WO2017157604A1

WO2017157604A1 - Device and method for determining runner stride parameters

Info

Publication number: WO2017157604A1
Application number: PCT/EP2017/053423
Authority: WO
Inventors: Léa VAUCHER; Alexandre Briot
Original assignee: Parrot Drones
Priority date: 2016-03-17
Filing date: 2017-02-15
Publication date: 2017-09-21
Also published as: FR3048868A1

Abstract

The device comprises an accelerometer able to deliver a signal indicating the vertical acceleration of an upper anatomical region of a runner and a computational circuit, the computational circuit being configured to determine a start-of-flight time from a slope (D2) of the variation in the vertical-acceleration signal and to determine a time-of-flight from a datum (PV, P4) obtained by integrating the vertical acceleration.

Description

Device and method for its determination

of crazy parameters of a run

The present invention generally relates to systems and methods for determining sport exercise parameters.

It relates more specifically to a device and a method for determining the parameters of a stride of a runner.

The US 2013/0190657 A1 and US 6 018 705 A describe such devices provided with accelerometric sensors placed at the level of the belt, the ankle or the foot of the user, allowing to derive in real time a certain amount of information. which are useful for him when he walks or when he runs.

In addition, manufacturers of leisure equipment such as headphones adapted to sports practice are now seeking to enhance the functionality of such headphones beyond the mere listening of music. Thus, for example, the Zik Sport helmet proposed by the Applicant makes it possible to provide the user, through an appropriate user interface in communication with the helmet, physiological parameters and parameters relating to the race.

It is known to equip such helmets with motion sensors, typically comprising an inertial unit equipped with an accelerometer and a gyrometer, and means for processing the signals delivered by these sensors in order to derive information relating to the stroke, and in particular the rate (number of strides per minute) and the vertical oscillation (amplitude of the rebound).

The WO 2016/029803 A1 describes such a helmet with accelerometric sensors to determine various data of interest to a user during walking or running.

Obtaining other data such as ground contact time or flight time are also desired.

In principle, the duration of ground contact DurationContactSol is defined from the flight time DurationVol and the duration of a stride DurationFolded by the following relation:

DurationContactSol = DurationFlow - DurationFly A difficulty in trying to determine this time accurately is that it is necessary to know the precise trajectories of several points of the feet, so as to establish the instants of beginning and end of contact of the feet with the ground , and deduce the duration of contact. In the case where one seeks to make this determination with a single equipment worn for example at the head (typically a headphone), without instrumentation feet, it is obvious that this information is not available.

The present invention thus aims, from the only data of motion sensors available at a location of the body away from the feet, and typically the head of the user, to deduce from these data precise information relating to the moments at which the feet leave the ground and find the ground.

To this end, the invention proposes, in a first aspect, a device for determining stride parameters of a running race, this device comprising in a manner known in itself, in particular according to US 2013/0190657 A1. above, an accelerometer capable of providing a vertical acceleration signal of an upper anatomical region of a runner, and a flight time calculating circuit from the vertical acceleration signal.

Typically, the flight time calculating circuit is configured to: i) determine an instant of flight start from an evolution slope of the vertical acceleration signal and a predetermined acceleration value, and ii) determining a flight duration from an information obtained by integrating the vertical acceleration, and the start of flight time.

This device advantageously but optionally comprises the following additional features, taken individually or in any combination that the skilled person will apprehend as being technically compatible:

- The calculation circuit is able to determine a flight duration from a vertical position information obtained by double integration of the vertical acceleration signal; the calculation circuit is capable of determining a flight duration from the instant of the beginning of flight and a moment of vertical position of greater altitude;

the flight time is determined to be twice the difference between the two instants above;

the start time of flight is determined as an intersection between a straight line having said slope of evolution of the vertical acceleration signal with a straight line representative of a predetermined acceleration value;

said predetermined acceleration value is the acceleration of gravity;

- the device is subject to the movements of the runner's head.

It is also proposed according to the invention an audio headset, characterized in that it comprises a device as defined above.

In another aspect, there is provided a method implemented by a computing circuit for determining stride parameters of a running from a vertical acceleration signal of an upper anatomical region of a runner provided by an accelerometer.

This method is characterized by the steps of: i) determining a start time of flight from an evolution slope of the vertical acceleration signal and a predetermined acceleration value, and ii) determining a duration flight from information obtained by integrating the vertical acceleration, and the moment of flight start.

Additional advantageous but optional features of this method are the counterparts of those of the device, expressed above.

0

An embodiment of the present invention will now be described with reference to the accompanying drawings in which the same references designate identical or functionally similar elements from one figure to another.

Figure 1 is a perspective view of an exemplary audio headphone capable of housing a device according to the invention and to implement the corresponding method. Figure 2 illustrates an example of a vertical acceleration curve of a subject collected at the subject's head as he runs.

Figure 3 illustrates for comparison a vertical acceleration curve during the race, collected at the bust, and a vertical acceleration curve during the same race, collected at the head.

FIG. 4 graphically illustrates, on the basis of curves of the type of those of FIGS. 2 and 3, a basic approach for estimating flight time with accelerometric information collected at the head.

Figure 5 graphically illustrates an improved approach to making this estimate.

FIG. 6 is a block diagram of the various steps of a method for calculating the estimated flight time performed within the helmet of FIG. 1.

An exemplary embodiment of the invention will now be described.

In FIG. 1, the reference 10 designates in a general manner a helmet equipped with a processing device for determining flight duration according to the invention, a helmet which comprises two earphones 12 joined by a connecting element comprising a central arch 14 and Two branches 16. The headphones 12 are for example intra-auricular or intracoque type. The two branches 16 with their earphones 12 are similar and symmetrical. Each has at its proximal end a link articulated to the central arch 14. On the distal side 22, each branch 16 carries an earpiece 12. On the other hand, the median region of each branch 16 supports a housing 40.

Each box 40 contains various electrical or electronic elements, for example one or more printed circuit boards 50 in one of the boxes, and a rechargeable battery 52 in the other box, the two boxes being joined via an electrical connection (not shown ) running through the central arch 14. One of the housings 40 (here the housing housing the printed circuit 50) contains an inertial unit 54 with a 3-axis accelerometer and a 3-axis gyro-meter, in a manner known per se. The printed circuit 50 has signal processing circuits delivered by the inertial unit 54. Now, in the case of a non-deformable object, it is obvious that in the case of the function of estimating the flight time that is the subject of the present invention. , it is relatively easy to detect the start and end times of flight from the vertical acceleration data. Thus, when such an object is in flight, that is to say in free fall, it is not subjected to any mechanical force other than gravity (neglecting here the resistance of the air), and an accelerometer then delivers a null signal; in fact, with the known sensors, the static value of the gravity g is generally neutralized, so that the accelerometer on the vertical axis placed on a falling object measures Og (note here that, in the case where the 3-axis accelerometer placed in one of the housings 40 has - for example for reasons of integration in the reduced space of the housing - a reference system which does not directly deliver the vertical component in the terrestrial reference, the circuit of associated processing will be able to ensure the change of reference system allowing to obtain this vertical component).

In the case of a human body, which of course deviates significantly from the model of an indeformable solid, the vertical acceleration noted during the race depends largely on the location of the accelerometer on the body.

Thus Figure 2 gives an example of the evolution of the vertical acceleration as a function of time, measured at the level of the head of a runner, while Figure 3 gives a comparative illustration of the evolution curves of the runner. acceleration respectively measured with an accelerometer located at the level of the bust, therefore in the vicinity of the center of gravity of the runner (dashed curve), corresponding for example to the case of an instrumented abdominal belt, and with an accelerometer located at the level of the head (curve dashed lines), for example in one of the housings of the helmet of Figure 1.

In the first case, the approximation of indeformable solids, consisting in determining the duration of flight as being the period during which the vertical acceleration is close to gravity, remains viable: in the In this case, the instants at which the acceleration race crosses a horizontal line corresponding to the acceleration of gravity are detected.

However, it becomes impossible to implement in the case where the acceleration signal is established at the level of the head. Indeed, the elasticity of the human body during the race makes that the neck will stretch in flight and compress during the resumption of contact with the ground. It is mainly this elasticity which introduces into the acceleration curve significant deviations from a measurement made at the level of the trunk, and in particular oscillations and ruptures of slope as shown in Figures 2 and 3, preventing a good approximation of the moments at which the feet leave and find the ground.

Referring now to FIG. 4, the vertical acceleration CA vs. time curve at the runner's head is shown first.

A first approach to the determination of the flight time can consist in causing the acceleration signal processing circuit to determine lines approaching at best the slopes of the acceleration signal during the phases of decay and growth of the acceleration, corresponding to the resumption of support of the foot with the ground and the impulse of the foot. By extrapolating these lines, we can obtain an approximation of the moments at which the signal reaches a level corresponding to the acceleration of gravity. Thus, by determining the instants at which the corresponding lines, here D2 and D3 respectively, intersect the horizontal line H corresponding to the gravitational acceleration (or the zero acceleration in the case where the gravity correction is integrated), the Corresponding intersection points P2 and P3 make it possible to determine, by calculating the interval of time At which separates them, a first approximation of the flight time.

The calculation of the position and the slope of the straight lines D2 and D3 can be done based on the regions of the acceleration curve CA at which the evolution is the most regular. In a particular example, and as illustrated in FIG. 4, these zones are those included in a range of accelerations between -0.5g and +0.3g. The settings D2 and D3 lines can be determined by linear regression calculation in such a range.

To determine the validity of this approach, the flight time thus obtained can be compared with the flight time determined as explained above from an accelerometer placed at the level of the bust. This comparison is clearly visible in Figure 3, and highlights a certain bias on the point of intersection between the downward slope from the point P3, compared to the true moment (point P3 ') to which, according to the sensor bust, the foot resumes contact with the ground. It is observed that this bias can introduce a relatively large error in the determination of flight time.

More precisely, it is observed in FIG. 3 that there exists between the points P3 'and P3 an oscillation of the value of the acceleration which disturbs the accuracy of the calculation.

According to an improvement of the approach described above with reference to FIG. 4, the device is designed to be based not on acceleration alone, but on both the acceleration and on a kinematic variable derived from the acceleration.

More particularly and now with reference to FIG. 5, during the flight phase, the body subjected to gravity alone will adopt at its center of gravity, but also in a first approximation at its head, a parabolic trajectory, illustrated by the PV curve in Figure 5, whose maximum height will be reached in the middle of the flight phase (point P4). The device is then designed to derive from the vertical acceleration signal vertical position information which is known to have reached its value corresponding to a maximum altitude after substantially half the flight time.

Thus, the device can make a finer estimate of the flight duration by multiplying by two the time that elapses between the instant To start of the flight start (point P2 determined using the line D2 as described above). high) and the time Tp _0S vertMax which the vertical coordinate is maximum (point P4 determined as indicated above), namely:

DurationVol - 2 X (TposVertMax- ToehutVol) Comparative tests carried out with different runners equipped on the one hand with a device determining the duration of flight as explained above and with a system for capturing foot movements making it possible to precisely determine the moments at which the feet leave and find the ground showed that the above approach made it possible to obtain a completely satisfactory precision in order to allow a rider to realistically appreciate the qualities of his race in relation to the duration of flight.

FIG. 6 will now describe a method 100 for processing accelerometer signals making it possible to carry out a flight time determination as explained above, this method being implemented in a suitable computer receiving input. accelerometer signals.

In step 102, the raw signals of the 3D accelerometer are collected. Depending on the orientation of the accelerometer in the helmet worn by the runner, a repository change is made in step 104.

In step 106, the vertical component of the acceleration is isolated and recorded.

Step 108 consists in determining the straight lines approximating the slopes of the acceleration during the take-off and landing phases. In step 110, the intersection of the straight line D2 of increasing slope (flight phase) with the horizontal H representative of an acceleration equal to gravity is determined, to obtain and memorize the start time of the flight as explained with reference to Figure 4.

In parallel, the vertical acceleration information recorded in step 106 is subjected to a filtering step 112, typically high-pass filtering to eliminate the DC component, and dual integration to obtain the instantaneous vertical position from acceleration information, position value which is recorded in step 114. Step 116 is to determine the maximum value of the vertical position, to determine the mid-flight time, which is stored in step 118.

Furthermore, the vertical acceleration information isolated in step 106 is applied to a step 120 for determining the stride rate, implemented for example by low-pass filtering and determination of the period of the resulting cyclic signal. This period represents the duration of the stride recorded at step 122.

In step 130, the start time of flight time determined and recorded in step 1 10, the flight time mid-point determined and recorded in step 1 18 and the duration of the determined stride and recorded at step 122 are combined to determine flight duration and ground contact time.

More precisely, if T is the duration of the stride, t1 is the start time of the flight and t2 is the mid-flight moment, then the flight duration is equal to:

2 x (t2 - t1) and the ground contact time is: T - [2 x (t2 - t1)] This information is stored in step 132.

The above treatments are, for example, implemented in a general purpose microcontroller or dedicated to this function, provided in one of the helmet housings, the acceleration signals supplied by the 3D accelerometer being the object of a prior analog / digital conversion in a manner known to those skilled in the art.

The above calculations are carried out periodically, either at each stride, or all the N strides, depending on whether the information to be provided to the rider must be more or less detailed. Furthermore, the calculator device can perform any appropriate post-processing and integrate the calculated data to any file or stream of data related to the race (speed, GPS race track, heart rate, etc.).

The data can be made available in real time or near real-time on a connected device such as a watch or smartphone connected to the cable headset or wireless link such as Bluetooth, and / or stored in the headset memory circuits for to be loaded in deferred time in a device such as a computer, a tablet, a smartphone, etc. Moreover, the invention can be the subject of numerous variants, and in particular:

- rather than implementing a dual integration of the acceleration signal to deduce the vertical position, it is possible to perform a simple integration, which allows to obtain the speed, and detect a change of sign of the information velocity, the instant of this change of sign being identical to the moment at which the vertical position of greater altitude has been reached;

by comparing the data obtained with the present invention with actual data obtained with appropriate sensors, it is possible, in order to improve the accuracy of the calculation of the flight time, to cause the calculation circuit to provide corrections to the processes, for example by providing a correction fixed or proportional to the slope of the acceleration during the flight phase, a correction at the acceleration threshold (strictly equal to g in the preceding example, but which may to some extent), the determination of the top of the parable, the multiplier (which may not be exactly equal to 2) of the estimated half-flight duration, and so on.

the treatment device and the inertial unit (or only an accelerometer, or only an accelerometer working on a vertical axis) can be received on or in any other equipment, for example a headband, a non-audio headset, a pair glasses, etc.) intended to be placed in the vicinity of the subject's head.

Claims

1. Device for determining stride parameters of a run comprising:

an accelerometer (54) able to provide a vertical acceleration signal of an upper anatomical region of a runner; and

a flight time calculation circuit starting from the vertical acceleration signal (50),

characterized in that the flight time calculating circuit is configured to:

i) determining a start time of flight (P2, start-up) from a slope (D2) of evolution of the vertical acceleration signal and a predetermined acceleration value (g), and

ii) determining a flight duration (DurationVof) from information (PV, P4) obtained by integrating the vertical acceleration, and the start time of flight (P2, Toébutvo!.

2. Device according to claim 1, characterized in that the flight time calculation circuit (50) is able to determine the flight time from a vertical position information (PV) obtained by double integration of the signal d vertical acceleration.

3. Device according to claim 2, characterized in that the flight time calculation circuit (50) is able to determine the flight time from the moment of the beginning of flight (P2, T'butvoi) and d a moment of vertical position of greater altitude (P4).

4. Device according to claim 3, characterized in that the flight time is determined to be equal to twice the difference between the start of flight times (P2, Toboutvoi) and vertical position of greater altitude (P4).

5. Device according to claim 1, characterized in that the start of flight time (P2, Toebu i) is determined as an intersection between a straight line having said slope (D2) of evolution of the vertical acceleration signal. with a line (H) representative of said predetermined acceleration value (g).

6. Device according to claim 1, characterized in that said predetermined acceleration value is the acceleration of gravity (g).

7. Device according to claim 1, characterized in that it is subject to the movements of the head of the runner.

8. Headphone (10), characterized in that it comprises a device (50, 52, 54) according to claim 7.

9. Method (100) implemented by a flight time calculating circuit for determining stride parameters of a run from a vertical acceleration signal of an anatomical region superior of a runner provided by an accelerometer,

characterized in that it comprises the following steps:

i) determining (108, 1 10) a start time of flight (P2, Toetu i) from a slope (D2) of evolution of the vertical acceleration signal and a predetermined acceleration value (g ), and

ii) determining (130) a flight duration (FlightTime) from an information item (PV, P4) obtained by integration (1 12) of the vertical acceleration, and the start of flight time (P2, Tohutvoi ).

10. Method according to claim 9, characterized in that the step of determining (130) the flight duration is implemented from a vertical position information (PV) obtained by double integration of the vertical acceleration signal. (IT).

1 1. A method according to claim 10, characterized in that the step of determining the flight time is implemented from the moment of start of flight (P2, To start) and a moment (P4) of vertical position higher altitude.

12. The method of claim 11, characterized in that the flight duration is determined to be equal to twice the difference between the start of flight instants (P2, Toeto) and the vertical position of greater altitude (P4).

13. The method as claimed in claim 9, characterized in that the flight start instant (P2, T∞butter) is determined as an intersection between a line having said slope of evolution (D2) of the acceleration signal. vertical with a line (H) representative of said predetermined acceleration value.

14. The method of claim 9, characterized in that said predetermined acceleration value is the acceleration of gravity (g).