JP7569262B2 - Multicopter - Google Patents

Description

This disclosure relates to a multicopter.

As a document related to multicopters, Patent Document 1 discloses a multicopter having a battery and a generator that supplies power to the battery. In the multicopter disclosed in Patent Document 1, when the remaining charge in the battery is low, the flight of the multicopter is restricted, power for flight is supplied from the generator, and the remaining power is supplied to the battery.

JP 2020-138594 A

If an abnormality occurs during flight of a multicopter and the generator stops, it is desirable to make an emergency landing of the multicopter. Here, the remaining battery charge of the battery is usually managed by the generator so that the SOC (State of Charge) is maintained within a predetermined usage range, but the usage range is often set to a fixed value regardless of the altitude of the multicopter's aircraft. Therefore, if the generator stops near the lower limit of the SOC usage range, depending on the altitude of the aircraft, the amount of energy required for landing may be insufficient, and a stable emergency landing may not be possible with the battery alone. Note that Patent Document 1 does not disclose anything about the possibility of a stable emergency landing not being possible depending on the altitude of the aircraft.

Therefore, this disclosure has been made to solve the above-mentioned problems, and aims to provide a multicopter that can make a stable emergency landing from any altitude.

One form of the present disclosure made to solve the above problems is characterized in that a multicopter having an aircraft, a battery capable of charging and discharging power to fly the aircraft, and a generator that supplies the power to the battery has a control unit that raises the lower limit of the battery's charging rate usage range the higher the altitude of the aircraft.

According to this embodiment, by setting the lower limit of the battery charging rate usage range higher as the altitude of the aircraft increases , even if the generator stops abnormally during flight of the multicopter, a minimum battery charging rate can be always ensured so that the multicopter can make a stable emergency landing using only the battery power, regardless of the altitude.

In the above aspect, it is preferable that the control unit operates the generator in a charging mode for rapidly charging the battery with the power when the charging rate of the battery is less than the lower limit of the charging rate usage range.

According to this embodiment, by operating the generator in charging mode to rapidly charge the battery, the battery charge rate can be ensured so that the multicopter can make a stable emergency landing using only the battery. This allows the multicopter to make a stable emergency landing from any altitude more reliably.

In the above aspect, it is preferable that the control unit calculates an emergency landing speed in accordance with wind speed , and sets a lower limit value of the charging rate usage range higher as the emergency landing speed is slower .

This allows the multicopter to make a stable emergency landing from any altitude without losing its aircraft attitude, even in strong winds.

The multicopter disclosed herein can perform a stable emergency landing from any altitude.

FIG. 1 is an external perspective view of a multicopter according to first and second embodiments. FIG. 1 is a block diagram showing a configuration of a multicopter according to a first embodiment. FIG. 4 is a flowchart showing the contents of control performed in the first and second embodiments. FIG. 4 is a flowchart illustrating a method for calculating an SOC lower limit value according to the first embodiment. FIG. 2 is a diagram showing an example of a map that defines the relationship between aircraft altitude and the amount of energy required for landing. FIG. 2 is a diagram showing the current full charge capacity and the amount of energy required for landing. 1 is a diagram showing the flight state of a multicopter and a lower limit value of SOC. FIG. 11 is a block diagram showing the configuration of a multicopter according to a second embodiment. FIG. 11 is a flowchart illustrating a method for calculating an SOC lower limit value according to a second embodiment. FIG. 2 is a diagram illustrating the relationship between airspeed, ground speed, and wind speed. FIG. 2 is a diagram showing an example of a map defining the relationship between wind speed and emergency landing speed. FIG. 2 is a diagram showing an example of a map that defines the relationship between the aircraft altitude, the amount of energy required for landing, and the emergency landing speed.

The following describes an embodiment of the multicopter disclosed herein.

First Embodiment
First, the first embodiment will be described.

<Overview of Multicopter>
(Multicopter configuration)
As shown in FIG. 1 , the multicopter 1 of this embodiment has an airframe 11 and an engine-generator unit 12 .

The aircraft 11 is provided with a propeller 21, a motor 22, and an aircraft main body 23.

There are multiple propellers 21. The multicopter 1 flies by rotating these multiple propellers 21.

The motor 22 is provided on each propeller 21 and rotates the propeller 21. As shown in FIG. 2, the motor 22 is electrically connected to a battery 31 and the engine generator unit 12 (more specifically, a generator 42) via a power control unit (hereinafter referred to as "PCU") 32, which will be described later. As a result, the power (generated current) generated by the engine generator unit 12 and the power (discharge current) discharged from the battery 31 are supplied to the motor 22 via the PCU 32, for example as a supply current.

As shown in FIG. 2, the aircraft main body 23 is provided with a battery 31, a PCU 32, and an altitude sensor 33.

The battery 31 is a charging/discharging unit (secondary battery, storage battery) that can charge and discharge the power to fly the aircraft 11. As shown in FIG. 2, the battery 31 is electrically connected to the engine generator unit 12 (more specifically, the generator 42) via the PCU 32, and charges the battery with the power generated by the engine generator unit 12. The battery 31 is also electrically connected to the motor 22 via the PCU 32, and discharges the power to be supplied to the motor 22.

The PCU 32 is configured as a small computer and controls the entire multicopter 1. For example, the PCU 32 controls the operation of the engine 41 and controls the power generation by the generator 42. The PCU 32 receives power generated by the engine generator unit 12, supplies and receives power (charging and discharging current) to and from the battery 31, and supplies power (supply current) to the motor 22.

The altitude sensor 33 is an altitude acquisition unit that measures the altitude of the aircraft 11 (i.e., the altitude of the multicopter 1). The PCU 32 then acquires information on the altitude of the aircraft 11 measured by this altitude sensor 33 (current altitude information).

As shown in Figures 1 and 2, the engine generator unit 12 includes an engine 41 and a generator (i.e., a power generator) 42. The engine 41 is the power source for the generator 42, and is, for example, a small diesel engine or a reciprocating engine. That is, the engine 41 drives the generator 42 to generate electricity to be supplied to the motor 22 or the battery 31 (i.e., the electricity to fly the aircraft 11). The generator 42 supplies power to the battery 31.

In addition, in the multicopter 1 of this embodiment, a series hybrid system is configured with the motor 22, battery 31, and engine 41. That is, in the multicopter 1, the engine 41 is used only for generating electricity, the motor 22 is used to drive the propeller 21, and a system is configured with the battery 31 for recovering electricity. In this way, the multicopter 1 flies by generating electricity in the generator 42 driven by the engine 41, and using the generated electricity to drive the motor 22 and drive the propeller 21. In addition, the multicopter 1 temporarily stores surplus electricity generated by the generator 42 driven by the engine 41 in the battery 31, and uses it to drive the motor 22 as needed.

(Multicopter action)
The multicopter 1 configured as described above flies by supplying power to the motor 22 and rotating the multiple propellers 21. The rotation speed of the propellers 21 is controlled and the lift obtained by the rotation of the propellers 21 is balanced with the gravity of the multicopter 1 itself, thereby realizing hovering flight and forward, backward, and left-right movement flight of the multicopter 1. In addition, by increasing the lift generated by the propellers 21, the multicopter 1 can achieve ascending flight, and by decreasing the lift generated by the propellers 21, the multicopter 1 can achieve descending flight.

<SOC management>
In this embodiment, the SOC of the battery 31 is controlled and managed by the PCU 32 so that the multicopter 1 can make a stable emergency landing using only the battery 31 from any altitude, even if the engine generator unit 12 stops for some reason.

Specifically, the PCU 32 performs control based on the flowchart shown in Figure 3.

As shown in FIG. 3, first, the PCU 32 calculates the SOC lower limit (step S1). Here, the "SOC lower limit" is the lower limit of the SOC usage range (charging rate usage range) of the battery 31.

In this embodiment, the PCU 32 calculates the SOC lower limit value as shown in Figure 4. As shown in Figure 4, the PCU 32 acquires the current altitude of the aircraft 11 from the altitude sensor 33 (step S11). Note that instead of acquiring the current altitude of the aircraft 11 from the altitude sensor 33, the PCU 32 may acquire position information of the aircraft 11 from the GPS 53 described below and calculate the current altitude of the aircraft 11 from the acquired position information.

Next, the PCU 32 uses, for example, the map shown in FIG. 5 to calculate the total amount of energy required for landing using the battery 31 alone, i.e., the total amount of energy required for the battery 31 alone to make a stable emergency landing of the multicopter 1 if the engine generator unit 12 stops (hereinafter referred to as the "amount of energy required for landing") (step S12).

Figure 5 is a map that specifies the relationship between the altitude of the aircraft 11 and the amount of energy required for landing. As shown in Figure 5, the higher the altitude of the aircraft 11, the greater the amount of energy required for landing. Note that Figure 5 shows an example in which the emergency landing speed is 3 m/s. Also, in the map of Figure 5, if the emergency landing speed is slow, more time is required to make an emergency landing, so more energy is required for landing. On the other hand, if the emergency landing speed is fast, less time is required to make an emergency landing, so less energy is required for landing.

Next, the PCU 32 calculates the lower limit SOC value using the amount of energy required for landing calculated in step S12 (step S13).

Specifically, as shown in Fig. 6, the PCU 32 calculates the SOC lower limit value using the following formula based on the "current full charge capacity" of the battery 31, which takes into account the capacity reduction due to deterioration of the battery 31 from the "initial full charge capacity" of the battery 31, and on the "amount of energy required for landing". Note that the "full charge capacity" is the capacity that can be taken out from the battery 31 in a fully charged state.
[Equation 1]
SOC lower limit = (amount of energy required for landing) / (current full charge capacity)

In this way, the PCU 32 calculates the SOC lower limit value and changes the SOC lower limit value depending on the altitude of the aircraft 11.

Returning to the explanation of FIG. 3, the PCU 32 determines whether the current SOC is less than the SOC lower limit calculated in step S1 (step S2). The PCU 32 obtains the current SOC from the battery 31 as SOC information (see FIG. 2).

If the PCU 32 determines that the current SOC is less than the SOC lower limit (step S2: YES), it issues a generator charging output point operation instruction (step S3). Here, "issuing a generator charging output point operation instruction" means issuing an instruction to the engine generating unit 12 to operate in a charging mode that rapidly charges the battery 31 with power. In this way, the PCU 32 operates the engine generating unit 12 in the charging mode when the current SOC is less than the SOC lower limit.

On the other hand, if the PCU 32 determines that the current SOC is equal to or greater than the SOC lower limit (step S2: NO) and equal to or greater than the SOC upper limit (step S4: YES), it issues a generator optimal fuel efficiency output point operation instruction (step S5). Here, "issuing a generator optimal fuel efficiency output point operation instruction" means issuing an instruction to the engine-generator unit 12 to operate in a fuel efficiency mode that provides optimal fuel efficiency. In this way, when the current SOC is equal to or greater than the SOC upper limit, the PCU 32 operates the engine-generator unit 12 in the fuel efficiency mode. The "SOC upper limit" is the upper limit of the usable range of the SOC of the battery 31.

If the PCU 32 determines that the current SOC is equal to or greater than the lower SOC limit (step S4: NO) and less than the upper SOC limit (step S4: NO), the process returns to step S1.

By carrying out the above-mentioned control, the multicopter 1 is flown as shown in Figure 7. As shown in Figure 7, when the altitude of the aircraft 11 is increased from a state of constant altitude cruising (i.e., flight with the aircraft 11 at a constant altitude), the amount of energy required for landing increases, so the SOC lower limit is increased and constant altitude cruising is performed. Then, when the altitude of the aircraft 11 is subsequently lowered, the amount of energy required for landing decreases, so the SOC lower limit is lowered and constant altitude cruising is performed.

According to this embodiment, the PCU 32 changes the lower limit of the SOC of the battery 31 depending on the altitude of the aircraft 11.

In this way, by changing the SOC lower limit value according to the altitude of the aircraft 11, a minimum SOC of the battery 31 can always be ensured so that the multicopter 1 can make a stable emergency landing using only the battery 31, even if the engine generator unit 12 stops abnormally while the multicopter 1 is flying. Therefore, the multicopter 1 can make a stable emergency landing using only the power of the battery 31, regardless of the altitude.

Also, in the past, as shown by the dashed line in Figure 7, the SOC lower limit was set high and the usable range of SOC was narrow, which tended to increase the number of times the battery 31 was charged and discharged. In contrast, in this embodiment, the SOC lower limit is set low without changing the SOC upper limit, which widens the usable range of SOC, thereby reducing the number of times the battery 31 is charged and discharged, and suppressing the rate at which the battery 31 deteriorates.

For example, if the altitude of the aircraft 11 is increased or if the multicopter 1 is affected by external disturbances such as wind, the power consumption of the motor 22 increases, and the SOC of the battery 31 may fall below the lower SOC limit.

Therefore, when the SOC of the battery 31 is below the lower SOC limit, the PCU 32 operates the engine generator unit 12 in charging mode.

In this way, by operating the engine generator unit 12 in charging mode to rapidly charge the battery 31 with power, the SOC of the battery 31 can be secured so that the multicopter 1 can make a stable emergency landing using the battery 31 alone. Therefore, the multicopter 1 can make a stable emergency landing from any altitude more reliably.

Second Embodiment
Next, a second embodiment will be described, but only the points different from the first embodiment will be described, and a description of the points in common with the first embodiment will be omitted.

When the multicopter 1 is descending to make an emergency landing, if the wind speed is high, it is difficult for the attitude of the multicopter 1 to stabilize. In such a situation where the wind speed is high and the attitude of the multicopter 1 is difficult to stabilize, if the emergency landing speed (i.e., the descent speed during an emergency landing) is too fast, there is a risk that the multicopter 1 will lose its attitude and will not be able to make a stable emergency landing.

Therefore, in this embodiment, the PCU 32 constantly calculates the current wind speed and changes the emergency landing speed according to the calculated wind speed. For example, the PCU 32 slows the emergency landing speed as the wind speed increases.

In this manner, in this embodiment, the PCU 32 changes the emergency landing speed according to the calculated wind speed, but when the emergency landing speed changes, the amount of energy required for landing also changes. For example, the slower the emergency landing speed, the greater the amount of energy required for landing. As a result, depending on the altitude of the aircraft 11, there is a risk that the amount of energy required for landing will be insufficient, making it impossible to perform a stable emergency landing using the battery 31 alone.

Therefore, in this embodiment, the PCU 32 changes the SOC lower limit value according to the emergency landing speed calculated according to the wind speed. That is, the PCU 32 changes the SOC lower limit value according to the altitude of the aircraft 11 and the emergency landing speed calculated according to the wind speed. In this way, when the PCU 32 changes the SOC lower limit value according to the altitude of the aircraft 11, it also changes the SOC lower limit value taking into account the emergency landing speed calculated according to the wind speed.

In this embodiment, as shown in FIG. 8, the aircraft body 23 of the aircraft 11 is equipped with a flight controller 51, an airspeed sensor 52, and a GPS 53.

The flight controller 51 is a flight control unit that controls the flight of the multicopter 1. The airspeed sensor 52 is an airspeed measurement unit that measures the airspeed. The GPS (i.e., a GPS sensor) 53 is a position measurement unit that measures the position of the multicopter 1.

In this embodiment, when the PCU 32 calculates the SOC lower limit value in step S3 of FIG. 3, the PCU 32 calculates the SOC lower limit value as shown in FIG. 9.

As shown in FIG. 9, first, the PCU 32 measures the airspeed using the airspeed sensor 52 (step S21). Specifically, the PCU 32 acquires the measured airspeed value from the airspeed sensor 52 via the flight controller 51 as the airspeed information.

Next, the PCU 32 measures the ground speed using the GPS 53 (step S22). Specifically, the PCU 32 acquires the ground speed measurement value from the GPS 53 via the flight controller 51 as the ground speed information.

Next, the PCU 32 calculates the wind speed based on the airspeed and ground speed as shown in FIG. 10 (step S23).

Next, the PCU 32 calculates the emergency landing speed based on the wind speed calculated in step S23, for example using the map shown in FIG. 11 (step S24). Note that FIG. 11 is a map that specifies the relationship between the magnitude of the wind speed and the emergency landing speed. In this way, the emergency landing speed is changed according to the wind speed. In other words, the higher the wind speed, the slower the emergency landing speed is.

Next, the PCU 32 obtains the current altitude of the aircraft 11 in the same manner as in step S11 above (step S25).

Next, the PCU 32 calculates the amount of energy required for landing using, for example, a map shown in FIG. 12 (step S26). FIG. 12 is a map that specifies the relationship between the altitude of the aircraft 11, the amount of energy required for landing, and the emergency landing speed. Note that, as an example, FIG. 12 specifies the relationship between the altitude of the aircraft 11 and the amount of energy required for landing when the emergency landing speed is 1 m/s and when the emergency landing speed is 3 m/s. As shown in FIG. 12, when the emergency landing speed is slow, more time is required to make an emergency landing, so more energy is required for landing. On the other hand, when the emergency landing speed is fast, less time is required to make an emergency landing, so less energy is required for landing.

Next, the PCU 32 calculates the SOC lower limit value (step S27) using the amount of energy required for landing calculated in step S26, in the same manner as in step S13 described above.

According to this embodiment, the PCU 32 calculates the emergency landing speed according to the wind speed, and when changing the SOC lower limit value according to the altitude of the aircraft 11, the PCU 32 changes the SOC lower limit value taking into account the emergency landing speed calculated according to the wind speed.

This allows the multicopter 1 to make a stable emergency landing from any altitude without compromising the attitude of the aircraft 11, even in strong winds.

The above-described embodiments are merely examples and do not limit the present disclosure in any way. Needless to say, various improvements and modifications are possible without departing from the spirit of the present disclosure.

1 Multicopter 11 Airframe 12 Engine generator unit 21 Propeller 22 Motor 23 Airframe main body 31 Battery 32 PCU (Power Control Unit)
33 Altitude sensor 41 Engine 42 Generator 51 Flight controller 52 Airspeed sensor 53 GPS

Claims (3)

A multicopter having an aircraft, a battery capable of charging and discharging power for flying the aircraft, and a generator that supplies the power to the battery,
a control unit that increases a lower limit of a range of a charging rate of the battery as the altitude of the aircraft increases ;
A multicopter that features: The multicopter of claim 1,
the control unit, when the charging rate of the battery is less than a lower limit value of the charging rate use range, operates the generator in a charging mode for rapidly charging the battery with the power;
A multicopter that features: In the multicopter according to claim 1 or 2,
The control unit is
Calculate emergency landing speed according to wind speed ,
The lower limit value of the charging rate usage range is set higher as the emergency landing speed is slower .
A multicopter that features:

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