Field of the Invention

The present invention mainly relates to a field of gyroscope and more particularly relates to an AC, DC input and AC output rate gyro module based on Micro-Electro-Mechanical Systems (MEMS) sensor.

Background of the invention

Gyroscopes are well known in the art which is a device used for measuring or maintaining orientation and angular velocity. It is basically a spinning wheel or disc in which the axis of rotation is free to assume any orientation by itself. When rotating, the orientation of this axis is unaffected by tilting or rotation of the mounting, according to the conservation of angular momentum. The gyroscopes have been used as a core/main element of an inertial navigation system or any guidance system for guided missiles, aircraft flight control systems, ships or aircraft Gyroscopes were invented a century ago and have been used as references to know inertial state of a moving body. In any of the spacecraft/aircraft, the quality of gyro determines the performance of the overall mission. It has been a factor behind ‘make or break’ of the many missions.

Gyroscopes are employed in many critical applications like guiding ballistic missiles, guiding the process of building tunnels, fire control systems abound ships, satellite navigation etc. Further, the gyroscopes have expanded the areas of applications to military and aviation purposes.

Gyroscopes have evolved over the period and hence, many technologies on which gyroscopes are based today, although only a few of them find their place in the practical applications. As the technology evolved, other types of gyroscopes were developed which could provide more accurate and consistent output. Over the period, as potential applications for gyroscopes were identified, need to develop low cost and compact gyroscopes were felt.

In addition, rate gyros are majorly used for measuring the rate about an axis. The conventional mechanical rate gyros are basically AC input (in an example, 26Vrms, 400Hz, etc.) and AC output. Further, the AC output has to be demodulated and converted to DC before using in any system. The Mechanical Rate Gyros were being used from 5 to 6 decades in various control and navigation applications for aerospace and industrial. The mechanical Rate Gyros has several limitations in terms of MTBF (Mean time between failures), complexity, Weight, Volume, life of gyro, Power and Cost. Typical MTBF of a Mechanical Rate Gyro is about 15000 Flours. On the other side, solid state rate Gyros will have about > 100000 Flours of MTBF in addition to less Weight, Volume, Power and Cost effective. Some of these mechanical rate gyros have become obsolete and where the systems with these gyros are still in use. But, drop in replacement for these mechanical rate gyros are not easily available in the form factor required. The usage of the available rate gyros will impose constraints like redesign of existing circuitry to take different form of inputs (DC, Serial interface, etc.)., Interface compatibility issues, functional compatibility issues and etc. Moreover, the understanding of old designs and making suitable redesign and re-qualification is a huge effort and time consuming in addition to high cost with substantial risk.

There may be many designs/systems making use of mechanical rate gyros. The system using mechanical rate gyros may get declared unserviceable, due to rate gyro failures and non-availability due to obsolescence of mechanical gyros. Alternate rate gyros available may not be functional and form fit.

Therefore, there is a need in the art with an AC, DC input and AC output rate gyro based on Micro-Electro-Mechanical Systems (MEMS) sensor to solve the above mentioned limitations. Summary of the Invention

An aspect of the present invention is to address at least the above- mentioned problems and/or disadvantages and to provide at least the advantages described below.

Accordingly, one aspect of the present invention relates to an AC, DC input and AC output rate gyro module 100, the module comprising: atleast one voltage regulator 120, wherein the voltage regulator 120 is used to receive an input voltage and generate a required constant voltage level, a MEMS based GYRO sensor module 1 10 , wherein the MEMS based GYRO sensor module 1 10 is configured to measure one or more angular movements of an aircraft, wherein the MEMS based GYRO sensor module further configured to process and provide an output rate (sensor signal (X)) equivalent to the measured angular movement, an attenuator 130 coupled and configured to receive an input power and attenuate the received input power for generating the required constant voltage levels (Y) and (Z), an analog multiplier 140 coupled and configured to receive the processed output rate

(X) from the MEMS based GYRO sensor module, required constant voltage levels

(Y) and (Z) from the corresponding attenuators, processes and provides corresponding AC output with reference to sensed angular movement.

Another aspect of the present invention relates to a method for providing an AC output rate from AC, DC input, the method comprising: measuring one or more angular movements of an aircraft by a MEMS based GYRO sensor module, wherein the MEMS based GYRO sensor module is configured to measure, process and provide an output rate (sensor signal (X)) equivalent to the measured angular movement 210, receiving an input power by an attenuator, wherein the attenuator attenuates the received input power for generating the required constant voltage levels (Y) and (Z) 220 and receiving the output rate (X) from the MEMS based GYRO sensor module and required constant voltage levels (Y) and (Z) from the corresponding attenuators by an analog multiplier, wherein the analog multiplier processes the received signals and provides corresponding AC output with reference to sensed angular movement 230. Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

Brief description of the drawings

The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

Figure 1 shows a functional block diagram of AC, DC input and AC output rate gyro module based on Micro-Electro-Mechanical Systems (MEMS) sensor according to one embodiment of the present invention.

Figure 2 shows a method for providing an AC output rate from AC, DC input by a MEMS gyro module according to one embodiment of the present invention.

Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.

Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures. Detailed description of the invention

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

It is to be understood that the singular forms“a,”“an,” and“the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to“a component surface” includes reference to one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic is intended to provide.

Figures, discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way that would limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged communications system. The terms used to describe various embodiments are exemplary. It should be understood that these are provided to merely aid the understanding of the description, and that their use and definitions, in no way limit the scope of the invention. Terms first, second, and the like are used to differentiate between objects having the same terminology and are in no way intended to represent a chronological order, unless where explicitly stated otherwise. A set is defined as a non-empty set including at least one element.

The present invention provides an AC, DC input and AC output rate gyro module based on Micro-Electro-Mechanical Systems (MEMS) sensor. The preset invention substitutes the existing AC input and AC output mechanical rate gyro without calling/requiring for any redesign and requalification of existing electronics in the system.

The present invention solves the problem of non-availability of the Rate Gyro in required form fit and functional (obsolescence issues). The present invention solves the problem of Low MTBF (Mean Time between Failures) issues of Mechanical Gyros.

The present invention solves the problem of repair complexity of miniature/ spin motor rate Gyros.

The present invention solves the problem of high cost issues with the mechanical rate Gyros.

The present invention solves the problem of performance issues with mechanical Rate Gyros.

The present invention Rate Gyro module works with various AC frequencies (like 400/800/1600/2400 Hz, etc.).

Figure 1 shows a functional block diagram of AC, DC input and AC output rate gyro module based on Micro-Electro-Mechanical Systems (MEMS) sensor according to one embodiment of the present invention.

The figure shows the functional block diagram of AC, DC input and AC output rate gyro module based on Micro-Electro-Mechanical Systems (MEMS) sensor for aircraft. The system/module is functional and form fit replacement for any Mechanical Rate gyro which is AC input and AC output in nature. Based on the specifications of the rate gyro, factory tuning has to be done to meet specific requirement. The present invention system/module has atleast one Vref Generator, Health check 1 18, MEMS based GYRO sensor module 1 10, atleast one low pass filter 1 12, atleast one voltage follower 1 14, atleast one differential amplifier 1 16, atleast one regulator 120, atleast one buffer 124, atleast one attenuator 130 and atleast one analog multiplier 140. The present invention uses MEMS based Rate Gyro as a sensing element. The module takes AC input (Any standard frequencies used for Rate Gyros like 400/800/1200/1600/2400Hz, etc.) and provides corresponding AC output with respect to the sensed rate. It will also provide required AC bias and health status signal. It acts like AC input and AC output Rate Gyro similar to Mechanical Rate Gyros. The present invention provides a drop in replacement solution for current or mechanical gyros in existing systems where the mechanical gyros are becoming obsolete and not available easily in functional form fit and also having high failure rate.

The MEMS based gyro DC output is used for proportionally converting to AC output by using analog multiplier to generate AC rate output. Refer Figure 1 for functional block diagram of“AC, DC input and AC output rate gyro module based on MEMS sensor”. The MEMS based gyro module requires AC input 26Vrms, 400Hz and DC input ±15V supplies. In this module, MEMS sensor is used for sensing the rate of aircraft. In an example, the specification of the“AC, DC input and AC output gyro module based on MEMS sensor” is given below:

Working of AC, DC input AC output Rate Gyro Module based on MEMS Sensor.

The system/module is functional and form fit replacement for any Mechanical Rate gyro which is AC input and AC output. Based on the specifications of the rate gyro, factory tuning has to be done to meet specific rate gyro requirement like AC voltage, Frequency, output sensitivity, output range, Bandwidth, etc. The present invention uses MEMS based Rate Gyro as a sensing element. It takes AC input (Any standard frequencies used for Rate Gyros like 400/800/1200/1600/2400Hz, etc.) and provides corresponding AC output with respect the sensed rate. It will also provide required AC bias and health status signal. It acts like AC input and AC output Rate Gyro similar to Mechanical Rate Gyros. In one embodiment, the present invention relates to an AC, DC input and AC output rate gyro module 100, the module comprising: atleast one voltage regulator 120, wherein the voltage regulator 120 is used to receive an input voltage and generate a required constant voltage level, a MEMS based GYRO sensor module 1 10 , wherein the MEMS based GYRO sensor module 1 10 is configured to measure one or more angular movements of an aircraft, wherein the MEMS based GYRO sensor module further configured to process and provide an output rate (sensor signal (X)) equivalent to the measured angular movement, an attenuator 130 coupled and configured to receive an input power and attenuate the received input power for generating the required constant voltage levels (Y) and (Z), an analog multiplier 140 coupled and configured to receive the processed output rate (X) from the MEMS based GYRO sensor module, required constant voltage levels (Y) and (Z) from the corresponding attenuators, processes and provides corresponding AC output with reference to sensed angular movement.

The MEMS based GYRO sensor module is coupled and configured to measure the any one of the one or more angular movements which is pitch, yaw and roll. The MEMS based GYRO sensor module further provides required AC bias and health status signal to confirm the working status of the MEMS based GYRO sensor module. The voltage regulator 120 is configured to power the MEMS based GYRO sensor moduleand generates Vref Voltage.The voltage regulator is coupled to receive about ± 15V DC, attenuates and generates about +5V DC signal to power the MEMS based GYRO sensor module and the attenuator is coupled to receive voltage of about 26 V rms, @ 400 Hz AC. The module has a low pass filter 1 12 coupled to MEMS based GYRO sensor module to receive the MEMS GYRO output (measured angular movement rate) in order to attenuate high frequency noise. The module has a voltage follower 1 14 coupled to the low pass filter to receive the filtered output and processes in order to avoid impedance mismatches.

The constant voltage level from the voltage regulator 120 is buffered using a buffer amplifier 124 and provide the buffered signal to the differential amplifier 1 16. The module has a differential amplifier 1 16 having one of the inputs from a voltage follower to receive the sensor output and another input from buffered reference voltage from buffer amplifier. The differential amplifier 1 16 has a gain corresponding to the required scale factor of the Rate Gyro.

The analog multiplier 140 is coupled and configured to receive and convert the DC output rate to AC output and processes the received inputs with (X ^* Y)/10 +Z to provide the corresponding AC output, where, X= measured any one of one or more angular movement of an aircraft (Yaw rate) (DC output), Y= required constant voltage level (Y) which is about 10 Vmax AC, 400 Hz, Z= required constant voltage level (Z) which is about 0.3 Vmax AC, 400 Hz. In an example embodiment of the present invention,

the existing mechanical rate gyro has

Inputs: Voltage of about 26 V rms, @ 400 Hz and

Output: Voltage range about ±6 Vrms @ 400 Hz, Null rate output: 0.3Vmax, @ 400 Hz and sensitivity of 280mV/deg/sec., Speed/heath output: >10.5VDC In an example embodiment of the present invention, rate gyro system/module has

Inputs: AC, DC input and AC output gyro module (New Rate Gyro): - a) about ± 15VDC to internal analog circuit operation.

b) about 26 Vrms, 400 Hz AC

Outputs: - (Output - (X ^* Y)/10 +Z).

a) Yaw rate output (about ± 6Vrms max) w.r.t yaw rate (± 20Vsec) sensing by gyro module.

b) Gyro module health output

c) Null rate output: about 0.3Vrms

d) Health output: >about 10.5VDC

In an example embodiment, the Voltage [15V to 5V] regulator is used to generate +5V DC signal from +15 V DC supply. +5 V DC supply is used for powering up MEMS sensor and also to generate Vref Voltage and same has been Buffered and used. To match the existing mechanical rate gyro, MEMS based sensor Ratio metric DC output is converted into AC output by using multiplier (AD 632) 1C (Output = (X ^* Y)/10 +Z).

Where X= Yaw rate sensor (MEMS sensing element) signal conditioning circuit output (DC output), i.e. Translating the Ratio Metric DC output of the sensor to required DC output form; Y= 10 Vmax AC, 400 Hz; Z= 0.3 Vmax AC, 400 Hz.

In an example embodiment, the present invention module calculates the Yaw rate Sensor Signal Conditioning Circuit: (X signal Generation) a) MEMS based rate Gyro Sensor [MEMS BASED GYRO] (ADXRS624) sense the yaw rate and provides the output with sensitivity of 25mV/Vsec. At Null rate it will provide 0.25 V DC.

b) The output is ratio metric with respect to a provided reference supply (5V). It produces a positive going output voltage for clockwise rotation (>2.5V up to 4.75 V) and produces a negative going output voltage for anticlockwise rotation (<2.5V up to 0.25V)

c) The sensor output (with external configurable components of the sensor) is limited to about 8 Hz Bandwidth as per requirement.

d) The sensor output is passed through Low Pass Filter (Cutoff frequency 220 Hz) to attenuate high frequency noise 14.5 KHz (Sensor resonance frequency) from sensor output line.

The low-pass filter (LPF) is a filter that passes signals with a frequency lower than a certain cut-off frequency and attenuates signals with frequencies higher than the cut-off frequency. The exact frequency response of the filter depends on the filter design. The present invention may use/configure the filter as per requirements.

Further, the sensor filtered output is passed through Voltage follower circuit before giving to differential amplifier to avoid impedance mismatches.

Next, to bring sensor output at null rate to 0V (instead of 2.5V), sensor buffered output is passed through differential amplifier (by subtracting 2.5V, internally generated voltage reference from 5V). The differential amplifier is a type of electronic amplifier that amplifies the difference between two input voltages but suppresses any voltage common to the two inputs. It is an analog circuit with two inputs and one output in which the output is ideally proportional to the difference between the two voltages. The present invention may use/configure/set the voltage levels to the amplifier as per requirements.

In an example embodiment,

a) Differential amplifier gain is set to about 1 1 .2 to match the existing mechanical gyro sensor output sensitivity of about 280mV/7sec. [Gain =1 1 .2; MEMS sensor sensitivity about 25mV/7sec * 1 1.2 = 280mV/7sec] b) Sensor signal conditioning output limited to about ±6 V by using zener diodes (zener voltage 5.6 v) to limit the gyro measurement range to ± 20 deg/sec

Generation of 400 Hz AC signal generation (Y & Z) a. about 10 Vmax AC, 400 Hz signal is generated from about 26 Vrms,

400 Hz by using attenuator circuit and then Buffered. where the attenuator is an electronic device that reduces the power of a signal without appreciably distorting its waveform. The present invention may use any type of attenuator as per requirements. b. 0.3 Vmax AC, 400 Hz signal is generated from 10Vmax,400 Hz signal by using 2 ^nd atte n u ato r circuit 132. c. 10 Vmax AC, 400 Hz and 0.3 Vmax AC, 400 Hz signals are given to Analog multiplier Y & Z inputs respectively.

To match the existing mechanical rate gyro signal phase with respect to about 26 Vrms, 400 Hz input signal (Anticlockwise: output is in phase with input, Clockwise: output is out of phase with input) AD632 Analog multiplier output is passed through inverter circuit after multiplier output stage (Not shown in block schematic).

In an example embodiment, the MEMS based gyro module output:

a. At Null rate: 0.3 V max AC, 400 Hz (Vref (2.5 V) - X (2.5 V MEMS Sensor Output at null rate)) - {which is the Z component of the equation}

b. Clockwise direction: Out of phase with 26 Vrms, 400 Hz input signal

(output = 0.3 Vrms max - rate output voltage at the rate of 280 mV/deg/sec).

c. Anti-clockwise direction: In phase with 26 Vrms, 400 Hz input signal (output = 0.3 Vrms max +rate output voltage at the rate of 280 mV/deg/sec). MEMS Sensor health check:

a. MEMS Sensor health is verified by using a comparator circuit (comparing MEMS Sensor Output (>0.25 V) with internally generated 0.2V)

b. Sensor Health Output:

i. Sensor at Healthy Condition: +1 1 V (approx.) ii. Sensor at non-Healthy Condition: 0 V (approx.)

Some of the factory settable/configurable features are:

1 . Configurable to various AC input voltages: about 400/800/1600/2400 Hz, etc. 2. Sensor Band width: in an example, the present design is for 8Hz. It may be configurable to required band width.

3. Null Rate Voltage: about 0.3Vrms. It may be configurable to required levels.

4 Sensitivity: about 280mV/deg/sec: It may be configurable to required levels. 5. Heath output Voltage Level: about 10.5V DC. It may be configurable to required voltage levels.

6. Mounting: Based mount matching existing mechanism. It is configurable based on the requirement.

Figure 2 shows a method for providing an AC output rate from AC, DC input by a MEMS gyro module according to one embodiment of the present invention.

The figure shows a method for providing an AC output rate from AC, DC input by an AC, DC input and AC output rate gyro module. The method comprising: measuring one or more angular movements of an aircraft by a MEMS based GYRO sensor module, wherein the MEMS based GYRO sensor module is configured to measure, process and provide an output rate (sensor signal (X)) equivalent to the measured angular movement 210, receiving an input power by an attenuator, wherein the attenuator attenuates the received input power for generating the required constant voltage levels (Y) and (Z) 220 and receiving the output rate (X) from the MEMS based GYRO sensor module and required constant voltage levels (Y) and (Z) from the corresponding attenuators by an analog multiplier, wherein the analog multiplier processes the received signals and provides corresponding AC output with reference to sensed angular movement 230. The MEMS based GYRO sensor module is coupled and configured to measure the any one of the one or more angular movements which is pitch, yaw and roll.

There may be many designs/systems making use of mechanical rate gyros. But the system will get declared unserviceable due to rate gyro failures and non availability due to obsolescence of mechanical gyros. Alternate rate gyros available may not be functionally suitable and form fit. In such cases, the present invention provides a drop in replacement for obsolete mechanical gyros without calling/requiring for redesign and requalification of complete existing electronics in the system, whereas other solutions requires for new design. The present invention solution effectively recovers failed critical systems which are not operational due to non-availability of mechanical rate gyros.

Those skilled in this technology can make various alterations and modifications without departing from the scope and spirit of the invention. Therefore, the scope of the invention shall be defined and protected by the following claims and their equivalents.

Figures are merely representational and are not drawn to scale. Certain portions thereof may be exaggerated, while others may be minimized. Figures illustrate various embodiments of the invention that can be understood and appropriately carried out by those of ordinary skill in the art.

In the foregoing detailed description of embodiments of the invention, various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the invention require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the detailed description of embodiments of the invention, with each claim standing on its own as a separate embodiment.

It is understood that the above description is intended to be illustrative, and not restrictive. It is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined in the appended claims. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms“including” and“in which” are used as the plain-English equivalents of the respective terms“comprising” and“wherein,” respectively.