Cycle crank sensing arrangement

Abstract

Provided is a cycle crank sensing arrangement (10) comprising a strain gauge assembly (12) configured to measure an instantaneous tangential force on a crank (8) of a cycle (6), a first three-axis accelerometer (14) arrangeable at a first radius from the centre of rotation of the crank, and a second three-axis accelerometer (16) arrangeable at a second radius from the centre of rotation of the crank. Also included is a processor (18) arranged in signal communication with the strain gauge assembly (12) and the accelerometers (14 and 16). The processor (18) is configured to determine the real-time force input to the crank by means of the strain gauge assembly (12), to simultaneously sample both accelerometers (14 and 16) to determine real-time first and second centripetal acceleration values, to calculate an angular velocity of the crank via a differential between the first and second centripetal acceleration values and radii, and to calculate a power applied to the crank using said tangential force and calculated angular velocity. The cycle crank sensing arrangement (10) also includes a transmitter (20) arranged in signal communication with the processor (18) and configured to transmit the calculated power to a reporting system (24).

Description

CYCLE CRANK SENSING ARRANGEMENTTECHNICAL FIELD

[0001] This invention relates broadly to the field of cycling, and more speci fically to a cycle crank sensing arrangement , an associated cycle crank and an associated method of determining real-time cycle crank power .BACKGROUND ART

[0002] The following discussion of the background art i s intended to facilitate an understanding of the present invention only . The discussion i s not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application .

[0003] The field of cycling, also called bicycling or biking, is well-known in the art and is generally the use of bicycles for transport , recreation, exercise or sport . In addition to cycling for transport or other practical utilitarian purposes , cycling for exercise also provides a variety of health benefits .

[0004] The World Health Organi zation (WHO) states that cycling can reduce the risk of cancers , heart disease , and diabetes that are prevalent in sedentary li festyles . Cycling has also been used as part of rehabilitation for lower limb inj uries , particularly after hip and knee surgery . Individuals who cycle regularly have also reported mental health improvements , including less perceived stress and better vitality .

[0005] Elite cyclists , cycling enthusiasts and personnel involved in cycling rehabilitation for medical purposes often require high accuracy and reliability regarding cycling performance to monitor improvement and / or ef ficacy of training or rehabilitation treatment regimes . In light of this need, cycle monitoring techniques have been developed to facilitate in monitoring of cycling performance .

[0006] One conventional cycling monitoring technique comprises a power meter, which typically works by measuring the force on a pedal or a crank arm or the like , typically using strain gauges . Such a force measurement , as a torque , can be multiplied by angular velocity to determine power . Such conventional power meters generally measure a power output as a calculation of torque (how hard the pedals are pushed) multiplied by cadence (how fast the pedals are turning, or cadence ) . Cadence or pedalling rate is a measure of angular speed representing the number of revolutions per minute ( r / min or rpm) of the crank .

[0007] This power measurement provides a precise calculation of how much energy i s applied via the pedals at any given moment , which in turn allows calculation of a training load, identi fying precise ef fort levels throughout di f ferent training zones , tracking improvements in fitness , determining how many calories have been expended, etc . Such cycling performance measurement may facilitate pedalling analysis and related physiological progress to monitor and manage cycling training, improvement and / or rehabilitation treatment regimes .

[0008] Applicant has identi fied a need in the art for more accurate measurement and management of cycling performance via dynamic measurement of power, torque and / or rotational speed of a pedal crank generated by a cyclist ' s interaction through the pedals .

[0009] Conventional cycling power meters typically determine cadence via some manner of once-per-rotation trigger, such as a magnet triggered reed switch, which measures the time between each trigger to determine cadence . Some of the disadvantages of this method is it only provides the average speed of each rotation and it requires the fitting of a magnet to the bike frame . Other types of cycling power meters are configured to count pulses either optically or by magnets during pedalling, and others rely on capacitive or inductive coupling to sense an angle between two parts to determine cadence or angular velocity . Again, such configurations require alteration or modi fication of a cycle to add sensors , and can be di f ficult to implement .

[0010] A yet further approach uses micro-electromechanical systems (MEMS ) gyroscopes to provide a direct measurement of a crank rotational speed . However, such MEMS gyroscopes can be expensive and have relatively high electrical power consumption, which is not well-suited to battery-powered systems , either requiring larger ( and heavier ) batteries , or only providing limited use times , which is not ideal .

[0011] The current invention was conceived with these shortcomings in mind .SUMMARY OF THE INVENTION

[0012] The skilled addressee is to appreciate that reference herein to 'cycle' generally refers to any pedal- powered conveyance, such as a bicycle, a tricycle, a recumbent bicycle, an electric bicycle, etc. Similarly, a crank may comprise any suitable arm or lever for imparting rotary or oscillatory motion from a cyclist to a cycle drivetrain.

[0013] It is also to be appreciated that reference herein to 'real-time' or 'instantaneous' is to be understood as meaning an instance of time that may include a delay typically resulting from processing, calculation and / or transmission times inherent in electronic processing systems. These transmission and calculations times, albeit of generally small duration, do introduce some delay, i.e. typically less than a second or within milli- or microseconds, but feedback is provided relatively quickly, practically instantaneously or within substantial 'real-time' .

[0014] The skilled addressee will further appreciate that, in the general fields of statistics and control theory, Kalman filtering is an algorithm that use a series of measurements observed over time, typically containing noise and other inaccuracies, and produces estimates of unknown variables that tend to be more accurate than those based on a single measurement alone, by estimating a joint probability distribution over the variables for each time frame.

[0015] According to a first aspect of the invention there is provided a cycle crank sensing arrangement comprising: a strain gauge assembly configured to measure an instantaneous tangential force on a crank of a cycle;a first three-axis accelerometer arrangeable at a first radius from the centre of rotation of the crank; a second three-axis accelerometer arrangeable at a second radius from the centre of rotation of the crank; a processor arranged in signal communication with the strain gauge assembly and the accelerometers , the processor configured to : i . determine the real-time force input to the crank by means of the strain gauge assembly; ii . simultaneously sample both accelerometers to determine real-time first and second centripetal acceleration values ; iii . calculate an angular velocity of the crank via a di f ferential between the first and second centripetal acceleration values and radii ; and iv . calculating power applied to the crank using said tangential force and calculated angular velocity; and a transmitter arranged in signal communication with the processor and configured to transmit the calculated power to a reporting system .

[0016] In an embodiment , the strain gauge assembly is disposed on and / or in said crank to determine the real-time force input to the crank .

[0017] In an embodiment , the first and second accelerometers are co-axially arranged along the crank .

[0018] In an embodiment , the first and second accelerometers are co-axially arranged so that two shared axes of said accelerometers are substantially parallel with each other, e . g . Y and Z-axes of the accelerometers are in parallel .

[0019] In an embodiment, the first and second accelerometers are co-axially arranged so that a spindle of the cycle on which the crank revolves is substantially in parallel with a shared axis of said accelerometers, e.g. spindle in parallel with a shared Z-axis.

[0020] In an embodiment, the first and second accelerometers are co-axially arranged so that one shared axis of said accelerometers is diametrically opposed to each other to facilitate in isolating said first and second centripetal acceleration values from a gravity vector and external noise, e.g. a shared X-axis of the accelerometers is orientated in opposite directions.

[0021] In an embodiment, a differential between the first and second radii is predetermined.

[0022] In an embodiment, the processor comprises any suitable microprocessor or microcontroller configured to receive input, perform logical and arithmetical operations on a suitable instruction set, and provide output, as well as transitory and / or non-transitory electronic storage.

[0023] In an embodiment, the processor is configured to sample the strain gauge assembly and accelerometers at a rate of between 100 to 150Hz, e.g. at 128 Hz.

[0024] In an embodiment, the processor is configured to calculate an angular velocity of the crank using classical mechanics principles.

[0025] In an embodiment, the processor is configured to apply Kalman filtering techniques to instantaneous three-axis accelerometers values to facilitate calculation of crank angular velocity.

[0026] In an embodiment, the processor is preconfigured with a tuned Kalman filter algorithm devised via a calibration process of positioning the first and second accelerometers in predetermined orientations.

[0027] In an embodiment, the tuned Kalman filter algorithm comprises an estimation state based on a torque calculation derived from the instantaneous tangential force and an estimation of cycle distance travelled per radian of crank rotation and a mass of the cycle with rider.

[0028] In an embodiment, the tuned Kalman filter algorithm comprises a control-input state based on the first and second instantaneous centripetal acceleration values transformed to a reference frame of the crank.

[0029] In an embodiment, the transmitter comprises a wireless transmitter configured to transmit information under the Institute of Electrical and Electronics Engineers (IEEE) 802.15 standard for wireless communications protocol, or similar wireless communications protocols, e.g. ANT, ANT+, Bluetooth, BLE, ZigBee, or the like.

[0030] In an embodiment, the transmitter is configured to transmit information to the reporting system selectable from a non-exhaustive group consisting of instantaneous acceleration values, crank angle, measured tangential force, crank velocity, temporal data, processor status, batterystatus , strain gauge assembly status , accelerometer status , and transmitter status .

[0031] In an embodiment , the cycle crank sensing arrangement comprises a button cell or coin battery for energising the assembly, accelerometers , processor and transmitter .

[0032] According to a second aspect of the invention there is provided a cycle crank comprising : a strain gauge assembly configured to measure a real-time tangential force on the crank when fitted to a cycle ; a first three-axis accelerometer arranged at a first radius from the centre of rotation of the crank; a second three-axis accelerometer arranged at a second radius from the centre of rotation of the crank; a processor arranged in signal communication with the strain gauge assembly and the accelerometers , the processor configured to : i . determine the real-time force input to the crank by means of the strain gauge assembly; ii . simultaneously sample both accelerometers to determine real-time first and second centripetal acceleration values ; iii . calculate an angular velocity of the crank via a di f ferential between the first and second centripetal acceleration values and radii ; and iv . calculating power applied to the crank using said tangential force and calculated angular velocity; and a transmitter arranged in signal communication with the processor and configured to transmit the calculated power to a reporting system .

[0033] In an embodiment, the strain gauge assembly is disposed on and / or in said crank to determine the real-time force input to the crank.

[0034] In an embodiment, the first and second accelerometers are co-axially arranged along the crank.

[0035] In an embodiment, the first and second accelerometers are co-axially arranged so that two shared axes of said accelerometers are parallel with each other, e.g. Y and Z-axes of the accelerometers are in parallel.

[0036] In an embodiment, the first and second accelerometers are co-axially arranged so that a spindle of the cycle on which the crank revolves is in parallel with a shared axis of said accelerometers, e.g. spindle in parallel with a shared Z-axis.

[0037] In an embodiment, the first and second accelerometers are co-axially arranged so that one shared axis of said accelerometers is diametrically opposed to each other to facilitate in isolating said first and second centripetal acceleration values from a gravity vector and external noise, e.g. a shared X-axis of the accelerometers is orientated in opposite directions.

[0038] In an embodiment, a differential between the first and second radii is predetermined.

[0039] In an embodiment, the processor comprises any suitable microprocessor or microcontroller configured to receive input, perform logical and arithmetical operations ona suitable instruction set, and provide output, as well as transitory and / or non-transitory electronic storage.

[0040] In an embodiment, the processor is configured to sample the strain gauge assembly and accelerometers at a rate of between 100 to 150Hz, e.g. at 128 Hz.

[0041] In an embodiment, the processor is configured to calculate an angular velocity of the crank using classical mechanics principles.

[0042] In an embodiment, the processor is configured to apply Kalman filtering techniques to instantaneous three-axis accelerometers values to facilitate calculation of crank angular velocity.

[0043] In an embodiment, the processor is preconfigured with a tuned Kalman filter algorithm devised via a calibration process of positioning the first and second accelerometers in predetermined orientations.

[0044] In an embodiment, the tuned Kalman filter algorithm comprises an estimation state based on a torque calculation derived from the instantaneous tangential force and an estimation of cycle distance travelled per radian of crank rotation and a mass of the cycle with rider.

[0045] In an embodiment, the tuned Kalman filter algorithm comprises a control-input state based on the first and second instantaneous centripetal acceleration values transformed to a reference frame of the crank.

[0046] In an embodiment, the transmitter comprises a wireless transmitter configured to transmit information under the Institute of Electrical and Electronics Engineers (IEEE) 802.15 standard for wireless communications protocol, or similar wireless communications protocols, e.g. ANT, ANT+, Bluetooth, BLE, ZigBee, or the like.

[0047] In an embodiment, the transmitter is configured to transmit information to the reporting system selectable from a non-exhaustive group consisting of instantaneous acceleration values, crank angle, measured tangential force, crank velocity, temporal data, processor status, battery status, strain gauge assembly status, accelerometer status, and transmitter status.

[0048] In an embodiment, the cycle crank comprises a button cell or coin battery for energising the assembly, accelerometers, processor and transmitter.

[0049] According to a third aspect of the present invention there is provided a method of determining real-time cycle crank power, said method comprising the steps of: measuring, via a strain gauge assembly, a real-time force input on a crank of a cycle; determining, via first and second accelerometers arranged at respective first and second radii from a centre of rotation of the crank, instantaneous first and second centripetal acceleration values; calculating, via a processor disposed in and / or or the crank, an instantaneous angular velocity of the crank via a differential between said first and second centripetal acceleration values and radii;calculating, via said processor, a power applied to the crank using said measured force input and calculated angular velocity; and transmitting, via a transmitter arranged in signal communication with the processor, the calculated real-time power to a reporting system.

[0050] In an embodiment, the first and second accelerometers are co-axially arranged along the crank.

[0051] In an embodiment, the first and second accelerometers are co-axially arranged so that two shared axes of said accelerometers are parallel with each other, e.g. Y and Z-axes of the accelerometers are in parallel.

[0052] In an embodiment, the first and second accelerometers are co-axially arranged so that a spindle of the cycle on which the crank revolves is in parallel with a shared axis of said accelerometers, e.g. spindle in parallel with a shared Z-axis.

[0053] In an embodiment, the first and second accelerometers are co-axially arranged so that one shared axis of said accelerometers is diametrically opposed to each other to facilitate in isolating said first and second centripetal acceleration values from a gravity vector and external noise, e.g. a shared X-axis of the accelerometers is orientated in opposite directions.

[0054] In an embodiment, a differential between the first and second radii is predetermined.

[0055] In an embodiment, the processor is configured to sample the strain gauge assembly and accelerometers at a rate of between 100 to 150Hz, e.g. at 128 Hz.

[0056] In an embodiment, the step of calculating the angular velocity of the crank is performed by the processor configured to use classical mechanics principles.

[0057] In an embodiment, the step of calculating is performed by the processor being configured to apply Kalman filtering techniques to determined instantaneous three-axis accelerometers values to facilitate calculation of crank angular velocity.

[0058] In an embodiment, the method includes the step of preconfiguring the processor with a tuned Kalman filter algorithm devised via a calibration process of positioning the first and second accelerometers in predetermined orientations.

[0059] In an embodiment, the tuned Kalman filter algorithm comprises an estimation state based on a torque calculation derived from the instantaneous tangential force and an estimation of cycle distance travelled per radian of crank rotation and a mass of the cycle with rider.

[0060] In an embodiment, the tuned Kalman filter algorithm comprises a control-input state based on the first and second instantaneous centripetal acceleration values transformed to a reference frame of the crank.

[0061] In an embodiment, the step of transmitting via the transmitter comprises transmitting information under theInstitute of Electrical and Electronics Engineers (IEEE)802.15 standard for wireless communications protocol, or similar wireless communications protocols, e.g. ANT, ANT+, Bluetooth, BLE, ZigBee, or the like.

[0062] In an embodiment, the step of transmitting comprises transmitting information to the reporting system selectable from a non-exhaustive group consisting of instantaneous acceleration values, crank angle, measured tangential force, crank velocity, temporal data, processor status, battery status, strain gauge assembly status, accelerometer status, and transmitter status.

[0063] According to a further aspect of the invention there is provided a cycle crank sensing arrangement, an associated cycle crank, and an associated method of determining real-time cycle crank power, substantially as herein described and / or illustrated .BRIEF DESCRIPTION OF THE DRAWINGSThe description will be made with reference to the accompanying drawings in which:Figure 1 is a diagrammatic side-view representation of a frame of reference of a cycle with which the cycle crank sensing arrangement of the present invention is useable;Figure 2 is a diagrammatic top-view representation of a crank including the cycle crank sensing arrangement according to aspects of the present invention;Figure 3 is diagrammatic side-view representation of the crank of Figure 2 with the cycle crank sensing arrangement,showing a frame o f reference for calculations using classical mechanics principles ;Figure 4 is a diagrammatic representation of one embodiment of the cycle crank sensing arrangement in accordance with aspects of the present invention; andFigures 5A to 5C are diagrammatic top, bottom and perspective-view rendered representations of one embodiment of an implementation of the cycle crank sensing arrangement of Figure 4 .DETAILED DESCRIPTION OF EMBODIMENTS

[0064] Further features of the present invention are more fully described in the following description of several nonlimiting embodiments thereof . This description is included solely for the purposes of exempli fying the present invention to the skilled addressee . It should not be understood as a restriction on the broad summary, disclosure or description of the invention as set out above .

[0065] In the figures , incorporated to illustrate features of the example embodiment or embodiments , like reference numerals are used to identi fy like parts throughout . Additionally, features , mechanisms and aspects well-known and understood in the art will not be described in detail , as such features , mechanisms and aspects will be within the understanding of the skilled addressee .

[0066] Addit ionally, the accompanying figures do not represent engineering or design drawings , but provide a functional overview of the invention only . As a result ,features and practical construction details required for various embodiments may not be indicated in each figure , but such construction requirements will be within the understanding of the skilled addressee .

[0067] The cycle crank sensing arrangement 10 of the present invention has been speci fically devised to enable measurement and calculation of cycling-related metrics , such as an ef fective power applied to the crank, angular velocity of cycle crank arms , acceleration metrics , and the like , without requiring the use of gyroscope-based sensors , that tend to have relatively high power requirements . Accordingly, arrangement 10 has been devised as a small device which can be incorporated as part of a crank 8 of a cycle 6 and be powered by a small battery, such as a button cell or coin battery 26 , while providing accurate measurements without high power consumption for extended periods of time .

[0068] Broadly, the cycle crank sensing arrangement 10 comprises a strain gauge assembly 12 , first and second three- axis accelerometers 14 and 16 , a processor 18 , and a transmitter 20 . The strain gauge assembly 12 is generally configured to measure an instantaneous tangential force on the crank 8 of the cycle 6 , where the strain gauge assembly 12 is disposed on and / or in said crank 8 to determine the real-time force input to the crank 8 , typically during cycling via suitable pedals . The cycle crank sensing arrangement 10 also generally comprises a button cell or coin battery 26 for energising the as sembly 12 , accelerometers 14 and 16 , processor 18 and transmitter 20 .

[0069] The strain gauge assembly 12 typically comprises aWheatstone bridge formed from four suitably-arranged activestrain gauges, along with signal amplification and conditioning and an analogue to digital converter. Of course, variations hereon are possible and within the scope of the present invention.

[0070] The first three-axis accelerometer 14 is generally arranged at a first radius from the centre of rotation of the crank 8, with the second three-axis accelerometer 16 arranged at a second radius from the centre of rotation of the crank 8. Such first and second radii differ and a differential or difference between the first and second radii is generally predetermined, i.e. accelerometers 14 and 16 are separated a known distance from each other. In one embodiment, such a predetermined differential is determined by mounting accelerometers 14 and 16 a known distance apart on a printed circuit board forming part of the cycle crank sensing arrangement 10, as shown in Figure 5. The accelerometers 14 and 16 operatively measure acceleration values along three axes in three-dimensional space, with said axes arranged in a particular frame of reference relative to the crank arm 8.

[0071] Importantly, as shown in Figures 1 and 2, the first and second accelerometers 14 and 16 are generally co-axially arranged along the crank 8. In one embodiment, the first and second accelerometers 14 and 16 are co-axially arranged so that two shared axes thereof are substantially parallel with each other, e.g. within the shown frame of reference, the Y and Z-axes of the accelerometers 14 and 16 are arranged in parallel. In the exemplified embodiment, the first and second accelerometers 14 and 16 are also co-axially arranged so that a spindle of the cycle 6 on which the crank 8 revolves is substantially in parallel with a shared axis of the accelerometers, e.g. the spindle of the crank 8 is arranged tobe parallel with a shared Z-axis of the accelerometers 14 and 16 . Of course , such exact relational alignment may not be practically achievable , but the skilled addressee is to appreciate that appropriately calibrating each accelerometer 14 and 16 to generate a trans formation matrix to convert their respective measurements into a consistent reference frame may be used to accommodate any variances in exact relational alignment , e . g . as part of a tuned Kalman filter algorithm, described below, or the like .

[0072] In a typical embodiment , as per the designated frame of reference of Figures 1 and 2 , the first and second accelerometers 14 and 16 are further co-axially arranged so that one shared axis of said accelerometers 14 and 16 is diametrically opposed and co-linear to each other to facilitate in isolating said first and second centripetal acceleration values from a gravity vector and external noise . For example , by arranging the accelerometers 14 and 16 as described, a shared X-axis of the accelerometers is orientated in opposite directions , with a gravity vector typically along a Y-axis , which can be isolated as a mutual and corresponding measurement between both accelerometers 14 and 16 .

[0073] In one embodiment , arrangement 10 uses two I IS2DLPC MEMS digital output ultra-low-power 3-axis accelerometer 3- axis accelerometers by STMicroelectronics™, but variations hereon are possible and expected . The first accelerometer 14 is located 28 . 5mm from the spindle axis , and the second accelerometer 16 is located 61 . 5mm from the spindle axis . Both accelerometers 14 and 16 are placed an axis along the crank 8 , as shown, so that the accelerometers 14 and 16 are tilted relative to the plane of crank rotation . As described, one accelerometer closest to the spindle is orientated with an Xaxis thereof directed towards the spindle , and the other accelerometer is orientated with an X axis thereof pointing away from the spindle .

[0074] Arrangement 10 further comprises processor 18 which is arranged in signal communication with the strain gauge assembly 12 and the accelerometers 14 and 16 . The processor 18 is generally conf igured by means o f a suitable instruction set to determine the real-time force input to the crank 8 by means of the strain gauge assembly 12 . Processor 18 is further configured simultaneously to sample both accelerometers 14 and 16 in order to determine real-time first and second centripetal acceleration values based on where the accelerometers 14 and 16 are in a rotation about the crank spindle . In one embodiment , the processor 18 may be configured to sample the strain gauge assembly 12 and accelerometers 14 and 16 at a rate of between 100 to 150Hz , such as at 128 Hz , but of course variations hereon are possible and expected .

[0075] In this manner, processor 18 is configurable to calculate an instantaneous angular velocity of the crank 8 via a di f ferential between the first and second centripetal acceleration values and radii between the accelerometers 14 and 16 . In one embodiment , the processor is configured to calculate an angular velocity of the crank using classical mechanics principles . For example , an angular velocity of the crank is calculable by the relationship :where w is the angular velocity of the crank 8 in radians per second, a represents respective centripetal acceleration values and r is the respective radii in metres .

[0076] If the angular velocity of the crank 8 is known, an effective real-time power applied to the crank is calculable by the processor 18 using the measured input force to the crank and known radius to derive torque, with power being a function of crank angular velocity and torque, as known in the art. For example, energy may be integrated the energy and, once a full crank rotation has completed, effective power during the rotation can be calculated, or the like.

[0077] Using the frame of reference established in Figures 1 and 3, a cycle coordinate system can be established where an origin is located at the intersection of a bottom bracket spindle axis and the mid plane of the cycle frame, as shown. In such a coordinate system, the X-axis lies on the horizontal and points towards the front of the cycle, the Y axis lies on the vertical and points upwards, and the Z axis lies horizontally and points outward on the starboard side of the cycle, as shown.

[0078] Similarly, a crank coordinate system is established where an origin lies at the intersection of the spindle axis and the mid plane of the cycle frame. In such a crank coordinate system, the X' axis lies normal to the spindle axis passing through the pedal axis on the starboard side of the bike, the Y' axis traverse thereto, and the Z' axis lies coincident with the spindle axis pointing outward on the starboard side of the bike .

[0079] In such a frame of reference, state variables for classical mechanics principles can be defined as follows:

[0080] Additional system parameters are defined as:

[0081] Similarly, acceleration values measured by the first and second accelerometers 14 and 16 along three axes in three- dimensional space can be defined as:

[0082] In this manner, as known in the art of classical mechanics, the following kinematics provide relationships between the defined variables and parameters:

[0083] At the centre of gravity of the system, the following equation of motion relationships apply:where a best estimate for total crank torque is made by doubling the calculated single crank torque to account for the second crank of the cycle 6 . An estimate of the crank angle and crank velocity can then be made by the relationship :

[0084] Such an estimation generally lacks suf ficient accuracy, as the instantaneous crank angle is af fected by various external factors including the other crank' s torque , any braking or deceleration the cycle is subj ected to , i f the cycle is travelling along and incline , i . e . not a perfectly hori zontal surface , a gear ratio between a wheel of the cycle and the crank, unaccounted friction in the system, and the like .

[0085] For this reason, the processor 18 is typically configured to apply Kalman filtering techniques to the instantaneous three-axis accelerometers values and associated calculations above in order to facilitate more accurate calculation of crank angle and associated angular velocity . For example , in one embodiment , the processor 18 is preconfigured with a tuned Kalman filter algorithm which comprises an estimation state based on a torque calculation derived from the instantaneous tangential force and an estimation of cycle distance travelled per radian of crank rotation and a mass of the cycle with rider . Similarly, in one embodiment , the tuned Kalman filter algorithm may comprise acontrol-input state based on the first and second instantaneous centripetal acceleration values transformed to a reference frame of the crank 8, as defined above.

[0086] In one embodiment, the processor 18 may be preconfigured with the suitably-tuned Kalman filter algorithm which is devised via a calibration process of positioning the first and second accelerometers 14 and 16 in predetermined orientations. For example, by positioning the crank vertically with a pedal end upwards, i.e. X axis up, the gravity vector is aligned with the crank X' axis. Similarly, positioning the crank horizontally with the pedal to the right of the spindle, i.e. Y axis up, the gravity vector is aligned with the crank Y' axis. Additionally, positioning the crank with the spindle vertically and below the crank arm, i.e. Z axis up, the gravity vector is aligned with the crank Z' axis.

[0087] Arrangement 10 also includes the transmitter 20 which is generally arranged in signal communication with the processor 18 and is configured so that the processor 18 is enabled to transmit the instantaneous crank angle, crank velocity, crank acceleration and / or calculated power to a reporting system 24. In one embodiment, the transmitter 20 comprises a wireless transmitter configured to transmit information under the Institute of Electrical and Electronics Engineers (IEEE) 802.15 standard for wireless communications protocol, or similar wireless communications protocols, e.g. ANT, ANT+, Bluetooth, BLE, ZigBee, or the like. The reporting system 24 may comprise, for example a smart phone running a suitable app, a computer configured to display and analyse the transmitted information, etc.

[0088] The skilled addressee is to appreciate that the transmitter 20 may be configured to transmit any desired information to the reporting system 24 , such as instantaneous acceleration values , crank angle , measured tangential force , crank velocity, temporal data, processor status , battery status , strain gauge assembly status , accelerometer status , and transmitter status .

[0001] The skilled addressee is further to appreciate that the present invention includes an associated method of determining real-time cycle crank power, angular velocity, etc . , as described above . Such a method generally comprises the steps of measuring, via the strain gauge assembly 12 , a real-time force input on the crank 8 of a cycle 6 , determining, via the first and second accelerometers 14 and 16 , instantaneous first and second centripetal acceleration values , and calculating, via the processor 18 disposed in and / or or the crank, an instantaneous angular velocity of the crank via a di f ferential between said first and second centripetal acceleration values and radii . The method further includes the steps of calculating, via said processor 18 , a real-time power applied to the crank using said measured force input and calculated angular velocity, and transmitting, via the transmitter 20 , the calculated real-time power to a reporting system 24 .

[0002] Applicant believes it particularly advantageous that the present invention provides for a cycle crank sensing arrangement 10 able accurately to measure and calculate cycling-related performance metrics without the use of gyroscopes to provide a direct measurement of a crank rotational speed . Arrangement 10 utilises Kalman filtering techniques to improve accuracy of calculations , thereby beingable to make use of low-power accelerometers which is operable by means of a small battery.

[0003] Optional embodiments of the present invention may also be said to broadly consist in the parts, elements and features referred to or indicated herein, individually or collectively, in any or all combinations of two or more of the parts, elements or features, and wherein specific integers are mentioned herein which have known equivalents in the art to which the invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth. In the example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail, as such will be readily understood by the skilled addressee .

[0004] The use of the terms "a", "an", "said", "the", and / or similar referents in the context of describing various embodiments (especially in the context of the claimed subject matter) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including, " and "containing" are to be construed as open- ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. No language in the specification should be construed as indicating any non-claimed subject matter as essential to the practice of the claimed subject matter .

[0005] Spatially relative terms, such as "inner, " "outer, " "beneath, " "below, " "lower, " "above, " "upper, " and the like,may be used herein for ease of description to describe one element or feature's relationship to another element (s) or feature (s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the example term "below" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0006] It is to be appreciated that reference to "one example" or "an example" of the invention, or similar exemplary language (e.g., "such as") herein, is not made in an exclusive sense. Various substantially and specifically practical and useful exemplary embodiments of the claimed subject matter are described herein, textually and / or graphically, for carrying out the claimed subject matter.

[0007] Accordingly, one example may exemplify certain aspects of the invention, whilst other aspects are exemplified in a different example. These examples are intended to assist the skilled person in performing the invention and are not intended to limit the overall scope of the invention in any way unless the context clearly indicates otherwise. Variations (e.g. modifications and / or enhancements) of one or more embodiments described herein might become apparent to those of ordinary skill in the art upon reading this application. The inventor (s) expects skilled artisans to employ such variations as appropriate, and the inventor (s) intends for the claimedsubject matter to be practiced other than as specifically described herein.

[0008] Any method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.

Claims

CLAIMS1 . A cycle crank sensing arrangement comprising : a strain gauge assembly configured to measure an instantaneous tangential force on a crank of a cycle ; a first three-axis accelerometer arrangeable at a first radius from the centre of rotation of the crank; a second three-axis accelerometer arrangeable at a second radius from the centre of rotation of the crank; a processor arranged in signal communication with the strain gauge assembly and the accelerometers , the processor configured to : i . determine the real-time force input to the crank by means of the strain gauge assembly; ii . simultaneously sample both accelerometers to determine real-time first and second centripetal acceleration values ; iii . calculate an angular velocity of the crank via a di f ferential between the first and second centripetal acceleration values and radii ; and iv . calculating power applied to the crank using said tangential force and calculated angular velocity; and a transmitter arranged in signal communication with the processor and configured to transmit the calculated power to a reporting system .2 . The cycle crank sensing arrangement of claim 1 , wherein the strain gauge assembly is disposed on and / or in said crank to determine the real-time force input to the crank .

3. The cycle crank sensing arrangement of either of claims 1 or 2, wherein the first and second accelerometers are coaxially arranged along the crank.

4. The cycle crank sensing arrangement of any of claims 1 to 3, wherein the first and second accelerometers are co-axially arranged so that two shared axes of said accelerometers are substantially parallel with each other, e.g. Y and Z-axes of the accelerometers are in parallel.

5. The cycle crank sensing arrangement any of claims 1 to 4, wherein the first and second accelerometers are co-axially arranged so that a spindle of the cycle on which the crank revolves is substantially in parallel with a shared axis of said accelerometers, e.g. spindle in parallel with a shared Z- axis .

6. The cycle crank sensing arrangement any of claims 1 to 5, wherein the first and second accelerometers are co-axially arranged so that one shared axis of said accelerometers is diametrically opposed to each other to facilitate in isolating said first and second centripetal acceleration values from a gravity vector and external noise, e.g. a shared X-axis of the accelerometers is orientated in opposite directions.

7. The cycle crank sensing arrangement any of claims 1 to 6, wherein a differential between the first and second radii is predetermined .

8. The cycle crank sensing arrangement any of claims 1 to 7, wherein the processor is configured to sample the strain gauge assembly and accelerometers at a rate of between 100 to 150Hz, e.g. at 128 Hz .9 . The cycle crank sensing arrangement any of claims 1 to 8 , wherein the processor is configured to calculate an angular velocity of the crank using classical mechanics principles .10 . The cycle crank sensing arrangement any of claims 1 to 9 , wherein the processor is configured to apply Kalman filtering techniques to instantaneous three-axis accelerometers values to facilitate calculation of crank angular velocity .11 . The cycle crank sensing arrangement any of claims 1 to 10 , wherein the processor is preconfigured with a tuned Kalman filter algorithm devised via a calibration process of positioning the first and second accelerometers in predetermined orientations .12 . The cycle crank sensing arrangement of claim 11 , wherein the tuned Kalman filter algorithm comprises an estimation state based on a torque calculation derived from the instantaneous tangential force and an estimation of cycle distance travelled per radian of crank rotation and a mass of the cycle with rider .13 . The cycle crank sensing arrangement either of claims 11 or 12 , wherein the tuned Kalman filter algorithm comprises a control-input state based on the first and second instantaneous centripetal acceleration values trans formed to a reference frame of the crank .14 . The cycle crank sensing arrangement any of claims 1 to 13 , wherein the transmitter comprises a wireless transmitter configured to transmit information under the Institute ofElectrical and Electronics Engineers ( IEEE ) 802 . 15 standardfor wireless communications protocol, or similar wireless communications protocols, e.g. ANT, ANT+, Bluetooth, BLE, ZigBee, or the like.

15. The cycle crank sensing arrangement any of claims 1 to14, wherein the transmitter is configured to transmit information to the reporting system selectable from a non- exhaustive group consisting of instantaneous acceleration values, crank angle, measured tangential force, crank velocity, temporal data, processor status, battery status, strain gauge assembly status, accelerometer status, and transmitter status.

16. The cycle crank sensing arrangement any of claims 1 to15, wherein the cycle crank sensing arrangement comprises a button cell or coin battery for energising the assembly, accelerometers, processor and transmitter.

17. A cycle crank comprising: a strain gauge assembly configured to measure a real-time tangential force on the crank when fitted to a cycle; a first three-axis accelerometer arranged at a first radius from the centre of rotation of the crank; a second three-axis accelerometer arranged at a second radius from the centre of rotation of the crank; a processor arranged in signal communication with the strain gauge assembly and the accelerometers, the processor configured to: i. determine the real-time force input to the crank by means of the strain gauge assembly; ii. simultaneously sample both accelerometers to determine real-time first and second centripetal acceleration values;iii . calculate an angular velocity of the crank via a di f ferential between the first and second centripetal acceleration values and radii ; and iv . calculating power applied to the crank using said tangential force and calculated angular velocity; and a transmitter arranged in signal communication with the processor and configured to transmit the calculated power to a reporting system .18 . The cycle crank of claim 17 , wherein the strain gauge assembly is disposed on and / or in said crank to determine the real-time force input to the crank .19 . The cycle crank of either of claims 17 or 18 , wherein the first and second accelerometers are co-axially arranged along the crank .20 . The cycle crank of any of claims 17 to 19 , wherein the first and second accelerometers are co-axially arranged so that two shared axes of said accelerometers are parallel with each other, e . g . Y and Z-axes of the accelerometers are in parallel .21 . The cycle crank of any of claims 17 to 20 , wherein the first and second accelerometers are co-axially arranged so that a spindle of the cycle on which the crank revolves is in parallel with a shared axis of said accelerometers , e . g . spindle in parallel with a shared Z-axis .22 . The cycle crank of any of claims 17 to 21 , wherein the first and second accelerometers are co-axially arranged so that one shared axis of said accelerometers is diametricallyopposed to each other to facilitate in isolating said first and second centripetal acceleration values from a gravity vector and external noise , e . g . a shared X-axis of the accelerometers is orientated in opposite directions .23 . The cycle crank of any of claims 17 to 22 , wherein a di f ferential between the first and second radii is predetermined .24 . The cycle crank of any of claims 17 to 23 , wherein the processor is configured to sample the strain gauge assembly and accelerometers at a rate of between 100 to 150Hz , e . g . at 128 Hz .25 . The cycle crank of any of claims 17 to 24 , wherein the processor is configured to calculate an angular velocity of the crank using classical mechanics principles .26 . The cycle crank of any of claims 17 to 25 , wherein the processor is configured to apply Kalman filtering techniques to instantaneous three-axis accelerometers values to facilitate calculation of crank angular velocity .27 . The cycle crank of any of claims 17 to 26 , wherein the processor is preconfigured with a tuned Kalman filter algorithm devised via a calibration process of positioning the first and second accelerometers in predetermined orientations .28 . The cycle crank of claim 27 , wherein the tuned Kalman filter algorithm comprises an estimation state based on a torque calculation derived from the instantaneous tangential force and an estimation of cycle distance travelled per radian of crank rotation and a mass of the cycle with rider .

29. The cycle crank of either of claims 27 or 28, wherein the tuned Kalman filter algorithm comprises a control-input state based on the first and second instantaneous centripetal acceleration values transformed to a reference frame of the crank .

30. The cycle crank of any of claims 17 to 29, wherein the transmitter comprises a wireless transmitter configured to transmit information under the Institute of Electrical and Electronics Engineers (IEEE) 802.15 standard for wireless communications protocol, or similar wireless communications protocols, e.g. ANT, ANT+, Bluetooth, BLE, ZigBee, or the like.

31. The cycle crank of any of claims 17 to 30, wherein the transmitter is configured to transmit information to the reporting system selectable from a non-exhaust ive group consisting of instantaneous acceleration values, crank angle, measured tangential force, crank velocity, temporal data, processor status, battery status, strain gauge assembly status, accelerometer status, and transmitter status.

32. The cycle crank of any of claims 17 to 31, wherein the cycle crank comprises a button cell or coin battery for energising the assembly, accelerometers, processor and transmitter .

33. A method of determining real-time cycle crank power, said method comprising the steps of: measuring, via a strain gauge assembly, a real-time force input on a crank of a cycle; determining, via first and second accelerometers arranged at respective first and second radii from a centre of rotationof the crank, instantaneous first and second centripetal acceleration values ; calculating, via a processor disposed in and / or or the crank, an instantaneous angular velocity of the crank via a di f ferential between said first and second centripetal acceleration values and radii ; calculating, via said processor, a power applied to the crank using said measured force input and calculated angular velocity; and transmitting, via a transmitter arranged in signal communication with the processor, the calculated real-time power to a reporting system .34 . The method of claim 33 , wherein the first and second accelerometers are co-axially arranged along the crank .35 . The method of either of claims 33 or 34 , wherein the first and second accelerometers are co-axially arranged so that two shared axes of said accelerometers are parallel with each other, e . g . Y and Z-axes of the accelerometers are in parallel .36 . The method of any of claims 33 to 35 , wherein the first and second accelerometers are co-axially arranged so that a spindle of the cycle on which the crank revolves is in parallel with a shared axis of said accelerometers , e . g . spindle in parallel with a shared Z-axis .37 . The method of any of claims 33 to 36 , wherein the first and second accelerometers are co-axially arranged so that one shared axis of said accelerometers is diametrically opposed to each other to facilitate in isolating said first and second centripetal acceleration values from a gravity vector andexternal noise , e . g . a shared X-axis of the accelerometers is orientated in opposite directions .38 . The method of any of claims 33 to 37 , wherein a di f ferential between the first and second radii is predetermined .39 . The method of any of claims 33 to 38 , wherein the processor is configured to sample the strain gauge assembly and accelerometers at a rate of between 100 to 150Hz , e . g . at 128 Hz .40 . The method of any of claims 33 to 39 , wherein the step of calculating the angular velocity of the crank is performed by the processor configured to use classical mechanics principles .41 . The method of any of claims 33 to 40 , wherein the step of calculating is performed by the processor being configured to apply Kalman filtering techniques to determined instantaneous three-axis accelerometers values to facilitate calculation of crank angular velocity .42 . The method of any of claims 33 to 41 , wherein the method includes the step of preconfiguring the processor with a tuned Kalman filter algorithm devised via a calibration process of positioning the first and second accelerometers in predetermined orientations .43 . The method of claim 42 , wherein the tuned Kalman filter algorithm comprises an estimation state based on a torque calculation derived from the instantaneous tangential forceand an estimation of cycle distance travelled per radian of crank rotation and a mass of the cycle with rider.

44. The method of either of claims 42 or 43, wherein the tuned Kalman filter algorithm comprises a control-input state based on the first and second instantaneous centripetal acceleration values transformed to a reference frame of the crank.

45. The method of any of claims 33 to 44, wherein the step of transmitting via the transmitter comprises transmitting information under the Institute of Electrical and Electronics Engineers (IEEE) 802.15 standard for wireless communications protocol, or similar wireless communications protocols, e.g. ANT, ANT+, Bluetooth, BLE, ZigBee, or the like.

46. The method of any of claims 33 to 45, wherein the step of transmitting comprises transmitting information to the reporting system selectable from a non-exhaust ive group consisting of instantaneous acceleration values, crank angle, measured tangential force, crank velocity, temporal data, processor status, battery status, strain gauge assembly status, accelerometer status, and transmitter status.

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