Description of Invention

The present invention relates to a monitoring method, in particular to a method for monitoring a flexible wing. The present invention further relates to a monitoring system for implementing the method and to an aerial vehicle comprising the monitoring system.

Background of the invention

Powered air vehicles using soft wings made of fabric (e.g. a canopy/parachute), generally known as paramotors, are used for leisure activities and surveillance, and occasionally for air delivery. Such vehicles may also be referred to as motorised or powered parachutes, paraplanes or PPCs, powered paragliders or PPGs.

The capability of paramotors can be significantly enhanced by designing them to fly autonomously using a control and guidance system following a set of predetermined instructions and/or directed by a remote pilot.

The fabric of the wings degrades over time. Wings degrade, for example, through UV, and through mechanical abrasion (either in contact with the ground, or when folded and unfolded before and after flight). That damage manifests primarily as an increase in wing porosity, as deformations of the wing structure, as changes in line length, and as reductions in wing material strength. Conventionally, the wings are assessed manually by directly measuring the wing and comparing measured dimensions with reference (design) dimensions, by directly measuring cloth porosity (by using machines that apply a pressure difference across sample areas of the cloth and measure flow through it), and/or by cloth strength (tear tests). Degradation may be also detected by monitoring colour changes (fading correlates with degradation).

With safety paramount, particularly with increased automation, there are obvious benefits to a system capable of automatically monitoring the wing for degradation.

Summary of the invention

In one aspect, the present invention provides a method for monitoring a flexible wing, which comprises a canopy and a line system for attaching the canopy to a vehicle, the method comprising operating the wing and measuring during the operation, using one or more sensors connected to the wing, one or more parameters reflecting performance criteria of the wing, and setting baseline performance criteria based thereon, and, following the setting of the baseline performance criteria, subsequently operating the wing, measuring the one or more parameters during the subsequent operation, comparing the one or more parameters measured during the subsequent operation against the baseline performance criteria, and determining whether the performance criteria of the wing is tolerably different to the baseline performance criteria.

The method preferably indicates degradation at a plurality of different levels. It may start with early degradation that will not overly affect operation through to a point at which degradation is sufficient that the wing must be swapped before future launches to prevent the risk of accidents. For such purposes, a plurality of predefined thresholds may be set, wherein, when measured variations of the performance criteria as compared to the baseline performance criteria reach any of the thresholds then a corresponding indication of wing degradation is provided.

According to a further aspect, there is provided a monitoring system for implementing the above method.

According to a yet further aspect, there is provided an aerial vehicle comprising the monitoring system.

Further, preferable, features are presented in the dependent claims.

Brief description of the drawings

Embodiments of the present invention will now be described, by way of nonlimiting examples only, with reference to the Figures in which:

Figure 1 illustrates a paramotor incorporating a monitoring system embodying the present invention; and

Figure 2 shows a basic schematic of the monitoring system.

Detailed description

Generally, embodiments of the present invention provide a method/system for monitoring a wing, in particular for monitoring for degradation of the wing.

With reference to figure 1 , a paramotor 10 consists of a canopy 1 and a ground vehicle 2. The vehicle 2 may be a tricycle, or take other forms. The vehicle 2 consists of a vehicle body and carries a propulsion unit 3 (which may comprise, for example, a propeller, jet or rockets). The vehicle further comprises an undercarriage 4 (e.g. skids, tracks or wheels), and the pilot and/or control system. In flight, the vehicle 2 is suspended from the canopy 1 by a network of lines 7 known as a line system 6, wherein the canopy 1 and line system 6 can together be considered to comprise a wing. Conventionally, the vehicle 2 is suspended at a pair of attachment points (left and right) on the vehicle 2, or any number of attachment points. The line system 6 then branches up to the canopy 1.

Conventionally, the lines 7 attach to the canopy 1 underside at attachment points arranged in rows across the span, from the leading edge 8A towards the trailing edge 8B. These attached points are often called A, B, C rows, indicated as A, B, C on Figure 1. An A, B or C line is one of the lines 7 in the respective A, B or C row. This arrangement allows the angle of attack and camber of the canopy 1 to be adjusted by changing the length of the lines 7 attached to one or more rows of lines. To facilitate this control the branching pattern of the lines 7 is arranged so that the lines 7 originating at one row are brought together into a single line (called a “riser” 9) near the base of the line system 6 and close to the vehicle 2 where it can be adjusted.

Conventionally, the line branching pattern of the line system 6 is arranged so that all the lines 7 from all the rows on the left side of the canopy 1 meet in the left set of risers 9, and all those from the right side meet in the right set of risers 9, allowing steering control by adjusting the lengths of the left and right sets of lines 7 asymmetrically. References herein to the line system 6 are generally referring to a system comprising both lines 7 and risers 9.

The rearmost set of lines 7 (those connected to row C) is conventionally attached at or near the trailing edge 8B of the canopy 1 and are used to control the canopy 1 by distorting the canopy 1 by pulling down the trailing edge 8B, which slows the canopy 1 (and these lines 7 are therefore called brakes). To turn, the brakes are applied asymmetrically and the paramotor vehicle 2 rolls and yaws towards the brake that is pulled down.

In flight, the paramotor 10 is controlled using the brakes, accelerator and throttle. The throttle controls the propulsion force (e.g. motor speed) and determines climb and sink rate. The accelerator controls the canopy’s angle of attack by adjusting the risers/lines 9, 6 in such a way as to change the angle of attack and/or camber and/or reflex of the canopy 1 and therefore the speed of the vehicle 2. The brakes selectively distort the trailing edge 8B of the canopy 1. Symmetric brake application - i.e. pulling down the trailing edge 8B of the left 1A and right 1 B sides of the canopy 1 equally - slows the canopy 1. Asymmetric brake application - pulling down the trailing edge 8B of one side 1 A, 1 B more than the other 1 B, 1 A - turns the canopy 1. For example, applying a brake on the right side 1 B results in a turn to the right. Turning may alternatively or additionally be controlled by asymmetric adjustment of the accelerator system.

The paramotor 10 can also be controlled in roll and yaw by moving the centre of gravity of the ground vehicle 2 laterally, this imparts a turn towards the loaded side. Moving the centre of gravity towards the right will result in a turn to the right.

The paramotor 10 may be controlled by a pilot onboard, and/or by remote control (for example using a radio control system and servos), or by an onboard autopilot, for example using an inertial measurement unit to identify attitude and heading and/or a GPS and/or a computer vision system to identify track and speed and command adjustment of the brakes, throttle and accelerator so as to execute the required flight path.

Prior to take-off, as part of a launch phase, the canopy 1 must first be inflated and rotated into a position substantially above the vehicle 2 so as to create lift. As the vehicle 1 is propelled forward by the propulsion unit 3, the flow of air over the canopy 1 creates lift and causes the vehicle 2 to become airborne.

Initially, the uninflated canopy 1 is laid out behind the aerial vehicle 2, so as to be generally aligned with the longitudinal axis of the aerial vehicle 2. As the propulsion unit 3 is initiated, the wash from the propulsion unit 3 causes the canopy 1 to begin to inflate, and for at least one of the lines 7 to become taut. As the canopy 1 is further inflated and creates a pressurised wing, the canopy 1 starts to rise towards a position where it is generally over the aerial vehicle 1. The phase during which the canopy 1 rises from the ground to being generally above the vehicle 1 may be referred to as the “rotation” phase.

In accordance with embodiments of the present invention, there is provided a method for monitoring the wing, which, as above, comprises the canopy 1 and the line system 6.

In broadest terms, the method comprises operating the wing and measuring during the operation, using one or more sensors 100 connected to the wing 1 , 6, one or more parameters reflecting performance criteria of the wing. A baseline performance criteria is set based on the measured parameters. Following the setting of the baseline performance criteria, the wing is subsequently operated and the one or more parameters are measured. The one or more parameters measured during the subsequent operation are compared against the baseline performance criteria. Based on the comparison, a determination is made whether the performance criteria of the wing is tolerably different to the baseline performance criteria.

It has been determined that degraded wings, including wings that are porous, or distorted or have stretched lines, have a tendency to hang-back on launch, and to suffer from deep-stall issues. The behaviour during launch is that the wing tends to perform the initial inflation phase normally, then pauses during the rotation phase of launch taking longer than normal to come overhead, often sitting back at about 70-80 degrees, around % of the way up. The wing will also have a tendency to subsequently fall-back rather than sit stably overhead. It will often be necessary to use more tension on the A lines to initiate the launch than is normal. Stretched lines may otherwise cause a wing to launch asymmetrically.

It has further been determined that during flight a degraded wing is likely to stall at a higher speed than normal, and to suffer degraded glide and increased sink rate, particularly in turns. In addition a degraded wing will require a higher throttle setting to achieve any set required performance such as level flight, or climb at a commanded climb rate (e.g. 1m/s), or to maintain altitude during a steady turn. Yet further, a degraded wing may respond differently to brake application, requiring a different amount of brake travel to achieve a commanded bank angle. This could be greater brake travel or smaller brake travel depending on the nature of the degradation.

Any of the above detailed exemplary changes/characteristics is indicative of degradation and in accordance with the principles of the present invention may be sensed using appropriate sensors to define parameters for monitoring.

It follows that by the monitoring of appropriate parameters and the comparison of those parameters to predetermined healthy baseline parameters, it is possible to monitor for wing degradation automatically.

The step of operating the wing preferably comprises launching and/or flying the vehicle. The baseline parameters are recorded on the basis of a known healthy wing. The baseline parameters may be determined from a single launch/flight but are more preferably determined from a plurality of launches/flights, in particular from a plurality of launches/flights under different weather conditions. The system, based on the data received from the sensors 100 (possibly with additional input from one or more existing on board sensors 200, i.e. sensors that are not exclusively part of the wing monitoring system, such as but not limited to a sensor for detecting wind speed and direction and/or a sensor for monitoring the speed/acceleration of the paramotor), can for example assess the normal launch characteristics collected over multiple launches in normal operation, and can learn, possibly with the implementation of machine learning or Artificial Intelligence (in a manner that will be readily conceived by those skilled in the art) what a normal launch characteristic is. Most preferably what a normal launch characteristic is in a particular or general set of wind conditions and under particular launch acceleration.

The parameters may comprise one or more or all of the loads in the risers 9 during launch, the force on the risers 9 during launch and the direction that force is aligned with, a change in direction of force on the risers 9 over time as launch progresses, or the tension on one or more of the lines during launch.

The method may operate on the basis of measuring a normal launch vs time trajectory, with a comparison of the difference between the achieved and expected trajectory.

With reference to Figure 2, there is shown a basic schematic of an exemplary monitoring system for implementing the method. The monitoring system comprises one or more sensors 100, a processor 101 and a memory 102. The processor 101 and memory 102 may be part of a main/flight control system for the paramotor 10 or may be separate thereto and specific to the monitoring system. It should be noted that whilst there are three sensors 100 shown connected to the processor 101 there may be more or less sensors provided, as will be readily appreciated by those skilled in the art. There may be arrangements with a single sensor 100 only. Connections between all of the sensors and the processor may be wired or wireless or there could be a combination of wired and wireless sensors provided.

The sensors 100 may comprise any appropriate known sensors in any appropriate combination, which may be selected and suitably mounted as required to the wing, in dependence on the parameter(s) to be measured, including but not limited to accelerometers, gyroscopic sensors, strain gauges, or otherwise.

In one arrangement one or more of the sensors may comprise optical fibres. Optical fibres may be provided as an alternative, or in addition to, any other form of sensor suggested above or otherwise known to those skilled in the art. The optical fibres are preferably flexible.

In such an arrangement, fibre optics/fibre optic load sensors may be embedded or woven into the fabric of the canopy and/or the wing lines 7. As will be appreciated by those skilled in the art, as fibre optics degrade their properties change, in particular a degradation may cause a change in light transmission, including but not limited to one or more of a change in intensity, a change in phase, a change in polarisation, a change in transmission rate (via total internal reflection), a change in the wavelength, or a change in the time it takes for a light packet to travel through the optical fibre. In arrangements utilising fibre optics, the optical fibres may be monitored, wherein any such changes will indicate a degradation of the optical fibre that can be used to identify a resultant degradation in the canopy/wing lines.

Degraded wing lines may stretch, for example, by a distance as little as 5mm over an 8m length. This is not straightforward to measure. Fibre optics provide an effective solution. With one or more optical fibres woven or embedded into one or more of the wing lines, there will be a change in length of the optical fibres with a change in length of the wing lines, this will result in changes, as discussed above, which may be monitored to provide an accurate measure of any increase in length of the lines. Optical fibres embedded or woven into the canopy would degrade with the canopy fabric itself.

The system, as mentioned, may further receive input from existing on board sensors 200 of the paramotor. Figure 2 shows three such sensors. It should be appreciated that such input to the system need not be provided, although is preferred. By way of example only, three existing sensors are shown, this is not to be construed as limiting in any way and is for illustrative purposes only. Exemplary existing sensors may, for example, provide information relating to one or more or all of acceleration, deceleration, flight height, rate of ascent or descent, or throttle and/or brake position, or may comprise atmospheric sensors, including a suitable sensor for measuring wind direction and speed (as referenced above).

The operation of an exemplary embodiment will now be considered further.

There is provided a paramotor as shown in Figure 1 comprising a system as discussed with reference to Figure 2. The system comprises one or more sensors 100 attached to each of the risers 9 for measuring both the load and load direction in each of the risers, independently of one another. The system receives further input from a wind sensor of the wind speed and direction and from a vehicle speed sensor.

The vehicle, with a known healthy wing, is launched on a predetermined number of occasions. On each occasion, the loads and directions of loads in the risers is measured along with the wind speed and direction during launch and the launch acceleration. Baseline performance criteria are set on the basis of this data and stored in the memory of the system. During subsequent launches, this data is measured again and compared to the baseline performance criteria to determine whether there is any tolerable difference. If measured variations are within predefined acceptable limits, it is determined that the wing is sufficiently healthy. If measured variations are outside the predefined acceptable limits then it is determined that the wing is degraded.

An indication of the degradation will be provided.

The indication in this example, or in the context of any above described arrangements, may comprise an alarm, a warning message, a transmission from the vehicle to a ground control, or otherwise. Numerous forms of indication will be readily conceived by those skilled in the art and the invention should not be limited in this regard.

It should be noted that the system in according to any of the described arrangements may be configured to indicate degradation at a plurality of different levels, for example, starting with early degradation that will not overly affect operation through to a point at which degradation is sufficient that the wing must be swapped before future launches to prevent the risk of accidents. The system may alternatively be configured to indicate degradation at a single predetermined level of degradation, with an indication provided at that point.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof. Although certain example embodiments of the invention have been described, the scope of the appended claims is not intended to be limited solely to these embodiments. The claims are to be construed literally, purposively, and/or to encompass equivalents.