FR2690613A1 - Four point posture monitoring system - uses detectors under heel and toe of each foot to give pressure signals that are processed to give measure of posture - Google Patents

Abstract

The posture monitoring has an acquisition phase gathering signals (S1-S4) from four detectors (C1-C4) in the top surface (P) of a plate on which the subject stands. The signals are processed to deliver data representative of the posture of the subject. The four signals represent the pressure exercised by the heel and toe of each foot of the subject on the detectors. The relative strengths of these signals can be used to deduce measures of the posture of the subject. The subject receives visual information on their posture from a screen (3), and resulting changes of posture are monitored and displayed. ADVANTAGE - Portable posture measurement equipment that can be brought to subjects home environment

Description

 The present invention relates to a tetra-ataxiametric posturography method.

 It also relates to a system implementing this method as well as the associated multisensor device.

Techniques for measuring human posture, or posturography, are already known using measurement platforms. These techniques are based on a scientific theory and methodology now established and widely described, especially in the publications of the Society's international congresses.
Internationale de Posturographie or in the journal "Agressologie" published by Editions MASSON in Paris, as well as in the notebooks of the Société Française de posturographie.

 Current posturography techniques, which have benefited from the considerable progress made in the field of pressure sensors, in particular piezoelectric sensors, and in that of computer processing means, are based on the processing of signals from a single platform. which essentially measures a) the oscillations of a subject's body in anteroposterior and lateral direction and b) the length of the trace produced by the vertical projections of the displacements of the subject's center of gravity on the surface of the platform. Posturography devices of this type, equipped with a single platform or plate, are said to be mono-ataxiametric.

 In addition, these mono-ataxiametric devices are generally heavy, non-transportable and often fixed to the ground. This has the consequence of forcing patients to go to a clinic or an equipped research laboratory, which generally contributes to modifying the behavior of the patient for whom the atmosphere of these places is very often intimidating. In addition, it is difficult to acquire posturographic data from normal subjects, especially children, since parental permission and cooperation are required beforehand. Finally the cost of acquisition of these devices is very high and generally beyond the possibilities of most public institutions.

 The object of the invention is to remedy these drawbacks by proposing a tetra-ataxiametric posturography method, comprising a step of acquiring signals from pressure sensor means included in a sensor device on the upper face of which a subject is standing. standing substantially in equilibrium, and a first step of processing said signals to deliver information representative of the posture of said subject and of the temporal evolution of said posture.

 According to the invention, this method is characterized in that at least four measurement signals representative respectively of the pressures exerted by each toe and each heel of the subject are generated by at least four independent pressure sensors representing said pressure sensor means and associated with at least four plates respectively receiving the two toes and the two heels of said subject, and in that the processing step comprises a step of analysis and interpretation of the interactions existing between these at least four measurement signals .

 Thus, with the method according to the invention, posturographic information is effectively tetra-ataxiametric while implementing a multisensor device which is much less bulky and expensive than the devices of the prior art, thus contributing to a development of this technique. diagnostic.

In addition, the independence of the four sensors allows a richer analysis of the interaction between the signals which result therefrom and a finer interpretation of the posturographic results thus obtained.

 Currently, the device of four independent sensors is capable of analyzing the dynamic coordination between toes and heels as it is put into action during walking. Consequently, it is possible to measure the non-linear (chaotic) dynamics of walking in a stationary position.

 According to another aspect of the invention, the posturography system implementing the method according to the invention, comprising a sensor device on the upper face of which a subject is standing substantially in equilibrium, is characterized in that this sensor device comprises at least four independent pressure sensors placed under at least four independent plates on which the toes and heels of said subject respectively rest, and in that said system comprises first control and processing means connected to the sensor device, for receiving and processing at least four measurement signals generated by said at least four independent sensors in order to provide information representative of the posture of said subject.

 According to yet another aspect of the invention, the multisensor device used in the posturography system according to the invention, is characterized in that it comprises on its upper face at least four independent plates of predetermined dimensions and arrangements under each of which is placed at least one independent pressure sensor, and in that it further comprises means for supplying electrical energy, means for collecting the measurement signals generated by said sensors, and means for processing these signals with a view to transmitting them to the first means of control and processing.

Other features and advantages of the invention will become apparent in the description below. In the accompanying drawings given by way of nonlimiting examples
- Figure 1 is an overview of an embodiment of the system according to the invention
- Figure 2 shows a multi-sensor device according to the invention;
- Figure 3 shows specific arrangements of platforms
- Figure 4 shows a particular embodiment of the internal circuit of a multi-sensor device according to the invention;
- Figure 5 illustrates different forms of display in response to combinations of signals from the sensors
- Figure 6 is a diagram illustrating the main steps of input, processing and output of the posturography method according to the invention; and
- Figure 7 is a diagram illustrating the essential steps for managing a posturography session with the method according to the invention.

 We will now describe a preferred embodiment of the posturography system according to the invention and of the associated device at the same time as the method implemented in this device, with reference to FIGS. 1 to 7.

 The tetraataxiametric posturography system 1 illustrated in FIG. 1 comprises a multisensor device 14 on which a subject stands upright, the tips and heels of his feet resting respectively on four plates P1, P2, P3, P4 placed on the upper face P of the multisensor device 14, as shown in FIG. 2.

 The multisensor device 14 is connected to a first microcomputer 2 via a first connector 8 by a first cable 5 for the purposes of data acquisition and of control and processing of the posturography system 1.

The device 14 can also be connected to a second microcomputer or computer 9 associated with a display device, for example a screen 3.

 The multisensor device 14 is supplied with electrical energy from the network or sector by a standard cord 4, via a power connector 15.

 The four plates, which each constitute a separate sensor, include two rectangular plates PI, P3, for example 18 cm by 10 cm, receiving the two toes of the subject, and two square plates P2, P4, of equal side for example at 10 cm, receiving the two heels of the subject.

 It is possible to adapt the multisensor device according to the invention to the dimension of the feet of the subject by screwing on a plate of origin P1 a plate P1 'of smaller dimension (FIG. 3 (a)) or else a plate Psi' 'of larger dimension (figure 3 (b)).

 Each plate P1-P4 is associated with a pressure sensor C1-C4 which has the function of generating a signal representative of the pressure and therefore of the resulting force F1-F4 exerted on the plate which is associated with it.

 The multisensor device 14 comprises a transformation module 10 ensuring the supply of the four sensors C1-C4 and receiving the signals S1-S4 which result therefrom, converting them and transmitting them to the main computer 2. This transformation module 10 comprises a unit of conversion II connected as an input to the AC network S via a connector 15 and generating on the one hand a DC voltage Vc, for example equal to 15 volts, and on the other hand a pulsed supply voltage of constant level Vp, for example 12 volts with 40 pulses per second, supplying each C1-C4 sensor.

 A conventional resistive sensor can be provided as a sensor, the resistance of which decreases when the pressure exerted increases, thereby contributing to generating an output signal sensitive to this pressure.

Each generated signal S1-s4 is applied to the input of a separate amplifier A1-A4 supplied by the DC voltage Vc. The output of each amplifier A1-
A4 is applied at the input of an analog-digital conversion module (ADC) 12 which generates image coded digital information of the different acquired analog signals. The arrangement of this digital information can be carried out according to usual techniques in the field of data acquisition and transmission and therefore will not be described here. The data is transmitted via the connector 8 by the cable 5 to a digital processing card 20 inserted in the microcomputer
The transformation module 10 further comprises a control circuit 13 receiving the output signals from the amplifiers A1-A4 and generating coded digital information representative of a combination of signals associated with the four plates P1-P4, with reference to FIG. 5 .

 Thus, when a sensor measures a pressure below a predetermined threshold, logic information 0 is associated with the plate concerned. The table shown in Figure 5 shows four combinations in which one plate is lightly or not pressed while the body weight is mainly supported by the other three plates (A pressure greater than the predetermined threshold is represented by a + sign). The circuit 13 transmits information associated with each of the combinations represented in FIG. 5, via the connector 7 by the cable 6 to the secondary computer 9 in order to generate visual information representative of the actual physical situation on screen 3. As For example, this visual information can be a vector or an arrow indicating to the subject the inclination of his body and encouraging him to rectify his postural situation. It is then a biofeedback operation. The aforementioned arrow can be replaced by a visual stimulus such as the representation of an animal or an object, and color can advantageously be used.

 The same method can be used to operate computer games previously put into action by the manipulation of a broomstick, or of a joystick or a mouse. Thus, the invention can also be used for training and rehabilitating pedal motor skills as well as for stimulating intentional pedal and postural reactions.

 The main steps of the posturography method according to the invention can be grouped into four parts, with reference to FIG. 6.

The first part I relates to all the inputs of the system according to the invention
- the pulse signals generated by the sensors,
- experimental parameters, for example, test duration and calibration data,
- data relating to the subject, for example, name, age, weight and height,
- information relating to the course of the postural test.

 In a first calibration phase, with reference to FIG. 7 and to FIG. 1, the signals from the sensors C1-C4 in the absence of a subject are checked automatically: with a reference voltage is associated a standard pressure and the input is modified in order to cancel the output signals in the absence of subject At this stage, the operator enters a test duration (in seconds) and a standard pressure (for example, in kg).

After verification of this calibration phase, the program associated with the system 1 according to the invention and stored in the hard disk of the first microcomputer 2 is ready for the acquisition phase. This acquisition phase begins with the entry of relative data. to the subject to be tested, in particular his name, his age, his height and his weight, information defining postural positions that the subject will have to take and messages inviting the subject to place himself on the sensor device 14. When the subject installed himself on the sensor device 14 and placed himself in the requested position, the operator initiates the acquisition of experimental data from sensors C1-C4, which are stored on the hard disk of the microcomputer 2. At the same time, these data are displayed in the form of graphs on the screen of the microcomputer 2. When the test time has elapsed, an indication of end of test is given by the operator or experimenter to the subject. and the acquisition is interrupted.

The acquired data are then transferred to a floppy disk (not shown) according to techniques now well known to those skilled in the art in the field of microcomputing. This transfer is accompanied by the input by the experimenter of comments and indications on the progress of the test session. These indications will be very useful for the further exploitation and interpretation of the experimental results. The data acquired and stored on a floppy disk can possibly be erased from the hard disk so as not to clutter it unnecessarily. The program then causes a return to a new acquisition phase.

The second part of the method according to the invention relates to the main or primary processing II of the data carried out within the microcomputer 2. Two types of processing can currently be envisaged
A) a Fourrier transformation treatment,
B) an analysis of chaos.

In case A, a Fourier transformation is performed for each signal separately and for each position taken by the subject. The Fourier spectrum is then subdivided into frequency bands, for example
F1 0 - 0.1 Hz
F2 0.1 - 0.25 Hz
F3 0.25 - 0.35 Hz
F4 0.35 - 0.50 Hz
F5 0.50 - 0.75 Hz
F6 0.75 - 1.00 Hz
F7 1.00 - 3.00 Hz
F8 3.00 and above.

The distribution of the subject's weight on each of the plates is then calculated. The data is filtered by convolution with SINC mathematical functions. A STI stability indicator is then calculated from a set of data acquired on each plate; as an example, if we call Ai, Bi, Ci and Di the data respectively from plates P1, P2, P3, P4 at each pulse i, if we consider a measurement frequency of 40 Hz and if we calculate this index stability over a period of 1 second, the expression used to calculate the STI stability index is

SYN synchronization scores are then produced for each acquisition i from the following formula

 In the case of chaos analysis processing, the acquired chaos is compared to random signals. the degree of periodicity of chaos signals is compared to that of normal postural signals.

 The two methods of treatment mentioned above can of course be combined to support a diagnosis or a statistical study.

 The third part III of the method according to the invention relates more particularly to treatments with a view to the exploitation and display of posturographic results.

First, the frequency ranges of the Fourier spectrum are converted into percentages, then spectral quotients SPQ1, SPQ2, SPQ3 are calculated according to the following formulas
F1x100
SPQ1 = F2 + F3 + F4
FtxlO
SPQ2 = F5 + F6 + F, + F8
F1
SPQ3 = F7 + F8
A WDI weight distribution index is also calculated according to the following expression

where A ', B', C 'and D' are the respective percentages of the total weight of the subject on each plate P1
P4.

In addition, an STQ stability quotient is calculated using the following expression
STQ = STI x 100
STQ M
where STI is the aforementioned stability index and M represents the weight of the subject.

 Of course, the present invention is not limited to the examples which have just been described and numerous modifications can be made to these examples without departing from the scope of the invention.

 Thus, the size and arrangement of the plates of the sensor device can be adapted according to particular physiological situations.

 In addition, any type of computer or microcomputer, portable or fixed, of PC compatible type or not, can be used for the processing of the experimental data, provided that it can receive digital data and allow the visualization of graphics and data storage. In addition, the acquisition card can be placed both inside and outside the microcomputer.

 Data processing can be carried out either from the acquisition microcomputer 2, or offline and remotely on another computer.

 The second calculator provided for displaying visual indications and stimuli can be dedicated only to this function or else be used for other functions. The screen used can be of any size and technology and placed according to physiological criteria defined by the experimenter.

 It is also possible to provide more than one independent sensor per independent plate, and / or more than four independent plates.

 Similarly, it is possible to use other types of sensors than the piezoelectric sensors described, for example strain gauges measuring a force exerted on the corresponding plate.

Claims (21)

 1. Tetraataxiametric posturography method, comprising a step of acquiring signals (S1-S4) from sensor means (C1-C4) included in a sensor device (14) on the upper face (P) of which a subject is standing substantially in equilibrium, and a first step of processing said signals (S1 S4) to deliver information representative of the posture of said subject and of the temporal evolution of said posture1 characterized in that at least four measurement signals (S1-S4) respectively representative of the pressures exerted by each toe and each heel of the subject are generated by at least four independent sensors (C1-C4) representing said sensor means and associated with at least four independent plates (P1 P4) receiving respectively the two toes and the two heels of said subject, and in that the processing step comprises a step of analysis and interpretation of the interactions existing between these at least four measurement signals (S1-S4 ).  2. Method according to claim 1, characterized in that it further comprises a so-called bioreaction step during which the subject receives bio-feedback information, in particular visual information substantially indicative of his instantaneous posture, and in that these bio-feedback information is obtained during a second step of processing said four measurement signals (S1-S4).  3. Method according to one of the preceding claims, characterized in that the acquisition step comprises a step of shaping and amplification of the four measurement signals (S1-S4) from the four independent sensors (C1- C4), followed by a step of analog multiplexing of said measurement signals (S1-S4), of a step of analog / digital conversion to generate multiplexed digital information transmitted to first control and processing means (2).  4. Method according to one of the preceding claims, characterized in that, prior to positioning the subject on the upper face (P) of said sensor device (14), a step of adapting the dimension of said plates (P1 , P'1, P "1) to the morphology of the feet of said subject.  5. Method according to one of the preceding claims, characterized in that the acquisition step further comprises an entry by an operator of information relating to the posturography session in progress, in particular experimental parameters and relative personal data about test.  6. Method according to one of the preceding claims, characterized in that said first processing step comprises a main processing sub-step (II) in which the four signals (S1-S4) are processed to generate raw information representative of the posture of the subject, followed by a secondary processing sub-step (III) in which said raw information is processed to provide a predetermined set of quotients and scores for a later interpretation of the results of this posturography session.  7. Method according to claim 6, characterized in that it comprises, after said second secondary processing sub-step (III) an output step (IV) in which said quotients and scores are processed to be viewed and stored .  8. Method according to one of claims 6 or 7, characterized in that the first main processing sub-step (II) further comprises processing said information entered by chaos analysis at the end of which analysis information of chaos are generated and represented graphically during said exit step (IV).  9. Method according to one of the preceding claims, characterized in that it further comprises a posturography session management step comprising a preliminary step of calibrating said sensor device (14), an acquisition launching step, and an end of session indication step.  10. System (1) of tetraataxiametric posturography, implementing the method according to one of the preceding claims, comprising a sensor device (14) on the upper face (P) of which a subject is standing substantially in equilibrium, characterized in that that this device (14) comprises at least four independent sensors (C1-C4) placed under at least four independent plates (P1-P4) on which the toes and heels of said subject rest respectively, and in that said system comprises first control and processing means (2) connected to the multisensor device (14), for receiving and processing at least four measurement signals (S1-s4) generated by said at least four independent sensors (CI-C4) in order to provide information representative of the posture of said subject.  11. System (1) according to claim 10, characterized in that said four plates (P1-P4) comprise two plates of substantially rectangular shape (P1, P3) for receiving the two points of said subject and two plates of substantially square shape (P2 , P4) to receive the two heels of said subject.  12. System (1) according to one of claims 10 or 11, characterized in that it further comprises bio-feedback means (3,9) to provide the subject, in particular in visual form, with information indicative of its own posture, said bio-feedback means (3,9) being connected to the multi-sensor device (14) and receiving therefrom data representative of the distribution of pressures between the four plates (P1 P4).  13. System (1) according to one of claims 10 to 12, characterized in that the first control and processing means (2) comprise a first microcomputer.  14. System (1) according to one of claims 10 to 13, characterized in that the bio-feedback means (3,9) comprise a display screen (3), in particular the screen of a second microcomputer ( 9).  15. Multisensor device (14) used in the posturography system (1) according to one of claims 10 to 14, characterized in that it comprises on its upper face (P) at least four independent plates (P1- P4) of predetermined dimensions and arrangements under each of which is placed at least one independent sensor (C1-C4), and in that it further comprises means (11) for supplying electrical energy, means for collecting the measurement signals (S1-S4) generated by said sensors (C1-C4), and means (A1-A4,12) for processing these signals (S1-S4) with a view to transmitting them to first means of control and treatment (2).  16. Device (14) according to claim 15, characterized in that the supply means (11) are connected at the input to the mains network (S) and deliver at output several predetermined DC voltage levels (Vp, Vc) to supply the sensors (C1-C4) and the signal processing means (AI-A4,12).  17. Device (14) according to one of claims 15 or 16, characterized in that it comprises, as signal processing means, means (A1-A4) for amplifying the four measurement signals (S1 S4) in analog form and means (12) for converting these amplified analog signals into digital information.  18. Device (14) according to claim 17, characterized in that it further comprises, as signal processing means, means for multiplexing said amplified signals before their conversion by said means for converting into multiplexed digital information .  19. Device (14) according to one of claims 15 to 18, characterized in that it further comprises first means (8) for connecting the signal processing means (12) to the first control and processing means (2).  20. Device (14) according to claim 19, characterized in that it further comprises means (13) for generating, from the four measurement signals (S1 S4), data indicative of the distribution of pressures on the four plates (P1-P4), and second means (7) for connecting said generator means (13) to bio-feedback means (3, 9).  21. Device (14) according to one of claims 15 to 20, characterized in that its upper face (P) is arranged to receive removable plates (P1, P'1, P "1) of variable size chosen according to the size of the subject's feet.