 on the support element
Opening in the base connection element for electric feedlines to
the piezoactuators [0151] 160 Piezoactuator [0152] 162
Piezoactuator [0153] 164 Engagement point of the piezoactuator 160
on the base connection element [0154] 166 Engagement point of the
piezoactuator 162 on the base connection element [0155] 168
Engagement point of the piezoactuator 160 on the load connection
element [0156] 170 Engagement point of the piezoactuator 162 on the
load connection element [0157] 172 Piezoactuator [0158] 174
Piezoactuator [0159] 176 Engagement point of the piezoactuator 172
on the support element 180 [0160] 178 Engagement point of the
piezoactuator 174 on the support element 180 [0161] 180 Support
element [0162] 182 Engagement point of the piezoactuator 172 on the
load connection element [0163] 184 Engagement point of the
piezoactuator 174 on the load connection element [0164] 190
Piezoactuator [0165] 192 Piezoactuator [0166] 194 Engagement point
of the piezoactuator 190 on the base connection element [0167] 196
Engagement point of the piezoactuator 192 on the base connection
element [0168] 198 Engagement point of the piezoactuator 190 on the
load connection element [0169] 200 Engagement point of the
piezoactuator 192 on the load connection element [0170] 202
Piezoactuator [0171] 204 Piezoactuator [0172] 206 Engagement point
of the piezoactuator 202 on the support element 210 [0173] 208
Engagement point of the piezoactuator 204 on the support element
210 [0174] 210 Support element [0175] 212 Engagement point of the
piezoactuator 202 on the load connection element 28 [0176] 214
Engagement point of the piezoactuator 204 on the load connection
element 28 [0177] 216 Pretensioning device [0178] 218 Pretensioning
device [0179] 230 Piezoactuator [0180] 232 Engagement point of the
piezoactuator 230 on the base connection element 10 [0181] 234
Engagement point of the piezoactuator 230 on the load connection
element 28 [0182] 236 Piezoactuator [0183] 238 Engagement point of
the piezoactuator 236 on the support element 180 [0184] 240
Engagement point of the piezoactuator 236 on the load connection
element 28 [0185] 242 Piezoactuator [0186] 244 Engagement point of
the piezoactuator 242 on the support element 210 [0187] 246
Engagement point of the piezoactuator 242 on the load connection
element 28 [0188] 260 Variable voltage source [0189] 262 Switch
[0190] 264 First electrode of the piezoceramic element 268 [0191]
266 Second electrode of the piezoceramic element 268 [0192] 268
Piezoceramic element [0193] 270 Measuring device [0194] 280
Combined unit composed of piezoceramic elements of the
piezoactuator 16 [0195] 282 Terminal of the unit 280 near to the
base connection element 10 [0196] 284 Terminal of the unit 280 near
to the load connection element 28 [0197] 286 Ohmic resistor [0198]
288 Inductor
* * * * *