WO2022034001A1

WO2022034001A1 - Method for operating an aircraft which takes off and lands vertically, and aircraft which takes off and lands vertically

Info

Publication number: WO2022034001A1
Application number: PCT/EP2021/072118
Authority: WO
Inventors: Christoph KÄPPNER
Original assignee: Volkswagen Aktiengesellschaft
Priority date: 2020-08-14
Filing date: 2021-08-09
Publication date: 2022-02-17
Also published as: DE102020210349A1

Abstract

The invention relates to a method for operating an aircraft (1) which takes off and lands vertically. The mass (m) of the aircraft (1) is determined by a controller (2). For this purpose, a vertical shear force (F_v) of a drive (5) of the aircraft (1) is determined, and the mass (m) of the aircraft (1) is determined at least on the basis of the determined vertical shear force (F_v) and the gravitational acceleration (g). The aircraft (1) is operated on the basis of the determined mass (m). The invention additionally relates to an aircraft (1) which takes off and lands vertically.

Description

description

Method of operating a vertical take-off and landing aircraft and vertical take-off and landing aircraft

The invention relates to a method for operating an aircraft that takes off and lands vertically and an aircraft that takes off and lands vertically.

In civil and private aviation, strict mass specifications apply to aircraft. Typically, these are defined both as maximum take-off weight (MTOW) and payload in such a way that the maximum passenger capacity, baggage volume and fuel capacity can be used at the same time with a sometimes significant violation of the specified limit values would be connected. For safe operation, the maximum take-off weight (MTOW) must not be exceeded, which means that it must be checked reliably, especially before a flight.

In a method known from US Pat. No. 4,490,802 B, the take-off weight of an aircraft is calculated from measurements of the thrust of the engines and the forward acceleration of the aircraft, which are recorded over a period in which this acceleration is at a maximum after the brake has been released on the runway. An important variable to consider is the rolling friction coefficient of the particular aircraft's landing gear and other factors that induce rolling resistance on the ground. The method calculates this variable as a function of engine thrust and manifest weight for each aircraft launch and updates weighted filter values thereof for use during subsequent launches. Therefore, for each takeoff, an average value of rolling friction is used to calculate takeoff weight, and this average value is closer to the actual value for the existing landing gear condition.

The invention is based on the object of creating a method for operating an aircraft that takes off and lands vertically and an aircraft that takes off and lands vertically, with which a mass of the aircraft can be determined and taken into account when operating the aircraft. The object is achieved according to the invention by a method having the features of patent claim 1 and an aircraft having the features of patent claim 10 . Advantageous configurations of the invention result from the dependent claims.

In particular, a method for operating an aircraft that takes off and lands vertically is made available, with a mass of the aircraft being determined by means of a control device, with a vertical thrust force of a drive of the aircraft being determined for this purpose and a mass of the aircraft at least based on the determined vertical thrust force and a gravitational acceleration is determined, the aircraft being operated as a function of the determined mass.

Furthermore, in particular an aircraft that takes off and lands vertically is created, comprising a control device, wherein the control device is set up to determine a mass of the aircraft, and for this purpose to determine a vertical thrust of a drive of the aircraft, and a mass of the aircraft at least based on the to determine a specific vertical thrust and a gravitational acceleration, and to control the aircraft depending on the determined mass.

The method and the aircraft make it possible to determine a mass of the aircraft. This is done by determining a vertical thrust of an aircraft engine. Since the aircraft can land and take off vertically, an exclusively vertical drive with an exclusively vertically acting lift force is possible. The vertical thrust acts in direct opposition to a weight that acts on the aircraft due to gravity. Since the weight depends on the mass and a gravitational acceleration (also referred to as gravitational acceleration or gravitational acceleration) is known, a mass of the aircraft can be determined at least on the basis of the determined vertical thrust force and a gravitational acceleration. The determined mass of the aircraft is taken into account when the aircraft is operated, for example by adjusting a flight control.

The advantage of the method and the aircraft is that, in the simplest case, only the vertically acting thrust of the drive has to be determined for the procedure. This simplifies determining the mass. The vertically acting thrust force can generally be derived from data from a drive control of the aircraft. A vertically taking off and landing aircraft is in particular a manned or unmanned drone or an air taxi.

The drive includes in particular one or more rotors. The drive is operated in particular by an electric motor. In principle, however, the drive can also be operated by an internal combustion engine.

The control device can be designed individually or combined as a combination of hardware and software, for example as program code that is executed on a microcontroller or microprocessor. However, it can also be provided that parts are designed individually or combined as an application-specific integrated circuit (ASIC).

In one embodiment it is provided that the determination of the mass is carried out in a state of equilibrium of forces between the vertical thrust force and a weight force acting on the aircraft. This allows the mass of the aircraft to be determined solely from the determined vertical thrust and a known value for the gravitational acceleration. The determination is particularly easy to carry out as a result. If F_v is the determined thrust force, g is the known gravitational acceleration and m is the mass of the aircraft, the balance of forces means: m = F_v / g

In a first approximation, the equilibrium of forces is reached in particular when the aircraft is hovering. The mass of the aircraft can therefore be determined, particularly when it is hovering.

In a further development it is provided that, in order to detect the state of the balance of forces during a take-off maneuver of the aircraft, a point in time at which the aircraft took off is recorded and recognized by means of at least one sensor, with the mass being determined at the point in time when the aircraft took off. In this way, the mass can already be determined before the end of the starting maneuver and, if necessary, checked for exceeding a maximum mass. This is based on the idea that at the time of lift-off, a vertical thrust force of the drive is approximately equal to the weight force, so that an equilibrium of forces can be assumed, at least approximately. The at least one sensor can be a position sensor of the aircraft, for example. This recorded in At the time of take-off, a movement and/or an acceleration of the aircraft, which then serves as a trigger for detecting take-off. Alternatively or additionally, a proximity sensor can also be used, for example an ultrasonic sensor and/or an optical distance sensor and/or a radar sensor. Furthermore, a camera installed in the aircraft can also be used to detect the time of take-off, for example by evaluating captured camera images accordingly for a change or movement, such as occurs during take-off. If lift-off is detected, the mass of the aircraft is determined.

In one embodiment, it is provided that a voltage and a current and/or at least one other performance parameter of an electrical drive of the aircraft are determined and/or queried to determine the vertical thrust, with the vertical thrust being determined and/or queried using a characteristic curve Voltage and the determined and / or queried current and / or the at least one other performance parameter is determined. As a result, the vertical thrust does not have to be measured directly, but can be determined indirectly via the voltage and the current, which can be detected on the electric drive and/or a drive controller. For example, the characteristic in which pairs of voltage and current are associated with values for a vertical thrust force can be determined empirically. In particular, other influencing variables and boundary conditions can also be taken into account here. The voltage can in particular be a phase voltage. The current can in particular be a phase current. If several electric drives are provided, a vertical thrust force is determined analogously for each of the drives and then added together.

In one embodiment it is provided that a rotor speed of the drive is detected and/or determined in order to determine the vertical thrust, the vertical thrust being additionally or alternatively determined on the basis of a model. In this way, an effect of the rotors of the drive can be determined directly. The rotor speed can be detected, for example, by means of a sensor designed accordingly for this purpose. In particular, the model can be a physical and/or flow-mechanical model. The model can have been determined empirically and/or theoretically.

In principle, provision can also be made for the vertical shear force to be determined both on the basis of the voltage and the current and/or the at least one other performance parameter and on the basis of a model, with the respective results being taken into account in a weighted manner, for example. In one embodiment it is provided that when determining the vertical thrust force, an ambient pressure and/or an ambient temperature and/or a ground effect and/or a wind direction and/or a wind speed and/or a lateral movement of the aircraft are taken into account. An ambient pressure and/or an ambient temperature influence the density of the ambient air and therefore the flow behavior of rotors of the drive. This can be taken into account, for example, in the characteristic curve and/or in the model-based determination of the vertical shear force. In particular, individual characteristics for different combinations of ambient pressure and ambient temperature can be determined empirically and used to determine the vertical thrust. A ground effect can also be taken into account in the characteristic curve and/or in the model-based determination, for example by means of a corresponding correction or in the form of a correction characteristic curve. In the event of a cross wind, the angle of attack of the rotors and/or the aircraft changes at the time of take-off due to a position stabilization that is usually carried out, so that a vertical thrust force must be determined based on a vertical component of a (total) thrust force of the drive. In this case, the angle of attack and/or the vertical component can be determined, for example, by means of a position sensor of the aircraft.

In one embodiment it is provided that a vertical acceleration is additionally detected by means of at least one sensor and taken into account when determining the mass. In this way, a mass can also be determined outside of an equilibrium of forces. Depending on the direction of the vertical acceleration a_v, the recorded vertical acceleration a_v is then added to or subtracted from the gravitational acceleration g: m = F_v / ( g +/- a_v )

A vertical acceleration can be detected, for example, by means of a position sensor of the aircraft.

One embodiment provides for the mass to be compared with a specified maximum mass, with a take-off maneuver being aborted and/or the aircraft being landed if the determined mass exceeds the maximum mass. As a result, a take-off maneuver can be automatically aborted if the maximum mass (in particular a maximum flight mass or MTOW) is exceeded. In particular, this enables fully automatic operation and fully automatic checking of the Compliance with a maximum take-off mass during flight operations and automatic termination of the flight if the maximum take-off mass is exceeded.

One embodiment provides that during a take-off maneuver of the aircraft, a mass of the aircraft is determined based on the determined vertical thrust and a gravitational acceleration even before the take-off is detected, with the take-off maneuver being aborted if the determined mass exceeds the maximum mass. As a result, there is no need to wait for the time of take-off. Since a thrust force is increased from zero or a low thrust force to a higher thrust force during a take-off maneuver, the take-off maneuver can be aborted even before a balance of forces is reached if the aircraft is overloaded. This makes the process faster and more energy-efficient. A mass of the aircraft can be determined here at least with regard to a lower minimum value, ie the minimum mass of the aircraft can be specified as a result, namely at least the specified maximum mass or the permissible maximum take-off mass.

Further features relating to the configuration of the aircraft result from the description of configurations of the method. The advantages of the aircraft are in each case the same as in the embodiments of the method.

The invention is explained in more detail below on the basis of preferred exemplary embodiments with reference to the figures. Here show:

1 shows a schematic representation of an embodiment of the vertical take-off and landing aircraft;

2 shows a schematic flowchart to illustrate an embodiment of the method for operating an aircraft that takes off and lands vertically.

1 shows a schematic representation of an embodiment of the aircraft 1 that takes off and lands vertically. The aircraft 1 includes a control device 2, a position sensor 3, which detects a position of the aircraft 1, a flight controller 4 and a drive controller 8. The aircraft 1 also includes a drive 5, which can include two or more rotors, for example, and in particular as an electric one Drive is driven by one or more electric motors. The flight controller 4 controls based on sensor data that were detected by the position sensor 3, by driving the Drive control 8 the drive 5 of the aircraft 1 in a conventional manner. The aircraft 1 can be a manned or unmanned drone or an air taxi, for example.

The control device 1 is set up to determine a mass m of the aircraft 1 and, for this purpose, to determine a vertical thrust force F_v of the engine 5 of the aircraft 1, and the mass m of the aircraft 1 at least on the basis of the determined vertical thrust force F_v and a gravitational acceleration g to determine. The control device 4 controls the aircraft 1 as a function of the determined mass m. For example, the control device 2 can transmit a corresponding control signal 6 to the flight controller 4, which then operates, in particular controls, the aircraft according to the determined mass m.

In particular, provision is made for the determination of the mass m to be carried out in a state of equilibrium of forces between the vertical thrust force F_v and a weight force F_g acting on the aircraft 1 . In this case:

F_v = F_g = m g

The following applies: m = F_v / g

At the point in time at which the aircraft 1 takes off, that is to say after a vertical thrust force F_v has been gradually and slowly increased, an equilibrium of forces can be approximately assumed. In particular, it is provided that, in order to detect the state of the balance of forces during a take-off maneuver of the aircraft 1, a point in time at which the aircraft 1 took off is recorded and recognized by means of the position sensor 3, with the mass m being determined at the point in time when the aircraft took off. The time of take-off can be determined, for example, by a non-zero vertical acceleration a_v or some other movement of the aircraft 1 .

Provision can be made for a voltage U and a current I of an electric drive 5 of the aircraft 1 to be determined and/or queried in order to determine the vertical thrust force F_v, with the vertical thrust force F_v being calculated from the determined and/or queried voltage using a characteristic curve 7 U and the determined and/or queried current I is determined. Values for the voltage U and the current I are provided by the drive controller 8, for example, and are transmitted by the latter to the control device 2. The characteristic curve 7 was determined in particular on the basis of empirical tests and is stored, for example, in a memory (not shown) of the control device 2 .

Provision can be made for a rotor speed RPM of the drive 5 to be detected and/or determined in order to determine the vertical thrust force F_v, with the vertical thrust force F_v additionally or alternatively being determined on the basis of a model. The rotor speed RPM can be supplied to the control device 2 by the drive control 8, for example.

Provision can be made for an ambient pressure and/or an ambient temperature and/or a ground effect and/or a wind direction and/or a wind speed and/or a lateral movement of the aircraft 1 to be taken into account when determining the vertical thrust force F_v. Values for the ambient pressure and/or the ambient temperature and/or a wind direction and/or a wind speed are supplied to the control device 2, for example, from an external source, for example via a communication interface (not shown) of the aircraft 1, or by means of its own sensors (not shown ) recorded. The presence and strength of a sideways movement can be determined, for example, by means of the position sensor 3 .

It can be provided that a vertical acceleration a_v is additionally detected by means of the position sensor 3 and taken into account when determining the mass m.

Provision can be made for the mass m to be compared with a specified maximum mass m_max, which corresponds in particular to a maximum take-off mass (MTOW) for the aircraft 1, with a take-off maneuver being aborted and/or the aircraft 1 being landed when the specified mass m dies Maximum mass m_max exceeded. The maximum mass m_max can be stored in a memory of the control device 2, for example.

Provision can be made for a mass m of the aircraft 1 to be determined during a take-off maneuver of the aircraft 1 before the lift-off is detected, based on the (continuously) determined vertical thrust force F_v and a gravitational acceleration g, with the take-off maneuver being aborted when the determined Mass m exceeds the maximum mass m_max. FIG. 2 shows a schematic flow chart to illustrate an embodiment of the method for operating an aircraft that takes off and lands vertically. In particular, the method should be used to check before or during a take-off maneuver of the aircraft whether a maximum take-off weight (MTOW) has been exceeded.

Based on the sensor data recorded by the position sensor 3 of the aircraft, it is checked whether the aircraft is just taking off. For this purpose, for example, a vertical acceleration a_v of the aircraft can be evaluated by comparing it with a threshold value in a method step 100 . Here, the threshold value is chosen to be close to zero, which means that a slight movement of the aircraft already triggers the following ones

Method steps 101-105, in which a mass m of the aircraft is determined and checked.

In method step 101, a thrust force F_v is determined on the basis of a specific and/or queried voltage U and a specific and/or queried current I on the basis of a characteristic curve 7, for example determined empirically. An ambient pressure p_Amb and an ambient temperature T_Amb can be taken into account here, for example by selecting and using an associated characteristic curve 7 for pairs of a current ambient pressure p_Amb and a current ambient temperature T_Amb.

In a method step 102, the determined vertical thrust force F_v is divided by the gravitational acceleration g (approx. 9.81 m/s ^A 2 ). As a result, method step 102 supplies an estimated mass m for the aircraft.

As part of a method step 103, a method step 104 checks whether the determined mass m exceeds a predefined maximum mass m_max, which corresponds to a maximum take-off mass (MTOW) for the aircraft. If this is the case, the starting maneuver is aborted in a method step 105 in that, in particular, a drive power of the drive is reduced.

If, on the other hand, the check in method step 104 shows that the maximum mass m_max has not been exceeded, then the starting maneuver is not aborted.

In particular, the method enables automated checking and monitoring of compliance with a maximum take-off weight (MTOW) for the aircraft and an automated Cancellation of a take-off maneuver or flight of the aircraft if it is determined that the maximum take-off weight (MTOW) has been exceeded.

Reference List

1 aircraft

2 controller

3 position sensor

4 flight controls

5 drive

6 control signal

7 characteristic

8 drive control

100-105 process steps

F_v vertical thrust

F_g weight force m mass of the aircraft m_max maximum mass (maximum flight mass/MTOW) g acceleration due to gravity a_v vertical acceleration

voltage

current

RPM rotor speed p_Amb Ambient pressure

T_Amb Ambient temperature

Claims

Method for operating an aircraft (1) taking off and landing vertically, a mass (m) of the aircraft (1) being determined by means of a control device (2), a vertical thrust force (F_v) of a drive (5) of the aircraft ( 1) is determined, and a mass (m) of the aircraft (1) is determined at least on the basis of the determined vertical thrust (F_v) and a gravitational acceleration (g), and the aircraft (1) depending on the determined mass (m) is operated. Method according to Claim 1, characterized in that the determination of the mass (m) is carried out in a state of equilibrium of forces between the vertical thrust force (F_v) and a weight force (F_g) acting on the aircraft (1). Method according to Claim 2, characterized in that, in order to detect the state of the balance of forces during a take-off maneuver of the aircraft (1), a point in time at which the aircraft (1) takes off is detected and recognized by means of at least one sensor (3), the mass (m) being determined at the point in time when the aircraft (1) took off will. Method according to one of the preceding claims, characterized in that to determine the vertical thrust (F_v) a voltage (U) and a current (I) and/or at least one other performance parameter of an electric drive (5) of the aircraft (1) is determined and /or queried, with the vertical thrust (F_v) being determined by means of a characteristic (7) from the determined and/or queried voltage (U) and the determined and/or queried current (I) and/or from the at least one other performance parameter will. Method according to one of the preceding claims, characterized in that to determine the vertical thrust (F_v) a rotor speed (RPM) of the drive (5) is detected and / or determined, wherein the vertical thrust (F_v) is additionally or alternatively determined based on a model. Method according to one of the preceding claims, characterized in that when determining the vertical thrust (F_v) an ambient pressure (p_Amb) and / or an ambient temperature (T_Amb) and/or a ground effect and/or a wind direction and/or a wind speed and/or a lateral movement of the aircraft (1) are taken into account. Method according to one of the preceding claims, characterized in that a vertical acceleration (a_v) is additionally detected by means of at least one sensor (3) and taken into account when determining the mass (m). Method according to one of the preceding claims, characterized in that the mass (m) is compared with a predetermined maximum mass (m_max), a take-off maneuver being aborted and/or the aircraft (1) being landed when the determined mass (m) exceeds the Maximum mass (m_max) exceeded. Method according to one of the preceding claims, characterized in that during a take-off maneuver of the aircraft (1) even before the lift-off is detected, a mass (m) of the aircraft (1) based on the determined vertical thrust (F_v) and a gravitational acceleration (g) is determined, with the starting maneuver being aborted if the determined mass (m) exceeds the maximum mass (m_max). Vertically taking off and landing aircraft (1), comprising: a control device (2), wherein the control device (2) is set up to determine a mass (m) of the aircraft (1), and for this purpose a vertical

to determine thrust (F_v) of a drive (5) of the aircraft (1), and to determine a mass (m) of the aircraft (1) at least on the basis of the determined vertical thrust (F_v) and a gravitational acceleration (g), and the aircraft (1) depending on the determined mass (m).