GB2568885A

GB2568885A - Methods and apparatus for performance testing of human powered vehicles

Info

Publication number: GB2568885A
Application number: GB1719762.5A
Authority: GB
Inventors: James Webb Antony
Original assignee: Red Is Faster Ltd
Current assignee: Red Is Faster Ltd
Priority date: 2017-11-28
Filing date: 2017-11-28
Publication date: 2019-06-05
Anticipated expiration: 2037-11-28
Also published as: GB201719762D0; GB2568885B

Abstract

A pedal cycle sensor arrangement comprises a sensor mount 34 having a main mounting portion attached to a front fork leg 38 of the pedal cycle. An elongate sensor boom 50 projects forwardly from the main mounting portion and an air sensor member 52 is located at the end of the boom. The air sensor member 52 is held at a position proximal to the upper edge and the front edge of a front wheel of the pedal cycle so as to be in a region of free flowing air in use. A method of deriving actual elevation data for a course (14, figure 1) traversed by a HPV (12, figure 1) is also disclosed. Ambient air pressure is periodically measured at a fixed reference location (28. Figure 1) close to the course 14 and proximal (26, figure 1) to the HPV 12 as it traverses the course 14. The reference and HPV air pressure data for the same point in time during the run is used to determine the elevation of the course at that point in time. Additionally, a low-noise pressure sensor arrangement is also disclosed (60, figure 7) which has a pair of pressure sensors, each having a pressure sensing diaphragm. The sensors are arranged close to one another with their diaphragms in mechanical opposition and the outputs of the two sensors are averaged to produce an overall output.

Description

Technical Field of the Invention

The present invention relates to methods and apparatus for performance testing of human powered vehicles and their riders and in particular pedal cycles. The present invention relates in particular to a method and apparatus for determining the actual elevation profile of a course over which a vehicle is travelling; to a sensor mounting arrangement for mounting one or more sensors to a pedal cycle; and to a pressure sensor arrangement.

Background to the Invention

Competitive cyclists are constantly seeking to improve their performance and the performance of the equipment they use. Particular areas of concern are aerodynamic drag and mechanical friction, since lowering these leads to the goal of increased speed for the same power input. New equipment is frequently developed and riding techniques reviewed and developed (e.g. rider position) with a view to reducing at least one of aerodynamic drag and mechanical friction. However, the effects of equipment choices, setup and rider position in practice requires testing.

Whilst aerodynamic drag and mechanical friction are of particular interest to competitive cyclists, they are also of interest in relation to other human powered vehicles (ITPV) such as wheelchairs and the like.

The aerodynamic drag-area (CaA) of a HPV and rider combination is the product of its coefficient of drag and the effective cross sectional area of the combination. Determining CaA is a useful in assessing the benefits of changes in equipment design and rider position. A useful parameter for assessing tyre friction of the combination is to determine its coefficient of rolling resistance (C_rr).

CaA in particular can be accurately evaluated using a wind tunnel. However, commercial testing in a wind tunnel is expensive and typically requires an individual to travel to the location where testing is carried out. This may be out of reach for many, even professional athletes.

Various methods and apparatus have been developed to try to evaluate CaA and Cn- in the field using data collected from a HPV and rider as they travel about a course. For example, Robert Chung in a paper entitled “estimating CaA with a power meter” (version 2012) has described a method for evaluating CaA and Cn-using power input and speed data collected periodically as a rider travels over a course. The data is subsequently processed to construct a “virtual elevation profile” for the course as a function of the collected data for power, speed, mass, and air density using estimated values for CaA and Cn·. The virtual elevation profile is compared to the actual elevation profile for the course to see whether the estimates for CaA and Cn·, were good estimates. If the virtual elevation profile diverges from the actual elevation profile, new estimates for CaA and C_rr, are input and the analysis is re-run until a virtual elevation profile which conforms closely to the actual elevation profile is produced, indicating that the estimated values used for CaA and C_rr, are accurate.

US 2012/022125757 Al to Froncioni et al. discloses a development of the virtual elevation method which takes into account the yaw angle of the airflow at various points during each run. The vehicle is equipped with sensors for collecting timestamped values indicative of the vehicle speed, propulsion force, airflow speed and yaw angle of the airflow at various points during the run. The run data are then processed using successively refined hypotheses regarding the CxA (yaw) dependence to generate a plurality of elevation profiles for the travelled path with estimated values of CaA and C_rr. The generated elevation profiles are then evaluated based on available route elevation information to select a correct dependence of the aerodynamic drag-area upon the yaw angle of the airflow.

The ability to correlate a virtual elevation profile with the actual elevation profile is highly dependent on the data for the actual elevation profile of the course being accurate. Where accurate elevation data for a course is available this is not an issue. However, testing will often be carried out on courses for which reliable elevation data is not readily available. In this case, changes in elevation for the course have to be measured to produce an actual elevation profile. In existing systems, the actual elevation resolution and accuracy are often poor for this type of application. For example, it is known to obtain elevation values using GPS or barometric altimeters, but

GPS data is subject to subject to errors which are relatively large for the purposes of this application and barometric altimeters are subject to drift with changing atmospheric pressure.

It is desirable then to provide alternative methods and apparatus for determining the actual elevation profile of a course over which a vehicle travels which overcomes, or at least mitigates, the drawbacks of existing methods.

There is a need also for an alternative method of assessing performance of a human powered vehicle and its rider which overcomes, or at least mitigates, the drawbacks of existing methods.

The accuracy of the known methods for determining CaA and C_rr using data collected from a HPV and rider as they traverse a course is necessarily dependant on the accuracy of the data collected. The accuracy of this data can be affected by the properties of the sensors and other apparatus used to collect the data and is also affected by the positioning of the sensors on the vehicle.

There is then a further need for alternative apparatus which can be used to collect data for use in the known methods of assessing performance of a human powered vehicle and its rider which overcomes, or at least mitigates, the drawbacks of the existing apparatus.

There is a still further need for an alternative mounting arrangement for mounting sensors on a HPV, especially a pedal cycle, which overcomes, or at least mitigates, the drawbacks of existing mounting arrangements.

Known air pressure sensors use a mechanical diaphragm to detect changes in air pressure. However, the diaphragm can be subject external forces other than air pressure which gives rise to sensor “noise”. This is a particular issue for pressure sensors mounted to moving vehicles or which are otherwise subject to movement.

There is a need then for alternative air pressure sensor arrangements which overcome, or at least mitigate, the drawbacks of the known pressure sensor arrangements.

Summary of the Invention

According to a first aspect of the invention, there is provided a sensor arrangement for a pedal cycle, the sensor arrangement comprising a sensor mount having a main mounting portion attached to at least one front fork leg of the pedal cycle, an elongate sensor boom projecting forwardly from the main mounting portion and an air sensor member at a forward end of the boom, the air sensor member comprising at least part of an air sensor arrangement for detecting a property of ambient air in use, wherein the air sensor member is located at a position close to the height of an upper circumferential edge of a front wheel of the pedal cycle and close to a front circumferential edge of the front wheel.

The air sensor member may be located above the height of the upper circumferential edge of the front wheel and/or in front circumferential edge of the front wheel.

The pedal cycle may comprise handle bars and the air sensor member may be located below the height of the handle bars.

The air sensor member may comprise at least part of one or more of an air pressure sensor, an air speed sensor, and an air flow direction sensor. The air sensor member may be a housing in which said at least part of at least one or more of an air pressure sensor, an air speed sensor, and an air flow direction sensor is located. The air sensor member may comprise one or more inlet ducts for an air sensor such as a pitot probe.

The pedal cycle may be a bicycle.

In an embodiment the main mounting portion comprises a supporting strut extending along one side of the front wheel and which is attached to one of the fork legs of the pedal cycle, and a base portion at an upper end of the leg, the sensor boom projecting forwardly from the base portion. The base portion may extend laterally over the front wheel.

In an embodiment, the main mounting portion comprises a pair of said supporting struts spaced apart on opposite sides of the front wheel, each strut being attached to a respective one of the front fork legs, the struts being interconnected at an upper end by the base portion which bridges over the front wheel.

A lower end of the, or each, strut may be attached to a respective one of the front fork legs. In which case, the lower end of the, or each, strut may be secured to its respective fork leg by means of one or more self-locking ties.

A lower end of the, or each, strut may be mounted to an axle of the front wheel, a respective brace extending rearwardly from the, or each, strut and attached to a respective one of the front fork legs. In which case, the, or each, brace may be secured to its respective fork leg by means of one or more self-locking ties.

The base portion may comprise a second sensor member comprising one or more further sensors. The base portion may comprise a temperature sensor for detecting the temperature of the front tyre. The base portion may be in the form of a housing in which the one or more further sensors are at least partially located.

In accordance with a second aspect of the invention, there is provided a sensor mount for use in the sensor arrangement according to the first aspect of the invention, the sensor mount comprising a main mounting portion attachable to at least one front fork leg of a pedal cycle, an elongate sensor boom projecting forwardly from the main mounting portion and an air sensor member at a forward end of the boom, the air sensor member comprising at least part of a sensor arrangement for detecting a property of ambient air in use, wherein the sensor mount is configured in use when mounted to a pedal cycle to locate the air sensor member at a position close to the height of an upper circumferential edge of a front wheel of the pedal cycle and close to a front circumferential edge of the front wheel.

The sensor mount may be configured to locate the air sensor member above the height of an upper circumferential edge of the front wheel in use.

The air sensor member may comprise at least part of at least one of an air pressure sensor, an air speed sensor, and an air flow direction sensor. The air sensor member may be a housing in which said at least part of at least one of an air pressure sensor, an air speed sensor, and an air flow direction sensor is located. The air sensor member may comprise one or more inlet ducts for an air sensor such as a pitot probe.

In an embodiment, the main mounting portion comprises a supporting strut for extending along one side of a front wheel of a pedal cycle, the strut being attachable to one of the fork legs of a pedal cycle, and a base portion at an upper end of the leg, the sensor boom projecting forwardly from the base portion.

In an embodiment, the main mounting portion comprises a pair of said supporting struts spaced apart for location on opposite sides of the front wheel of a pedal cycle, each strut being attachable to a respective one of the front fork legs of a pedal cycle, the struts being interconnected at an upper end by the base portion which bridges over the front wheel.

A lower end of the, or each, strut may be attachable to a respective one of the front fork legs. In which case, the lower end of the, or each, strut may be adapted to be secured to a respective fork leg by means of one or more self-locking ties.

A lower end of the, or each, strut may be mountable to an axle of the front wheel of a pedal cycle, a respective brace extending rearwardly from the, or each, strut for attachment to a respective one of the front fork legs of a pedal cycle. In which case, the, or each, brace may be adapted to be secured to a respective fork leg by means of one or more self-locking ties.

In accordance with a third aspect of the invention, there is provided a method of sensing one or more parameters of ambient air proximal (close) to a pedal cycle whilst the pedal cycle is being ridden along a course, the method comprising mounting at least one air sensor for detecting a property of ambient air from at least one fork leg of the pedal cycle such that at least part of the at least one air sensor is located at a position proximal to the height of the upper circumferential edge of a front wheel of the pedal cycle and proximal to a front circumferential edge of the front wheel.

The method may comprise locating the air sensor member above the height of an upper circumferential edge of the front wheel.

The method may comprise locating said at least part of the at least one air sensor in a region of the ambient air which is substantially unaffected by the pedal cycle and its rider moving through the air.

The method may comprise locating at least part of the at least one air sensor in a region of the ambient air where the pressure of the air is not increased significantly as a result of the pedal cycle and its rider moving through the air.

In accordance with a fourth aspect of the invention, there is provided a method of determining the actual elevation profile of a course traversed by a human powered vehicle (HPV) in a run, the method comprising:

a. during the run, periodically detecting the ambient air pressure at a fixed reference location close to the course;

b. during the run, periodically detecting the ambient air pressure close to the HPV;

c. using the reference ambient air pressure detected in step a and the HPV ambient air pressure detected in step b for the same point in time during the run to determine the elevation of the HPV at that point in time;

d. repeating steps a to c for a number of different points in time during the run to determine the elevation of the HPV at those points in time and generating an elevation profile for the course from the determined elevation data.

The method may comprise recording timestamped values for the reference ambient pressure and the HPV ambient pressure detected periodically during the run, wherein the timestamps applied to the data are synchronised. The data may be analysed subsequent to the run and could be analysed at a remote location.

The reference ambient air pressure and the HPV ambient air pressure may be sampled are sampled at a rate of at least 1Hz, or at a rate of at least 2Hz, or at a rate of at least 4Hz, or at a rate of at least 6Hz, or at a rate of at least 8Hz, or at a rate of at least 10Hz. A high sampling rate allows higher resolution of the elevation data for the course

The method may comprise using any of a range of standard pressure to altitude equations to determine the elevation of the HPV from the reference ambient air pressure and the HPV air pressure data.

In one embodiment, the method comprises determining the elevation of the fixed reference location above mean seal level (MSL) and step c comprises:

e. from the elevation of the fixed reference location and the reference ambient air pressure for a given point in time during the run calculating the air pressure at MSL at that point in time;

f. from the air pressure at MSL calculated in step e and the HPV ambient air pressure for the same point in time during the run, determining the elevation of the HPV above the MSL at that point in time.

In an alternative embodiment, step c of the method comprises:

g. from the reference ambient air pressure and the HPV ambient air pressure for the same point in time during the run, determining the elevation of the HPV relative to the fixed reference location at that point in time.

This embodiment may also comprise determining the elevation of the fixed reference point above MSL and adding this to the elevation of the HPV relative to the fixed reference determined in step g to derive the elevation of the HPV above MSL at that point in time.

The method may comprise:

h. periodically detecting the ambient air pressure at a plurality of fixed reference locations spaced apart along the course during the run;

i. using air pressure data derived from one or more of the fixed reference locations at a given point in time during the run to determine the elevation of the HPV at that point in time, the reference air pressure data used being selected in dependence on the distance between the HPV and the various fixed reference locations at that point in time.

Step i may comprise determining the pressure at MSL from the ambient air pressure at each of the fixed reference locations at the given point in time and using the pressure at MSL derived from one or more of the fixed reference locations to determine the elevation of the HPV at that point in time

The air pressure data derived from the fixed reference location closest to the HPV at said point in time may be used to determine the elevation of the HPV. Alternatively, air pressure data derived from a plurality of the fixed reference locations may be used to determine the elevation of the HPV, the air pressure data from the plurality of fixed reference locations used being interpolated in dependence on the relative distances between the fixed reference locations and the HPV at the relevant point in time.

The method may comprise detecting the ambient air pressure at the, or each, fixed reference location proximal to the course using a reference unit located at the fixed reference location and detecting the ambient air pressure proximal to the HPV using a head unit mounted to the HPV, and recording the air pressure data from each of the reference unit(s) and head unit as a timestamped data set wherein the timestamping of the data is synchronised. The method may comprise recording the data locally in the respective reference unit and head unit, the units each having a clock for timestamping the recorded data and the method comprising synchronising the clocks of the reference unit and the head unit. Alternatively, the data may be transmitted from reference unit and/or the head unit to a remote data recorder.

The method may comprise using the virtual elevation method to derive values for CdA and Crr for the HPV and rider using the actual elevation profile derived in step d and other required data obtained from the HPV and rider during the run. The other data may be selected from the group comprising: ground speed/distance, air speed, power input, air density and system mass.

In accordance with a fifth aspect of the invention, there is provided apparatus for carrying out the method according to the fourth aspect of the invention, the apparatus comprising at least one reference unit for positioning at a fixed reference location along the course and a head unit for mounting on a HPV whilst traversing the course, each of the at least one reference unit and the head unit having an air pressure sensor for detecting ambient air pressure and processing means for periodically collecting air pressure data from its respective air pressure sensor.

The head unit may comprise means for sensing and periodically collecting other data required to determine CdA and Cn using the virtual elevation method. The head unit may comprise a sensor arrangement for detecting airspeed and air temperature. The head unit may also comprise a sensor arrangement for detecting any one or more of: air incident angle, wheel rotation, humidity position and input power from the rider.

The head unit and/or the reference unit may have a means for recording the data collected or means for transmitting this data to a remote data recorder.

Where the head unit and/or the reference unit has a means for recording the data collected, it may have a clock means and be configured to record the data sampled periodically during a run as a timestamped data set.

In accordance with a sixth aspect of the invention, there is provided a pressure sensor arrangement comprising a pair of pressure sensors, each pressure sensor having a pressure sensing diaphragm, the sensors being arranged proximal to one another with their diaphragms in mechanical opposition.

The outputs of the two sensors may be averaged to produce an overall output.

The sensors may be mounted to opposite sides of a common substrate, which substrate may be an ECB.

The pressure sensors may be mounted with their diaphragms aligned on a common axis.

The pressure sensor arrangement according to the sixth aspect of the invention may be incorporated into the sensor arrangement of the first aspect of the invention and/or into the air sensor member of the sensor mount in accordance with the second aspect of the invention. The pressure sensor arrangement according to the sixth aspect of the invention can be used to sense ambient air pressure in the method according to the fourth aspect of the invention and can be incorporated into or associated with either the reference unit or the head unit of the apparatus according to the fifth aspect of the invention. However, the pressure sensor arrangement according to the sixth aspect of the invention may be used in any application for sensing fluid pressure.

Detailed Description of the Invention

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

Figure 1	is a schematic representation of an arrangement for testing the performance of a human powered vehicle and rider traveling a course using apparatus and methods in accordance with various aspects of the invention;
Figure 2	is a graph illustrating plots of virtual and actual elevation against time for the course in Figure 1;
Figure 3	is a drawing illustrating a first method of determining the actual elevation of head unit on a human powered vehicle in accordance with an aspect of the invention;
Figure 4	is a drawing illustrating a second method of determining the actual elevation of a head unit on a human powered vehicle in accordance with an aspect of the invention;
Figure 5	is a schematic side view of a bicycle and rider illustrating the generation of a higher pressure region in the ambient air in front of rider and bicycle as they travel about the course of Figure 1;
Figure 6	is a side view of a bicycle and a first embodiment of a sensor arrangement in accordance with an aspect of the invention attached to the bicycle;
Figure 7	is a side view of a bicycle and a second embodiment of a sensor arrangement in accordance an aspect of the invention attached to the bicycle; and
Figure 8	is a schematic illustration of a pressure sensor in accordance with an aspect of the invention and which can be used as part of the apparatus and methods for testing the performance of certain aspects of a human

powered vehicle and rider in accordance with various aspects of the invention.

Aspects of the invention will now be described with reference to a method and apparatus for testing certain aspects of the performance of a cyclist riding a bicycle. Whilst the invention is considered to have particular application in testing for cyclists, especially competitive cyclists (including triathletes), the various aspects of the invention can be adapted for use in testing the performance of a range of human powered vehicles and riders including all types of pedal cycle and other human powered vehicles such as wheelchairs. The term “pedal cycle” as used herein should be understood as encompassing a wide range of pedalled vehicles not just bicycles and includes without limitation: bicycles, tricycles, recumbent bicycles and tricycles, and hand-powered cycles regardless of the number of wheels. The term “rider” is used herein to refer to the operator of any pedal cycle or other human powered vehicle including wheelchairs.

Figure 1 illustrates a cyclist 10 riding a bicycle 12 over a course 14. As previously discussed, values for CdA and Cn for the rider/bicycle combination can be derived from data collected periodically as they travel the course using the known virtual elevation method. The virtual elevation method will not be described in detail herein and the reader should refer to Robert Chung’s paper “estimating CdA with a power meter” (version 2012) and/or US 2012/022125757 Al to Froncioni et al. for further information if required. The contents of these documents are hereby incorporated in their entirety. However, briefly, for each run being analysed, values are input for the following five parameters:

Aerodynamic drag (Coefficient of drag x effective cross section) (CdA) - estimated; Coefficient of rolling resistance (Cn·) - estimated;

Drive system efficiency (η (Eta)) - estimated;

Total mass of cycle and rider (m) - typically measured before each run.

Local acceleration due to gravity (g) - this may also be measured.

These data together with the data collected or derived from the rider and bicycle periodically on the run form inputs to the following energy balance equation (equation 1):

AE_gpe= E_in _ ΔΕ_κε — ΔΕ_κε — ΔΕ_Αίτ — ΔΕ_ΚΚ

Where

Egpe is the gravitational potential energy

Ejn is the useful energy input by the rider during this time interval

Eke is the kinetic energy of the rider and cycle

EAir is the energy lost to air resistance (drag)

Err is the energy lost to rolling resistance

Any surplus or deficit in Egpe is assumed to be the result of a change in elevation from sample point to sample point. A surplus being indicative in a gain of elevation, a deficit indicative of a loss of elevation. The resulting gain or loss of elevation balances the equation by assuming that gravitational potential energy has been gained or lost. This change in elevation is evaluated at each sample point during the run and a graph drawn of the ‘virtual elevation profile’ of the cycle and rider over the duration of the run under analysis.

The virtual elevation profile generated is overlaid over the actual elevation profile for the course to see whether the estimates for CdA, Crr, and η were accurate. This is illustrated in Figure 2 in which the grey shaded area 16 indicates the actual elevation profile of the course and lines 18, 20, 22 indicate plots of a number of virtual elevation profiles generated using different estimated values for CdA, C_rr, and η. If the virtual elevation profile diverges from the actual elevation profile, as indicated by plots 18 and 20 in Figure 2, new estimates for CdA, Crr, and η are input and the analysis is re-run until a plot 22 which conforms closely to the actual elevation profile is produced, indicating that the estimated values used for CdA, Crr, and η are accurate. In Figure 2, elevation (vertical axis) is plotted against time (horizontal axis). Alternatively, elevation could be plotted against distance travelled along the course.

Typically, it has been found that η has little impact on the result and a reasonable estimate of say 0.97 will yield good results depending on the power meter in use.

If the course comprises a circuit returning to the same point, then the net change in elevation will be zero and estimated values of CaA and C_rr are selected that produce zero net elevation gain over each lap of the course. It is possible to have a number of CaA /C_rr pairs which result in a zero net elevation change. However, since the effects of CdA and C_rr are a square function of V_air, and linear of V_grOund respectively, it is possible to establish values that maximise the correlation between the virtual elevation profile and the actual elevation profile when the run includes phases of running at different speeds with Crr dominating at low speed and CaA dominating at higher speeds.

The data collected from the bicycle and rider as they travel the course will typically include:

Time (t);

Distance travelled (d);

Air pressure;

Instantaneous ground speed (Vair);

Instantaneous air speed (Vground);

Power input (Pin);

Air density (p (rho));

The data collected on the run is obtained from a number of sources including sensors and other instrumentation mounted on the bicycle and/or rider which are sampled periodically as the rider traverses the course. In the system according to an aspect of the present invention, the apparatus 24 used to carry out the method includes a head unit 26 mounted to the bicycle which collects and records at least some of the required data. The data is sampled periodically and is timestampcd. In the case of the power produced by the rider, this may alternatively be recorded separately on a cycle computer and synchronised with the data recorded in the head unit 26 via timestamps. Alternatively, data collected by the head unit 26 may be transmitted to a separate data recording unit such as a cycle computer or mobile phone.

The collected data is processed to produce a time-based data set and is analysed with a view to obtaining accurate values for CdA and C_rr using the virtual elevation method as discussed above.

As described so far, the method of determining CdA and Crr and the apparatus 24 used is largely conventional. In accordance with aspects of the invention a method and apparatus for deriving the actual elevation profile of the course will now be described.

The apparatus 24 additionally includes a reference unit 28 which is positioned at a fixed location in close proximity to the course during the run. The reference unit 28 contains or is operatively connected with sensors and instrumentation for collecting the following data, though not all the data listed below are essential to the method of the present invention:

Date and time;

Position (using GPS);

Elevation (using GPS);

Air Temperature;

Air Pressure; and

Air Relative humidity;

This reference unit data is sampled periodically during a run and is recorded and timestamped. The data may be recorded in the reference unit or it may be transmitted to a separate data recording unit such as a cycle computer or mobile.

The head unit 26 and the reference unit 28 operate independently and synchronised clocks are used for recording the sampled data against timestamps. Any suitable method for synchronising the clocks and or data collected can be adopted. For example, synchronisation can be achieved via:

• GPS signal;

* Sync at a point in time before or after use via infrared or RF communication;

• Intermittently via radio or infrared during use when the units are sufficiently close - for example when a rider passes the reference unit on each lap of a velodrome;

• Continuously via radio or infrared around the course.

In accordance with an aspect of the invention, ambient air pressure data from the HPV and the reference unit collected during the run is used to derive the actual elevation profile of the circuit using a differential pressure measurement technique. In accordance with this method, the elevation of the head unit Ehead at a given point in time during the run is calculated using the standard pressure-elevation equation from the air pressure at the same point in time collected by the head unit and the reference unit. By repeating this process for air pressure data recorded periodically during the run, an actual elevation profile of the course can be derived.

There are a number of ways in which the elevation Ehead of the head unit 26 can be calculated using the air pressure data from the head unit 26 and the reference unit 28 as will be understood by those skilled in the art. Two suitable methods will now be described. In the following methods, the actual elevation E_ref of the reference unit 28 is recorded. This may be obtained from known topographical data or taken from GPS data over time. Whilst elevation data from GPS is subject to error, if the reference unit 28 is at a fixed location for a period of time then reasonably accurate elevation data can be acquired using GPS. A GPS unit may be incorporated into the reference unit 28 or a separate GPS unit may be mounted to the reference unit to obtain the elevation of the reference unit.

In a first method illustrated in Figure 3, Mean Sea Level (MSL) is taken as “zero” elevation. The air pressure at MSL is calculated from the air pressure data from the reference unit 28 using the following equation, (equation 2):

₌ Pref msl /-E_Ref\ _e\ cT )

Where:

Pref = ambient air pressure at the fixed reference point where the reference unit is located;

Eref = the elevation of the reference unit;

c is a constant scalar value (typically 29.263).

T is air temperature in Kelvin (K)

The elevation of the head unit 26 above MSL is then calculated using the following equation (equation 3):

E_head = c.T.Log(^\ ''head'

Where:

Pmsi is the air pressure at MSL derived from equation 2;

Phead is the ambient air pressure proximal to the bicycle at the same point in time during the run collected by the head unit 26;

c is a constant scalar value (typically 29.263); and

T is air temperature in Kelvin (K).

In a second method as illustrated in Figure 4, the reference unit elevation Eref is take as “zero” elevation and the elevation of the head unit Ehead is derived from the following equation (equation 4):

Ehead = c- T- Log + E_ref '“head'

Where:

Phead = is the ambient air pressure proximal to the bicycle at the same point in time during the run collected by the head unit 26

Eref = elevation of the reference unit;

c is a constant scalar value (typically 29.263); and

T is air temperature in Kelvin (K).

The formulae given above are not the only formula that can be used for calculating elevation from measured air pressure as will be understood by those skilled in the art. At different altitudes, other formulae may be more accurate and can be adopted.

In the present application, absolute accuracy in determining the elevation of the head unit or bicycle is not critical, what is required are changes in elevation along the course and repeatability of the measurement.

The use of a differential pressure measurement technique incorporating air pressure data from a fixed reference location and air pressure data from the bicycle removes errors that could be caused by atmospheric pressure changes over time, and so increases precision of the actual elevation data over the use of GPS or standard barometric altimeter mounted on the bicycle.

The accuracy of the elevation data is significantly improved by the use of lownoise high-resolution air pressure sensors and high frequency sampling of the data in both the reference and head units. In a preferred embodiment, the data is sampled at a rate of 1Hz or more in both the head unit and the reference unit. The sampling rate may be as high as 10Hz or more. The high resolution of the measurements means that the elevation resolution for the actual elevation profile can be much higher than provided by GPS, standard barometric or combined GPS/Barometric systems.

The apparatus and methods in accordance with the present invention can accommodate a number of head units 26 sharing the same reference unit 28. This enables a number of bicycles and riders to undergo performance testing at the same time. The data collected by each head unit 26 is recorded and timestamped in a synchronised manner with the data collected by the reference unit 28 for later analysis.

It is also possible to use multiple reference units 28 located at different positions along a route with one or more head units 26. This may be desirable to improve the accuracy of the elevation data by compensating for changes in the local air pressure over the length of the course. Where more than one reference unit 28 is used, each reference unit will operate independently of the others but the timestamping of the data from all the reference units 28 and head units 26 will be synchronised. When analysing the recorded data, the location of the various reference units 28 relative to the bicycle and rider at any given time during the run can be used to determine which reference unit or units are best to use for the reference data. For example, in the case where 2 reference units are in use (28A and 28B), with a distance to the cycle and calculated MSL pressures for the two units of D28A, D28B and Pmsl28a, Pmsl28b respectively, an estimate for MSL pressure Pmsl for use in calculating the head unit elevation may be derived using linear interpolation in accordance with the following equation (equation 5):

_n _ _n , (D28A ( PmSL2SB ~ ?MSL28a) “mSL — LMSL28A + I 5 \ + ^υ28Β

Where:

Pmsl28a the pressure at MSL derived from the ambient reference air pressure at reference unit A;

Pmsl28b ~ the pressure at MSL derived from the ambient reference air pressure at reference unit B;

D28a= distance between reference unit A and the cycle; and

D28B = distance between reference unit B and the cycle.

The interpolated value for Pmsl derived using equation 5 can be input into equation 3 above to determine the elevation of the head unit Ehead.

Other interpolation schemes can be used, and the model will vary with the number of reference units available.

The system could source this data from a crowd of reference units including suitably equipped smartphones or IOT devices.

The head unit 26 and reference unit 28 each have a processing means for processing data from the sensors in accordance with programmed algorithms. In one embodiment the head unit 26 and reference unit 28 each have memory for storing the data and the units 26, 28 may also have means for transferring the stored data for subsequent processing at a remote location. The data may be transferred wirelessly or by means of a wired connection or the data may be stored on a removable memory device. In an alternative embodiment, the data collected by the head unit 26 and/or the reference unit is transmitted to a separate data recording unit such as a cycle computer or mobile phone. In this case, the head unit 26 and/or reference unit will have suitable means for transmitting the data. In a further alternative embodiment, the data may be processed contemporaneously during a run in order to provide an output. In this case the data may be processed in one of the head unit or a reference unit or in a separate computing device with arrangements made to transfer data between the units as required wirelessly and a suitable display being provided to display the results of the analysis. In this case, the system would process all the data collected to provide values for CdA and Crr utilising the actual elevation data for the course derived in accordance with this aspect of the invention. The head unit 26 will typically comprise sensor means for collecting other data required to derive CdA and C_n values using the virtual elevation method such as ground speed/distance, air speed, power input. Air density and system mass may also be recorded. The power input data could though be obtained using a separate cycle computer and the data synchronised.

An important consideration in obtaining data for use in the determining the elevation profile of the course as well as for use in the virtual elevation method of determining CdA and C_rr is the placement and mounting of the required sensors on the bicycle. Typically, sensors for recording at least air speed and air pressure are mounted on the bicycle. In some cases, air direction is also measured. The placement of air sensors for measuring these properties of the ambient air is important as it can affect the accuracy of the data obtained. As illustrated in Figure 5, a higher pressure region 30 is generated in the air in front of a rider 10 and bicycle 12, particularly when travelling at relatively high speeds. If the air flow and/or air pressure sensors are located within this higher pressure region, the reading provided may not be accurate and will be affected by changes in the speed of the bicycle, ft has though been found that there is a region 32 just above and close to the front of the front wheel of a bicycle where the air is free flowing and where it is preferred to place the air sensors/air sensor inlets in order to obtain more accurate and/or reliable data.

Figures 6 and 7 illustrate two embodiments of a system for mounting sensors to a bicycle 12. The mounting system is particularly suitable for mounting sensors for detecting at least one property of the atmospheric air, such as air pressure, air speed and/or air flow direction and may be, or be part of, the head unit 26 used in the method for determining the actual elevation profile of a course as described above.

Referring initially to Figure 6, in a first embodiment the mounting system includes a sensor mount 34 having a main mounting portion comprising a pair of cantilevered struts 36 which are each attached at a distal/lower end to a respective one of the front fork legs 3 8 of the bicycle 12 on either side of the front wheel 42. Only one of the struts 36 can be seen in Figure 6 but it will be appreciated that the other strut is a mirror image of the one shown. The struts 36 can be attached to the front fork legs 38 by any suitable method. In one suitable arrangement as shown, each strut 36 is held in place by means of self-locking plastic ties 44 such as are typically used for securing cables. As shown, two ties 44 can be used to secure each strut to its respective fork leg. This method of attaching the sensor mount 34 to the fork legs 38 is very adaptable as it is able to accommodate wide range of different sizes and shape of fork leg. However, other suitable means of attaching the sensor mount 34 to each fork leg 38 can be used, such as by means of a clamp mechanism or the like.

The struts 36 each have a first region 36a that projects forwardly from their respective fork leg, and a second region 36b that projects upwardly and slightly forwardly towards the outer circumference of the tyre 46 of the front wheel. The two struts are connected together at their upper ends by a base portion 48 that extends across the wheel, spaced from but in relatively close proximity to the outer circumference of tyre 46 in front of the forks. A sensor boom 50 projects forwardly from the base portion 48 and an air sensor member 52 is located at the forward end of the sensor boom. The air sensor member 52 incorporates at least part of an air sensor arrangement for detecting a property of the ambient atmospheric air. One or more air sensors (not shown) for detecting properties of the atmospheric air are located within or mounted to the air sensor member 52. Typically the air sensors will include any one or more of an air pressure sensor, an air speed sensor, or an air flow direction sensor. The air sensor member 52 alternative or in addition comprise an inlet for an air sensor. For example, a pitot probe may be incorporated into the sensor mount 34 and the air sensor member 52 may have one or more ports for feeding air pressure via tubing to another part of the mount 34 housing the sensors.

The sensor mount 34 is configured to position the air sensor member 52 within the preferred region 32 in front of and just above the front wheel where the air is relatively free flowing helping to improve the accuracy/reliability of the air data collected. Whilst the air sensor member 52 is primarily intended to position sensors (or inlets to sensors) for collecting data related to the air, sensors for other purposes could also be housed in or mounted on the air sensor member 52. It is expected that the air sensor member will usually be located in-line with the front wheel but it could be offset to one side.

The base portion 48 and or one or both struts 36 can be used to mount additional sensors and components not required in the free-flowing air region. This could include odometer and temperature sensors. For example, the base portion 48 can be formed as a second sensor member and could house further sensors such as a tyre temperature sensor, whilst means for detecting wheel rotations could be mounted to one or both struts.

The sensor mount 34 can be made of any suitable material or materials provided it is sufficiently rigid as to stably support the sensors in the desired location without undue movement in use. The sensor mount 34 could be made of metallic materials such as steel or aluminium, or polymeric materials, or composite materials, for example. The mounting 34 provides a stable fixed location for a range of sensors including accelerometers and gyroscopes which reduces errors resulting from movement of such sensors.

Figure 7 illustrates a modified embodiment of the sensor mount 34’ in which the distal/lower ends of the struts 36’ are mounted to the front wheel hub 54. Each strut 36’ has a brace 56 which projects rearwardly for engagement with a respective fork leg 3 8 and is secured to the fork leg by means of a self-locking tie 44. Otherwise, the sensor mount 34’ according to the second embodiment is constructed and used substantially in the same manner as the first embodiment 34 and it comprises a base member 48’ that can be used as a second sensor member, a sensor boom 50’ and air sensor member 52’ at the forward end of the boom 50’.

In addition to positioning the air sensors and/or air sensor inlets in the region of free flowing air 32, the sensor mount 34, 34’ has the advantage that if the handlebars or rider’s hand position are adjusted during testing, the air sensors are much less affected than would be the case if the sensor mount was attached to the handlebars or the air sensors/inlets located closer to the front of the bicycle.

The sensor mount 34, 34’, could take different forms from those shown in Figures 6 and 7 but is preferably mounted to at least one of the fork legs. If mounted to only one fork leg, the sensor mount may have only one strut 36, 36’. The sensor mount 34, 34’ can be adapted to use fixed features on the front fork such as brake mountings or the front wheel axle to support itself. The sensor mount 34, 34’ may use a part permanently attached to the front fork (for example with adhesive) to provide support. The adhered part may act as a datum when re-mounting the system to the cycle. The sensor mount 34, 34’ may include one or more articulated joints to allow for alignment on different cycles.

The sensor members (s) 48, 52 may be aligned with each other or offset.

The design of the sensor mount 34, 34’ is such that additional aerodynamic drag and interference with the airflow is minimised.

Whilst the sensor mount 34, 34’ has been described for use with a bicycle, the principles can be adapted for mounting sensors to other types of pedal cycle which have a front wheel mounted in a front fork.

In accordance with a further aspect of the invention, a reduced noise air pressure sensor arrangement 60 will now be described with reference to Figure 8. Because the air pressure sensor arrangement 60 has been developed to reduce sensor noise it is capable of providing more accurate air pressure data than some known air pressure sensor arrangements. The air pressure sensor arrangement 60 is particularly suitable for use in mounting on a bicycle or other HPV for detecting air pressure for use in the method of determining the actual elevation profile of a course traversed by a HPV and rider as described above and can be accommodated in the air sensor member 52, 52’ of the sensor mount 34, 34’ as also described above. However, the air pressure sensor arrangement 60 can be adopted for use in any application in which detection of ambient air pressure is required.

The air pressure sensor arrangement 60 uses a pair of air pressure sensors A, B instead of a single sensor as is normally used. The two sensors A, B each have a sensing diaphragm and they are arranged so that their diaphragms are in mechanical opposition. The diaphragms of each sensor A, B are subject to atmospheric pressure P_atm and external forces causing an apparent error pressure P_err. The external forces might include inertial forces acting on the diaphragms if the sensor arrangement 60 is moved, for example. However, because the diaphragms are arranged in mechanism opposition, the external forces will operate in opposite relative directions on the diaphragms. The pressure measurement which is the output of the sensor arrangement P_out is the average of the pressure measurements of the two sensors A, B and is calculated using the following equation (equation 6):

_P_A + P_B ^rout ~ 2 _ (Patm T Perr) + (Patm Perr) _ Patm T Patm ~ 2

Because the diaphragms of the two sensors A, B are in mechanical opposition, the arrangement automatically compensates for any external forces applied to the diaphragms which are moved in opposite directions by such forces. This is particularly beneficial for a sensor arrangement mounted to a bicycle or other moving vehicle to sense air pressure data during a run, as it reduces sensor noise caused by moment of the vehicle and/or rider. The sensors A, B may be mounted on opposite sides of a common substrate 62 as illustrated. The pressure sensors may aligned on a common axis but this is not essential. Conveniently, the common substrate 62 is an electronic circuit board (ECB). However, this is not essential and the two sensors A, B could be mounted to any suitable substrate or indeed to separate substrates, though they should be positioned in close proximity. The sensors A, B could be facing outwardly away from one another as illustrated or they could face towards each other.

The reduced noise pressure sensor arrangement 60, the pressure sensor mounting arrangement 34, 34’, and the differential pressure method of determining the actual elevation profile of a course in accordance with various aspects of the invention can be used in combination to produce actual elevation data for a course traversed by a bicycle and rider which is more accurate and more reliable that that provided by the 10 known methods. This is particularly so where a high sampling rate is used. However, each of the various aspects can be used independently of the others.

The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.

Claims

1. A sensor arrangement for a pedal cycle, the sensor arrangement comprising a sensor mount having a main mounting portion attached to at least one front fork leg of the pedal cycle, an elongate sensor boom projecting forwardly from the main mounting portion and an air sensor member at a forward end of the boom, the air sensor member comprising at least part of a sensor arrangement for detecting a property of ambient air in use, wherein the air sensor member is located at a position proximal to the height of an upper circumferential edge of a front wheel of the pedal cycle and proximal to a front circumferential edge of the front wheel.

2. A sensor arrangement as claimed in claim 1, wherein the main mounting portion comprises a supporting strut extending along one side of the front wheel and which is attached to one of the fork legs of the pedal cycle, and a base portion at an upper end of the leg, the sensor boom projecting forwardly from the base portion.

3. A sensor arrangement as claimed in claim 2, wherein the main mounting portion comprises a pair of said supporting struts spaced apart on opposite sides of the front wheel, each strut being attached to a respective one of the front fork legs, the struts being interconnected at an upper end by the base portion which bridges over the front wheel.

4. A sensor arrangement as claimed in any one of claims 1 to 3, wherein a lower end of the, or each, strut is attached to a respective one of the front fork legs.

5. A sensor arrangement as claimed in claim 4, wherein the lower end of the, or each, strut is secured to its respective fork leg by means of one or more selflocking ties.

6. A sensor mounting arrangement as claimed in any one of claims 1 to 3, wherein a lower end of the, or each, strut is mounted to an axle of the front wheel, a respective brace extending rearwardly from the, or each, strut and attached to a respective one of the front fork fegs.

7. A sensor arrangement as claimed in claim 6, wherein the, or each, brace is secured to its respective fork leg by means of one or more self-locking ties.

8. A sensor arrangement as claimed in claim 2 or claims 3, wherein the base portion comprises a second sensor member comprising one or more sensors.

9. A sensor arrangement as claimed in claim 8, wherein the base portion comprises a temperature sensor for detecting the temperature of the front tyre.

10. A sensor mount for use in the sensor arrangement of any one of claims 1 to 9, the sensor mount comprising a main mounting portion attachable to at least one front fork leg of a pedal cycle, an elongate sensor boom projecting forwardly horn the main mounting portion and an air sensor member at a forward end of the boom, the air sensor member at least part of a sensor arrangement for detecting a property of ambient air in use, wherein the sensor mount is configured in use when mounted to a pedal cycle to locate the air sensor member at a position proximal to the height of an upper circumferential edge of a front wheel of the pedal cycle and proximal to a front circumferential edge of the front wheel.

11. A method of sensing one or more parameters of ambient air proximal to a pedal cycle whilst the pedal cycle is being ridden along a course, the method comprising mounting an air sensor arrangement for detecting a property of ambient air from at least one fork leg of the pedal cycle such that at least part of the air sensor arrangement is located at a position proximal to the height of an upper circumferential edge of a front wheel of the pedal cycle and proximal to a front circumferential edge of the front wheel.

12. A method as claimed in claim 11, where the at least a part of an air sensor arrangement is located in a region of the ambient air which is substantially unaffected by the pedal cycle and its rider moving through the air.

13. A method as claimed in claim 11, where the at least a part of an air sensor one arrangement is located in a region of the ambient air where the pressure of the air is not increased significantly as a result of the pedal cycle and its rider moving through the air.

14. A method of determining the actual elevation profile of a course traversed by a human powered vehicle (HPV) in run, the method comprising:

a. during the run, periodically detecting the ambient air pressure at a fixed reference location to the course;

b. during the run, periodically detecting the ambient air pressure proximal to the HPV;

15. A method as claimed in claim 14, wherein the method comprises recording timestamped values for the reference ambient pressure and the HPV ambient pressure detected periodically during the run, wherein the timestamps applied to the data are synchronised.

16. A method as claimed in claim 14 or claim 15, wherein the reference ambient air pressure and the HPV ambient air pressure are sampled at a rate of at least 1Hz, or at a rate of at least 2Hz, or at a rate of at least 4Hz, or at a rate of at least 6Hz, or at a rate of at least 8Hz, or at a rate of at least 10Hz.

17. A method as claimed in any one of claims 14 to 16, wherein the method comprises determining the elevation of the fixed reference location above mean seal level (MSL) and step c comprises:

18. A method as claimed in any one of claims 14 to 16, wherein step c of the method comprises:

19. A method as claimed in claim 18, the method comprising determining the elevation of the fixed reference point above MSL and adding this to the elevation of the HPV relative to the fixed reference determined in step g to derive the elevation of the HPV above MSL at that point in time.

20. A method as claimed in any one of claims 14 to 19, the method comprising;

i. determining the elevation of the HPV at a point in time during the run based on air pressure data derived from one or more of the fixed reference locations for a given point in time, the air pressure data used being selected in dependence on the distance between the HPV and the various fixed reference locations at that point in time.

21. A method as claimed in claim 20, wherein air pressure data derived from the fixed reference location closest to the HPV at said point in time is used to determine the elevation of the HPV.

22. A method as claimed in claim 20, wherein air pressure data derived from a plurality of the fixed reference locations is used to determine the elevation of the HPV, the air pressure data derived from the plurality of fixed reference locations being interpolated in dependance on the relative distances between the fixed reference locations and the HPV at the relevant point in time.

23. A method as claimed in any one of claims 14 to 22, the method comprising detecting the ambient air pressure at the, or each, fixed reference location proximal to the course using a reference unit located at the fixed reference location and detecting the ambient air pressure to the HPV in a head unit mounted to the HPV, and recording the data from each of the reference unit(s) and the head unit as a timestamped data set, wherein the timestamping of the various sets of data is synchronised.

24. Apparatus for carrying out the method of any one of claims 14 to 23, the apparatus comprising at least one reference unit for positioning at a fixed reference location along the course and a head unit for mounting on a pedal cycle whilst traversing the course, each of the at least one reference unit and the head unit having an air pressure sensor for detecting ambient air pressure and processing means for periodically collecting air pressure data from its respective air pressure sensor.

25. Apparatus as claimed in claim 24, wherein the head unit and/or the reference unit has a means for recording the air pressure data collected or means for transmitting this data to a remote data recorder.

26. Apparatus as claimed in claim 25, wherein the head unit and/or the reference unit has a means for recording the air pressure data collected and a clock means, the head unit and/or the reference unit being configured to record ambient air pressure data sampled periodically during a run as a timestamped data set.

27. A pressure sensor arrangement comprising a pair of pressure sensors, each pressure sensor having a pressure sensing diaphragm, the sensors being arranged proximal to one another with their diaphragms in mechanical opposition.

28. A pressure sensor arrangement as claimed in claim 27, wherein the outputs of the two sensors are averaged to produce an overall output.

29. A pressure sensor arrangement as claimed in claim 27 or claim 28, wherein the sensors are mounted to opposite sides of a common substrate.

30. A pressure sensor arrangement as claimed in claim 29, wherein the sensors are mounted on opposite sides of an ECB.