Rotation rate sensor

A rotation rate sensor having a substrate and a Coriolis element is proposed, the Coriolis element being situated above a surface of a substrate; the Coriolis element being able to be induced to vibrate in parallel to a first axis (X); an excursion of the Coriolis element being detectable, based on a Coriolis force in a second axis (Y), which is provided to be essentially perpendicular to the first axis (X); the first and second axes (X, Y) being provided parallel to the surface of the substrate, wherein force-conveying means are provided, the means being provided to convey a dynamic force effect between the substrate and the Coriolis element.

FIELD OF THE INVENTION

The present invention relates to a rotation rate sensor.

BACKGROUND INFORMATION

Linearly vibrating vibration gyroscopes are generally known. In these rotation rate sensors, parts of the sensor structure are actively set into vibration (primary vibration) in one direction, i.e. in a first axis (x axis), which is oriented parallel to a substrate surface. At an outer rotation rate about a singular sensitive axis, Coriolis forces are exerted on the vibrating parts. These Coriolis forces, which vary periodically with the frequency of the primary vibration, give rise to vibrations of parts of the sensor structure (secondary vibration) that are also parallel to the substrate surface in a second direction or second axis (y axis) which is oriented perpendicular to the x axis. Means of detection are mounted on the sensor structure which detect the secondary vibration (Coriolis measuring effect).

In the lay-out of the rotation rate sensor, as described above, by design (choice of suitable symmetries) a singular cartesion coordinate system, K=(x,y) is specified for the primary and the secondary vibration within the plane of the substrate. The mass distributions and the spring distributions are laid out so that the main axis system of the mass tensors and spring stiffness tensors for the primary and secondary vibrations coincide exactly with K. In addition, in the implementation of the means of detection, care is taken that no signals are created at the means of detection for the Coriolis effect by the operation of the sensors in the primary vibration (without external rotation rate). For this purpose, the means of detection are designed so that their singular coordinate system KD also coincides with the coordinate system of the mechanics K, i.e. it is also true that KD=(x,y). Consequently, in the case of such ideal vibration rate sensors, there is not created a bridging of the primary vibration to the detection device for the Coriolis effect. Such a bridging is called a quadrature. Thus, quadrature signals are signals to the means of detection for the Coriolis effect, which are present also without a relative motion of the sensor with respect to an external inertial system, the sensor being operated in its primary vibration.

The quadrature leads to periodic signals, modulated with the frequency of the primary vibration, to the means of detection for the Coriolis effect.

The reason for the appearance of quadtature signals is that the coordinate system of the sensor element mechanics K=(x,y) does not coincide with the coordinate system of the means of detection KD=(x′,y′) but both systems are slightly rotated with respect to each other by an angle theta.

Typical causes for this rotation, which is generally slight, are, for example, asymmetries in the sensor structure by reason of imperfections in the manufacturing process. These are able to make themselves known by asymmetrical mass distributions or asymmetrical spring constants. As a result of this, the main axis systems of the mass tensors and the spring constant tensors no longer coincide with KD.

The appearance of quadrature is not specific for the silicon technology used for the rotation rate sensors described here, having a sensor structure made of epitactically grown polysilicon. Even in rotation rate sensors made of monocrystalline silicon material or with monocrystalline quartz, quadrature signals appear as a result of imperfections in the manufacturing process.

Another interpretation of the quadrature signals, important to an understanding of the present invention, is based on an observation with respect to interference theory: For a small twisting of the coordinate systems one may initially regard the directions of the main axis systems as interference free (K=KD). In this representation, the quadrature is described as s slight coupling of the two essential vibration modes (primary and secondary vibrations). In this representation, during the vibration of the sensor structure in primary mode, the quadrature leads to an inducement of the secondary vibrations, even without external rotation rate. This motion becomes visible as an interference signal at the means of detection for the Coriolis effect.

According to the present invention, based on the well-directed effect of time-wise periodically varying forces, a reduction or avoidance of quadrature signals is achieved. For this, electrostatic forces that vary in time (dynamic) are exerted on the sensor structure by electrode structures applied at suitable parts of the sensor structure and by the purposeful application of external electrical dc voltages. It is achieved particularly by the suitable form of the electrode structures (quadrature compensation structures) that, during the primary vibration of the sensor structures, forces varying in time act upon suitable parts within the sensor structure. These forces are oriented in such a way that they induce secondary vibrations, and may consequently be detected at the means of detection of the Coriolis effect. Because of the height of the electrical voltage, the magnitude of these signals may be varied until they exactly compensate the quadrature signals present in the sensor element because of imperfections. Consequently, the present invention represents a dynamic method for quadrature compensation.

The effect of the quadrature compensation is based, in the method according to the present invention, on a purposefully undertaken asymmetry within the mechanical sensor structure.

Quadrature interference signals in rotation rate sensors as a result of manufacturing imperfections are known, and are encountered in rotation rate sensors of the most varied technologies. In this context, according to the related art, various different methods are known for the reduction of these interference signals.

A first method, according to the related art, for suppressing quadrature signals makes use of the different phase position of rotation rate signals and quadrature signals. The Coriolis force is proportional to the speed of the primary vibration, whereas the quadrature is proportional to the excursion of the primary vibration. Consequently, there is a phase shift of 90° between the rotation rate signal and the quadrature signal. At the means of detection, quadrature signals and rotation rate signals are detected as signals amplitude-modulated with the frequency of the primary vibration. By the method of synchronous demodulation, as described, for example, in German Published Patent Application No. 197 26 006 and U.S. Pat. No. 5,672,949, the signals may first of all be demodulated again into the baseband. In addition, by a suitable choice of the phase position of the reference signal for the demodulation, the quadrature signal may be suppressed.

In this method, the quadrature signal is not influenced in the sensor element itself. Furthermore, the quadrature signal also has to pass through the primary signal conversion paths in the means of detection, and it is able to be electronically suppressed only relatively late in the signal path. In the case of large quadrature signals compared to the rotation rate measuring range, this means drastically increased requirements on the dynamic range of the first signal conversion stages, and often leads to increased sensor noise.

A second method according to the related art, for reducing quadrature signals, is the physical balancing of the mechanical sensor structures. Here, in contrast to the first method, the cause of the quadrature is directly rectified by reworking the sensor element, so that no quadrature signals appear at the means of detection. In the case of precision rotation rate sensors, this is achieved actively by iterative mechanical material surface removal at different places in the sensor element. Using this method, the principal axis system of the mass or spring constant tensors for the primary and secondary vibrations are modified so that the twisting of the coordinate system of the sensor element mechanics K with respect to the coordinate system of the means of detection KD, which is present at first, is reversed. In the case of rotation rate sensors made of monocrystalline quartz material, a surface removal of material is undertaken partially by laser trimming at singular locations in the sensor element. Here too, the mass tensor or spring constant tensor is modified so that, at the end, the twisting of K with respect to KD is essentially reversed. Even in the case of micromechanical rotation rate sensors made of monocrystalline silicon, laser trimming is used on mass structures (e.g. VSG or CRS-03 from Silicon Sensing Systems Ltd.). Furthermore, for general tuning fork rotation rate sensors, laser trimming at singular spring structures within the sensor structure is generally known. Using this method, in the operation of the sensor elements in primary vibration, the principal axis system of the spring constant tensor is able to be modified until K and KD coincide, and thus the quadrature signal is eliminated. The methods described here eliminate the quadrature in the sensor element itself, and are therefore superior to the first method, with respect to sensor performance. However, the balancing (procedure) represents a costly and often iterative as well as tedious process, and thereby a very cost-intensive process.

According to a further generally known method according to the related art, an electronic quadrature compensation is carried out in capacitive micromechanical rotation rate sensors. By doing this, the suppression of the quadrature signal is accomplished by the targeted injection of an electrical signal into the electronic transducer unit at the means of detection for the Coriolis effect. For this, the magnitude of the signal is selected so that it exactly compensates for the signal generated by the quadrature at the means of detection. In this method too, (analogous to the first method according to the related art), the mechanical cause for the quadrature signal itself is not eliminated. However, in contrast to the first method, in this case the quadrature signal is suppressed even before the primary signal conversion. This is able to reduce the requirements on dynamic range and noise of the primary signal conversion. However, a serious disadvantage of the method described is that it is suitable only for a very special design of the sensor evaluation electronics. This evaluation method (baseband evaluation), however, has serious disadvantages conditioned on principle (electrical distortion, etc), and therefore cannot be used in rotation rate sensors described in the present invention.

In U.S. Pat. No. 6,067,858, a further method according to the related art for electronic quadrature compensation in capacitive micromechanical rotation rate sensors is discussed. Between movable comb fingers and fixed electrodes, different electrical potentials are applied.

SUMMARY OF THE INVENTION

The rotation rate sensor according to the present invention has the advantage over the related art that, by using a special method, based on the targeted action of static forces, a reduction in the quadrature signals is achieved. In this context, electrostatic forces that are either changeable over time (dynamic) or changeable over time (dynamic) and constant over time (static) are exerted on the sensor structure by electrode structures applied at suitable parts of the sensor structure and by the purposeful application of external electrical dc voltages. By the suitable application of the electrode structures (quadrature compensation structures) it is achieved that the quadrature is reduced or compensated for. Consequently, the present invention represents a method for quadrature compensation using dynamic and optionally additional static forces. In this connection, the forces are generated by electrode structures applied to singular parts of the sensor structure, in such a way that an external electrical dc voltage is applied to electrodes suspended fixedly with respect to the substrate as opposed to the movable sensor structure. The method according to the present invention acts similarly to a mechanical balancing of the sensor structure. However, compared to the physical balancing, it has the advantage that the compensation is able to be carried out here by applying an external voltage (by balancing), and consequently a costly process step may be omitted.

Moreover, the method is compatible with all conceivable sensor evaluation electronics.

DETAILED DESCRIPTION

A possible embodiment of the method according to the present invention for dynamic quadrature compensation is shown below, using as the example a micromechanical rotation rate sensor. The method may be applied to a special class of rotation rate sensors. In this context, this involves linearly vibrating vibration gyroscopes. An exemplary embodiment of the present invention is explained below, first of all the essential functional components of the rotation rate sensor being briefly described in the light of the rough illustration ofFIG. 1, for an understanding of the procedure of the present invention.

FIG. 1shows the top view of the structured parts or rather, the structure of a rotation rate sensor or a rotation rate sensor element, the substrate lying under the particularly micromechanically structured structure of the rotation rate sensor being not shown in greater detail, for reasons of clarity.

Silicon is preferably used as the material for the substrate and for the sensor elements situated above the substrate, and it is developed to be conductive by appropriate doping. The substrate may be electrically insulated where it is necessary using insulating layers. However, other materials such as ceramic, glass or metals may also be used for the rotation rate sensor according to the present invention.

The rotation rate sensor shown inFIG. 1is designed according to the present invention particularly for production using pure surface micromechanics. What is sensed is a rotation about the normal to the substrate (the z axis), i.e. an axis which is perpendicular to the substrate surface, and which will from here on also be denoted as the third axis. According to the present invention, all movable parts of the structure are essentially completely load conducting, i.e. electrically conductive.

According to the present invention, the sensor structure includes especially two preferred, symmetrically designed partial structures, which are shown in the left and right parts ofFIG. 1and are denoted as reference marks50aand50b. However, according to the present invention it is also possible that the sensor structure according to the present invention includes only one such partial structure50a. Each of the partial structures50a,50bincludes three individual masses that are movable with respect to the substrate with which the reference coordinate system is connected. In this connection, there is provided inside the partial structures in each case a first mass as driving mass1a,1b. It is suspended on the substrate with springs5a,5busing anchoring means18a,18bin such a way that the driving mass can preferably execute only one in-plane motion (parallel to the plane of the substrate) in a first direction, or rather, according to a first axis (the x axis), and an in-plane motion in a second axis (the y axis), which is perpendicular to the first axis, is suppressed. For this purpose, springs18a,18bare flexible in the x direction and rigid in the y direction. The first axis is also called driving axis X; the second axis is also called detection axis Y.

Furthermore, within partial structures50a,50b, a third mass, which from here on will also be called detection element3a,3b, is suspended using springs6a,6bin such a way with respect to the substrate that preferably it can execute an in-plane motion only in detection direction Y, and a motion in driving direction X is suppressed. For this purpose, springs6a,6bare flexible in the Y direction and rigid in the X direction.

Within partial structures50a,50b, in each case a second mass is connected as a Coriolis element2a,2bto the first mass1a,1band the third mass3a,3bby springs7a,7b,8a,8bin such a way that Coriolis element2a,2bis able preferably to execute an in-plane relative motion only in the detection direction, and a relative motion in the driving direction is suppressed, and that Coriolis elements2a,2bis able preferably to execute an in-plane relative motion only in the x direction, and a relative motion in the y direction is suppressed, so that Coriolis element2a,2bis able to execute both a motion in the driving direction and the detection direction. For this purpose, springs7a,7bbetween Coriolis element2a,2band detection element3a,3bare provided flexible in the X direction and rigid in the Y direction. Springs8a,8bbetween Coriolis element2a,2band driving mass1a,1bare provided flexible in the y direction and rigid in the x direction.

Driving mass1a,1b, Coriolis element2a,2band detection element3a,3bare denoted from here on in common also as movable sensor elements1a,1b,2a,2b,3a,3b, since they have a certain movability with respect to the substrate that is limited by the spring elements. Sensor elements1a,1b,2a,2b,3a,3bare particularly provided, according to the present invention, as essentially rectangular, frame-shaped structures, Coriolis element2a,2bsurrounding detection element3a,3b, and driving mass1a,1bsurrounding Coriolis element2a,2b.

In one sensor structure according to the present invention, having two partial structures50a,50b, the two Coriolis elements2a,2bare connected by springs11so that a direct mechanical coupling of both partial structures50a,50bis present, both in the driving and the detecting direction, in such a way that the formation of parallel and antiparallel vibration modes in the x direction takes place (with participation of driving masses1a,1band Coriolis elements2a,2b) (effective modes drive, primary vibration) and that the formation of parallel and antiparallel in-plane vibration modes in the y direction takes place (with the participation of Coriolis element2a,2band detection elements3a,3b) take place (effective modes detection, secondary vibration).

The inducement or rather, the drive of the structure (primary vibration) preferably takes place in the antiparallel driving mode (first mass1aof first partial structure50amoves in phase opposition to first mass1bof second partial structure50b). The Coriolis accelerations appearing about the z axis at an external rotation rate about the z axis are then also in phase opposition, and if there is an appropriate design of the structures, this leads to an activation of the antiparallel detection mode (secondary vibrations). The desired measuring effect generated thereby may then, by a suitable evaluation, be directly distinguished from an (undesired) measuring effect, brought on by external linear accelerations in the y direction, which would act in phase on the detection of both partial structures.

The inducement of the primary vibration takes place at drive masses1a,1bvia interdigital comb drives; also the detection of the driving motion. For this, according to the present invention, a first electrode12a,12b, and a second electrode13a,13bare provided, which generate the primary vibrations. First electrode12a,12bis provided rigidly connected to the substrate but electrically insulated. Second electrode13a,13bis connected to driving mass1a,1bmechanically rigid and electrically conductive. First electrode12a,12band second electrode13a,13b, in this situation, reach into each other, finger-like, and thus form a comb structure. Consequently, when a voltage is applied between the electrodes it is possible to exert a force from the substrate on driving mass1a,1b.

The detection of the Coriolis acceleration takes place at means of detection particularly in the form of third and fourth electrodes inside detection elements3a,3b. Detection element3a,3bis designed for this purpose in such a way that it forms the fourth electrode as the movable part16a,16bof a plate capacitor device. A fixed part15a,16bof the plate capacitor device is denoted as the third electrode, and it is connected to the substrate in a mechanically rigid (but electrically insulated) fashion. In this context, the fixed part15a,15bis designed as a split-up electrode, so that the whole system forms a differential plate capacitor.

In the sensor structure, detection takes place at a structure at rest (detection at rest). This specifies that detection element3a,3b, and consequently movable electrode16a,16bof the plate capacitor system, essentially does not execute a driving motion. By the subdivision of partial structures50a,50bof the rotation rate sensor into driving mass1a,1b, Coriolis element2a,2band detection element3a,3bone achieves a two-fold decoupling of the detection motion from the driving motion.

InFIG. 2, left partial structure50afromFIG. 1of a rotation rate sensor according to the present invention is shown in a detailed view. For reasons of clarity, in this case only one partial structure (the left one) of the sensor element is shown.

In the layout of the rotation rate sensor, by design (choice of suitable symmetries) a singular cartesian coordinate system, K=(x,y) is specified for the primary and the secondary vibration within the plane of the substrate. The mass distributions and the spring distributions should ideally be laid out so that the main axis system of the mass tensors and spring stiffness tensors for the primary and secondary vibrations coincide exactly with K. In addition, in the implementation of the means of detection, care is taken that no signals are created at the means of detection for the Coriolis effect by the operation of the sensors in the primary vibration (without external rotation rate). For this purpose, the means of detection are designed so that their singular coordinate system KD also coincides with the coordinate system of the mechanics K, i.e. it is also true that KD=(x,y).

When the coordinate systems K and KD do not completely coincide, for instance, because of manufacturing fluctuations, quadrature signals may appear.

There is a difference made between positive and negative quadrature signals, with respect to the Coriolis measuring effect: when left partial structure50ainFIG. 2moves in primary vibration in the positive x direction, and a positive external rotation rate about the z axis, the Coriolis acceleration acts in the negative y direction. A positive quadrature signal acts in the same direction, and a negative quadrature signal acts in the opposite direction.

In the rotation rate sensor according to the present invention, because of electrode structures applied at suitable parts, especially Coriolis element2a,2b, of the sensor structures, by purposeful application of external electrical dc voltages, electrostatic forces changeable over time (dynamic), possibly superimposed by forces that are constant over time (static), are exerted on the sensor structure. By the suitable application of these electrode structures, which from here on are also denoted as quadrature compensation structures or as compensation structures, it is achieved that, during the primary vibration of the sensor structure, forces varying over time are exerted on suitable parts within the sensor structure. These forces are oriented in such a way that they induce secondary vibrations, and may consequently be detected at the means of detection of the Coriolis effect. Because of the height of the electrical voltage, the magnitude of these signals may be detected until they exactly compensate the quadrature signals present in the sensor element because of imperfections of the sensor structure. Consequently, the present invention represents a dynamic method for quadrature compensation.

InFIG. 2and the subsequent figures dynamic quadrature compensation structures19,20are shown as an example within Coriolis element2a. According to the present invention, the compensation structures are provided in the form of two substructures, one first substructure19compensating for the positive quadrature signal, and a second substructure compensating for the negative quadrature signals. Such two substructures make sense, particularly because, since, according to the present invention, electrostatic forces varying over time are exerted, especially attractive forces, then a rotation of coordinate system K is able to be effected both in the positive and in the negative direction.

InFIG. 3, detailed views of compensation structures19,20are shown as an example of their implementation at Coriolis element2a.

InFIGS. 2 and 3, especially compensation structures19,20are shown in a detailed view, for a first exemplary embodiment of the rotation rate sensor according to the present invention. In the first exemplary embodiment, compensation structures19,20differ according to whether they are located on a first side of Coriolis element2a, which inFIG. 2is shown in the upper part of the figure, or whether they are located on a second side of Coriolis element2a, InFIGS. 2 and 3, the first side is denoted by reference numeral61and the second side is denoted by reference numeral62.

FIG. 3ashows compensation structures19,20with Coriolis element2awithout excursion of Coriolis element2afrom its equilibrium position (i.e. the displacement of Coriolis element2ain the X direction vanishes), i.e. X=0.FIG. 3bshows compensation structure19,20with Coriolis element2aand having an excursion of Coriolis element2afrom its equilibrium position in the positive X direction, i.e. X=+Xo.FIG. 3cshows compensation structure19,20with Coriolis element2ahaving an excursion of Coriolis element2afrom its equilibrium position in the negative X direction, i.e. X=−Xo.

Each of substructures19,20of the compensation structure is, according to the present invention, provided in particular as a capacitor device having a fifth electrode and a sixth electrode provided. Suitable regions60are cut out from Coriolis element2a, which will be denoted as cutouts60below.

According to the present invention it is provided in all specific embodiments of the rotation rate sensor that each cutout60has a greater extension in a first cutout region65in the direction of second axis (y) than in a second cutout region66. Cutout regions65,66, according to the present invention, are each particularly provided to be rectangular, they being provided particularly in such a way that one side of the rectangles of cutout regions65,66are provided to be equally long, and that the other side of the rectangles of cutout regions65,66are provided to be of different lengths. According to the present invention, cutout regions65,66are particularly positioned so that the equally long sides of second cutout regions65,66run parallel and especially along the first axis X, as well as that in the direction of the first axis X they “abut” each other in such a way, i.e. in the direction of the X axis they are positioned adjacent to each other in such a way that together they form cutout60.

Moreover, in all specific embodiments of the present invention, the sidewalls of cutouts60in each case form sixth electrode19b,20bof electrostatic compensation structure19,20. With respect to first cutout region65and second cutout region66of a cutout60, sixth electrode19b,20b, in each of the cutouts, is divided in two, into a first partial electrode67and a second electrode68. In this connection, first partial electrode67is provided as the sidewall of first cutout region65and second partial electrode68is provided as the sidewall of second cutout region66. According to the present invention, cutout regions65,66are adjacent in the direction of the first axis, and, because of their different extension in the direction of second axis Y, they form a common sidewall69and, on the other of their sides, they form a stepped sidewall70. In cutouts60, counterelectrodes (plate capacitor structures)19a,20a, that are mechanically rigidly anchored to the substrate, are provided as the fifth electrode. According to the present invention, fifth electrodes19a,20aare particularly provided as plates, extending from the substrate into cutouts60, having in particular a rectangular-shaped cross section. According to the present invention, fifth electrodes19aand also fifth electrodes20aare in each case electrically connected to each other, especially via circuit-board conductors underneath the movable structures of the rotation rate sensor, fifth electrodes19a, however, being provided electrically insulated from fifth electrodes20a, however, they are designed to be electrically insulated from the substrate, so that at these electrodes19a,20aelectrical potentials desired may be applied from the outside with respect to the movable sensor structures.

According to the present invention, several positioning possibilities are provided so as to provide cutout regions65,66adjacent to each other to form a cutout60: The first possibility provides that first cutout region65follows second cutout region66in the positive direction of first axis X, the common sidewall69being provided on the side of the positive Y axis. InFIG. 3b, the first possibility is provided with reference numeral210. The second possibility provides that first cutout region65follows second cutout region66in the positive direction of first axis X, the common sidewall69being provided on the side of the negative Y axis. InFIG. 3b, the second possibility is provided with reference numeral220. The third possibility provides that first cutout region65precedes second cutout region66in the positive direction of first axis X, the common sidewall69being provided on the side of the negative Y axis. InFIG. 3b, the third possibility is provided with reference numeral230. The fourth possibility provides that first cutout region65precedes second cutout region66in the positive direction of first axis X, the common sidewall69being provided on the side of the positive Y axis. InFIG. 3b, the fourth possibility is provided with reference numeral240.

Furthermore, in all specific embodiments of the present invention it is provided that stationary fifth electrodes (19a,20a) are provided within the cut out regions in such a symmetrical way that fifth electrodes (19a,20a) are provided to be asymmetrical in first cutout region65. This means that fifth electrodes19a,20a, in first cutout region65are provided, with respect to second axis Y, closer to one of the two sidewalls69,70of first cutout region65than to the other of the sidewalls. With respect to the second cutout region, fifth electrodes19a,20aare provided to be essentially symmetrical to second cutout region66.

Now, cutout regions65,66are provided in the first exemplary embodiment in such a way that they are positioned for first compensation structure19of first side61of Coriolis element2aaccording to the first positioning possibility, and for second compensation structure20of first side61of Coriolis element2aaccording to the second positioning possibility. In the first exemplary embodiment it is also provided that cutout regions65,66are positioned for first compensation structure19of second side62of Coriolis element2aaccording to the third positioning possibility, and are positioned for second compensation structure20of second side62of Coriolis element2aaccording to the fourth positioning possibility. Thereby, in the position at rest of Coriolis element2a, static forces are exerted on Coriolis element2ain the y direction when external quadrature compensation voltages (electrical dc voltages) are applied between fifth and sixth electrodes19a.20a,19b,20b. According to the present invention, the magnitude of these forces may be changed, in particular continuously, via the dc voltage between the fifth and sixth electrodes. The direction of the forces is predefined by the asymmetry of the arrangement. These static forces already bring about a slight static quadrature compensation.

In this connection, according to the present invention, first substructure19shown inFIG. 3, for first side61is in a position to exert forces toward the right, which is shown in the upper part ofFIG. 3aby a short arrow pointing to the right in the region of a brace belonging to reference numeral19. According to the present invention, first substructure20, shown inFIG. 3, of first side61of Coriolis element2ais in a position to exert forces toward the left, which is shown in the upper part ofFIG. 3aby a short arrow pointing to the left in the region of a brace belonging to reference numeral20. Furthermore, according to the present invention, first substructure19for second side62of Coriolis element2a, shown inFIG. 3, is in a position to exert forces toward the left, which is shown in the lower part ofFIG. 3aby a short arrow pointing to the left in the region of a brace belonging to reference numeral19. According to the present invention, second substructure20of second side62, shown inFIG. 3, of Coriolis element2ais in a position to exert forces toward the right, which is shown in the lower part ofFIG. 3aby a short arrow pointing to the right in the region of a brace belonging to reference numeral20. Corresponding arrows in the other figures point to the action of force of the static forces.

By the suitable positioning of compensation structures19,20, it is achieved that, because of the static forces on Coriolis element2a, a torque about the center of gravity of the partial structure shown inFIG. 2and denoted by reference symbol S is generated, but that no linear force component in the y direction is present.

The torque on Coriolis element2a, just by the static forces, leads to a twisting of the sensor structure, and thereby also of the principal axis system of sensor element mechanics K, with reference to the substrate. In this context, the direction of twisting is different for the first and second compensation structure19,20.

Using this effect, twisting, predefined by production imperfections, etc, between the principal axis system of sensor element mechanics K and the principal axis system of detection means KD is now able to be partially reversed.

However, the central point of the present invention is the additional dynamic quadrature compensation effect appearing on account of the mechanical asymmetry within the compensation structures. During the motion of the sensor element in primary vibration at amplitude Xo, which is shown inFIGS. 3band3c, the areas swept over, between fifth electrodes19a,20aand first and second cutout regions65,66of cutouts60of Coriolis element2a, change. From this, there also result periodically changing, resulting forces in the y direction, which is shown by the long arrows shown inFIGS. 3band3c, as opposed to the short arrows mentioned above. Consequently, in the first arrangement possibility of cutout regions65,66, as was shown in first compensation structure19on first side61, in the case of an excursion of the Coriolis element in positive X axis, a dynamic force is generated in the positive Y axis (to the left), and in the case of an excursion of Coriolis element2ain negative X axis, a dynamic force is generated in the negative Y axis (to the right). In the case of the second arrangement possibility of cutout regions65,66, as was shown in second compensation structure20on first side61, in the case of a excursion of Coriolis element2ain positive X axis, a dynamic force is generated in the negative Y axis (to the right), and in the case of an excursion of Coriolis element2ain negative X axis, a dynamic force is generated in the positive Y axis (to the left). In the case of the third arrangement possibility of cutout regions65,66, as was shown in first compensation structure19on second side62, in the case of a excursion of the Coriolis element in the positive X axis, a dynamic force is generated in the positive Y axis (to the left), and in the case of an excursion of Coriolis element2ain negative X axis, a dynamic force is generated in the negative Y axis (to the right). In the case of the fourth arrangement possibility of cutout regions65,66, as was shown in second compensation structure20on second side62, in the case of an excursion of Coriolis element2ain the positive X axis, a dynamic force is generated in the negative Y axis (to the right), and in the case of an excursion of Coriolis element2ain the negative X axis, a dynamic force is generated in the positive Y axis (to the left).

Consequently, the entire effective force on Coriolis element2ais composed of a static proportion—short arrows—and a dynamic proportion—long arrows.

It is achieved, by the suitable orientation of the compensating structure, that the resulting effective dynamic force contributions with regard to positive and negative compensation point in opposite directions.

The dynamic force contribution is directly proportional to the excursion of the sensor structure in the primary vibration, and acts in the y direction. Consequently, it corresponds directly to a quadrature signal. Thus, for positive and negative quadrature signals in the sensor element, an electrical compensation voltage with respect to the movable sensor structure would be applied to one of the two compensation structures.

The magnitude of the dynamic force contribution, and thus the magnitude of the quadrature compensation may take place by variation in the electrical voltage applied

The positioning of the compensation structure on the second partial structure50bof the rotation rate sensor shown inFIG. 1is produced by a symmetry operation, for example, a rotation by 180° about the overall center of gravity Sg from first partial structure50b.FIG. 4shows the two partial structures50aand50b, and the overall center of gravity denoted by reference symbol Sg.FIG. 4also shows first side61and second side62, and the distribution of compensation structures19,20with respect to the two sides61,62. As was shown in connection withFIG. 3, from this there follows, for first partial structure50a, for first compensation structure19on first side61, the first possibility210, for second compensation structure20on first side61, the second possibility220, for first compensation structure19on second side62, the third possibility230and for second compensation structure20on second side62, the fourth possibility240. For second partial structure50b, there follow for the example of rotation by 180° as symmetry operation the same associations of compensation structures19,20and possibilities210,220,230,240with this difference, that on both sides61,62, first compensation structure19is not provided as in first partial structure50ato the left (positive Y direction) of second compensation structure20, but to the right of it (negative Y direction).

It is essential for the effect of the dynamic quadrature compensation that the compensation structure be mounted at parts of the sensor elements which participate both in the primary vibration and the secondary vibration. For the rotation rate sensors explained as examples, this means only Coriolis element2a,2b. Mounting compensation structures19,20at sensor elements participating in only one of the vibrations would not bring about any dynamic compensation effect.

The first specific embodiment distinguishes itself in that it leads to a superimposition of static and dynamic quadrature compensation effect, and that the mass distribution inside Coriolis element2a,2bremains symmetrical to a great extent at compensation structures19,20.

InFIG. 2the effect of the static compensation forces is explained in greater detail. By the suitable positioning of compensation structures19,20, it is achieved that, because of the static forces (short arrows) on Coriolis element2a, a torque about the center of gravity, denoted by reference symbol S inFIG. 2, of Coriolis element2ais generated, but that no linear force component in the y direction is present, because of the static compensation forces. According to the present invention, because of the voltages applied to compensation structures19,20, the force effect is such that a twisting of, in the present example, Coriolis element2a, and thus also a twisting of the principal axis system of Coriolis element2ais effected with respect to the substrate. If Coriolis element2ais in a rest position in the X direction, because of the positioning of substructures19,20, and by applying a voltage to first substructure19, there comes about a twisting of, or rather a torque on Coriolis element2aclockwise inFIG. 2, and by applying a voltage to second substructure20, there comes about a twisting of, or rather a torque on Coriolis element2acounterclockwise inFIG. 2.

The dynamic force contributions shown by long arrows, which appear when Coriolis element2ais deflected from its rest position with respect to the X direction, cause a linear force effect which, in the X direction of positive excursion of Coriolis element2a, is oriented for first compensation structure19in the positive Y direction, and for second compensation structure20in the negative Y direction.

Because of the superimposition of the dynamic and the static force contributions, according to the present invention it is advantageously possible to carry out a quadrature compensation.

Further exemplary embodiments of the present invention are shown below, with particular focus on the differences from the example discussed up to now.

The second exemplary embodiment inFIG. 5differs by the geometrical positioning of first and second substructures19,20. For simplicity's sake, first partial structure50aof a rotation rate sensor according to the present invention is shown again inFIG. 5. On first side61of Coriolis element2a, in the left part (in the direction of the positive Y axis) a number of first substructures19are provided, and in the right part a number of second substructures20are provided. On second side62of Coriolis element2a, in the left part (in the direction of the positive Y axis) a number of first substructures19are provided, and in the right part a number of second substructures20are provided. In the second exemplary embodiment, first substructures19are provided on first side61and on second side62according to third positioning possibility230. In the second exemplary embodiment, second substructures20are provided on first side61and on second side62according to second positioning possibility220. Correspondingly, the dynamic and the static force effects are shown again by long and short arrows inFIG. 5, and they correspond to what was described forFIG. 3with respect to second and third positioning possibilities220,230, respectively, of cutout regions65,66. Because of the changed positioning of cutout regions65,66, with reference to the first exemplary embodiment, it is achieved that in the rest position of the sensor, i.e. not having excursion in the X direction of the Coriolis element, no resulting torque acts upon the sensor structure (short arrows inFIG. 5). Consequently, in this arrangement, no static quadrature compensation becomes effective.

The compensation system inFIG. 6or the detail section inFIG. 7shows a third specific embodiment of the present invention, and stands out in that the compensation structures19,20are each localized on only one of partial structures50a,50b. First substructure19is exclusively localized on first partial structure50a, and second substructure19is exclusively localized on second partial structure50b. First substructure19and second substructure20are differently provided as in the first exemplary embodiment on first side61and second side62, namely: For first side61and first substructure19, first positioning possibility210, for first side61and second substructure20, second positioning possibility220, for second side62and first substructure19, third positioning possibility230, and for second side62and second substructure20, fourth positioning possibility240. Consequently, likewise, both a static (torque) and a dynamic quadrature compensation becomes effective. One advantage of the system inFIG. 6is that it is more simply implementable because of the lower number of printed circuit traces. Since, as a rule, only either the first or the second substructures are controlled, the compensation forces act upon only one of partial structures50a,50b; however, because of the active mechanical coupling of the two partial structures50a,50b, the compensation forces are transmitted respectively to the other partial structure. The system of the compensation structure for negative quadrature on second partial structure50b(FIGS. 6 and 7, right) may be produced by a symmetry operation—in particular a mirroring at the symmetry line furnished with the reference symbol SL by the overall center of gravity furnished with the reference symbol Sg—from the first compensation structure for positive quadrature on the first partial structure (FIGS. 6 and 7, left).

The rotation rate sensor according to the present invention inFIG. 8, or the detailed cutout inFIG. 9, according to a fourth specific embodiment, differs in turn by the orientation of cutout sections65,66of compensation structures19,20within Coriolis elements2aand2b, respectively. Here too, first substructure19or second substructure20are localized on one respective partial structure50a,50b(left or right, respectively). First substructure19is provided equally for first side61and second side62. Second substructure20is also provided equally for first side61and second side62. Third positioning possibility230of cutout regions65,66is provided for first substructure19. Fourth positioning possibility240of cutout regions65,66is provided for second substructure20. By this changed orientation it is achieved that in the sensor's rest position no resulting torque acts upon the sensor structure (short arrows inFIGS. 8 and 9). Consequently, in this arrangement, no static quadrature compensation becomes effective. Here too, the system of the compensation structure for negative quadrature on second partial structure (FIGS. 8 and 9, right) may be produced by a symmetry operation (mirroring at the symmetry line furnished with the reference symbol SL by the overall center of gravity furnished with the reference symbol Sg) from the first compensation structure for positive quadrature on the first partial structure (FIGS. 8 and 9, left).

The present invention describes possibilities for the reduction of interference signals in micromechanical rotation rate sensors having the following advantages:

A simple, reliable and cost-effective electrostatic method for quadrature compensation (electrical compensation) is proposed, in contrast to costly (iterative) physical balancing methods.

Reduction of the quadrature takes place in the sensor element itself. Consequently, no quadrature signals arise at the means of detection for the Coriolis effect, which results in clearly reduced requirements on the primary sensor signal evaluation and improved sensor performance, respectively.

The method is based, in particular, on the effect of dynamic forces. Because of that, compared to a purely static compensation method, a clearly greater compensation range is accessible.

The method is based on the use of suitable asymmetries within the mechanical sensor structure. Consequently, compensation may take place by a single exterior potential (dc voltage).

The present invention may be used for whole classes of rotation rate sensors, especially vibration gyroscopes, whose primary and secondary vibrations proceed within the plane of the substrate. In addition, the present invention is compatible with the most varied sensor evaluation circuit concepts.