Description:A TETHERED MULTI-ROTOR ELECTRIC AIR VEHICLE

Field of the Invention
The present invention relates to tethered electric aerial vehicles and, more particularly, to a tethered multi-rotor electric aircraft employing tethered high-voltage electric power with onboard power management during airborne operation.

Background of the Invention
Tethered air vehicles commonly employ high-voltage power transmission through a tether to reduce electrical transmission losses. In existing tethered aircraft architectures, however, the voltage level of the tether-supplied power is constrained by the maximum operating voltage of onboard electrical systems. This constraint is primarily dictated by the input voltage limitations of power conversion hardware integrated into the aircraft. Consequently, the voltage of the tether power cannot be increased beyond the operating limits of commercially available power converters, thereby restricting system scalability and operational capability. There is therefore a need for a tethered air vehicle architecture that can accommodate tether-supplied power at voltage levels exceeding the operating voltage limitations of conventional onboard power conversion components.

Objects of the Invention
1. The primary object of the present invention is to provide a tethered multi-rotor electric aircraft capable of utilising tether-supplied electric power at elevated voltage levels.
2. Another object of the present invention is to provide a tethered multi-rotor electric aircraft configured to efficiently transfer high-voltage tether-supplied power to onboard energy storage and propulsion systems.
3. Still another object of the present invention is to provide a tethered multi-rotor electric aircraft capable of operating with a power tether cable having reduced weight and reduced physical dimensions.
4. Yet another object of the present invention is to provide a tethered multi-rotor electric aircraft configured to minimize electrical power transmission losses through the tether.
5. Yet another object of the present invention is to provide a tethered multi-rotor electric aircraft capable of sustained operation at increased altitudes.

Summary of the Invention
1. The present invention provides a tethered multi-rotor electric aircraft (100) configured to receive auxiliary electrical power through an electric tether cable (101) and to utilize the auxiliary electrical power for recharging an onboard energy storage system (102) during airborne operation.
2. The energy storage system (102) comprises a plurality of energy storage units (103) electrically connected in series through a series electrical connection (109). Each energy storage unit comprises a plurality of secondary cells electrically connected in series.
3. The aircraft (100) further comprises a plurality of power management units (104) and a plurality of electric fans (106), wherein each power management unit is operatively coupled to a corresponding energy storage unit and is configured to dynamically control a rotational speed of a corresponding electric fan to regulate an amount of auxiliary electrical power utilized by the corresponding energy storage unit for recharging the secondary cells while the aircraft is airborne.
4. In some embodiments, a plurality of inverters (105) are provided between corresponding energy storage units and electric fans. The electric tether cable (101) may comprise a first conductor (108a) and a second conductor (108b) configured to supply auxiliary electrical power across the series-connected energy storage system (102).

Brief description of drawing
The accompanying drawings form a part of the present disclosure and are included to illustrate the invention further and are not intended to limit the scope thereof.
FIG. 1 is a schematic block diagram of a tethered multi-rotor electric aircraft in accordance with an embodiment of the present invention.

Detailed description of the invention
1. The present invention relates to a tethered multi-rotor electric aircraft (100) configured to receive auxiliary electrical power through an electric tether cable (101) and to dynamically regulate utilization of the auxiliary electrical power during airborne operation. The aircraft (100) comprises an energy storage system (102), a plurality of energy storage units (103-1, 103-2, 103-3, ... 103-N), a plurality of power management units (104-1, 104-2, 104-3, ... 104-N), and a plurality of electric fans (106-1, 106-2, 106-3, ... 106-N). In various embodiments, a plurality of inverters (105-1, 105-2, 105-3, ... 105-N), battery management systems, current sensing devices, and other electrical components may additionally be provided.
2. The term “aircraft” as used herein refers to the tethered multi-rotor electric aircraft (100) and may encompass a tethered electric aerial vehicle, multi-rotor electric air vehicle, or other electrically powered aerial vehicle employing a plurality of electric propulsion devices. The terms used herein may encompass equivalent structures, devices, assemblies, and functional implementations capable of performing the respective functions described herein.
3. The energy storage system (102) comprises the plurality of energy storage units (103-1, 103-2, 103-3, ... 103-N) electrically connected in series through the series electrical connection (109). The plurality of energy storage units (103-1, 103-2, 103-3, ... 103-N) may collectively provide an electrical potential corresponding substantially to the combined electromotive forces of the respective energy storage units connected in series.
4. Each energy storage unit (103-1, 103-2, 103-3, ... 103-N) comprises a plurality of rechargeable secondary cells electrically connected in series. The electromotive force of each energy storage unit may therefore correspond substantially to the combined electromotive forces of the plurality of secondary cells connected in series within the respective energy storage unit.
5. The number of energy storage units (103-1, 103-2, 103-3, ... 103-N) and the number of secondary cells included in each energy storage unit may be selected according to desired electrical voltage, energy capacity, propulsion power, aircraft configuration, operating conditions, weight requirements, redundancy requirements, and other requirements of a particular implementation. The specific number of energy storage units and secondary cells is therefore not intended to limit the invention.
6. The aircraft (100) comprises the electric tether cable (101) configured to deliver auxiliary electrical power to the aircraft (100) from a grounded power source (110) or another suitable external electrical power source. The electric tether cable (101) extends between the grounded power source (110) and the aircraft (100) and electrically couples the grounded power source (110) to the energy storage system (102).
7. In one embodiment, the electric tether cable (101) comprises at least two electrical conductors, including a first conductor (108a) and a second conductor (108b), configured to deliver the auxiliary electrical power to the energy storage system (102).
8. The first conductor (108a) may be electrically coupled to a first energy storage unit (103-1) of the series-connected energy storage system (102), while the second conductor (108b) may be electrically coupled to a last energy storage unit (103-N) of the series-connected energy storage system (102). The auxiliary electrical power supplied through the electric tether cable (101) may thereby be delivered across the series-connected energy storage system (102).
9. The grounded power source (110) may supply electrical power through the electric tether cable (101) at a voltage level selected according to the electrical configuration of the energy storage system (102) and the power transmission requirements of the aircraft (100). In one embodiment, the grounded power source (110) is capable of supplying electrical power at a voltage level exceeding 1000 volts.
10. The voltage level supplied through the electric tether cable (101) may be substantially equal to, or otherwise electrically compatible with, the voltage level of the energy storage system (102). Because the energy storage units (103-1, 103-2, 103-3, ... 103-N) are connected in series through the series electrical connection (109), the aggregate electromotive force of the energy storage system (102) may substantially correspond to the sum of the electromotive forces of the respective energy storage units.
11. The use of an elevated tether transmission voltage may permit a desired amount of electrical power to be transmitted through the electric tether cable (101) at a comparatively reduced current relative to transmission of the same power at a lower voltage. The electric tether cable (101) may thereby be configured to provide a desired electrical power transmission capability while considering conductor size, tether weight, electrical losses, thermal characteristics, insulation requirements, mechanical flexibility, and other operating requirements.
12. The particular voltage level of the electric tether cable (101) is not intended to be limited to a particular numerical value unless expressly specified in a claim. The voltage may be selected according to the electrical characteristics of the energy storage system (102), the electric tether cable (101), the grounded power source (110), and the aircraft (100).
13. The aircraft (100) comprises the plurality of electric fans (106-1, 106-2, 106-3, ... 106-N) configured to generate thrust. The electric fans may collectively generate thrust sufficient to provide at least vertical lift of the aircraft (100).
14. Each electric fan (106-1, 106-2, 106-3, ... 106-N) is operatively coupled to a corresponding energy storage unit (103-1, 103-2, 103-3, ... 103-N). The coupling may be electrical and may be provided directly or through one or more electrical power conversion devices.
15. In some embodiments, each electric fan (106-1, 106-2, 106-3, ... 106-N) is coupled to the corresponding energy storage unit through a corresponding inverter (105-1, 105-2, 105-3, ... 105-N).
16. Each inverter (105-1, 105-2, 105-3, ... 105-N), when provided, may receive electrical power associated with the corresponding energy storage unit and control electrical power supplied to the corresponding electric fan. The inverter may thereby control rotational speed of the corresponding electric fan according to one or more control inputs received from the corresponding power management unit (104-1, 104-2, 104-3, ... 104-N).
17. The aircraft (100) comprises the plurality of power management units (104-1, 104-2, 104-3, ... 104-N). Each power management unit is operatively coupled to a corresponding energy storage unit and a corresponding electric fan.
18. Each power management unit (104-1, 104-2, 104-3, ... 104-N) is configured to dynamically control a rotational speed of the corresponding electric fan (106-1, 106-2, 106-3, ... 106-N) to regulate an amount of auxiliary electrical power utilized by the corresponding energy storage unit (103-1, 103-2, 103-3, ... 103-N) for recharging its secondary cells while the aircraft (100) is airborne.
19. The corresponding power management unit may control rotational speed of the corresponding electric fan directly or through an associated inverter (105-1, 105-2, 105-3, ... 105-N) or another suitable electrical power conversion device.
20. Variation of the rotational speed of an electric fan may produce a corresponding variation in electrical power demand associated with the electric fan and the corresponding energy storage unit. An increase in rotational speed may generally result in an increase in electrical power demand, while a reduction in rotational speed may generally result in a reduction in electrical power demand, depending upon characteristics and operating conditions of the propulsion system.
21. The power management unit may thereby dynamically regulate electrical power demand associated with the corresponding electric fan and consequently regulate the amount of auxiliary electrical power utilized by the corresponding energy storage unit for recharging its secondary cells.
22. In one embodiment, each power management unit (104-1, 104-2, 104-3, ... 104-N) monitors one or more operating states of the corresponding energy storage unit (103-1, 103-2, 103-3, ... 103-N) and dynamically controls the rotational speed of the corresponding electric fan based at least in part on the monitored operating states.
23. The monitored operating states may include one or more of state of charge, charging voltage, charging current, temperature, electrical current, electrical voltage, cell condition, or another operating parameter associated with the corresponding energy storage unit or its secondary cells.
24. Each power management unit (104-1, 104-2, 104-3, ... 104-N) may determine a dynamic auxiliary power limit based at least in part on one or more monitored operating states. The dynamic auxiliary power limit may represent an allowable amount of auxiliary electrical power that may be utilized by the corresponding energy storage unit for recharging its secondary cells.
25. The dynamic auxiliary power limit may be represented by an electrical signal, digital data, a control parameter, a calculated value, a command, or another suitable representation of an allowable auxiliary power level.
26. In some embodiments, each power management unit employs at least one feedback control loop to generate or modify the dynamic auxiliary power limit. The feedback control loop may receive one or more measured operating states of the corresponding energy storage unit and may modify the dynamic auxiliary power limit according to the measured operating states.
27. The dynamic auxiliary power limit may be determined such that one or more monitored operating states of the corresponding energy storage unit are maintained within a predefined operating range. The dynamic auxiliary power limit may be continuously, periodically, or conditionally modified in response to changes in one or more monitored operating states.
28. Each power management unit (104-1, 104-2, 104-3, ... 104-N) may dynamically control the corresponding electric fan based at least in part on the dynamic auxiliary power limit. Where the corresponding inverter (105-1, 105-2, 105-3, ... 105-N) is provided, the power management unit may provide the dynamic auxiliary power limit or a corresponding control parameter to the inverter, and the inverter may vary the rotational speed of the corresponding electric fan according to the control parameter.
29. The corresponding energy storage unit may provide electrical power associated with operation of the electric fan while auxiliary electrical power supplied through the electric tether cable (101) is utilized for recharging the secondary cells. Electrical power demand associated with propulsion may therefore affect the amount of auxiliary electrical power available for utilization by the corresponding energy storage unit for recharging.
30. When propulsion power demand increases, the corresponding electric fan may require an increased amount of electrical power, thereby reducing the amount of auxiliary electrical power that may be utilized for recharging, subject to applicable operating conditions and the dynamic auxiliary power limit.
31. Conversely, when propulsion power demand decreases, the electrical power demand of the corresponding electric fan may decrease, thereby permitting a greater amount of available auxiliary electrical power to be utilized by the corresponding energy storage unit for recharging, subject to the dynamic auxiliary power limit and other operating constraints.
32. The power management unit may additionally control rotational speed of the corresponding electric fan according to propulsion requirements of the aircraft (100). Such propulsion requirements may include requirements associated with generating or maintaining vertical lift, maintaining altitude, controlling thrust, maintaining aircraft operation, or responding to propulsion-related operating conditions.
33. The dynamic regulation of fan rotational speed and auxiliary electrical power utilization may occur while the aircraft (100) is airborne. The power management units (104-1, 104-2, 104-3, ... 104-N) may therefore dynamically regulate operation of corresponding electric fans during airborne operation in response to changing operating conditions of corresponding energy storage units and/or changing propulsion requirements.
34. In some embodiments, each power management unit may independently determine a dynamic auxiliary power limit for its corresponding energy storage unit. Accordingly, different energy storage units may have different dynamic auxiliary power limits at a particular time based on differences in state of charge, temperature, charging condition, electrical loading, or other operating states.
35. Each energy storage unit (103-1, 103-2, 103-3, ... 103-N) may further comprise a battery management system configured to monitor and/or manage one or more operating characteristics of its secondary cells. In one embodiment, the battery management system is configured at least to balance charge between the plurality of secondary cells of the corresponding energy storage unit.
36. In one embodiment, each energy storage unit (103-1, 103-2, 103-3, ... 103-N) includes a current sensing device electrically connected in series with its plurality of secondary cells. The current sensing device may generate a signal representative of electrical current flowing through the energy storage unit.
37. The corresponding power management unit may utilize information from the current sensing device to determine or estimate an amount of electrical power utilized by the energy storage unit. Current information may be combined with voltage information or another electrical parameter to determine or estimate auxiliary electrical power utilized by the energy storage unit.
38. The particular current sensing technology, physical configuration, electrical interface, measurement technique, and location of the current sensing device may vary according to a particular implementation.
39. The power management unit may utilize information obtained from the current sensing device together with one or more additional operating parameters, including state of charge, charging voltage, charging current, temperature, or other information associated with the corresponding energy storage unit or its secondary cells, to determine or modify the dynamic auxiliary power limit.
40. The power management unit may be implemented using suitable electronic circuitry, one or more processors, programmable devices, dedicated control circuitry, firmware, software executed by processing circuitry, or combinations thereof. The particular implementation of the power management unit is not intended to limit the invention provided that the power management unit is capable of performing the functions described herein.
41. The plurality of energy storage units (103-1, 103-2, 103-3, ... 103-N) may be physically distributed throughout the aircraft (100) while maintaining the series electrical connection (109). Similarly, an energy storage unit, corresponding power management unit, corresponding inverter, and corresponding electric fan may be physically separated from one another while remaining operatively coupled through suitable electrical connections.
42. The physical arrangement of the electric tether cable (101), energy storage system (102), energy storage units (103-1 to 103-N), power management units (104-1 to 104-N), inverters (105-1 to 105-N), electric fans (106-1 to 106-N), sensing devices, and battery management systems may be modified according to the structural and electrical configuration of the aircraft (100).
43. The association between the energy storage units (103-1 to 103-N) and electric fans (106-1 to 106-N) may likewise be varied. In some implementations, an individual energy storage unit may be associated with a single electric fan. In other implementations, an energy storage unit may be associated with more than one propulsion device, provided that the corresponding power management unit is capable of regulating utilization of auxiliary electrical power according to the disclosed principles.
44. During operation, electrical power may be supplied from the grounded power source (110) through the electric tether cable (101) to the series-connected energy storage system (102). At least a portion of the auxiliary electrical power may be utilized for recharging secondary cells of the respective energy storage units while the plurality of electric fans (106-1 to 106-N) simultaneously operate to generate thrust.
45. During airborne operation, the power management units (104-1 to 104-N) may monitor respective energy storage unit operating states and dynamically regulate rotational speed of corresponding electric fans (106-1 to 106-N). The resulting variation in propulsion electrical demand may regulate the amount of auxiliary electrical power utilized by corresponding energy storage units for recharging.
46. The resulting operating relationship may comprise monitoring an operating state of an energy storage unit, determining or modifying a dynamic auxiliary power limit, controlling rotational speed of a corresponding electric fan based at least in part on the dynamic auxiliary power limit, modifying electrical power demand associated with the electric fan, and thereby regulating auxiliary electrical power utilized for recharging the energy storage unit.
47. The foregoing embodiments are provided for purposes of illustration and are not intended to limit the invention to any particular structure, arrangement, voltage level, number of components, sensing technique, control technique, operating sequence, or numerical value unless expressly specified in a claim.
48. Various modifications, substitutions, rearrangements, and equivalent implementations may be made by a person skilled in the art without departing from the underlying principles of the invention. The scope of the invention is therefore to be determined with reference to the claims and their legally permissible equivalents.
, C , Claims:I/We Claim:
1. A tethered multi-rotor electric aircraft (100), comprising:
an electric tether cable (101) configured to deliver auxiliary electric power to the aircraft (100);
an energy storage system (ESS) (102) comprising a plurality of energy storage units (ESUs) (103) electrically connected in series through a series electrical connection (109), wherein each ESU comprises a plurality of secondary cells electrically connected in series and configured to receive at least a portion of the auxiliary electric power for recharging;
a plurality of electric fans (106) configured to generate thrust, each electric fan being operatively coupled to a corresponding ESU; and
a plurality of power management units (PMUs) (104), each PMU being operatively coupled to a corresponding ESU and configured to dynamically control a rotational speed of a corresponding electric fan to regulate an amount of the auxiliary electric power utilized by the corresponding ESU for recharging the secondary cells while the aircraft (100) is airborne.
2. The tethered multi-rotor electric aircraft (100) of claim 1, wherein the electric tether cable (101) receives electrical power from a grounded power source (110) capable of supplying power at a voltage level exceeding 1000 volts.
3. The tethered multi-rotor electric aircraft (100) of claim 1, wherein the electric tether cable (101) comprises at least two conductors configured to deliver auxiliary electric power to the ESS (102), a first conductor (108a) being electrically coupled to a first ESU (103-1) of the ESS (102) in the series electrical connection (109) and a second conductor (108b) being electrically coupled to a last ESU (103-N) of the ESS (102) in the series electrical connection (109), thereby supplying the auxiliary electric power across the ESS (102).
4. The tethered multi-rotor electric aircraft (100) of claim 1, wherein the electric tether cable (101) supplies auxiliary electrical power at a voltage level substantially equal to a voltage level of the ESS (102).
5. The tethered multi-rotor electric aircraft (100) of claim 1, wherein the plurality of ESUs (103) are electrically connected in series through the series electrical connection (109) such that an electromotive force of the ESS (102) is substantially equal to a sum of electromotive forces of the plurality of ESUs connected in series.
6. The tethered multi-rotor electric aircraft (100) of claim 1, wherein each of the plurality of ESUs (103-1, 103-2, 103-3, ... 103-N) comprises a plurality of secondary cells electrically connected in series such that an electromotive force of each ESU is substantially equal to a sum of electromotive forces of the plurality of secondary cells connected in series.
7. The tethered multi-rotor electric aircraft (100) of claim 1, wherein the plurality of electric fans (106) generate thrust at least to produce vertical lift of the aircraft (100).
8. The tethered multi-rotor electric aircraft (100) of claim 1, further comprising a plurality of inverters (105), each inverter being electrically coupled to a corresponding electric fan and a corresponding ESU.
9. The tethered multi-rotor electric aircraft (100) of claim 8, wherein each of the plurality of PMUs (104-1, 104-2, 104-3, ... 104-N) is electrically coupled to a corresponding inverter (105-1, 105-2, 105-3, ... 105-N) and the corresponding ESU (103-1, 103-2, 103-3, ... 103-N).
10. The tethered multi-rotor electric aircraft (100) of claim 9, wherein each PMU (104-1, 104-2, 104-3, ... 104-N) is configured to monitor one or more operating states of the corresponding ESU and to use at least one feedback control loop to generate a dynamic auxiliary power limit, such that the dynamic auxiliary power limit maintains at least one of the monitored operating states within a predefined range.
11. The tethered multi-rotor electric aircraft (100) of claim 10, wherein the dynamic auxiliary power limit comprises at least one of an electrical signal, digital data, or a control parameter representative of an allowable auxiliary power level.
12. The tethered multi-rotor electric aircraft (100) of claim 10, wherein the monitored operating states include at least a state of charge, charging voltage, charging current, and temperature of the plurality of secondary cells of the corresponding ESU.
13. The tethered multi-rotor electric aircraft (100) of claim 10, wherein each inverter (105-1, 105-2, 105-3, ... 105-N) dynamically varies the rotational speed of the corresponding electric fan (106-1, 106-2, 106-3, ... 106-N) based at least on the dynamic auxiliary power limit.
14. The tethered multi-rotor electric aircraft (100) of claim 13, wherein each inverter (105-1, 105-2, 105-3, ... 105-N) generates a variable electrical power demand at the corresponding ESU with respect to the rotational speed of the corresponding electric fan.
15. The tethered multi-rotor electric aircraft (100) of claim 14, wherein each ESU is configured to utilize the auxiliary electric power in combination with electrical power associated with operation of the corresponding inverter to satisfy the electrical power demand of the inverter.
16. The tethered multi-rotor electric aircraft (100) of claim 15, wherein the electrical power utilized for operation of the corresponding inverter limits an amount of auxiliary electric power utilized by the ESU for recharging the secondary cells.
17. The tethered multi-rotor electric aircraft (100) of claim 1, wherein each inverter (105-1, 105-2, 105-3, ... 105-N) further varies the rotational speed of the corresponding electric fan (106-1, 106-2, 106-3, ... 106-N) based on propulsion requirements of the aircraft (100).
18. The tethered multi-rotor electric aircraft (100) of claim 1, wherein dynamic regulation of fan speed and auxiliary electric power utilization occurs while the aircraft (100) is airborne.
19. The tethered multi-rotor electric aircraft (100) of claim 1, wherein each ESU (103-1, 103-2, 103-3, ... 103-N) further comprises a battery management system at least configured to balance charges between the plurality of secondary cells of the corresponding ESU.
20. The tethered multi-rotor electric aircraft (100) of claim 1, wherein each ESU (103-1, 103-2, 103-3, ... 103-N) includes a current sensing device electrically connected in series with the plurality of secondary cells, the current sensing device being configured to enable a corresponding PMU (104-1, 104-2, 104-3, ... 104-N) to measure an amount of auxiliary electric power utilized by the ESU.