METHOD FOR DETERMINING AT LEAST ONE FRICTION PARAMETER OF A CYCLIST IN REAL TRAVEL CONDITIONS, AND ASSOCIATED APPARATUS

Abstract

The invention relates to a method for determining at least one friction parameter of a cyclist in real travel conditions, on a section of track or road having a slope and extending longitudinally from a starting line (LD) to a finishing line (LA) over a length (L), each of the starting (LD) and finishing (LA) lines extending transversely over a width (l). The method, based on an equation derived from the principle of conservation of energy, comprises a step of measuring a first transverse position of passage (P1) of the cyclist on the starting line (LD) and a second transverse position of passage (P2) of the cyclist on the finishing line (LA), each of the first and second transverse positions (P1, P2) being determined along the width (l) with an accuracy of + / -5 cm. The invention also relates to apparatus for measuring a transverse position of passage of the cyclist.Figure to be published with the abstract: Figure 1.

Description

Title of the invention: METHOD FOR DETERMINING AT LEAST ONE FRICTION PARAMETER OF A CYCLIST IN REAL TRAVEL CONDITIONS, AND ASSOCIATED EQUIPMENT FIELD OF THE INVENTION

[0001] The present invention relates to the field of devices and methods for measuring and determining resistive forces exerted on a cyclist in motion. The invention aims in particular to determine parameters characterizing the resistive forces such as the aerodynamic drag surface and / or the rolling coefficient of the cyclist on his bicycle, with precision, reproducibility and by implementing a simple and rapid protocol.

[0002] TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] There are two categories of tests for measuring key cyclist friction parameters (rolling and aerodynamics): stationary tests (wind tunnel) and in-motion tests (real-life travel conditions). Real-life tests are particularly interesting because they can take into account parameters related to the cyclist's posture during effort and movement.

[0004] As explained in document WO2022074330A1, a moving cyclist is subjected to several forces (gravity force, rolling force, friction force with the air, forward force). In order to minimize the energy cost of the vehicle's movement, it appears particularly key to know how to accurately measure the friction applied to the cyclist (rolling and aerodynamics).

[0005] The methods for determining the aerodynamic drag surface and the rolling coefficient proposed by this document, based on the principle of conservation of energy, generally offer excellent reproducibility as well as great simplicity of implementation.

[0006] It was nevertheless observed that in certain test route conditions, short and involving a sloping road (for example on a velodrome track), the level of precision for determining the friction parameters was lower than expected.

[0007] SUBJECT OF THE INVENTION

[0008] The present invention aims to remedy all or part of the aforementioned drawbacks. It relates to a method for determining at least one friction parameter of a cyclist in real travel conditions, on a section of track or road with a slope.

[0009] BRIEF DESCRIPTION OF THE INVENTION

[0010] The invention relates to a method for determining at least one friction parameter of a cyclist in real travel conditions, on a section of track or road having a slope and extending longitudinally from a starting line to a finishing line over a length, each of the starting and finishing lines extending transversely over a width.

[0011] The method, based on an equation derived from the principle of conservation of energy, is remarkable in that it comprises a step of measuring a first transverse position of passage of the cyclist on the starting line and a second transverse position of passage of the cyclist on the finishing line, each of the first and second transverse positions being determined along the width with an accuracy of + / -5 cm.

[0012] According to other advantageous and non-limiting characteristics of the invention, taken alone or in any technically feasible combination: • the measuring step involves at least one membrane potentiometer placed on the starting line and on the finishing line, along the width; • the membrane potentiometer is held on a rigid strip, which is arranged on the starting line (respectively on the finishing line), along the width; • each of the first and second transverse positions is determined over the width with a precision of + / -4cm, or even + / -3cm, + / -2cm, or even + / -1cm; • the -at least one- membrane potentiometer arranged on the starting line (respectively the finishing line) is connected to a microcontroller capable of transmitting information relating to the first transverse position (respectively to the second transverse position), via a wireless communication protocol; • the width of the starting line and / or the width of the finishing line is between 0.2m and 5m; • the starting line and the finish line are the same, the section of track or road defining a loop; • the first and second transverse positions are precisely time-stamped when measured; • the process involves one or more movements on the section of track or road by the cyclist, and includes for each movement: - a measure of the difference in kinetic energy of the cyclist between the finish line and the start line, - a measurement of the motive energy developed by the cyclist, if applicable, during his movement on the section between the start line and the finish line, - a direct or indirect measurement of the dynamic air pressure during the cyclist's movement on the section between the start line and the finish line, so as to plot a relationship linking the resistive force to the average dynamic air pressure, the mass of the cyclist being known and the difference in altitude between the starting line and the finishing line being determined from the first and second transverse positions; • the relationship linking the resistive force to the average dynamic air pressure is linear and we determine an aerodynamic drag surface, the directing coefficient of the line, and a rolling coefficient, proportional to the coordinate at the origin of the line.

[0013] The invention also relates to an apparatus for measuring a transverse position of passage of the cyclist on a starting or finishing line and its time stamping, comprising:

[0014] - a resistive membrane potentiometer placed on the start or finish line, the dimension of the potentiometer along a transverse axis being equal to a transverse extent or width of the start or finish line, the potentiometer comprising three pins and having a fixed resistance between a first pin and a third pin and a variable resistance between the second pin and a third pin, said variable resistance being proportional to the transverse position of passage of the cyclist along the dimension;

[0015] - a microcontroller to which the membrane resistive potentiometer is connected, the second pin of the resistive membrane potentiometer being connected to an analog input of the microcontroller allowing voltage variations representative of the transverse position of the cyclist to be read and timestamped.

[0016] Finally, the invention relates to another apparatus for measuring a transverse position of passage of the cyclist on a starting or finishing line and its time stamping, comprising:

[0017] - two resistive membrane potentiometers arranged parallel and side by side on the start or finish line, the dimension of each potentiometer along a transverse axis being equal to a transverse extent or width of the start or finish line, each potentiometer comprising three pins and having a fixed resistance between a first pin and a third pin and a variable resistance between the second pin and a third pin, said variable resistance being proportional to the transverse position of the cyclist along the dimension;

[0018] - a microcontroller to which the two resistive potentiometers are connected membrane, the second pin of the first resistive membrane potentiometer being connected to an analog input of the microcontroller for reading the transverse position of the cyclist's passage, the second pin of the second resistive membrane potentiometer being connected to an interrupt of the microcontroller so as to trigger the timestamp with an accuracy better than + / -100ms.

[0019] Advantageously, one or other of the aforementioned devices comprises wireless communication means for transmitting information relating to the transverse position of the cyclist and relating to its time stamp. BRIEF DESCRIPTION OF THE FIGURES

[0020] Other characteristics and advantages of the invention will emerge from the detailed description of the invention which follows with reference to the appended figures in which:

[0021] [Fig.l] [Fig.l] shows a diagram of the implementation of a method in accordance with the invention;

[0022] [Fig.2] [Fig.2] presents a graphical representation of the resistive force as a function of the dynamic air pressure, for 8 movements (8 points) made by a cyclist, on the section of track or road on a slope, between the start and finish lines, with different speeds, and without implementing the measurement of the first and second transverse positions of passage on said start and finish lines of the method according to the invention;

[0023] [Fig.3] [Fig.3] presents a graphical representation of the resistive force as a function of the dynamic air pressure, for the same 8 movements (8 points) made by a cyclist, on the section of track or road on a slope, between the start and finish lines, by applying the measurement of the first and second transverse positions of passage on said start and finish lines to correct the altitude information, in accordance with the present invention;

[0024] [Fig.4] [Fig.4] shows a table of values ​​of the aerodynamic drag surface CxS, for ten similar movements (same equipment configurations and position, similar movement speeds), determined without altitude correction and with altitude correction thanks to the determination of the first and second transverse passage positions in accordance with the invention;

[0025] [Fig.5a]

[0026] [Fig.5b] [Fig.5a] and [Fig.5b] show devices for measuring a transverse position of the cyclist crossing a start or finish line and its time stamping;

[0027] [Fig.6] [Fig.6] shows an example of the relationship between the value retrieved at the analog input of the microcontroller and the transverse position y detected by a membrane potentiometer.

[0028] The figures are schematic representations which, for the sake of readability, are not necessarily to scale. DETAILED DESCRIPTION OF THE INVENTION

[0029] The invention relates to a method for determining at least one friction parameter of a cyclist in real travel conditions, on a section of track or road with a slope. Friction parameter is any parameter that makes it possible to characterize the resistance experienced by the cyclist during his travel; this parameter can therefore in particular be an aerodynamic drag surface CxS, a rolling coefficient Cr, an overall friction force Fres that is applied to the cyclist during his travel, or even the work of this force per unit of time.

[0030] The section may in particular correspond to a portion (or the whole) of a velodrome track.

[0031] The section extends longitudinally from a starting line LD to a finishing line LA over a length L ([Fig.l]). Each of the starting lines LD and finishing lines LA extends transversely over a width 1. The cyclist is intended to move along a longitudinal axis, over the length L of the section; the width 1 extends along a transverse axis, substantially normal to the longitudinal axis.

[0032] Note that the starting line LD and the finishing line LA may possibly be confused, in particular when the section of track or road defines a loop.

[0033] The starting line LD and the finishing line LA may have different widths 1. However, for reasons of simplification and without this being limiting, a single width 1 will be considered in the remainder of this description for the starting lines LA and finishing lines LA.

[0034] Width 1 defines the traffic lane in which the cyclist must pass when carrying out a test in real travel conditions, on the section. Preferably, width 1 is between 0.2m and 5m.

[0035] In the context of the present invention, the section of track or road is considered to be on a slope from the moment there is a variation in altitude, between points on the starting line LD or between points on the finishing line LA, greater than or equal to 1 cm. This is for example the case when the traffic corridor extends over a width of between 15 cm and a few meters on a conventional velodrome track.

[0036] The method of the invention is based on an equation derived from the principle of conservation of energy.

[0037] The preparatory sequence described in document WO2022 / 074330A1, as well as the methods for determining the aerodynamic drag surface CxS and / or the rolling coefficient Cr can also be implemented in the method of the invention.

[0038] The method according to the invention nevertheless proposes a significant improvement, in that it comprises a step of measuring a position (along the transverse axis) of passage of the cyclist on the starting line LD (called first transverse position of passage PI) and a position (along the transverse axis) of passage of the cyclist on the finishing line LA (called second transverse position of passage P2). The position of the cyclist along the transverse axis is assimilated either to the position of the front wheel of his bicycle, or to the position of the rear wheel of his bicycle, or to the average of the positions of the front and rear wheels.

[0039] Each of the first PI and second P2 transverse positions is determined along the width 1 of each of the lines LD, LA with an accuracy of + / -5cm. Advantageously, the positions P1, P2 are determined with an accuracy of + / -4cm, or even + / -3cm, + / -2cm or even + / -1cm.

[0040] As will be explained in detail and illustrated later, the precise knowledge of the first PI and second P2 transverse positions gives access to the difference in altitude of the cyclist between the starting line LD and the finishing line LA. The applicant observed that an inaccuracy on this difference in altitude (elevation difference H) greatly affected the quality of the results and therefore the precision on the values ​​of the friction parameter(s) obtained.

[0041] Different measuring systems can be used to determine the first PI and second P2 transverse positions of passage on the starting lines LD and finishing lines LA.

[0042] Preferably, the step of measuring the first PI and second P2 transverse positions involves at least one membrane potentiometer arranged on the starting line LD and on the finishing line LA, along the width 1. The dimension D of the membrane potentiometer is chosen to extend over the entire width 1 of the starting lines LD and finishing lines LA (D = 1).

[0043] A resistive membrane potentiometer has three pins connected to electrodes extending over the dimension D ([Fig.5a]). The resistance Rn between a first and a third pin is fixed, while the resistance R23 between the second and third pins is variable and proportional to the transverse position y at which a pressing force will be applied to the potentiometer. The second pin of the potentiometer is connected to an analog input of a microcontroller making it possible to read and time-stamp voltage variations representative of the transverse position of the cyclist's passage.

[0044] It is thus understood that the passage of the cyclist over the membrane potentiometer placed on the starting line LD (or finishing line LA) will generate a given resistance value R23; said value is associated with a precise position on the potentiometer and therefore on the starting line LD (or finishing line LA); this precise position will correspond to the first PI (or second P2) transverse position of passage.

[0045] The membrane potentiometer can be directly placed on the ground of the section of track or road, or, advantageously, fixed on a rigid strip, easily removable and movable, which will be placed and temporarily immobilized on the starting line LD and on the finishing line LA, along the width 1.

[0046] The membrane potentiometer is connected to a microcontroller capable of transmitting information relating to the first PI and second P2 transverse positions by wired connection (to a ground computer, for example) or by a wireless communication protocol (to an on-board device, for example). The on-board device is adapted to measure different parameters such as the speed of the cyclist, the air speed or the dynamic air pressure, the power developed by the cyclist if necessary, during the movement of the cyclist on the section of track or road, the values ​​of which are necessary for the determination of the friction parameter(s).

[0047] Regardless of the type of measuring system (membrane potentiometer or other), it is important to note that a time lag in the reception of information relating to the first PI and second P2 transverse positions can also affect the quality of the results: it is therefore preferable that the transmission time of the information from the microcontroller to the embedded device is less than 100ms.

[0048] Of course, if it were envisaged to transmit information from the embedded device to the microcontroller, the same transmission time requirements would apply.

[0049] An alternative solution to this information transmission time constraint consists of time-stamp the passages of the cyclist on the starting line LD and on the finishing line LA, with an accuracy better than + / -100ms. This solution also requires setting up a clock synchronization mechanism between the clock of the microcontroller of the measurement system and the clock of the on-board device, also with an accuracy better than + / -100ms. This mechanism could rely on a master device, for example one of the microcontrollers connected to the measurement system (band with membrane potentiometer), capable of emitting on one of its output ports at periodic intervals, for example every minute, an electrical pulse perfectly synchronized with its clock.Other devices, by definition slaves (for example the device on board the bicycle and the microcontroller connected to the other measuring system), will be able to connect to this port and make the necessary adjustments to their own clock. The measuring system. (in particular, its microcontroller) must then be capable of transmitting by wired link (to a computer on the ground, for example) or by a wireless communication protocol (to the on-board device, for example), the information relating to the first PI and second P2 transverse positions and the timestamp of the cyclist's passage on the start LD and finish lines LA.

[0050] An apparatus for measuring a transverse position of passage of the cyclist on a start or finish line and its time stamping, can advantageously comprise two resistive membrane potentiometers (respectively named band 1 and band 2 on the diagram of [Fig.5b]) arranged parallel and side by side on the start line LD or finish line LA, the dimension D of each potentiometer along a transverse axis being equal to a transverse extent or width 1 of the line. As mentioned previously, each potentiometer comprises three pins and has a fixed resistance Rn between a first pin and a third pin and a variable resistance R23 between a second pin and the third pin, said variable resistance R23 being proportional to the transverse position y of passage of the cyclist along the dimension D (or width 1).

[0051] The apparatus also comprises a microcontroller to which the two resistive membrane potentiometers are connected, the second pin of the first resistive membrane potentiometer being connected to an analog input (to analog digital converter, ADC) of the microcontroller for reading the transverse position of the cyclist's passage, the second pin of the second resistive membrane potentiometer being connected to an interrupt of the microcontroller so as to trigger the time stamping with an accuracy better than + / -100ms.

[0052] The relationship between the analog input ADC and the transverse position is slightly non-linear. An example of this relationship for a pull-down resistor PD of 47kOhm, a resistor Rn of 20kOhm and a 12-bit converter (4096 values) is illustrated in [Fig.6]. Once the passage time and the value of the analog input ADC have been determined, the microcontroller proceeds to send the data, for example wirelessly, to the on-board device. The latter can then determine the altitude H(P1) at the first transverse passage position PI (and similarly H(P2)), using the following relationship:

[0053] [Equ.l] H(P1) =Psin(0)................................... -2 2,.f Rx 3

[0055] with D the length of the strip (which is equivalent to the width 1 of the starting line LD), RPD the pull-up resistor to ground, ADCvai the value recovered at the analog input ADC of the microcontroller, M the number of sampling bits of the converter analog digital, Rn the total resistance of the strip, 0 the track angle at the starting line LD. Note that this track angle, shown schematically in [Fig.l], may be different at the starting line LD (0D) and at the finishing line LA (0A).

[0056] As stated previously, the preparatory sequence and the methods for determining the aerodynamic drag surface CxS and / or the rolling coefficient Cr presented in document WO2022 / 074330A1 can be implemented in the method of the invention which aims, in addition, to precisely measure the difference in altitude (or gradient) between the cyclist's point of passage on the starting line LD and his point of passage on the finishing line LA, this thanks to the knowledge of the first PI and second P2 transverse positions, during movement on a section of track or road on a slope.

[0057] The present invention also proposes a protocol for testing and determining at least one friction parameter, different from those proposed by document WO2022074330A1.

[0058] Let us recall the fundamental equation of dynamics:

[0059] [Equ.2]

[0060] N? F = fm 4- — ) — = F 4- F • j 4- F , 4- F Zj 1 (111) dt x areo 1 weight 1 bearing ' x advancement

[0061] With

[0062] fluid friction force (friction force with air):

[0063] [Equ.3] F.™= -0.5 p CxS v air 2= ​​-P^ CxS

[0064] the force of gravity:

[0065] [Equ.4] Fpoids = - mgp

[0066] the dry friction force (or rolling force):

[0067] [Equ.5] Froujemen^ mg Cr

[0068] the forward force (force exerted by the cyclist on the pedals):

[0069] [Equ.6] F = Em " advancement L

[0070] In which: • vair, Pair are respectively the air speed and the dynamic air pressure, • m is the mass of the 4-bicycle cyclist pair, • g is the acceleration of gravity, • p = H / Lh is the slope of the road defined as the ratio between the difference in height H of the section (difference between the altitude H(P1) at the crossing of the line of departure LD and altitude H(P2) at the crossing of the finish line LA) and its length projected on a horizontal plane Lh, • Em is the motive energy produced by the cyclist, • L is the length of the path, • CxS is the aerodynamic drag surface of the cyclist on his bicycle, • Cr is the rolling coefficient, • I, the sum of the moments of inertia of the two wheels, and R, their radius.

[0071] From an energy point of view this gives:

[0072] [Equ.7]

[0073] / o2 Fd x = 2 w = Jo( m + i)^ dx

[0074] or,

[0075] [Equ.8] dx = Vdt

[0076] From where

[0077] [Equ.9] 100781 SW=^(m+^)Vdv=0.5(m+^) [WV^ 2 ]

[0079] With

[0080] Vfinai and Vini, respectively the speeds at the arrival and departure of the cyclist.

[0081] By breaking down the work generated by each force on a section, we obtain:

[0082] [Equ.10]

[0083] £w = Wres + Wweight + Wavanœment = 0.5 (m + £) [V^2-Vfinal2]

[0084] With

[0085] Wres the energy lost by aerodynamic friction and by rolling.

[0086] This can be expressed using the fluid friction parameters CxS (aerodynamic coefficient) and dry friction Cr (rolling coefficient):

[0087] [Equ.ll]

[0088] W res = W reSaero + Wres^^

[0089] = jL + jLm $ dx

[0090] w res = 4 CxS P air dx + mg C r L

[0091] Wweight = mgH

[0092] Wprogress Em

[0093] The variation of kinetic energy AEC can be defined as being equal to:

[0094] [Equ.12]

[0095] AE^O^m+^HW-V]

[0096] We thus obtain the following relationship between the height difference (or gradient) H and the rest of the parameters CxS, Cr, v and Pair:

[0097] [Equ.13]

[0098] A Ec— - Wres-ni gH+Em

[0099] Let us note Fres = Wres / L the average resistive force by aerodynamic friction and by rolling along the route on the section of track or road:

[0100] [Equ.14]

[0101] n _ -AEC- mg H+Em " res L

[0102] Assuming that CxS and Cr are constant, we can write the following relationship:

[0103] [Equ.15]

[0104] Fres= CxS (Pæj.)+m (j C,

[0105] With <pair>corresponding to the average dynamic air pressure along the course (between the starting line LD and the finishing line LA).

[0106] By precisely measuring AEC, Em, <pair>, and knowing beforehand m, H and L, it is possible to draw the relation Fres = f( <pair>) to determine the coefficients CxS and (mgCr), by linear regression.

[0107] The method for determining at least one friction parameter according to the present invention may therefore involve one or more movements on the section of track or road by the cyclist, between the starting line LD and the finishing line LA (or vice versa) and comprise for each movement:

[0108] 1) a measure of the difference in kinetic energy of the cyclist between the finish line LA and the starting line LD,

[0109] 2) a measurement of the driving energy developed by the cyclist, during his movement on the section between the starting line LD and the finishing line LA, except of course if there is no motive power because movement on the section is freewheeling,

[0110] 3) a direct or indirect measurement of the average dynamic air pressure during the movement of the cyclist on the section between the start line LD and the finish line LA.

[0111] When several movements are carried out, the measurements stated above make it possible to plot a linear relationship linking the resistive force Fres and the dynamic air pressure Pair, which makes it possible to determine the aerodynamic drag surface CxS, the directing coefficient of the straight line, and the rolling coefficient Cr, proportional to the coordinate at the origin of the straight line. The cyclist's movement speed varies with each movement, all other test conditions remaining identical (bicycle, cyclist's clothing and posture, properties of rolling...). Each point on the line Fres = f( <pair>) corresponds to a movement of the cyclist, at a given speed, therefore at a given average dynamic air pressure.

[0112] The measurement of the kinetic energy can be carried out using one or more magnets positioned on one of the wheels of the bicycle and a Hall effect magnetic switch positioned on an element of the frame or fork close to the passage of the magnet(s) and connected to an on-board electronic device capable of recording with an accuracy better than + / -100ms the electrical pulses tn at each passage of magnet n in front of the switch. In the case of a single magnet, prior knowledge of the mass m of the cyclist, the circumference C of the wheel on which the magnet is positioned and the inertia I of the wheels will make it possible to accurately estimate the kinetic energy at the average point n+N / 2 between the passages of magnet n and n+N using the following relationship:

[0113] [Equ.16]

[0114] ( R / \ '■O+N 0

[0115] With N a number of wheel revolutions, typically between 1 and 10, advantageously between 1 and 6.

[0116] The measurement of the driving energy developed by the cyclist may be based on the reading of a power sensor present on the cyclist's bicycle via an “ANT+” or “Bluetooth Low Energy” communication protocol.

[0117] The measurement of the dynamic air pressure will be made possible: - either indirectly from the ground speed, calculated between several wheel passages N, and thanks to the magnetic switch and knowledge of the air density p via the relationship:

[0118] [Equ.17] [0H9] p _ i / N*C \2 rair^N~ 2P\ /

[0120] assuming that the tests are carried out indoors without air movement relative to the ground; - either directly by a differential pressure sensor connected to a structure present on the front of the bicycle of the "Pitot probe" type having an air inlet sensitive to the total pressure and another sensitive to the static pressure. In this case, the dynamic pressure can be compensated so as to eliminate the air blocking factor induced by the presence of the cyclist.

[0121] In both cases, the average dynamic air pressure <pair>is obtained by averaging the Pair values ​​along the section.

[0122] [Fig.2] shows the results Fres = f( <pair>) for eight moves with different speeds, without correction of the difference in level H in equation [Equ.14], that is to say without use the first PI and second P2 transverse positions of passage of the cyclist on the start lines LD and finish lines LA.

[0123] The coefficient “R2” which reflects the quality of the linear regression is lower than on flat terrain without slopes (0.975 vs. 0.999 usually). The coefficients Cr and CxS cannot therefore be determined very precisely.

[0124] [Fig.3] shows the results Fres = f( <pair>) for these same eight movements, using the first PI and second P2 transverse positions of the cyclist passing on the starting lines LD and finishing lines LA to precisely determine the difference in level H. The linear regression is then perfect (coefficient close to 1) and we determine with very good precision a value of the aerodynamic drag surface, directing coefficient of the line Fres = f( <pair>).

[0125] The rolling coefficient is determined from the coordinate at the origin of said line which corresponds to the term mgCr, with m and g known.

[0126] Under the test conditions of the invention, that is to say by determining the first and second transverse positions of passage of the cyclist on the starting and finishing lines, we also note an excellent reproducibility of the value obtained from the aerodynamic drag surface CxS, for the different displacements (considering Cr known): the standard deviation is 0.9% whereas it is 5.4% without correction of the difference in level (see table in [Fig.4]).

[0127] Example of implementation:

[0128] The tests are carried out on an indoor velodrome track. The objective is to evaluate the friction parameters of a cyclist under given conditions (particular bicycle, clothing, helmet, posture).

[0129] The following steps are applied: a. Arrange two rigid strips, each equipped with a membrane potentiometer, along a starting line LD and a finishing line LA extending transversely over a width 1; these lines LD,LA are spaced longitudinally by approximately 20m (length L of the section) and positioned approximately on one of the two straight track segments (i.e. without bends) of the velodrome ([Fig.l]). b. Align the strips transversely with one of the velodrome height reference lines (black line, red line, Côte d'Azur, etc.) or with a floor slat or with a height reference given by an optical level. c. Measure the slope of the velodrome (with an inclinometer or an optical level) or have data relating to this slope, at the level of the line starting line LD and at the finish line LA, and save this value in the on-board device settings. d. Optionally synchronize the clocks between the device on board the bicycle and the microcontrollers on the ground (connected to the membrane potentiometers). e. Start a measurement sequence as described previously (steps 1), 2) and 3)). The air speed can be assumed to be equal to the ground speed and determined using the Hall effect magnetic switch. The parameters relating to the movement speed are time-stamped and recorded at each wheel revolution. f. Detect and optionally time-stamp the cyclist's passage on the LD starting line via the detection of a voltage change (membrane potentiometer connected to an analog input of the microcontroller) and / or via the detection of an interrupt on the microcontroller (membrane potentiometer directly connected to an "interrupt" input of the microcontroller). g. Capture information relating to the transverse position PI of the cyclist on the track as he passes over the starting line LD using the membrane potentiometer connected to the analog input of the microcontroller or, in the case where the membrane potentiometer is connected to the interrupt of the microcontroller, using a second membrane potentiometer connected to the analog input of the microcontroller (in this case, a device such as previously described, including two membrane potentiometers in parallel, may be used). Immediately after detecting the passage, the microcontroller reads the analog input and detects the maximum value reached in a time period of about fifty milliseconds. h. Transmit information relating to the first transverse position PI and possibly the timestamp of the passage on the starting line LD, to the on-board device, via “wifi” or “bluetooth”. i. Convert the information relating to the transverse position PI into the altitude of the cyclist at the time of his crossing the starting line LD using knowledge of the slope of the track at the starting line LD and the relationship between the position of the cyclist on the strip and the voltage at the terminals of the analog / digital converter of the microcontroller. This step can also be carried out before step h), by the microcontroller. j. Detect and optionally timestamp the cyclist's passage over the finish line LA (similar to step f). k. Capture information relating to the second transverse position P2 of the cyclist as he passes the finish line LA (similar to step g). 1. Transmit information relating to the second transverse position P2 and possibly the timestamp of the crossing of the finish line LA, to the on-board device (similar to step h). m. Convert transverse position data into altitude difference or elevation difference H (can be done either by the microcontroller connected to the membrane potentiometer or in the on-board device). n. Calculate the resistive force Fres associated with the measured elevation difference H (can be done in the on-board device) optionally using the timestamp data to best match the data measured by the on-board device on one side (kinetic energy and air pressure data), and the data measured at the bands on the other (altitudes H(P1), H(P2) or lateral position). o. Extract a value of aerodynamic coefficient CxS, or rolling coefficient Cr; and / or carry out several tests on the section, under the given conditions to construct a straight line connecting the resistive force Fres as a function of the average dynamic air pressure <pair>(each test being carried out at a different speed), and extract the slope coefficient of the curve (CxS) and the coordinate at the origin (mgCr), so as to deduce the friction parameters CxS and Cr, under the given conditions. p. Repeat steps a) to o), for new conditions to be tested (particular bicycle, clothing, helmet, posture).

[0130] The method according to the invention makes it possible to access in a simple and efficient manner the values ​​of friction parameters of a cyclist, in real conditions of movement; these values ​​are precise and the high reproducibility of the results makes it possible to evaluate in a few tests, over a very short distance, therefore in a short time, a large number of conditions (particular bicycle, clothing, helmet, posture).

[0131] Of course, the invention is not limited to the embodiments and examples described, and variant embodiments may be made without departing from the scope of the invention as defined by the claims.< / pair> < / pair> < / pair> < / pair> < / pair> < / pair> < / pair> < / pair> < / pair>

Claims

Claims

1. Method for determining at least one friction parameter of a cyclist in real travel conditions, on a section of track or road having a slope and extending longitudinally from a starting line (LD) to a finishing line (LA) over a length (L), each of the starting lines (LD) and finishing lines (LA) extending transversely over a width (1), the method being based on an equation derived from the principle of conservation of energy expressed as follows: AEC = -Wres -mgH + Em with AEC the variation of kinetic energy, Wres the energy lost by aerodynamic friction and by rolling on the section, m the mass of the cyclist-bicycle couple, g the acceleration of gravity, H the difference in level and Em the driving energy produced by the cyclist on the section, and being characterized in that: - it comprises a step of measuring a first transverse position of passage (PI) of the cyclist on the starting line (LD) and a second transverse position of passage (P2) of the cyclist on the finishing line (LA), each of the first and second transverse positions (P1, P2) being determined along the width (1) with an accuracy of + / -5cm, - the variation of kinetic energy (AEC) and the difference in level (H) are calculated between two positions: the first transverse position of passage (PI) and the second transverse position of passage (P2).

2. Method for determining at least one friction parameter according to the preceding claim, wherein the measuring step involves at least one membrane potentiometer arranged on the starting line (LD) and on the finishing line (LA), along the width (1).

3. Method for determining at least one friction parameter according to the preceding claim, wherein the membrane potentiometer is held on a rigid strip, which is arranged on the starting line (LD) and on the finishing line (LA), along the width (1).

4. Method for determining at least one friction parameter according to one of the preceding claims, in which each of the first (PI) and second (P2) transverse positions is determined over the width (1) with an accuracy of + / -4cm, or even + / -3cm, + / -2cm, or even + / -1cm.

5. Method for determining at least one friction parameter according to one of the three preceding claims, in which the -at least one- membrane potentiometer arranged on the starting line (LD) (respectively the finishing line (LA)) is connected to a microcontroller capable of transmitting information relating to the first transverse position (PI) (respectively to the second transverse position (P2)), via a wireless communication protocol!

6. 111. Method for determining at least one friction parameter according to one of the preceding claims, in which the width (1) of the starting line (LD) and / or the width (1) of the finishing line (LA) is between 0.2m and 5m.

7. Method for determining at least one friction parameter according to one of the preceding claims, in which the starting line (LD) and the finishing line (LA) are the same, the section of track or road defining a loop.

8. Method for determining at least one friction parameter according to one of the preceding claims, in which the first (PI) and the second (P2) transverse positions are time-stamped when they are measured.

9. Method for determining at least one friction parameter according to one of the preceding claims, involving one or more movements on the section of track or road by the cyclist, and comprising for each movement: - a measurement of the difference in kinetic energy of the cyclist between the finish line (LA) and the start line (LD), - a measurement of the driving energy developed by the cyclist, if applicable, during his movement on the section between the start line (LD) and the finish line (LA), - a direct or indirect measurement of the dynamic air pressure during the movement of the cyclist on the section between the start line (LD) and the finish line (LA), so as to plot a relationship linking a resistive force (Fres) to an average dynamic air pressure ( <pair>), the mass of the cyclist being known and the difference in altitude (H) between the starting line (LD) and the finishing line (LA) being determined from the first (PI) and second (P2) transverse positions.

10. Method for determining at least one friction parameter according to the preceding claim, in which the relationship linking the resistive force (Fres) to the average dynamic air pressure ( <pair>) is linear and we determine an aerodynamic drag surface (CxS), the directing coefficient of the line, and a rolling coefficient (Cr), proportional to the coordinate at the origin of the line.

11. Apparatus for measuring a transverse position (P1, P2) of the cyclist passing over a starting line (LD) or finishing line (LA) and its time stamp, intended to be implemented in a method for determining at least one friction parameter according to claim 8, comprising: - a resistive membrane potentiometer arranged on the starting line (LD) or finishing line (LA), the dimension (D) of the potentiometer along a transverse axis being equal to a transverse extent or width (1) of the starting line (LD) or finishing line (LA), the potentiometer comprising three pins and having a fixed resistance between a first pin and a third pin and a variable resistance between the second pin and a third pin, said variable resistance being proportional to the transverse position (y) of the cyclist passing along the dimension (D);- a microcontroller to which the resistive membrane potentiometer is connected, the second pin of the resistive membrane potentiometer being connected to an analog input of the microcontroller allowing voltage variations representative of the transverse position (P1, P2) of the cyclist's passage to be read and timestamped.;

12. Apparatus for measuring a transverse position of passage of the cyclist on a starting line (LD) or finishing line (LA) and its time stamp, intended to be implemented in a method for determining at least one friction parameter according to claim 8, comprising: - two resistive membrane potentiometers arranged parallel and side by side on the starting line (LD) or finishing line (LA), the dimension (D) of each potentiometer along a transverse axis being equal to a transverse extent or width (1) of the starting line (LD) or finishing line (LA), each potentiometer comprising three pins and having a fixed resistance between a first pin and a third pin and a variable resistance between the second pin and a third pin, said variable resistance being proportional to the transverse position (y) of the cyclist's passage along the dimension (D); - a microcontroller to which the two resistive membrane potentiometers are connected, the second pin of the first resistive membrane potentiometer being connected to an analog input of the microcontroller for reading the transverse position of the cyclist's passage, the second pin of the second resistive membrane potentiometer being connected to an interrupt of the microcontroller so as to trigger the timestamp with an accuracy better than + / -100ms.

13. Apparatus according to one of claims 11 and 12, comprising wireless communication means for transmitting information relating to the transverse position (P1, P2) of the cyclist's passage and relating to its time stamp.< / pair> < / pair>

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