EP1409889A1

EP1409889A1 - Method and damping device for absorbing an undesired vibration

Info

Publication number: EP1409889A1
Application number: EP01967013A
Authority: EP
Inventors: Jens Hofschulte; Norbert Scherm
Original assignee: Leibniz Universitaet Hannover
Current assignee: Leibniz Universitaet Hannover
Priority date: 2000-08-31
Filing date: 2001-08-29
Publication date: 2004-04-21
Also published as: JP2004507689A; DE10043128C2; WO2002018815A1; DE10043128A1; US20040041316A1

Abstract

The invention relates to a method and a damping device (1) for absorbing an undesired vibration, in particular, a tremor or an oscillation. According to said method, a base (2) is decoupled from the vibration, by means of a positioning actuator (10). A control unit (9) registers a relative displacement of the foot (4) and a mass (6) caused by the vibration, as a deflection of a spring element (5) that links the foot (4) to the mass (6). There is thus no need for a reference system that acts independently of the vibration to control the positioning actuator (10), allowing the damping device (1) to be produced at relatively low cost. The time-delayed transfer from the spring element (5) to the mass (6) is also exploited, to counteract the vibration before it has an undesired effect on the base (2).

Description

Method and device for absorbing unwanted excitation

The invention relates to a method for absorbing an unwanted excitation, in particular a vibration or an oscillation, the excitation being detected by a sensor and a signal for a displacement actuator being generated by means of a control unit, so as to avoid transmitting the excitation to a base. Furthermore, the invention relates to a device for performing the method.

Such a method and a device provided for this purpose are used in practice to keep disturbing vibrations away from sensitive technical devices. Ground vibrations or vibrations caused by airborne noise are particularly disruptive. Impairments caused by this can be found, for example, in measurement and laser technology, as well as in hard disks of data storage systems (head crash), or in the noticeable limitation of driving comfort for a passenger of a motor vehicle.

Other typical areas of application for absorber devices are the shielding of sensitive sensors, in particular in test arrangements or inertially stabilized systems in the field of defense or surveillance technology and when used for the transport of dangerous goods or ambulances, as well as in general to increase comfort when transporting people.

Technical systems are often protected against vibrations with the help of springs. Such passive systems are inadequate in particular due to their transmission behavior in the case of low-frequency interference.

For high-precision systems, absorber devices are used in which the vibration is detected by acceleration sensors and compensated for by the displacement actuator. However, this method is usually unsuitable at high frequencies because the displacement actuator has an upper limit frequency. The working range of the arrangement is thus limited by the bandwidth of the travel actuator. In the known devices, the problem arises in particular that the undesired excitation is only detected by the sensor on the base which supports the body, for example the body of a motor vehicle. Before the displacement movement, which is suitable for compensation, can be initiated by the displacement actuator, the shock can already be felt by the occupant, so that the influence of the vibration can be restricted but not prevented with such a device. DE 197 25 770 A1 also discloses a device in which an additional mass is connected elastically to the system to be damped by means of a displacement actuator for damping over an enlarged frequency range. The displacement actuator is intended to generate forces between the elastic system and the mass of the absorber device in addition to the mass on the system, so that vibration energy is extracted from the system. A disadvantage here is the comparatively high outlay which is associated with the detection of the excitation and the control of the mass by the displacement actuator.

From US 45 31 699 it is also known to be an active absorber device in which disruptive vibrations are kept away from the base by moving the displacement actuator with the same deflection in the opposite direction to the vibration, while a spring element stabilizes the base.

JP 22-25 839 already discloses an absorber device in which an acceleration sensor detects a filtered area of the excitation. The signal detected in this way is then converted into an opposite input signal for a piezo actuator, so that the vibrations can cancel each other out.

Furthermore, US Pat. No. 4,566,118 describes a method for vibration damping in which excitation in a specific area is canceled out by generating a second excitation synchronized with the first excitation. A vibration sensor with a filter is used for this.

In addition, DE 196 21 700 A1 also discloses an active vibration reducer with a controllable magnetic bearing to achieve a desired damping effect.

Regardless of the large number of known and commonly used damper devices, the problem that has so far been unsolved in combating undesired excitation is that an acceleration sensor or a reference system is required in order to be able to produce a signal for the displacement actuator by means of an adjustment. However, such a reference system that is not influenced by the excitation can only be implemented with great effort. The invention has for its object to absorb the unwanted excitation without the need for a complex reference system. At the same time, the efficiency of the process is to be increased. Furthermore, a device for performing the method is to be created.

The first-mentioned object is achieved according to the invention with a method according to the features of patent claim 1.

According to the invention, therefore, a method is provided in which the excitation is initially introduced into a mass and transmission of the excitation from the mass to the base is prevented by the sensor detecting a relative movement between the mass and the excitation, and from this for the displacement actuator certain signal is generated for a movement opposite to the mass. As a result, the excitation initially acts only on the mass, a relative movement between the initiated movement and the mass, which is essentially based on the inertia, being detected by the sensor. The transmission of this excitation, which acts on the mass, to the base is prevented by means of the displacement actuator by initiating a countermovement in good time. Because the excitation initially acts only on the mass with a delay, the displacement actuator can be controlled in such a way that transmission of the excitation to the base is counteracted in good time so that it can be kept in complete calm. As a result, the excitation is not only weakened, but is even balanced before an undesirable influence on the base, so that a transfer from the mass to the base is excluded.

An embodiment of the method according to the invention is particularly advantageous in which the deflection of a spring element which transmits the excitation to the mass is detected in order to determine the relative movement. This will cause excitement

deformation caused by the spring is detected in order to determine a signal for the displacement actuator by means of the sensor by the control unit. In particular, compared to an acceleration sensor required according to the prior art, only a displacement sensor is required, so that, in addition to a lower manufacturing outlay, an improvement in the efficiency with low-frequency vibrations is also achieved, which can be detected by an acceleration sensor with only unsatisfactory accuracy. For this purpose, the spring element can be arranged on a receptacle, for example that in this way the relative movement between the receptacle and the mass can be detected as a distance changed by the excitation.

Another advantageous modification of the present invention is provided by detecting the relative speed between the mass and the excitation. As a result, a speed sensor known from the prior art can be used in a simple manner, by means of which the relative speed between the mass and a receptacle moved by the excitation is determined. The measured value recorded in this way is converted into a corresponding manipulated variable for the displacement actuator, so that the excitation has no effect on the base.

Another advantageous modification of the method according to the invention can be achieved in that the sensor detects a relative rotary movement between the mass and the excitation. In this way, an undesired torsional vibration can be prevented by the same method. In this case, the excitation acts on the mass, for example by means of a torsion spring, the relative rotational speed or the relative rotational angle of which is detected by the sensor and then serves as an input signal for the displacement actuator designed for this purpose as an angle actuator.

The second-mentioned object, an absorber for absorbing unwanted excitation, in particular a vibration or a vibration, with a base supporting a structure, the distance of which from a mass movable by the excitation, arranged between the base and the location, can be changed by means of a displacement actuator, and with one Control unit by means of which a signal for the displacement actuator can be generated from a measured variable detected by a sensor, the mass being arranged to be movable relative to the location of the undesired excitation and this relative movement can be detected by the sensor and from this a signal intended for the displacement actuator can be generated is to create the method is achieved according to the invention in that the excitation can first be introduced into the mass and a transmission of the excitation from the mass to the base is prevented by a movement opposite to the mass. This makes it possible to dispense with a complex reference system, since knowledge of the absolute position of the mass influenced by the excitation is unnecessary. For the detection of a signal by the sensor, only the relative movement of the excitation as a disturbing movement and the resulting, possibly delayed movement of the mass is determined. This relative movement can be determined with much higher accuracy than through a conventional acceleration sensor. At the same time, the damper device thus constructed can be realized with comparatively simple technical means.

A particularly advantageous development of the present invention is created in that the mass can be moved by the excitation by means of a spring element. As a result, the disturbing movement associated with the excitation is transmitted to the mass only by the spring element. This results in a deformation of the spring element corresponding to the spring constant, from which the relative movement between a receptacle of the spring facing away from the mass and the mass can be derived.

For this purpose, the relative speed can be detected during the deflection of the spring element in order to determine the corresponding signal for the travel actuator by means of the control unit. Another particularly advantageous embodiment of the present invention is achieved, however, in that the deflection of the spring element can be detected. As a result, only the distance between a base point and a fixed point of the spring element connected to the ground, which is changed by the excitation, is determined in order to calculate the force acting on the excitation by means of the control unit.

Another particularly advantageous embodiment of the absorber device is also created in that the mass is arranged to be relatively movable relative to the excitation by means of a magnetic field. As a result, the position of the mass can be predetermined via a control system, so that contactless positioning is achieved. The precision of the control can be increased further because the system parameters required for this can be reproduced with a high degree of accuracy. The excitation is recorded as a change in the parameters of the magnetic field or as a change in the position of the mass.

For this purpose, it is also particularly favorable if the displacement actuator has a controllable magnetic bearing. Appropriate control of the travel actuator designed in this way enables a rapid and precise movement to be achieved, by means of which the base can be kept free of the undesired excitation. The parameters of the magnetic bearing, which are known per se, can be processed precisely with the aid of the control, so that a further increase in efficiency can be achieved. Another, also very advantageous embodiment of the invention is achieved in that the mass is rotatably arranged and a relative rotational movement between the mass and the excitation can be detected by the sensor. In this way, an absorber device for a torsional vibration or excitation is created, by means of which, for example, the vibrations occurring in motors can be compensated in a simple manner. For this purpose, a torsion spring can be used, by means of which the mass can be kept movable in a predetermined rest position with respect to the excitation.

A particularly effective modification of the present invention is achieved in that the relative angle of rotation between the mass and the excitation can be detected by the sensor. As a result, the relative movement between the mass and the excitation can be detected with an accuracy that cannot be achieved by a conventional acceleration sensor. A reference system is not required. At the same time, it is also conceivable to provide a magnetic field instead of a spring element, as a result of which, in particular, undesirable influences of friction can be avoided.

A further, particularly expedient embodiment of the present invention is achieved in that the damper device has a plurality of displacement actuators acting on a common basis, each with an associated sensor. As a result, different excitations introduced at different sub-areas of the base can be detected and a reliable compensation of the position or a position stabilization can be achieved by the individual displacement elements.

The high sensitivity of the speed sensor also opens up other fields of application. Since the movement of the lower mass can be reconstructed by the absorber device, the form of excitation can also be determined with the aid of an expanded control. This allows the relative movement of the foundation to be determined. The acceleration of the excitation can also be determined by differentiating the signal from the speed sensor. An acceleration sensor implemented in this way has a higher sensitivity with a reduced manufacturing outlay than the sensors known from the prior art.

The invention allows various embodiments. To further clarify its basic principle, one of these is shown in the drawing and is described below. This shows in 1 shows a damper device according to the invention in a front view;

2 shows a circuit diagram of the absorber device;

3 shows a further absorber device with a magnetic bearing in a schematic diagram.

FIG. 1 shows a front view of an absorber device 1 with a base 2 which is intended for a structure which is not shown and which is to be protected against undesired excitation, for example a vibration or an oscillation. The excitation acts via a foundation 3 on a receptacle 4 (foot) of the absorber device 1, which is thereby moved vertically by an unknown distance. By means of a spring element 5, the force caused by the excitation is transferred to a mass 6, the column 7 of which is essentially free to move both upwards and downwards in the receptacle 4. The action of force leads to a deflection of the spring element 5, which can be detected by means of a sensor 8 as a relative movement between the column 7 and the receptacle 4. The measured variable obtained in this way is then converted by means of a control unit 9 into a signal for a displacement actuator 10 connected to the mass 6, which permits a vertical change in length. This change in length corresponds to its magnitude after excitation, with its direction of movement being opposite. Therefore, the excitation acts on the mass 6, but is compensated by the displacement actuator 10 in such a way that a reaction to the base 2 is excluded. For this purpose, the travel actuator 10 is equipped with a connecting means 11 designed as a spring element in order to counteract a possible reaction of the base 2 to the mass 6.

The spring element 5 permits a movement of the mass 6 which deviates from the excitation. The deflection of the spring element 5 which occurs here is detected by the sensor 8 and converted by means of the control unit 9 into a signal for the displacement actuator 10, a reference system, in particular for determining the relative arousal position, is not required. Due to the relative movement of the mass 6 which is delayed compared to the excitation, the compensating movement can be initiated by the displacement actuator 10 before the excitation is felt at the base 2.

The exact mode of operation is explained in more detail with reference to FIG. 2, which shows a circuit diagram of the damper device 1. First of all, the vertical fault 12 is shown Excitement. This acts on the mass 6 via a spring-damper system 13 corresponding to the spring element 5 shown in FIG. 1 or the column 7 movable in the receptacle 4 idealized equation of motion of the spring-damper system 13 is calculated as an input variable for the travel actuator 10 represented here only by its functional equation. The displacement actuator 10 thus sets a time-dependent correction distance 14 between the base 2 and the mass 6 that corresponds to the amount of the disturbance 12, so as to avoid the disturbance 12 acting on the base 2.

The generation of the signal for the travel actuator 10 is both time-discrete and continuously conceivable. A complete, exact replication of the unloaded spring-mass system over the entire frequency band is not absolutely necessary if the practical requirements do not require such high accuracy.

FIG. 3 shows a further absorber device 15, in which a mass 16 is held in a hanging arrangement in a predetermined rest position by a magnetic bearing 17. Excitation is detected as a change in the parameters of the magnetic field, whereby the relative movement between the mass 16 and a receptacle 18 can be determined. From this, a control variable for a displacement actuator 19, which is also designed as a magnetic bearing, is then calculated in order to be able to initiate a countermovement. A base 20 of the damper device 15 is therefore unaffected by the unwanted excitation and decoupled.

Claims

claims

1. A method for absorbing an undesired excitation, in particular a vibration or an oscillation, the excitation being detected by a sensor and a signal for a displacement actuator being generated by means of a control unit, so as to avoid transmitting the excitation to a base, characterized in that that the excitation is initially introduced into a mass and transmission of the excitation from the mass to the base is prevented by the sensor detecting a relative movement between the mass and the excitation and from this the signal intended for the displacement actuator for a movement opposite to the mass is produced.

2. The method according to claim 1, characterized in that the deflection of a spring element transmitting the excitation to the mass is detected.

3. The method according to claims 1 or 2, characterized in that the relative speed between the mass and the excitation is detected.

4. The method according to at least one of the preceding claims, characterized in that a relative rotary movement between the mass and the excitation is detected by the sensor.

5. absorber device (1, 15) for absorbing an undesirable excitation, in particular a vibration or vibration, with a base supporting a structure (2, 20), the distance from which is movable by the excitation, between base (2, 20) and the location (foundation 3) of the mass (6, 16) arranged can be changed by means of a displacement actuator (10, 19), and by means of a control unit (9) by means of which a signal for the Position actuator (10, 19) can be generated, the mass (6, 16) being arranged so as to be movable relative to the location (foundation 3) of the undesired excitation and this relative movement can be detected by the sensor (8) and a signal intended for the position actuator can be generated therefrom characterized in that the excitation can initially be introduced into the mass (6, 16) and the excitation can be transmitted from the mass (6, 16) to the base (2, 20) by an opposite one to the mass (6, 16) Movement excluded is outside.

6. damper device (1) according to claim 5, characterized in that the mass (6) by means of a spring element (5) is movable by the excitation.

7. damper device (1) according to claim 6, characterized in that the deflection of the spring element (5) can be detected.

8. damper device (15) according to at least one of claims 5 to 7, characterized in that the mass (16) by means of a magnetic field relative to the excitation is arranged to be relatively movable.

9. damper device (15) according to at least one of claims 5 to 8, characterized in that the displacement actuator (19) has a controllable magnetic bearing.

10. damper device according to at least one of claims 5 to 9, characterized in that the mass is arranged rotatably and a relative rotational movement between the mass and the excitation can be detected by the sensor.

11. absorber device according to claim 10, characterized in that the relative angle of rotation between the mass and the excitation can be detected by the sensor.

12. Damper device (1, 15) according to at least one of claims 5 to 11, characterized in that the damper device (1, 15) has a plurality of displacement actuators (10, 19), each acting on a common base (2, 20) assigned sensor (8).