FR2513508A1 - Sensor system measuring pressure between patient and support - uses capacitive matrix to adjust oscillator frequency for coding and entry to memory to obtain display - Google Patents

Abstract

A capacitive matrix is subjected to pressure from a part of the body. Its different points are explored by pointer circuits for the columns and lines. The outputs of these circuits are connected to an oscillator which provides a variable frequency input to a gating circuit. A square wave generator provides a fixed signal for the gate and also steps the line pointer circuit through an AND gate receiving a reset signal from a bistable. The fixed frequency signal passes through an OR gate and addressing coder to a memory. The variable frequency gate output passes via another coder to the memory from which the data can be applied to a display.

Description

 Medical and paramedical activities often require knowledge of the pressures or points of impact exerted by the body or part of the body on a support. Whether it is a measure leading to simple knowledge, or aimed at therapeutic treatment, observations of pressures or points of impact are of two types.

i One, static (the patient is motionless)
a) in the standing position, we want to know what the pressures are,
partial or total, exercised by the feet and in general,
the lower limbs, on the ground or on any support.

b) In sitting or lying down, we want to know what are the
points of contact, or pressures from any
part of the body on a support (cabinet or laboratory examination)
or the contact points and pressures in an envelope which can
be a fixed laboratory device or a device intended for
be worn by the patient.

c) In any position, we want to know the pressures exerted
voluntarily for examination, limb, hand, fingers
with one hand, or any other part of the body that one would like to know
form or strength for comparison with a listed model or ta
quote.

* The other, dynamic (the patient is on the move) and we want to know the
pressures or impacts exerted mainly by the lower limbs,
on a support chosen by the practitioner or the patient himself, for example
ple, the pressures exerted by the foot on the sole of the shoe.

 These observations offer a certain number of difficulties depending on their nature, which are in general, the large number of measurement points resulting in a large number of connections, the heaviness, the dimensions or the excessive volume of all the devices which make them exclusively devices. non-portable laboratories. They sometimes cause the difficulty of observing the dynamic aspect even in the laboratory, but always prohibit observation outside the laboratory; for example, knowledge of the impacts and pressures exerted by the foot on the sole of the shoe after a period of activity (walking for example).

 In addition, these devices, when they exist, require information to be analyzed during the measurement phase, without allowing deferred analysis, very useful when the pressures or impacts depend in part on patient behavior (compensation, leakage, impaired movements , etc).

 The present invention relates to a device making it possible to measure and record the pressures exerted by a part of the body on any support in the various phases of a movement, and to view them at the same time or delayed.

The description which follows has as a support a podiatric application and precisely the observation of the pressures exerted by the foot on the sole of a shoe during the normal walking of the patient. This application, a special case of those which will be discussed below, is the most complex since it assumes a device which consists of - a pressure sensor with multiple points distributed in corresponding matrix
laying on the surface to be observed, light and thin; - an electronic set of pressure point information processing
by point; - a memory; - a device for viewing memory states.

Thus, with such an assembly, the implementation process is as follows: the patient receives one or more sensors in the form of a sole or an envelope at his size which he slides into the shoe of which impact of the foot (s) to be observed. After putting on his shoes, including this sole or this envelope, he takes a first "snapshot" of the pressures in the standing position, legs immobile, by the appropriate command in the device worn in an acceptable manner and connected to the sensor sole by a cable of connection. One understands by "stereotype", the exploration and the recording of all the pressures of the matrix.

After a certain period of activity (walking for example), it causes by another command, the taking of several "cliches" representing the evolution of pressures during a step.

 The viewing of the pictures takes place when the device comprising the memory is adequately connected to the viewing element which may be a light matrix, a printer, a screen, or any other device.

- In a preferred but non-limiting form of the invention, the sensor
pressure is achieved as follows (Figure 2).

Flexible insulating plates (A) alternate with metal sheets
(B) forming capacitors. According to a preferred form of the invention, the
plate is made of metallized elastomer on which a chemical attack has
bounded by straight or non-straight bands, lengthwise
for even plates and width for odd plates, # cons-
thus constituting a multilayer capacitor with a large nominal value of
capacity, whose general flexibility allows great crushing7
a large variation in capacity, does not interfere with the foot thanks to its thick
weak sister. The choice of band width is important.
small it exaggeratedly increases the number of points to observe, without
increase precision since the foot will make several points of
measure in the same way; too large, the measuring points are no longer
quite numerous and the information lacks interest. This width will therefore
chosen according to the size of the foot. The whole will therefore constitute
a capacitive matrix whose intersection points XiYi will be
variable CXiYi capacitors with the pressure exerted by the foot on
this matrix.

A connection, classic in its design, brings the connection wires
dement of the capacitive matrix that constitutes the sole, to the whole
electronic data processing. The layout in matrix
allows to decrease in a clear way, the number of connections compared
the number of points explored. If we assume X rows and Y columns,
the number of connections is X + Y which would be XY connections in
point by point technology.

In a preferred form of the invention, the electronic processing assembly
pressure information is constituted in the following way
(see figure 1).

Circuit 1 is an oscillator whose relaxation frequency depends
of capacitor CXiYi from point XiYi of the pressure sensor.

The different XiYi points are explored by a pointer circuit of co
lonnes, associated with a line pointer circuit, respectively designated
6 and 7 in figure 1. When for a given column all the rows
have been crawled by the pointer, this not only causes the return
at the line of the line pointer, but also the advance of a column of the
column pointer.

Decoupling 6 bis of columns and 7 bis of rows is necessary
so that the CXiYi capacitors are galvanically isolated from the circuit
and do not disturb the operation of oscillator 1.

Circuit 2 is an oscillator whose function is to generate a signal
square of fixed duration.

Circuit 4 is a logical AND which receives a variable signal depending
of CXiYi of circuit 1 and a fixed signal of circuit 2. The output of cir
cooked is therefore the logical addition of these two signals, i.e.
trains of impulses whose number represents the capacity, therefore the pres
received by the point XiYi explored.

It is the signal end edge of circuit 2 which causes advancement
a line from pointer 7 through circuit 3 which is a logical AND
and whose 2nd input is attacked by a circuit 5 (rocker RS)
which sets the number of matrix explorations in the following way
Case 1: only one exploration of the matrix is requested: this is the command
U which is used. The electrical duration of U being essentially going
reliable since it depends on the duration of the patient's support, it
is reduced to a fixed value of very short duration by a circuit 8
suitable monostable. The pulse from 8 causes the tilting of the
circuit 5 whose output, through circuit 3 allows the end front
signal 2 to advance the line pointer by one line.
that the last column has been explored, a signal appears on the output
Reset of circuit 6 which through circuit 9 which is a logical AND (of which
the other entry authorizes by its electrical level, the passage) causes
reverse switching (RESET) of circuit 5.

Case nb 2: several matrix explorations are requested: the number
exploration is fixed by the memory size whose corresponding signal
at the last address will be used in this circuit.

It is first the command V, then the command U, which will be used
by the patient.

The command V attacks a circuit 10 (flip-flop RS) via input 5 whose
additional output Q inhibits logic AND circuit 9. This inhibition
will last as long as the address pointer does not come, for
enter RESET from circuit 10, put the system back in the previous step.

The U command is then used to trigger the exploration as described above.
demment.

In one of the forms of the invention, the memorization is carried out in the ma
next.

The signal from circuit 2 is routed to an encoder 11 through a
circuit 12 which is a logical OR and the 2nd input of which will be useful for addressing the memory when reading its content; the outputs of the encoder 11 designate the measured addresses.

In Figure 1, 3 outputs of the encoder 11 have been shown. Their number depends on the memory size, that is to say on the number of "snapshots" per step which has been chosen.

At each address is stored the pressure information of the output of the circuit 4 through an encoder 15. In FIG. 1, 2 outputs of the encoder 15 have been shown. Their number depends on the number of pressure levels desired. In Figure 1, 4 pressure levels can be stored. Reading or writing will be selected by a button reserved for this purpose according to a diagram specific to the type of memory used. The voluntary reset of memory also. They are designated in Figure 1 by the letters
W (write), R (read), and RESET (reset).

All types of memories can be used. They condition the way of processing information.

Circuit 13 is a logical AND with, when necessary, inverting inputs so that the last memory address, and only this address, activates the input R of circuit 10, the operation of which has been explained previously.

In another form of the invention, the storage can be carried out by using a disc or a magnetic tape. The drive systems are specific to each manufacturer. The operating mode of the device would then be the simple starting of the scrolling of the disc or of the tape at the start of the observation period. In both cases, a large memory capacity is obtained.

In one of the forms of the invention, the display is carried out by a printer in which the characters would be spaced so that the writing: of successive lines delimits a series of aligned characters representing a column. The number of characters per line would be the number Y of matrix columns. The number of lines in the print would be the number X of lines in the matrix. The print characters can be numbers or letters, or symbols. The numbers and letters could be chosen in such a way that their surface area or their opacity is more than the absolute value of the number itself, representative of the pressure received by the sensor, the figure 8 (eight) is for example perceived as being representative of a pressure higher than O (zero).

The impression of relief can be increased by using symbols, as mentioned above. For example, a series of tiles ranging from white to black, passing through the number of shades of gray required (obtained by
hatching or dots in particular) can be used instead of chars
ters normally supplied by the printer.

Other visualizations are possible such as table XY, saved
graphic processors, video monitors (screen) diode matrix, etc.

All these visualization elements, with the appropriate interface circuits
required, can coexist in the same installation.

The invention is applicable whenever lton wants to detect if there is
or not pressure, or again, if the place or places where these pres
sions are correct in relation to the desired result or to a given model.

Or, in a non-exhaustive list
h in podiatry
- in a service equivalent to that rendered by the current podoscope.

In this case, no storage is necessary and the V311lC? IL
of the sensor is immaterial. The patient climbs on the sensor
sufficient space to receive both feet normally
spaced. Pressures are read or viewed on the vi device
sualisation, at the same time as these pressures are exerted.

- By inserting the sensor into the shoe with display # in
simultaneous or delayed after a period of walking. The precision
of the visualization can allow the drawing of the orthop # element -
dique aimed at correcting the defect observed, and examining its
effectiveness by a second observation including it.

a in limb rehabilitation
- for example with the hand, observing the pressures exerted by
fingers on the matrix and comparing those pressures to those
exercised by the other hand or a model listed.

a in physiotherapy
- the overall pressure compared to the lower limbs allows to learn
for example, the horizontality of the iliac bone.

The electronic and memory unit, comprising a material limited in vo
light and light and easy to use and easy to access
research "in an adequate realization, makes the whole fit to be
worn and operated by the patient without tainting the result of the measurements.

Claims (9)

1- Device for measuring and recording pressures, using us  medical and paramedical, characterized by a variatic sensor  of capacity sensitive in multiple points to the pressures which  are exerted on him, which, associated with a memory device  of these pressures and a display device allows, e  same time or delayed, to visualize the state of the pressures  are exerted on him. 2- Device according to claim 1 characterized in that led:  sensor is made in multilayer structure (reference A & B d  figure 2) which provides a high nominal capacity value  retaining a small thickness and great flexibility pi  putting to marry the most varied forms and to be inserted  in an envelope, a shoe for example, between the foot  the shoe, without hampering the walk of the one who received the ca]  tor. 3- Device according to claim 1 and 2 characterized in that q  said sensor has multiple measurement points arranged in n  this rows X, columns Y, making it possible to decrease n  ble the number of matrix / electronic system connections. 4- Device according to claim 3 characterized in that the  XY matrix is explored by a column pointer 6 and 6bis  a Z and Zbis line pointer, which is controlled by the  front edge of an impulse acting as a cone window  ge of circuit 2 and inside which is a ce  tain number of pulses representing the capacity Xi, Yi, at  through oscillator 1 (the pins of this claim  those of figure 1 plate I).  several shots.  commands of the U and V allow respectively the taking of a  5- Device characterized in that (part II of Figure 1) 1 6- Device according to claim 1 characterized in that  the set includes a memory (figure 1, section III, repè  14) of large capacity of integrated or magnetic type.  7- Device according to claims 1 and 6 characterized in that  said device comprises a connection connectable to a hub  display (Fifure 1, position IV, item 16) specific to  the user and first to view the status of the press  saved.  pressures.  or graphics whose form (or / and) the opacity represents the  said display device uses signs, symbol  8- Device according to claims 1 and 6 characterized in that 9- Device according to claim 1 and 4 characterized in that  said device is portable and has a control (Figure 1,  section II, marks U and V) accessible and maneuverable by the  patient.