CH714860B1 - Method for automatically assisting landing of an aircraft and system and computer program product therefor. - Google Patents

Abstract

The invention relates to a method for automatically assisting the landing of an aircraft (1) on a landing platform (2) using a tether (3) which connects the aircraft (1) to the landing platform (2) and a cable winch (4). which the tether (3) can be rolled up and unrolled automatically. The invention also relates to a computer program with program code means set up to carry out a method of the aforementioned type when the computer program is run on a computer. The invention also relates to a system for automatically supporting the landing of an aircraft (1) on a landing platform (2) by means of a tether (3), the system having at least one control device (5), a sensor system (6) and one controlled by the control device ( 5) has a controllable cable winch (4) on which the retaining cable (3) can be rolled up and unrolled by a motor.

Description

The invention relates to a method for automatically supporting the landing of an aircraft on a landing platform by means of a tether that connects the aircraft to the landing platform, and a winch with which the tether can be rolled up and unwound automatically. The invention also relates to a system for automatically assisting the landing of an aircraft on a landing platform by means of a tether, the system having at least one control device, a sensor system and a cable winch which can be controlled by the control device and on which the tether can be rolled up and down by a motor. The invention also relates to a computer program product comprising a program code which, when executed on a control device of the system, causes the method of the aforementioned type to be carried out.

The landing of an aircraft on a landing platform can be associated with particular difficulties in certain situations, e.g. when the landing platform is on a high-rise building and strong and possibly gusty winds are present. Another difficult landing situation occurs when the aircraft is to land on a landing platform located on a ship, e.g., on a ship's deck. Landing can be made more difficult in particular by rough seas and strong and changeable winds.

In the field of manned helicopters, the Recovery Assist, Secure and Traverse System (RAST) from Curtiss-Wright is known. In this system, the pilot first performs a normal approach to the landing platform on a ship and then enters a hovering state. A pilot line is lowered from the helicopter to the landing platform and connected to a main ship tether by shipboard personnel. The main tether is then pulled up to the helicopter using the pilot line and locked there. As soon as a period of slight ship movement occurs, the pilot requests personnel on board the ship to tighten the main tether. The onward landing approach to the landing platform is then controlled by the pilot, with the main tether maintained under tension through manual operation of the system by personnel on board the ship. This whole process requires a significant amount of manual operation.

The invention is based on the object of improving the landing of an aircraft on a landing platform by means of a tether in such a way that the method can be carried out largely automatically and accordingly fewer or no manual interventions are required. In particular, the method should also be suitable for landing processes of unmanned or autonomous aircraft.

[0005] This object is achieved by a method of the type mentioned at the outset and with the method features according to independent patent claim 1. Advantageous refinements of the method emerge from the dependent patent claims. Accordingly, in the method for automatically assisting the landing of an aircraft according to the invention, a flight attitude adjustment control is carried out, by which the current attitude of the aircraft is regulated to a target position relative to the landing platform, based on the actual position of the landing platform characterizing signals from the sensors.

In an advantageous development of the invention, the method involves: carrying out position control of the aircraft, in which an actual position of the aircraft is controlled to a desired position relative to the landing platform based on at least one signal from a sensor system.

The method according to the invention has the advantage that the aircraft is stabilized by the tensile force exerted mechanically by the tether on the aircraft. In addition, the effective rotor thrust of the aircraft is increased, as a result of which the aircraft is stabilized against gusts and the wake effects of objects in the vicinity, such as buildings or ship superstructures. The aircraft is restricted and centered with regard to position changes by the tether. The possible degrees of freedom of the aircraft are limited by the tether, so that a restoring force is generated in the direction of the anchor point of the tether, to which the tether is attached to the landing platform, as soon as a lateral or longitudinal displacement of the aircraft relative to the landing platform occurs.

By carrying out the position control of the aircraft, an additional stabilization of the aircraft relative to the landing platform can be achieved. Position control minimizes deviations in the position of the aircraft from the target position. The target position can be the anchor point of the tether, for example. The position control can be carried out, for example, on the basis of sensor signals. In principle, a position signal can be recorded on board the aircraft, e.g. by optically detecting markings on the landing platform or by measuring the cable force vector, or sensors arranged on the landing platform, such as laser scanners, sonar distance sensors or radar sensors, through which the aircraft can be detected. The position control promotes the stabilizing function of the tether even further and protects the tether from excessive load fluctuations.

The cable winch can be arranged on the aircraft and/or on the landing platform. Control in the sense of the present application is understood to be a control in which at least one variable to be controlled is controlled based on one or more detected sensor signals in relation to a setpoint in such a way that the deviation between the actual value of the variable to be controlled and the setpoint is minimized or ideally equal to zero.

According to an advantageous development of the invention, it is provided that the position control is carried out based on a cable force of the tether representing the sensor signal. The signal representing the rope force of the tether is thus at least one input variable of the position control. In this way, a constant load on the tether can be promoted by the position control.

According to an advantageous development of the invention it is provided that the position control is performed based on an angle signal from the sensors, which represents a rope angle of the tether relative to the aircraft and/or a rope angle of the tether relative to the landing platform. Accordingly, the angle signal can be at least one input variable for the position control. Since the alignment of the tether relative to the aircraft and/or relative to the landing platform is an indicator of the deviation of the actual position of the aircraft from the target position, a suitable input variable for position control can be obtained in this way with little effort.

[0012] In this case, the remaining cable length of the tether, which is a measure of the distance between the aircraft and the landing platform, can also be used as a supplement. By taking such sensor signals into account, the position of the aircraft relative to the landing platform can also be determined. This eliminates the need for complex instrumentation on the landing deck or data transmission systems with which data can be exchanged between the aircraft and the landing platform. The cable angle of the tether relative to the aircraft or relative to the landing platform can in particular include two spatial components, for example a longitudinal and a lateral component of the cable angle.

The aircraft is reliably guided to the landing platform by means of the tether. The tether progressively limits the aircraft's degrees of freedom as the aircraft approaches the landing pad. Thereby the deviation of the aircraft with respect to the landing position can be controlled. In addition, due to the cable angle, a restoring force is applied to the aircraft.

In contrast to the RAST system, which is designed for manned helicopters, the present invention can also be used to land unmanned and/or autonomous aircraft. Due to the detected sensor signals, which can be measured by the tether, it is possible to provide a controller that holds the relative position of the aircraft to the anchor point on the landing platform and can compensate for a rate of descent of the aircraft, taking into account the lift of the landing platform.

It is advantageous to combine the inventive method with a control of the cable force of the tether, for example such that the cable force of the tether is controlled to a predetermined cable force setpoint, based on at least one input signal of the sensors. The corresponding input signal from the sensors can be carried out, for example, by measuring the current cable force, for example using a force sensor or a tension sensor. As a result, not only can undesired sagging of the tether be detected or avoided in advance. In addition, a constant approach of the aircraft to the landing platform can be generated in a reliable manner, e.g. by means of a force sequence control. Alternatively or additionally, it is advantageous to use a tether with sufficient elasticity, so that undesired sagging of the cable can also be avoided via stretching effects of the tether.

The above-mentioned flight attitude adjustment control makes it possible to adjust the flight attitude of the aircraft to the existing actual position of the landing platform, which is particularly important for ship deck landings in rough seas. This makes it possible to align the landing gear of the aircraft parallel to the landing platform, especially at the end of the landing process, and thus to still be able to land safely even if the landing platform is in a significant inclined position. By limiting the range of movement of the aircraft, the invention makes it possible to achieve better adaptation of its position to the position of the landing platform. This means that helicopters, for example, can land on a much more sloping surface than before, because the mast torques on the rotor mast can be significantly reduced as a result. This is an important contribution to all-weather capability in ship deck landings.

The flight attitude adjustment control can be carried out, for example, during the entire landing process of the aircraft, which is assisted by the tether.

According to an advantageous development of the invention, it is provided that the flight attitude adjustment control is activated when the distance between the aircraft and the landing platform falls below a minimum value after the cable winch has rolled in the tether. Accordingly, the attitude adjustment control is not permanently active during the landing process of the aircraft guided by the tether, but only in a final phase of the landing approach, in which the aircraft is already relatively close to the landing platform. For this purpose, a certain rolling-in process of the retaining cable must first be carried out, for example halving the initial cable length. Then the attitude adjustment control is activated. The activation criterion for the attitude adjustment control, namely that the distance between the aircraft and the landing platform falls below a minimum value, can be determined on the basis of different sensor-detected data. For example, the distance can be determined by the remaining rope length of the tether. Alternatively or additionally, sensors of the aircraft can be used for this purpose, e.g. distance sensors on the aircraft, such as laser scanners, sonar distance sensors, radar sensors. Alternatively or additionally, sensors can be used on the landing platform, for example sensors of a comparable type as mentioned above.

According to an advantageous development of the invention, it is provided that the position control is switched off when the flight attitude adjustment control is activated, or the position control is hidden when the flight attitude adjustment control is activated. This avoids any conflict between the position control and attitude adjustment control systems. The transition between the position control and the attitude adjustment control can be made abruptly by switching, or with a smooth transition, namely by the mentioned fade-out of the position control. At the same time, the flight attitude adjustment rule can be displayed.

According to an advantageous development of the invention, it is provided that the aircraft has a flight attitude controller which is set up to automatically keep the aircraft in the horizontal flight attitude. This is particularly advantageous for unmanned and/or autonomous aircraft. The aircraft is automatically stabilized in the horizontal flight attitude by the flight attitude controller.

According to an advantageous development of the invention it is provided that a regulation of the rope force of the tether is carried out to a predetermined rope force target value based on at least one input signal of the sensors. The input signal can be the measured actual rope force of the tether. As a result, the tether can be prevented from sagging and the aircraft can be brought up to the landing platform evenly. For example, the tether can be steadily pulled in, so that the average distance between the aircraft and the landing platform is steadily reduced. The rope force target value can be determined, for example, based on the maximum payload of the aircraft (payload), e.g. as one third of the payload.

[0022] If such a control of the cable force is carried out, the actual cable force detected by the sensors can be used at the same time as an input variable for the position control. In this case, the position control can be designed as a higher-level control for the cable force control, i.e. the cable force control is subordinate to the position control.

According to an advantageous development of the invention, it is provided that the aircraft is an unmanned aircraft and/or an aircraft capable of vertical landing and/or the landing platform is located on a watercraft at sea. For example, the aircraft may be a helicopter or any other type of vertical-landable aircraft. The watercraft can, for example, be a ship or, particularly in the case of smaller unmanned aircraft, a buoy.

According to an advantageous development of the invention, it is provided that at least part of the sensor system is arranged on the landing platform, with the signals required in the aircraft from the sensor system being transmitted via wireless communication from the landing platform to the aircraft to automatically support the landing. In this way, the data exchange to support the automatic landing of the aircraft can be further optimized. For example, the aircraft and the landing platform can each have a wireless communication device, e.g. for communication via radio signals or optical signals.

The object mentioned at the outset is also achieved by a computer program product which includes program code which, when executed on the control device of the system, causes the method to be carried out as previously described. The control device can be assigned to a computer, e.g. a microcontroller or microprocessor be, for example, a computer of a control device of the system explained below. The program code can be stored in a data medium, e.g. in a memory of the system explained below. The advantages explained above can also be realized in this way.

The object mentioned at the outset is also achieved by a system for automatically assisting the landing of an aircraft on a landing platform by means of a tether, the system having at least one control device, a sensor system and a cable winch which can be controlled by the control device and on which the tether is motor-driven can be rolled up and unrolled, the control device being set up to automatically carry out one, several or all steps of a method of the type explained above. The advantages explained above can also be realized in this way.

According to an advantageous development of the invention, it is provided that the sensor system has one, several or all of the following sensors: a) laser scanners on the aircraft and/or on the landing platform, b) inertial sensors on the landing platform, c) sonar distance sensors on the aircraft and/or on the landing platform, d) radar sensors on the aircraft and/or on the landing platform, e) cable force sensor for detecting the cable force of the tether, f) angle measuring device on the aircraft for determining the cable angle of the tether relative to the aircraft and/or an angle measuring device the landing platform to record the cable angle of the tether relative to the landing platform, g) a camera or multi-camera on the aircraft and/or on the landing platform h) cable length meter to record the remaining cable length between the aircraft and the landing platform.

In this way, the system can be adapted to the respective existing requirements for supporting the landing of the aircraft.

The implementation of the attitude adjustment control requires that the actual attitude of the landing platform is determined. This can be done, for example, by inertial sensors that are installed on or on the landing platform and transmit the current actual position of the landing platform to the aircraft via wireless communication. Alternatively or additionally, sensors installed on the aircraft can also be used, e.g. by using several non-contact distance measurements, e.g. at least three spatially distributed distance measurements, to record the actual position of the landing platform from the aircraft. For this purpose, for example, scanning and flashing laser scanners, multi-camera systems, sonar distance sensors and radar sensors can be used. The actual position of the landing platform can be detected continuously while the flight attitude adjustment control is being carried out.

The invention is explained in more detail below on the basis of an exemplary embodiment using drawings.

FIG. 1 shows a landing process of an aircraft in a first landing phase and FIG. 2 shows the landing process of the aircraft in a second landing phase.

The reference symbols used in the drawings have the following meanings: 1 aircraft 2 landing platform 3 tether 4 winch 5 control device 6 sensors 7 cable force 8 anchor point 9 spherical surface segment α cable angle

FIG. 1 shows an aircraft 1 which is to carry out a landing operation on a landing platform 2 which is shown lying at an angle in this case. The aircraft 1 has a system for automatically assisting landing on the landing platform 2 by means of a tether 3 . The system has a control device 5, a sensor system 6 and a cable winch 4 that can be controlled by the control device. In the exemplary embodiment shown, the cable winch 4 is arranged on the aircraft 1; alternatively, the cable winch 4 can also be arranged on the landing platform 2.

1 shows a state in which the tether 3 is already attached to an anchor point 8 on the landing platform 2 . As a result, the possible freedom of movement of the aircraft 1 is limited to a segment 9 of the spherical surface. At least the rope force 7 occurring in the tether 3 and the rope angle α of the tether are determined by the sensors 6 . In the first landing phase shown in FIG. 1, the aircraft 1 is still relatively far away from the landing platform 2. By rolling up the tether 3 by means of the cable winch 4, this distance is reduced. In the first landing phase shown in FIG. 1, the position of the aircraft 1 is initially regulated relative to the landing platform 2 in such a way that the aircraft 1 is stabilized vertically over the anchor point 8 as precisely as possible.

FIG. 2 shows the landing of the aircraft in a second landing phase, which follows the first landing phase. The aircraft 1 is now significantly closer to the landing platform 2, i.e. the remaining length of the tether 3 is significantly shorter. In this second landing phase, the previously mentioned position control is no longer carried out. Instead, a flight attitude adjustment control is carried out, by means of which the aircraft is now controlled in parallel to the landing platform 2. If the actual position of the landing platform 2 changes, the flight position of the aircraft is also automatically adjusted to this by the flight position adjustment control.

The entire landing process of the aircraft 1 on the landing platform 2 can take place, for example, in the following phases: 1. The aircraft 1 approaches the landing platform 2 with conventional navigation, e.g. by autonomous control with simultaneous flight attitude control, which the aircraft 1 automatically maintains level flight. 2. Unrolling the tether 3 using the winch 4 and fastening the tether 3 to the anchor point 8, or alternatively to a winch located on the landing platform 2. 3. Constant rolling up of the tether 3 by means of the cable winch 4 while carrying out the position control of the aircraft 1, if necessary additionally by a horizontal position control of the aircraft 1 by the flight attitude controller. 4. Transition from position control to attitude adjustment control when aircraft 1 is in the second landing phase (according to FIG. 2), e.g. when the distance between aircraft 1 and landing platform 2 falls below a minimum value. In this case, the attitude controller is also switched off, since the attitude of the aircraft 1 is aligned parallel to the landing platform 2 by the attitude adjustment control.

Claims (13)

1. Method for automatically supporting the landing of an aircraft (1) on a landing platform (2) by means of a tether (3) which connects the aircraft (1) to the landing platform (2) and a cable winch (4) with which the Tether (3) can be rolled up and unrolled automatically, characterized by: - Carrying out a flight attitude adjustment control, by which a current flight attitude of the aircraft (1) is regulated to a target position relative to the landing platform (2), based on an actual position of the landing platform (2) characterizing signals from a sensor system (6). 2. The method according to claim 1, characterized by: - Carrying out a position control of the aircraft (1), in which an actual position of the aircraft (1) based on at least one signal from the sensors (6) is controlled to a target position relative to the landing platform (2). 3. The method according to claim 2, characterized in that the position control is carried out based on a cable force (7) of the retaining cable (3) representing the sensor system (6). 4. The method according to claim 3, characterized in that the control of the cable force (7) of the retaining cable (3) is carried out to a predetermined cable force target value based on at least one input signal of the sensor (6). 5. The method according to any one of claims 2 to 4, characterized in that the position control is carried out based on an angle signal from the sensors (6) which indicates a cable angle (α) of the tether (3) relative to the aircraft (1) and/or a Rope angle (α) of the tether (3) relative to the landing platform (2) represents. 6. The method according to any one of the preceding claims, characterized in that the flight attitude adjustment control is activated if, after the cable winch (4) has rolled in the tether (3), the distance between the aircraft (1) and the landing platform (2) falls below a minimum value. 7. The method according to any one of claims 2 to 6, characterized in that the position control is switched off when the attitude adjustment control is activated, or the position control is hidden when activating the attitude adjustment control. 8. The method according to any one of the preceding claims, characterized in that the aircraft (1) has a flight attitude controller which is set up to automatically keep the aircraft (1) in the horizontal flight attitude. 9. The method according to any one of the preceding claims, characterized in that the aircraft (1) is an unmanned aircraft and/or an aircraft capable of vertical landing (1) and/or the landing platform (2) is located on a watercraft at sea. 10. The method according to any one of the preceding claims, characterized in that at least part of the sensor system (6) is arranged on the landing platform (2), the signals of the sensor system (6) required in the aircraft (1) being transmitted via wireless communication can be transmitted from the landing platform (2) to the aircraft (1). 11. System for automatically supporting the landing of an aircraft (1) on a landing platform (2) by means of a tether (3), the system having at least one control device (5), a sensor system (6) and one of the control device (5) controllable cable winch (4) on which the retaining cable (3) can be rolled up and down by a motor, characterized in that the control device (5) is set up for automatically carrying out a method according to one of Claims 1 to 10. 12. System according to claim 11, characterized in that the sensor system (6) has one, several or all of the following sensors: a) Laser scanners on the aircraft (1) and/or on the landing platform (2), b) inertial sensors on the landing platform (2), c) sonar distance sensors on the aircraft (1) and/or on the landing platform (2), d) radar sensors on the aircraft (1) and/or on the landing platform (2), e) rope force sensor for detecting the rope force (7) of the retaining rope (3), f) Angle measuring device on the aircraft (1) for determining the cable angle (a) of the tether (3) relative to the aircraft (1) and/or an angle measuring device on the landing platform (2) for detecting the cable angle (a) of the tether (3) relative to the landing platform (2), g) a camera or multi-camera on the aircraft (1) and/or on the landing platform (2), h) Rope length meter to record the remaining rope length between the aircraft (1) and the landing platform (2). 13. Computer program product which comprises program code which, when executed on a control device (5) of a system according to one of claims 11 or 12, causes a method according to one of the preceding claims 1 to 10 to be carried out.