Method and system for collecting airborne data using laser-induced plasma channels

Abstract

The present invention relates to a method and system for collecting air data using a laser-induced plasma channel, and provides a method for measuring air data of an aircraft. The method includes emitting a laser into the air outside the aircraft by a laser arranged on the aircraft, and the laser is tuned to induce a laser-induced plasma channel (LIPC) in the air. The method also includes sensing at least one property of the LIPC by a sensor system arranged on the aircraft. The method also includes calculating the air data of the aircraft based on at least one property of the LIPC by a computing device arranged on the aircraft.

Description

Technical Field

[0001] The field of the present disclosure relates generally to air data systems, and more particularly to systems and methods for measuring air data of an aircraft using a laser induced plasma channel. Background Art

[0002] In order to measure the aerial data of the aircraft, such as airspeed and air density, static pressure instruments such as pitot tubes are usually used. The reliability of such instruments depends on maintaining an open air channel, which may be susceptible to ice, insects, bird strikes, etc. In addition, due to the formation of heating and shock waves, pitot tubes are difficult to use at hypersonic speeds. Known alternatives to pitot tubes include light detection and ranging (LIDAR) systems, in which lasers are used to measure the distance to the target by irradiating the target with pulsed lasers and sensing the laser pulses reflected by the target. The targets used to measure aerial data in LIDAR are air molecules or airborne particles. However, above 30,000 feet, where supersonic or hypersonic aircraft usually operate, particles are scarce. In addition, LIDAR requires relatively large, heavy and expensive lasers to emit sufficiently strong lasers for detection after reflection, especially when the altitude increases and the air density decreases accordingly. Therefore, an alternative system for pitot tubes for measuring aerial data will be practical, which is smaller, lighter and / or cheaper than LIDAR systems. Summary of the invention

[0003] One aspect of the present disclosure includes a method for measuring air data of an aircraft. The method includes emitting a laser into the air outside the aircraft by a laser disposed on the aircraft, the laser being tuned to induce a laser induced plasma channel (LIPC) in the air. The method also includes sensing at least one property of the LIPC by a sensor system disposed on the aircraft. The method also includes calculating the air data of the aircraft based on at least one property of the LIPC by a computing device disposed on the aircraft.

[0004] Another aspect of the present disclosure includes an air data system for measuring air data of an aircraft. The air data system includes a laser, a sensor system, and a computing device. The laser is disposed on the aircraft. The sensor system is also disposed on the aircraft. The computing device is disposed on the aircraft and includes at least one processor in electronic communication with the laser and the sensor system. The at least one processor is configured to cause the laser to emit laser light into the air outside the aircraft, the laser being tuned to induce LIPC in the air. The at least one processor is also configured to receive from the sensor system at least one attribute of the LIPC detected by the sensor system, and to calculate the air data of the aircraft based on the at least one attribute of the LIPC.

[0005] There are various improvements of features related to the above aspects. Other features may also be incorporated into the above aspects. These improvements and additional features may exist alone or in any combination. For example, the various features discussed below with respect to any of the illustrated examples may be incorporated into any of the above aspects alone or in any combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a schematic block diagram of an example air data system implemented on an aircraft;

[0007] Figure 2A Yes Figure 1 A schematic side view of an aircraft of an example implementation of an air data system;

[0008] Figure 2B Yes Figure 1 A schematic front view of an aircraft according to another embodiment of the air data system;

[0009] Figure 3 Yes Figure 1 A schematic side view of an aircraft of another embodiment of an air data system;

[0010] Figure 4 Yes Figure 1 A schematic side view of an aircraft of another embodiment of an air data system;

[0011] Figure 5A is a diagram showing the angle of attack of an aircraft. Figure 4 A schematic diagram of an air data system is shown;

[0012] Figure 5B is a diagram showing the method for measuring the sideslip angle of an aircraft. Figure 4 A schematic diagram of the air data system shown; and

[0013] Figure 6 is a flow chart of an example method of measuring airborne data of an aircraft.

[0014] Although specific features of the various examples may be shown in some drawings and not in others, this is for convenience only. Any feature of any drawing may be referenced and / or claimed in combination with any feature of any other drawing.

[0015] Unless otherwise indicated, the drawings provided herein are intended to illustrate features of the examples of the present disclosure. It is believed that these features can be applied to a variety of systems including one or more examples of the present disclosure. As such, the drawings are not intended to include all conventional features known to those of ordinary skill in the art required to practice the examples disclosed herein. DETAILED DESCRIPTION

[0016] Examples of the systems and methods described herein include air data systems. The air data system includes a laser, a sensor system, and a computing device. The computing device is configured to cause a laser to emit a laser into the air outside an aircraft, the laser being tuned to induce a laser-induced plasma channel (LIPC) in the air. LIPC is not a reflection of the emitted laser, but rather the emitted laser is absorbed by the air, thereby converting a portion of the air into plasma. The plasma then emits radiation at characteristic visible and near-visible wavelengths (usually unrelated to the wavelength of the induced laser) and is conductive. The laser energy required to produce LIPC is much less than the laser energy required to produce detectable reflections of the laser itself from air molecules or particles (especially at high altitudes). Therefore, the systems and methods described herein can be implemented with lasers that are relatively smaller, lighter, and / or cheaper than the lasers required to implement a LIDAR system on an aircraft.

[0017] In some examples, the air data includes airspeed. The sensor system captures a position offset of the LIPC relative to the aircraft over a known time interval, and the computer system calculates the airspeed based on the position offset and the time interval. Additionally or alternatively, the air data includes air density, and the computer system calculates the air density based on the intensity of visible or near-visible emitted radiation from the LIPC, or based on the intensity of a radar signal emitted from the sensor system and reflected from the conductive LIPC.

[0018] In some embodiments, the sensor system of the air data system includes a camera. The camera takes images of the LIPC (i.e., radiation emitted from the plasma in the LIPC) at different times. The images are used to measure air data of the aircraft, including the airspeed of the aircraft and / or the air density outside the aircraft. Additionally or alternatively, the sensor system includes a radar. Radar waves emitted from the radar are reflected by the LIPC. The reflected radar waves are sensed by the radar and used to measure air data of the aircraft, such as airspeed and air density. In certain embodiments, the air data system includes multiple sensor systems. The signals acquired by the multiple sensor systems can be used to measure the three-dimensional (3D) orientation of the aircraft, such as the angle of attack and / or sideslip angle of the aircraft.

[0019] Figure 1 1 is a schematic block diagram of an example of an air data system 100 implemented on an aircraft 101 for measuring air data. The air data may include at least one of an airspeed of the aircraft 101 and an air density of ambient air outside the aircraft 101. The air data system 100 includes a laser 102, a sensor system 104, and a computing device 106. The laser 102 and the sensor system 104 are disposed on the aircraft 101. The computing device 106 may be disposed on the aircraft 101 or remote from the aircraft 101.

[0020] The laser 102 is configured to emit laser light toward air 108 outside the aircraft 101 flowing through the aircraft 101. More specifically, the laser 102 is tuned to induce LIPC 110 in the air 108. The LIPC 110 typically exists for less than one second, emits light in the visible and / or near-visible wavelength range (the range depends on the properties of the air molecules and / or any particles in the air), and also reflects radar signals. In some examples, the laser 102 is a short pulse laser capable of creating LIPC 110 in the air 108, which is small enough to fit on a tabletop, and / or weighs less than 30 pounds. The laser 102 can be implemented by an off-the-shelf commercial laser with a pulse duration of tens of femtoseconds. Since the air travels less than a nanometer in the duration of the laser pulse, such a laser is capable of inducing LIPC in the air at hypersonic speeds (even 1000 meters per second). Although a single laser 102 is shown, in some examples, the air data system 100 includes more than one laser 102. This improves reliability, enables more granular measurements of airborne data, and can facilitate additional measurements. For example, if a first laser 102 is on the left side of aircraft 101 and a second laser 102 is on the right side of aircraft 101, the airspeed difference measured from the corresponding induced LIPC 110 on both sides of aircraft 101 enables calculation of the turn rate of aircraft 101.

[0021] exist Figure 2A In the example shown, laser 102 is positioned on aircraft 101 to emit laser light upward, which helps avoid directing the laser light toward another object. Alternatively, laser 102 can be positioned to emit laser light in any suitable direction. For example, in Figure 2B In the example shown, the laser 102 is positioned to emit laser light laterally at a laser beam dump 210 mounted on a wing tip 212 of the aircraft 101. Alternatively, the laser beam dump 210 is mounted at any suitable location on the aircraft 101, or no laser beam dump is included. The laser beam dump 210 is configured to absorb any portion of the laser light that travels beyond the induced LIPC 110. In some examples, the laser beam dump 210 includes a laser light absorbing surface so that the laser light emitted by the laser 102 does not travel beyond the range of the aircraft 101.

[0022] Aircraft 101 may include other safety mechanisms associated with laser 102. In some examples, computing device 106 is programmed to automatically deactivate laser 102 in response to landing gear of aircraft 101 making contact with the ground, such as by shutting off power to laser 102 or by another suitable mechanism. In some examples, laser 102 operates at a wavelength that prevents emitted laser light from propagating more than a few meters through the air.

[0023] The sensor system 104 is configured to sense properties of the LIPC 110, such as the position of the LIPC 110 relative to the sensor system 104, or the intensity or brightness of the LIPC 110. The sensor system 104 includes, for example, a camera 202 (in Figure 2A ) or a radar transmitter and receiver (collectively referred to herein as radar 302) (shown in Figure 3 10). Additionally or alternatively, sensor system 104 includes other sensors that can be used to sense properties of LIPC 110 and enable air data system 100 to function as described herein. Sensor system 104 is positioned on aircraft 101 at a location that enables sensor system 104 to detect signals from LIPC 110. That is, sensor system 104 is positioned so that signals emitted or reflected from LIPC 110 can reach sensor system 104. For example, if sensor system 104 includes camera 202, camera 202 is positioned so that LIPC 110 is within the camera's field of view. If sensor system 104 includes radar 302, radar 302 is positioned so that radar waves emitted from radar 302 can reach LIPC 110 and reflect back to radar 302.

[0024] Once induced, LIPC 110 remains stationary in air 108 while aircraft 101 continues to travel at the airspeed. In some examples, after induction of LIPC 110, properties of LIPC 110 sensed by sensor system 104 are used to derive measurements of the movement of LIPC 110 relative to aircraft 101, i.e., measurements of the movement of aircraft 101 relative to air 108. For example, the speed of LIPC 110 relative to aircraft 101 is the same as the airspeed of aircraft 101, and therefore, the airspeed of aircraft 101 can be measured by measuring the speed of LIPC 110 relative to aircraft 101. The three-dimensional movement of aircraft 101 can also be measured by, for example, measuring the movement and position of LIPC 110 relative to aircraft 101 using two or more sensor systems 104.

[0025] The computing device 106 includes at least one processor 112 in communication with at least one memory 114. As used herein, the terms "processor" and "computer" and related terms (such as "processing device", "computing device" and "controller") are not limited to those integrated circuits known in the art as computers, but refer generally to processors, processing devices, controllers, general-purpose central processing units (CPUs), graphics processing units (GPUs), microcontrollers, microcomputers, programmable logic controllers (PLCs), reduced instruction set computers (RISC) processors, field programmable gate arrays (FPGAs), digital signal processing (DSP) devices, application-specific integrated circuits (ASICs), and other programmable circuits or processing devices capable of performing the functions described herein, and these terms are used interchangeably herein. The above is merely an example, and is therefore not intended to limit the definition or meaning of the terms processor, computing device, and related terms in any way.

[0026] In the examples described herein, the memory 114 may include, but is not limited to, non-transitory computer-readable media, such as flash memory, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), and non-volatile RAM (NVRAM). As used herein, the term "non-transitory computer-readable medium" is intended to mean any tangible computer-readable medium, including but not limited to non-transitory computer storage devices (including but not limited to volatile and non-volatile media, and removable and non-removable media), such as firmware, physical and virtual memory, CD-ROM, DVD, and any other digital source (such as a network or the Internet) and digital devices yet to be developed, with the only exception of temporary propagation signals. Alternatively, a floppy disk, a compact disk-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disk (DVD), or any other computer-based device implemented in any method or technology for short-term or long-term storage of information (such as computer-readable instructions, data structures, program modules and submodules or other data) may also be used. Thus, the methods described herein may be encoded as executable instructions embodied in a non-transitory computer-readable medium, such as "software" and "firmware." Furthermore, as used herein, the terms "software" and "firmware" are interchangeable and include any computer program stored in a memory for execution by a personal computer, workstation, client, and server. Such instructions, when executed by a processor, cause the processor to perform at least a portion of the methods described herein.

[0027] In this example, computing device 106 also includes a laser interface 116 and a sensor interface 120, each in electronic communication with processor 112. Laser interface 116 enables processor 112 to receive status and monitoring data from laser 102, and to transmit operator commands and preprogrammed (e.g., stored in computer executable form in memory 114) commands to laser 102 (these commands cause laser 102 to emit lasers at selected times and for selected durations), and to otherwise function as described herein. Sensor interface 120 enables processor 112 to receive status, sensed data, and monitoring data from sensor system 104, and to transmit operator commands and preprogrammed (e.g., stored in computer executable form in memory 114) commands to sensor system 104 (these commands cause sensor system 104 to capture data at selected times), and to otherwise function as described herein. Alternatively, computing device 106 interfaces with laser 102 and / or sensor system 104 in any suitable manner that enables air data system 100 to function as described herein.

[0028] Furthermore, in the examples described herein, the additional input channels may be, but are not limited to, computer peripherals associated with an operator interface such as a mouse and keyboard. Alternatively, other computer peripherals may be used, which may include, for example, but are not limited to, a scanner. Furthermore, in the examples described herein, the additional output channels may include, but are not limited to, an operator interface monitor.

[0029] In operation, computing device 106 is configured to control laser 102 and sensor system 104, receive signals from sensor system 104 indicating properties of LIPC 110, and calculate airborne data of aircraft 101 based on the signals. In the illustrated example, computing device 106 is implemented separately from a flight controller (not shown) of aircraft 101, and is operable to receive commands, data, and other suitable signals from and send commands, data, and other suitable signals to the flight controller of aircraft 101. Alternatively, computing device 106 is integrated with the flight controller of aircraft 101 (e.g., processor 112 and / or memory 114 may be shared with the flight controller of aircraft 101).

[0030] In this example, components of air data system 100 do not protrude beyond the outer skin profile of aircraft 101 into the airflow when aircraft 101 is in flight. Thus, air data system 100 may operate at hypersonic airspeeds without overheating and is less susceptible to damage during ground operations than at least some known air data systems.

[0031] Figure 2Ais a schematic side view of an aircraft 101 illustrating an example implementation 200 of an air data system 100. In implementation 200, the sensor system 104 includes a camera 202 disposed on the aircraft 101. The laser 102 is positioned adjacent to an outer skin 208 of the aircraft 101 and is configured to emit laser light toward the air outside the aircraft 101 to induce the LIPC 110. In this example, as described above, the laser 102 is positioned within the fuselage 204 of the aircraft 101 and is oriented to emit laser light upward. Alternatively, the laser 102 is positioned at any suitable location on the aircraft 101, such as a wing (not shown) or a vertical stabilizer 206 of the aircraft 101, and is oriented to emit laser light in any suitable direction.

[0032] In embodiment 200, camera 202 is positioned relative to laser 102 such that LIPC 110 appears in the field of view of camera 202. In this example, camera 202 is positioned within fuselage 204 behind laser 102 and oriented upward to observe LIPC 110 as aircraft 101 travels beneath LIPC 110. Alternatively, camera 202 is positioned relative to laser 102 at any suitable location on aircraft 101, such as a wing (not shown) or vertical stabilizer 206 of aircraft 101, and oriented in any suitable direction to observe LIPC 110 during the short time window that LIPC 110 remains visible after being induced.

[0033] In operation, air 108 is moved at a velocity V air Flowing through aircraft 101. Processor 112 transmits a signal to laser 102, which causes laser 102 to fire a pulse at time t0, thereby creating LIPC 110 in air 108 flowing through aircraft 101. LIPC 110 contains a large number of ions and free electrons. For at least a few milliseconds, it glows brightly and also conducts electricity as it moves with the airflow to subsequent positions relative to aircraft 101 (shown at times t1, t2, and t3). The narrowing of the line used to illustrate LIPC 110 at subsequent times illustrates the gradual decay of the intensity of LIPC 110 over time.

[0034] The visible radiation emitted by LIPC 110 enables it to be tracked by camera 202. Processor 112 transmits a signal to camera 202 that causes camera 202 to capture an image at at least one known time after t0 (e.g., time t1, t2, and t3). Camera 202 sends the image data to computing device 106. Processor 112 of computing device 106 locates LIPC 110 in each image and uses image processing techniques to estimate the displacement of LIPC 110 through the camera's field of view over the known time interval, and therefore the speed at which LIPC 110 is moving. This speed is the airspeed V of aircraft 101. air .

[0035] In some examples, the processor 112 detects a first displacement of the LIPC 110 between a first image of the LIPC 110 captured at a first time point (e.g., t1) and a second image of the LIPC 110 captured at a second time point (e.g., t2), and calculates the airspeed by removing the first bit by the time interval between the first time point and the second time point (e.g., Δt=t2-t1). In other examples, the airspeed is calculated by averaging the results from multiple time intervals. For example, the processor 112 also detects a second displacement of the LIPC 110 between a third image of the LIPC captured at a third time point (e.g., t3) and a second image of the LIPC 110 captured at the second time point, removes the second bit by the time interval between the second time point and the third time point, and calculates the airspeed by averaging the speed results obtained from the first time point and the second time point with the speed results obtained from the second time point and the third time point. Images of the LIPC 110 captured by the camera 202 at any number of additional time points can be used to further refine the averaging technique. Alternatively, at the time of laser 102 emission (t0), the known deviation of camera 202 from laser 102 is used to determine the position of LIPC 110 relative to camera 202, at a known time t1 after laser 102 emission, camera 202 captures a single image, and processor 112 detects the displacement from the known original position in the single image and calculates the airspeed by dividing by the time interval (Δt=t1-t0).

[0036] Additionally or alternatively, the air density of the air 108 is determined using the camera 202 as the air data. More specifically, the brightness or intensity of the LIPC 110 is related to the air density of the air 108. Therefore, in some examples, the camera 202 is configured to detect the intensity of the LIPC 110 in at least one image (e.g., captured at any one of t1, t2, and t3), and the processor 112 is configured to calculate the air density of the air outside the aircraft based on the detected intensity. In some examples, intensity-to-density calibration data that relates the detected intensity to the air density of the air 108 is stored in the memory 114 and is used by the processor 112 to convert the detected intensity value to a density value. For each combination of laser type, laser tuning (e.g., frequency / energy setting of the laser 102), time interval between induction of the LIPC 110 and image capture, and camera type, the intensity-to-density calibration data can be obtained empirically at various air densities. In some examples, the processor 112 calculates the air density by averaging the results obtained from multiple camera images.

[0037] Figure 3 is a schematic side view of aircraft 101 illustrating another example implementation 300 of air data system 100. In implementation 300, sensor system 104 includes radar 302 disposed on aircraft 101. Laser 102 is substantially as described above with respect to implementation 200.

[0038] As described above, the LIPC 110 induced by the laser light emitted from the laser 102 is conductive and is therefore capable of reflecting radar waves emitted from the radar 302. In the embodiment 300, the radar 302 is positioned relative to the laser 102 so that the emitted laser light is approximately tangential to the wavefront of the radio wave 304 emitted from the radar 302, which helps to reflect the emitted or "first" radio wave 304 from the LIPC 110 as a reflected or "second" radio wave 306. In the illustrated example, the laser 102 is positioned within the fuselage 204 and is oriented to emit laser light upward, and the radar 302 is positioned on the vertical stabilizer 206 and is oriented to face the LIPC 110 when the aircraft 101 travels below the LIPC 110 so that the emitted laser light is tangential to the wavefront of the radio wave 304 emitted from the radar 302. Furthermore, in some examples, including the illustrated example, the radar 302 is positioned so that the direction of radar incidence and reflection is aligned with the airflow velocity vector V airThe radar 302 is approximately aligned, which reduces the geometric corrections required to convert the detected Doppler shift or pulse return travel time to airspeed. Alternatively, the radar 302 is positioned at any suitable location on the aircraft 101 relative to the laser 102, such as a wing (not shown) or fuselage 204 of the aircraft 101, and is oriented in any suitable direction to detect the LIPC 110 during the short time window that it remains visible after being induced.

[0039] In operation, air 108 is moved at a velocity V air Flowing through aircraft 101. Processor 112 transmits a signal to laser 102, which causes laser 102 to fire a pulse at time t0, thereby creating LIPC 110 in air 108 flowing through aircraft 101. LIPC 110 contains a large number of ions and free electrons. For at least a few milliseconds, it glows brightly and also conducts electricity sufficiently to reflect radio waves as it moves with the airflow to subsequent positions relative to aircraft 101 (shown at times t1, t2, and t3). The narrowing of the line used to illustrate LIPC 110 at subsequent times illustrates the gradual decay of the conductivity of LIPC 110 over time.

[0040] The conductivity of LIPC 110 enables it to be tracked by camera 202. Processor 112 transmits a signal to radar 302, which causes radar 302 to transmit a first radio wave 304 in pulses at at least one known time after t0 (e.g., time t1, t2, and t3). The first radio wave 304 of each pulse is reflected from LIPC 110 as a second radio wave 306. Radar 302 detects the returning second radio wave 306 and sends the detection data to computing device 106. Processor 112 of computing device 106 calculates airspeed at a time corresponding to each radar pulse using known radar signal processing techniques. For example, processor 112 uses the Doppler shift of second radio wave 306 relative to first radio wave 304 to calculate the speed at which LIPC 110 is moving relative to radar 302. Additionally or alternatively, processor 112 uses radar pulse return times (e.g., the time from transmitting first radio wave 304 until returning second radio wave 306) to locate LIPC 110 at the time of each radar pulse to estimate the displacement of LIPC 110 within a known time interval and, therefore, the speed at which LIPC 110 is moving. In some examples, processor 112 uses both techniques. The speed is the airspeed V of aircraft 101. air Alternatively, processor 112 may derive V from the detected radar signal using any suitable technique. air .

[0041] In some examples, using the pulse return technique, the processor 112 detects a first displacement of the LIPC 110 between a first pulse of the radar 302 at a first time point (e.g., t1) and a second pulse of the radar 302 at a second time point (e.g., t2), and calculates the airspeed by removing the first bit by the time interval between the first time point and the second time point (e.g., Δt=t2-t1). In other examples, the airspeed is calculated by averaging the results from multiple time intervals. For example, the processor 112 also detects a second displacement of the LIPC 110 between a third pulse of the radar 302 at a third time point (e.g., t3) and a second pulse of the radar 302 at the second time point, removes the second bit by the time interval between the second time point and the third time point, and calculates the airspeed by averaging the speed results obtained from the first time point and the second time point with the speed results obtained from the second time point and the third time point. The position of the LIPC 110 detected by the radar 302 at any number of additional time points can be used to further refine the averaging technique. Alternatively, at the time of laser 102 emission (t0), the known deviation of radar 302 from laser 102 is used to determine the position of LIPC 110 relative to radar 302, at a known time t1 after laser 102 emission, radar 302 is pulsed once, and processor 112 detects the displacement from the known original position at the time of the single pulse and calculates the airspeed by dividing by the time interval (Δt=t1-t0).

[0042] Similarly, in some examples, using Doppler shift techniques, radar 302 is pulsed a single time at a known time t1 after laser 102 is emitted, and processor 112 detects the Doppler shift in second radio wave 306 from the single pulse time and calculates airspeed based on the Doppler shift. Alternatively, processor 112 averages the speed results obtained from the detected Doppler shift of radar pulses at multiple points in time.

[0043] Additionally or alternatively, the radar 302 is used to determine the air density of the air 108 as the air data. More specifically, the radio wave reflectivity of the LIPC 110 is related to the air density of the air 108. Therefore, in some examples, the radar 302 is configured to detect the intensity of the second radio wave 306 in the detection data (e.g., the detection data captured at any one of t1, t2, and t3), and the processor 112 is configured to calculate the air density of the air outside the aircraft based on the detected intensity. In some examples, intensity-to-density calibration data that relates the detected intensity to the air density of the air 108 is stored in the memory 114 and is used by the processor 112 to convert the detected intensity value to the density value. For each combination of laser type, laser tuning (e.g., frequency / energy setting of the laser 102), time interval between induction of the LIPC 110 and radar data capture, and radar type and tuning (e.g., frequency / energy setting of the radar 302), the intensity-to-density calibration data can be empirically obtained at various air densities. In some examples, processor 112 calculates air density by averaging results obtained from multiple radar pulses.

[0044] Because the distance that radio waves 304 and 306 need to travel is relatively small, in some examples, radar 302 can operate with a relatively short range or low power. Therefore, radar 302 can be implemented using relatively small, lightweight, and / or inexpensive hardware.

[0045] As described above, the frequencies of the sensor system 104 and the laser 102 need not overlap. In other words, in some examples, the laser 102 is configured to emit laser light within a first frequency range, and the sensor system 104 is configured to sense at least one property of the LIPC 110 by detecting the emission from the LIPC 110 within a second frequency range that does not overlap with the first frequency range. Thus, unlike LIDAR (where the laser and sensor system use the same frequency or frequency range to emit and detect reflected laser light), the frequency of the laser light emitted by the laser 102 is independent of the frequency of the radiation emitted by the LIPC 110 (and independent of the frequency employed by the radar 302). Furthermore, in some examples, the combination of the laser 102 and the sensor system 104 is selected to reduce or eliminate the sensitivity of the air data measurements to environmental effects (such as icing and / or shock waves / heating). Thus, the air data system 100 is capable of operating in environmental conditions (e.g., ice, hypersonic flight) where conventional pitot tube systems may degrade, and is suitable as a primary air data system or as a backup to conventional pitot tube systems.

[0046] Figure 4is a schematic side view of an aircraft 101 illustrating another example implementation 400 of an air data system 100. The implementation 400 includes a plurality of sensor systems 104 disposed on the aircraft 101. Although the plurality of sensor systems 104 are illustrated as two sensor systems 104, the plurality of sensor systems 104 may alternatively include any suitable number of sensor systems 104. For example, each of the plurality of sensor systems 104 includes at least one of a camera 202 or a radar 302.

[0047] Sensor systems 104 are offset, i.e., spaced apart from one another, on aircraft 101, and each sensor system is positioned to detect signals from the same LIPC 110. In the example shown, a first sensor system 104 is positioned on fuselage 204 aft of laser 102 and oriented upward to view LIPC 110 as aircraft 101 travels beneath LIPC 110, and a second sensor system 104 is positioned on vertical stabilizer 206 and oriented to face LIPC 110 as aircraft 101 travels beneath LIPC 110. Additionally or alternatively, each of multiple sensor systems 104 is positioned on aircraft 101 at any suitable location that enables air data system 100 to function as described herein. For example, one of multiple sensor systems 104 is positioned at a wingtip 212 ( Figure 2B ) on or near the

[0048] In operation, processor 112 is programmed to cause multiple sensor systems 104 to simultaneously capture data from LIPC 110 at least one known time after laser 102 is pulsed to create LIPC 110. In some examples, the simultaneously measured positions of LIPC 110 relative to each sensor system 104, combined with the known offsets between multiple sensor systems 104 on aircraft 101, facilitate calculation of a 3D state of aircraft 101. Suitable parameters of the 3D state of aircraft 101 may be calculated using any suitable known geometric algorithm.

[0049] For example, Figure 5A1 is a schematic diagram showing an air data system 100 for measuring an angle of attack α of an aircraft 101. More specifically, the aircraft 101 is shown in solid lines at time t0 when the laser 102 is caused to fire to create the LIPC 110, and the aircraft 101 is shown in dashed lines at a subsequent time t1 when the sensor system 104 is caused to collect data. The LIPC 110 is stationary relative to the air 108, and thus the aircraft 101 is already traveling below the LIPC 110 at time t1. The processor 112 is programmed to calculate the angle of attack α based on the simultaneously measured positions of the LIPC 110 relative to each sensor system 104, combined with the known offsets between the multiple sensor systems 104.

[0050] For another example, Figure 5B 1 is a schematic diagram showing an air data system 100 for measuring a sideslip angle β of an aircraft 101. More specifically, the aircraft 101 is shown in solid lines at time t0 when the laser 102 is caused to fire to create the LIPC 110, and the aircraft 101 is shown in dashed lines at a subsequent time t1 when the sensor system 104 is caused to collect data. Although based on the example placement of the laser 102, the LIPC 110 would be created as a vertical column directly above the aircraft 101, for ease of illustration, the LIPC 110 is shown offset laterally from the aircraft 101. The LIPC 110 is stationary relative to the air 108, and therefore the aircraft 101 is already traveling below the LIPC 110 at time t1. The processor 112 is programmed to calculate the sideslip angle β based on the simultaneously measured positions of the LIPC 110 relative to each sensor system 104, combined with the known offsets between the multiple sensor systems 104.

[0051] In some examples, air data system 100 is implemented on aircraft 101 implemented as a rotorcraft. It is difficult to measure air data of the rotorcraft, such as airspeed, using conventional air data systems on aircraft 101 because the rotorcraft creates a downwash region in which the local air speed is deflected in a complex manner due to the rotor blades of the rotorcraft. Therefore, the speed of the air in the rotor downwash region is different from the speed of the air outside the region, which is the airspeed of the rotorcraft to be measured. In some examples where aircraft 101 is a rotorcraft, laser 102 is configured to emit laser light beyond the downwash region of the rotorcraft and induce LIPC 110 outside the downwash region. As described above, sensor system 104 is configured to sense at least one attribute of LIPC 110 outside the downwash region, and as described above, computing device 106 is configured to calculate air data of the rotorcraft based on the detected attribute of LIPC 110.

[0052] Figure 6 6 is a flow chart of an example method 600 for measuring air data of aircraft 101. Method 600 includes transmitting 602 a laser into air outside the aircraft by a laser disposed on the aircraft, such as laser 102. The laser is tuned to induce LIPC in the air. Method 600 also includes sensing 604 at least one property of the LIPC by a sensor system disposed on the aircraft, such as sensor system 104. Method 600 also includes calculating 606 air data of the aircraft based on the property of the LIPC by a computing device disposed on the aircraft, such as computing device 106. Additionally or alternatively, method 600 includes other steps consistent with the description of air data system 100 above.

[0053] Example technical effects of the methods, systems, and apparatus described herein include at least one of the following: (a) the air data system has increased reliability over a wide range of environmental conditions (such as, but not limited to, icing or hypersonic flight); (b) the laser-based air data system can operate using relatively short-range, low-power lasers compared to conventional laser-based air data systems; (c) the air data system measures the 3D orientation of the aircraft (such as angle of attack and / or angle of sideslip); (d) the air data system has no parts that "stick out" in the airflow or protrude from the aircraft, thereby reducing the risk of damage during ground operations; and (e) the air data system is operable to measure air data outside the downwash region of a rotorcraft.

[0054] The systems and methods described herein are not limited to the specific examples described herein, but rather, components of the systems and / or steps of the methods may be used independently and separately from other components and / or steps described herein. As one example, the air data system 100 may be implemented on a ground-based vehicle. As another example, the air data system 100 may be implemented in a wind tunnel. More specifically, the laser 102 and the sensor system 104 are positioned relative to the wind tunnel, with the computing device 106 communicating with the laser 102 and the sensor system 104. The air data system 100 is used to measure a flow field in the wind tunnel.

[0055] As used herein, an element or step recorded in the singular and beginning with the word "a" or "an" should be understood as not excluding multiple elements or steps, unless such exclusion is explicitly recorded. In addition, reference to "an example", "example" or "some examples" of the present disclosure is not intended to be interpreted as excluding the existence of other examples that also contain the recorded features.

[0056] In addition, the present invention includes examples according to the following clauses:

[0057] Clause 1: A method for measuring airborne data of an aircraft, the method comprising:

[0058] emitting laser light into the air outside the aircraft by means of a laser disposed on the aircraft, wherein the laser is tuned to induce a laser induced plasma channel (LIPC) in the air;

[0059] sensing at least one property of the LIPC via a sensor system disposed on the aircraft; and

[0060] The air data of the aircraft is calculated based on the at least one attribute of the LIPC by a computing device disposed on the aircraft.

[0061] Clause 2. The method of clause 1, wherein the calculating the air data comprises calculating, by the computing device, at least one of an airspeed of the aircraft or an air density of air outside the aircraft.

[0062] Clause 3. The method of clause 1, wherein the sensor system comprises a camera, and wherein sensing the at least one property comprises capturing at least one image of the LIPC using the camera.

[0063] Clause 4. The method according to clause 3, wherein:

[0064] The capturing of the at least one image comprises: capturing a first image of the LIPC at a first point in time, and capturing a second image of the LIPC at a second point in time; and

[0065] The calculating the air data includes: detecting, by the computing device, a displacement of the LIPC from the first image to the second image, and calculating, by the computing device, an airspeed of the aircraft based on the displacement.

[0066] Clause 5. The method according to clause 3, wherein:

[0067] The sensing the at least one property comprises detecting an intensity of the LIPC in the at least one image; and

[0068] The calculating the air data includes calculating an air density of air outside the aircraft based on the intensity.

[0069] Clause 6. The method of clause 5, wherein the calculating the air density comprises applying, by the computing device, intensity-to-density calibration data to the detected intensity to obtain the air density, and wherein the intensity-to-density calibration data corresponds to tuning of the laser.

[0070] Clause 7. The method of Clause 1, wherein emitting the laser light comprises emitting the laser light toward a beam dump disposed on the aircraft, and wherein the beam dump is configured to absorb the laser light.

[0071] Clause 8. The method of clause 1, wherein emitting the laser comprises emitting the laser within a first frequency range, and wherein sensing the at least one property of the LIPC comprises detecting emissions from the LIPC within a second frequency range that does not overlap with the first frequency range.

[0072] Clause 9. A method according to clause 1, wherein the sensor system includes a radar, and wherein the sensing of the at least one property of the LIPC includes: transmitting a first radio wave toward the LIPC by the radar, and receiving a second radio wave by the radar, the second radio wave including at least a portion of the first radio wave reflected by the LIPC.

[0073] Clause 10. The method of clause 9, wherein the calculating the air data comprises:

[0074] detecting, by the computing device, at least one of a Doppler frequency shift of the second radio wave or a pulse return time of the second radio wave; and

[0075] An airspeed of the aircraft is calculated based on at least one of the Doppler shift or the pulse return time.

[0076] Clause 11. The method of clause 9, wherein:

[0077] said sensing said at least one property comprises detecting a strength of said second radio wave; and

[0078] The calculating the air data includes calculating an air density of air outside the aircraft based on the intensity of the second radio wave.

[0079] Clause 12. A method according to clause 11, wherein the calculating the air density includes applying intensity-to-density calibration data to the detected intensity to obtain the air density by the computing device, wherein the intensity-to-density calibration data corresponds to the tuning of the laser and the tuning of the radar.

[0080] Clause 13. The method of clause 1, wherein:

[0081] The sensor system includes a first sensor disposed at a first location on the aircraft and a second sensor disposed at a second location on the aircraft, wherein the second location is offset from the first location;

[0082] The sensing the at least one property of the LIPC comprises sensing a respective position of the LIPC relative to each of the first sensor and the second sensor; and

[0083] The method also includes estimating, by the computing device, a three-dimensional state of the aircraft based on the corresponding positions and the deviations.

[0084] Clause 14. An air data system for measuring air data of an aircraft, the system comprising:

[0085] A laser disposed on the aircraft;

[0086] A sensor system disposed on the aircraft; and

[0087] A computing device disposed on the aircraft, the computing device comprising at least one processor in electronic communication with the laser and the sensor system, wherein the at least one processor is configured to:

[0088] causing the laser to emit laser light into air outside the vehicle, wherein the laser is tuned to induce a laser induced plasma channel (LIPC) in the air;

[0089] receiving from the sensor system at least one attribute of the LIPC detected by the sensor system; and

[0090] The air data of the aircraft is calculated based on the at least one attribute of the LIPC.

[0091] Clause 15. The air data system of clause 14, wherein the sensor system comprises a camera, and wherein the at least one attribute comprises at least one image of the LIPC captured using the camera.

[0092] Clause 16. The air data system of clause 15, wherein the at least one processor is further configured to:

[0093] causing the camera to capture a first image of the LIPC at a first point in time and to capture a second image of the LIPC at a second point in time;

[0094] detecting a displacement of the LIPC from the first image to the second image; and

[0095] An airspeed of the aircraft is calculated based on the displacement.

[0096] Clause 17. An air data system according to clause 15, wherein the camera is configured to detect an intensity of the LIPC in the at least one image, and wherein the at least one processor is further configured to calculate an air density of the air outside the aircraft based on the intensity.

[0097] Clause 18. The air data system of clause 17, wherein the at least one processor is further configured to apply intensity to density calibration data to the detected intensity to obtain air density, and wherein the intensity to density calibration data corresponds to tuning of the laser.

[0098] Clause 19. The air data system of Clause 14, further comprising a beam dump disposed on the aircraft, and the beam dump is configured to absorb the laser light emitted from the laser.

[0099] Clause 20. An air data system as described in clause 14, wherein the laser is tuned to transmit the laser within a first frequency range, and wherein the sensor system is configured to detect emissions from the LIPC within a second frequency range that does not overlap with the first frequency range.

[0100] Clause 21. An air data system according to clause 14, wherein the sensor system includes a radar configured to transmit a first radio wave toward the LIPC induced by the laser and receive a second radio wave, the second radio wave comprising at least a portion of the first radio wave reflected by the LIPC.

[0101] Clause 22. The air data system of clause 21, wherein the at least one processor is further configured to:

[0102] detecting at least one of a Doppler frequency shift of the second radio wave or a pulse return time of the second radio wave; and

[0103] An airspeed of the aircraft is calculated based on at least one of the Doppler shift or the pulse return time.

[0104] Clause 23. An air data system according to clause 21, wherein the radar is further configured to detect the intensity of the second radio wave, and wherein the at least one processor is further configured to calculate the air density of the air outside the aircraft based on the intensity of the second radio wave.

[0105] Clause 24. An air data system according to clause 23, wherein the at least one processor is further configured to apply intensity to density calibration data to the detected intensity to obtain air density, and wherein the intensity to density calibration data corresponds to tuning of the laser and tuning of the radar.

[0106] Clause 25. The air data system of clause 14, wherein the aircraft is a rotorcraft, and wherein the laser is configured to induce the LIPC in a region of air outside a rotor downwash region of the rotorcraft.

[0107] Clause 26. The air data system of clause 14, wherein the sensor system comprises a first sensor disposed at a first location on the aircraft and a second sensor disposed at a second location on the aircraft, wherein the second location is offset from the first location, and wherein the at least one processor is further configured to:

[0108] causing the sensor system to sense a respective position of the LIPC relative to each of the first sensor and the second sensor; and

[0109] A three-dimensional state of the aircraft is estimated based on the corresponding positions and the deviations.

[0110] This written description uses examples to disclose various examples, including the best mode, to enable those skilled in the art to practice those examples, including making and using any devices or systems and performing any incorporated methods. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

1. A method for measuring air data of an aircraft, the method comprising: emitting laser light into the air outside the aircraft by means of a laser disposed on the aircraft, wherein the laser is tuned to induce a laser-induced plasma channel (LIPC) in the air; sensing at least one property of the LIPC by a sensor system disposed on the aircraft; as well as Calculating the air data of the aircraft based on the at least one attribute of the LIPC by a computing device disposed on the aircraft; wherein the sensor system comprises a radar, and wherein sensing the at least one property of the LIPC comprises transmitting, by the radar, a first radio wave toward the LIPC, and receiving, by the radar, a second radio wave comprising at least a portion of the first radio wave reflected by the LIPC. 2 . The method of claim 1 , wherein the calculating the air data comprises calculating, by the computing device, at least one of an airspeed of the aircraft or an air density of air outside the aircraft. 3 . The method of claim 1 , wherein the sensor system further comprises a camera, and wherein the sensing the at least one property comprises capturing at least one image of the LIPC using the camera.

4. The method according to claim 3, wherein: The capturing of the at least one image comprises: capturing a first image of the LIPC at a first point in time, and capturing a second image of the LIPC at a second point in time; and The calculating the air data includes: detecting, by the computing device, a displacement of the LIPC from the first image to the second image, and calculating, by the computing device, an airspeed of the aircraft based on the displacement.

5. The method according to claim 3, wherein: The sensing the at least one property comprises detecting an intensity of the LIPC in the at least one image; and The calculating the air data includes calculating an air density of air outside the aircraft based on the intensity. 6 . The method of claim 1 , wherein the emitting the laser light comprises emitting the laser light toward a beam dump disposed on the aircraft, and wherein the beam dump is configured to absorb the laser light.

7. The method of claim 1, wherein said emitting said laser comprises emitting said laser within a first frequency range, and wherein said sensing said at least one property of said LIPC comprises detecting emissions from said LIPC within a second frequency range that does not overlap with said first frequency range.

8. The method of claim 1, wherein the calculating the air data comprises: detecting, by the computing device, at least one of a Doppler frequency shift of the second radio wave or a pulse return time of the second radio wave; as well as An airspeed of the aircraft is calculated based on at least one of the Doppler shift or the pulse return time.

9. The method according to claim 1, wherein: The sensor system includes a first sensor disposed at a first location on the aircraft and a second sensor disposed at a second location on the aircraft, wherein the second location is offset from the first location; The sensing the at least one property of the LIPC comprises sensing a respective position of the LIPC relative to each of the first sensor and the second sensor; and The method also includes estimating, by the computing device, a three-dimensional state of the aircraft based on the corresponding positions and the deviations.

10. An air data system for measuring air data of an aircraft, the system comprising: A laser disposed on the aircraft; a sensor system disposed on the aircraft; as well as A computing device disposed on the aircraft, the computing device comprising at least one processor in electronic communication with the laser and the sensor system, wherein the at least one processor is configured to: causing the laser to emit laser light into air outside the vehicle, wherein the laser is tuned to induce a laser induced plasma channel (LIPC) in the air; receiving from the sensor system at least one attribute of the LIPC detected by the sensor system; and calculating the air data of the aircraft based on the at least one attribute of the LIPC; The sensor system includes a radar configured to transmit a first radio wave toward the LIPC induced by the laser and receive a second radio wave including at least a portion of the first radio wave reflected by the LIPC.

11. The air data system of claim 10, wherein the sensor system further comprises a camera, and wherein the at least one attribute comprises at least one image of the LIPC captured using the camera.

12. The air data system of claim 11, wherein the at least one processor is further configured to: causing the camera to capture a first image of the LIPC at a first point in time and to capture a second image of the LIPC at a second point in time; detecting a displacement of the LIPC from the first image to the second image; and An airspeed of the aircraft is calculated based on the displacement.

13. The air data system of claim 11, wherein the camera is configured to detect an intensity of the LIPC in the at least one image, and wherein the at least one processor is further configured to calculate an air density of air outside the aircraft based on the intensity.

14. The air data system of claim 10, further comprising a beam dump disposed on the aircraft, and the beam dump is configured to absorb the laser light emitted from the laser.

15. The air data system of claim 10, wherein the laser is tuned to transmit the laser within a first frequency range, and wherein the sensor system is configured to detect emissions from the LIPC within a second frequency range that does not overlap with the first frequency range.

16. The air data system of claim 10, wherein the at least one processor is further configured to: detecting at least one of a Doppler frequency shift of the second radio wave or a pulse return time of the second radio wave; and An airspeed of the aircraft is calculated based on at least one of the Doppler shift or the pulse return time.

17. The air data system of claim 10, wherein the aircraft is a rotorcraft, and wherein the laser is configured to induce the LIPC in a region of air outside a rotor downwash region of the rotorcraft.

18. The air data system of claim 10, wherein the sensor system comprises a first sensor disposed at a first location on the aircraft and a second sensor disposed at a second location on the aircraft, wherein the second location is offset from the first location, and wherein the at least one processor is further configured to: causing the sensor system to sense a respective position of the LIPC relative to each of the first sensor and the second sensor; and A three-dimensional state of the aircraft is estimated based on the corresponding positions and the deviations.

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