US20160001163A1

US20160001163A1 - Secure attachment of a shoe on a ski

Info

Publication number: US20160001163A1
Application number: US14/767,142
Authority: US
Inventors: Fabrice Devaux
Original assignee: BRISON SA
Current assignee: BRISON SA
Priority date: 2013-02-11
Filing date: 2013-12-10
Publication date: 2016-01-07
Also published as: FR3001898A1; EP2953694A1; WO2014122366A1; EP2953694B1; FR3001898B1; JP2016506808A

Abstract

The device for performing secured binding of a boot on a first ski includes a binding of the boot on the first ski and a control circuit. The binding is configured to facilitate disengagement between the boot and the first ski on receipt of a disengagement signal. A control circuit is configured to:

- determine an angular deviation between a first direction of the first ski and a second direction of a second ski,
- determine the forward progression of the first and second skis along the longitudinal axis of each of the skis,
- calculate at least one parameter from the angular deviation and from the forward progressions of the first and second skis, compare the parameter with a threshold parameter, and transmit the disengagement signal according to the comparison.

Description

BACKGROUND OF THE INVENTION

The invention relates to a device for secured binding of a boot on a ski.

State of the Art

Boot bindings, in particular for ski boots, enable a boot to be secured in reliable and removable manner on a ski. Releasing between the boot and the ski is either performed deliberately by the user by means of mechanical means or happens involuntarily when certain forces higher than a predefined threshold are applied on at least one of the parts of the binding, for example in the event of the skier falling.
The predefined threshold of the forces above which the boot disengages from the ski (or is released from its binding) is generally adjustable according to the user's weight, level of ability, physical fitness, etc.
Incorrect adjustment of the bindings results in:

- an increased risk of accident by untimely disengagement (or releasing) if the adjustment is too slack,
- an increased risk of knee injury in case of falling by failure to disengage (non-release) if the adjustment is too tight. In particular, failure to release is the principal cause of sprained knees.

The most commonplace convention bindings comprise a heel piece and a front stop, the heel piece exerting a pressure on the heel of the boot, thus pressing the boot against the front stop. In the event of the skier falling, the jaws of the heel piece and/or of the front stop open or swivel automatically due to the effect of forces higher than a predefined threshold in order to release the boot from the binding. This therefore involves purely mechanical means implemented for example by means of simple springs.
Bindings are undergoing continuous improvements. Patent application FR 2,874,833 describes in particular a ski boot binding which improves the safety of the bindings by proposing a heel piece comprising means for facilitating rotation of the heel of the boot around a vertical axis while limiting the friction resistances of the sole of the boot on the binding.
However, such a device does not make the ski boot disengage from the ski in potentially dangerous situations. In particular, this type of device does not protect the knee in all risk situations as it does not present any possibility of disengagement between the boot and the ski whatever the torques applied on the binding and in particular whatever the axes of these torques.
Furthermore, as explained above, for a good efficiency, the binding has to be properly adjusted according to parameters particular to the individual skier and which are liable to change with time (skier's weight, level of ability, fitness, etc).
U.S. Pat. No. 6,007,086 proposes a ski boot binding device having the objective of remedying these shortcomings. Said device comprises in particular a binding system of a ski boot on a ski by means of electromagnets and a processor configured to communicate with said binding system. This device enables the boot to be released from the ski when forces in excess of a predefined threshold are identified by the processor. Furthermore, this device can be completed by a transmitter located at the front of a first ski and a receiver placed in the same manner on a second ski, both of the skis comprising a transceiver set in communication with the processor. In such a system, the transmitter of a first ski sends a signal to the receiver of the second ski, the signal being in the form of a unidirectional arc. When communication is interrupted between a transmitter of one ski and the receiver of the other ski, the processor sends a release signal to the binding system.
Such a device therefore enables releasing to be performed in situations that are hazardous for the skier, in particular when the skis have an abnormal angular deviation (U.S. Pat. No. 6,007,086, FIG. 5b and 5c).
However, this device presents the major drawback of causing releasing in non-hazardous situations or when a pile of snow between the skis momentarily interrupts the signal. Inversely, this system makes the binding release too late in hazardous situations.

OBJECT OF THE INVENTION

It is observed that a requirement exists to provide a device for secured binding of a boot on a ski which presents improved risk situation detection.
This requirement tends to be met by means of a device for secured binding of a boot on a first ski comprising:

- binding means of the boot on the first ski configured to facilitate disengagement between the boot and the first ski on receipt of a disengagement signal,
- a control circuit configured to:
- determine an angular deviation between a first direction of the first ski and a second direction of a second ski,
- determine the forward progression of the first and second skis along the longitudinal axis of each of said skis,
- calculate at least one parameter from the angular deviation and from the forward progressions of the first and second skis, compare the parameter with a threshold parameter, and transmit the disengagement signal according to the comparison.

According to a preferred embodiment, the control circuit is configured to:

- determine an angular deviation between a first direction of the first ski and a second direction of a second ski,
- determine the first direction of progression of the first ski and the second direction of progression of the second ski,
- calculate at least one parameter from the angular deviation, the first direction of progression and the second direction of progression, compare the parameter with a threshold parameter, and transmit the disengagement signal according to the comparison.

According to an even more preferred embodiment, the control circuit is configured to:

- determine a first angle between first direction of the first ski and a first fixed reference direction,
- determine a second angle between the second direction of the second ski and a second fixed reference direction,
- calculate at least one parameter from the first angle, the second angle, the first direction of progression and the second direction of progression.

Advantageously, the first and second reference directions correspond to magnetic north.
According to a particularly advantageous embodiment, the control circuit is configured to evaluate the speed of movement of the first ski.
Preferentially, the control circuit further comprises at least one gyroscope and/or at least one accelerometer. The gyroscope can be achieved by any suitable means. In a particular embodiment, the gyroscope is formed by a set of accelerometers connected to a microprocessor continuously integrating the accelerations. Even more preferentially, the control circuit comprises at least one inertial unit and possibly a compass. The compass can be two-dimensional or three-dimensional. In the case of a three-dimensional compass, the compass indicates the three-dimensional vector formed by the terrestrial magnetic field with respect to the control circuit.
According to an advantageous embodiment, the control circuit of each ski comprises a sensor and a computing circuit configured to compute the parameter or parameters.
According to another embodiment, the device comprises a piezoelectric blade configured to be integrated in the ski and the control circuit is configured to discriminate between sliding of the ski and another movement of the ski by monitoring the electric power generated by the piezoelectric blade. Preferentially, the piezoelectric blade is configured to supply the whole of the secured binding device.
Advantageously, the binding system comprises a front stop, a heel piece and at least one swivelling plate placed between the front stop and the ski and/or between the heel piece and the ski. Preferentially, the swivelling plate is configured to be blocked in case of absence of a disengagement signal.
According to an advantageous embodiment, the device comprises a first control circuit configured to be associated with a right ski and a second control circuit configured to be associated with a left ski.
According to another embodiment, the control circuit is configured to determine which ski is the right ski and which ski is the left ski with respect to the boot with which each ski is associated.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and features will become more clearly apparent from the following description of particular embodiments of the invention given for non-restrictive example purposes only and represented in FIG. 1 which illustrates an embodiment of a secured binding device, in schematic manner in top view.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The device for secured binding of a boot on a ski comprises binding means 1 of the boot on a first ski configured to facilitate disengagement between the boot and the first ski on receipt of a disengagement signal.
Binding means 1 can be any means for binding a boot on a ski well known to the person skilled in the art.
According to a particular embodiment, the binding device comprises a swivelling plate 3 placed between the front stop and the ski and/or between the heel piece and the ski in order to enable the boot to disengage more easily and to reduce the risk of injury for the skier. In this manner, binding means 1 present two different behaviours.
The bindings are preferentially conventional bindings comprising a front stop and a heel piece with which at least one swivelling plate placed between the ski and the front stop and/or between the ski and the heel piece is associated.
What is meant by “conventional bindings” is any binding as described in the foregoing designed to mechanically fix the boots to the ski and to release them, in particular when forces greater than a predefined threshold are applied on at least one of the components of the binding.
Swivelling plate 3 is configured to rotate, for example through more or less 60°, around an axis which is vertical with respect to the main plane of the ski parallel to the sliding surface of said ski.
In a particular embodiment, swivelling plate 3 comprises an electromechanical mechanism whereby

- either plate 3 can be immobilized,
- or, on receipt of a disengagement signal, plate 3 is allowed to swivel freely with a certain amplitude, for example oil more or less 60° with respect to the previous position.

When plate 3 is immobilized, the same is the case for the binding which is fitted on plate 3. In this position, the user can ski and binding means 1 advantageously operate as in the prior art.
When plate 3 is released, it can swivel in the same way as the binding. This freedom of rotation enables the boot to disengage more easily being released laterally with respect to the ski to reduce the risks of injury for the skier, in particular knee injuries.
The binding device also comprises a control circuit 2 configured to:

- determine an angular deviation between a first direction of the first ski and a second direction of a second ski,
- determine the forward progression of the first and second skis along the longitudinal axis of each of said skis,
- calculate at least one parameter from the angular deviation and the forward progressions of the first and second skis, compare the parameter with a threshold parameter, and transmit the disengagement signal according to the comparison.

Control circuit 2 is configured to block binding means 1 in a functional position enabling skiing, for example to block swivelling plate 3 in its non-swivelling configuration, in the case of absence of a disengagement signal.
In this way, by default, plate 3 is in the blocked position so that, in case of failure of control circuit 2 or if the signal is absent, the binding device operates as in the prior art. The user is still protected but in less efficient manner, for example as in the prior art.
Knowing the angular deviation between the two skis and their forward progression makes it possible to quickly differentiate between a risk situation and a normal situation.
Preferentially, each ski comprises a binding device comprising at least one binding means 1 and a control circuit 2.
Advantageously, control circuit 2 of each ski comprises one or more sensors and a computing circuit to compute the parameter or parameters.
Control circuit 2 of the first ski can be connected to binding means 1 by a hard-wired connection. This in particular enables the electric consumption of the binding device to be reduced.
Control circuit 2 is designed to be able to know the spatial configuration of the two skis and to determine whether the situation is a risk situation or a non-hazardous situation. In this manner, compared with devices of the prior art, disengagement in non-hazardous situations is reduced.
According to a preferred embodiment, a first control circuit 2 is fixed onto the first ski so as to determine one or more parameters specific to the first ski. A second control circuit 2 is fixed onto the second ski so as to determine one or more parameters specific to the second ski. The use of a control circuit 2 dedicated to each ski facilitates computation of the different required parameters. This does however generally mean that it is necessary to know which ski is the right ski and which other ski is the left ski. This determination can be made either by an initial predetermination of a right ski and a left ski in the design stage of the skis, or by parameter setting of the skis depending on whether they are associated with a right boot or with a left boot. In this way, according to a first embodiment, the secured binding device comprises a first computing circuit configured to be associated with a right ski and a second computing circuit configured to be associated with a left ski and, according to a second embodiment, control circuit 2 is configured to determine which ski is the right ski and which ski is the left ski with respect to the boot with which each ski is associated. The second embodiment presents the advantage of being able to use two identical skis.
In advantageous manner, control circuit 2 of each ski sends the information relative to its ski to a computing circuit. The computing circuit is then able to compute the parameter. In advantageous manner, the information is transmitted in permanent or in periodic manner. In an advantageous embodiment, the computing circuit is fixed onto one of the skis. In even more advantageous manner, each ski comprises a computing circuit which receives information from the different sensors. Preferentially, the computing circuit is connected by a hard-wired connection to control circuit 2 of its ski, to any other sensors that may be fitted and to binding means 1 of its ski.
Advantageously, control circuit 2 of the first ski communicates in periodic manner or in continuous manner with control circuit 2 of the second ski.
Communication between the two skis is preferentially a wireless communication, for example with a radio-frequency link. However, it is also conceivable to use a hard-wired connection by means of a conducting wire integrated in the ski boots and in the skier's ski pants. The communication between the two control circuits 2 can for example be digitally encoded. It can more preferentially be performed by means of an encrypted radio wave.
In another embodiment that is able to be combined with the previous embodiments, the secured binding device further comprises a sensor configured to determine whether the boot of one of the two skis has disengaged. The sensor is configured to determine whether the boot is fixed or not. In the case where the sensor detects that a first boot has disengaged, said sensor communicates the disengagement to the sensor or to control circuit 2 of the other ski and control circuit 2 of this other ski facilitates disengagement of the second boot. A disengagement signal is then sent to binding means 1 of the other ski. In this way, as soon as a boot has disengaged, the other boot also disengages. This configuration enables the risks of injuries to be reduced. The sensor can be achieved by any means known to the person skilled in the art, for example by a magnetized system or any other passive system able to detect two different signals indicating for example “absence of boot”, “right boot” or “left boot”.
In an advantageous embodiment, the binding device also comprises a control circuit 2 configured to:

- determine the angular deviation between the first direction of the first ski and the second direction of the second ski, and
- determine a first direction of progression of the first ski and a second direction of progression of the second ski,
- calculate at least one parameter from the angular deviation, the first direction of progression and the second direction of progression, compare the parameter with a threshold parameter, and transmit the disengagement signal according to the comparison.

According to this embodiment, control circuit 2 is therefore configured to further determine the direction of progression of the first and second skis whatever the direction of progression of the skis with respect to their longitudinal axis and/or whatever their direction of progression (forward, backward, left, right, etc). This can be achieved by any means known to the person skilled in the trade, for example by integrating a geolocation device, at least one accelerometer and/or at least one gyroscope in each ski. Thus, by means of such a control system, the secured binding device enables a better evaluation of risk situations. In advantageous manner, the gyroscope can be formed by means of a set of accelerometers connected to a microprocessor which integrates the accelerations in continuous manner. This functionality can be obtained for example by means of a 9-axis sensor.
In this way, control circuit 2 is able to know the spatial configuration of the two skis and to determine whether the situation is a risk situation or a non-hazardous situation. For example purposes, in certain configurations, the skier performs a backward movement at low speed and stops in a configuration which is considered as being a risk configuration if the skier advances in the normal direction of progression. In this way, in comparison with devices of the prior art, disengagement in non-hazardous situations is reduced.
In a particularly advantageous embodiment, control circuit 2 is configured to:

- determine a first angle between a first direction of the first ski and a first fixed reference direction,
- determine a second angle between a second direction of the second ski and a second fixed reference direction.

The first angle and the second angle serve the purpose of determining the angular deviation which exists between the two skis. This embodiment is simpler to set up and it is also more rugged.
Control circuit 2 is configured to calculate at least one parameter from the first angle, the second angle, the first direction of progression and the second direction of progression, to compare the parameter with a threshold parameter, and to transmit the disengagement signal according to the comparison.
The threshold parameter is integrated in control circuit 2, and can be evaluated by modelling of risk situations taking a part or of all of the parameters measured by the binding device into account.
Preferentially, the first reference direction is identical to the second reference direction. For example purposes, one of the reference directions is determined with respect to a marker or with respect to magnetic north.
Even more preferentially, the first and second reference directions correspond to magnetic north. This enables easy measurement by means of an independent quantity that is easily detectable by means for example of a simple compass, or preferentially a three-dimensional compass. In the case of a three-dimensional compass, information on the direction of the north is provided. In the case of a three-dimensional compass, the compass also indicates the three-dimensional vector which the terrestrial magnetic field makes with the control circuit.
Determination of the directions of orientation of the skis and determination of the directions of progression of the skis can be performed by any suitable means, for example by means of a geolocation device such as a GPS. It is however necessary to ensure that the capacities of the GPS are able to distinguish between the positions of the two skis.
In a preferred embodiment, the secured binding device is configured to be disengaged manually, for example by means of a remote control. Thus, in all the situations where the skier does not wish to take advantage of the device, for example when the skier is taking a chairlift or practicing extreme skiing, the device can be completely shut down.
In another embodiment able to be combined with the previous embodiments, control circuit 2 is configured to bring about disengagement of both boots.
According to one embodiment, control circuit 2 comprises an inertial unit and the compass of control circuit 2 enables recalibration of the inertial unit. Recalibration is preferably performed when the compass is in a normal or substantially normal plane to the Earth's radius. This recalibration is particularly advantageous for a three-dimensional compass. Recalibration can also be performed taking account of gravity in order to determine the position of the skis in a plane normal to the Earth's radius. When the compass is three-dimensional, recalibration can be performed whatever the position of said compass with respect to the Earth's radius. According to a particularly preferred embodiment, control circuit 2 is configured to be recalibrated periodically. The inertial unit enables the orientation of the ski to be determined in particular when the compass measurement is very noisy or disturbed by metallic elements. This configuration enables a reliable measurement to be had in a very large variety of configurations.
According to a particular embodiment, control circuit 2 can also be configured to evaluate the speed of movement of one of the skis such as the first ski or both of the skis. For this purpose, control circuit 2 can also comprise at least one accelerometer. Evaluation of the speed enables risk situations to be better determined. For example, a snowplough position where the skis are particularly far apart from one another at the back result in a boot/ski disengagement if the skier is at high speed whereas disengagement will not take piece at a standstill or at very low speed.
According to a particular embodiment compatible with the previous embodiments, control circuit 2 is configured to discriminate between sliding of the ski on the ski slope and another movement of the ski, for example a movement on a chairlift. The skis can in fact be immobile on the chairlift but present is speed of movement which may be high. In advantageous manner, the ski comprises a piezoelectric material film or piezoelectric blade 4 preferably integrated in the ski. In this way, when the ski slides on the snow with the skier, the ski deforms and vibrates thereby enabling piezoelectric blade 4 to generate electricity. When the ski is in motion on a chairlift on the other hand, the deformations of the ski are small, there is little or no torsion or deformation of piezoelectric blade 4 and the electricity generated by piezoelectric blade 4 is then extremely low. It is thus possible to distinguish between these two scenarios by monitoring the electric power generated by piezoelectric blade 4. Control circuit 2 is advantageously configured to monitor the electric power supplied by piezoelectric blade 4 in order to determine whether the ski is sliding on the snow or not. In this way, control circuit 2 is configured to distinguish between sliding of the first ski and another action by monitoring the electric power produced by piezoelectric blade 4 in the first ski. When the electric power produced is lower than a given threshold, control circuit 2 blocks binding means 1 so that the binding device operates as in the prior art
In a preferential embodiment, piezoelectric blade 4 is also configured to at least partially supply the secured binding device. Advantageously, piezoelectric blade 4 supplies the whole of the secured binding device.
In a particular embodiment, piezoelectric blade 4 is coupled with super-capacitors or with miniature batteries. When it is in use, piezoelectric blade 4 deforms and generates an electric current which supplies the electronic devices of the binding device.
According to an advantageous embodiment, the binding device operates in an energy saving mode in particular in case of disengagement between the boots and binding means 1 or if there is no or very little power produced by piezoelectric blades 4. In this case, there is no communication between the skis.
According to a preferred embodiment, control circuit 2 comprises an inertial unit which may be recalibrated periodically by means of a two-dimensional compass, or preferably a three-dimensional compass. Advantageously, each ski is monitored continually by its control circuit 2 which detects a sudden change of direction or a sharp deceleration. Thus, when control circuit 2 detects an angular acceleration and/or a linear acceleration or deceleration of the ski in excess of a predefined threshold, it transmits a disengagement signal to binding means 1 of said ski. The angular acceleration and/or linear acceleration or deceleration threshold of the ski can be set manually or established during a learning mode of the binding device. Such an embodiment enables the skier to disengage immediately as soon as a ski is stopped or diverted by an obstacle, whatever the forces applied on binding means 1.
According to a preferred embodiment, in case of absence of communication between the two skis, control circuit 2 blocks binding means 1 so that the binding device operates as in the prior art. Thus, when the binding device comprises a swivelling plate 3, the latter is located in the immobilized position, enabling the user to ski, in case of absence of communication between the two skis. The user is therefore still protected but in less efficient manner, as for example in the prior art. Preferentially, in case of absence of communication between the two skis, control circuit 2 does not transmit any disengagement signal except in the case of an angular acceleration and/or of a linear acceleration or deceleration of the ski exceeding a predefined threshold, as has been described in the foregoing.
In a particularly advantageous embodiment, control circuit 2 comprises at least one inertial unit. An inertial unit is fitted on each ski and control circuits 2 are configured to perform calibration of the two inertial units. In this way, when the calibration step is performed, the placement of the two skis is determined. When the skier moves on his skis, the two inertial units calculate the movement and speed components step by step which enables control circuit 2 to determine the angular deviation and the direction of orientation of the two skis. The use of an inertial unit is particularly advantageous as it enables the angle each ski makes with its reference direction to be calculated in greatly disturbed locations. For example, if the reference direction is magnetic north, it is difficult to determine the first and second angles in an area presenting for example underground electric cables.
In advantageous manner, the inertial unit is associated with a two-dimensional compass, or preferentially with a three-dimensional compass. This association enables an inertial unit with lesser performances to be used. This inertial unit is initially calibrated and periodically recalibrated by means of the compass. In this way, the skier does not have to perform any initial calibration procedure of the inertial unit and calculation of the angular deviation between the skis is reliable over a large time period.
Advantageously, control circuit 2 is configured to recalibrate the inertial units periodically and to avoid use of the compass when the ski is greatly displaced which distorts measurement or, in the case where a two-dimensional compass is used, when the position of the ski is not sufficiently parallel to the normal plane of the Earth.
According to a preferred embodiment, control circuit 2 is formed by a set of micro electromechanical systems (MEMs) thereby enabling the electric consumption of the device to be reduced.
According to a particularly advantageous embodiment, control circuit 2 is configured to comprise a “learning mode”. Such a mode enables calibration of control circuit 2 on the first run or runs performed by the skier. Thus, on the first run or runs, the secured binding device is partially activated in the sense that control device 2 is only configured to determine the threshold parameters (for example angular acceleration and/or linear acceleration or deceleration threshold of the ski above which control circuit 2 has to transmit a disengagement signal) linked to the individual characteristics of the skier, in particular his technical ability, but does not transmit any disengagement signal. During such a learning mode, the user is still protected but in less efficient manner, for example as in the prior art. Advantageously, the binding device can be pre-calibrated before the first run in learning mode. In this case, the user will indicate his own characteristics, for example his/her weight and/or level of ability on a reduced scale of levels (for example, “beginner”/“intermediate”/“experienced”) which will be integrated by control circuit 2. The binding device will then operate, on the first run, according to the parameters initially indicated by the user while determining, still during this first run, the real threshold parameters (for example angular acceleration and/or linear acceleration or deceleration threshold of the ski above which control circuit 2 has to transmit a disengagement signal) linked to the level of ability of the user. Preferably, learning mode can be reiterated as many times as necessary in particular if the skier has fallen during the first run. Learning mode can also be progressive, the skier first of all performing a first descent on a blue run, and then a second descent on a red run, etc. Such an embodiment is particularly advantageous in particular because an over-estimation by the user of his actual level of ability is regularly observed.
The secured binding device enables risks of injury for the skier to be prevented while at the same time enabling him/her to ski without his/her skis releasing in untimely manner. For example, a position of the skis of rear snowplough type (back ends of the skis towards one another and separation of the front tips of the two skis) will not result in disengagement between the boot and the ski if the skier is moving in a backwards direction. The binding device therefore enables skiing to be performed without any risk of injury and without the boots disengaging from their bindings when the situation is not a risk situation.
The design of the device further enables the latter to be associated with a conventional binding comprising a purely mechanical secured system. The device therefore takes a large number of parameters into account such as the relative position of the skis with respect to one another, the direction of movement, speed, skier's weight, level of ability, etc. in order to evaluate risk situations.

Claims

1-14. (canceled)

15. A device for secured binding of a boot on a first ski comprising:

a binding of the boot on the first ski configured to facilitate disengagement between the boot and the first ski on receipt of a disengagement signal,

a control circuit configured to:

determine an angular deviation between a first direction of the first ski and a second direction of a second ski,

determine a forward progression of the first and second skis along a longitudinal axis of each of said skis,

calculate at least one parameter from the angular deviation and from the forward progressions of the first and second skis, compare said at least one parameter with a threshold parameter, and transmit the disengagement signal according to said comparison.

16. The device according to claim 15, wherein the control circuit is further configured to:

determine a first direction of progression of the first ski and a second direction of progression of the second ski,

calculate at least one additional parameter from the angular deviation, the first direction of progression and the second direction of progression, compare the at least one additional parameter with an additional threshold parameter, and transmit the disengagement signal according to said comparison between the at least one additional parameter with the additional threshold parameter.

17. The device according to claims 15, wherein the control circuit is further configured to:

determine a first angle between the first direction of the first ski and a first fixed reference direction,

determine a second angle between the second direction of the second ski and a second fixed reference direction,

calculate the at least one parameter from the first angle, the second angle, the first direction of progression and the second direction of progression.

18. The device according to claim 17, wherein the first and second fixed reference directions correspond to magnetic north.

19. The device according to claim 15, wherein the control circuit is configured to evaluate a speed of movement of the first ski and to further calculate at least one parameter from said speed of movement.

20. The device according to claim 15, wherein the control circuit further comprises at least one gyroscope and/or at least one accelerometer configured for determining the first direction of the first ski and or the forward progression of the first ski.

21. The device according to claim 20, wherein the control circuit comprises at least one inertial unit.

22. The device according to claim 21, wherein the control circuit comprises a compass configured for recalibrate the at least one inertial unit.

23. The device according to claim 15, wherein a second control circuit is associated to the second ski, each control circuit comprises a sensor and a computing circuit configured to compute the at least one parameter.

24. The device according to claim 15, further comprising a piezoelectric blade configured to be integrated in the first ski and wherein the control circuit is configured to discriminate between a sliding movement of the first ski and another movement of the first ski by monitoring an electric power generated by the piezoelectric blade.

25. The device according to claim 24, wherein the piezoelectric blade is configured to supply the whole of the secured binding device.

26. The device according to claim 15, wherein the binding comprises a front stop, a heel piece and at least one swivelling plate placed:

between the front stop and the first ski and/or

between the heel piece and the first ski.

27. The device according to claim 26, wherein the swivelling plate is configured to be blocked in case of absence of a disengagement signal.

28. The device according to claim 15, comprising a first control circuit configured to be associated with a right ski and a second control circuit configured to be associated with a left ski.

29. The device according to claim 15, wherein the first and second control circuits are configured to determine which ski is the right ski and which ski is the left ski with respect to the boot with which each ski is associated.