Rotation rate sensor and method for operating a rotation rate sensor

Abstract

A gyroscope with a substrate (2) and a Coriolis element (3) movable relative to the substrate (2), wherein the gyroscope has excitation means for exciting a drive oscillation of the Coriolis element (3) along a first direction (X) and wherein the gyroscope has detection means for detecting a Coriolis deflection of the Coriolis element (3) along a third direction (Z) perpendicular to the first direction (X), characterized in that the gyroscope has a quadrature compensation structure (6) comprising both a comb electrode structure (60) and a plate capacitor structure (61), wherein the plate capacitor structure (61) comprises a surface electrode (62) substantially parallel to a principal extension plane (100) of the substrate (2), which is attached to the substrate (2) and which is arranged perpendicular to the third direction (Z) at least partially between the Coriolis element (3) and the substrate (2).

Description

State of the art

[0001] The invention is based on a yaw rate sensor according to the preamble of claim 1.

[0002] Such methods are generally known. For example, WO 2003 / 058 167 A1 discloses a yaw rate sensor comprising a substrate and a Coriolis element. The Coriolis element can be excited to a drive oscillation parallel to a first axis. A deflection of the Coriolis element is provided due to a Coriolis force along a detection direction perpendicular to the first axis. The yaw rate sensor has force-transmitting means between the substrate and the Coriolis element in the form of compensation structures, which are provided for compensating quadrature disturbances. The Coriolis element comprises a seismic mass with a plurality of cutouts into which electrodes of the compensation structures, connected to the substrate, protrude.The inner circumference of each cutout is designed asymmetrically, so that quadrature compensation forces parallel to the detection direction are generated by appropriately wiring the electrodes. These quadrature compensation forces serve to compensate for the quadrature disturbances that are superimposed on the detection movement of the Coriolis element and arise due to manufacturing imperfections in the sensor design during excitation of the drive vibration. Unfortunately, the quadrature compensation forces are strongly dependent on the deflection along the detection direction, so that an unintentional oscillation of the Coriolis element around its operating point along the detection direction results in a change in the quadrature compensation force. This leads to an increased vibration sensitivity of the sensor arrangement to external disturbances.The operating point-dependent quadrature compensation forces also result in an operating point-dependent electrostatic spring stiffness along the detection direction, so that the effective resonance frequency of the sensor arrangement also exhibits an undesirable operating point dependence.

[0003] Further angular rate sensors with a substrate and a Coriolis element are known from the documents DE 10 2007 030 119 A1, US 2007 / 0 234 803 A1, US 8 061 201 B2 and US 7 043 985 B2. Disclosure of the invention

[0004] The yaw rate sensor according to the invention and the method according to the invention for operating a yaw rate sensor according to the independent claims have the advantage over the prior art that the quadrature compensation structure generates a quadrature compensation force on the Coriolis element, which, on the one hand, compensates for the unwanted quadrature disturbances and, on the other hand, has no or only a significantly reduced operating point dependence along the third direction (i.e., in the force direction or in the detection direction). Advantageously, this significantly increases the vibration sensitivity of the yaw rate sensor compared to the prior art. Furthermore, the resonant frequency of the yaw rate sensor along the third direction is not influenced, or is influenced only insignificantly, by the quadrature compensation.These advantages are achieved by the quadrature compensation comprising both the comb electrode structure and the plate capacitor structure. The comb electrode structure generates a first compensation force, and the plate capacitor structure generates a second compensation force, each on the Coriolis element along the third direction (hereinafter also referred to as the detection direction), with the quadrature compensation force essentially comprising the sum of the first and second compensation forces. The first and second compensation forces each depend on the position of the Coriolis element along the first direction (hereinafter also referred to as the drive direction) as well as on the position of the Coriolis element along the detection direction (operating point dependence).Due to the physical properties of a comb electrode structure, the change of the first compensation force with increasing deflection of the Coriolis element along the detection direction (away from the substrate) is negative, whereas due to the physical properties of a plate capacitor structure, the change of the second compensation force with increasing deflection of the Coriolis element along the detection direction (away from the substrate) is positive (see, for example, . Fig. 3). Advantageously, the change in the first compensation force at least partially compensates for the change in the second compensation force and / or the change in the second compensation force at least partially compensates for the change in the first compensation force, so that, in total, a quadrature compensation force is generated which has no or only a significantly reduced dependence on the deflection of the Coriolis element along the detection direction and thus on the operating point of the Coriolis element along the detection direction. The yaw rate sensor preferably comprises a micromechanical yaw rate sensor, which is provided for measuring yaw rates "in-plane" (axis of rotation of the yaw rate parallel to a main extension plane of the substrate) and / or "out-of-plane" (axis of rotation of the yaw rate perpendicular to the main extension plane). The substrate comprises, in particular, a semiconductor substrate, such as silicon.Advantageous embodiments and further developments of the invention can be found in the dependent claims and the description with reference to the drawings.

[0005] According to one embodiment of the invention, the plate capacitor structure comprises a surface electrode that is substantially parallel to a main extension plane of the substrate, which is attached to the substrate and arranged perpendicular to the third direction, preferably at least partially between the Coriolis element and the substrate. Advantageously, the surface electrode is suitable for generating, based on electrostatic interaction, a second compensation force on the Coriolis element perpendicular to the main extension plane in the direction of the substrate and in particular parallel to the third direction. The magnitude of the second compensation force increases with increasing negative deflection of the Coriolis element from the initial position toward the substrate along the third direction Z.

[0006] According to a preferred embodiment, the comb electrode structure comprises first finger electrodes and second finger electrodes engaging with the first finger electrodes parallel to the first direction, wherein the first finger electrodes are preferably attached to the substrate and wherein the second finger electrodes are preferably attached to the Coriolis element. Advantageously, the comb structure is suitable for generating a first compensation force on the Coriolis element perpendicular to the main extension plane in the direction of the substrate and in particular along the third direction. This first compensation force is usually referred to as a levitation force and arises from an asymmetric field distribution above and below the finger electrodes. The space on the side of the first and second finger electrodes facing away from the substrate is not delimited by the substrate, so that the stray fields expand more on this side.The resulting force is the first compensation force, which is directed away from the substrate parallel to the third direction. The first and second compensation forces are thus diametrically opposed, so that they partially compensate each other. However, the magnitudes of the first and second compensation forces are different, so that a resultant quadrature compensation force is still generated towards the substrate. The second compensation force decreases with increasing negative deflection of the Coriolis element from the initial position towards the substrate along the third direction Z. Since the signs of the first and second compensation forces are inverse to each other, the change in the first compensation force and the change in the second compensation force as a function of the deflection along the third direction are also opposite to each other, so that the sum of these changes at least partially compensate each other.Advantageously, a quadrature compensation force is thus generated which has no or only a weak dependence on the deflection of the Coriolis element along the third direction.

[0007] According to a preferred embodiment, the first finger electrodes are electrically conductively connected to the surface electrode. This advantageously significantly simplifies the electrical contacting and control of the quadrature compensation structure. The ratio between the first and second compensation forces is preferably determined by the design of the plate capacitor structure relative to the comb electrode structure.

[0008] According to a preferred embodiment, the rotation rate sensor has a further quadrature compensation structure, which comprises a further comb electrode structure and a further plate capacitor structure, wherein the further plate capacitor structure preferably comprises a further surface electrode substantially parallel to the main extension plane, and wherein the further comb electrode structure preferably comprises further first finger electrodes attached to the substrate and further second finger electrodes attached to the Coriolis element and engaging with the first finger electrodes parallel to the first direction. Compensation of force components extending perpendicular to the third direction is advantageously achieved, which compensation is generated by the quadrature compensation structure.

[0009] According to a preferred embodiment, the quadrature compensation structure and the further quadrature compensation structure are mirror-symmetrical with respect to a mirror plane perpendicular to both the main extension plane and the first direction, so that forces of the comb electrode structure along the first direction can be compensated by the further comb electrode structure in such a way that no resulting force components are generated on the Coriolis element along the first direction. The drive oscillation is thus advantageously not influenced by the quadrature compensation structures.

[0010] According to a preferred embodiment, the Coriolis element has a recess perpendicular to the main extension plane, in which the comb electrode structure and / or the further comb electrode structure are arranged. This particularly advantageously enables a comparatively compact arrangement of the yaw rate sensor, and the excitation means can be arranged on the outer sides of the Coriolis element in a known manner.

[0011] According to a preferred embodiment, the quadrature compensation structure and the further quadrature compensation structure are configured such that the quadrature compensation force is dependent on the drive oscillation and / or such that the quadrature compensation force is substantially independent of the Coriolis deflection. Advantageously, by appropriately dimensioning the plate capacitor structure and the comb electrode structure, a quadrature compensation force is achieved which, at the operating point, depends only on a drive-induced deflection of the Coriolis element along the first direction (drive direction) and not, or only insignificantly, on the deflection of the Coriolis element along the third direction (detection direction).

[0012] A further subject of the present invention is a method for operating a yaw rate sensor, wherein in a first operating step, the drive oscillation of the Coriolis element is excited along the first direction, and in a second operating step, a quadrature compensation force is generated along the third direction on the Coriolis element by the quadrature compensation structure such that a change in a first compensation force generated by the comb electrode structure as a function of the Coriolis deflection is at least partially compensated by a change in a second compensation force generated by the plate capacitor structure as a function of the Coriolis deflection. Thus, as already explained in detail above, a quadrature compensation force is advantageously generated which, at the operating point, has no or only an insignificant dependence on the deflection of the Coriolis element along the third direction.Compared to the prior art, the vibration sensitivity is thus advantageously reduced. The quadrature compensation force plotted against the Coriolis deflection preferably exhibits a maximum at the operating point, i.e., in the initial position, so that the vibration sensitivity at the operating point is significantly reduced.

[0013] According to a preferred embodiment, it is provided that the quadrature compensation force is generated on the Coriolis element in such a way that the quadrature compensation force is dependent on the drive vibration and / or that the quadrature compensation force is substantially independent of the Coriolis deflection.

[0014] Embodiments of the present invention are illustrated in the drawings and explained in more detail in the following description. Short description of the drawings

[0015] It shows Fig. 1 is a schematic perspective view of a quadrature compensation structure of a yaw rate sensor according to a first embodiment of the present invention, Fig. 2 a schematic plan view of a portion of a rotation rate sensor according to the first embodiment of the present invention, Fig. 3 shows a schematic curve of a quadrature compensation force of a rotation rate sensor according to the first embodiment of the present invention and Fig. 4a, Fig. 4b, Fig. 5a, Fig. 5b, Fig. 6a and Fig. 6b schematic views of various compensation forces of a yaw rate sensor according to the first embodiment of the present invention. Embodiment of the invention

[0016] In Fig. 1 shows a schematic perspective view of a quadrature compensation structure of a yaw rate sensor according to a first embodiment of the present invention, wherein the yaw rate sensor comprises a substrate 2 with a main extension plane 100 and a Coriolis element 3 movable relative to the substrate. The Coriolis element 3 is excited relative to the substrate 2 by means of excitation means (not shown) to a drive oscillation along a first direction X parallel to the main extension plane 100. In the presence of a yaw rate about a rotation axis parallel to a second direction Y perpendicular to the first direction X and parallel to the main extension plane 100, the Coriolis element 3 experiences a Coriolis force parallel to a third direction Z perpendicular to the main extension plane 100, which causes a Coriolis deflection of the Coriolis element 3 along the third direction Z, which can be detected by means of detection means (not shown). Fig. 1, the Coriolis element 3 is shown in its initial position 110 (also called the equilibrium position). The Coriolis deflection (not shown) comprises a positive deflection of the Coriolis element 3 from the initial position 110, which is directed away from the substrate 2, or a negative deflection of the Coriolis element from the initial position 110, which is directed toward the substrate 2. A quadrature disturbance 90 along the third direction Z is superimposed on the Coriolis deflection, which results from manufacturing-related imperfections of the yaw rate sensor. To compensate for this quadrature disturbance 90, the yaw rate sensor has a quadrature compensation structure 6. The quadrature compensation structure 6 comprises a comb electrode structure 60, which includes first and second finger electrodes 63, 64 extending parallel to the first direction X. The first finger electrodes 63 are anchored to the substrate 2 and the second finger electrodes 64 are anchored to the Coriolis element 3.The first finger electrodes 63 further engage between the second finger electrodes 64 along the first direction X such that the first and second finger electrodes 63, 64 partially overlap each other along the second direction Y. A potential difference between the first and second finger electrodes 63, 64 causes a first compensation force 80 acting on the Coriolis element 3 along the third direction Z, directed away from the substrate 2 and also referred to as a levitation force. The first compensation force is superimposed on the quadrature disturbance 90 and increases with increasing positive Coriolis deflection. The quadrature compensation structure 6 further comprises a plate capacitor structure 61, which has a surface electrode 62 arranged along the third direction Z between the substrate 2 and the Coriolis element 3 and firmly connected to the substrate 2.A potential difference between the surface electrode 62 and a portion of the Coriolis element 3 acting as a counter electrode 62' causes a second compensation force 81, which is directed parallel to the first compensation force 80 and parallel to the third direction Z towards the substrate 2. The second compensation force 81 is opposite to the quadrature disturbance 90 and overcompensates the quadrature disturbance 90. Similar to the first compensation force 80, the second compensation force 81 also decreases with increasing Coriolis deflection directed away from the substrate 2, but in the opposite direction compared to the first compensation force 80. The sum of the first and second compensation forces 80, 81 is referred to as the quadrature compensation force 82. The comb electrode structure 60 and the plate capacitor structure 61 are now dimensioned such that in the initial position (ieat the operating point of the Coriolis element 3) the quadrature compensation force 82 causes a compensation of the quadrature disturbance 90. (∂Fz,total∂x|z=zAP≠0) and at the same time is essentially independent of the Coriolis deflection (∂∂z∂Fz,total∂x|z=zAP=0). Such an adjustment of the quadrature compensation force 82 is carried out, for example, via the number and / or width of the first and second finger electrodes 63, 64, via the distance and / or the overlap area between the first and second finger electrodes 63, 64, via the distance and / or the overlap area between the counter electrode 62' and the surface electrode 62, and the like. Optionally, it is conceivable to control the quadrature compensation force 82 via the voltage applied to the first finger electrodes 63 and the surface electrode 62, wherein the first finger electrode 63 and the surface electrode 62 are preferably connected jointly or separately.

[0017] In Fig. 2 is a schematic plan view of a portion of a rotation rate sensor according to the first embodiment of the present invention, wherein the Coriolis element 3 has a recess 8 in which the Fig. 1 and furthermore, a further quadrature compensation structure 6' of identical construction is arranged. The further quadrature compensation structure 6' is designed mirror-symmetrically with respect to a mirror plane 101 perpendicular to both the main extension plane 100 and the first direction X, which passes centrally through the recess 8, so that forces emanating from the comb electrode structure 60 and a further comb electrode structure 60' of the further quadrature compensation structure 6' parallel to the main extension plane 100 compensate each other. The quadrature compensation structure 6 and the further quadrature compensation structure 6' are preferably wired separately to compensate for manufacturing-related tolerances.

[0018] In Fig. 3 is a schematic diagram of a quadrature compensation force 90 of a rotation rate sensor according to the first embodiment of the present invention, wherein in Fig. 3 shows a diagram 102 in which the Coriolis deflection is plotted on the abscissa 103 and a force acting on the Coriolis element 3 along the third direction Z is plotted on the ordinate. The diagram 102 shows the first compensation force 80, the second compensation force 81, and the quadrature compensation force 82, each as a function of the Coriolis deflection. It can be seen that the gradient of the first compensation force 80 is negative with increasing Coriolis deflection, while the gradient of the second compensation force 81 is positive with increasing Coriolis deflection, so that the quadrature compensation force 82, as the sum of the first and second compensation forces 80, 81, has a significantly reduced dependence on the Coriolis deflection.

[0019] In Fig. 4a, Fig. 4b, Fig. 5a, Fig. 5b, Fig. 6a and Fig. 6b shows schematic views of compensation forces 80, 81 of a rotation rate sensor according to the first embodiment of the present invention, each illustrated at three different Coriolis deflections of the Coriolis element 3. In Fig. 5a and Fig. 5b shows a sectional view and a perspective view of the quadrature compensation structure 6 in the initial position of the Coriolis element 3. In the Fig. 4a and Fig. 4b, the Coriolis element 3 has a positive Coriolis deflection directed away from the substrate 2 compared to the initial position and in the Fig. 6a and Fig. 6b shows a negative Coriolis deflection compared to the initial position, directed towards the substrate 2. It can be seen that the magnitude of the first compensation force 80 in Fig. 4a and Fig. 4b (positive Coriolis deflection) smaller and in the Fig. 6a and Fig. 6b (negative Coriolis deflection) is larger than in the Fig. 5a and Fig. 5b (initial position). Accordingly, the amount of the second compensation force 81 in Fig. 4a and Fig. 4b smaller and in the Fig. 6a and Fig. 6b larger than in the Fig. 5a and Fig. 5b. The sum of the first and second compensation force 80, 81 in the form of the quadrature compensation force 82 is, however, in all Fig. 5a to 6b are essentially the same size.

Claims

[1] A rotation rate sensor comprising a substrate (2) and a Coriolis element (3) movable relative to the substrate (2), wherein the rotation rate sensor comprises excitation means for exciting a drive oscillation of the Coriolis element (3) along a first direction (X), and wherein the rotation rate sensor comprises detection means for detecting a Coriolis deflection of the Coriolis element (3) along a third direction (Z) perpendicular to the first direction (X), characterized by in that the rotation rate sensor has a quadrature compensation structure (6) which comprises both a comb electrode structure (60) and a plate capacitor structure (61), wherein the plate capacitor structure (61) comprises a surface electrode (62) which is substantially parallel to a main extension plane (100) of the substrate (2), which is fastened to the substrate (2) and which is arranged perpendicular to the third direction (Z) at least partially between the Coriolis element (3) and the substrate (2). [2] Rotation rate sensor according to claim 1, characterized by in that the comb electrode structure (60) comprises first finger electrodes (63) and second finger electrodes (64) engaging in the first finger electrodes (63) parallel to the first direction (X), wherein the first finger electrodes (63) are preferably attached to the substrate (2) and wherein the second finger electrodes (64) are preferably attached to the Coriolis element (3). [3] Rotation rate sensor according to claim 2, characterized by that the first finger electrodes (63) are electrically conductively connected to the surface electrode (62). [4] Rotation rate sensor according to one of the preceding claims, characterized byin that the rotation rate sensor has a further quadrature compensation structure (6') which comprises a further comb electrode structure (60') and a further plate capacitor structure (61'), wherein the further plate capacitor structure (61') preferably comprises a further surface electrode which is substantially parallel to the main extension plane (100), and wherein the further comb electrode structure (60') preferably comprises further first finger electrodes fastened to the substrate (2) and further second finger electrodes fastened to the Coriolis element (3) and engaging in the further first finger electrodes parallel to the first direction (X). [5] Rotation rate sensor according to claim 4, characterized by that the quadrature compensation structure (6) and the further quadrature compensation structure (6') are mirror-symmetrical with respect to a mirror plane (101) perpendicular to both the main extension plane (100) and the first direction (X). [6] Rotation rate sensor according to claim 4 or 5, characterized by that the Coriolis element (3) has a recess (8) perpendicular to the main extension plane (100), in the region of which the comb electrode structure (60) and / or the further comb electrode structure (60') are arranged. [7] Rotation rate sensor according to one of claims 4 to 6, characterized by that the quadrature compensation structure (6) and the further quadrature compensation structure (6') are designed such that the quadrature compensation force (82) is dependent on the drive vibration and / or that the quadrature compensation force (82) is substantially independent of the Coriolis deflection. [8] Method for operating a rotation rate sensor according to one of the preceding claims, characterized byin that in a first operating step the drive oscillation of the Coriolis element (3) is excited along the first direction (X) and in a second operating step a quadrature compensation force (82) is generated along the third direction (Z) on the Coriolis element (3) by the quadrature compensation structure (6) such that a change in a first compensation force (80) generated by the comb electrode structure (60) as a function of the Coriolis deflection and a change in a second compensation force (81) generated by the plate capacitor structure (61) as a function of the Coriolis deflection are at least partially mutually compensated. [9] Method according to claim 8, characterized by that the quadrature compensation force (82) is generated such that the quadrature compensation force (82) is dependent on the drive vibration and / or that the quadrature compensation force (82) is substantially independent of the Coriolis deflection.

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