Microelectromechanical inertial sensor, and method for operating microelectromechanical inertial sensor

Abstract

To provide a microelectromechanical inertial sensor, and a method for operating the microelectromechanical inertial sensor.SOLUTION: A microelectromechanical inertial sensor 1 includes: a first measuring component 4 which has oscillating elements and outputs first and second measuring signals according to a movement about an axis of rotation; and a second measuring component 5 which has oscillating elements and outputs third and fourth measuring signals according to a movement about the axis of rotation. An evaluation circuit 3 generates an output signal based on a sum of a first difference signal of the first and second measuring signals and a second difference signal of the third and fourth measuring signals. The first difference signal and the second difference signal are in phase in the event of a first acceleration. The evaluation circuit 3 is configured to amplify the first difference signal and the second difference signal in such a way that the output signal substantially disappears in the event of a second acceleration. The first acceleration is a Coriolis acceleration and the second acceleration is a rotational acceleration; or the first acceleration is a rotational acceleration and the second acceleration is a Coriolis acceleration.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a microelectromechanical inertial sensor and a method for operating a microelectromechanical inertial sensor. [Background technology]

[0002] Microelectromechanical inertial sensors are used in a variety of applications, including smartphones, game controllers, smartwatches, drones, and mobile devices. In the automotive field, inertial sensors, in particular angular velocity sensors, are used in the field of driving dynamics control and in further applications such as rollover detection.

[0003] A key performance feature of inertial sensors is their robustness to external influences, especially vibrations caused by system control interventions, as well as external influences such as stone strikes and vibrating parts inside the vehicle or engine compartment.

[0004] A microelectromechanical component for a sensor of angular velocity and a corresponding manufacturing method are known from DE 10 2020 205 372 A1. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] German Patent Application Publication No. 102020205372 Summary of the Invention [Means for solving the problem]

[0006] The invention provides a microelectromechanical inertial sensor and a method for operating a microelectromechanical inertial sensor having the features of the independent claims. Preferred embodiments are the subject of the respective dependent claims.

[0007] According to a first aspect, the present invention provides a first measurement component having a vibration element, the first measurement component outputting a first measurement signal and a second measurement signal in response to movement about a rotation axis, and a second measurement component having a vibration element, the second measurement component outputting a third measurement signal and a fourth measurement signal in response to movement about the rotation axis. An evaluation circuit generates a first differential signal between the first measurement signal and the second measurement signal, generates a second differential signal between the third measurement signal and the fourth measurement signal, amplifies the first differential signal, amplifies the second differential signal, and generates an output signal based on the sum of the amplified first differential signal and the amplified second differential signal. The first differential signal and the second differential signal are in phase at a first acceleration. The evaluation circuit amplifies the first differential signal and the second differential signal so that the output signal substantially vanishes at a second acceleration. The first acceleration is Coriolis acceleration and the second acceleration is rotational acceleration, or the first acceleration is rotational acceleration and the second acceleration is Coriolis acceleration.

[0008] According to a second aspect, the present invention relates to a method for operating a microelectromechanical inertial sensor including a first measuring component having a vibrating element. The first measuring component outputs a first measurement signal and a second measurement signal in response to movement around a rotation axis. A second measuring component including a vibrating element outputs a third measurement signal and a fourth measurement signal in response to movement around the rotation axis. A first differential signal between the first and second measurement signals is generated, and a second differential signal between the third and fourth measurement signals is generated. The first differential signal and the second differential signal are each amplified. An output signal is generated based on the sum of the amplified first differential signal and the amplified second differential signal. The first differential signal and the second differential signal are in phase at a first acceleration. The first differential signal and the second differential signal are amplified so that the output signal substantially vanishes at a second acceleration. The first acceleration is Coriolis acceleration and the second acceleration is rotational acceleration. Alternatively, the first acceleration is rotational acceleration and the second acceleration is Coriolis acceleration. [Effects of the Invention]

[0009] The microelectromechanical inertial sensor can be configured to measure Coriolis acceleration (angular velocity). By providing two measurement components, rotational acceleration can be suppressed. If the signal processing is modified, it may be contemplated that the microelectromechanical inertial sensor measures rotational acceleration and Coriolis acceleration is suppressed.

[0010] After identifying the differential signal, amplifying it before summing it to determine the output signal makes it possible to suppress signals due to rotational acceleration even if the two measurement components are not perfectly symmetrical.

[0011] Such asymmetries may arise from, for example, process non-uniformities and are stable over temperature and aging, so can be well compensated for by amplification. One possible cause of the asymmetry is the asymmetry in the spring widths of the springs of the first and second measurement components. This asymmetry is not statistical but is caused by the position of the individual microelectromechanical inertial sensors on the wafer and in the surrounding environment via the bonding pads or bonding frame, as well as gradients across the chip, resulting in different spring widths. Simply put, this can be explained by different natural frequencies of the measurement components. The weaker the mechanical coupling between the measurement components, the stronger the effect of this asymmetry.

[0012] The microelectromechanical inertial sensor can be provided as a three-axis angular rate sensor that is specifically optimized for robustness against rotational acceleration. According to one embodiment of the microelectromechanical inertial sensor, the first measuring component has a first vibration element and a second vibration element. The second measuring component has a third vibration element and a fourth vibration element. The first vibration element is arranged in mirror symmetry with respect to the third vibration element with respect to the symmetry plane. The second vibration element is arranged in mirror symmetry with respect to the fourth vibration element with respect to the symmetry plane. Under Coriolis acceleration, the first vibration element and the fourth vibration element undergo a first harmonic oscillatory motion oriented perpendicular to the symmetry plane. The second vibration element and the third vibration element undergo a second harmonic oscillatory motion oriented perpendicular to the symmetry plane. The first harmonic oscillatory motion and the second harmonic oscillatory motion are approximately in antiphase.

[0013] According to one embodiment of the microelectromechanical inertial sensor, under rotational acceleration, the first and third vibrating elements undergo a third harmonic oscillatory motion oriented perpendicular to the plane of symmetry, and the second and fourth vibrating elements undergo a fourth harmonic oscillatory motion oriented perpendicular to the plane of symmetry, the third and fourth harmonic oscillatory motions being substantially in antiphase.

[0014] According to one embodiment of the microelectromechanical inertial sensor, a first measurement signal is generated in response to the vibrational movement of a first vibration element, a second measurement signal is generated in response to the vibrational movement of a second vibration element, a third measurement signal is generated in response to the vibrational movement of a third vibration element, and a fourth measurement signal is generated in response to the vibrational movement of a fourth vibration element.

[0015] According to one embodiment, the microelectromechanical inertial sensor comprises a microelectromechanical element (MEMS element) including a first measuring component and a second measuring component. Furthermore, the microelectromechanical inertial sensor comprises an application-specific integrated circuit (ASIC) including an evaluation circuit. Therefore, the summation for generating the output signal is not performed on the MEMS element, but the measurement signals of the two measuring components are transmitted separately, and asymmetries are compensated for separately for each part in the ASIC (e.g., digitally).

[0016] According to one embodiment of the microelectromechanical inertial sensor, the evaluation circuit comprises a first digital amplifier stage configured to amplify the first differential signal. The microelectromechanical inertial sensor comprises a second digital amplifier stage configured to amplify the second differential signal. The gain factor can be set to a constant value. However, if necessary, the gain factor can be dynamically adjusted based on further input parameters, such as a temperature sensor signal or a stress sensor signal.

[0017] According to one refinement, the method for operating the microelectromechanical inertial sensor is carried out by means of an evaluation circuit of the microelectromechanical inertial sensor arranged on an ASIC. According to a refinement of the method, the first differential signal is amplified by a first digital amplification stage, and the second differential signal is amplified by a second digital amplification stage.

[0018] According to one refinement of the method, a predetermined Coriolis acceleration (or angular velocity) is applied to the microelectromechanical inertial sensor. A resulting first amplified differential signal and a second amplified differential signal are determined. Gain factors of the first and second differential signals are set based on a comparison of the first and second amplified differential signals. In particular, the corresponding first and second analog or digital amplifier stages can be trimmed.

[0019] Further advantages, features and details of the invention will become apparent from the following description, in which various embodiments are set forth in detail with reference to the drawings. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic block diagram of a micro-electro-mechanical inertial sensor according to an embodiment of the present invention in the presence of Coriolis acceleration; [Figure 2] 1 is a schematic block diagram of a micro-electromechanical inertial sensor in the presence of rotational acceleration. [Figure 3] FIG. 2 is a schematic diagram of a transfer function. [Figure 4]1 is a flowchart of a method of operating a micro-electro-mechanical inertial sensor according to an embodiment of the present invention.

[0021] In all figures, identical or functionally identical elements and devices are labeled with the same reference numerals. The numbering of method steps is for clarity and generally does not imply a particular temporal order. In particular, multiple method steps may be performed simultaneously. DETAILED DESCRIPTION OF THE INVENTION

[0022] 1 shows a schematic block diagram of a microelectromechanical inertial sensor 1 in the presence of a Coriolis acceleration 7. The microelectromechanical inertial sensor 1 comprises a MEMS element 2, which comprises a first measuring component 4 and a second measuring component 5. Furthermore, the microelectromechanical inertial sensor comprises an ASIC which comprises an evaluation circuit 3.

[0023] The micro-electromechanical inertial sensor 1 is configured to measure Coriolis acceleration 7 about an axis of rotation perpendicular to the substrate of the MEMS element 2 . The first measurement component 4 comprises a first measurement element 41 having a first vibration element and a first drive structure, and a second measurement element 42 having a second vibration element and a second drive structure. The second measurement component 5 comprises a third measurement element 51 having a third vibration element and a third drive structure, and a fourth measurement element 52 having a fourth vibration element and a fourth drive structure. The first measurement element 41 is arranged mirror-symmetrically with respect to the third measurement element 51 about the symmetry plane A. The second measurement element 42 is arranged mirror-symmetrically with respect to the symmetry plane A with respect to the fourth measurement element 52.

[0024] The first to fourth drive structures are displaced parallel to the plane of symmetry A by a drive signal (e.g., by applying an electrical voltage), causing the first and fourth drive structures to perform in-phase harmonic oscillatory motions 61, 67, and the second and third drive structures to perform anti-phase (i.e., 180° offset) harmonic oscillatory motions 63, 65.

[0025] The structure of the microelectromechanical inertial sensor 1 can basically correspond to the sensor described in DE 10 2020205 372 A1. In the presence of a Coriolis acceleration 7, the first and fourth oscillatory elements undergo a first harmonic oscillatory motion 62, 68 oriented perpendicular to the plane of symmetry. The second and third oscillatory elements undergo a second harmonic oscillatory motion 64, 66, respectively, oriented perpendicular to the plane of symmetry. The first harmonic oscillatory motion 62, 68 and the second harmonic oscillatory motion 64, 66 are substantially antiphase (opposite directions), i.e., offset from each other by 180°.

[0026] 2, when there is a rotational acceleration, the first and third vibration elements perform a third harmonic oscillatory motion 91, 93 oriented perpendicular to the plane of symmetry. The second and fourth vibration elements perform a fourth harmonic oscillatory motion 92, 94 oriented perpendicular to the plane of symmetry. The third harmonic oscillatory motion 91, 93 and the fourth harmonic oscillatory motion 92, 94 are approximately in antiphase.

[0027] The first measurement component 4 outputs a first measurement signal and a second measurement signal in response to the movement about the rotation axis. The second measurement component 5 outputs a third measurement signal and a fourth measurement signal in response to the movement about the rotation axis. The first measurement signal is generated in response to the vibrational movement of the first vibration element. The second measurement signal is generated in response to the vibrational movement of the second vibration element. The third measurement signal is generated in response to the vibrational movement of the third vibration element. The fourth measurement signal is generated in response to the vibrational movement of the fourth vibration element.

[0028] The evaluation circuit 3 includes a first differential stage 31 for generating a first differential signal for the first and second measurement signals, and a second differential stage 32 for generating a second differential signal for the third and fourth measurement signals.

[0029] The evaluation circuit 3 comprises a first digital amplifier stage 33 for amplifying the first differential signal, and further comprises a second digital amplifier stage 34 for amplifying the second differential signal. Furthermore, the evaluation circuit 3 includes a summing element 35 that sums the amplified first differential signal and the amplified second differential signal, thereby generating an output signal. The first differential signal and the second differential signal are in phase at Coriolis acceleration. The evaluation circuit amplifies the first differential signal and the second differential signal such that the output signal substantially vanishes at rotational acceleration, as will be described in more detail below.

[0030] The first to fourth measurement signals are generated based on the capacitance values ​​of the measurement electrodes.

[0031]

number

[0032] represents the capacitance at the first measuring element,

[0033]

number

[0034] is the Coriolis acceleration for the first measurement component 4

[0035]

number

[0036] represents the change in capacitance due to the capacitance change. Then, the first measurement signal is given by

[0037]

number

[0038] where:

[0039]

number

[0040] represents the frequency-dependent transfer function of the detection, which in addition to the mechanical transfer function also includes the capacitive sensitivity of the detection electrode, i.e., dC / dx. The transfer function is given by the following equation:

[0041]

number

[0042] where f1 is the natural frequency of the first measuring element, Q1 is the quality factor of the first measuring element, and f is the excitation frequency. Similarly,

[0043]

number

[0044] represents the capacitances of the second to fourth measurement elements,

[0045]

number

[0046] is the Coriolis acceleration for the second measurement component 5

[0047]

number

[0048] represents the change in capacitance due to The second measurement signal is then given by:

[0049]

number

[0050] The third measurement signal is given by:

[0051]

number

[0052] The fourth measurement signal is given by:

[0053]

number

[0054] The first differential signal is then proportional to:

[0055]

number

[0056] The second differential signal is proportional to:

[0057]

number

[0058] Here, DigGain1 and DigGain2 represent the amplification (gain) of the first amplification stage 33 or the second amplification stage 34. Then, the output signal of the adding element 35 is proportional to the following equation.

[0059]

number

[0060] rotational acceleration

[0061]

number

[0062] In the equation, the first measurement signal is given by:

[0063]

number

[0064] The second measurement signal is given by:

[0065]

number

[0066] The third measurement signal is given by:

[0067]

number

[0068] The fourth measurement signal is given by:

[0069]

number

[0070] The output signal of the summing element 35 is proportional to:

[0071]

number

[0072] In the symmetric case,

[0073]

number

[0074] Signals generated by rotational acceleration are completely suppressed without amplification. However, if asymmetry is present,

[0075]

number

[0076] Performance is degraded and cannot be compensated for by post-correction unless amplification is done before the signals are summed. Regarding the interference susceptibility of the angular velocity sensor, the frequency band around the drive frequency is particularly relevant, due to the output bandwidth of the microelectromechanical inertial sensor 1, which is typically 80-500 Hz. The drive frequency is typically 10-50 kHz, e.g. 35 kHz.

[0077] The microelectromechanical inertial sensor 1 may be operated in a partial resonance mode, i.e. the resonant frequency of the vibrating element is typically 1000-5000 Hz, e.g. 3000 Hz, above or below the driving frequency. An asymmetry of e.g. 100 Hz may exist between the two measuring components 4, 5.

[0078] By transmitting the signals separately, the error due to rotational acceleration can be reduced by intentionally trimming DigGain1 / DigGain2 by the following equation:

[0079]

number

[0080] Both the Coriolis acceleration and the critical rotational acceleration act at the drive frequency f. Since the output signal at the Coriolis acceleration also has this transfer function as an amplification (e.g., during standard adjustment of the angular rate sensitivity), DigGain1 and DigGain2 can be determined. To do this, the inertial sensor 1 can be rotated and the two angular rate channels evaluated before the final output signal is added. Thus, at the applied angular rate,

[0081]

number

[0082]

number

[0083] are determined. If the two angular rate channels are trimmed to the same sensitivity, the angular acceleration is suppressed to the maximum extent. If the gain difference is due to electrostatics rather than mechanics, then individual gain adjustments can also correct for this.

[0084] The signal processing may be modified so that the microelectromechanical inertial sensor 1 measures angular acceleration and Coriolis acceleration is suppressed. For this purpose, instead of the summing element 35, a differential stage that subtracts the signals may be used.

[0085] According to further embodiments, it may be contemplated to change the relative signs of components 35. For example, when dynamically changed, the two measurands (rotational acceleration and Coriolis acceleration) can be separated and measured separately, with one of the quantities being suppressed.

[0086] FIG. 3 shows a schematic diagram of an exemplary transfer function curve. z1 Curve 100, H z2 Curve 200, without correction, i.e., without amplification, H z1 -H z2 Curve 300 and H with correction z1 -H z2 A curve 400 is shown.

[0087] FIG. 4 shows a flow diagram of a method of operation of a microelectromechanical inertial sensor, and in particular the microelectromechanical inertial sensor 1 described above. The microelectromechanical inertial sensor 1 comprises a first measuring component 4 having a vibrating element, which outputs a first measurement signal and a second measurement signal in response to a movement about an axis of rotation.

[0088] A second measurement component 5 comprising a vibration element outputs a third measurement signal and a fourth measurement signal in response to the movement about the axis of rotation. In a first step S1, a first differential signal between the first and second measurement signals is generated, and a second differential signal between the third and fourth measurement signals is generated.

[0089] In a second step S2, the first differential signal and the second differential signal are each amplified. In a third step S3, an output signal is generated based on the sum of the amplified first differential signal and the amplified second differential signal.

[0090] The first differential signal and the second differential signal are in phase with respect to Coriolis acceleration, and the first differential signal and the second differential signal are amplified such that the output signal substantially vanishes with respect to rotational acceleration. The method of operation of the microelectromechanical inertial sensor 1 described above can be implemented by an evaluation circuit 3 arranged on the ASIC of the microelectromechanical inertial sensor 1 .

[0091] The first differential signal may be amplified by a first digital amplifier stage 33, and the second differential signal is amplified by a second digital amplifier stage . A predetermined Coriolis acceleration can be applied to the microelectromechanical inertial sensor 1 to determine the amplification factors of the amplifier stages 33 and 34. The resulting first and second amplified differential signals are identified. The amplification factors of the first and second amplified differential signals are set based on a comparison of the first and second amplified differential signals. In particular, the first and second amplifier stages can be trimmed. [Explanation of symbols]

[0092] 1 Microelectromechanical inertial sensor 3 Evaluation circuit 4, 5 Measurement Components 33 First digital amplifier stage 34 Second digital amplifier stage A symmetry plane

Claims

1. a first measurement component (4) having a vibration element, the first measurement component (4) outputting a first measurement signal and a second measurement signal in response to a movement about an axis of rotation; a second measurement component (5) having a vibration element, the second measurement component (5) outputting a third measurement signal and a fourth measurement signal in response to movement about an axis of rotation; an evaluation circuit (3) configured to generate a first differential signal between the first measurement signal and the second measurement signal, generate a second differential signal between the third measurement signal and the fourth measurement signal, amplify the first differential signal and the second differential signal, and generate an output signal based on the sum of the amplified first differential signal and the amplified second differential signal; A microelectromechanical inertial sensor (1) comprising: the first differential signal and the second differential signal are in phase at a first acceleration, and the evaluation circuit (3) is configured to amplify the first differential signal and the second differential signal so that the output signal substantially disappears at a second acceleration; The first acceleration is a Coriolis acceleration and the second acceleration is a rotational acceleration, or the first acceleration is a rotational acceleration and the second acceleration is a Coriolis acceleration. Microelectromechanical inertial sensor (1).

2. 2. The microelectromechanical inertial sensor of claim 1, wherein the first measuring component (4) has a first vibration element and a second vibration element, the second measuring component (5) has a third vibration element and a fourth vibration element, the first vibration element is arranged in mirror symmetry with respect to a plane of symmetry (A) with respect to the third vibration element, the second vibration element is arranged in mirror symmetry with respect to the plane of symmetry (A) with respect to the fourth vibration element, and under Coriolis acceleration, the first vibration element and the fourth vibration element undergo a first harmonic vibration motion oriented perpendicular to the plane of symmetry (A), and the second vibration element and the third vibration element undergo a second harmonic vibration motion oriented perpendicular to the plane of symmetry (A), and the first harmonic vibration motion and the second harmonic vibration motion are approximately in opposite phase.

3. 3. The microelectromechanical inertial sensor (1) of claim 2, wherein, under rotational acceleration, the first vibration element and the third vibration element undergo a third harmonic vibration motion oriented perpendicular to the plane of symmetry (A), and the second vibration element and the fourth vibration element undergo a fourth harmonic vibration motion oriented perpendicular to the plane of symmetry (A), and the third harmonic vibration motion and the fourth harmonic vibration motion are approximately in antiphase.

4. 4. The microelectromechanical inertial sensor (1) of claim 3, wherein the first measurement signal is generated in response to a vibrational movement of the first vibration element, the second measurement signal is generated in response to a vibrational movement of the second vibration element, the third measurement signal is generated in response to a vibrational movement of the third vibration element, and the fourth measurement signal is generated in response to a vibrational movement of the fourth vibration element.

5. a microelectromechanical device comprising said first measurement component (4) and said second measurement component (5); an application specific integrated circuit including the evaluation circuit (3); The microelectromechanical inertial sensor (1) according to any one of claims 1 to 4, comprising:

6. The microelectromechanical inertial sensor (1) according to any one of claims 1 to 5, wherein the evaluation circuit (3) comprises a first digital amplifier stage (33) configured to amplify the first differential signal and a second digital amplifier stage (34) configured to amplify the second differential signal.

7. 1. A method for operating a microelectromechanical inertial sensor (1) comprising a first measuring component (4) having a vibration element, the first measuring component outputting a first measurement signal and a second measurement signal in response to a movement about an axis of rotation, and a second measuring component (5) comprising a vibration element, the second measuring component outputting a third measurement signal and a fourth measurement signal in response to a movement about an axis of rotation, the method comprising: a) generating a first differential signal between the first measurement signal and the second measurement signal, and generating a second differential signal between the third measurement signal and the fourth measurement signal; b) amplifying the first differential signal and the second differential signal (S2); c) generating an output signal based on a sum of the amplified first differential signal and the amplified second differential signal, wherein the first differential signal and the second differential signal are in phase at a first acceleration, and the first differential signal and the second differential signal are amplified such that the output signal substantially vanishes at a second acceleration; The first acceleration is a Coriolis acceleration and the second acceleration is a rotational acceleration, or the first acceleration is a rotational acceleration and the second acceleration is a Coriolis acceleration. method.

8. The method according to claim 7, wherein steps a) to c) are performed by an evaluation circuit (3) arranged on an application specific integrated circuit of the microelectromechanical inertial sensor (1).

9. applying a predetermined Coriolis acceleration to the microelectromechanical inertial sensor (1); identifying a resulting first amplified differential signal and a second amplified differential signal; setting an amplification factor of the first amplified differential signal and the second amplified differential signal based on a comparison of the first amplified differential signal and the second amplified differential signal; The method of claim 7 or 8, further comprising:

10. The method of any one of claims 7 to 9, wherein the first differential signal is amplified by a first digital amplification stage and the second differential signal is amplified by a second digital amplification stage.

Images