Deep-body-temperature estimation system, heat stress warning system, and deep-body-temperature estimation method

1. A deep-body-temperature estimation system comprising:

a temperature sensor configured to measure a temperature inside clothes being a temperature inside the clothes worn by a user;

an acceleration sensor configured to detect an acceleration applied to the user; and

a hardware processor configured to estimate a heat production amount based on the acceleration detected by the acceleration sensor, the heat production amount being a heat amount generated inside a body of the user, and estimate a deep body temperature based on (i) the temperature inside the clothes measured by the temperature sensor and (ii) the estimated heat production amount, the deep body temperature being a temperature inside the body of the user, wherein

the hardware processor estimates the deep body temperature by using a mathematical model indicating a correspondence relation among the temperature inside the clothes, the heat production amount, and the deep body temperature,

the mathematical model is expressed by a simultaneous differential equation comprising:

a first equation where an amount of change in a first heat amount is expressed by a difference between the heat production amount and a first heat flow amount that is a heat flow amount supplied from muscles of the user to a blood of the user, the amount of change in the first heat amount being a heat amount of the muscles of the user,

a second equation where an amount of change in a second heat amount is expressed by a difference between the first heat flow amount and a second heat flow amount that is a heat flow amount supplied from the blood of the user to an inside of the clothes, the amount of change in the second heat amount being a heat amount of the blood of the user,

a third equation where the first heat flow amount is expressed by a ratio of a difference between an amount of change in a first temperature that is a temperature of the muscles of the user and the amount of change in a second temperature that is a temperature of the blood of the user to a first thermal resistance value that is a thermal resistance value from the muscle of the user to the blood of the user,

a fourth equation wherein the second heat flow amount is expressed by a ratio of a difference between the amount of change of the second temperature and the amount of change in the temperature inside the clothes to a second thermal resistance value that is a thermal resistance value from the blood of the user to the inside of the clothes,

a fifth equation where the amount of change in the first temperature is expressed by a ratio of the first heat amount to a first heat capacity that is a heat capacity of the muscles of the user, and

a sixth equation where an amount of change in the second temperature is expressed by a ratio of the second heat amount to a second heat capacity that is a heat capacity of the blood of the user, and

the hardware processor estimates the second temperature as the deep body temperature.

2. The deep-body-temperature estimation system according to claim 1 , wherein

the first heat capacity and the second heat capacity are values obtained based on physical features of the user, and

the first thermal resistance value and the second thermal resistance value are predetermined values.

3. The deep-body-temperature estimation system according to claim 2 , further comprising:

an air pressure sensor configured to detect an air pressure around the user, wherein

the hardware processor estimates the heat production amount based on the acceleration detected by the acceleration sensor and the air pressure detected by the air pressure sensor.

4. The deep-body-temperature estimation system according to claim 1 , further comprising:

an air pressure sensor configured to detect an air pressure around the user, wherein

the hardware processor estimates the heat production amount based on the acceleration detected by the acceleration sensor and the air pressure detected by the air pressure sensor.

5. The deep-body-temperature estimation system according to claim 1 , further comprising:

an angular rate sensor configured to detect an angular rate applied to the user; and

a magnetic sensor configured to detect a direction of a magnetic field around the user, wherein

the acceleration sensor, the angular rate sensor, and the magnetic sensor are fixed to one another, and

the hardware processor estimates the heat production amount based on the acceleration detected by the acceleration sensor, the angular rate detected by the angular rate sensor, and the direction detected by the magnetic sensor.

6. The deep-body-temperature estimation system according to claim 1 , wherein the hardware processor is further configured to provide notification of an abnormality of the user based on the estimated deep body temperature.

7. The deep-body-temperature estimation system according to claim 1 , wherein the clothes have a heat shielding effect.

8. The deep-body-temperature estimation system according to claim 7 , wherein the heat shielding effect satisfies a requirement in which the HTI 24 that is measured by a method defined in ISO 9151 is three seconds or more.

9. The deep-body-temperature estimation system according to claim 1 , wherein the clothes have an air permeability of 1.0 cm 3 /cm 2 /s or below measured by a method that is defined in JIS L 1096 and that uses a fragile type tester.

10. The deep-body-temperature estimation system according to claim 1 , wherein the clothes have a moisture permeability of 1000 g/m 2 /h or below measured by a method that is defined in JIS L 1099 and uses a cup method.

11. The deep-body-temperature estimation system according to claim 1 , wherein the clothes have a thermal conductivity of 1 kcal/h/m/° C. or below.

12. A heat-stress alarm system comprising:

a temperature sensor configured to measure a temperature inside clothes being a temperature inside the clothes worn by a user;

an acceleration sensor configured to detect an acceleration applied to the user; and

a hardware processor configured to estimate a heat production amount based on the acceleration detected by the acceleration sensor, the heat production amount being a heat amount generated inside a body of the user, estimate a deep body temperature based on (i) the temperature inside the clothes measured by the temperature sensor and (ii) the estimated heat production amount, the deep body temperature being a temperature inside the body of the user, and generate an alarm based on the estimated deep body temperature,

wherein

the hardware processor estimates the deep body temperature by using a mathematical model indicating a correspondence relation among the temperature inside the clothes, the heat production amount, and the deep body temperature,

the mathematical model is expressed by a simultaneous differential equation comprising:

a first equation where an amount of change in a first heat amount is expressed by a difference between the heat production amount and a first heat flow amount that is a heat flow amount supplied from muscles of the user to a blood of the user, the amount of change in the first heat amount being a heat amount of the muscles of the user,

a second equation where an amount of change in a second heat amount is expressed by a difference between the first heat flow amount and a second heat flow amount that is a heat flow amount supplied from the blood of the user to an inside of the clothes, the amount of change in the second heat amount being a heat amount of the blood of the user,

a third equation where the first heat flow amount is expressed by a ratio of a difference between an amount of change in a first temperature that is a temperature of the muscles of the user and the amount of change in a second temperature that is a temperature of the blood of the user to a first thermal resistance value that is a thermal resistance value from the muscle of the user to the blood of the user,

a fourth equation wherein the second heat flow amount is expressed by a ratio of a difference between the amount of change of the second temperature and the amount of change in the temperature inside the clothes to a second thermal resistance value that is a thermal resistance value from the blood of the user to the inside of the clothes,

a fifth equation where the amount of change in the first temperature is expressed by a ratio of the first heat amount to a first heat capacity that is a heat capacity of the muscles of the user, and

a sixth equation where an amount of change in the second temperature is expressed by a ratio of the second heat amount to a second heat capacity that is a heat capacity of the blood of the user, and

the hardware processor estimates the second temperature as the deep body temperature.

13. A deep-body-temperature estimation method comprising:

measuring a temperature inside clothes that is a temperature inside the clothes worn by a user;

detecting acceleration applied to the user;

estimating a heat production amount based on the detected acceleration, the heat production amount being a heat amount generated inside a body of the user; and

estimating a deep body temperature based on the measured temperature inside the clothes and the estimated heat production amount, the deep body temperature being a temperature inside the body of the user,

wherein the estimating the deep body temperature further comprises estimating the deep body temperature by using a mathematical model indicating a correspondence relation among the temperature inside the clothes, the heat production amount, and the deep body temperature,

wherein

the mathematical model is expressed by a simultaneous differential equation comprising:

a first equation where an amount of change in a first heat amount is expressed by a difference between the heat production amount and a first heat flow amount that is a heat flow amount supplied from muscles of the user to a blood of the user, the amount of change in the first heat amount being a heat amount of the muscles of the user,

a second equation where an amount of change in a second heat amount is expressed by a difference between the first heat flow amount and a second heat flow amount that is a heat flow amount supplied from the blood of the user to an inside of the clothes, the amount of change in the second heat amount being a heat amount of the blood of the user,

a third equation where the first heat flow amount is expressed by a ratio of a difference between an amount of change in a first temperature that is a temperature of the muscles of the user and the amount of change in a second temperature that is a temperature of the blood of the user to a first thermal resistance value that is a thermal resistance value from the muscle of the user to the blood of the user,

a fourth equation wherein the second heat flow amount is expressed by a ratio of a difference between the amount of change of the second temperature and the amount of change in the temperature inside the clothes to a second thermal resistance value that is a thermal resistance value from the blood of the user to the inside of the clothes,

a fifth equation where the amount of change in the first temperature is expressed by a ratio of the first heat amount to a first heat capacity that is a heat capacity of the muscles of the user, and

a sixth equation where an amount of change in the second temperature is expressed by a ratio of the second heat amount to a second heat capacity that is a heat capacity of the blood of the user, and

the estimating the deep body temperature further comprises estimating the deep body temperature to be the second temperature.