Rotation rate sensor and method for operating a rotation rate sensor

Abstract

A gyroscope (102) with a substrate having a principal extension plane (100) for detecting a gyroscope rate about a first axis (X) extending parallel to the principal extension plane (100), characterized in that the gyroscope has a first Coriolis element (1), a second Coriolis element (2), a third Coriolis element (3) and a fourth Coriolis element (4), wherein the first Coriolis element (1) and the fourth Coriolis element (4) can be driven in the same direction parallel to a second axis (Y) extending parallel to the principal extension plane (100) and perpendicular to the first axis (X), wherein the first Coriolis element (1) and the second Coriolis element (2) can be driven in opposite directions parallel to the second axis (Y), and wherein the first Coriolis element (1) and the third Coriolis element (3) can be driven in opposite directions parallel to the second axis (Y), wherein the Coriolis elements (1, 2, 3, 4) are coupled with a translation means (200),wherein the translation means (200) is coupled to a drive means, wherein the translation means (200) is coupled to the substrate.

Description

State of the art

[0001] The invention is based on a yaw rate sensor and a method for operating a yaw rate sensor according to the preambles of the independent claims. Yaw rate sensors are known from the prior art. For example, a yaw rate sensor with two oscillating mass elements is known from the document WO 03 / 064 975 A1. Micromechanical yaw rate sensors for yaw rates about an axis parallel to the sensor plane (Z' or yaw rate Qy) are usually designed as planar oscillating masses or as masses rotating in the plane, which, when rotation occurs, experience a Coriolis force perpendicular to the plane. This force is determined either via the electrostatic counterforce required for position feedback (closed-loop control) or, for example, measured via the change in capacitance due to the change in distance to the substrate (open-loop operation).In addition to the target measurement variable, the Coriolis force, there are other forces that act on the sensors and can generate a signal: linear acceleration and rotational acceleration. The occurrence of these forces leads to false signals during operation. By differentially evaluating the forces acting on two masses moving in opposite directions, a distinction can be made between the Coriolis force and the force caused by linear acceleration (e.g., two masses oscillating towards each other or a mass rotating in a plane), in which the capacitance is evaluated at two opposite positions. Conventional sensors are insensitive to rotational acceleration about the y-axis as well as to rotational acceleration about the z-axis. Differentiating between the Coriolis force and the force caused by rotational acceleration about the x-axis is not possible with conventional sensors.This limitation is extremely disadvantageous because rotational accelerations occur as disturbances.

[0002] It is therefore an object of the present invention to provide a yaw rate sensor and a method for operating a yaw rate sensor which do not have the disadvantages of the prior art and are insensitive to rotational accelerations.

[0003] Further yaw rate sensors are known from the publications DE 10 2007 030 119 A1, DE 60 2004 006 205 T2 and US 6 848 304 B2. Disclosure of the invention

[0004] The yaw rate sensor according to the invention and the method according to the invention according to the independent claims have the advantage over the prior art in that they do not have the disadvantages of the prior art and are insensitive to disturbances and, in particular, rotational accelerations. Furthermore, it is advantageously possible for disruptive linear accelerations and disruptive rotational accelerations to produce no or at least only comparatively small disturbance signals through differential evaluation.These advantages are achieved according to the invention by a rotation rate sensor with a substrate having a main extension plane for detecting a rotation rate about a first axis extending parallel to the main extension plane, wherein the rotation rate sensor has a first Coriolis element, a second Coriolis element, a third Coriolis element and a fourth Coriolis element, wherein the first Coriolis element and the fourth Coriolis element can be driven in the same direction parallel to a second axis extending parallel to the main extension plane and perpendicular to the first axis, wherein the first Coriolis element and the second Coriolis element can be driven in opposite directions parallel to the second axis and wherein the first Coriolis element and the third Coriolis element can be driven in opposite directions parallel to the second axis.

[0005] Advantageous embodiments and further developments of the invention can be found in the dependent claims and the description with reference to the drawings.

[0006] According to a preferred embodiment, the Coriolis elements are connected to one another via coupling elements, wherein the coupling elements are preferably connected to the substrate. This advantageously makes it possible for the parallel interference modes to be shifted to high frequencies relative to the opposing detection modes.

[0007] According to another preferred development, the coupling element has a rotational axis parallel to the main plane of extension, with the rotational axis preferably running parallel to the first axis or the second axis. This advantageously makes it possible for the parallel interference modes to be shifted to high frequencies relative to the opposing detection modes.

[0008] According to another preferred development, the coupling element has a rocker structure, wherein the rocker structure preferably has a symmetrical mass distribution with respect to the axis of rotation. This advantageously makes it possible for the parallel interference modes to be shifted to high frequencies relative to the opposing detection modes.

[0009] According to the present invention, the Coriolis elements are coupled to a transmission means, wherein the transmission means is coupled to a drive means, wherein the transmission means is preferably coupled to the substrate, wherein further drive means are preferably provided, wherein the drive means are further coupled to one another. This advantageously makes it possible for the parallel interference modes in the drive movement to be shifted to higher frequencies compared to the opposing drive modes.

[0010] According to another preferred embodiment, the transmission means is quadrangular, with the transmission means preferably comprising L-shaped transmission means sub-elements. This advantageously allows the parallel disturbance modes in the drive movement to be shifted to higher frequencies compared to the opposing drive modes.

[0011] A further subject matter of the present invention relates to a method for operating a rotation rate sensor according to one of the preceding embodiments, with a substrate having a main extension plane for detecting a rotation rate about a first axis extending parallel to the main extension plane, wherein a first Coriolis element and a fourth Coriolis element are driven in the same direction parallel to a second axis extending parallel to the main extension plane and perpendicular to the first axis, wherein the first Coriolis element and a second Coriolis element are driven in opposite directions parallel to the second axis, wherein the first Coriolis element and a third Coriolis element are driven in opposite directions parallel to the second axis.

[0012] According to a preferred development, it is provided that the Coriolis elements are deflected parallel to a third axis perpendicular to the first axis and the second axis, wherein the Coriolis elements are preferably rotatably mounted, wherein a first detection signal is generated by the deflection of the first Coriolis element, wherein a second detection signal is generated by the deflection of the second Coriolis element, wherein a third detection signal is generated by the deflection of the third Coriolis element, wherein a fourth detection signal is generated by the deflection of the fourth Coriolis element, wherein the first detection signal, the second detection signal, the third detection signal and the fourth detection signal are preferably initially evaluated individually and then combined. This advantageously makes it possible for the method to be insensitive to disturbances and, in particular, rotational accelerations.Furthermore, it is advantageous that through differential evaluation, disturbing linear accelerations and disturbing rotational accelerations cause no or at least only comparatively small interference signals.

[0013] According to another preferred embodiment, the first detection signal and the fourth detection signal are added to form a first sum signal, while the second detection signal and the third detection signal are added to form a second sum signal. This advantageously allows for a simple differential evaluation. The combining can be achieved by routing conductor tracks in the element or in the evaluation circuit.

[0014] Process asymmetries can cause the drive motion to be coupled to the detection motion. This effect, known as quadrature, can be advantageously compensated for by a quadrature compensation structure. Such a quadrature compensation structure can preferably be implemented as flat electrodes that change their overlap with the Coriolis elements relative to the drive deflection.

[0015] According to another preferred embodiment, relief structures are provided on the coupling elements. This advantageously shifts the nonlinear region of the coupling elements to higher deflections.

[0016] According to another preferred development, a differential signal is formed from the first sum signal and the second sum signal, with the rotation rate being determined as a function of the differential signal. This advantageously allows for a differential evaluation to be carried out in a simple manner.

[0017] Embodiments of the present invention are illustrated in the drawings and explained in more detail in the following description. Short description of the drawings

[0018] It shows Fig. 1, Fig. 2a-d, Fig. 3, Fig. 4a-b and Fig. 5 schematic representations of exemplary embodiments of the yaw rate sensor according to the invention. Embodiment(s) of the invention

[0019] In the various figures, identical parts are always provided with the same reference symbols and are therefore usually named or mentioned only once.

[0020] In Fig. 1 shows a schematic representation of an exemplary embodiment of the yaw rate sensor 102 according to the invention. The yaw rate sensor 102 has four Coriolis elements 1, 2, 3, 4, which are designed as linearly oscillating masses (hereinafter also referred to as partial oscillators or structures). A substrate (not shown) has a main extension plane 100. The second axis (drive axis) Y lies in the main extension plane 100. Drive means (not shown), which are preferably designed as comb structures, are provided for capacitively exciting oscillations of the Coriolis elements parallel to the second axis. The Coriolis elements 1, 2, 3, 4 are connected to one another via coupling elements 101, which are preferably designed as rockers. The movements of the partial oscillators in the drive mode are indicated by the arrows. The diagonally opposite partial oscillators 1 and 4, or2 and 3 move in the same direction in the drive mode (i.e. parallel to the drive axis Y), so that the Coriolis force 103 acts in the same direction on the diagonally opposite masses due to a rotation rate about the first axis X and leads to a deflection of the opposing masses in the same direction parallel to the third axis Z.

[0021] The Coriolis force due to the drive movement causes a co-directional z-movement of substructures 1 and 4, or 2 and 3. Electrodes (not shown) are located beneath each sub-oscillator. The detection means (not shown) are preferably designed as capacitively measuring flat electrodes. The electrodes of 1 and 4 are connected together, and the electrodes of 2 and 3 are connected together. The differential evaluation of the capacitances (C1+C4)-(C2+C3) results in a net capacitance change, from which the angular rate is calculated.

[0022] Due to the drive movement and the interconnection, as well as the differential evaluation of the capacitances (C(1+4)-C(2+3)), a signal is only generated at a rotation rate around the X-axis. Linear and rotational accelerations, however, advantageously do not produce a signal.

[0023] In addition to the drive movement and detection movement, there are other interference modes that this sensor can perform and which can lead to interference signals. By introducing special coupling structures between the partial oscillators, interference modes are suppressed in the sense that they are higher in frequency than the wanted modes. These coupling structures have, for example, rocker structures or torsion beams. This separation of wanted modes and interference modes in the frequency domain advantageously leads to a lower excitation of the interference modes and thus to stable operation. The separation of the antiparallel detection movement and the associated parallel interference modes is achieved, for example, by the Fig. 2a-2d and Fig. 3, whose out-of-plane torsional mode is softer and therefore lower frequency than the bending mode.

[0024] Fig. 2a shows a further exemplary embodiment of the yaw rate sensor 102 according to the invention. The yaw rate sensor 102 has the Coriolis elements 1, 2, 3, 4. The Coriolis elements 1, 2, 3, 4 are connected to one another via coupling elements 101. The yaw rate sensor 102 has a transmission means 200. The transmission means 200 is connected to the substrate via a corner spring 299. Further corner springs 299', 299'', 299''' are arranged at the other three corners of the transmission means 200. Alternatively, the corner springs are arranged between the transmission means 200 and the Coriolis elements 1, 2, 3, 4. The transmission means 200 preferably has angular or L-shaped substructures. Fig. 2b shows the yaw rate sensor from Fig. 2a in the rest position. The Coriolis elements are excited to oscillate parallel to the y-axis via drive structures 280. Fig. 2c shows the drive deflection in the positive y-direction and Fig. 2d shows the drive deflection in the negative y-direction (where the drive structures and the coupling of the frames are not shown)

[0025] Fig. Figure 3 shows another exemplary embodiment of the yaw rate sensor 102 according to the invention. The yaw rate sensor 102 has Coriolis elements 1, 2, 3, 4. The Coriolis elements 1, 2, 3, 4 are connected to one another via coupling elements 101. The yaw rate sensor 102 has a central coupling element 301 with a torsion beam 300.

[0026] Fig. 4a shows another exemplary embodiment of the yaw rate sensor 102 according to the invention. The yaw rate sensor 102 comprises the Coriolis elements 1, 2, 3, 4, as well as a central coupling element 400. This central coupling element 400 comprises the rigid elements 405, 406, and 407. Furthermore, the central coupling element 400 comprises the optional elastic elements 403 and 404, which serve to advantageously shift the nonlinear region of the coupling element 400 to greater deflections. Furthermore, it comprises the torsion beams 401 and 402. Fig. 4b shows the embodiment of Fig. 4a in a further illustration.

[0027] Fig. Figure 5 shows another exemplary embodiment of the yaw rate sensor 102 according to the invention. The yaw rate sensor 102 additionally has a detection structure 500 (webs) for deflections in the x-direction coupled to each Coriolis element. This detection structure 500 experiences a deflection in the detection direction (indicated by the dashed arrows) due to a Coriolis force. In this way, both an x- and a z-yaw rate can advantageously be measured.

[0028] A separation of the antiparallel drive motion and the associated parallel spurious modes can be preferably suppressed by a surrounding frame (see Fig. 2a-2d). The parallel interference modes related to detection are shifted to higher frequencies by the rocker-like structures. The parallel drive modes are shifted to higher frequencies by the frame. Alternatively or optionally, this can be achieved by a Fig. 3 shown rocker structure can be achieved, in the center of which a beam 300 is stiff with respect to double bending (S-shaped bending), whereby the parallel drive mode is shifted to higher frequencies than the antiparallel (single bending of the beam). The parallel interference modes with respect to the detection are shifted to higher frequencies by the rocker-like structures. The torsion beam (300) is soft with respect to the detection mode (useful mode), in which the four partial oscillators oscillate crosswise antiparallel out of plane. Alternatively to 301 or optionally, the same can be achieved by a Fig. 4a, Fig. 4b, in which the stiff elements (405, 406, T-shaped structure) prevent bending of the coupling element and thus serve to favorably implement the drive movement described above and shift the parallel drive modes to higher frequencies. The optional elastic elements (404, 403 and U-spring at 407) serve to advantageously shift the nonlinear region of the coupling element to higher deflections. The torsion beams 402, 401 are soft with respect to torsion about their axis and stiff with respect to a linear deflection in the direction perpendicular to the main extension plane. As a result, the parallel detection modes are advantageously shifted to higher frequencies. Optionally, the yaw rate sensor 102 can be equipped with counterweights to compensate for the torque coupled out by the coupling structure 400.

[0029] Furthermore, one of the above structures with the same properties can be used to additionally measure a rotation rate around the z-axis by attaching further detection structures to the Coriolis elements movable in the x-, y- and z-directions (exemplary embodiment in Fig. 5) which detect a deflection in the x-direction. In the example shown, the x-deflection of the Coriolis elements is transmitted to the detection structures, which are rigid with respect to a deflection in the z-direction. As in the previous examples, the deflection of the Coriolis elements in the z-direction is detected, for example, using electrodes located beneath the Coriolis elements (not shown).

[0030] Furthermore, the electrodes can be used to evaluate linear and rotational accelerations, e.g. by individual evaluation of the electrodes.

[0031] The micromechanical yaw rate sensor structure 102 according to the invention can be used in all yaw rate sensors for rotations about an axis parallel to the sensor plane, as used in the automotive sector (e.g. roll-over sensing) or consumer sector (e.g. game controllers, navigation).

Claims

[1] Rotation rate sensor (102) with a substrate having a main extension plane (100) for detecting a rotation rate about a first axis (X) extending parallel to the main extension plane (100), characterized bythat the rotation rate sensor has a first Coriolis element (1), a second Coriolis element (2), a third Coriolis element (3) and a fourth Coriolis element (4), wherein the first Coriolis element (1) and the fourth Coriolis element (4) are drivable in the same direction parallel to a second axis (Y) extending parallel to the main extension plane (100) and perpendicular to the first axis (X), wherein the first Coriolis element (1) and the second Coriolis element (2) are drivable in opposite directions parallel to the second axis (Y), and wherein the first Coriolis element (1) and the third Coriolis element (3) are drivable in opposite directions parallel to the second axis (Y), wherein the Coriolis elements (1, 2, 3, 4) are coupled to a transmission means (200), wherein the transmission means (200) is coupled to a drive means, wherein the transmission means (200) is coupled to the substrate is. [2] Rotation rate sensor (102) according to claim 1, characterized bythat the third Coriolis element (3) and the fourth Coriolis element (4) are connected to one another via a coupling element (101, 301, 400), wherein the coupling element (101, 301, 400) is preferably connected to the substrate. [3] Rotation rate sensor (102) according to claim 2, characterized by that the coupling element (101, 301, 400) has an axis of rotation parallel to the main extension plane, wherein the axis of rotation preferably runs parallel to the first axis (X) or to the second axis (Y). [4] Rotation rate sensor (102) according to one of the preceding claims 2 or 3, characterized by that the coupling element (101, 301, 400) has a rocker structure, wherein the rocker structure preferably has a symmetrical mass distribution with respect to the axis of rotation. [5] Rotation rate sensor (102) according to one of the preceding claims 2 to 4, characterized bythat the coupling element (101, 301, 400) contains a beam that is soft with respect to torsion and stiff with respect to double bending, wherein preferably the coupling element (101, 301,400) is coupled to the substrate. [6] Rotation rate sensor (102) according to one of the preceding claims, characterized by that the translation means (200) is quadrangular, wherein the translation means (200) preferably has angular translation means sub-elements. [7] Method for operating a rotation rate sensor (102) according to one of the preceding claims, with a substrate having a main extension plane (100) for detecting a rotation rate about a first axis (X) extending parallel to the main extension plane (100), characterized byin that a first Coriolis element (1) and a fourth Coriolis element (4) are driven in the same direction parallel to a second axis (Y) extending parallel to the main extension plane (100) and perpendicular to the first axis (X), wherein the first Coriolis element (1) and a second Coriolis element (2) are driven in opposite directions parallel to the second axis (Y), wherein the first Coriolis element (1) and a third Coriolis element (3) are driven in opposite directions parallel to the second axis (Y). [8] Method according to claim 7, characterized byin that the Coriolis elements (1, 2, 3, 4) are deflected parallel to a third axis (Z) perpendicular to the first axis (X) and the second axis (Y), wherein a first detection signal is generated by the deflection of the first Coriolis element (1), wherein a second detection signal is generated by the deflection of the second Coriolis element (2), wherein a third detection signal is generated by the deflection of the third Coriolis element (3), wherein a fourth detection signal is generated by the deflection of the fourth Coriolis element (4), wherein the first detection signal, the second detection signal, the third detection signal and the fourth detection signal are evaluated individually and / or jointly. [9] Method according to claim 8, characterized bythat the first detection signal and the fourth detection signal are added to a first sum signal, wherein the second detection signal and the third detection signal are added to a second sum signal. [10] Method according to claim 9, characterized by that a difference signal is formed from the first sum signal and the second sum signal, wherein the rotation rate is determined as a function of the difference signal. [11] Method according to one of claims 7, 8, 9 or 10, characterized by that a rotation rate about the first axis (X) and / or about the third axis (Z) is detected.

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