Patent Description:
A ballonet is an air bag disposed within the outer envelope of an airship. When the ballonet is inflated, the ballonet reduces the volume within the airship available for lifting gas. Air is characteristically denser than lifting gas, therefore, the density of the airship changes as the ballonet changes volume. For example, inflating the ballonet may increase the overall mass of the airship, while deflating it will reduce the mass.

Ballonets may typically be used in non-rigid or semi-rigid airships, commonly with multiple ballonets located both fore and aft to maintain balance and to control the pitch of the airship. Accordingly, proper management of the ballonet is necessary to control the movement of the airship.

Typically, ballonet volume has been managed manually, either by feel or by using a bubble window with markings on the inside of the ballonet. For example, the pilot may stick his head into the bubble window and visually inspect the markings. Based on these markings, the pilot can determine a relative volume of the ballonet.

<CIT> discloses systems and methods for measuring a volume of a ballonet. A system may include a plurality of sensors configured to transmit a plurality of signals toward an interior surface of the ballonet to receive the plurality of signals reflected from the interior surface of the ballonet, a distance calculation module configured is for calculating a plurality of distances from the plurality of sensors to the inner surface of the ballonet using the received plurality of signals, and a mapping module configured to create a three-dimensional surface using the calculated plurality of distances. The system may further include a measurement module configured to calculate the volume of the ballonet using the three-dimensional surface.

<CIT> discloses techniques relating lighter-than-air aircraft. Such aircraft may be used for various purposes, such as providing network connectivity to areas that would otherwise lack such connectivity.

<CIT> relates to the technical field of super-pressure balloons, in particular to a volume-variable super-pressure balloon.

According to a first aspect of the invention, there is provided an airship as defined in claim <NUM>. Optional and/or preferable features are denoted in the dependent claims.

According to a second aspect of the invention, there is defined a method for controlling the operation of an airship as defined in claim <NUM>. Optional and/or preferable features are denoted in the dependent claims.

The present disclosure may provide numerous technical advantages. For example, certain embodiments provide highly accurate volume measurements for a ballonet in an airship by measuring the relative differences in distance from one or more fixed locations and predetermined distances. Such measurements may be made for even large ballonets, which when not full, may have complicated and highly irregular surfaces. As another example, one or more lasers and one or more light detectors may be used to measure the respective distances to the surface of the ballonet. A variety of configurations of the lasers and light detectors may be used based on the geometry and size of the ballonet. As yet another example, the calculated volume may be used to determine the center of mass and overall mass of air within the ballonet. This information may be used by a vehicle management system to adjust the air within the ballonet to control the movement of the airship.

Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages.

The appended drawings illustrate, and the following text describes, typical embodiments which are not to be considered limiting of the scope of the invention, but only as much as they fall within the scope of the appended claims.

For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:.

Various embodiments and examples are shown and discussed herein, to be construed in as much as they fall within the scope of the appended claims.

To facilitate a better understanding of the present disclosure, the following examples of certain embodiments are given. The following examples are not to be read to limit or define the scope of the disclosure. Embodiments of the present disclosure and its advantages are best understood by referring to <FIG>, where like numbers are used to indicate like and corresponding parts.

Measuring the volume of a ballonet is increasingly difficult as ballonets increase in size and the more variability between the volume during normal operation. For example, for larger ballonets, the relative volume is difficult to discern by only viewing a small portion of the ballonet surface, e.g., by visually inspecting markings on the ballonet. This is, at least in part, due to the fact that the ballonet surface may fold on itself or collapse in localized positions on the ballonet surface when insufficient air is disposed within the ballonet for it to maintain a continuous surface. As a result, visually inspecting a smooth region of the ballonet may not indicate that the ballonet currently has smaller volume. Similarly, the more that the ballonet decreases in volume, the more the ballonet is susceptible to folding onto itself. Thus, in such cases, it is desired to have systems and methods of accurately measuring the volume of the ballonet. The present disclosure may provide numerous technical advantages. For example, certain embodiments provide numerous technical advantages and provide highly accurate volume measurements for a ballonet in an airship by measuring the relative differences in distance from one or more fixed locations and predetermined distances. Such measurements may be made for even large ballonets, which when not full, may have complicated and highly irregular surfaces. As another example, one or more lasers and one or more light detectors may be used to measure the respective distances to the surface of the ballonet. A variety of configurations of the lasers and light detectors may be used based on the geometry and size of the ballonet. As yet another example, the calculated volume may be used to determine the center of mass and overall mass of air within the ballonet. This information may be used by a vehicle management system to adjust the air within the ballonet to control the movement of the airship.

<FIG> illustrates an example airship <NUM> having at least two ballonets <NUM>, according to certain embodiments. Airship <NUM> may be any type of airship or lighter-than-air aircraft that can navigate through the air under its own power. Airship <NUM> may use a lifting gas that is less dense than the surrounding air to provide lift to airship <NUM> to overcome gravity. Airship <NUM> may be a non-rigid, semi-rigid, or rigid airship.

In certain embodiments, airship <NUM> includes at least two ballonets <NUM>. Ballonets <NUM> are configured to be filled with air, e.g., surrounding air having the same density as the air outside of airship <NUM>. An operator of airship <NUM> may control the flow in and out of each of ballonets <NUM>. Ballonets <NUM> may be inflated, thereby reducing the volume within airship <NUM> available for lifting gas. Air is typically denser than lifting gas, therefore, the density of airship <NUM> changes as the ballonet changes volume. For example, inflating ballonets <NUM> may reduce the overall lift, while deflating ballonets <NUM> may increase lift.

Ballonets <NUM> are typically used in non-rigid or semi-rigid airships, commonly with multiple ballonets <NUM> located both fore and aft of the respective airship, e.g., airship <NUM>, to maintain balance and to control the pitch of the airship. In certain embodiments, the pitch of airship <NUM> is controlled by controlling the relative inflation of ballonets <NUM>. For example, one of ballonets <NUM> near the rear of airship <NUM> may be inflated more than one of the ballonets <NUM> near the front of airship <NUM>. This may induce airship <NUM> to pitch up because the front of airship <NUM> is less dense than the rear of airship <NUM>, e.g., due to a higher volume of lifting gas at the front of airship <NUM>.

Additionally, ballonets serve an important purpose in maintaining hull pressure within an operable range. For example, because air pressure reduces as airship <NUM> increases in altitude, a soft hull of airship <NUM> would experience greater internal pressure when rising. This internal pressure may exert unnecessary stress on the hull and if the difference between a minimum and a maximum altitude was great enough, as it could be in limited circumstances, the hull may be structurally compromised. This may have negative impacts throughout airship <NUM> because the hull is used as a mounting structure for other parts of airship <NUM>. Accordingly, maintaining the correct pressure within ballonets <NUM> is important in maintaining the pressure on exerted on the hull within the optimal ranges.

As discussed earlier, conventional techniques for measuring the volume of the ballonet are prone to inaccuracies and human error. Disclosed herein are embodiments of methods and systems that provide an accurate measurement of the volume of a ballonet, such as ballonet <NUM>, which may be used to control the operation of an airship, e.g., airship <NUM>.

<FIG> illustrate a system <NUM>, also called ballonet tracking system <NUM> disposed within ballonet <NUM> where ballonet <NUM> is in a full state and a partially full state, respectively, according to certain embodiments. ballonet tracking system <NUM> may include one or more measurement devices 130a-e located within ballonet <NUM>. For example, the illustrated example includes five measurement devices 130a-e disposed at five locations on ballonet <NUM>.

In certain embodiments, ballonet <NUM> includes a ballonet surface <NUM>. Ballonet surface <NUM> is an outer surface of ballonet <NUM> that is impermeable or semi-permeable, such that air does not escape from ballonet <NUM> without intervention. In certain embodiments, measurement devices 130a-e are disposed on a portion of ballonet surface <NUM> of ballonet <NUM> that does not change shape and/or relative position to airship <NUM> with a change of volume of ballonet <NUM>. In this manner, measurement devices 130a-e may maintain fixed locations, and in some embodiments a fixed orientation, within ballonet <NUM>.

The system <NUM> is configured to measure a plurality of distances between one or more fixed locations and one or more locations on ballonet surface <NUM> of ballonet <NUM>. For example, each of measurement devices 130a-e may be configured to emit light in a certain direction and receive the reflected light from the surface of ballonet surface <NUM>. Based on the reflected light, ballonet tracking system <NUM> may determine the distance the light traveled from the respective measurement device <NUM> to ballonet surface <NUM> (or vice versa).

In certain embodiments, measurement devices 130a-e are at a plurality of fixed locations and each oriented in a fixed orientation relative to ballonet <NUM>. For example, measurement devices 130a-e may be spread along the portion of ballonet <NUM> that does not change shape and oriented towards a respective location of ballonet <NUM> at a portion that deforms or changes position when the volume within ballonet <NUM> changes. In this example, measurement devices 130a-e may measure five distances from the locations of measurement devices 130a-e to ballonet surface <NUM> of ballonet <NUM> along their fixed orientation.

As shown in <FIG>, the distance that would be measured by measurement devices <NUM> may change as the volume of ballonet <NUM> changes. For example, ballonet surface <NUM> may change shape and deform as the volume of ballonet <NUM> decreases from a full or maximum volume. The system <NUM> is configured to determine the difference between the measured distances and a set of expected distances. The system <NUM> compares the measured distances with a corresponding set of distances corresponding to ballonet <NUM> being full. For example, the system <NUM> compares the measured distances with a set of distances along the measured orientations that is expected for ballonet <NUM> being full, e.g., ballonet surface <NUM> is expanded at its maximum. The predetermined set of distances may be obtained from an outside source, e.g., preloaded into a memory during the time of installation or production, or obtained and stored when measuring distances when ballonet <NUM> is known to be full. Based on these comparisons, ballonet tracking system <NUM> may calculate a set of differences, e.g., a set of deviations from a full state.

Thr system <NUM> is further configured to determine the present volume of ballonet <NUM> based on the calculated differences. The volume may be calculated in a variety of ways. For example, given a known geometry of ballonet <NUM> at a full state, it may be known how ballonet surface <NUM> deforms at various states of emptiness. Thus, ballonet tracking system <NUM> may be configured to compare the expected deviations with the calculated differences from the measurements from each measurement device <NUM>. As another example, a polygonal approximation of ballonet <NUM> may be constructed using the calculated differences. Using the calculated differences, ballonet tracking system <NUM> may constructed a three-dimensional shape that approximates ballonet surface <NUM> in its current state.

The volume of that three-dimensional shape may then, be used to calculate the volume of ballonet <NUM>. While a few examples have been described above of how the calculated differences may be used to determine the volume of ballonet <NUM>, any suitable algorithm or method known to persons having skill in the art for constructing the volume of ballonet <NUM> from the differences from the measured distances and the set of expected distances is contemplated in this disclosure.

In certain embodiments, ballonet tracking system <NUM> further includes at least one temperature sensor <NUM> and at least one pressure sensor <NUM>. Temperature sensor <NUM> and pressure sensor <NUM> may each be configured to measure values of temperature and pressure, respectively, inside ballonet <NUM>. This information may be used to determine the present temperature and pressure within the air contained in ballonet <NUM>. In some embodiments, ballonet tracking system <NUM> is further configured to measure a mass of air within ballonet <NUM> based the measurements from temperature sensor <NUM> and pressure sensor <NUM>, and the calculated volume of ballonet <NUM>. For example, given a known pressure, temperature, and volume of a gas, the number of molecules, and thereby the mass, of the gas may be determined. Using a simple version, known as the ideal gas law, PV=nRT, where P is the pressure, V is the volume, n is the number of molecules, R is a known constant, and T is the temperature, the number of molecules n can be calculated as n=PV/RT. Therefore, ballonet tracking system <NUM> may determine n or a mass analogue thereto using the temperature and pressure from sensors <NUM> and <NUM> with the calculated volume to determine the mass within ballonet <NUM>. More involved equations may be used depending on the level of accuracy desired or applicable in the particular application.

Additionally, ballonet tracking system <NUM>, in certain embodiments, may also determine the center of gravity of the air within ballonet <NUM>. For example, ballonet tracking system <NUM> may be configured to determine the approximate shape of ballonet <NUM> in its current state and using a presumed uniform distribution of air, determine the center of gravity. There may also be a number of other techniques known to persons having skill in the art to construct a center of gravity from the measurements obtained by ballonet tracking system <NUM>. Knowing the mass and center of gravity is useful in controlling airship <NUM>. For example, it may indicate how airship <NUM> would react to applied forces, such as by gusts of wind or deliberate propulsion on the outside of airship <NUM>.

Ballonet tracking system <NUM> is communicatively coupled to a vehicle management system <NUM> of airship <NUM>. Vehicle management system <NUM> may control various operations onboard airship <NUM>. For example, vehicle management system <NUM> may be used to control the propulsion systems of airship <NUM>, the environmental conditions for passengers and/or cargo, the flow of air in and out of ballonets <NUM>, etc. As described earlier, the volume of ballonets <NUM> may be of particular importance to controlling the movement of airship <NUM>. In this manner, vehicle management system <NUM> may be coupled to ballonet tracking system <NUM>, thereby enabling the communication of certain measurements or calculations, such as the measured distances, calculated differences in distances, or the calculated volume.

In certain embodiments, all, none, or all of the functionality of ballonet tracking system <NUM> is integrated with vehicle management system <NUM>. For example, certain processing operations, such as calculating differences or volumes, may occur within vehicle management system <NUM> in addition to or in lieu of within ballonet tracking system <NUM>. As another example, certain data, such as the predetermined set of distances, may be stored within vehicle management system <NUM> and accessed by ballonet tracking system <NUM> when needed. In this manner, certain functionality described with respect to ballonet tracking system <NUM> may be performed, in part or in whole, by components of vehicle management system <NUM>.

In certain embodiments, ballonet tracking system <NUM> is configured to measure a plurality of distances from one or more fixed locations to one or more locations on ballonet surface <NUM> of ballonet <NUM> without using additional reflective material disposed at ballonet surface <NUM>. For example, measurement devices 130a-e may be configured to emit light that reflects off of the material of ballonet surface <NUM> of ballonet. Additionally, adding pieces of reflective material to ballonet surface <NUM> of ballonet <NUM> may not enhance the measurement of distances from measurement devices 130a-e. For example, as ballonet surface <NUM> deforms with changing volume of ballonet, these pieces of reflective material may move positions with ballonet surface <NUM>. Accordingly, systems relying on the presence of the reflective material may fail to make any distance measurement, let alone an accurate measurement. In this manner, ballonet tracking system <NUM> may be configured to measure the distances to ballonet surface <NUM> of ballonet <NUM> without additional reflective material disposed on ballonet surface <NUM>.

<FIG> illustrates vehicle management system <NUM> communicatively coupled to at least a portion of the ballonet tracking system <NUM> in <FIG>, according to certain embodiments. In certain embodiments, vehicle management system <NUM> is communicatively coupled to one or more measurement devices <NUM>. For example, vehicle management system <NUM> may be communicatively coupled to all measurement devices <NUM>, one measurement device <NUM> directly as an intermediary for other measurement devices, or measurement devices <NUM> indirectly through an intermediate interface (not depicted). In this manner, vehicle management system <NUM> and measurement devices <NUM> may exchange information between them to ensure proper operation of airship <NUM>.

Vehicle management system <NUM> may include one or more interfaces <NUM>, memory <NUM>, and processing circuitry <NUM>. Measurement device <NUM> may include one or more interfaces <NUM>, memory <NUM>, and processing circuitry <NUM>. Information or data may be shared between vehicle management system <NUM> and measurement device <NUM> over a communications link via interfaces <NUM> and <NUM>. The communications link may be line link, a wireless link, or some combination thereof.

Processing circuitry <NUM>, <NUM> can be any electronic circuitry, including, but not limited to microprocessors, ASIC, ASIP, and/or state machines, that communicatively couples to one or more interfaces <NUM>, <NUM>, respectively, memory <NUM>, <NUM>, respectively. Processing circuitry <NUM>, <NUM> may be <NUM>-bit, <NUM>-bit, <NUM>-bit, <NUM>-bit or of any other suitable architecture. Processing circuitry <NUM>, <NUM> may include an ALU for performing arithmetic and logic operations, processor registers that supply operands to the ALU and store the results of ALU operations, and a control unit that fetches instructions from memory <NUM>, <NUM>, respectively, and executes them by directing the coordinated operations of the ALU, registers and other components. Processing circuitry <NUM>, <NUM> may include other hardware and software that operates to control and process information. Processing circuitry <NUM>, <NUM> executes software stored in memory <NUM>, <NUM>, respectively, to perform any of the functions of vehicle management system <NUM>, ballonet tracking system <NUM>, and measurement device <NUM>, respectively, described herein. Processing circuitry <NUM>, <NUM> may control the operation of vehicle management system <NUM> and measurement device <NUM>, respectively, for example by calculating the volume of ballonet <NUM> using the calculated differences based on the measurements obtained via interface <NUM> and information from memory <NUM>, <NUM>. Processing circuitry <NUM>, <NUM> may be a programmable logic device, a microcontroller, a microprocessor, any suitable processing device, or any suitable combination of the preceding. Processing circuitry <NUM>, <NUM> is not limited to a single processing device and may encompass multiple processing devices.

Memory <NUM>, <NUM> may be any suitable type of memory. Memory <NUM>, <NUM> may store, either permanently or temporarily, data, operational software, or other information for processing circuitry <NUM>, <NUM>, respectively. Memory <NUM>, <NUM> may include any one or a combination of volatile or non-volatile local or remote devices suitable for storing information. For example, memory <NUM>, <NUM> may include RAM, ROM, magnetic storage devices, optical storage devices, or any other suitable information storage device or a combination of these devices. The software represents any suitable set of instructions, logic, or code embodied in a computer-readable storage medium. For example, the software may be embodied in Memory <NUM>, <NUM>, a disk, a CD, or a flash drive. In particular embodiments, the software may include an application executable by processing circuitry <NUM>, <NUM> to perform one or more of the functions of vehicle management system <NUM>, ballonet tracking system <NUM>, and measurement device <NUM>, respectively, as described herein.

Memory <NUM>, <NUM> may store one or more instructions or data, which when processed by processing circuitry <NUM>, <NUM>, cause vehicle management system <NUM>, ballonet tracking system <NUM>, and measurement device <NUM>, respectively, to perform any of the functions described in this disclosure. For example, memory <NUM> may store instructions how to correlate calculated differences in distances to calculate a volume of ballonet. As another example, memory <NUM> may store instructions of how to adjust the propulsion system parameters based on the volume of ballonet <NUM> calculated by ballonet tracking system <NUM>.

Measurement devices <NUM> may be any suitable device capable of measuring a distance across air from the location of measurement device <NUM> to a surface of ballonet surface <NUM> of ballonet <NUM>. In certain embodiments, measurement device <NUM> may further include a light emitter <NUM> and light-receiver <NUM>. Light emitter <NUM> is configured to emit light along a predetermined path relative to measurement device <NUM>. Light receiver <NUM> is configured to receive and/or detect light from outside measurement device <NUM>.

Measurement device <NUM> is further configured to determine the distance from measurement device <NUM> to ballonet surface <NUM> of ballonet <NUM> along a particular orientation. For example, measurement device <NUM> may store a time value in memory <NUM> associated with the emission of light from light emitter <NUM>. Once light is detected at light receiver <NUM>, a second time value is stored in memory <NUM> associated with the receipt of a reflection of the emitted light. Processing circuitry <NUM> may use these stored values in memory <NUM> to calculate a distance based on the time values, e.g., based on the speed of light through air. In this manner, measurement device <NUM> may use light emitter <NUM> and light receiver <NUM> to measure distances from measurement device <NUM> to a position on ballonet surface <NUM> of ballonet <NUM>. This process may be repeated by each measurement device <NUM> in ballonet tracking system <NUM> for each orientation to be measured. These distances may be compiled into a set of distances at a central location in ballonet tracking system <NUM> to allow further processing, e.g., to determine the differences in distances and volume of ballonet. Additionally, each distance measurement may be associated with a particular measurement device <NUM> and/or an orientation and/or position of measurement device <NUM>, e.g., a relative polar and/or azimuthal angle. Accordingly, the measured distances may be correlated to respective values of the predetermined set of distances.

In certain embodiments, measurement device <NUM> is a laser range finder. For example, light emitter <NUM> may be a lasing device emitting a beam of light at a predetermined frequency. Light receiver <NUM> may be a photodetector configured to detect light in a frequency range containing the frequency at which light emitter lases. Using the timing between emission and detection of the laser light, measurement device <NUM> may determine an accurate amount of time it took the laser light to travel to and from ballonet surface <NUM> of ballonet <NUM>. As described above, this may be translated or calculated into a distance from measurement device <NUM> to ballonet <NUM>.

While the example of ballonet tracking system <NUM> having five measurement devices 130a-e was used to describe certain features and embodiments of this disclosure, any number of measurement devices <NUM> may be used to allow ballonet tracking system <NUM> to accurately measure the volume of ballonet <NUM>. For example, ballonet tracking system <NUM> may only include a single measurement device <NUM>. In some embodiments, the orientation of measurement devices <NUM> are not fixed. In this manner, the orientation of measurement devices <NUM> may be changed during measurement to measure additional distances to points on the surface of ballonet surface <NUM> of ballonet <NUM>. While additional variations are described below in reference to <FIG>, other variations are contemplated by this disclosure, including those having different types of measurement devices, different mounting structures to ballonet <NUM>, different mechanisms of coupling measurement devices <NUM> together, or those integrated certain functionality across different portions of ballonet tracking system <NUM> and/or vehicle management system <NUM>.

<FIG> illustrate three variations 400A-C of ballonet tracking system <NUM> that may be used in a ballonet, such as ballonet <NUM>, according to certain embodiments.

<FIG> illustrates a first variation 400A of ballonet tracking system <NUM>. First variation 400A includes a measurement device <NUM>, according to the various embodiments previously described. First variation 400A may include one or more motors <NUM> and one or more mounts <NUM>.

Motors <NUM> and mounts <NUM> may control the orientation of measurement device <NUM> relative to ballonet <NUM>. For example, in certain embodiments, measurement device <NUM> may be mounted, or fastened in any suitable manner, to mount 420a. Mount 420a may be coupled to motor 410a such that as motor 410a rotates, mount 420a also rotates. Accordingly, motor 410a may control the orientation of measurement device <NUM>. As depicted in this example, motor 410a and mount 420a may be controlled to change the polar angle of measurement device <NUM> relative to the fixed portion of ballonet <NUM>.

Similarly, in certain embodiments, motor 410a is mounted to mount 420a, which is coupled to motor 410b. Because mount 420a is coupled to motor 410b, mount 420a may rotate when motor 410b rotates. Accordingly, this may cause motor 410a to rotate, thereby causing a further rotation of mount 420a and measurement device <NUM>. In some embodiments, the rotational axis of motor 410b and motor 410a are orthogonal or at a <NUM>-degree relative angle to each other. For example, in the depicted example, motor 410b and mount 420b may be controlled to change the azimuthal angle of measurement device relative to the fixed portion of ballonet. Accordingly, motors 410a-b and mounts 420a-b may be controlled to vary the azimuthal and polar angles of the orientation of measurement device <NUM>. In this manner, first variation 400A may vary the orientation of measurement device <NUM> over a range of angles.

In certain embodiments, first variation 400A is configured to vary the orientation of measurement device <NUM> over <NUM> degrees around the azimuthal angle and at least <NUM> degrees over the polar angle. For example, if ballonet <NUM> has a shape of approximately a half-sphere, then first variation 400A may controlled to orient measurement device <NUM> towards the entire surface of ballonet surface <NUM> of ballonet. In certain embodiments, first variation 400A is configured to vary the orientation of measurement device <NUM> over <NUM> degrees around the azimuthal angle and less than <NUM> degrees over the polar angle. For example, it may not be necessary to orient measurement device <NUM> across that entire range of angles, e.g., due to the shape of ballonet <NUM> or the measurement requirements to calculate a volume of ballonet <NUM>.

In certain embodiments, the ranges over the azimuthal and polar angles may be varied based on application and/or location of first variation 400A within ballonet 400a. For example, if multiple first variations 400A are disposed within ballonet <NUM>, then it the range of angles may be limited based on the different coverage areas of each of first variations 400A. Similarly, the shape of ballonet <NUM> may also factor over which angles first variation 400A is configured to orient measurement device <NUM>.

First variation 400A may measure a plurality of distances from first variation 400A and one or more locations on ballonet surface <NUM> of ballonet <NUM>. For example, measurement device <NUM> may emit a light signal from first variation 400A and receive a reflection of the light signal from ballonet surface <NUM> of ballonet <NUM>. First variation 400A may then change the orientation of measurement device <NUM>, e.g., by controlling motor 410a and/or 410b to rotate certain amounts. Measurement device <NUM> may repeat the process of emitting light signals and receiving the reflections for a number of orientations along ballonet surface <NUM> of ballonet <NUM>. Accordingly, first variation 400A may measure a plurality of distances from one or more fixed locations and a plurality of locations on ballonet surface <NUM> of ballonet <NUM>.

As described above with respect to ballonet tracking system <NUM>, first variation 400A may use those measured distances to calculate differences between a predetermined set of expected distances and the plurality of measured distances. Based on the calculated differences, first variation 400A may then calculate volume of the ballonet. Thus, first variation 400A may provide an accurate volume of ballonet <NUM>, which may be used to control airship <NUM>.

In certain embodiments, first variation 400A includes housing <NUM> disposed over motors 410a-b, mounts 420a-b, and measurement device <NUM>. Housing <NUM> may protect sensitive components of first variation 400A from inadvertent contact, impact from air currents within ballonet <NUM>, and/or dust or particulates. In some embodiments housing <NUM> may be transparent at least at certain portions of housing <NUM>. For example, housing <NUM> may be completely transparent to the light emitted from measurement device <NUM>, thereby ensuring that the measurements of the distances to ballonet surface <NUM> of ballonet <NUM> are still accurate. Any suitable material may be used to provide housing <NUM>, including plastics, glass, etc..

<FIG> illustrates a second variation 400B of ballonet tracking system <NUM>. Second variation 400B is similar to first variation 400A in that second variation includes motor 410b and mount <NUM> which are controllable to change the azimuthal orientation of measurement device <NUM>.

Second variation 400B differs from first variation 400A at least due to the exclusion of a second mount that rotates in an orthogonal direction to mount <NUM>. In contrast, second variation 400B includes a motor 410a coupled to rack and pinion <NUM>. Measurement device <NUM> is connected to rack and pinion <NUM> by link <NUM>. Link <NUM> may be any suitable coupling, such as a steel string or a hinged rod, that connects a portion of rack and pinion <NUM> to measurement device. Measurement device <NUM> may be mounted to mount <NUM> via hinge <NUM> at the surface of mount <NUM>.

In certain embodiments, motor 410a rotates, causing the portion of rack and pinion <NUM> coupled to measurement device <NUM> via link <NUM> to move vertically. As the portion of rack and pinion <NUM> changes its vertical position, the polar orientation of measurement device <NUM> may change. For example, if the portion of rack and pinion <NUM> is displaced downward toward mount <NUM>, measurement device <NUM> may rotate about hinge <NUM> to have a lower polar-angle orientation relative to rack and pinion <NUM>. Accordingly, motor 410a may be controllable to change the polar orientation of measurement device <NUM>.

In certain embodiments, the combination of motors 410a and 410b can be controllable to change the orientation of measurement device <NUM> over a range of polar and azimuthal angles. In some embodiments, the polar angle may vary from zero to <NUM> degrees and the azimuthal angle may vary from <NUM> to <NUM> degrees. In some embodiments, the polar and azimuthal angles may vary less or more than <NUM> and <NUM> degrees, respectively. Similarly, the range of angles over which measurement device <NUM> is oriented may be based on the application and/or position of second variation 400B within ballonet <NUM>.

Accordingly, second variation 400B may be used to provide distance measurements across a range of orientations, thereby representing a range of points along ballonet surface <NUM> of ballonet <NUM>. As a result, an accurate volume may be calculated for ballonet <NUM>.

In certain embodiments, second variation 400B includes housing <NUM> disposed over motors 410a-b, mount <NUM>, rack and pinion <NUM>, and measurement device <NUM>. Housing <NUM> may protect sensitive components of second variation 400B from inadvertent contact, impact from air currents within ballonet <NUM>, and/or dust or particulates. In some embodiments housing <NUM> may be transparent at least at certain portions of housing <NUM>. For example, housing <NUM> may be completely transparent to the light emitted from measurement device <NUM>, thereby ensuring that the measurements of the distances to ballonet surface <NUM> of ballonet <NUM> are still accurate. Any suitable material may be used to provide housing <NUM>, including plastics, glass, etc..

<FIG> illustrates a third variation 400C of ballonet tracking system <NUM>. In contrast to first variation 400A and second variation 400B, third variation 400C only includes a single motor <NUM> that rotates about a single axis. In certain embodiments, motor <NUM> is oriented to rotate across polar angles, such as motor 410a of <FIG>. In certain embodiments, motor <NUM> is oriented to rotated across azimuthal angles, such as motor 410b of <FIG> and motor 410b of <FIG>.

Instead of including a second degree of movement, third variation 400C includes multiple measurement devices 130a-c mounted to the same mount <NUM> that rotates with motor <NUM>. Each of measurement devices 130a-c is offset by a fixed angle from an adjacent one of measurement devices 130a-c. As depicted in the illustrated example in <FIG>, measurement device 130a is offset by a fixed angle from measurement device 130b and measurement device 130c is offset by a fixed angle from measurement device 130b. These offset angles may be the same or different. In some embodiments, the offset angles are the same and measurement device is oriented having a polar angle of zero relative to the portion of ballonet <NUM> that does not change shape. For example, in a starting position, measurement device 130b may be oriented directly up (assuming a zero pitch of aircraft <NUM>) and each of measurement devices 130a and 130c oriented a fixed angle offset from the vertical.

In certain embodiments, the offset angles are along an axis orthogonal or different from the rotational axis of motor <NUM>. For example, if motor <NUM> rotates mount <NUM> along the polar angles at a fixed azimuthal angle, then the offset angles may be along the polar axis at a fixed azimuthal angle rotated <NUM> degrees relative to the fixed azimuthal angle of mount <NUM>'s rotation. Accordingly, this creates a spread of the orientations of measurement devices 130a-c that allows for the measurement of distances to a variety of locations on ballonet surface <NUM> of ballonet <NUM> at different azimuthal and polar angles.

Third variation 400C may measure a plurality of distances from third variation 400C and one or more locations on ballonet surface <NUM> of ballonet <NUM>. For example, each of measurement devices 130a-c may emit a light signal from third variation 400C and receive a reflection of the light signal from ballonet surface <NUM> of ballonet <NUM>. Third variation 400C may then change the orientation of measurement devices 130a-c, e.g., by controlling motor <NUM> to rotate certain amounts. Measurement devices 130a-c may repeat the process of emitting light signals and receiving the reflections for a number of orientations along ballonet surface <NUM> of ballonet. Accordingly, third variation 400C may measure a plurality of distances from one or more fixed locations and a plurality of locations on ballonet surface <NUM> of ballonet <NUM>.

As described above with respect to ballonet tracking system <NUM>, third variation 400C may use those measured distances to calculate differences between a predetermined set of expected distances and the plurality of measured distances. Based on the calculated differences, third variation 400C may then calculate volume of the ballonet. Thus, third variation 400A may provide an accurate volume of ballonet <NUM>, which may be used to control airship <NUM>.

In certain embodiments, third variation 400C includes housing <NUM> disposed over motor <NUM>, mount <NUM>, and measurement devices 130a-c. Housing <NUM> may protect sensitive components of third variation 400C from inadvertent contact, impact from air currents within ballonet <NUM>, and/or dust or particulates. In some embodiments housing <NUM> may be transparent at least at certain portions of housing <NUM>. For example, housing <NUM> may be completely transparent to the light emitted from measurement device <NUM>, thereby ensuring that the measurements of the distances to ballonet surface <NUM> of ballonet <NUM> are still accurate. Any suitable material may be used to provide housing <NUM>, including plastics, glass, etc..

Similar to ballonet tracking system <NUM> in <FIG>, in certain embodiments, variations 400A-C may be communicatively coupled to vehicle management system <NUM>. In this manner, the measurements performed by variations 400A-C may be used by vehicle management system <NUM> to control airship <NUM>.

In certain embodiments, each of variations 400A-C is disposed at only one location on ballonet surface <NUM> of ballonet <NUM>. For example, instead of the five locations shown in example ballonet tracking system <NUM> depicted in <FIG>, variation 400a may be located at only on location, such as the center of the fixed portion of ballonet surface <NUM>, e.g., where measurement device 130e is located in ballonet <NUM> of <FIG>. In this manner, the arrangement of measurement devices <NUM> may be simplified. Further, as discussed above, because the orientation of measurement devices <NUM> are not fixed in variations 400A-C, multiple distance may be measured from the single fixed location.

<FIG> is a flow chart diagram illustrating an example method <NUM> of calculating the volume of a ballonet in an airship, according to certain embodiments. Method <NUM> may begin at step <NUM>, wherein a plurality of distances between one or more fixed locations and one or more locations on a ballonet surface of a ballonet disposed in an airship are measured. For example, one or more distances may be measured from a plurality of locations fixed to a portion of the ballonet to various points on the ballonet surface of the ballonet, which are subject to deformation or change of position as the volume within the ballonet changes. As another example, one or more distances may be measured from a single location inside the ballonet in a plurality of directions towards the ballonet surface of the ballonet. As yet another example, ballonet measurement system <NUM> may use measurement devices <NUM> to emit and receive reflected light to determine the one or more distances.

At step <NUM>, differences between a predetermined set of expected distances and the plurality of measured distances may be calculated. For example, the measured values may be subtracted from the expected values for a ballonet that is full, e.g., at its highest volume. In some embodiments, this step may include correlating the measured distances with one or a set of distances the predetermined set of expected distances. For example, the correlation may be based on the location and/or orientation of the measurement devices used to obtain the distances. In this manner, the appropriate distances may be compared and used to calculate the differences.

At step <NUM>, a volume of the ballonet is calculated based on the calculated differences. For example, the calculated differences may be further processed to calculated amount of reduction of volume of the ballonet, as compared to the ballonet's full volume. As another example, the calculated differences may be used to determine an approximate three-dimensional shape that corresponds to the approximate shape of the ballonet in its current state. That three-dimensional shape may be used to then calculate the current volume of the ballonet. In certain embodiments, one or more components of ballonet tracking system <NUM> may be used to carry out this step, such as one or more measurement devices <NUM>.

After the volume is obtained, at step <NUM>, the operation of the airship may be controlled using the calculated volume of the ballonet. For example, based on the volume of the ballonet, the flow of air into or out of the ballonet may be controlled. This may control the lift and/or pitch or roll of the airship. As another example, the calculated volume of the ballonet may be used as an intermediary parameter to determine the mass and center of gravity of the air within ballonet, e.g., using measured pressure and temperature values within the ballonet. Using this information, the control of airship may be enhanced by adjusting how the propulsion systems react to commands, e.g., from an operator, to ensure a stable flight.

Accordingly, method <NUM> provides better operation of an airship, such as airship <NUM>, by obtaining an accurate volume of the ballonet. In some embodiments, method <NUM> may be carried out, independently, concurrently, or sequentially, for each ballonet of the airship. The values of volume for each ballonet may be combined for use in controlling the operation of the airship.

Modifications, additions, or omissions may be made to method <NUM> depicted in <FIG>. Any steps may be performed in parallel or in any suitable order. Furthermore, method <NUM> may include more, fewer, or other steps. Additionally, one or more of the steps of method <NUM>, or embodiments thereof, may be performed by any suitable component or combination of components of ballonet tracking system <NUM>, variations 400A-C, and/or vehicle management system <NUM>.

Claim 1:
An airship (<NUM>), comprising:
a ballonet (<NUM>) disposed within the airship (<NUM>), wherein the ballonet (<NUM>) comprises a ballonet surface (<NUM>);
a system (<NUM>), comprising:
one or more light emitters disposed within the ballonet (<NUM>) at one or more fixed locations; and
one or more light detectors disposed within the ballonet (<NUM>) at the one or more fixed locations;
wherein the system (<NUM>) is configured to:
measure a plurality of distances between one or more fixed locations and one or more locations on a surface of the ballonet (<NUM>);
calculate differences between a predetermined set of expected distances and the plurality of measured distances, wherein the predetermined set of expected distances comprise distances from the one or more fixed locations and predetermined locations on the ballonet surface (<NUM>) when the ballonet (<NUM>) is full; and
based on the calculated differences, calculate a volume of the ballonet (<NUM>), wherein the airship (<NUM>) is configured to be operated at least based on the calculated volume of the ballonet (<NUM>); and
a vehicle management system (<NUM>) communicatively coupled to the system (<NUM>), wherein the vehicle management system (<NUM>) is configured to control the operation of the airship (<NUM>) using the calculated volume of the ballonet (<NUM>).