GOVERNMENT RIGHTS

[0001] The subject mater of the present disclosure was made with government support under Government Contract No. 75D30120C09739 awarded by the National Institute for Occupational Safety and Health. The government has certain rights in the subject matter of the present disclosure.

CROSS-REFERENCE TO RELATED APPLICATION

[0002] The present disclosure claims the priority benefit of U.S. Provisional Application Serial No. 63/310,399, entitled “INTRINSICALLY SAFE UNMANNED AERIAL VEHICLES” and filed February 15, 2022, the entire contents of which is incorporated herein.

TECHNICAL FIELD

[0003] The present disclosure is directed to unmanned aerial vehicles (UAV), and more particularly, to UAVs capable of operation in explosive atmospheres or environments.

BACKGROUND

[0004] Existing UAVs are useful tools for remote inspection and surveillance because they are compact, lightweight, and offer superior mobility over other surveillance systems. Being compact and lightweight allows for movement in confined spaces, such as mines or the like. However, traditional UAVs contain components that are not suitable for operation in mines (e.g., underground mines) or other potentially hazardous environments because of the potential for explosion. Further, existing components that would prove to be suitable for use in a mine are large and heavy and would negate the compactness and lightweight characteristics of a UAV. As such, the large and unwieldy components would not be useful in navigating tight spaces in an area such as a mine.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

[0006] FIG. 1 depicts a perspective top view of an illustrative UAV according to one or more embodiments shown and described herein;

[0007] FIG. 2 depicts a perspective bottom view of the UAV of FIG. 1;

[0008] FIG. 3 depicts a top view of the UAV of FIG. 1 ;

[0009] FIG. 4 depicts a first side view of the UAV of FIG 1 having various external components according to one or more embodiments shown and described herein;

[0010] FIG. 5 depicts a bottom side view of the UAV of FIG. 1 having various external components according to one or more embodiments shown and described herein;

[0011] FIG. 6 depicts a cutaway side view along line 6-6 of FIG. 3, depicting the UAV as having interior components therein according to one or more embodiments shown and described herein;

[0012] FIG. 7 schematically depicts a block diagram of illustrative components of a UAV according to one or more embodiments shown and described herein;

[0013] FIG. 8 graphically depicts an inductive analysis of an illustrative brushless DC motor IS potential; and

[0014] FIG. 9 graphically depicts a resistive analysis of an illustrative DC motor IS potential.

DETAILED DESCRIPTION

[0015] The present disclosure generally relates to a UAV system that is suitable (e.g., intrinsically safe) for hazardous environments, allowing the UAV to be used in a hazardous environment where the risk of explosion is high, like a gassy underground mine or the like. In addition, the UAV is constructed of components that are compact and lightweight so that the UAV can navigate through the tight spaces of a mine (e.g., a collapsed mine) or similar location. [0016] A major impediment to design and implementation of a UAV to assist in underground mine rescue operations or for use in other hazardous mining areas is UAV approval by the Mine Safety and Health Administration (MSHA) for use in potentially explosive mine atmospheres.

[0017] In response to a major underground mine emergency, an intrinsically safe (IS) UAV conveys sensors into the mine prior to and/or ahead of entry by rescue personnel to provide timely, accurate, and reliable information upon which a mine rescue team (MRT) can base its decisions and actions. An aerial system approach potentially offers a smaller, faster, more agile, longer range, and more economical means of information collection than ground- based reconnaissance options which may encounter impassible post-event mine conditions. Providing the MRT with the ability to accurately assess conditions well ahead of their current location should permit the MRT to advance under circumstances where poor and/or deteriorating conditions exist, and/or time may be of the essence.

[0018] An IS UAV would also have application to normal underground mining operations as well as operations in other industries where explosive gases or combustible dusts or mists may be present. Such areas are commonly found in oil refineries, chemical plants, petroleum storage areas, flour mills, grain elevators, and paint shops. A UAV constructed to the MSHA design standards could also be approved to support routine operations in nearly any other industry for hazardous confined space investigation and/or evaluation applications.

[0019] Prior investigation and continued monitoring of the industry commercial space has identified a few purpose-designed UAVs that possess some desirable attributes for the mine rescue support mission, such as the UAVs described herein with respect to Appendix A. However, no commercially available or contemplated airframes can address the primary mine rescue mission requirement: intrinsic safety approval to safely operate in the most potentially explosive (Zone 0) atmospheres (for which the power distribution, propulsion, and control systems of commercial UAVs cannot qualify and operate).

[0020] Some IS concerns for a UAV design are (1) protection and isolation of the battery power supply if a short circuit condition occurs and (2) the magnitudes of the voltages and currents associated with the operation of the brushless motors employed by nearly all UAVs. These concerns can be addressed first through detailed design of a small IS UAV (relative to existing UAVs) employing low-power commercial motors and second through introduction of efficient, lightweight means of isolating the battery power required by the low-power motors.

[0021] Other concerns include any IS issues associated with the design and construction of lightweight, low-power commercial communication and sensor technologies identified as candidates for the mine rescue UAV application. Such technologies are available and are constantly evolving. For any specific communication component or sensor, detailed investigations of individual sensor design and construction must be conducted to either demonstrate the absence of any IS issues, implement means to address IS issues, or identify substitutes that are acceptable from an IS perspective.

[0022] Yet other concerns include the potential buildup of static electric charges on any moving UAV components such as its propellers which may be addressed by appropriate selection of propeller base and/or coating materials.

[0023] An illustrative means to achieve energy isolation includes explosion-proof (XP) enclosures that can prevent an internal explosion from escaping the enclosure. Such enclosures are strong enough to initially contain any internal explosion while venting the explosion flame through a path sufficient to cool or quench the flame temperature below ignition levels before reaching outside of the enclosure (For example, US Patent Nos. 4,174,013, US 8,512,430, incorporated herein by reference in their respective entireties). Depending upon the specific environmental conditions of its intended application, additional device protection may be achieved by pressurizing the interior of the enclosure with inert gas (For example, US Patent No. 5,753,986, incorporated herein by reference in its entirety) or filling the enclosure with other materials (e.g., oil, sand) to prohibit the ingress of hazardous materials. Potentially incendiary non-moving components of electrical devices may also be coated with inert compounds (encapsulates) of sufficient thickness and durability to insure that stray energy does not escape.

[0024] Safeguarding means for XP energy isolation may necessitate the addition of protective materials around the device over and above that required for its basic operation. Thus, the designs of these XP devices are generally larger and more massive than comparably capable units intended for operation in non- hazardous locations. For most stationary or fixed equipment installations, the additional size and mass of explosion-proof electrical devices rarely presents a problem. However, for mobile or portable equipment applications, such as a UAV or the like, employing larger, more massive XP enclosures would be inefficient and impractical. That is, the bulkiness of the material may be more than the operating load parameters of the low power components necessary to meet IS specifications so the components are unable to move the UAV as intended. In another example, the components may be too large (e.g., a length, width, or height greater than an acceptable length, width, or height necessary for operating in enclosed spaces, such as, for example, a length, width or height greater than about 50 cm).

[0025] Another illustrative means of designing electrical equipment that can operate suitably in hazardous environments is to limit the electrical energy of that equipment such that any unintended energy release is insufficient to cause an ignition in an environment for which the equipment has been approved for safe operation. Classification systems have been established and accepted (e.g., by various governing bodies and/or organizations) which characterize different hazardous environments based upon the types of potentially explosive materials that may be present and their occurrence levels. For example, one such environment may be one in which the air has a methane content of about 5% or greater. A device or system design that achieves this objective is considered intrinsically safe (IS). The entire power regime of an IS system is controlled. That is, that the energy contained in all its resistive, inductive, and capacitive components, either alone or in combination, under fault conditions cannot generate an unintended energy discharge (e.g., a spark) above a level specified for the particular hazardous environment in which the system is approved for operation. IS equipment may therefore be both more compact and lighter than comparable XP units. However, ignition energy safety thresholds do restrict the available power that an IS device operating in a hazardous location can provide.

[0026] Existing ATEX and EX safety standards classify hazardous areas by gas groups according to their flammability, and zones according to the probability of presence of flammable materials. Among these zones the most hazardous Zone 0 where an explosive gas-air mixture is continuously present or present for long periods. Industry standards and government regulations like ACRI 2001 and Title 30 of the Code of Federal Regulations (CFR) in the United States prescribe requirements for how IS equipment must be designed, constructed, and maintained to insure safe operation. [0027] The primary IS protection method accepted for Zone 0 devices is based on the limitation of power available for creating a spark in the instance of two simultaneous electrical circuit failures (i.e., faults). In case a circuit suffers a break and the circuit becomes open or there is an occasion for an abnormal current diversion, the device design must ensure that the available power for generating a spark between the portions of the open circuit or between any two parts where the current may be diverted is always under the Zone 0 atmosphere’s ignition threshold. The design of an IS device must consider both the physical separation of components along with the maximum possible voltage and current of those components.

[0028] Illustrative examples of environmental characteristics and components that are considered intrinsically safe can be found, for example, in Mine Fires: Prevention, Detection, Fighting Paperback - July 1, 1990, by Donald W. Mitchell, Publisher: Maclean Hunter Pub Co (July 1,1990), ISBN-10: 9990238758, ISBN-13: 978-9990238754, which is incorporated herein by reference.

[0029] Physical separation of conductive parts is mandated to prevent diversion of current and ignition of an explosive atmosphere. Two types of separation are considered for prevention of spark generation: “clearance distance” is the shortest distance between two conductive parts measured through air and “creepage distance” is the shortest distance between two conductive parts measured along the surface of the insulating material separating them. In addition, insulation separation must be evaluated for conductors housed in separate single- or multi-conductor cables along with the possible use of grounded metal or insulating partitions between conductors. Generally, the minimum mandated requirements for separation are based on three factors: location of the circuits, voltage of the circuits, and the material between the conductors.

[0030] If conductors are adequately separated according to the prescribed voltage-based requirements, those conductors are not considered in the two simultaneous electrical circuit fault analysis employed to assess intrinsic safety.

[0031] Electrical motors such as those employed to drive propellers on UAVs incorporate conductive wire coils wound around a ferromagnetic core. Such coils fall in the category of electric circuits with inductive components. Inductive circuit components can store energy that can be released to ignite an explosive atmosphere in the instance of a circuit fault even if the circuit’s power source suddenly shuts off. Therefore, an electrically powered IS device design must also recognize the requirement to maintain stored power at a level less than that required to generate an incendiary spark in the case of accidental opening or diversion of the circuit. The previously mentioned codes and regulations offer voltage versus current limit curves that correspond to safe energy limits. The ignition limits depend on the type of explosive environment (incendiary powder, liquid, or gas and temperature), in which the device is intended and, ultimately, approved to operate.

[0032] Traditional electrical device designs were initially developed to function in non- hazardous locations. Those designs have evolved as new component materials have become available and more elaborate power control schemes have been developed. The result is that electrical device designs, still intended for non-hazardous locations, have become more powerful, responsive, and energy efficient than their predecessors. One such example are the electrical motors now employed to drive propellers on small unmanned aerial vehicles. However, while the means to enable electrical devices to function safely in hazardous locations may also have been refined over time, they have not changed fundamentally. Therefore, the latest, most efficient XP devices still remain more massive than their standard design counterparts, and current IS devices must still function within known energy restrictions which limit the power and the power density that they can deliver. The increased mass and power restrictions generally preclude the use of current XP and IS devices in many applications where a light weight or an equivalent high energy density is required, as in the example above using small unmanned aerial vehicles.

[0033] The present disclosure relates to a practical approach to the design of an IS UAV capable of safe operation in atmospheres having the greatest potential for explosion. The present disclosure describes the design of an IS UAV specifically engineered for and capable of safe operation in all explosive atmosphere zones such as those that may be encountered in gassy underground mines or ATEX or EX classified facilities.

[0034] Given the foregoing, as used herein, the term “intrinsically safe” or “IS” refers to any component, device, material used, system, or combination thereof that limit energy (both electrical energy and thermal energy) that is available for ignition, particularly in environments where the risk of explosion due to unsafe gases, particulate matter, or the like are present (e.g., Zone 0 environments as described herein). That is, the components, devices, materials used, systems, or combinations thereof as described herein generally encompass equipment and wiring that is incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of specific hazardous atmospheric mixtures in a most easily ignited concentration. “Intrinsically safe” as used herein specifically excludes high-power circuits and/or components that utilize the same (e.g., certain electric motors and/or lighting). Components, devices, materials, systems, or combinations thereof used herein as “intrinsically safe” or “IS” may be such components, devices, materials, systems, or combinations thereof that are denoted with an “i” as part of ATEX and/or lECEx explosion classifications; components, devices, materials, systems, or combinations thereof that have been designated explosion proof per NEC 500; flameproof enclosures (designated “d” in IEC, ATEX, and NCE 505); components, devices, materials, systems, or combinations thereof that are designated increased safety ("e"), encapsulation ("m"), enclosed-break device ("nC"), sealed device ("nC"), hermetically-sealed device ("nC"), restricted-breathing enclosure ("nR"), oil immersion ("o"), protection of optical radiation ("op"), venting ("p"), powder or sand filling ("q"), special protection ("s") and dust ignition protection by enclosure ("t"). “Intrinsically safe” or “IS” as used herein may also include designated or non-designated components, devices, materials, systems, or combinations thereof that limit electric current by using series resistors (e.g., using types of resistors that always fail open); and limit the voltage with a plurality of zener diodes. With zener diodes, dangerous incoming potentials are grounded, with galvanic isolation barriers there is no direct connection between the safe- and hazardous- are a circuits by interposing a layer of insulation between the two. Certification standards for intrinsic safety designs (e.g., IEC 60079-11 but since 2015 also IEC TS 60079-39) generally specify that the barrier does not exceed approved levels of voltage and current with specified damage to limiting components. Further, “Intrinsically Safe” or “IS” as used herein also refers to components, devices, materials, systems, or combinations thereof that are usable in a hazardous area and designed to operate with low voltage and current, without any large capacitors or inductors that could discharge in a spark. The components, devices, materials, systems, or combinations thereof are further connected, using approved wiring methods, back to a control panel in a non-hazardous area that contains safety barriers (e.g., a body, housing, storage cavity, or the like that defines an intrinsically safe interior environment. The safety barriers ensure that, during normal operation, and with the application of faults according to the Equipment Protection Level, EPL, also if accidental contact occurs between the instrument circuit and other power sources, no more than a predetermined approved voltage and current enters the hazardous area. [0035] In some embodiments, a UAV is provided with one or more low-impedance motors powered by a single cell or battery having a plurality of cells. The motors drive propellers constructed so that they do not accumulate static electric charge. The maximum current and voltage demands of each motor remain below established IS limits. The operation of the motors is controlled remotely by low-power radio signals which provide instructions to flight stability and motor speed controller circuits on the UAV specifically designed to adhere to all IS electrical design and construction requirements. Furthermore, the single cell or battery power supply is mechanically protected from damage by exterior forces while its output is protected electrically by current limiting circuits so that a short circuit failure in the UAV electronics cannot release energy exceeding that required to ignite an explosive atmosphere. Additionally, all of the UAV radio control and data transmission components, payload sensors, and their interfaces are designed, constructed, and protected to operate below the established IS power limits. Thus, the entire design, construction, and operation of the present disclosure is capable of operation in an explosive environment.

[0036] As will be described herein, one or more components of the UAVs encompassed by the present disclosure are IS components. That is, the various components described herein may be rated as intrinsically safe as described herein. In some embodiments, an IS UAV may be constructed of electrically powered components and power supplies that are each rated as IS components. In other embodiments, an IS UAV may be constructed of body materials that are IS rated such that the interiors defined by the bodies are an intrinsically safe environment. In still further embodiments, an IS UAV may be constructed of body materials, electrically powered components, and power supplies that are all rated as IS components. Specific examples of the various IS UAVs of the present disclosure will now be described.

[0037] Referring now to the figures, FIGS. 1-6 depict various views of an illustrative UAV 100 according to an embodiment. While the present disclosure relates specifically to an unmanned vehicle, the present disclosure is not limited to such. That is, the systems described herein may be, for example, a remotely piloted vehicle (RPV), an unmanned aircraft system (UAS), or the like. The UAV 100 is generally constructed of components that make the UAV an intrinsically safe system, as described herein. The UAV 100 includes a containment apparatus 101 that has a body 102 defining at least one component storage cavity 110. In some embodiments, the body 102 may also define at least one power supply containment cavity 116 (FIG. 2) and/or at least one mobility component 120 (shown as 120a, 120b, 120c, 120d). In other embodiments, the at least one power supply containment cavity 116 (FIG. 2) and/or the at least one mobility component 120 may be components that are separate from the body 102. In some embodiments, the at least one component storage cavity 110 may be a central cavity around which the power supply containment cavity 116 (FIGS. 2 and 6) and/or the at least one mobility component 120 are coupled. However, other arrangements and configurations of components (including additional or fewer components) are contemplated and included within the scope of the present application.

[0038] The at least one component storage cavity 110 may generally be a cavity that contains various components of the UAV 100 therein, as described hereinbelow with respect to FIG. 6. Still referring generally to FIGS. 1-6, the containment apparatus 101 includes one or more walls that form the body 102 (including the component storage cavity 110, the at least one power supply containment cavity 116, and/or the at least one mobility component 120). For example, the component storage cavity 110 may have at least an upper wall 112 and a lower wall 114 that enclose the contents of the component storage cavity 110. That is the upper wall 112 and the lower wall 114 define an interior cavity for containing components, as described in greater detail herein. The upper wall 112 and/or the lower wall 114 may be constructed of materials that protect the contents of the component storage cavity 110, particularly materials that exhibit shock absorption characteristics, materials that are lightweight, and/or materials that are less susceptible to damage, such as cracking or the like. In some embodiments, the materials of the component storage cavity 110 may be rated as IS materials. One illustrative example of such materials includes carbon fiber. It should be appreciated that while the present disclosure only discusses the upper wall 112 and the lower wall 114, the body 102 may define additional walls of the at least one component storage cavity 110 in other embodiments.

[0039] Still referring generally to FIGS. 1-6, the body 102 is generally dimensioned such that the overall size of the UAV 100 is compact and lightweight enough to maneuver in tight spaces (e.g., in mine environments) and so that low power components can be used. That is, as depicted in FIG. 1, the body 102 may have a length 1, width w, and/or height h that is sufficiently small enough to maintain a compact overall size of the UAV 100. For example, the length 1 may be between about 10 centimeters (cm) and about 100 cm, including, but not limited to, less than about 20 cm, less than about 30 cm, less than about 40 cm, less than about 50 cm, less than about 60 cm, less than about 70 cm, less than about 80 cm, less than about 90 cm, less than about 100 cm, or any value or range between any two of the foregoing values (including endpoints). In another example, the width w may be between about 10 cm and about 100 cm, including, but not limited to, less than about 20 cm, less than about 30 cm, less than about 40 cm, less than about 50 cm, less than about 60 cm, less than about 70 cm, less than about 80 cm, less than about 90 cm, less than about 100 cm, or any value or range between any two of the foregoing values (including endpoints). In yet another example, the height h may be between about 1 cm and about 100 cm, including, but not limited to, less than about 5 cm, less than about 10 cm, less than about 20 cm, less than about 30 cm, less than about 40 cm, less than about 50 cm, less than about 60 cm, less than about 70 cm, less than about 80 cm, less than about 90 cm, less than about 100 cm, or any value or range between any two of the foregoing values (including endpoints). In some embodiments, the length 1 and the width w may be substantially equal.

[0040] Referring to FIG. 6, the at least one power supply containment cavity 116 is generally shaped, sized, and configured to contain a power supply 160 therein, such a battery or the like. In some embodiments, the power supply containment cavity 116 may fully enclose the power supply 160. That is, the power supply 160, particularly in embodiments where a battery is used, may be completely contained so that in the event of failure, any short, spark, or the like at the battery occurs within the power supply containment cavity 116 to avoid or minimize an external explosion or the like. In such an embodiment, the power supply 160 may include one or more wireless charging components (e.g., one or more charging pads using the Qi® standard, another inductive charging standard, or the like) that allow for charging and/or discharge of energy to/from the battery wirelessly. In other embodiments, the power supply containment cavity 116 may partially enclose the power supply 160. That is, the power supply containment cavity 116 may be at least partially open to the component storage cavity 110 such that wires, conduit, or the like extends between the power supply containment cavity 116 and the component storage cavity 110 for the purposes of transmitting electrical power and/or data between the power supply 160 and/or one or more components of the UAV 100 as described in greater detail herein. In some embodiments, the power supply containment cavity 116 may be omitted or integrated with the component storage cavity 110 such that the power supply 160 is at least partially contained within the component storage cavity 110. In still other embodiments, the power supply 160 and/or the components to which it is connected may be intrinsically safe components so no XP enclosure is necessary, thereby minimizing the need for weighty components.

[0041] The power supply 160 can generally be any batery, capacitor, and/or the like to provide electrical power to the UAV 100, particularly the various components thereof. The power supply 160 includes a single cell or a plurality of cells sufficient to power the UAV 100. In some embodiments, the power supply 160 may be constructed such that an output component thereof (e.g., wires, ports, radios, and/or the like) is protected electrically by current limiting circuits so that a short circuit failure is unlikely or does not release energy exceeding that required to ignite an explosive atmosphere, as described herein.

[0042] Referring to FIGS. 1-3, the mobility components 120a-120d are depicted as air propulsion components. However, it should be appreciated that this is a non-limiting example and other components that allow for flight may also be used. The mobility components 120a-120d each include a frame 128a-128d, one or more motors 126a-126d, one or more electronic speed control devices (not shown), one or more propellers 124a-124d, and/or one or more support arms 122a-122d.

[0043] The frame 128a-128d and/or the one or more support arms 122a-122d may generally support the one or more motors 126a-126d, and/or the one or more propellers 124a- 124d. The frame 128a-128d and/or the one or more support arms 122a-122d may also be constructed to surround one or more other components to protect certain components (e.g., the propellers 124a-124d and/or the motors 126a-126d) from becoming damaged in the event of a crash or other impact. In some embodiments, the frame 128a-128d may at least partially surround various components (e.g., the one or more propellers 124a-124d). In more specific embodiments, the frame 128a-128d may be an enclosure that surrounds components such as the respective propellers 124a-124d to protect the propellers 124a-124d from contacting debris or the like, while at the same time allowing for air passage therethrough so that flight can be achieved (e.g., a cage like surround or the like).

[0044] The one or more motors 126a-126d may be electrically powered components that drive rotational movement of the one or more propellers 124a-124d around a respective axis Al, A2, A3, A4 (FIG. 1), which, when rotated, provide the necessary lift to cause the UAV 100 to fly in any direction, hover, and/or the like. It should be appreciated that adjusting the speed and/or rotation of each of the one or more propellers 124a-124d (e.g., via the corresponding motors 126a-126d) causes various movements of the UAV 100, such as up, down, roll, pitch, yaw) such that the UAV 100 can be navigated through a space such as a mine. In some embodiments, the UAV 100 may be quadcopter having 4 rotors. However, it should be understood that any rotorcraft, regardless of the number of rotors, may be used without departing from the scope of the present disclosure. Thus, the UAV 100 may include 1, 2, 3, 4, 5, 6, 7, 8, or more rotors. In some embodiments, the one or more motors 126a- 126d may be electric motors. In some embodiments, the motors 126a-126d possess an electrical impedance such that, at a maximum operating current and voltage level of a particular motor 126a-126d, the individual stored energy remains below a regulatory established IS limit to generate an incendiary spark.

[0045] In some embodiments, each of the one or more motors 126a-126d may be any one of a class of low inductance brushless motors. One means to initially evaluate candidate motors is to compare their electrical power requirements and energy storage potentials to limits that the MSHA has established as IS thresholds. Measurement of brushless motor inductance and knowledge of the maximum operating currents necessary to keep any stored energy in the motor from exceeding established explosive limits would serve to identify candidate motors for IS UAV design consideration. Note that more rigorous analysis of likely motor IS performance in a complete UAV design would be required prior to actual motor selection. MSHA has provided three Excel files as basic IS screening tools to compare the resistive, inductive, and capacitive energy storage of operating electrical circuits or components relative to a 0.3 millijoule (mJ) minimum ignition energy for a methane-air mixture. These screening tools can be applied to identify brushless motors that, under certain circumstances, could closely approach or operate within IS electrical limits. The screening analysis process then becomes one that identifies any motors (or class of motors) that, for a reasonable available battery voltage, have maximum recommended operating currents that define points that still fall below or close to the methane ignition energy curves of the MSHA tools. For motors with multiple wire windings, the critical tool may be that which evaluates energy storage as a function of component induction and applied current. If motor physical parameters can be accurately characterized, application of the MSHA methane ignition energy curves can be used in an initial motor screening process recognizing their limitations. As an example, each of the one or more motors 126a- 126d may be a Scorpion 2208 (Scorpion Power System Limited, Hong Kong), wound for a constant velocity (Kv) of 1900 revolutions per minute (rpm) that the motor turns when 1 volt (V) is applied with no load atached to the motor, and has an inductance of 12.8p.I I (microhenry). Inserting this inductance value into the appropriate MSHA tool and increasing the amperage until reaching the ignition curve, as indicated in FIG. 8, suggests that limiting motor current to a maximum of 6.8 A (amp) might allow the Scorpion 2208 to be considered a viable IS UAV motor candidate. This value of current at the specified inductance is shown on the minimum ignition curve. Note however that MSHA will most likely apply a safety factor to the current to obtain a 1.5 factor on energy. Therefore, the maximum allowable operating current (before applying a safety factor) would be about 5.55 A. Assuming a 12V DC power supply for the motor operating at maximum of 6.8A, the resistive circuit analysis of FIG. 9 also suggests the Scorpion 2208 might be a viable candidate. Once again, MSHA would likely apply safety factors to the voltage and current. The actual circuit voltage and current would be increased by A/1.5. AS noted above, the pre-safety factor current would be 5.55A and the pre-safety factor voltage would be 9.8V. If 12V and 6.8 A are the actual circuit values, then MSHA would increase the voltage to 14.7V and the current to 8.3 A. Extrapolating, the calculated point now appears to fall much closer to the curve, but would likely pass a sparkignition test. For motors, MSHA’s Approval and Certification Center (A&CC) will measure the inductance to verify an applicant’s specification. MSHA measures inductance using either a Sencore LC103 or an Agilent E4990 impedance analyzer. This discussion emphasizes inductance as an important factor A&CC might consider in assessing the IS potential of any specific brushless motor. However, A&CC may also choose to conduct spark-ignition testing of the motors in series or parallel, dependent on a circuit fault analysis.

[0046] Referring again to FIGS. 1-3, in some embodiments, the one or more propellers 124a-124d are constructed so that they do not accumulate static electric charge, particularly during movement thereof. As such, the one or more propellers 124a-124d may be constructed of materials that are less likely to accumulate static electric energy and/or are constructed so that the propellers 124a-124d, as a result of operation in the specific atmospheres described herein (e.g., underground mines), do not build up a static charge from rotating in the atmosphere. As an added benefit, the materials used for the propellers 124a- 124d may not generate static discharge in the unlikely event that the propellers 124a-124d rub against other components such as the corresponding frames 128a-128d (e.g., if damage is sustained during operation). While the propellers 124a-124d are depicted as being three blade propellers, the present disclosure is not limited to such. That is greater than or fewer than three blades may be used in other embodiments. In some embodiments, additional components such as vanes (e.g., inlet/outlet guide vanes), fan blades, and/or the like may be utilized.

[0047] Referring again to FIGS. 1-7, the UAV 100 further includes at least one additional electrically powered component, including, but not limited to, remote radio control system components, flight control electronic circuits, data collection sensors, data transmission system components and/or the like. Data collection sensors as used herein may generally be any component that is capable of sensing an environment and capturing data pertaining to the environment. Illustrative examples of data collection sensors include, but are not limited to, an imaging device, an obstacle detection and avoidance sensor, an atmospheric gas detection and measurement sensor, or the like. For example, the UAV 100 may include one or more IR sensors 132a, 132b, 142a, 142b, 142c, one or more gas sensors 134, one or more illumination light emitting devices (LED) 146, one or more navigational LEDs 148, one or more imaging devices (e.g., a low lux camera 144 capable of capturing one or more wavelengths of visible light, an IR camera 130 capable of capturing one or more wavelengths of IR radiation, and/or the like), a video transmission antenna 138, an R/C receiver antenna 136, and/or the like. The one or more illumination LEDs 146 may provide white light illumination for the low lux camera 144. The one or more navigational LEDs 148 may provide navigation lights (e.g., red, green, blue) to assist in operator visual control. The various components may be interconnected via a plurality of power distribution conduits 140 (e.g., wires, cables, and/or the like) that are shielded and/or embedded within components in order to meet standards necessary so that the UAV 100 is intrinsically safe, as described herein. For example, the plurality of power distribution conduits 140 may include first and second power distribution conduits that are physically separated from one another in a manner that is in accordance with various established regulations to ensure the power distribution conduits 140 are intrinsically safe. An obstacle detection and avoidance sensor may be, for example, an infrared transmitter (e.g., LEDs 146, 148), an infrared receiver (e.g., the one or more IR sensors 132a, 132b, 142a, 142b, 142c and/or IR camera 130), and a potentiometer (not depicted). According to the reflecting character of an object, if there is no obstacle, the emitted infrared ray will weaken with the distance it spreads and finally disappears. If there is an obstacle encountered by the infrared rays, the rays will be reflected back to the infrared receiver. Then the receiver detects the signal and confirms an obstacle in front. An atmospheric gas and measurement sensor (e.g., gas sensor 134) is generally a sensor that obtains samples of fluid (e.g., gas) in the atmosphere surrounding the UAV and determines various concentrations of elements within the fluid. An illustrative example is the various sensors available from Seeed Technology Co., Ltd. (Shenzhen, CN). Additional details regarding these various components is described in Appendix A.

[0048] As depicted in FIG. 7, the UAV 100 also includes an electronic speed controller 162, a video transmitting and/or processing device 164, and an integrated fight controller 172 contained within the component storage cavity 110. The electronic speed controller 162, the video transmitting and/or processing device 164, and/or the integrated fight controller 172 may each may be electrically and/or communicatively coupled to one another and/or to one or more components described herein via one or more transmission lines 170, such as wires, fiber optic cables, and/or the like. In some embodiments, various components may be communicatively and/or electrically coupled via wireless means, using one or more wireless transmitters. FIG. 7 schematically depicts an illustrative interconnection of components described herein, where the lines between components represent communications and/or electrical connections). The electronic speed controller 162 is generally an electronic circuit or the like that controls and regulates the speed of an electric motor (e.g., one or more of the motors 126a-126d). The electronic speed controller 162 may also provide reversing of the motors 126a-126d and dynamic braking. The video transmitting and/or processing device 164 is generally an electronic circuit or the like that receives signals from the various sensors (e.g., the low lux camera 144, the IR camera 130, or the like) and processes the signals so the signals can be interpreted for the purposes of providing images/video to a user at a remote station and/or for the purposes of autonomous movement of the UAV 100 (e.g., to avoid obstacles and plan movement). The integrated flight controller 172 is generally an electronic circuit, computer, or the like for controlling movement of the UAV 100, either autonomously or via instructions received from a remote controller. The integrated flight controller 172 may be known as a flight controller (FC), a flight controller board (FCB), or autopilot. In some embodiments, the integrated flight controller 172 may incorporate a primary microprocessor, a secondary or failsafe processor, and sensors such as accelerometers, gyroscopes, magnetometers, and barometers into a single module. As previously described herein, each of the components depicted in FIG. 7, including, but not limited to the electronic speed controller 162, the video transmitting and/or processing device 164, and the integrated fight controller 172, may be constructed according to predetermined specifications such that the components are IS components. Specific examples of certain components depicted in FIG. 7, such as, for example, the electronic speed controller 162, the video transmitting and/or processing device 164, and the integrated fight controller 172 are described in greater detail with respect to Appendix A.

[0049] In some embodiments, the UAV 100 described herein may be formed according to a particular method. For example, the method may include the steps of providing the various cavities described herein, assembling the various electrically powered components within the cavities, electrically coupling the electrically powered components to a power supply, placing the power supply within a cavity (e.g., the power supply containment cavity 116), and enclosing the various cavities to form the UAV.

Appendix A - Illustrative examples of components included within UAV 100

Table 1 : List of COTS components incorporated in the current IS UA V design and drawings

Table 2: List of potential alternative COTS components

Appendix B - Information pertaining to other UAVs claiming IS approvals

[0050] The acronym “ATEX” is a set of European Union regulations that ensure products used in explosive environments are safe. ATEX is short for ‘'Atmospheres Explosibles”.

ATEX directives define safety standards that apply to different levels of working environments. The more dangerous the environment, the more stringent the requirements.

For example, ATEX Zone 0 is one of the two most dangerous zoning classifications, 'fable 3 shows the European zone classifications and how the zones are defined. The table also shows how the North American classification of zones maps into the European classifications.

Table 3: ATEX and North American zone classifications [0051] A survey completed in 2018 of UAVs (a.k.a. “drones”) reported below revealed only four (4) vehicles that claimed to be designed and constructed for use in potentially hazardous conditions. Table 4 lists these and summarizes their basic attributes. The paragraphs following Table 4 elaborate upon each of those drones and their potential suitability for underground application.

[0052] Subsequent active monitoring for new innovations in the UAV market space since 2018 has observed significant advances in both UAV designs and capabilities to enable effective operation in GPS-denied confined spaces. However, monitoring of that same market space has not revealed either any advancement of the vehicles listed in Table 4 or any new commercial makes or models that claim to have any level of IS approval.

2018 Market Survey Investigation Report

Table 4: UAVs Designed for Use in Hazardous Atmospheres

[0053] The Larson Electronics EXDR-LE10-CMR-R1 is by far the largest and heaviest of the four drones described herein. This should be anticipated since it was designed not only for open-air industrial site inspection and assessment but also for material delivery. It is reported to be certified for service in Class 1 Division 1 (a.k.a. “Zone 1”) areas defined as those “where ignitable concentrations of flammable gases, vapors, or liquids are either likely to exist under normal operating conditions or exist frequently because of maintenance/repair work or frequent equipment failure”.

[0054] The Larson drone is much too large for effective use in most underground environments and has a maximum flight duration only slightly greater than the threshold requirement for the mine rescue UAV. Its cost is also prohibitive. [0055] The Parrot Bebop 2 C1D2 apparently was intended to be a hardened version of the popular Bebop 2 model that the French company Parrot has developed and successfully marketed in several variants over the past three years as an economical hobbyist or sport UAV. Parrot has expanding the application of the Bebop 2 design into commercial markets with the introduction in late 2017 of the Bebop 2 Thermal model that carries both visible and infrared cameras. The Thermal UAV is intended for use in building inspection and civil (fire, police) support applications such as search and rescue.

[0056] The C1D2 (presumed to stand for Class 1, Division 2 operation) version for industrial inspection in “hazardous areas” was advertised on a third-party website. The C1D2 appeared attractive as the basis for a potential Task 3 project demonstration unit not only because it was designed to achieve some level of safety certification but because of its compact size, proven and tested basic design, and relatively low cost (originally advertised at $3,500). The C1D2 was neither designed nor marketed by Parrot; apparently, an “aftermarket” developer intended to make modifications to the Parrot product and sell the modified units.

[0057] The San Jorge Tecnologicas ATEX DRONE was another small UAV specifically intended for use in enclosed spaces classified as Zone 0 where a continuous or nearly continuous explosive atmosphere may be present (see Table 3). What makes the ATEX DRONE unique is that it employs motors that are pneumatically powered (instead of electrically powered) thus eliminating a major design concern related to a potential ignition source.

[0058] The drone's pneumatic flight motors are powered through an umbilical tether connected to an air compressor maintained in fresh air. The umbilical also serves as a means of communication with the drone through fiber optic cable. The power (lift) of the current pneumatic motor/propeller combination has been tested and measured. Four (4) motors have been installed on a COTS quad-copter platform about 20 inches in width for limited flight control and stability testing. San Jorge's initial concept is to use and support a tether ~30 meters (-100 feet) in length, sufficient for inspection of the interior of oil storage tanks and similar confined spaces. Additional payload capacity is anticipated to be about 100-200 grams, about the mass of a video camera and its LED illuminator. [0059] The major drawbacks of this design for underground applications are associated with the umbilical tether that would both severely limit the exploration range of the UAV and undoubtedly become tangled or caught on objects within the mine.

[0060] Xamen Technologies of France claims that their LE4-8X Dual as “the first ever UAV compliant with explosive atmosphere operations to investigate areas where there is a risk of explosion due to the presence of gas and/or vapor”. This UAV is also a dual quadcopter design slightly smaller than the Larson UAV. The LE4-8X Dual is approved for use in Zone 2 areas as defined in Table 3 as having an “infrequent presence of explosive atmosphere”. It is intended for outdoor inspection and assessment of chemical and petroleum processing plants. One notable design feature of this drone is its use of wooden propellers to eliminate the possibility of static build-up and discharge. This drone is also quite large for effective use in most underground environments, claims a maximum flight duration only 15 minutes.

[0061] In summary, of the four identified “hazardous atmosphere” UAVs, the two commercially available models are both much too large and do not offer the necessary level of safety certification for unrestricted use in an underground coal mine. The smaller Parrot and San Jorge models profess to have acceptable physical dimensions for underground application. Unfortunately, neither is currently offered as a commercial product and neither has a documented IS rating. The pneumatic tether required by the San Jorge model limits both its range and maneuverability. The actual development status of the Parrot UAV remains unknown.

[0062] Further aspects are provided by the subject matter of the following clauses:

[0063] An intrinsically safe unmanned aerial vehicle (UAV), comprising: a body defining at least one component storage cavity containing at least one electrically powered component; and a power supply containment cavity containing a power supply that is electrically coupled to the at least one electrically powered component, wherein the at least one component storage cavity and/or the power supply containment cavity defines an intrinsically safe interior environment.

[0064] The intrinsically safe UAV of any preceding clause, further comprising the at least one electrically powered component. [0065] The intrinsically safe UAV of any preceding clause, wherein each of the at least one electrically powered component is selected from a group comprising a motor, a propeller, a remote radio control system component, a flight control electronic circuit, a data collection sensor, and a data transmission system component.

[0066] The intrinsically safe UAV of any preceding clause, wherein the data collection sensor comprises an imaging device.

[0067] The intrinsically safe UAV of any preceding clause, wherein the imaging device is configured to image one or more wavelengths of visible light.

[0068] The intrinsically safe UAV of any preceding clause, wherein the imaging device is configured to image one or more wavelengths of infrared radiation.

[0069] The intrinsically safe UAV of any preceding clause, wherein the data collection sensor comprises an obstacle detection and avoidance sensor.

[0070] The intrinsically safe UAV of any preceding clause, wherein the data collection sensor comprises an atmospheric gas detection and measurement sensor.

[0071] The intrinsically safe UAV of any preceding clause, wherein the at least one electrically powered component comprises at least one remote radio control system component designed, constructed, and protected to operate below a threshold intrinsically safe power limit.

[0072] The intrinsically safe UAV of any preceding clause, wherein the at least one electrically powered component comprises at least one flight control electronic circuit formed in accordance with an intrinsically safe electrical design and construction requirement.

[0073] The intrinsically safe UAV of any preceding clause, wherein the at least one electrically powered component comprises at least one data collection sensor designed, constructed, and protected to operate below a threshold intrinsically safe power limit.

[0074] The intrinsically safe UAV of any preceding clause, wherein the at least one electrically powered component comprises at least one data transmission system components designed, constructed, and protected to operate below a threshold intrinsically safe power limit. [0075] The intrinsically safe UAV of any preceding clause, wherein the at least one electrically powered component comprises an electric motor that, when operating at a maximum operating current and voltage level, has an impedance and a stored energy that is below a predetermined intrinsically safe limit to generate an incendiary spark.

[0076] The intrinsically safe UAV of any preceding clause, wherein the at least one electrically powered component comprises a propeller constructed from a material that does not accumulate a static electric charge.

[0077] The intrinsically safe UAV of any preceding clause, further comprising a plurality of power distribution conduits electrically coupling the at least one electrically powered component to the power supply, wherein a first one of the plurality of power distribution conduits is physically separated from a second one of the plurality of power distribution conduits.

[0078] The intrinsically safe UAV of any preceding clause, wherein the power supply comprises a single cell or a plurality of cells sufficient to power the at least one electrically powered component and, wherein an output of the power supply is electrically protected via one or more current limiting circuits such that a short circuit failure releases an amount of energy below a threshold necessary to ignite an explosive atmosphere.

[0079] The intrinsically safe UAV of any preceding clause, wherein the body has a length, a width, and a height having a maximum dimension of about 50 centimeters (cm).

[0080] A system comprising the intrinsically safe UAV of any preceding clause.

[0081] A containment apparatus for an intrinsically safe UAV, the containment apparatus comprising: one or more walls forming a body that defines an interior cavity, wherein the interior cavity is an intrinsically safe interior environment for at least one electrically powered component contained within the interior cavity.

[0082] The containment apparatus of any preceding clause, wherein the interior cavity comprises at least one component storage cavity and/or a power supply containment cavity.

[0083] The containment apparatus of any preceding clause, wherein the body has a length, a width, and a height, each of the length, the width, and the height having a maximum dimension of about 50 centimeters (cm). [0084] The containment apparatus of any preceding clause, wherein the body is rated for European Zone 0 (gases), European Zone 20 (dusts), North American Class I Division 1 (gases), or North American Class II Division 1 (dusts).

[0085] An intrinsically safe UAV, comprising: a body defining an interior cavity; and at least one electrically powered component disposed within the interior cavity of the body, wherein the at least one electrically powered component is designed, constructed, and protected to operate below a threshold intrinsically safe power limit.

[0086] The intrinsically safe UAV of any preceding clause, wherein each of the at least one electrically powered component is selected from a group comprising a motor, a propeller, a remote radio control system component, a flight control electronic circuit, a data collection sensor, and a data transmission system component.

[0087] The intrinsically safe UAV of any preceding clause, wherein the data collection sensor comprises an imaging device.

[0088] The intrinsically safe UAV of any preceding clause, wherein the imaging device is configured to image one or more wavelengths of visible light.

[0089] The intrinsically safe UAV of any preceding clause, wherein the imaging device is configured to image one or more wavelengths of infrared radiation.

[0090] The intrinsically safe UAV of any preceding clause, wherein the data collection sensor comprises an obstacle detection and avoidance sensor.

[0091] The intrinsically safe UAV of any preceding clause, wherein the data collection sensor comprises an atmospheric gas detection and measurement sensor.

[0092] The intrinsically safe UAV of any preceding clause, further comprising at least one flight control electronic circuit formed in accordance with an intrinsically safe electrical design and construction requirement.

[0093] The intrinsically safe UAV of any preceding clause, wherein the at least one electrically powered component comprises an electric motor that, when operating at a maximum operating current and voltage level, has an impedance and a stored energy that is below a predetermined intrinsically safe limit to generate an incendiary spark. [0094] The intrinsically safe UAV of any preceding clause, wherein the at least one electrically powered component comprises a propeller constructed from a material that does not accumulate a static electric charge.

[0095] The intrinsically safe UAV of any preceding clause, further comprising: a power supply; and a plurality of power distribution conduits electrically coupling the at least one electrically powered component to the power supply, wherein a first one of the plurality of power distribution conduits is physically separated from a second one of the plurality of power distribution conduits.

[0096] The intrinsically safe UAV of any preceding clause, wherein the power supply comprises a single cell or a plurality of cells sufficient to power the at least one electrically powered component and, wherein an output of the power supply is electrically protected via one or more current limiting circuits such that a short circuit failure releases an amount of energy below a threshold necessary to ignite an explosive atmosphere.

[0097] The intrinsically safe UAV of any preceding clause, wherein the body has a length, a width, and a height having a maximum dimension of about 50 centimeters (cm).

[0098] A method of forming an intrinsically safe unmanned aerial vehicle (UAV), the method comprising: assembling one or more electrically powered components within a component storage cavity; electrically coupling the one or more electrically powered components to a power supply; placing the power supply within a power supply containment cavity; and enclosing the component storage cavity and the power supply containment cavity to form the intrinsically safe UAV.

[0099] The method of any preceding clause, wherein assembling the one or more electrically powered components comprises assembling one or more of a motor, a propeller, a remote radio control system component, a flight control electronic circuit, a data collection sensor, and a data transmission system component.

[00100] The method of any preceding clause, wherein electrically coupling the one or more electrically powered components to the power supply comprises coupling a plurality of power distribution conduits between the one or more electrically powered components and the power supply such that a first one of the plurality of power distribution conduits is physically separated from a second one of the plurality of power distribution conduits.