Description:FIELD OF THE INVENTION

[0001] The present invention relates to a sensor assembly. More particularly, the present invention relates to a sensor assembly for measuring a change in a stress on a cable.
BACKGROUND
[0002] Several sensing and measuring devices are known in the state of the art for measuring a stress on a cable. In the state of the art devices, the sensor and the cable are exposed to the environment. Moreover, with the available devices, measuring the stress on cables with diameters less than a certain value, say 0.5 mm, is not feasible. These devices have less sensitivity and hence fail to record small changes in the stress applied. In addition to poor sensitivity, these devices also have a low resolution.
[0003] Furthermore, these sensors may only be used for measuring stresses higher than a certain value and cannot be used to measure stresses lower than that value or the measurements are not accurate enough for many purposes. The state of the art cable tension sensors can measure only an increase in the tensile stress on a cable which implies that the state of the art sensors are not capable of measuring a decrease in the tensile stress, from a pre-existing tensile stress on a cable. Still further, the pre-existing tensile stress on a cable may vary over time and the sensors used in existing system are incapable of detecting or measuring or both, such minor variations in the tensile stress.
[0004] One such prior art discloses increased structural monitoring systems that have sensitive continuous coaxial cable sensors. A preferred embodiment sensor cable of the invention includes an inner conductor, a dielectric jacket, and an outer conductor that is configured to passively deform responsively to strain in an associated structure. The deformation can be aided by the physical structure of the dielectric jacket, the outer conductor, or a combination of both. The deformation translates strain into a measurable change in a reflection coefficient associated with the outer conductor. This prior art sensor is not capable of adjusting the change in magnitude of stress on the cable which may occur due to repeated application of stress on the cable and certain other conditions.
[0005] Therefore, in view of the problems mentioned above, it is advantageous to provide a sensor assembly that may overcome one or more of the problems and limitations mentioned above.
SUMMARY

[0006] This summary is provided to introduce a selection of concepts, in a simplified form, that are further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention nor is it intended for determining the scope of the invention.
[0007] To overcome or at least mitigate one of the problems mentioned above in the state of the art, a sensor assembly with a strain sensor with a high sensitivity, for detecting slight changes in a load acting on a cable g is needed.
[0008] In an embodiment of the present invention, a sensor assembly for measuring a change in magnitude in a tensile stress on a cable is disclosed. The sensor assembly includes a curved leaf spring and a strain sensor. A first end of the leaf spring is affixed to a planar surface such that a second end of the leaf spring is in a slidable contact with the planar surface. The strain sensor is mounted to one of the surfaces (such as the inner surface as per one embodiment) of the leaf spring for sensing a deformation of the leaf spring, caused by a change in magnitude in the tensile stress on the cable. The term “inner” is used herein to describe the concave surface of the curved leaf spring. Conversely the outer surface of the curved leaf spring may be referred to as the convex surface of the curved leaf spring. Further, for the sake of brevity, the term curved may be dropped from the term curved leaf spring and just the term leaf spring may be used, and these terms may be used interchangeably.
[0009] To further clarify the advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[00010] These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
[00011] Figure 1A illustrates a drawing of a sensor assembly configured for measuring a change in a tensile stress on a cable, according to an embodiment of the present invention;
[00012] Figure 1B illustrates a deformation of a leaf spring under different loading conditions, according to an embodiment of the present invention;
[00013] Figure 2A illustrates a plan view and a longitudinal-sectional view of the sensor assembly, according to an embodiment of the present invention;
[00014] Figure 2B illustrates a simulated longitudinal sectional view of the sensor assembly, according to an embodiment of the present invention;
[00015] Figure 3 illustrates an exploded view of the sensor assembly, according to an embodiment of the present invention;
[00016] Figure 4 illustrates three drawings and a simulated view of the flange used in the sensor assembly, according to an embodiment of the present invention;
[00017] Figure 5 illustrates an isometric view, a side view, and a simulated view of a spacer used in the sensor assembly, clockwise from top left, according to an embodiment of the present invention;
[00018] Figure 6 illustrates an isometric view, a plan view and a simulated view of a housing used in the sensor assembly, clockwise from top left, according to an embodiment of the present invention; and
[00019] Figure 7 illustrates a plan view, an isometric view, and a simulated view of a leaf spring, clockwise from top left, according to an embodiment of the present invention.
[00020] Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have necessarily been drawn to scale. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
DETAILED DESCRIPTION OF FIGURES
[00021] For the purpose of promoting an understanding of the principles of the present invention, reference will now be made to the various embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the present invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the present invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the present invention relates.
[00022] It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the present invention and are not intended to be restrictive thereof.
[00023] Whether or not a certain feature or element was limited to being used only once, it may still be referred to as “one or more features” or “one or more elements” or “at least one feature” or “at least one element.” Furthermore, the use of the terms “one or more” or “at least one” feature or element do not preclude there being none of that feature or element, unless otherwise specified by limiting language including, but not limited to, “there needs to be one or more…” or “one or more elements is required.”
[00024] Reference is made herein to some “embodiments.” It should be understood that an embodiment is an example of a possible implementation of any features and/or elements of the present invention. Some embodiments have been described for the purpose of explaining one or more of the potential ways in which the specific features and/or elements of the proposed invention fulfil the requirements of uniqueness, utility, and non-obviousness.
[00025] Use of the phrases and/or terms including, but not limited to, “a first embodiment,” “a further embodiment,” “an alternate embodiment,” “one embodiment,” “an embodiment,” “multiple embodiments,” “some embodiments,” “other embodiments,” “further embodiment”, “furthermore embodiment”, “additional embodiment” or other variants thereof do not necessarily refer to the same embodiments. Unless otherwise specified, one or more particular features and/or elements described in connection with one or more embodiments may be found in one embodiment, or may be found in more than one embodiment, or may be found in all embodiments, or may be found in no embodiments. Although one or more features and/or elements may be described herein in the context of only a single embodiment, or in the context of more than one embodiment, or in the context of all embodiments, the features and/or elements may instead be provided separately or in any appropriate combination or not at all. Conversely, any features and/or elements described in the context of separate embodiments may alternatively be realized as existing together in the context of a single embodiment.
[00026] Any particular and all details set forth herein are used in the context of some embodiments and therefore should not necessarily be taken as limiting factors to the proposed invention.
[00027] The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by “comprises... a” does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.
[00028] Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[00029] For the sake of clarity, the first digit of a reference numeral of each component of the present invention is indicative of the Figure number, in which the corresponding component is shown. For example, reference numerals starting with digit “1” are shown at least in Figure 1. Similarly, reference numerals starting with digit “2” are shown at least in Figure 2.
[00030] Figure 1A illustrates a drawing of sensor assembly (100) configured for measuring a change in stress on a cable (102), according to an embodiment of the present invention. In particular, Figure 1 illustrates the cable (102), a leaf spring (104), a first end (110) and a second end (106) of the leaf spring (104), a planar surface (108), a slidable contact (112) between the second end (106) and the planar surface (108), a strain sensor (114), a housing (116), a spacer (118) and a flange (120). Figure 1B illustrates a deformation of the leaf spring (104) under different conditions of stress on the cable, according to an embodiment of the present invention. In particular, Figure 1B illustrates the contour of the leaf spring (104) under a no-load condition (105), that is, no tensile stress on the cable, a pre-load condition (115) and a fully loaded condition (125).
[00031] The sensor assembly (100) as shown in Figure 1A is implemented for measuring a change in magnitude in a tensile stress on the cable (102). The sensor assembly (100) is a tension sensing module configured for measuring the application of tension on the cable (102). Using the principles disclosed herein and varying one or more dimensions of the components of the disclosed assembly, assemblies for measuring stresses of different ranges of stress and for cables of different dimensions may be realized in practice by a person skilled in the art. All such variations must be deemed as laboratory variations of the disclosed assembly and that they are embodiments of the same innovative concepts disclosed herein. In one embodiment, the cable (102) in the measuring area within the housing (116) may be completely sealed with a cover.
[00032] The sensor assembly (100) includes the leaf spring (104). The first end (110) of the leaf spring (104) is affixed to a planar surface (108) while the second end (106) of the leaf spring (104) is in slidable contact (112) with the planar surface (108). The slidable contact (112) surface may be lubricated. The leaf spring (104) is in the shape of an arc of a predefined curve selected from a set of curves, but not limited to, a circle, an ellipse, a parabola, a hyperbola, a part of a French curve, and a catenary. The leaf spring (104) is preferably made of stainless spring steel. For certain applications, materials such as Phosphor Bronze and the like may also be used by a person skilled in the art. All such variations in the materials used must be deemed as laboratory variations of the disclosed assembly and that they are embodiments of the same innovative concepts disclosed herein.
[00033] The sensor assembly (100) includes the strain sensor (114), mounted to an inner surface of the leaf spring (104) for sensing a deformation of the leaf spring (104), caused by a change in magnitude in the tensile stress on the cable (102). The strain sensor (114) is affixed to an inner surface of the arc of the leaf spring (104), substantially at a center of the length of the arc. It may also be possible to attach the sensor to the outer convex surface of the leaf spring, in one execution.
[00034] Now a brief description of the working of the disclosed sensor assembly is provided. The leaf spring (104) does not experience any stress, in the absence of any load on it. When the cable (102) is resting on the leaf spring (104), the leaf spring (104) may experience an initial stress based on an actual stress on the cable (102). This results in an initial deformation of the leaf spring and the strain sensor (114) senses the initial stress on the leaf spring (104). This deformation may also be referred to as a flattening of the leaf spring. The output of the strain sensor (114) may be measured. For further measurements, this initial measured value is set as zero which is then considered as a reference value. When the cable (102) is stretched or, in other words, more tensile stress is applied on the cable (102), the cable (102) tends to become straighter and pushes the leaf spring (104) further down, thus causing a greater deformation of the leaf spring (104). The magnitude of the deformation in the leaf spring (104) is sensed by the strain sensor (114).
[00035] The strain sensor may be chosen from a set of strain sensors comprising, but not limited to, a strain gauge, a piezoelectric transducer, a force sensing resistor, an optical sensor, a fibre Bragg grating sensor, a proximity sensor, and a deflection gauge. The measured value is used as a measure of the stress acting on the cable (102). When calibrated against a standard or reference strain sensor the disclosed sensor functions as a stress sensor.
[00036] The sensor assembly (100) is encapsulated in a metallic housing (116). The housing (116) includes orifices for receiving cable (102), one or more of a spacer (118) and a flange (120) for restraining an outer sheath of the cable (102) outside the housing (116), and a cover (122), as shown in Figure 3, for encapsulating the sensor assembly (100) within the housing (116).
[00037] The housing (116) includes an orifice (628), as shown in Figure 6, for one or more wires from the strain sensor (114) to be brought out of the housing (116). The orifice (628) is sealed, once the wires are brought out, for protecting the parts within the housing (116) from external environment.
[00038] The sensor assembly (100) as disclosed herein may be implemented in a combined braking system (CBS), also called linked braking system (LBS) which is a system for linking front and rear brake levers on a vehicle, in accordance with an embodiment of the present invention.
[00039] The vehicle, as meant in this invention, may be an electric vehicle. An electric vehicle (EV) or a battery powered vehicle including, and not limited to two-wheelers such as scooters, mopeds, motorbikes, or motorcycles; three-wheelers such as auto-rickshaws, primarily work on the principle of driving an electric motor using the power from the batteries provided in the EV. Furthermore, the electric vehicle may have at least one wheel which is electrically powered to traverse such a vehicle. The term ‘wheel’ may be referred to any ground-engaging member which allows traversal of the electric vehicle over a path. The types of EVs include Battery Electric Vehicle (BEV), Hybrid Electric Vehicle (HEV) and Range Extended Electric Vehicle. However, the subsequent paragraphs pertain to the different elements of a Battery Electric Vehicle (BEV).
[00040] Most commonly, the brake on the rear wheel is operated by the left hand of the rider and the brake on the front wheel is operated by the right hand of the rider. Thus, the term left brake lever and right brake lever or left brake and right brake may also be used hereinafter and refer to the operation of the brakes on the rear wheel and the front wheel respectively.
[00041] In one example, the front brake lever and the rear brake lever of the vehicle are interconnected through a CBS cable. In one embodiment, this CBS cable may be the cable (102) as disclosed herein. It is necessary to determine which brake lever (the right or the left) the rider riding the vehicle is applying. Further, it is also necessary to determine the extent i.e., a measure of the displacement of the brake lever on the application of each of the brakes. In order to determine both the above, an electronic signal is needed that may be provided as an input to a controller in the vehicle. This signal is obtained from the sensor assembly (100) as disclosed herein.
[00042] The static preloading on the strain sensor (114) is explained in detail below. In one embodiment, the tensile stress on the cable (102) is set to a predefined percentage of the maximum tensile stress experienced by the cable (102). In one example, the leaf spring (104) may be used to measure both the actuation of the right lever and left lever. The condition where the right lever is fully actuated corresponds to the no-load condition (105) and when the left lever is fully actuated, without the right lever being operated, corresponds to the fully loaded condition (125) as shown in Figure 1B. In order to achieve this, the cable (102) needs to be preloaded as shown in Figure 1B wherein the leaf spring assumes the contour (115). The cable (102) may be preloaded using an element such as, but not limited to, a nut provided in the CBS system. By turning the nut, the preload on the CBS cable may be set to various values. In one embodiment, the preloading on the cable (102) is forty percent of the capacity of the strain sensor (114) employed in the disclosed sensor assembly (100). The pre-loading may be varied based on the required sensing range for the front brake lever when compared to the rear brake lever.
[00043] If there is a breakage in the cable (102), the deformation of the leaf spring tends to disappear as the cable (102) becomes completely loose and the output value of the strain sensor (114) reaches its minimum value, and the controller senses it as a break in the cable.
[00044] The leaf spring is preloaded using a nut provided in the right brake assembly. The more that the nut is turned in one direction, such as clockwise, the more is the tensile stress applied on the cable (102) thereby preloading the leaf spring. Thus, when the left brake is applied, the cable (102) is stretched (or is under higher stress) which causes the leaf spring (104) to be stressed more than the preloaded condition (115).
[00045] The magnitude of stress on the cable (102) is proportional to the magnitude of movement of the brake lever, let us say the left brake lever. The stress on the cable deforms the leaf spring (104) and the sensing element is hence under stress, which gives an output based on the magnitude of the stress on the sensing element. Similarly, when the right brake is applied, due to the CBS mechanism, as described hitherto, the stress on the cable (102) decreased thereby causing the deformation of in the leaf spring (104) to be reduced which has been preloaded. The magnitude of reduction in stress from the preloaded stress is proportional to the magnitude of the movement of the right brake lever. The strain sensor (114) now experiences less stress which is opposite of when the left brake is applied.
[00046] Thus, the system is configured to determine which lever is pressed and the magnitude of the displacement of the brake lever. The magnitude of the displacement of the brake lever may be accurately calculated and then used to control the regenerative braking function and regenerative torque provided by the braking system. The measured value is correlated to the stress applied on the levers and subsequently on the cable (102).
[00047] The dynamic preloading (115) of the strain sensor (114) is explained in detail below. In one example, a system may be implemented on a vehicle, in accordance with an embodiment of the present invention. The vehicle may be an electric vehicle. The system includes the sensor assembly (100) and a controller. The controller is configured for receiving the sensor signal when the controller is commanded for operation. This value may be referred to as the initial sensor signal value. The then the controller sets initial sensor signal value as a reference value of the tensile stress on the cable (102). In one example, the reference value may be set as zero. The command to the controller may be an act of turning the vehicle’s power switch on for riding. The controller is configured for determining a change in the magnitude of the sensor signal, with reference to the initial sensor signal value as a measure of the change in the tensile stress on the cable (102). The direction of change in the value of the sensor signal and the magnitude of change in value of the sensor signal from the base value are used as an indication of a source of the change and the magnitude of the change in the tensile stress on the cable (102), respectively. In turn, the magnitude of change is used as a measure of the magnitude of displacement of the brake lever. In one example, the source as mentioned herein may be a left brake assembly or a right brake assembly in a vehicle (for example an electric vehicle). That is to say, the controller is configured to determine which of the brake levers, the left one or the right one, has been operated and by how much.
[00048] The disclosed sensor assembly (100) is a compact assembly. The strain sensor (114) used in the sensor assembly (100) may be made sensitive for detecting even slight changes in a stress acting on the cable (102) by being used along with leaf spring (104) in the disclosed assembly (100). Given the type of stainless spring steel, for example, the thickness of the sheet from which the leaf spring is formed determines the sensitivity of the sensor assembly (100)
[00049] Figure 2A illustrates a plan view (200A) and a longitudinal-sectional view (200B) respectively of the sensor assembly (100), according to an embodiment of the present invention. The top view (200A) of the sensor assembly (100) illustrates the cable (102), the spacer (118), and the flange (120) inside the housing (116). The longitudinal-sectional view (200B) of the sensor assembly illustrates the cable (102) and the leaf spring (104).
[00050] In particular, the top view (200A) of the sensor assembly illustrates the arrangement of the cable (102), the spacer (118), and the flange (120) with the housing (116). The cable (102) passing through the sensor assembly (100) rests on the leaf spring (104) in absence of any load. This resting position of the cable (102) on the leaf spring (104) is more prominently seen in the longitudinal-sectional view (200B) of the sensor assembly (100).
[00051] Figure 2B illustrates a simulated longitudinal sectional view (200C) of the sensor assembly (100), according to an embodiment of the present invention. In particular, the simulated longitudinal sectional view (200C) of the sensor assembly (100) clearly illustrates the arrangement of the cable (102) resting on the leaf spring (104), the spacers (118) and the flange (120) with the housing (116) of the sensor assembly (100).
[00052] Figure 3 illustrates an exploded view (300) of the sensor assembly (100), according to an embodiment of the present invention. The exploded view (300) illustrates the individual components of the sensor assembly (100) that includes the flange (120), the spacer (118), the cable (102), the leaf spring (104), the strain sensor (114) and the top cover (122).
[00053] Figure 4 illustrates three drawings and a simulated view of the flange (120) used in the sensor assembly (100), according to an embodiment of the present invention. In particular, Figure 4 illustrates a view (420A), a side view (420B), a front view (420C) and a simulated view (420D) of the flange (120). The flange (120) is a part that connects the cable (102) and the housing (116) of the sensor assembly (100). One end (425) of the flange (120) is crimped to the outer cover of the cable (102) and the other end of the flange (120) is connected to the housing (116). The inner cable or the core of the cable (102) is drawn out from the end of the flange (120) and passes over in contact with the leaf spring (104). The core of the cable (102) then runs over the leaf spring (104) in the housing (116) and passes through a second flange (120) on the other end of the housing (116) and though an outer cable crimped with the second flange (120).
[00054] Figure 5 illustrates an isometric view (518A), a front view (518B) and a simulated view (518C) of a spacer (118) used in the sensor assembly (100), according to an embodiment of the present invention. The spacer (118) is used to maintain the gap between the flange (120) and the housing (116). It is to be noted, that the spacer (118) is an element used to compensate for the size of the flange which is available, and the sensor assembly (100) may or may not have spacers (118).
[00055] Figure 6 illustrates an isometric view (616A), a plan view (616B) and a simulated view (616C) of a housing (116) used in the sensor assembly (100), according to an embodiment of the present invention. The metallic housing (116) encapsulates the entire sensor assembly (100). The housing (116) comprises a provision (624) for the flange (120) to rest on it, thereby maintaining the required distance between leaf spring (104) and the cable (102) that is drawn from the flange (120) while restraining an outer sheath of the cable (102) outside the housing (116). The housing (116) also has provisions (626) for the leaf spring (104) to be affixed inside the housing (116) at one end that is, the first end (110. The two provisions (626) may be two tapped blind holes or through holes configured to receive bolts, for example, and other hardware to hold the first end (110) of the leaf spring (104) in place. The other hardware mentioned may be plane washers and spring washers, for example. The housing (116) includes orifice (628) for one or more wires from the strain sensor (114) to be brought out of the housing (116) for measurement. This orifice (628) may then be sealed, for protecting the parts of the sensor assembly (100) encapsulated within the housing (116) from the external environment. The housing (116) is further provided with the top cover (122) that encapsulates the entire sensor assembly (100) within the housing (116) to ensure protection from ingress, of dust and water, for example, into the sensor assembly (100).
[00056] Figure 7 illustrates a side view (704A), an isometric view (704B), and a simulated view (704C) of a leaf spring (104), according to an embodiment of the present invention. In particular, the leaf spring (104) is the main functional component of the sensor assembly (100) that enables the measurement of stress on the cable (102). The magnitude of the deformation in the leaf spring (104) is sensed using the strain sensor (114) that is affixed to the leaf spring (104), with a suitable glue, for example, as illustrated in the side view (704A).
[00057] Thus, the disclosed invention has the advantage that the sensing element in the form of a leaf spring (104) in the sensor assembly (100) is completely encapsulated and hence protected from the environment such that it is not affected by ingress of moisture and dust, thereby retaining the sensitivity over time. Further, by the proper choice of materials and their dimensions, a person skilled in the art can implement a sensor assembly (100) for measuring changes in a wide range of tensile stresses on the cable (102). Still further, because of the static preset facility, the sensor assembly capable of measuring variations in tensile stress in the cable (102), both an increase and decrease, from the preset value. Further still, by implementing the disclosed sensor assembly (100) with a combined braking system, the system comprising a suitably configured controller may determine which of the two brakes, the left one or the right one, has been operated and by what magnitudes have the brake levers been displaced. Furthermore, the disclosed sensor assembly (100) is capable of overcoming the changes in the statically preset tensile stress on the cable due to repeated operation, for example, by dynamically presetting the initial tensile stress on the cable to zero every time the controller is commanded for operation, that is to stay, the vehicle is turned on for use. It has to be noted that none of the above advantages are offered by the state of the art sensor assemblies and systems at the same time.
[00058] Furthermore, embodiments of the disclosed devices and systems may be readily implemented, fully or partially, in software using, for example, object or object-oriented software development environments that provide portable source code that may be used on a variety of computer platforms. Alternatively, embodiments of the disclosed methods, processes, modules, devices, systems, and computer program product may be implemented partially or fully in hardware using, for example, standard logic circuits or a very-large-scale integration (VLSI) design. Other hardware or software may be used to implement embodiments depending on the speed and/or efficiency requirements of the systems, the particular function, and/or particular software or hardware system, microprocessor, or microcomputer being utilized.
[00059] In this application, unless specifically stated otherwise, the use of the singular includes the plural and the use of “or” means “and/or.” Furthermore, use of the terms “including” or “having” is not limiting. Any range described herein will be understood to include the endpoints and all values between the endpoints. Features of the disclosed embodiments may be combined, rearranged, omitted, etc., within the scope of the invention to produce additional embodiments. Furthermore, certain features may sometimes be used to advantage without a corresponding use of other features.
[00060] List of reference numerals:
Components Reference numerals
Sensor Assembly 100
Cable 102
Leaf spring 104
a first end of the leaf spring 110
a second end of the leaf spring 106
Planar Surface 108
Slidable Contact 112
Strain Sensor 114
Housing Assembly 116
Spacer 118
Flange 120
Top cover 122
No load condition 105
Pre-load condition 115
Fully loaded condition 125
Plan view of Sensor Assembly 200A
Longitudinal sectional view of Sensor Assembly 200B
Simulated sectional view of Sensor Assembly 200C
Exploded view of Sensor Assembly 300
Orthographic projection (top view) of Flange 420A
Orthographic projection (front view) of Flange 420B
Orthographic projection (side view) of Flange 420C
Simulated view of Flange 420D
End of flange crimped to cable sheath 425
Diagrammatic view of Spacer 518A
Side view of Spacer 518B
Simulated view of Spacer 518C
Isometric view of Housing 616A
Plan view of housing 616B
Simulated view of housing 616C
Flange Rest 624
Position for coupling leaf spring 626
Orifices 628
Plan view of leaf spring 704A
Isometric view of leaf spring 704B
Simulated view of leaf spring 704C

, Claims:1. A sensor assembly (100) for measuring a change in magnitude in a tensile stress on a cable (102), the sensor assembly (100) comprising:
a leaf spring (104), wherein a first end (110) of the leaf spring (104) is affixed to a planar surface (108) such that a second end (106) of the leaf spring (104) is in a slidable contact (112) with the planar surface (108); and
a strain sensor (114), mounted on the leaf spring (104) for sensing a deformation in the leaf spring (104), caused by a change in the tensile stress on the cable (102).

2. The sensor assembly (100) as claimed in claim 1, wherein the strain sensor (114) is mounted to an inner surface of the leaf spring (104).

3. The sensor assembly (100) as claimed in claim 1, wherein the leaf spring (104) is of a shape of an arc of a predefined curve.

4. The sensor assembly (100) as claimed in claim 1, wherein the sensor assembly (100) is encapsulated in a metallic housing (116).

5. The sensor assembly (100) as claimed in claim 1, wherein the housing (116) incapsulating the sensor assembly (100) comprises:
orifices for receiving a core of the cable (102),
one or more of a spacer (118) and a flange (120) for restraining an outer sheath of the cable (102) outside the housing (116) and
a cover (122) for encapsulating the sensor assembly (100) within the housing (116).

6. The sensor assembly (100) as claimed in claim 1, wherein the housing (116) comprises an orifice (628) for one or more wires from the strain sensor (114) to be brought out of the housing (116) and wherein the orifice (628) is sealed for protecting the sensor assembly (100) from external environment.

7. The sensor assembly (100) as claimed in claim 1, wherein the magnitude of the deformation in the leaf spring (104) is sensed using a strain sensor (114) comprising a strain gauge, a piezoelectric transducer, a force sensing resistor, an optical sensor, a fibre Bragg grating sensor, a proximity sensor, and a deflection gauge.

8. The sensor assembly (100) as claimed in claim 1, wherein the cable (102) is statically preset with a predefined tensile stress as a predefined percentage of the maximum tensile stress experienced by the cable (102), using a combined braking system mechanism.

9. A system comprising the sensor assembly (100) as claimed in claim 1 and a controller, wherein the controller is configured for:
dynamically presetting the tensile stress on the cable (102) by,
receiving a sensor signal each time the controller is commanded for operation and setting the value of the received signal as a reference value of the tensile stress on the cable; and
determining a change in the magnitude of the sensor signal as a measure of the tensile stress on the cable (102) relative to the reference value.

10. The system as claimed in claim 9, wherein a direction of change in the value of the sensor signal and the change in value of the sensor signal from the base value are used as an indication of a source of the change and the magnitude of the change in the tensile stress on the cable (102).