Field of the Disclosure

The present disclosure relates to a sensing tension in a rope.

Background of the Disclosure

Loading of a rope, such as a mooring line used for mooring a boat, and in particular over-loading of a rope, may gradually fatigue and damage the rope. This leads to the risk of the rope snapping in service, risking damage to equipment and injury to personnel in the vicinity. It is desirable therefore to determine the load exerted on a rope. Knowledge of the load history of a rope may allow an operator to infer the condition and so remaining service-life of the rope without the requirement for manual inspection of the rope. Further, determination in real-time of the load on a rope during use may allow for an operator to take action to control the load exerted on the rope to reduce the occurrence of overloading of the rope.

Summary of the Disclosure

An objective of the present disclosure is to provide an apparatus and method for sensing tension in a rope, i.e. a line comprising a plurality of intertwined, e.g. twisted, plaited or braided, strands of material, for example, strands of cotton, sisal, nylon, polyester, polyethylene, or metal wire. In particular, an objective is to provide a sensor assembly which may be located within a rope during use to sense tension in the rope.

The foregoing and other objectives are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the Figures.

A first aspect of the present invention comprises a sensor assembly for sensing tension in a rope, the sensor assembly comprising: a housing, a force sensor for sensing mechanical force applied to the housing located outside the housing, and a controller for controlling the force sensor located inside the housing.

The housing serves the functions of: (a) protecting the controller located therein from compression forces during use, which forces may otherwise damage the controller; (b) protecting the controller from the environment in which the sensor is deployed, e.g. from water and/or other environmental contaminants; and (c) defining an overall shape which resists ejection of the sensor assembly from a rope during use, and which protects the rope from damage by the sensor assembly in use. In order to fulfil these objectives, it is generally necessary that the housing is highly resistant to compression, i.e. is relatively rigid.

However, a rigid housing of this construction may undesirably interfere with sensing of force by the force sensor if the force sensor is located with the controller in the housing. By locating the controller inside the housing, but the force sensor outside of the housing, the controller may be protected by the housing from compression and from environmental conditions, whilst avoiding interfering with force sensing by the force sensor. The force sensor may thereby be exposed directly to force applied to the sensor

I assembly in use. Consequently, the accuracy and reliability of force sensing by the sensor assembly may desirably be improved. The force sensor could, for example, comprise a strain gauge.

The housing should ideally be rigid to thereby protect the internally located controller and maintain desired outer shape for retention within rope. For example, the housing could be formed of a rigid material such as polyether ether ketone (PEEK), carbon-fibre or steel.

In an implementation, the force sensor is attached to the housing. Attachment, i.e. mechanical fixing, of the force sensor to the housing, may advantageously improve the transmission of force between the housing and the force sensor, e.g. deformation of the housing will result in deformation of the force sensor. This may advantageously improve the accuracy of the force sensing. For example, the force sensor could be attached to the housing by an adhesive bond.

In an implementation, the sensor assembly further comprises a coating applied to the housing over the force sensor to seal the force sensor from an environment of the sensor assembly. Locating the force sensor outside of the housing may advantageously reduce interference by the housing with force sensing by the force sensor. However, by locating the force sensor outside the housing the force is then undesirably not protected from environmental conditions, such as water, by the housing, risking damage to the force sensor. The coating seals the force sensor to the housing, thereby reducing the risk of damage occurring to the force sensor, and thereby improving the service-life of the force sensor. The coating should form an air and/or water-resistant seal. The coating could, for example, be over moulded onto the housing having the force sensor pre-attached.

In an implementation, the coating is deformable. The coating may thereby deform to allow transmission of force to the force sensor, and to accommodate deformation of the force sensor under load. In particular, because the coating is applied to the housing, the coating should be deformable to accommodate relative movement between the coating and the housing. For example, the coating could be formed of a rubber material, such as high-density neoprene.

In an implementation, the coating is resiliently deformable. The coating may thus return to its default form when unloaded, thereby maintaining the desired overall shape of the assembly, and so reducing the risk of the sensor assembly being displaced within the rope and/or ejected from the rope in use, and reducing the risk of damage being caused to the rope by the sensor assembly.

In an implementation, the coating attaches the force sensor to the housing. In other words, the coating may perform the dual function of mechanically fixing the force sensor to the housing. This may advantageously improve the connection between the housing and the force sensor, and so reduce the risk of the force sensor become misaligned or detached from the housing in use.

In an implementation, the coating extends around a full circumference of the housing. In other words, the coating may form a complete sleeve to the housing. This may advantageously improve the attachment of the coating to the housing. The coating is thus less likely to become detached from the housing in use, and so the risk of the force sensor being damaged is desirably reduced.

In an implementation, the force sensor comprises a strain gauge. A strain gauge may desirably be relatively mechanically robust and resistant to mechanical damage.

In an implementation, the sensor assembly further comprises an antenna electrically connected to the controller located outside of the housing.

In an implementation, the antenna is attached to the housing.

In an implementation, the antenna is attached to the housing along a full length of the antenna.

In an implementation, the coating is applied over the antenna to seal the antenna from an environment of the sensor assembly.

In an implementation, the coating attaches the antenna to the housing.

In an implementation, the strain gauge extends circumferentially around the housing.

In an implementation, the strain gauge extends around at least a quarter of a circumference of the housing.

In an implementation, the strain gauge extends around at least a half of a circumference of the housing, or at least three-quarters of the circumference of the housing.

In an implementation, the strain gauge is attached to the housing.

In an implementation, the strain gauge is attached to the housing continuously along a full circumferential extent of the strain gauge.

In an implementation, the strain gauge extends around an outer circumference of the housing.

In an implementation, the housing is elongate, the housing comprises a plurality of housing sections extending in length consecutively, and the housing sections are flexibly coupled to facilitate flexing of the housing about a longitudinal axis of the housing.

In an implementation, the housing sections are resiliently flexibly coupled to facilitate resilient flexing of the housing about the longitudinal axis.

In an implementation, each of the plurality of housing sections is rigid. In an implementation, the sensor assembly comprises one or more flexible seals between the plurality of housing sections to seal the controller from an environment of the sensor assembly.

In an implementation, the one or more flexible seals comprises a flexible coating applied over the housing sections to flexibly couple the housing sections.

In an implementation, the controller comprises a first part located in a first of the plurality of housing sections, a second part located in a second of the plurality of housing sections, and flexible electrical conductors electrically coupling the first and second parts.

In an implementation, the controller comprises a magnetic field sensor responsive to an applied magnetic field, and the controller is switchable between a first state of operation and a second state of operation, and the magnetic field sensor is excitable to cause the controller to switch from the first state of operation to the second state of operation in response to an applied magnetic field.

In an implementation, in the first state of operation one or more systems of the controller is in an inoperative state.

In an implementation, the controller comprises a radio receiver for receiving a radio frequency signal, in the first state of operation the radio receiver is in an inoperative state, and in the second state of operation the radio receiver is in an operative state.

According to a second aspect of the present invention, there is provided a sensor assembly for sensing tension in a rope, the sensor assembly comprising a housing, a force sensor arranged for sensing mechanical force applied to the housing, a controller for controlling the force sensor located inside the housing, and an antenna electrically connected to the controller located outside of the housing.

The housing serves the functions of: (a) protecting the controller located therein from compression forces during use, which forces may otherwise damage the controller; (b) protecting the controller from the environment in which the sensor is deployed, e.g. from water and/or other environmental contaminants; and (c) defining an overall shape which resists ejection of the sensor assembly from a rope during use, and which protects the rope from damage by the sensor assembly in use. In order to fulfil these objectives, it is generally necessary that the housing is highly resistant to compression, i.e. has a relatively sturdy, rigid, construction.

However, a housing of this construction may undesirably interfere with reception/transmission of radiofrequency (RF) signals by the antenna, if the antenna is sited with the controller inside the housing, and especially so if the housing is formed of a conductive metal. By locating the controller inside the housing, but the antenna outside of the housing, the controller may be protected by the housing from compression and from environmental conditions, whilst avoiding interfering with RF transmission/reception by the antenna. Consequently, the reliability of RF transmission/reception by the antenna may desirably be improved. The controller may comprise a radio-frequency receiver/transmitter/transceiver coupled to the antenna.

In an implementation, the antenna is attached to the housing. Attachment, i.e. mechanical fixing, of the antenna to the housing, may advantageously reduce the risk of the antenna becoming detached from the sensor assembly in use, and may thereby desirably reduce the risk of damage to the antenna. For example, the antenna could be attached to the housing by an adhesive bond.

In an implementation, the antenna is attached to the housing along a full length of the antenna. This may best support the antenna, thereby reducing the risk of the antenna becoming detached from the sensor assembly in use, and so desirably reducing the risk of damage being caused to the antenna.

In an implementation, the sensor assembly further comprises a coating applied to the housing over the antenna to seal the antenna from an environment of the sensor assembly. Locating the antenna outside of the housing may advantageously reduce interference by the housing with RF transmission/reception by the antenna. However, by locating the antenna outside the housing, the antenna is then undesirably not protected from environmental conditions, such as water, by the housing, risking damage to the antenna. The coating seals the antenna to the housing, thereby reducing the risk of damage occurring to the antenna, and thereby improving the service-life of the antenna. The coating should form an air and/or water-resistant seal. The coating could, for example, be over moulded onto the housing having the antenna pre-attached.

In an implementation, the coating attaches the antenna to the housing. In other words, the coating may perform the dual function of mechanically fixing the antenna to the housing. This may advantageously improve the connection between the housing and the antenna, and so reduce the risk of the antenna become misaligned or detached from the housing in use.

In an implementation, the coating extends around a full circumference of the housing. In other words, the coating may form a complete sleeve to the housing. This may advantageously improve the attachment of the coating to the housing. The coating is thus less likely to become detached from the housing in use, and so the risk of the antenna being damaged is desirably reduced

According to a third aspect of the present invention, there is provided a sensor assembly for sensing tension in a rope, the sensor assembly comprising: a housing, a strain gauge extending circumferentially around the housing for sensing mechanical force applied to the housing, and a controller for controlling the strain gauge located inside the housing.

The housing serves the functions of: (a) protecting the controller located therein from compression forces during use, which forces may otherwise damage the controller; (b) protecting the controller from the environment in which the sensor is deployed, e.g. from water and/or other environmental contaminants; and (c) defining an overall shape which resists ejection of the sensor assembly from a rope during use, and which protects the rope from damage by the sensor assembly in use. In order to fulfil these objectives, it is generally necessary that the housing is highly resistant to compression, i.e. has a relatively sturdy, rigid, construction.

The strain gauge extends circumferentially around the housing. In other words, the electrical conductors of the strain gauge are arranged to run circumferentially around the housing. The strain gauge is thus operable to detect force applied to the housing around the full circumferential extent of the strain gauge. In this arrangement, the strain gauge may desirably be capable of accurately detecting forces applied to the housing from a wide range of directions; in particular, from directions subtended by the circumferential extent of the strain gauge. For example, the strain gauge may be configured to sense deformation of the housing. A strain gauge force sensor is ideally suited to this application, for the reason that it may be readily confirmed to the circumferential profile of the housing.

In contrast, it has been observed that, for example, force sensors, such as strain gauges, that are arranged to extend diametrically with respect to the housing may exhibit relatively highly directional force sensing characteristics, i.e. in this arrangement the responsiveness of the sensor to an applied force would vary significantly in dependence on the direction of application of the force. Thus, in this configuration multiple force sensors may be required to accurately sense forces from a range of different directions. The invention may thus provide improved force sensing.

In an implementation, the strain gauge extends around at least a quarter of a circumference of the housing. In other words, the electrically conductive trace of the strain gauge may extend around at least a quarter of the circumference of the housing. In this configuration, the strain gauge may thus directly sense forces applied to the housing in both the‘X’ and Ύ’ directions.

In an implementation, the strain gauge extends around at least a half of a circumference of the housing, or at least three-quarters of the circumference of the housing. Arranging the strain gauge to extend around a greater proportion of the circumference of the housing may desirably increase the responsiveness of the sensor to forces from a wider range of directions, and thereby improve the accuracy of the force sensing.

In an implementation, the strain gauge is attached to the housing. For example, the strain gauge may be attached to housing by an adhesive bond. The attachment of the strain gauge to the housing may desirably improve the transmission of force therebetween, such that the strain gauge may most effectively sense deformation of the housing under load. In an implementation, the strain gauge is attached to the housing continuously along a full circumferential extent of the strain gauge.

In an implementation, the strain gauge extends around an outside of the housing. The outer circumference of the housing will be relatively greater than the inner circumference. The greater circumference of the outside of the housing may allow for a gentler curvature of the strain gauge, which may desirably reduce fatigue on the strain gauge. In an implementation, the sensor assembly comprises a coating applied to the outside of the housing over the strain gauge to seal the force sensor from an environment of the sensor assembly. Locating the strain gauge outside of the housing may advantageously reduce interference by the housing with force sensing by the strain gauge. However, by locating the strain gauge outside the housing the force is then undesirably not protected from environmental conditions, such as water, by the housing, risking damage to the strain gauge. The coating seals the strain gauge to the housing, thereby reducing the risk of damage occurring to the strain gauge, and thereby improving the service-life of the strain gauge. The coating should form an air and/or water-resistant seal. The coating could, for example, be over moulded onto the housing having the strain gauge pre-attached.

In an implementation, the coating is deformable. The coating may thereby deform to allow transmission of force to the strain gauge, and to accommodate deformation of the strain gauge under load. In particular, because the coating is applied to the housing, the coating should be deformable to accommodate relative movement between the coating and the housing. For example, the coating could be formed of a rubber material, such as high-density neoprene.

In an implementation, the coating is resiliently deformable. The coating may thus return to its default form when unloaded, thereby maintaining the desired overall shape of the assembly, and so reducing the risk of the sensor assembly being displaced within the rope and/or ejected from the rope in use, and reducing the risk of damage being caused to the rope by the sensor assembly.

In an implementation, the coating attaches the strain gauge to the housing. In other words, the coating may perform the dual function of mechanically fixing the strain gauge to the housing. This may advantageously improve the connection between the housing and the strain gauge, and so reduce the risk of the strain gauge become misaligned or detached from the housing in use.

In an implementation, the coating extends around a full circumference of the housing. In other words, the coating may form a complete sleeve to the housing. This may advantageously improve the attachment of the coating to the housing. The coating is thus less likely to become detached from the housing in use, and so the risk of the strain gauge being damaged is desirably reduced.

According to a fourth aspect of the present invention, there is provided a sensor assembly for sensing tension in a rope, the sensor assembly comprising: an elongate housing; a force sensor for sensing mechanical force applied to the housing, and a controller for controlling the force sensor located inside the housing, wherein the housing comprises a plurality of housing sections extending in length consecutively, and the housing sections are flexibly coupled to facilitate flexing of the housing about a longitudinal axis of the housing.

The elongate housing serves the functions of: (a) protecting the controller located therein from compression forces during use, which forces may otherwise damage the controller; (b) protecting the controller from the environment in which the sensor is deployed, e.g. from water and/or other environmental contaminants; and (c) defining an overall shape which resists ejection of the sensor assembly from a rope during use, and which protects the rope from damage by the sensor assembly in use. In this regard, it has been found that in many applications an elongate housing advantageously presents a desirable shape for location within a rope. In order to fulfil these objectives, it is generally necessary that the housing is highly resistant to compression, i.e. is relatively rigid. For example, the housing could be formed of a rigid material such as polyether ether ketone (PEEK), carbon-fibre or steel.

However, a rigid elongate housing may undesirably interfere with bending of the rope, as may occur for example if the rope is wound over a pulley or coiled for storage, risking damage to the sensor housing and/or the rope. By forming the housing of a plurality of flexibly coupled housing sections extending in length consecutively, the housing may flex along its length, thereby reducing the risk of damage to the sensor assembly and/or the rope caused by bending of the rope. In particular, in this construction each of the housing sections may be relatively rigid and resistant to compression, thereby protecting internally located components from compression forces in use, whilst flex between the rigid housing sections may desirably allow the sensor assembly to flex along its length.

In an implementation, the housing sections are resiliently flexibly coupled to facilitate resilient flexing of the housing about the longitudinal axis. The resiliently flexible coupling between housing sections tends to cause the housing to return to its original form when unloaded. This may advantageously reduce the risk of the sensor being displaced within, or ejected from, the rope in use, and may desirably reduce the risk of damage being caused to the rope by a misshapen sensor assembly.

In an implementation, each of the plurality of housing sections is rigid. Rigid housing sections may best resist compression forces exerted thereon by strands of the rope during use, thereby protecting the internally located controlled from damage.

In an implementation, the sensor assembly comprises one or more flexible seals between the plurality of housing sections to seal the controller from an environment of the sensor assembly. The flexible seals may desirably seal the internally located controller from environmental conditions, such as water ingress, through a range of flex between housing sections.

In an implementation, the one or more flexible seals comprises a flexible coating applied over the housing sections to flexibly couple the housing sections. The flexible coating may thus desirably perform the dual purposes of mechanically coupling the housing sections in addition to sealing between adjacent housing sections.

In an implementation, the controller comprises a first part located in a first of the plurality of housing sections, a second part located in a second of the plurality of housing sections, and flexible electrical conductors electrically coupling the first and second parts. According to a fifth aspect of the present invention, there is provided a sensor assembly for sensing tension in a rope, the sensor assembly comprising: a housing; a force sensor for sensing mechanical force applied to the housing, and a controller for controlling the force sensor located inside of the housing, the controller comprising a magnetic field sensor responsive to an applied magnetic field, wherein the controller is switchable between a first state of operation and a second state of operation, and the magnetic field sensor is excitable to cause the controller to switch from the first state of operation to the second state of operation in response to an applied magnetic field.

The controller may undesirably have a (relatively) high power consumption in an active state, and during periods of time when the sensor assembly is not in use, which may be long periods of time in the case of applications such as ropes for mooring boats, the controller may unnecessarily consume power. This is particularly problematic where the controller is powered by an onboard battery, which may be unduly depleted by powering of the sensor assembly when not in use.

The controller is switchable between the first and second states of operation. For example, in the first state of operation the controller could be powered-down, either partially or fully to conserve electrical power, and in the second state of operation the controller could be powered-up to facilitate control of the force sensor and wireless communication with remote equipment.

It may be desirable in the first state to fully power down hardware used for operating the sensor assembly, such as an RF receiver/transceiver. However, in the event that the wireless receiver/transceiver is powered-down, remote powering-up of the sensor assembly via a RF signal is not possible.

In the invention however, the magnetic field sensor may be excited by an applied magnetic field to cause the controller to switch to the second state of operation, which could for example be a powered-on state. In particular, using the magnetic field sensor, and a corresponding magnetic field generator, the state of the sensor assembly may be readily switched without requiring removal of the sensor assembly from the rope and/or disassembly of the sensor assembly, thereby reducing the time cost incurred in switching the state of the sensor assembly. The system could further comprise a magnetic field generator for exciting the magnetic field sensor.

In an implementation, in the first state of operation one or more systems of the controller is in an inoperative state. In other words, in the first state, some or all function of the controller may be powered- down to conserve power.

In an implementation, the controller comprises a radio receiver for receiving a radio frequency signal, in the first state of operation the radio receiver is in an inoperative state, and in the second state of operation the radio receiver is in an operative state. In other words, in the first state of operation the radio receiver may be powered-down, to thereby conserve power. According to a sixth aspect of the present invention, there is provided a sensor system comprising a sensor assembly according to the fifth aspect of the invention, and a magnetic field generator operable to generate a magnetic field to excite the magnetic field sensor.

According to a seventh aspect of the present invention, there is provided a tethering assembly for tethering an object, comprising: a rope, and a sensor assembly as defined in any one of the preceding statements located within the rope for sensing mechanical force applied to the housing by the rope.

According to an eighth aspect of the present invention, there is provided a method of sensing tension in a rope, comprising: obtaining a sensor assembly as defined in any one of the preceding statements, locating the sensor assembly within the rope, and operating the sensor assembly to sense tension in the rope.

These and other aspects of the invention will be apparent from the embodiment(s) described below.

Brief Description of the Drawings

In order that the present invention may be more readily understood, embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure I shows illustratively an example of a tethering assembly including a rope for tethering an object, embodying an aspect of the present. The tethering assembly comprises a sensor system for sensing tension in the rope, comprising a sensor assembly located within the rope and a remote computer in communication with the sensor assembly via a wireless communication network;

Figure 2 shows illustratively a sensor assembly of the sensor system, identified with reference to Figure I , located within the rope;

Figure 3 shows schematically the sensor assembly identified with reference to Figure 2 in a side cross- sectional view;

Figure 4 shows schematically computing hardware of the sensor assembly;

Figure 5 shows schematically computing hardware of the remote computer;

Figure 6 shows processes of a method for sensing tension in the rope using the sensor system, which includes a process of powering-on the sensor assembly using a magnetic field generator;

Figure 7 shows illustratively the process of powering-on the sensor assembly using the magnetic field generator;

Figure 8 shows schematically computing hardware of the magnetic field generator; and Figure 9 shows schematically an alternative sensor assembly of the sensor system.

Detailed Description of the Disclosure

Referring firstly to Figure I , a tethering assembly 101 embodying an aspect of the invention, comprises a rope 102 for tethering an object, and a sensor system, indicated generally at 103, for sensing tension in the rope 102. In the example, the tethering assembly 101 is deployed for mooring a boat 104 to a dock 105.

Rope 102 comprises a plurality of intertwined strands of polyester forming a flexible line.

Sensor system 103 comprises a sensor assembly, indicated generally at 106, located within the rope 102 for measuring tension in the rope, and a remote computer 107, in communication with the sensor assembly 106 via a wireless telecommunication network to facilitate data exchange therebetween.

Referring in particular to Figure 2, the sensor assembly 106 is located within the rope 102, approximately centrally with respect to the width of the rope. The sensor assembly 106 is thus located between strands of the rope, such as strands 201 , 202, and is retained in place in use within the rope by the strands.

As illustrated in the Figure, the strands 201 , 202 of the rope 102 are displaced radially outwardly from a centreline of the rope by the location of the sensor assembly 106. Tension exerted along the length of the rope causes the strands 201 , 202 of the rope to be drawn inwardly against the sensor assembly 106, thereby exerting a compressive, i.e. a radially inward, force on the sensor assembly 106. Consequently, tension on the rope 102 may be inferred by the sensor assembly 106 through measurement of the compressive force exerted on the sensor assembly by the strands 201 , 202 of the rope.

Referring next in particular to Figure 3, the sensor assembly 106 comprises a housing 301 , a force sensor 302, a controller, indicated generally at 304, for controlling the force sensor 302, an antenna 305, and a coating 306 applied to the housing 301.

Housing 301 is elongate and generally cylindrical in form with closed ends, and bounds an internal volume 307 for location of components of the sensor assembly. In the example, housing 301 comprises domed end-caps 308, 309 covering the end walls of the housing, which are releasably attached to the remainder of housing to facilitate access to the end walls of the housing.

A primary function of the housing 301 is to protect components of the sensor assembly located in the volume 307, e.g. the controller 304, from compression by strands of the rope 102 during use of the sensor assembly. The housing 301 is thus relatively rigid so as to be highly resistant to compression to thereby protect the internally located components. In the example, the housing 301 is formed from a rigid plastic material, specifically, Polyether ether ketone (PEEK). The housing 301 could instead be constructed from an alternative rigid material, for example, from carbon-fibre, or a metal such as steel. Although the housing 301 is constructed to be highly resistant to compression, it is intended that the housing should be slightly elastically deformable under an applied load.

A secondary function of the housing 301 is to define an overall outer shape of the sensor assembly 106 which: (a) facilitates convenient location of the sensor assembly within a rope; (b) is shaped to minimise abrasion between the sensor assembly and the rope in use, thereby minimising damage to either the sensor assembly or the rope; and (c) that is best retained within the rope during use and is resistant to displacement within the rope and/or ejection from the rope in use. These further objectives also require that the housing 301 is relatively rigid in order that the housing is not excessively deformed in use, such that the intended shape of the housing 301 is approximately maintained in use.

Force sensor 302 is located outside of the housing 301 , and is attached to an outer surface of the cylindrical side wall of the housing 301 by an adhesive. In the example, force sensor 302 is a strain gauge, comprising a convoluted electrically conductive trace. The strain gauge 302 is arranged such that runs of the conductive trace extend circumferentially around almost the full circumference of the cylindrical side wall of the housing 301 .

Because the strain gauge 302 is attached to the cylindrical side wall of the housing 301 , radial deformation of the housing 301 , as may be expected to occur in consequence of compressive, i.e. radially inward, forces applied to the sensor assembly by strands of the rope when tensioned, will correspondingly deform the strain gauge 302, by stretching or compressing the conductive trace of the strain gauge. The electrical resistance of the conductive trace of the strain gauge may thereby be varied by compressive force applied to the housing by strands of the rope in use. By measurement of the electrical resistance of the strain gauge 302, compared to a reference unloaded value, the compressive force exerted on the sensor assembly 106 by the strands of the rope may be measured, from which the tension along the length of the rope, may be inferred.

Controller 304 is located inside the internal volume 307 of the housing 301 . The controller 304 is connected to the strain gauge 302 by conductors which extend from the strain gauge through apertures in the side wall of the housing 301 . The strain gauge 302 is controllable by the controller 304 to measure force exerted on the strain gauge. Controller 304 comprise an input/output port 3 10 located in the end wall of the housing 301 , which is accessible by removable of the detachable end-cap 309.

Antenna 305 is located outside of the housing 301 , and is attached to the outer surface of the cylindrical side wall of the housing 301 by an adhesive. In the example, antenna 305 is a monopole antenna, and is arranged such that the conductor of the antenna runs in length along the length of the elongate housing 301 . Similarly to strain gauge 302, antenna 305 is connected to the controller 304 by conductors which extend from the antenna through apertures in the side wall of the housing 301 .

Coating 306 is disposed around the full circumference of the side wall of the housing 301 , over the strain gauge 302 and the antenna 305. The coating 306 thus forms a generally cylindrical sleeve about the housing 301 , the strain gauge 302, and the antenna 305, sealing the strain gauge 302 and the antenna 305 against the housing 301 . Coating 306 is formed of a resiliently compressible rubberised material, in the example, a synthetic rubber material. Coating 306 is applied to the housing 301 during manufacture by over moulding of the coating 306 onto the housing 301 , with the strain gauge 302 and antenna 305 pre-attached to the housing 301 . The coating 306 thereby encapsulates the strain gauge 302 and antenna 305 against the housing 301 . Because the coating 306 is resiliently deformable, the coating 306 is able to accommodate deformation of the housing 301 and the strain gauge 302 during use.

A primary function of the coating 306 is to seal the strain gauge 302 and antenna 305 from the environment in which the sensor assembly is employed, to thereby prevent chemical degradation of the strain gauge 302 and/or the antenna 305 by water or other environmental contaminants.

A further function of the coating 306 is to provide mechanical protection to the strain gauge 302 and the antenna 305, especially to protect the strain gauge and antenna from shear, i.e. abrasion, forces, which may otherwise damage the strain gauge 302 and the antenna 305, or cause the strain gauge and/or the antenna to become detached from the housing 301 .

A further function of the coating 306 is to improve the attachment of the strain gauge 302 and the antenna 305 to the housing 301 , for the reason that the coating 306 serves to further secure the strain gauge and antenna in place.

A further function of the coating 306 is to define a desired overall shape of the sensor assembly, in the example, a prolate spheroid shape, to best resist displacement/ejection of the sensor assembly from the rope, and to minimise mechanical damage to the sensor assembly 106 and rope 102, during use of the sensor assembly to sense tension in the rope. In this regard, it will be appreciated that the deformable rubber-type material from which the coating 306 is formed may advantageously be more easily shaped to the desired shape than the rigid material from which the housing 301 is formed.

Referring next in particular to Figure 4, the controller 304 comprises central processing unit 401 , memory 402, transceiver 403, magnetic field sensor 404, battery 405, and input/output interface 406.

Central processing unit 401 is configured for execution of commands received from the remote computer 107, for processing of sensor data received from the strain gauge 302, and for overall control of the other hardware of the controller, including transceiver 403. Memory 402 is configured as read/write memory for non-volatile storage of sensor data received from strain gauge 302. Transceiver 403 is provided for wireless communication with the remote computer 107 via the wireless telecommunication network. Magnetic field sensor 404 is configured to act as a switch for controlling the operation of the central processing unit 401 , and is operable to cause the controller 304 to switch from a powered-down state to a powered-up state in response to an applied magnetic field, as will be described in further detail with particular reference to Figures 7 and 8. In the example, the magnetic field sensor 404 comprises a microelectromechanical systems (MEMS) sensor. Battery 405 is provided for supplying electrical power to electrical consumers of the controller 304, such as the central processing unit 401 and the transceiver 403, and for supplying electrical power to the strain gauge 302. The input/output interface 406 is provided for connection of peripheral devices to the controller 304. In particular, input/output interface 406 supports input/output port 3 10, which is a Universal Serial Bus (USB) connection, operable for upload and download of data from memory 402, and for charging of battery 405. The components 401 to 406 of the controller 304 are in communication via system bus 407.

Referring next in particular to Figure 5, remote computer 107 comprises similar hardware components to controller 304, and like components are identified in the Figure by like reference numerals.

Thus, similarly to controller 304, remote computer 107 comprises central processing unit 401’, memory 402’, transceiver 403’, input/output interface 406’, and system bus 407’. Unlike controller 304, remote computer 107 comprises a power supply 501 for connection to a source of mains electrical power, in place of the battery 405 of controller 304. Remote computer 107 communicates with controller 304 using transceiver 403’ via the wireless communication network. Thus, remote computer 107 may issue commands to controller 304 to cause controller 304 to operate the strain gauge 302 to collect sensor data relating to tension in the rope 102, and to cause controller 304 to return the sensor data to the remote computer 107. Sensor data returned to the remote computer 107 may subsequently be processed by central processing unit 401’, and/or output to an operator of the remote computer 107, for example, by outputting the processed sensor data in a visual format via an electronic display connected to input/output interface 406’.

Referring next to Figure 6, a method of using the sensor system 103 disclosed herein to sense tension in a rope comprises eight stages.

At stage 601 , a sensor assembly 106 as depicted in Figure 3 is obtained.

At stage 602, the sensor assembly 106 is located within the rope for which tension is to be sensed, e.g. rope 102. For example, the sensor assembly may be manually manipulated into the rope by locally separating strands of the rope to create an opening, and inserting the sensor assembly into the opening so as to be retained between strands of the rope approximately centrally with respect to the width of the rope.

At stage 603, the sensor assembly is powered-up. In an example, the sensor assembly 106 is powered-up, i.e. turned on, by application of a local magnetic field to the sensor assembly 106 to excite the magnetic field sensor 404 and cause the magnetic field sensor 404 to switch the sensor assembly to an active state.

At stage 604, the remote computer 107 issues a command, via the wireless communication network, to cause the sensor assembly 106 to sense force exerted on the sensor assembly by the strands of the rope and return the sensor data to the remote computer. For example, the remote computer 107 may issue such a command in response to a human input via a human-machine interface connected to the input/output interface 406’ of the remote computer. As an exemplary alternative, the command issued by the remote computer could be prompted by a computer program running on central processing unit 401’ of remote computer 107.

At stage 605, in response to the command issued at stage 604, the controller 304 of the sensor assembly 106 passes an electrical current through the strain gauge 302, and measures the electrical resistance of the strain gauge. The controller 304 then performs preliminary processing of the sensor data, i.e. the electrical resistance data, using the central processing unit 401 of the controller.

At stage 606, the controller 304 of the sensor assembly transmits the sensor data obtained at stage 605 to the remote computer 107 via the wireless communication network.

At stage 607, the remote computer 107 further processes the sensor data returned by the sensor assembly 106 at stage 606 to infer the tension on the rope. The remote computer may, for example, output the sensor data to a human operator of the remote computer 107 in real-time, thereby allowing the operator to understand the tension in the rope in real time. Alternatively, and/or additionally, the remote computer 107 may store the processed sensor data in memory 402’, to thereby record the load history of the rope for retrieval by an operator at a later time.

At stage 608, the sensor assembly 106 is powered-down to conserve the state of charge of battery 405 during a period of non-use. For example, the power-down operation could be performed in response to a command received from the remote computer 107 indicating an end of a force sensing session. As an exemplary alternative, the sensor assembly 106 could be internally programmed to power-down following a period of non-use exceeding a threshold period of time.

The powered-down state of the sensor assembly, entered at stage 608, could involve a partial shut-down of electrical consumers of the sensor assembly, such that the sensor assembly is placed in a low-power ‘sleep’ state, in which some components of the sensor assembly remain powered. For example, the powered-down state could involve powering-down the strain gauge 302, whilst maintaining sufficient functionality of the central processing unit 401 and transceiver 403 to allow the sensor assembly to receive and act on future power-up commands issued by the remote computer 107 via the wireless communication network. Such a partially powered-down state has the advantage that battery consumption is reduced, whilst remote powering-on of the sensor assembly 106 by the remote computer 107 remains possible.

Alternatively, the powered-down state of the sensor assembly could involve a full power-down of all electrical consumers of the sensor assembly 106, including the central-processing unit 401 and the transceiver 403. Such a fully powered-down state has the advantage that power-consumption during periods of non-use of the sensor assembly is near-eliminated, and thus the operational life of the sensor assembly before recharging of the battery 405 is required may desirably be extended. A disadvantage however of a fully powered-down state of the sensor assembly 106 is that the sensor assembly may not be remotely powered-up by a command issued by remote computer 107 via the wireless communication network.

Referring next to Figures 7 and 8 collectively, the sensor system 103 further comprises a portable magnetic field generator device 701 .

Magnetic field generator device 701 is operable to generate a magnetic field, for example, in response to an operator pressing a button on the device 701 . The magnetic field generator device 701 may thus be used for exciting the magnetic field sensor 404 of the controller 304 of sensor assembly 106, to thereby cause the controller 304 to switch from a powered-down, inoperative, state to a powered-up, operative, state. The magnetic field sensor device 404 of the controller 304 may be an electrically passive device, i.e. a device which does not require electrical power for operation. Thus, magnetic field sensor 404 of the controller 304 and magnetic field generator device 701 may be used for non-intrusively powering-up the sensor assembly even from a fully powered-down state of the sensor assembly.

Magnetic field generator device 701 comprises central processing unit 801 , magnetic field generator 802, battery 803, input/output interface 804, and system bus 805. Central processing unit 801 is operable to control magnetic field generator 802. Magnetic field generator 802, which in the example is an electromagnet, is operable by an applied electric current to generate a magnetic field. Battery 803 is provided to supply electrical power to the central processing unit 801 and to the magnetic field generator 802. Input/output interface 804 is provided for connection of peripheral devices, for example, a human- machine interface, such as a trigger button. The components 801 to 804 of the device 701 communicate via system bus 805.

Referring in particular to Figure 7, given the relatively short-range nature of a magnetic field, a method of powering-up the sensor assembly 106, located in-situ in rope 102, from a fully powered-down state, may involve an operative placing the magnetic field generator device 701 in the immediate vicinity of the sensor assembly 106, for example, within approximately 30 centimetre of the sensor assembly, and operating the magnetic field generator 802 to excite the magnetic field sensor 404 of the controller 304.

Referring finally to Figure 9, in an alternative embodiment of the sensor assembly 106’, in substitute of the unitary housing 301 of the sensor assembly 106, the housing of sensor assembly 106’ comprises a plurality of separate housing sections, in the example, three housing sections 901 , 902 and 903. Many features of the construction of sensor assembly 106’ are similar to features of sensor assembly 106, and like features are denoted in the Figure by like reference numerals.

Similarly to housing 301 of sensor assembly 106, housing sections 901 , 902 and 903 of sensor assembly 106’ are generally cylindrical in shape, and are formed of a rigid material, such as PEEK. Each of the housing sections 901 to 903 defines an internal volume circumferentially surrounded by the wall of the respective housing section. Coating 306’, is applied over the housing sections 901 to 903, for example, by over moulding, forming a unitary sleeve-like structure which flexibly couples the housing sections consecutively in length. Accordingly, the housing sections 901 to 903 are retained together by the coating 306’, but a degree of flexibility about a longitudinal axis of the sensor assembly is permitted at the junctions between the housing sections. This flexibility of the housing of the sensor assembly 106’ may advantageously accommodate bending of the rope 102 in which the sensor assembly is located.

Like sensor assembly 106, sensor assembly 106’ comprises a controller, for controlling the strain gauge 302’. The controller of sensor assembly 106’ is formed by three distinct modules 904, 905, 906. In the example, module 904 comprises a battery 405’, module 905 a central processing unit 40 G, memory 402’, and a magnetic field sensor 404’, and module 906 a transceiver 403’ and an input/output interface 406’. The modules 904 to 906 are located within the housing sections 901 to 903 respectively, and are electrically connected by flexible conductors 907, 908. The construction of sensor assembly 106’, and in particular the flexible coupling of the plural housing sections 901 to 903, may advantageously allow for flexing of the sensor assembly 106’ about the longitudinal axis, such as may occur if the section of rope 102 in which sensor assembly 106’ is located were coiled or wound about a pulley. This flexing of the sensor assembly 106’ may desirably reduce the risk of damage being caused to the sensor assembly and/or the rope by bending of the rope, and further may reduce interference with bending of the rope by the sensor assembly.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.Jn the claims, the word“comprising” does not exclude other elements or steps, and the indefinite article“a” or“an” does not exclude a plurality.