Method and device for demodulating gyroscope signals

A method and a device for processing signals, including a demodulator demodulating a modulated signal during a first time interval in such a way that a quadrature signal is generated, the quadrature signal is stored in a memory unit of the device, the demodulator demodulating the modulated signal in such a way that an in-phase signal is generated during a second time interval and an output signal for describing a rotation of the gyroscope about a defined sensing axis is generated from the in-phase signal.

FIELD

The present invention relates to a method and device for demodulating gyroscope signals.

BACKGROUND INFORMATION

Methods for processing signals from a gyroscope are generally available.

It is becoming increasingly popular to use sensors, such as gyroscopes, in electronic terminal devices, and to use sensors for applications such as navigation, in buildings, and for augmented reality.

A good performance of the terminal devices or of the applications necessitates that the gyroscopes used satisfy stringent requirements in terms of the long-term stability thereof and the insensitivity to drifts. A drift is understood in this case to be a systematic effect that changes continuously in one direction.

Good performances are usually achieved by using closed-loop control circuits or electrical circuits having closed-loop architectures. In this case, however, electrical circuits having closed-loop architectures disadvantageously consume more energy than electrical circuits that do not have closed-loop architectures. In contrast to electrical circuits that do not have closed-loop architectures, a further disadvantage of electrical circuits that have closed-loop architectures is that, in the case of micromechanical sensors, both the MEMS unit (microelectromechanical systems unit), as well as the ASIC unit (application-specific integrated circuit unit) require a relatively large surface area.

Because of this disadvantage that electrical circuits that have closed-loop architectures have in contrast to those that do not have closed-loop architectures, and due to a lower complexity of the electrical circuits that do not have closed-loop architectures, electrical circuits that do not have closed-loop architectures are often used for user applications.

One of the main causes of insufficient long-term stability and insensitivity to gyroscope drifts is a change in the product of the quadrature signal and the sine of the error in the demodulation phase. There have already been various approaches for improving long-term stability and providing sufficient insensitivity to gyroscope drifts.

U.S. Pat. No. 7,290,435 B2 and U.S. Patent Application Pub. No. 2014/0190258 A1, for example, describe canceling the quadrature signal, respectively computationally eliminating it already at the front end before the signal generated by the gyroscope is measured. In addition, U.S. Patent Application Pub. No. 2015/0057959 A1 describes measuring the quadrature signal and subsequently subtracting the same using an appropriate coefficient from the main signal or in-phase signal.

SUMMARY

It is an object of the present invention to provide a method for processing signals from a gyroscope that is an alternative to the related art method. Example embodiments of the method according to the present invention may make possible the long-term stability and insensitivity to gyroscope drifts in a resource-conserving, space-saving and cost-effective manner.

The objective is achieved, for example:in a second method step, by storing the quadrature signal in a memory unit of the device;in a third method step, by the demodulator demodulating the modulated signal in such a way that an in-phase signal is generated during a second time interval;in a fourth method step, by an output signal for describing a rotation of the gyroscope about a defined sensing axis being generated from the in-phase signal.

By storing the quadrature signal in a memory unit of the device, and thus holding it in readiness for a later use, the need is hereby advantageously eliminated for components of analog circuits, such as trimmable capacitive dividers, analog-digital converters and filters. A method is hereby provided that offers another possibility for reducing energy consumption and surface area, for example, on an ASIC of a micromechanical component that includes the gyroscope, which is particularly important for developing micromechanical components that include further generations of gyroscopes.

It is especially possible to reduce the components of analog circuits by an example method according to the present invention making possible a device having merely one sensing path for the defined sensing axis. In other words, the method according to the present invention makes it possible for the device to include merely one sensing path per defined axis. In this case, both the quadrature signal, as well as the in-phase signal are read out via the one sensing path by a time division, in particular by a division into the first time interval and the second time interval.

A method is hereby provided for processing signals from a gyroscope that is an alternative to the related art method, the long-term stability and insensitivity to gyroscope drifts being made possible in a resource-conserving, space-saving and cost-effective manner. In particular, the method according to the present invention makes it possible to counter such drifts of output signals from gyroscopes that occur in response to changes in quadrature signals. Changes in quadrature signals are often caused here by stresses due to manufacturing steps, soldering steps, temperatures or the effects of aging, particularly during the lifetime of a gyroscope.

In accordance with the present invention, the gyroscope is a MEMS-based gyroscope or a MEMS gyroscope.

Advantageous embodiments and refinements of the present invention may be derived from the description herein, reference being made to the figures.

Another preferred example embodiment of the present invention provides that,in the fourth method step, a function is applied to the quadrature signal and to the in-phase signal in a processor unit of the device to generate the output signal. This advantageously makes it possible to provide an output signal for describing the rotation of the sensor element about the defined sensing axis as an essentially quadrature-corrected output signal without the need for feeding the quadrature signal back to the modulated signal and thus saving components from a possible feedback loop.

Another preferred example embodiment provides that,in a fifth method step, another function is applied to a raw signal of the signals and on the quadrature signal in a sensor channel of the device to generate the modulated signal. This advantageously makes it possible to provide an output signal for describing the rotation of the sensor element about the defined sensing axis as an essentially quadrature-corrected output signal without having to perform other method steps in a processor unit of the device, respectively without having to provide further components.

Another object of the present invention is to provide a device for processing signals, the device being configured in such a way that a gyroscope of the device generates the signals, the demodulator of the device receiving a modulated signal of the signals;in a first method step, the demodulator demodulating the modulated signal during a first time interval in such a way that a quadrature signal is generated; the device being configured in such a way that,in a second method step, the quadrature signal is stored in a memory unit of the device;in a third method step, the demodulator demodulating the modulated signal during a second time interval in such a way that an in-phase signal is generated;in a fourth method step, an output signal for describing a rotation of the gyroscope about a defined sensing axis being generated from the in-phase signal.

One preferred further embodiment provides that the device be configured in such a way that,in the fourth method step, a function is applied to the quadrature signal and to the in-phase signal in a processor unit of the device to generate the output signal.

One preferred further embodiment provides that the device be configured in such a way that,in a fifth method step, another function is applied to a raw signal of the signals and to the quadrature signal in a sensor channel of the device to generate the modulated signal.

The mentioned advantages of the method according to the present invention also apply analogously to the device according to the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the various figures, the same parts are always denoted by the same reference numerals and, therefore, are also typically only named or mentioned once.

FIG. 1is a schematic representation of a method in accordance with an exemplary embodiment of the present invention, the method being provided for processing signals, and the signals being generated by a gyroscope1of a device200. Here, a demodulator of device200receives a modulated signal of the signals. The method encompasses a first method step101, a second method step102, a third method step103, and a fourth method step104. In first method step101, demodulator5demodulates the modulated signal during a first time interval in such a way that a quadrature signal is generated. Moreover, in second method step102, the quadrature signal is stored in a memory unit7of device200. Moreover, in third method step103, demodulator5demodulates the modulated signal in such a way that an in-phase signal is generated during a second time interval. Finally, in fourth method step104, an output signal for describing a rotation of gyroscope1about a defined sensing axis is generated from the in-phase signal.

FIG. 2shows a schematic representation of a device200from the related art. In schematic representations,FIGS. 3 and 4show devices200in accordance with exemplary specific embodiments of the present invention.

Device200includes a gyroscope1, a processor unit9, and a sensor channel11. Moreover, device200includes another sensor channel13, a third sensor channel15, a capacitance-voltage transducer17, an amplitude controller19, a phase-locked loop21, and a temperature sensor23.

In the case of device200, gyroscope1is a vibration gyroscope, such as an MEMS gyroscope. Gyroscope1is configured in such a way that a rotation thereof about a defined sensing axis201, about a defined further sensing axis202, and about a defined third sensing axis203is detectable. In this case, sensing axis201, further sensing axis202, and third sensing axis203are essentially configured vertically relative to each other. Gyroscope1is also configured to generate signals, the signals including raw signals, preferably modulated raw signals. It is provided here that the signals include raw signals responsive to the movement of a vibrating test mass and responsive to a rotation of the gyroscope about sensing axis201, further sensing axis202, respectively third sensing axis203.

Moreover, gyroscope1includes a drive25. Drive25is configured in such a way that test masses assigned in each case to sensing axis201, further sensing axis202, and third sensing axis203are excited in response to a specified frequency in such a way that, in response to a rotation of the gyroscope about sensing axis201, further sensing axis202, respectively third sensing axis203, forces acting on the test masses essentially orthogonally to the respective drive directions and sensing axes generate raw signals. For this purpose, drive25receives a drive signal in order to set the respective test masses into vibration in response to specified frequencies.

Sensor channel11is electrically connected to an output of sensing axis201, so that a force acting on the vibrating test mass of sensing axis201induces a raw signal to be transmitted from the output of sensing axis201to sensor channel11. Sensor channel11includes a further capacitance-voltage transducer27; further capacitance-voltage transducer27being configured in such a way that the raw signal is converted from a modulated capacitance output signal of sensing axis201to a modulated voltage signal.

Moreover, sensor channel11includes an I/Q demodulator; the I/Q demodulator including an in-phase demodulator29and a quadrature phase demodulator31. Here, in-phase demodulator29and quadrature phase demodulator31are electroconductively connected to an output of capacitance-voltage transducer27, so that in-phase demodulator29and quadrature phase demodulator31receive the modulated voltage signal of sensing axis201. Moreover, in-phase demodulator29and quadrature phase demodulator31are designed as inverters in such a way that the modulated voltage signal of sensing axis201is demodulated in response to in-phase tracking signals and quadrature-phase tracking signals transmitted by phase-locked loop21to in-phase demodulator29and quadrature-phase demodulator31. Here, device200is designed in such a way that in-phase demodulator29is connected to an in-phase output of phase-locked loop21, so that the in-phase tracking signal is transmitted by phase-locked loop21to in-phase demodulator29, and quadrature-phase demodulator31is connected to a quadrature-phase output of phase-locked loop21, so that phase-locked loop21transmits the quadrature phase tracking signal to quadrature-phase demodulator31. Here, the in-phase tracking signal and the quadrature-phase tracking signal are 90° phase-shifted relative to each other. Moreover, it is provided that in-phase demodulator29demodulates the modulated voltage signal of sensing axis201in such a way that an in-phase component of the modulated voltage signal, respectively the in-phase signal is generated. Moreover, it is provided that quadrature phase demodulator31demodulates the modulated voltage signal of sensing axis201in such a way that a quadrature phase component of the modulated voltage signal, respectively the quadrature signal is generated.

Further sensor channel13and third sensor channel15are essentially formed, respectively configured relative to further sensing axis202and third sensing axis203, essentially in the manner of sensor channel11relative to sensing axis201.

Drive25of device200receives the drive signal from amplitude controller19of device200. For the drive of drive25, amplitude controller19controls or determines the amplitude of the drive signal here in order to set the respective test masses into vibration at specific amplitudes, respectively while maintaining specific amplitudes, in response to specified frequencies. In this case, amplitude controller19and phase-locked loop21control drive25in a closed control loop.

An output signal of drive25is transmitted here to capacitance-voltage transducer17. Capacitance-voltage transducer17generates herefrom a voltage signal that corresponds to the oscillation along a drive axis of the drive. Capacitance-voltage transducer17transmits the voltage signal to phase-locked loop21. From the voltage signal, phase-locked loop21generates a tracking signal for determining the frequency and phase of the drive signal. Phase-locked loop21generates the time-dependent tracking signal which describes the movement, respectively vibration of one or a plurality of test masses of gyroscope1. This tracking signal essentially corresponds to an in-phase tracking signal, phase-locked loop21transmitting the in-phase tracking signal to amplitude controller19. Phase-locked loop21hereby controls the amplitude controller in such a way that the amplitude, phase and frequency of the drive signal are tuned to the actual movement of the particular test masses. Moreover, phase-locked loop21transmits the in-phase tracking signal to in-phase demodulator29to control the same. Phase-locked loop21includes a phase shift circuit37; phase shift circuit37shifting the phase of the in-phase tracking signal generated by a phase-locked loop unit39of phase-locked loop21by 90° and thus including a quadrature phase tracking signal for controlling quadrature phase demodulator31.

Output signals of a phase-locked loop21control drive25, in-phase demodulator29, and quadrature phase demodulator31. Temperature influences, for example, within gyroscope1cause phase shift errors in the modulated voltage signal and thus in the in-phase signal and in the quadrature signal.

Temperature sensor23generates an analog temperature signal that contains information about a temperature of gyroscope1. Temperature sensor23transmits the analog temperature signal to a third analog-to-digital converter41which, in turn, converts the same into a digital temperature signal for a further processing in processor unit9. Temperature sensor23and third analog-to-digital converter41supply temperature data; a factor to be applied to the quadrature signal being derived from the temperature data. It is assumed in this connection that the phase shift error, respectively the absolute value thereof depends on the temperature of the gyroscope.

Device200is configured in such a way that processor unit9receives digital in-phase signals from analog-to-digital converter33, digital quadrature signals from further analog-to-digital converter35, and digital temperature signals from third analog-to-digital converter41.

Moreover, processor unit9is configured to receive digital in-phase signals and digital quadrature signals from further sensor channel13and from third sensor channel15in response to a rotation of gyroscope1about a defined further sensing axis202and a defined third sensing axis203.

Processor unit9includes a low-pass filter43, a further low-pass filter45, and a third low-pass filter47. Low-pass filter43is hereby applied to the digital temperature signal to produce a filtered digital temperature signal, further low-pass filter45to the digital in-phase signal to produce a filtered digital in-phase signal, and third low-pass filter47to the digital quadrature signal to generate a filtered digital quadrature signal. This advantageously makes it possible, in particular, for mixed products having double the frequency (in comparison to the carrier frequency) to be filtered out of the digital in-phase signal and the digital quadrature signal.

With the aid of a multiplier51, processor unit9multiplies the filtered digital temperature signal by a constant49, for example, constant c1, and, with the aid of an adder circuit55, subsequently adds the filtered digital temperature signal multiplied by first constant49to another constant53, for example, constant c0. Constant49and further constant53are stored here in a further memory unit assigned to processor unit9.

Moreover, the processor unit includes a further multiplier57; further multiplier57multiplying the output of adder circuit55, respectively the factor by the output of third low-pass filter47, respectively by the filtered digital quadrature signal to produce a scaled, filtered digital quadrature signal. It is provided here that multiplier57includes a multiplication by −1, so that multiplier57provides a negative, scaled, filtered digital quadrature signal.

Moreover, processor unit9includes a further adder circuit59; with the aid of further adder circuit59, the negative, scaled, filtered, digital quadrature signal and the filtered, digital in-phase signal being summed, and thus further adder circuit59generating, respectively providing an output signal for describing a rotation of gyroscope1about a defined sensing axis201. Processor unit9hereby dynamically adapts the factor on the basis of the temperature measured by temperature sensor23and on the basis of calibration data of gyroscope1to counter variations in the phase shift error, respectively minimize the influence of phase shift errors on the output signal. In other words, a component of the quadrature signal in the filtered, digital in-phase signal caused by the phase-shift error is computationally eliminated from the in-phase signal, so that an output signal is provided for describing the rotation of sensor element1about defined sensing axis201as an essentially quadrature-corrected output signal.

Device200illustrated inFIGS. 3 and 4is configured for processing signals in such a way that gyroscope1of device200generates the signals, and demodulator5of device200receives a modulated signal of the signals. Moreover, device200is configured in such a way that, during a first time interval, demodulator5demodulates the modulated signal in such a way that the quadrature signal is generated. In addition, device200is configured in such a way that the quadrature signal is stored in a memory unit7of device200. Moreover, device200is configured in such a way that demodulator5demodulates the modulated signal during a second time interval in such a way that an in-phase signal is generated, and an output signal for describing a rotation of gyroscope1about a defined sensing axis201is generated from the in-phase signal.

In contrast to device200illustrated inFIG. 2, device200illustrated exemplarily inFIGS. 3 and 4merely includes a sensing path in each particular case for defined sensing axis201, defined further sensing axis202and defined third sensing axis203. In other words, the present invention eliminates the need in each sensing path for a demodulator, an analog-to-digital converter and a low pass filter, for example. In device200illustrated exemplarily inFIGS. 3 and 4, both the quadrature signal, as well as the in-phase signal are read out in a sensing path. This is made possible by device200being configured in such a way, for example, that demodulator5is adapted to be connectible to an in-phase output of phase-locked loop21and to a quadrature-phase output of phase-locked loop21. Device200is configured in such a way, for example, that phase-locked loop21alternately transmits the quadrature-phase tracking signal to modulator5, particularly during the first time interval, and the in-phase tracking signal to modulator5, particularly during the second time interval. Device200is configured in such a way, for example, that controller65connects quadrature phase output and in-phase output, respectively phase-locked loop21. This is shown exemplarily by an arrow inFIGS. 3 and 4.

For example, in the case of device200illustrated inFIGS. 3 and 4, it is provided that, each time the quadrature signal is generated in first method step101, the quadrature signal is stored in memory unit7, preferably in a digital memory unit7, of device200. For example, the stored quadrature signal is used in this case for compensating for the in-phase signal in such a way that an output signal for describing the rotation of sensor element1about defined sensing axis201is generally provided as a quadrature-corrected output signal.

For example, device200is configured in such a way that, in fourth method step104, a function is applied to the quadrature signal and to the in-phase signal in processor unit9of device200to generate the output signal.

It is, moreover, provided in accordance with the present invention that—in a sixth method step, preferably controller65connects demodulator5to the quadrature phase output of phase-locked loop21. It is also preferably provided that, in the sixth method step, analog circuits of device200are configured in such a way that quadrature signals, respectively quadrature components of the modulated signal are transmittable with the aid of the analog circuits. It is especially preferred that the sixth method step be carried out before first method step101.

For example, after the sixth method step, a, preferably one single, quadrature measurement is carried out, respectively first method step101is carried out.

Moreover, for example, subsequently to first method step101, the resulting value for each channel, respectively for sensor channel11, for further sensor channel13and for third sensor channel15are stored in memory unit7, preferably of a digital memory unit7, respectively in the memory units associated with the particular sensor channels, respectively second method step102is carried out.

Moreover, it is preferably provided in accordance with the present invention that, preferably after second method step102, — in a seventh method step, preferably controller65connects demodulator5to the in-phase output of phase-locked loop21. It is also preferably provided that, in the seventh method step, analog circuits of device200are configured in such a way that in-phase signals, respectively in-phase components of the modulated signal are transmittable with the aid of the analog circuits. It is especially preferred that the seventh method step be carried out after second method step102.

For example, after the seventh method step, an in-phase measurement, preferably a plurality of in-phase measurements are performed; respectively third method step103is carried out.

Moreover, it is also provided, for example, that, subsequently to the third method step, a result of the in-phase measurement, respectively results of each of the plurality of in-phase measurements, and the stored, resulting value of the quadrature measurement, a stored resulting value of the quadrature measurement, preferably modified by a constant, especially by a first constant49, and a further constant53, are summed, and thus the output signal is generated, respectively fourth method step104is carried out. It is provided here, for example, that the constant and/or first constant49and/or further constant53be determinable by measurements, simulations and/or calculations. It is preferably provided that the constant and/or first constant49and/or further constant53are/is determinable by measurements, simulations and/or calculations in each case as a function of a temperature, preferably as a function of a temperature measured by the temperature sensor.

It is also provided that, subsequently to the fourth method step, in an eighth method step, the output signal is stored in a third memory unit of device200, respectively in a third memory unit associated with device200. Third memory unit is preferably an output register.

Moreover, it is provided, for example, that the quadrature measurement, respectively first method step101is merely implemented during a start phase of gyroscope1. However, it is also alternatively or additionally provided, for example, that the quadrature measurement, respectively first method step101is carried out at different, preferably at regular successive instants during the operation of gyroscope1. However, it is also alternatively or additionally provided, for example, that the quadrature measurement, respectively first method step101is triggered by an external influence, preferably by a temperature change. Finally, it is also alternatively or additionally provided, however, for the quadrature measurement or first method step101to be performed as a function of user input or, for example, when deemed appropriate by a user, during a reset of device200or of gyroscope1, for example.

It is preferably provided that device100include a micromechanical component3, micromechanical component3including gyroscope1and an ASIC. It is especially preferred that ASIC include sensor channel11, further sensor channel13, third sensor channel15, capacitance-voltage transducer17, amplitude controller19, phase-locked loop21, processor unit9, temperature sensor23and third analog-to-digital converter41. However, it is also alternatively provided that the ASIC merely include a portion of sensor channel11, further sensor channel13, third sensor channel15, capacitance-voltage transducer17, amplitude controller19, phase-locked loop21, processor unit9, temperature sensor23and third analog-to-digital converter41. In other words, it is provided that the inventive method is entirely carried out in micromechanical component3that includes gyroscope1, respectively in the ASIC of micromechanical component3or at least partially in an external unit assigned to micromechanical component3respectively to the ASIC of micromechanical component3, preferably an external controller, especially an external microcontroller.

For example, it is also provided that device200is configured in such a way that the quadrature, respectively quadrature signals, respectively quadrature components of the modulated signal are suppressed with the aid of force signals in the gyroscope, respectively removed from the modulated signal. For example, it is also provided, however, that device200is configured in such a way that the quadrature, respectively quadrature signals, respectively quadrature components of the modulated signal are compensated by the modulated signal with the aid of electrical compensations in the front end of the device.

For this, device200that is exemplarily illustrated inFIG. 4is configured in such a way that,in a fifth method step, another function is applied to a raw signal of the signals and to the quadrature signal in a sensor channel11of device200to generate the modulated signal. In other words, device200is configured in such a way that, in the fifth method step, memory unit7transmits the stored quadrature signal to a quadrature compensation unit67, preferably to a circuit for quadrature compensation, and quadrature compensation unit67transmits the same via further capacitance-voltage transducer27, and to the raw signal in the manner of a closed control circuit.

It is preferably provided in accordance with the present invention that, subsequently to the fifth method step, device200illustrated inFIG. 4be configured in such a way that an in-phase measurement, preferably a plurality of in-phase measurements are performed, respectively that third method step103is carried out. Finally,FIG. 4shows that device200includes a drive controller69for controlling and driving drive25.