The present invention relates to a garment for the acquisition of joint movement data using strain gauge sensors, which allows to record with high accuracy the movements made by the user of the garment, particularly for rehabilitation.

Background of the invention

Garments for the acquisition of joint movement data by using strain gauge sensors are known in the art. The drawback of the prior art garments, for example that disclosed in US 2100010379A1 to De Rossi et al., is that they do not provide reliable enough information relating to the movement of the joints.

The prior art sensors are arranged along all the joints until reaching the control electronics, thus making difficult to discriminate the movements of each joint without completely eliminating the influence of the other joints.

Description of the invention In order to overcome the prior art drawbacks, the present invention provides a garment for the acquisition of joint movement data by using strain gauge sensors, which is characterized in that it comprises at least two sensors for a joint, said sensors having a speed of response when shrinking lower than the speed of response when elongating. The present invention includes at least two strain gauge sensors for acquiring the data of a joint movement. For example, for the rotation movement, flexion/extension movement and/or adduction/abduction movement. This allows to improve the asymmetric inertial response of the sensor, so that the movement data acquisition may be performed more quickly and accurately

The strain gauge sensors used have an inertial behavior in the elongation different from the inertial behavior in the contraction (speed of response when contacting lower than the speed of response when elongating), resulting in an asymmetric inertial response which reduces the accuracy in the data acquisition. The presence of two or more sensors to study the movement of one joint allows to improve this response. According to a preferred embodiment, said garment comprises at least two sensors configured for acting complementarily during the data acquisition of a joint movement, said sensors being arranged such that during the joint movement at least one of those sensors provides a response signal to the elongation.

It has been observed that when working with at least two sensors, it is possible to combine the response signal of these sensors such that the estimated delay time for correcting the error in the measurement of the sensor response and of the movement is significantly reduced. As a result, the data acquisition rate of the garment is increased.

By this sensor arrangement a more linear acquisition of the measurement of the rotation and torsion angles is obtained, which facilitates achieving the calibration of the system. Furthermore, the erratic behavior of the elastomeric material of the sensors is also corrected. Advantageously, said garment comprises at least two sensors for acquiring data of the movement of a joint with one degree of movement freedom. For example, at least two sensors for acquiring data relating to a rotation movement of a joint selected among a human wrist, elbow, neck or ankle or, for example, at least two sensors for acquiring data of the flexion/extension movement of an elbow, a wrist or an ankle. Preferably, at least two of the sensors are arranged physically on opposite sides, one of said sensors being capable of stretching while the other one contracts during the joint movement.

More advantageously, the garment comprises at least three sensors for acquiring data of the movement of a joint with two degrees of movement freedom, for example, for acquiring data of the movement of flexion/extension and/or adduction/abduction of a joint selected from a neck, an elbow and an upper part of the leg.

Preferably, the ends of each one of said sensors comprises a fixation element formed by a foamy thermoplastic polymer, for example, a polymer of the EVA rubber type which is flexible but little deformable.

It has been observed that this fixation element is very convenient to prevent wrinkling of the tissue on which the sensor is arranged and to reduce the production of output signals or "noise" interfering with the measurement. The present invention allows the sensors to look at a single joint without being disturbed by the sensors from the environment by fixations in strategic areas.

According to various optional aspects of the present invention which may be combined wherever possible, the garment comprises at least a textile arm for the acquisition of data relating to the movement of a person.

According to a first embodiment, this garment comprises the following arrangement of sensors: a first sensor is arranged in the part beginning at the scapula and ending at the rear part of the elbow;

a second sensor is arranged in the part beginning at the pectoral and ending at the front part of the elbow;

a third sensor is arranged on the back of the hand;

a fourth sensor is arranged on the palm of the hand;

a fifth sensor is arranged in the rear part of the elbow;

a sixth and a seventh sensors are crossed or not arranged in the rear distal part of the forearm forming at least an angle of 30° between them,

an eighth sensor is arranged vertically under the armpit from the trunk

a ninth and a tenth sensors start at any point of the elbow and extend crossed or not crossed, ending at the elbow forming between them at least an angle of 30°.

an eleventh sensor which is arranged at the front part of the elbow. According to a second embodiment, the garment comprises the following arrangement of sensors: a first sensor 1 is arranged in the part beginning at the scapula and ending at the start of the forearm;

- a second sensor 2 beginning at the pectoral or at the upper part of the elbow and ending at the start of the forearm. ;

a third sensor 3 is arranged on the back of the hand;

a fourth sensor 4 is arranged on the palm of the hand;

a fifth sensor 5 is arranged in the rear part of the elbow;

- a sixth 6 and a seventh 7 sensor are crossed arranged forming an "X", or arranged in a "V" shape, forming at least an angle of 30° between them. an eighth sensor 8 is arranged vertically under the armpit from the trunk a ninth 9 and tenth 10 sensors start at any point of the elbow and extend crossed forming an "X", or arranged in a "V" shape, forming between them at least an angle of

30°

- an eleventh sensor 1 1 which is arranged in the front part of the elbow.

This second embodiment can reduce the number of parts of the pattern of the fabric piece, thus facilitating its industrialization. Advantageously, the garment is a ready-made garment such that at least one of the strain gauge sensors is printed on the fabric and, preferably, these sensors are made of a silicone elastomer.

More advantageously, the sensors and the fabric have a similar Young's modulus. The employed fabric may be, for example, a fabric based on 90% polyamide and 10% elastane, or any elastic fabric based on polyamide, polyester, cotton or viscose.

In the claimed garment, the connecting cables are arranged in a tunnel formed by the seams or embroideries.

According to a first embodiment, the garment comprises in the elbow a ring shaped fixation element joined to the internal surface of the garment, the fifth sensor being attached on the opposite side to that fixation element, such that its fixation is ensured in the correct position while in use. This ring is made of silicone.

Advantageously, both the first and the second embodiments of the garment comprise, joined to the textile arm, a sleeve for the thumb, such that the fixation is ensured in the correct position of the third and fourth sensors. Finally, the garment comprises a zipper in the front part of the forearm, preferably in the forearm and arm for providing a better fitting of the sleeve and ensuring an appropriate strain of the sixth and seventh sensors.

The manufacture of the claimed garment is suitable in mass-production and has a low material consumption because the sensors are located in strategic areas only. In the present invention, strain gauge sensor means a resistive strain gauge sensor, preferably a strain gauge sensor which does not necessarily follow the Hooke's law. This type of sensors allows to measure the deformation of a material, in this case produced by the elongation of its ends and having the property of changing their resistance with the variations produced in the total length of the sensor.

Advantageously, the material of the sensor should not be used such that its Young's modulus is exceeded, since it is preferable that the sensors try to meet Hooke's law. However, the present invention tries to overcome the fact that this condition is not met.

Brief Description of the Figures

For a better understanding of what has been outlined some drawings are attached which, schematically and solely by way of non-limiting example, disclose a practical embodiment.

FIG. 1 shows an asymmetric behavior of an elongation resistive sensor, in this case with a very slow response when shrinking.

FIG. 2 shows a front perspective view of a first arrangement of gauges or sensors according to the invention.

FIG. 3 shows a rear perspective view of the gauges arrangement of Figure 2.

FIG. 4 shows the cylindrical projection on the garment of the sensor path.

FIG. 5 shows the abduction of a joint with two degrees of freedom, at 45° with respect to its axis, and the location of three sensors.

FIG. 6 shows the abduction of a joint with two degrees of freedom, at -45° with respect to its axis, and the location of three sensors.

FIG. 7 shows the flexion of a joint with two degrees of freedom, at 45° with respect to its axis, and the location of three sensors. FIG. 8 shows the abduction of a joint with one degree of freedom, at 45° with respect to its axis and the location of two sensors. FIGS. 9 and 10 show the special arrangement in the elbow to ensure a correct positioning and measures. FIG. 1 1 shows the projected paths of a joint with a movement of rotation, with two sensors and with rotations from -270° to 270°.

FIG. 12 shows the projected paths of a joint with a movement of rotation, with two sensors and with rotations from -270° to 270°, crossed version.

FIG. 13 shows paths for three sensors of a joint with a movement of rotation from -360° to +360°

FIG. 14 shows a front perspective view of a second preferred arrangement of gauges or sensors according to the invention.

FIG. 15 shows a rear perspective view of the preferred arrangement of the gauges of Figure 14. FIG. 16 shows a set of plots (indicated by 0 to 3) to explain and schematically represent the effect of reducing the time delay in the correction of error in the measurement of two resistive sensors used to acquire the rotation movement data of a joint.

FIG. 17 schematically depicts a sensor arranged in the elbow with its ends fixed to the fabric using two foam rubber EVA pieces.

Description of two preferred embodiments

The invention relates to a garment P for the acquisition of joint movement data, using strain gauge sensors, which is characterized in that it comprises at least two sensors for acquiring data relating to a joint movement, having said sensors a speed of response when shrinking lower than the speed of response when elongating.

As already described above, the strain gauge sensors used (elongation resistive sensors) have a different inertial behavior in the elongation from the inertial behavior in the contraction (speed of response when shrinking lower than the speed of response when elongating), which results in an asymmetric inertial response which reduces the accuracy in the acquisition of data. The presence of two sensors for analyzing the movement of a sole joint allows to improve this response. The above behavior is represented in the graph of Figure 1 , which shows how the inertial behavior in the elongation is different from the inertial contraction behavior. Part of this inertia is determined by the stretching speed.

In the present invention, the garment P comprises at least two sensors configured for acting complementarily during the acquisition of data of a joint movement. These sensors are arranged such that during the joint movement at least one of the sensors provides a response signal to the elongation.

In particular, it has been observed that when working with at least two sensors, it is possible to combine the response signal of the sensors so that the estimated delay time to correct the error in the measurement of the sensor response and of the movement is reduced very significantly. As a result, the data acquisition rate of the garment P is increased.

The graph in Figure 16 shows a set of graphs depicting schematically the effect mentioned. In particular, this figure shows the reduction in the delay time in the error correction in the measuring of two resistive sensors used to acquire data of the rotational movement of a joint.

The graph "0" of Figure 16 includes a curve representing the measuring of the angle A (from -80 to 60 °) of rotation of the joint and another curve which represents the elongation E1 (4.2 mm to 4.7 mm) of a sensor during the rotation of the joint.

From these two curves it follows that, by turning clockwise the joint, the sensor is lengthened, while, when turning the joint counterclockwise, the sensor shrinks tending to recover its initial position.

The graph "1 " of Figure 16 includes a curve representing the measure of the resistivity R1 of a sensor during the rotation of the joint, and another curve representing the elongation E1 of this sensor during the rotation of the joint. In these curves, T1 and T2 data represent the time delay of response of the sensor when elongating T1 and shrinking T2, respectively, during the movement. These T1 , T2 delay times are estimated for reaching a 5% error in the measurement of the response and are related to the time required for the resistive sensor to stabilize.

From these two curves in Figure "1", the asymmetric inertial behavior of the sensors used is inferred, also similar to that shown in Figure 1. This behavior occurs because the speed of response of the sensor to shrink is lower than the response speed when lengthened, resulting in a time delay T2 of response when shrinking greater than the delay time T1 when elongating. When extending, the sensor decreases resistivity R1 and when it shrinks it tends to recover the initial resistivity R1 , however, as can be seen in the curve, the sensor takes a superior time T2 to recover the initial resistivity (lower speed response).

Graph "2" of Figure 16 adds to the curves in "1" a third curve representing the resistivity measure R2 of a second sensor which is arranged physically opposite the other sensor so that during movement, when a sensor lengthens, the other shrinks. Curve E2 represents the elongation of the second sensor. As can be seen from the curves, the sensors are arranged to act in a complementary manner (orthogonal behavior) upon the movement under study.

The graph "3" of Figure 16 includes two curves representing schematically the effect of reducing the time delay in the correction of error in the measurement of the two resistive sensors used and represented on the graph "2".

Of the two curves in Figure "3" of Figure 16, it follows that when working with at least two sensors, it is possible to combine the response signal of these sensors so that the estimated delay time to correct the error in the measure of the response of the sensor and the movement is reduced very significantly. As a result the data acquisition rate of the garment increases.

For a combined response of two or more sensors, the resistance values obtained should be properly weighted by giving more weight to the sensor that performs with more precision and less weight to the other, depending on the instantaneous settings of position and speed for each sensor.

Now, the arrangements of the sensors of the present invention with reference to Figures 1 to 15 and 17 will be described. a) Joint with movement of rotation As shown in Figure 4, the garment that is located on the joint axis must be affixed to both ends A and B, so that it moves integrally with the rotation of the joint and thus also twists the fabric and sensors. For this type of joint, the travel path of the sensors must be adjusted as maximum as possible to the cylindrical projection of a path or a segment thereof.

The path to follow in the cylindrical projection must meet that the cylindrical paths to be projected of each sensor must follow the shortest line on the cylinder of the joint if possible. At least there must be two sensors and between them they must comply:

(α _Γ βί)-(α _Μ - β _Μ )=360/Ν (where "i" satisfies N≥i>1),

Where N is the number of elongation resistive sensors employed, ai being the displacement angle from the starting point of the path of the sensor (i) on the A axis of each path, and βί is the displacement angle of the end of the path relative to axis B.

Furthermore, to act in a complementary manner, i.e. so that one of them always elongates more than the other sensors and so that all the possible movements of the joint are covered, for the intermediate state of rotation (if the rotation goes from + Θ to -Θ for the intermediate state rot = 0), the projection of the paths has to get as close as possible to the following arithmetical compensation:

i-S. As an example of this type of joint movement the rotation of the wrist can be mentioned. End A would be the elbow and end B the wrist, which rotates about the same axis (forearm). The rotation of the human shoulder, neck ankles would also be included in this type of movement.

Figures 11 to 13 show the cylindrical projection of the paths of two sensors 1 , 2 or three sensors 1 , 2, 3 used to acquire data of the rotational movement of a joint with one degree of freedom. b) Articulation with movement of flexion/extension and/or adduction/ abduction, with one or two degrees of freedom. This type of joint is shown in Figures 5 to 8. In this case, the fixation may be located anywhere in the cylinder although the best place are the ends A and B. The ends of the projection cylinder may extend along the joint, provided at least the cylinder portion that is twisted is covered.

It is also preferred that the path of the sensors fits maximally to a cylindrical projection of a path, or segment thereof, and the following conditions are met:

There must be at least three sensors for two degrees of freedom and at least two sensors for one degree of freedom.

Each of the paths of the sensors must follow the shortest line on the cylinder of the joint if possible, and at least one of the sensors must start and end in one of the planes of rotation and also between them they must meet:

(cii - a )=360/N (where i is such that N≥i>1)

(β _ί - β _Μ )=360/Ν (where i is such that N≥i>1)

Where N is the number of elongation resistive sensors employed ai being the displacement angle of the starting point of the path of the sensor (i) on the A axis of each path, and βί being the displacement angle of the end of the path relative to the B axis.

As examples of this type of joint, with two degrees of freedom on the flexion / extension and abduction / adduction movement, one can cite the neck, shoulder and upper leg. With one degree of freedom on the flexion-extension, one can cite the elbow, wrist and ankle.

Examples of complete garments

A first exemplary arrangement of sensors on a garment is illustrated in Figures 2 and 3.

Specifically, the garment is provided with at least a textile arm for the acquisition of data relating to the movement of a person, wherein: a first sensor 1 is arranged in the part beginning at the scapula and ending at the rear part of the elbow;

a second sensor 2 is arranged in the part beginning at the pectoral and ending at the front part of the elbow;

a third sensor 3 is arranged on the back of the hand;

a fourth sensor 4 is arranged on the palm of the hand;

a fifth sensor 5 is arranged in the rear part of the elbow;

- a sixth 6 and a seventh 7 sensor are crossed or not arranged in the rear distal part of the forearm, forming at least an angle of 30° between them,

an eighth sensor 8 is arranged vertically under the armpit from the trunk

- A ninth 9 and a tenth 10 sensor start at any point of the elbow and extend crossed or not crossed, to end at the elbow forming at least an angle of 30° between them, - an eleventh sensor 1 1 which is arranged at the front part of the elbow.

A preferred second example of arrangement of sensors in the garment P is shown in Figures 14 and 15: - a first sensor 1 is arranged in the part beginning at the scapula and ending at the start of the forearm;

a second sensor 2 beginning at the pectoral or at the upper part of the elbow and ending at the start of the forearm. ;

a third sensor 3 is arranged on the back of the hand;

- a fourth sensor 4 is arranged on the palm of the hand;

a fifth sensor 5 is arranged in the rear part of the elbow;

a sixth 6 and a seventh 7 sensor are crossed arranged forming an "X", or arranged in a "V" shape, forming at least an angle of 30° between them,

an eighth sensor 8 is arranged vertically under the armpit from the trunk

- a ninth 9 and a tenth 10 sensor start at any point of the elbow and extend crossed forming an "X", or arranged in a "V" shape, forming at least an angle of 30° between them.

an eleventh sensor 1 1 which is arranged at the front part of the elbow. This second embodiment or example allows for the reduction of the number of parts of the pattern of the fabric piece, thus facilitating its industrialization.

In the two examples of garments disclosed, the sensors 6, 7 are arranged physically on opposite sides for acquiring data relating to a rotation movement of an arm or of a wrist, and the sensors 9, 10 arranged in opposite sides for acquiring data relating to a rotation movement of the elbow. FIGS. 1 1 and 12 depict the cylindrical projection of the paths of these pairs of sensors 6, 7 and 9, 10. In these figures 1 1 y12, for clarity reasons, these sensors 6, 7 have been numbered with 1 and 2.

It is important to point out that the sensors 6, 7, may be also used for acquiring data of the movement of supination and pronation of the arm, or be employed to analyze the movement of rotation of the wrist.

In the same examples of the garment disclosed, the sensors 1 , 2, 8 are arranged physically on opposite sides for acquiring data of the flexion-extension movement and abduction of the elbow. FIGS. 5 to 6 represent the cylindrical projection of the paths of these three sensors 1 , 2, 8, with regards to flexion and extension, and FIG. 7, with regards to abduction. In these figures 5 to 7, for clarity reasons, the sensors 1 , 2, 8 have been numbered with the references 1 , 2, 3. Now regarding the sensors 3, 4, and the sensors 5, 11 , these pairs of sensors are arranged physically on opposite sides two and two for acquiring data of the movement of flexion and extension of the wrist 3, 4 and of the elbow 5, 1 1. FIG. 8 represents the cylindrical projection of the paths of these pares of sensors 3, 4 and 5, 1 1. Like in the other figures, for clarity reasons, the sensors 3, 4 and 5, 11 have been numbered with the references 1 , 2.

As shown in Figures 9 and 10, the garment may comprise in the elbow a fastener ring or a ring shaped fixation element, preferably made of silicone, attached to the inner surface of the garment, the fifth sensor 5 being fixed on the opposite side of said element, such that its fixation is ensured in the correct position in use.

Also a garment is conceived that has an attached sleeve for the thumb, such that it ensures the fixation in the correct position of the sensors 3 and 4.

A preferred embodiment of the garment has a zipper in the front part of the forearm and arm for providing a better fitting of the sleeve and ensuring an appropriate tension of the sensors sixth 6 and seventh 7. Moreover, the ends of the sensors will be attached by means of a fixation element 12 formed by a foamy thermoplastic polymer, for example, a polymer of the EVA rubber type. As mentioned, it has been observed that this allows to reduce the creation of interference signals caused by the wrinkles of the elastic fabric during movement.

Although reference has been made to a specific embodiment of the invention, it is apparent to one skilled in the art that the described garment is susceptible of numerous variations and modifications, and that all the details mentioned can be replaced with other technically equivalent, without departing from the scope of protection defined by the appended claims.