WO2019076461A1

WO2019076461A1 - Insole with sensors

Info

Publication number: WO2019076461A1
Application number: PCT/EP2017/076721
Authority: WO
Inventors: Nathan Smith
Original assignee: Nathan Smith
Priority date: 2017-10-19
Filing date: 2017-10-19
Publication date: 2019-04-25

Abstract

A shoe insole with monitoring capabilities is hereby described, the insole of the invention comprises data acquisition means define by a plurality of sensors. Said plurality of sensors are aimed to obtain data related to pressure exerted by the user when walking or running, relative humidity inside the shoe or temperature inside the shoe; the data acquisition means are complemented by gyrometers that may generate angle, acceleration and direction data that can be useful to process the data output generated by the sensors. Likewise, data generated by one sensor can account to process any data produced by any other sensor, and vice versa.

Description

INSOLE WITH SENSORS

OBJECT OF THE INVENTION The invention herein disclosed belongs to the technical field of sensing devices oriented to sport, fitness and health activities.

More precisely, the object of the invention is an insole for shoes, preferably but not limited to for sport shoes.

BACKGROUND

An insole is an inside sole of a shoe, which most of the time is removable and defined by a loose thin strip placed inside a shoe; insoles may provide warmth, isolation, and extra comfort. Insoles are also referred to as footbeds and inner soles.

Since shoes come in pairs, insoles tend to come in sets of two, although some user may prefer to have different insoles for each foot, or just one insole. People often replace the original insoles with a pair of specialty insoles they have purchased separately for a more comfortable and supportive fit or for extra features like control odour and moisture, and absorb shocks. For health-related reasons orthotic insoles can better position and support the foot. These are called aftermarket insoles.

The insole is in direct contact with the foot when the shoe is worn barefoot, or with a sock when the foot is covered by a sock; either way the insole is the part of the shoe which contacts the plant of the foot; therefore, it is directly associated to said part of the foot; insoles run underneath and support the bottom of the foot. Shoe wearers want a more comfortable fit and a more lightweight shoe, so insoles are mainly manufactured from a thermoplastic material, a plastic polymer that is heated and moulded to the shape of the foot, providing greater comfort and arch support like the insole disclosed in US 7793433 B2 where it is provided an insole with at least one layer made of thermoplastic material, which material is chosen from a group of ABS, PVC, A-PET and PETG. Feet take a lot of stress, and when that stress is not properly absorbed it can cause serious pain in ankles, knees and hips. Insoles may absorb shock, evenly distribute weight and provide arch support. Improper foot care can lead to all kinds of health issues, so it's important to take care of the feet.

But in order to take proper care of the foot we need to be able to control said weight distribution, shock dampening or monitoring activities related to the feet it is necessary to be able to gather some data related to any activity that may involve the feet. Temperature analysis has been considered as a complementary method in medical evaluation and diagnosis. Several studies demonstrated that monitoring the temperature variations of the feet of diabetic patients can be helpful in the early identification of diabetic foot manifestations, and also in changing behaviours, which may contribute to reducing its incidence. In Sousa, Paola et al. "A review of thermal methods and technologies for diabetic foot assessment system, based on electric contact thermometry" Expert Review of Medical Devices (Volume 12, 2015 - Issue 4) is disclosed a smart insole that integrates temperature and pressure sensor arrays. The sensors' temperature information is analysed in real-time and an alert is emitted if there are temperature variations that indicate ulcer formation.

Sometimes, an ex post facto analysis of the insole may provide information about the use of the insole, hence about the activities carried out while wearing the insole; for example: gait analysis. Gait analysis is the systematic study of animal locomotion, more specifically the study of human motion, gait analysis is used to assess and treat individuals with conditions affecting their ability to walk. It is also commonly used in sports biomechanics to help athletes run more efficiently and to identify posture-related or movement-related problems in people with injuries. The study encompasses quantification (i.e. introduction and analysis of measurable parameters of gaits), as well as interpretation, i.e. drawing various conclusions about the animal (health, age, size, weight, speed etc.) from its gait pattern. Gait analysis is also applied in the clinical environment, where it is fundamental for the assessment of gait pathologies, the prevention of pressure ulcers in diabetes or the assessment of the course of an orthopaedic disease. In addition, gait analysis carried out for sport purposes is aimed at helping athletes to gain a high level of performance, while minimising the risk of injuries. Finally, scientific research laboratories use gait analysis with the aim to study mechanisms of human musculoskeletal system and cerebral apparatus. Each of these application fields uses different gait analysis techniques to pursue specific aims.

Nowadays, new development in sensing technology and advanced materials allow a real-time analysis, monitoring and data captioning of information related the use of the shoe, more precisely how, what, when and where a user is using a shoe by means of data gathering insoles. For instance, JP2017000522 provides an information processor capable of giving an instruction for motion to a user by using a detection result of a weight of a sole. The information processor includes a weight distribution information generation part for acquiring weight distribution information of a sole on the basis of weight detection information detected by a pressure sensor provided on a sole of a user, and an instruction information generation part for generating instruction information to be reported to the user on the basis of the weight distribution information.

Insole pressure monitoring techniques encompasses: force platforms, pedobarographs and pressure-sensitive foot insoles. Force and pressure platforms are very reliable and accurate devices, thanks to their very sensitive and high-frequency sensors (sensitivity is up to 1 μΝ, sampling frequency can reach 200 Hz); these devices can be used for both static and dynamic studies, like for assessing balance, posture and gait. Pedobarographs are characterized by extremely high spatial resolution, that can reach 1 mm. Nevertheless, both force platforms and pedobarographs are affected by several limitations such as high encumbrance, high weight and the lack of portability, which restrict their application to clinical or research laboratories. Moreover, force platforms are affected by the "targeting" effect, that significantly alters the normal gait of the subjects A good example of a pressure-sensitive foot insole is disclosed in Crea, Simona et al. "A Wireless Flexible Sensorized Insole for Gait Analysis." Sensors (Basel, Switzerland) 14.1 (2014): 1073-1093. PMC. Web. 4 July 2017; which discloses a pressure-sensitive foot insole for real-time monitoring of plantar pressure distribution during walking. The device consists of a flexible insole with a plurality of pressure- sensitive elements based on an optoelectronic technology and an integrated electronic board for high-frequency data acquisition, pre-filtering, and wireless transmission to a remote data computing/storing unit. This document also provides information related to one of the problems solved by the object of the invention, namely when a high portability is desired, or measurement of pressures at foot-shoe interface is required, pressure-sensitive insoles appear to offer the best trade-off in order to perform gait analysis. Their use is however limited to applications that do not need extremely precise measurements. Two main aspects are important when dealing with pressure- sensitive insoles: the technology used for sensors; the actual information that can be extracted.

In the last years, examples of sensorised insoles based on different sensing technologies have been developed and commercialized, despite that fact all of these systems have shown their usability in gait analysis applications, some limitations are known, such as: the flexible contact surface may distort unpredictably, causing undesired variations of the sensor response; the output may drift when the load is applied for long time, mainly due to the heat inside the shoe; and subject-specific calibration procedures may be needed and may alter measurement accuracy. The limitations of the prior art do not merely account for the ones cited above, but also for the devices of the prior art providing a relatively small number of sensitive elements, which are positioned in correspondence of specific anatomical shape, and lead to a reduced spatial resolution and a consequent difficulty to reconstruct an accurate pressure map under the foot sole. The devices of the prior art also require time-consuming subject-specific calibration procedures and, in some cases, said devices store acquired data into an internal memory without an on-line data transfer to a remote computing/storing unit thus preventing them from being used in applications of real-time gait analysis. Some of those limitations are associated with the sensing means used thereof, in this sense US 9510776 B2 discloses an insole sensor which body is furnished with a plurality of recessed regions formed at respective locations corresponding to vertexes of N-polygon, where N is an even number, a plurality of first protrusions formed in odd recessed regions of the recessed regions, where each of the first protrusions has a first height, and a plurality of second protrusions formed in even recessed regions of the recessed regions, where each of the second protrusions has a second height different from the first height. Here, the body is formed with a nonconductive material, each of the first protrusions is formed with a conductive material, and each of the second protrusions is formed with a conductive material.

Sometimes, problems are tackled by adding different sensors such as the insole disclosed in CN205813736, the insole described thereby comprises an upper portion central point of shoe -pad body is associated with a first pressure sensor, whereas the lower part central point of shoe -pad body is associated with a second pressure sensor; both pressure sensors being arranged in the inner sandwich of the insole body and connected with a FPC line body receiving device through an electrical data line, the FPC line body receiving device adopts the wireless transmission connection data acquisition. A processor is provided with a protective layer, a pressure sensor and a gas permeable layer from top to bottom, and the pressure sensor is provided with a protective film on both sides of the pressure sensor.

DESCRIPTION The insole of the invention is aimed to solve the problems found in the art. The insole of the provides further inputs and monitoring functions that allow to overcome the limitations of the insoles known in the art, in this sense, the insole of the invention is preferably furnished with sensors, a battery, a microcontroller and a transmitter; both microcontroller and transmitter may be comprised in a single chip, actually the whole set of microcontroller, sensor and transmitter may be comprised on one single device. In some embodiments of the invention a battery may be completed with, or even substituted by, a kinetic system wherein the power for the device is generated using the motion and weight of the wearer. The insole of the invention relies on data gathered by data captioning means, such as pressure sensors which may be fabric-based, flexible, and stretchable sensors, which are capable of seamlessly covering natural shapes. As humans have curved body parts that move with respect to each other, the practical usage of traditional rigid sensor arrays is limited. Rather, a flexible skin alike sensor is preferred for the footbed. In some embodiments of the invention the insole may be comprise a battery, in this case surplus energy can be stored or used to charge other devices such as smart watches and mobile phones.

Preferably, the insole of the invention comprises a pressure sensor covering the whole base of the insole, this feature may be rendered by a pressure sensor material layer arranged on along the whole surface of the insole; since any pressure sensor output data may be supported by other sensor outputs, the pressure sensor layer may be arranged on top of the insole, on the bottom layer of embedded in the insole body or base.

DRAWINGS

In order to complement the description that is being made and in order to aid a better understanding of the characteristics of the invention, according to a preferred example of practical implementation thereof, a set of drawings is attached as an integral part of said description in which, with an illustrative and non-limiting character, the following has been represented:

Figure 1 .- Shows an exploded view of the insole of the invention that depicts the relationship and order of assembly of the parts of the insole. Figures 2a, 2b.- Show a representation of the layers of the pressure sensor. Figure 2a shows the different layers forming the pressure sensor whereas figure 2b depicts an arrangement of said layers.

PREFERRED EMBODIMENT

In a preferred embodiment of the insole object of the invention, the insole comprises a base (1 1 ) which is preferably made from plastic material and sealed with a lid, also preferably made of plastic; as the skilled person would acknowledge any other suitable material or a more specific plastic may be used. The plastic base (1 1 ) comprises a microcontroller (3) and, in some embodiments of the invention it may also comprise a battery (4). The insole (1 ) of the invention comprises a plurality of data acquisition means which may be arranged along the base (1 1 ), said data acquisition means may be selected from: gyrometers (21 ), heat sensors (22), moisture sensors (23) and pressure sensors (24) like the Velostat material sensor. The data acquisition means produces output data that allows the microcontroller (3) to calculate data such as: Weight of wearer, foot strike, weight distribution, foot pronation, moisture and heat.

In a preferred embodiment of the invention the pressure sensors (24) are preferably flexible and may be defined by a pressure and/or bend sensitive conductive sheet made from "velostat" or "Linqstat", which is a conductive material that is pressure- sensitive: squeezing it will reduce the resistance, so it is suitable for making flexible sensors.

Changes in material resistance may be measured by the data acquisition means, for instance a change in the structure of the plastic material of the base may be measured by the pressure sensors (24) but also aided or complemented by input coming from the output generated by the heat sensors (22) , which may be calibrated to the features and mechanical properties of the material of the base (1 1 ) of the insole (1 ) so when a certain threshold value is determined by the heat sensors (22), they produce an output so that the microcontroller (3) adjust the data captioned by the rest of the sensors, i.e. the pressure sensors (24) using the output generated by the heat sensors (22) as input for the pressure sensors (24) may tune the output generated by the pressure sensors (24) so the microcontroller (3) may use this tuned output generated by the pressure sensors (24) for accurately calculating any of the: weight of wearer, foot strike, weight distribution, foot pronation, etc.

The presence of moisture sensors (23) in the insole provides the microcontroller (3) relative to humidity, moist and even dew point inside the show, so any input generated by the rest of the data acquisition means may be adjusted accordingly, similarly to the input generated by the heat sensors (22) the output produced by the moisture sensor (23) may be used as input data to calibrate or set up the rest of the data acquisition means or to tune, calibrate, correct or adjust, by means of the microcontroller (3) any data produced. Hence, as per the heat sensors (22), the microcontroller (3) may use a tuned output generated by the moisture sensors (23) for accurately calculating any of the: weight of wearer, foot strike, weight distribution, foot pronation, etc.

The calculation of foot pronation may be assisted by an output generated by gyrometers (21 ); in this sense, foot pronation (for both feet or for each foot individually) may be calculated by the microcontroller (3) having as input any output data generated by the gyrometers (21 ). Since foot pronation may be also related to the weight of the user, the calculation of said weight may be carried out taking into account the tuned output generated by the pressure sensors (24), which is tuned using data generated by either or both heat sensors (22) and moisture sensors (23). The microcontroller (3) software may be developed with The open-source Arduino Software (IDE)', many microcontrollers boards are compatible with this IDE. The IDE can be extended to work with many boards. The software on the board reads the data generated by the data acquisition means and relays them (via wireless communications) to the software running on connected device. Some data processing (sampling, and environmental correction) is done within the software on the microcontroller.

Power needed for the data acquisition means and the microcontroller (3) to operate may be generated by a kinetic power generator (5) which may provide energy to the components of the insole (1 ) and also may charge the battery (4) when provided.

In a preferred embodiment shown in figure 1 of the invention the insole (1 ) is a multilayer monolithic item wherein each layer comprises the data acquisition means ; in this sense a top layer may comprise the moisture sensors (23), then a middle layer may comprise the heat sensors (22) and a lower layer may comprise the pressure sensors (24); the gyrometers (21 ), when arranged, may be arranged on an individual layer or embedded in any of the layers or in any other suitable location in the insole (1 ) or the plastic base (1 1 ). In a preferred embodiment of the insole (1 ) of the invention shown in figure 2b, the layer comprising the pressure sensors (24) is pressure/bend sensitive sheet.

The sensitive sheet may be based on a piezoresistive effect based sensing sheet formed by layers (241 ,242,243) of different plain and conductive fabrics as depicted in figure 2a and 2b, ensuring good elasticity of the compound sensor; a piezoresistive, stretchable knitted fabric (72% nylon, 28% spandex) is a more than suitable selection. Then individual fibres within the fabric may be nanocoated with conductive materials like polymers; the thickness of the coating will determine the material resistance; rendering the material available at different resistances, determined by the thickness of the applied coating; a material with a volume resistivity of approximately 20kQ m seems to be the most suitable.

By arranging a piezoresistive material layer (242), in this particular embodiment shown in figure 2b with a thickness comprised between 0.3mm and 0.5mm, between two highly conductive material layers (241 ), in this particular embodiment with respective thickness comprised between 0.1 mm and 0.3mm, it is observed a change in the resistance measured at the highly conductive material layers (241 ) when pressure is applied. The outer layers, namely the highly conductive material layers (241 ), constitute the low impedance electrodes that transport current into and out of the pressure sensor (24) with minimal losses. An additional non-conductive material meshed layer (243) may be added between the piezoresistive material layer (242) and one of the electrode layers (241 ) , it is noted that sensitivity also depends on the thickness of the non-conductive material meshed layer (243) and on the size of the mesh openings, with larger openings and thinner layers providing better sensitivity; by adding this additional non-conductive material meshed layer (243) with a honeycomb structure, the pressure sensor (24) yields a very high resistivity when not acted upon, which is achieved by the introduced gap between the highly conductive material layers (241 ) and the piezoresistive material layer (242). This configuration renders an insole (1 ) which is sensitive to subtle forces.

The data acquisition means and the microcontroller (3) are linked in such a way they can respectively communicate and transfer data, this may be accomplished wirelessly or using a wired connection such a conductive mesh communicatively connecting the different electronic parts of the insole (1 ).

Claims

Insole (1 ) for a shoe, comprising sensors:

• a base (1 1 ) preferably made of plastic material, and

• a microcontroller (3) linked to at least one pressure sensor (24) arranged in the base (1 1 ),

the insole (1 ) being characterised by the microcontroller (3) being further linked to at least one of:

o a moisture sensor (22) and

o a heat sensor (23),

so that an output of at least one the moisture sensor (22) and the heat sensor (23) is an input for the pressure sensor (24).

Insole (1 ) for a shoe, according to claim 1 further comprising a battery (4). Insole (1 ) for a shoe, according to either claim 1 or 2 further comprising kinetic power generator (5).

Insole (1 ) for a shoe, according to claims 2 and 3 wherein the kinetic power generator (5) is connected to the battery (4) for charging said battery (4).

Insole (1 ) for a shoe, according to any one of claims 1 to 4 further comprising a gyrometer (21 ).

Insole (1 ) for a shoe, according to any one of claims 1 to 5 wherein the pressure sensor (24) comprises in turn:

a piezoresistive material layer (242) arranged between two highly conductive material layers (241 ), and

a non-conductive material meshed layer (243) arranged between the piezoresistive layer and one of the highly conductive material layers.