System with high performance sensors with extended lifetime

Abstract

The invention is entitled "System with high performance sensor with extended lifetime". The invention discloses a system comprising a high performance sensor for providing accurate measurement results and at least one dissimilar sensor which is less accurate. The at least one dissimilar sensor is a different type of sensor than the high performance sensor while providing the same type of measurement results as the high performance sensor. The at least one dissimilar sensor has a longer expected lifetime than the high performance sensor. At least one controller is configured to start the high performance sensor and the at least one dissimilar sensor upon start-up of the system, to shut down the high performance sensor after a selected period of time, and to output measurement data based on the measurement results of the high performance sensor when the high performance sensor is on and based on the at least one dissimilar sensor when the high performance sensor is off.

Description

BACKGROUND

[0001] Gyroscopes can be used as a navigation aid. Gyroscopes measure orientation and angular rate. In aircraft applications, these measurements provide important information for safely operating the aircraft as it traverses through its path of travel. There are several different types of gyroscopes used for aircraft navigation. Two exemplary types include ring laser gyroscopes (RLGs) and microelectromechanical systems (MEMS) gyroscopes. RLGs have excellent run-to-run stability, but their expected lifetime is less than the expected lifetime of the aircraft. Other types of sensors, such as MEMS gyroscopes, have good angular random walk (ARW) and good run-in-bias stability, but poor run-to-run stability. ARW is the velocity error that accumulates over time due to noise. Run-in-bias stability is a measure of the random variation of the bias calculated over a specified sampling time and averaging time interval. Run-to-run (or turn-to-turn) stability is the residual output error that occurs after calibration and internal compensation from the effects of turn-on, turn-off, time variation, and temperature variation. Thus, a suitable long-life self-aligning gyroscope system cannot currently be manufactured by either technology type. SUMMARY

[0002] The following summary is made by way of example and not limitation. The purpose of the summary is to enable the reader to understand some aspects of the described subject matter. The summary is not intended to be limiting in any way, and does not delineate the scope of the subject matter. Embodiments provide a system that selectively incorporates a high performance sensor and at least one dissimilar sensor at selected times during operation of the system to extend the lifetime of the high performance sensor.

[0003] In one embodiment, a system is provided that includes a high performance sensor, at least one dissimilar sensor, and at least one controller. The high performance sensor is used to provide accurate measurements. The at least one dissimilar sensor is a different type of sensor than the high performance sensor, while providing the same type of measurements as the high performance sensor. The at least one dissimilar sensor is not as accurate as the high performance sensor, and has a longer expected lifetime than the high performance sensor. The at least one controller is in communication with the high performance sensor and the at least one dissimilar sensor. The at least one controller is configured to start the high performance sensor and the at least one dissimilar sensor at start-up of the system. The at least one controller is further configured to shut off the high performance sensor after a selected period of time. The at least one controller is further configured to output measurement data based on measurements of the high performance sensor when the high performance sensor is on, and output measurement data based on the at least one dissimilar sensor when the high performance sensor is off.

[0004] In another example embodiment, another gyro system is provided that includes a ring laser gyroscope (RLG) to provide rate / angle measurements, a plurality of dissimilar sensors, and at least one controller. Each dissimilar sensor is a different type of sensor than the RLG that also provides rate / angle measurements. The at least one controller is in communication with the RLG and the plurality of dissimilar sensors. The at least one controller is configured to start the RLG and the plurality of dissimilar sensors at a start-up of the gyro system. The at least one controller is further configured to turn off the RLG after a selected period of time. The at least one controller is further configured to output rate / angle measurements based on the RLG when the RLG is on, and output rate / angle data based on the plurality of dissimilar sensors when the RLG is off. The at least one controller is further configured to determine a bias error between the output of the RLG and the plurality of dissimilar sensors when the RLG is on, and calibrate the rate / angle data from the plurality of dissimilar sensors based on the determined bias error when the RLG is off.

[0005] In yet another embodiment, a method of operating a gyro system is provided. The method includes turning on a ring laser gyroscope (RLG) and at least one dissimilar sensor, each dissimilar sensor being a different type of sensor than the RLG that also provides rate / angle measurements; using rate / angle measurements of the RLG when the RLG is on; determining a bias error associated with rate / angle measurements of the at least one dissimilar sensor; storing calibration information based on the bias error in a memory; turning off the RLG; and calibrating rate / angle measurements from the at least one dissimilar sensor based on the stored calibration information. BRIEF DESCRIPTION OF DRAWINGS

[0006] The embodiments can be more easily understood and further advantages and uses thereof will be more readily apparent, when considered in view of the following detailed description and the accompanying drawings, in which:

[0007] Figure 1 is a block diagram of a gyro system according to one example embodiment;

[0008] Figure 2 shows a gyro system operation flow diagram according to one example embodiment;

[0009] Figure 3 shows a timing flow diagram according to one example embodiment;

[0010] Figure 4 shows a solution determination flow diagram according to one example embodiment;

[0011] Figure 5 is a block diagram of another gyro system according to one example embodiment; and

[0012] Figure 6 A flow diagram of a three-gyro system operation is shown in accordance with one example embodiment.

[0013] In accordance with common practice the various features described with reference to the drawings are not necessarily drawn to scale but are susceptible to change in scale in order to emphasize specific features relevant to the subject matter at hand. Reference numerals are used consistently throughout the drawings and the written description and refer to the same or similar elements in all figures and the written description. DETAILED DESCRIPTION

[0014] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration specific embodiments in which the application can be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the various embodiments, and it is to be understood that other embodiments can be utilized and that changes can be made without departing from the spirit and scope of the present application. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present application is defined only by the claims and equivalents thereof.

[0015] Embodiments provide systems that improve the expected lifetime of high performance sensors. The systems described herein include a high performance sensor and at least one dissimilar sensor. The at least one dissimilar sensor provides the same type of measurement as the high performance sensor, but is generally less accurate than the high performance sensor. In addition, the at least one dissimilar sensor can have a longer expected lifetime than the high performance sensor. In embodiments, the expected lifetime of the high performance sensor is extended by selectively turning off the high performance sensor during vehicle mission periods where the measurement from the at least one dissimilar sensor can be safely used. Vehicle applications in which the systems can be incorporated include, but are not limited to, automobiles, trucks, boats, airplanes, spacecraft, etc. The systems described herein can be applied in vehicles where the vehicle mission is longer than the expected lifetime of the high performance sensor, or where the vehicle has a longer expected lifetime than the high performance sensor.

[0016] The embodiments are described below as exemplary embodiments applicable to a gyro system that selectively incorporates a ring laser gyroscope (RLG) (exemplary high performance sensor) and at least one other dissimilar sensor (such as, but not limited to, a micro-electro-mechanical system (MEMS)) at selected times to extend the life of the RLG. Specifically, in some embodiments, the gyro system uses only the long enough accurate sensor (RLG) to overcome the run-to-run repeatability issues of the other dissimilar sensor. The RLG is then turned off to limit the amount of time the RLG is used. The gyro system is just one example of an implementable system. Any system that requires a high performance sensor with an expected life less than the expected life of the associated vehicle or with less than the expected life of the vehicle mission can implement the systems described herein. Thus, the embodiments are not limited to just gyro systems.

[0017] Referring to Figure 1 , a block diagram of one example gyro system 100 is shown. The gyro system 100 is shown to include a controller 102, a memory 110, an RLG 104 (high performance sensor), a plurality of dissimilar sensors 106-1 through 106-N, a Kalman filter 112, vehicle controls 114, and a clock 116. The dissimilar sensors 106-1 through 106-N can be other types of gyroscopes, such as MEMS gyroscopes, or other devices that provide orientation and angular velocity information. The vehicle controls 114 can be vehicle systems that use measurements from the gyro system 100 (generally described as rate / angle measurements) to at least display or even control aspects of the vehicle based on the rate / angle measurements from the gyro system 100 for navigation reasons. In one exemplary embodiment, the controller 102 uses the clock 116 to at least track the time the RLG 104 is on.

[0018] Generally, the controller 102 can include any one or more of a processor, a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or equivalent discrete or integrated logic circuitry. In some example embodiments, the controller 102 can include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, one or more FPGAs, and other discrete or integrated logic circuitry. The functions attributed to the controller 102 herein can be embodied by software, firmware, hardware, or any combination thereof. The controller can be part of a system controller or a component controller. The memory 110 can include computer readable operational instructions that, when executed by the controller, provide the functionality of the gyroscope system 100. Such functionality can include the functionality of turning the RLG 104 on and off, as described below. The computer readable instructions can be encoded within the memory 110. The memory 110 can include computer readable storage media including any volatile, non-volatile, magnetic, optical, or electrical media, such as but not limited to, a random access memory (RAM), read only memory (ROM), non-volatile RAM (NVRAM), electrically

[0019] Figure 2 A gyroscope system operational flowchart 200 of an example embodiment is shown. The flowchart 200 is provided as a series of sequential steps. In other embodiments, the order and even the content can be different. Thus, embodiments are not limited to the sequence and content shown in the example flowchart. Figure 2

[0020] In the gyroscope system operational flowchart 200, the process begins by turning on all sensor devices at block (202). All sensor devices include the RLG 104 and a distinct sensor, generally represented as 106. Then, in the gyroscope system embodiment, the controller 102 receives all sensor or measurement data including rate / angle measurements from the RLG 104 and the distinct sensor 106. Based on instructions stored in the memory 110, the rate / angle measurements of the RLG data are used by the controller 102 as the primary measurement data at block (210) when the RLG 104 is on.

[0021] ​Further, at block (206), the bias error of the N dissimilar sensors is calculated by the controller 102. In this example embodiment, at block (208), a compensation model based on the bias error of each dissimilar sensor 106 is loaded onto and stored in the memory 110. In one embodiment, the compensation model is based on a comparison of the measured output of the dissimilar sensor 106 to the measured output of the RLG 104. At block (212), the controller 102 converts to rate measurement using the dissimilar sensor measurement output using the compensation module stored in the memory 110. The RLG 104 is then switched off at block (214).

[0022] Figure 3 One example of a timing flowchart 300 of an example embodiment is shown in FIG. 3. The flowchart 300 is provided as a series of sequential steps. In other embodiments, the order and even the content can be different. Thus, the embodiments are not limited to the sequence and content shown in the example flowchart. Figure 3

[0023] In this example embodiment, at block (302), the RLG 104 and the dissimilar sensor are turned on. At block (304), the time of the RLG turn on is tracked. Once it is determined that the selected time has been reached at block (306), the RLG 104 is turned off at block (308). In one embodiment, the time period is a period long enough to overcome the run-to-run repeatability issue of the dissimilar sensor 106.

[0024] In one embodiment, the dissimilar sensor 106 and the RLG 104 are turned on at the beginning of a "day". At start-up, the RLG 104 self-aligns and provides data to calibrate the dissimilar sensor bias to about 0.002 degrees / hour to 0.003 degrees / hour for a selected initial calibration time period. For example, the selected time period can be the first hour of operation. The RLG 104 is then switched off, and the dissimilar sensor 106 is used for navigation for the remainder of the "day". With this system, the useful life of the RLG 104 can be extended by a factor of 15 for 15 hours of a day. The system not only solves the run-to-run bias repeatability issue of the dissimilar sensor (such as the MEMS run-to-run bias repeatability issue), but also extends the life of the RLG 104.

[0025] In an example embodiment, the bias error of the dissimilar sensor 106 can be determined using the Kalman filter 112 during a selected calibration period of RLG operation. Thereafter, the calibrated (adjusted) rate / angle measurements from the dissimilar sensor 106 based on the determined bias error are used for the remainder of the "day", and the RLG 112 is switched off.

[0026] ​Furthermore, in an embodiment, the RLG 104 may be opened at any time during a period of time to provide a new solution (update calibration information) to add fault tolerance or detection to the gyroscope system 100. Figure 3 At block (310), it is determined whether a new solution is needed at block (310). In one embodiment, the need for a new solution is the need for a new compensation model (or calibration information) stored in memory 110, as described above in Figure 2 If a new solution is needed, the RLG 104 is turned on at block (312). The time the RLG 104 is turned on is tracked at block (314). Once it is determined at block (316) that the selected time has been reached, the RLG 104 is turned off. The operating time of the RLG 104 may be variable, depending on the ARW of the RLG 104 and the bias uncertainty level required for the different sensors.

[0027] exist Figure 4 An example of the application of a Kalman filter is shown in the solution determination flowchart 400. The flowchart 400 is provided as a series of sequential steps. In other embodiments, the order and even the content may be different. Therefore, the embodiments are not limited to Figure 4 The sequence and content shown in the exemplary flow chart of FIG.

[0028] The process begins at block (402) where it is determined whether the RLG 104 is on. If the RLG is on, the process uses the Kalman filter 112 at block (404) to determine bias errors associated with the dissimilar sensor measurements. At block (406), calibration information based on the determined bias errors is stored in the memory 110. If the RLG is not on as determined at block (402), the stored calibration information is used at block (408) to generate rate / angle measurements from the dissimilar sensors.

[0029] The embodiment can also be applied to Figure 5 The sensor triad shown. Figure 5 5. The gyroscope system 500 is shown as including an RLG triad 504, a plurality of distinct sensor triads 106-1 to 106-N, a Kalman filter 512, a vehicle control 514, and a clock 516. The distinct sensor triads may be other types of gyroscope triads, including MEMS triads that provide orientation and angular velocity information. Figure 1 The embodiment includes a controller 502 and a memory 510 to at least perform the above Figure 1 The functions described in the described implementation scheme.

[0030] Figure 6 A flowchart 600 of an exemplary implementation of a triad gyroscope system operation is shown. The flowchart 600 is provided as a series of sequential steps. In other implementations, the order and even the content can be different. Thus, the implementation is not limited to Figure 2 the sequence and content shown in the exemplary flowchart.

[0031] In the gyroscope system operation flowchart 600, the process starts by turning on all sensor devices at block (602). The all sensor devices include the RLG triad 504 and the dissimilar sensor triads generally represented as 506. The controller 502 then receives all sensor data including rate / angle measurements from the triad RLG 504 and the dissimilar sensor triads 506. At block (604), the controller 502 uses the RLG data as the primary data at block (610) based on instructions stored in the memory 510 while the RLG 504 is on.

[0032] At block (606), the controller 502 calculates the bias error for the N dissimilar sensor triads. At block (608), the bias error for the N dissimilar sensor triads is stored in memory. As described above, in one implementation, calibration information based on the bias error is stored in memory. At block (612), the data from the N dissimilar sensor triads 506 is converted for use using the calculated bias error. The RLG triad is then turned off at block (614). Then, while the RLG triad 504 is off, the converted measurements from the N dissimilar sensor triads 506 are used by the gyroscope system 500.

[0033] Exemplary Embodiments

[0034] Example 1 is a system comprising a high performance sensor, at least one dissimilar sensor, and at least one controller. The high performance sensor is configured to provide accurate measurements. The at least one dissimilar sensor is a different type of sensor than the high performance sensor while providing the same type of measurements as the high performance sensor. The at least one dissimilar sensor is less accurate than the high performance sensor and has a longer expected life than the high performance sensor. The at least one controller is in communication with the high performance sensor and the at least one dissimilar sensor. The at least one controller is configured to start the high performance sensor and the at least one dissimilar sensor at system startup. The at least one controller is further configured to turn off the high performance sensor after a selected period of time. The at least one controller is further configured to output measurement data based on measurements of the high performance sensor while the high performance sensor is on and output measurement data based on the at least one dissimilar sensor when the high performance sensor is off.

[0035] Example 2 includes the system of Example 1, wherein the expected lifetime of the high- performance sensor is less than at least one of: the expected lifetime of the at least one dissimilar sensor; and the mission of the vehicle in which the high-performance sensor is implemented.

[0036] Example 3 includes the system of any of the Examples, wherein the high-performance sensor is a ring laser gyroscope (RLG) and the measurement is a rate / angle measurement.

[0037] Example 4 includes the system of Example 3, wherein the at least one controller is further configured to determine a bias error between the rate / angle measurement of the RLG and the rate / angle measurement of the at least one dissimilar sensor when the RLG is on, and to convert the rate / angle measurement of the at least one dissimilar sensor using the determined bias error when the RLG is off.

[0038] Example 5 includes the system of Example 4, further comprising at least one Kalman filter used by the at least one controller to determine the bias error, the at least one controller configured to use an estimated solution from the Kalman filter when the RLG is off and to use the estimated solution to calibrate the output of the at least one dissimilar sensor.

[0039] Example 6 includes the system of Example 5, further comprising a memory to store calibration information based on the determined bias error, the at least one controller in communication with the memory.

[0040] Example 7 includes the system of Example 6, wherein the at least one controller is further configured to periodically turn on the RLG to update the calibration information.

[0041] Example 8 includes the system of any of Examples 1-7, further comprising a clock. The at least one controller is in communication with the clock to track the time the high-performance sensor is on.

[0042] Example 9 includes the system of any of Examples 1-8, wherein the selected period of time is a time required to overcome a run-to-run repeatability issue of the at least one dissimilar sensor.

[0043] Example 10 is a gyro system comprising a ring laser gyroscope (RLG) to provide rate / angle measurements, a plurality of dissimilar sensors, and at least one controller. Each dissimilar sensor is a different type of sensor than the RLG that also provides rate / angle measurements. The at least one controller is in communication with the RLG and the plurality of dissimilar sensors. The at least one controller is configured to start the RLG and the plurality of dissimilar sensors when the gyro system is started. The at least one controller is further configured to turn off the RLG after a selected time period. The at least one controller is further configured to output rate / angle measurements based on the RLG when the RLG is on, and output rate / angle data based on the plurality of dissimilar sensors when the RLG is off. The at least one controller is further configured to determine a bias error between the output of the RLG and the plurality of dissimilar sensors when the RLG is on, and calibrate the rate / angle data from the plurality of dissimilar sensors based on the determined bias error when the RLG is off.

[0044] Example 11 includes the gyro system of Example 10, further comprising a memory to store calibration information determined based on the bias error. The at least one controller is in communication with the memory.

[0045] Example 12 includes the gyro system of any of Examples 10-11, further comprising a clock. The at least one controller is in communication with the clock. The at least one controller is configured to track a time the RLG is on.

[0046] Example 13 includes the gyro system of any of Examples 10-12, wherein the selected time period is a time required to overcome run-to-run repeatability issues of the at least one dissimilar sensor.

[0047] Example 14 includes the gyro system of any of Examples 10-13, wherein the RLG is an RLG triad and each dissimilar sensor is a dissimilar sensor triad.

[0048] Example 15 is a method of operating a gyro system. The method comprises turning on a ring laser gyroscope (RLG) and at least one dissimilar sensor, each dissimilar sensor being a different type of sensor than the RLG that also provides rate / angle measurements; using rate / angle measurements of the RLG when the RLG is on; determining a bias error associated with rate / angle measurements of the at least one dissimilar sensor; storing calibration information based on the bias error in a memory; turning off the RLG; and calibrating rate / angle measurements from the at least one dissimilar sensor based on the stored calibration information.

[0049] Example 16 includes the method of example 15, further comprising applying a Kalman filter to determine a bias error associated with rate / angle measurements of the at least one dissimilar sensor.

[0050] Example 17 includes the method of example 16, wherein the Kalman filter uses rate / angle measurements from the RLG and the at least one dissimilar sensor to determine the bias error.

[0051] Example 18 includes the method of any of examples 15-17, wherein turning off the RLG further comprises turning off the RLG after a selected time needed to overcome a run-to-run repeatability issue of the at least one dissimilar sensor has elapsed.

[0052] Example 19 includes the method of any of examples 15-18, further comprising re-opening the RLG to update calibration information.

[0053] Example 20 includes the method of any of examples 15-19, wherein the RLG is an RLG triad and the at least one dissimilar sensor is at least one dissimilar sensor triad.

[0054] While specific embodiments have been shown and described in detail to illustrate the application, it will be readily appreciated by those skilled in the art that any arrangement which is calculated to achieve the same purpose can be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of the present application. Therefore, it is manifestly intended that this application be limited only by the claims and the equivalents thereof.

Claims

1. A system (100), comprising: a ring laser gyroscope (104) for providing rate / angle measurements; at least one dissimilar sensor (106), the at least one dissimilar sensor (106) being a different type of sensor than the ring laser gyroscope (104) while providing the same type of measurements as the ring laser gyroscope (104), the at least one dissimilar sensor (106) being less accurate than the ring laser gyroscope (104) and having a longer life expectancy than the ring laser gyroscope (104); and at least one controller (102) in communication with the ring laser gyroscope (104) and the at least one distinct sensor (106), the at least one controller (102) being configured to activate the ring laser gyroscope (104) and the at least one distinct sensor (106) when the system (100) is activated, the at least one controller (102) being further configured to deactivate the ring laser gyroscope (104) after a selected period of time, the at least one controller (102) being further configured to output measurement data based on measurements of the ring laser gyroscope (104) when the ring laser gyroscope (104) is activated, and to output the measurement data based on the at least one distinct sensor (106) when the ring laser gyroscope (104) is deactivated, The at least one controller (102) is further configured to determine a bias error between a rate / angle measurement of the ring laser gyroscope (104) and a rate / angle measurement of the at least one dissimilar sensor (106) when the ring laser gyroscope (104) is turned on and to convert the rate / angle measurement of the at least one dissimilar sensor (106) using the determined bias error when the ring laser gyroscope (104) is turned off.

2. The system (100) according to claim 1, further comprising: At least one Kalman filter (112) is used by the at least one controller (102) to determine the bias error, the at least one controller (102) being configured to use an estimated solution from the Kalman filter (112) when the ring laser gyroscope is off and to use the estimated solution to calibrate an output of the at least one dissimilarity sensor (106).

3. The system (100) according to claim 2, further comprising: A memory (110) for storing calibration information based on the determined bias error, the at least one controller (102) being in communication with the memory (110).

4. The system (100) according to claim 3, wherein The at least one controller (102) is further configured to periodically turn on the ring laser gyroscope (104) to update calibration information.

5. A vehicle comprising the system according to claim 1, wherein: The expected life of the ring laser gyroscope (104) is less than the expected life of the vehicle.

6. A method of operating a gyroscope system (100), the method comprising: turning on a ring laser gyroscope (104) and at least one distinct sensor (106), each distinct sensor (106) being a different type of sensor than the ring laser gyroscope (104) that also provides rate / angle measurements; When the ring laser gyroscope (104) is turned on, using the rate / angle measurements of the ring laser gyroscope (104), the at least one dissimilar sensor (106) is less accurate than the ring laser gyroscope (104) and has a longer life expectancy than the ring laser gyroscope (104); determining a bias error between rate / angle measurements of the ring laser gyroscope (104) and rate / angle measurements of the at least one distinct sensor (106); storing calibration information based on the bias error in a memory (110); Turning off the ring laser gyroscope (104); as well as The rate / angle measurements from the at least one distinct sensor (106) are calibrated based on the stored calibration information.

7. The method according to claim 6, further comprising: A Kalman filter (112) is applied to determine a bias error in the rate / angle measurements of the at least one distinct sensor (106).

8. The method according to claim 6, wherein: Turning off the ring laser gyroscope (104) further includes: The ring laser gyroscope (104) is turned off after a selected time period required to overcome run-to-run repeatability issues of the at least one distinct sensor (106).

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