Method and device for the objective determination of thermal seat comfort

Abstract

A method and device to objectively determine the thermal seat comfort characteristics is disclosed. Thermal conditioning units, comprising individually controlled cooling / heating elements 4 and individually controlled fan elements 5, are positioned at the seat 2 or back-rest surface 3 and temperature regulated airflow is introduced at predefined positions on and in the seat. After removing the thermal conditioning units from the sensing field of a thermal camera 10, temporal 2D temperature data is transmitted to the evaluation and output unit 15 for parameter determination and parameter output. The thermal seat parameters or characteristics may comprise thermal inertia or thermal capacity. Control signals are provided by control unit 12.

Description

21 08 24 Background of the Invention Several studies (e.g. DKV-Report 2021, I. Frobose and B. Wallmann-Sperlich) reveal that home office, driving, public transport commuting, office work, sedentary leisure activities such as watching TV, etc. lead in many European countries to more than eight hours on average that are spent sitting every day. The seat comfort is hence crucial for the well-being of people during this long time of daily use. Apart from ergonomics of a seat and properties of seat cover texture, the comfort also comprises seat hardness, strain- and shear forces and several further mechanical properties. Also thermal properties of the seat, such as thermal inertia or thermal capacity, play a crucial role if there is a prolonged stay in the seat. The individual anthropometric data of persons but also their subjective impression differs significantly and needs to be considered when finding an objective determination method, applicable to a wide range of users and user preferences. For the thermal comfort impression, the thermal seat surface information (e.g. thermal impression of seat covers like leather or fabric) as well as thermal seat depth information (e.g. influenced by seat structure, foams or other seat substructures) need to be acquired and processed to derive an objective rating value or design improvements. The present invention introduces a new device and a new method to objectively determine thermal heat comfort of seats by means of a set of individually controlled air-flow Peltier elements combined with individually controlled fans and at least one thermal camera to obtain the 2D temperature distribution over time. State of the Art A plurality of methods and devices to provide thermal seat control is known to the state of the art, e.g. (JP2018193057A - Temperature Control Seat Device; JP2020199920A - Seat Control Device and Seat Control Method; WO2022039866A1 - Method and System Using Machine Learning Algorithm for Controlling Thermal Comfort). These methods use heating elements to set an appropriate seat surface temperature but are not able to specify heat or cold at a defined depth of the seat substructure. US10372990B2 - System and method for identification of personal thermal comfort presents a technical system that includes passenger actions to derive the level of thermal comfort (i.e. whether each individual appears to be feeling too hot, appears to be feeling too cold or appears to be feeling satisfied with an ambient temperature). 21 08 24 Similar to matrix-type seat pressure mats also seat temperature mats are known and in use (e.g. https: / / www.thermaltech.at / seat-sensing / ; US2009008377A1 - Occupant sensing heat mat). Here, the passenger's thermal impact onto the seat is measured by means of a matrix of thermal sensors. Furthermore, KR201900835g9A - System and Method for Evaluating Thermal Comfort of Seat presents a method for estimating temperature values of a seat when a user takes a seat and a predetermined time has elapsed by using a regression equation. CN106198069A - Heat comfortableness testing apparatus for office chairs discloses a heat comfortableness testing apparatus comprising a metal buttock model and a steam generator. By means of the buttock model to simulate the buttock of a person, it is possible to know about the shape, the surface temperature as well as the weight of the person. US2022176855A1 - Air Conditioning Device for an Air Flow presents an air conditioning device for a vehicle seat, comprising a flow generator to generate an air flow and air inlet opening fluidically connected to a flow inlet of the flow generator to draw in air to be temperature-controlled. Furthermore, JP2022094185A - Seat Heater Control Device describes a system that determines whether an occupant sits on the seat based on the information on the thermal image and stops energization to the seat heater when the occupant does not sit on the seat. In contrast to the state of the art, the present invention uses air-permeable heating / cooling elements 4 (Peltier-elements) that are individually controlled to provide the required temperature profiles over time for the thermal comfort testing. Every heating / cooling element 4 is attached to an individually controlled fan 5 that allows for a well-defined air-flow 9 and convective heat conduction over time for the thermal comfort testing. Data acquisition is provided with at least one thermal camera 10 observing the seat 2 or back 3 surface over time. Description of the Invention The present invention comprises a device to objectively determine thermal seat parameters such as thermal inertia and thermal capacity of a seat at different positions over the seat 2 and back 3 surface but also in different depths of the seat structure. A predefined temperature (lower or higher than ambient temperature) is applied in a predefined depth of the seat surface 2 or the back surface 3. Therefore, heating / cooling elements 4 and fan elements 5 are combined to thermal conditioning units. The heating / cooling elements 4 are Peltier-type devices that have air tunnels 4a allowing for air flow 9 through the heating / cooling element 4. The fan elements 5 are positioned on top of the heating / cooling elements 4 in a way, that the diameter of the fan elements 5 covers the major part of the heating / cooling element 4 and provides air flow 9 through the air tunnels 4a of the heating / cooling elements 4. At least one of these thermal conditioning units is required to introduce a temperature at a certain point of the seat or back structure. For introducing the temperature at a predefined position, both the 2 21 08 24 heating / cooling elements 4 as well as the fan elements 5 are controlled via a control unit 12. This control unit 12 is connected to a state of the art human machine interface (e.g. personal computer) and provides the control signal for the Peltier elements of the heating / cooling elements 4 to warm up or cool down to the predefined temperature and also provides the control signal for the fan elements 5 to generate the predefined air flow 9 through the air tunnels 4a. The control signal (e.g. voltage or current to operate heating / cooling elements 4 or fan elements 5) are recorded with state of the art data acquisition systems and a storage device (e.g. the personal computer), both implemented in an evaluation and output unit 15. For introducing the desired temperature at the predefined position of the seat 2 or back 3, the thermal conditioning unit or units are placed on the seat 2 or back 3 surface and are fixed. The control unit 12 provides control signals, where: ■ for an intended temperature introduction close to the surface at the seat 2 or back 3, the fan element 5 is set to low velocity, resulting in a low air flow 9 through the air tunnels 4a ■ for an intended temperature introduction further inside the seat 2 or back 3 (i.e. further away from the surface), the fan element 5 is set to high velocity, resulting in a high air flow 9 through the air tunnels 4a and a high temperature transport into deeper sections of the seat structure ■ for intended high temperature introduction, the heating / cooling elements 4 are set to a high temperature value, generating high heat ■ for intended low temperature introduction, the heating / cooling elements 4 are set to a low temperature value, generating either low heat or cooling ■ for any combination of depth and temperature for a given surface position the control signal is set according to the logic presented above The control signals provided by the control unit 12 can be derived from state of the art methods such as look-up-tables, diagrams and lists, machine learning models, etc. When more than one thermal conditioning unit is used to introduce several temperatures at the same time, thermal conditioning units can be connected to a matrix-like structure via connectors or linking elements 7 (e.g. tension straps mounted on the mounting brackets 13) to be placed on the seat 2 or back 3 surface. Linking elements can be e.g. tension straps or mechanical spring devices that allows for the mounting of the thermal conditioning units in pre-defined distances between each other and for mounting options onto the seat 2 or back 3 surface. To fix the thermal conditioning units on the seat 2 or back 3 surface, fixation straps 8 can be used as well as suitable mechanical spring devices. The thermal conditioning units are operated on the seat 2 or back 3 surface according to the control unit 12 signals for a predefined time to ensure stable and fully developed insertion of heat or cooling at the desired position at or inside the seat 2 or back 3. A thermal camera 10 mounted on a stationary or movable frame, tripod or mounting 11 is facing the seat 2 or back 3 surface and determines the temperature distribution over time after all thermal conditioning units are removed from the seat 2 or back 3. Therefore, the temporal 2D temperature 21 08 24 values from the thermal camera 10 are processed in the evaluation and output unit 15. According to the laws of physics or other state of the art evaluation methods such as machine learning, thermal seat parameters such as thermal inertia or thermal capacity as well as porosity properties of the material are evaluated based on the known values of temperature and fan speed from the control unit 12. Porosity information is derived from a procedure, where the thermal conditioning unit is positioned at a flat angle to the surface rather than perpendicularly. The thermal conditioning unit is then heated or cooled while the fan 5 is operated at maximum speed. The length of thermal spreading in the image of the thermal camera 10 is evaluated in the evaluation and output unit 15. A wide length of thermal spreading from the source (thermal conditioning unit) corresponds to high porosity while a short length corresponds to low porosity. For a fast and reliable operation and application of one single thermal conditioning unit at the surface of the seat 2 or back 3, a robot arm 14 can be beneficially used. The thermal conditioning unit can be positioned at any arbitrary spot of the seat 2 or back 3 surface, perpendicular to the seat 2 or back 3 surface by means of a robot arm 14 or any other automated positioning device. It is relevant that the force with which the thermal conditioning unit is pressed against the seat 2 or back 3 surface is used to control the robot arm 14 movement. A constant contact pressure between thermal conditioning unit and seat 2 or back 3 surface is needed for reliable heat transfer. The device hence also comprises a force sensor at the robot arm 14 tool tip. Any state of the art 'revolver'-type selectable tool tip can also be used for operation. All sorts of seats can be tested, especially automotive, rail and aerospace seats, office seats, wheelchairs, sofa furniture as well as cinema or theatre seats. The present invention also comprises a method to objectively determine thermal seat parameters such as thermal inertia and thermal capacity of a seat at different positions over the seat 2 and back 3 surface but also in different depths of the seat structure. Additionally, porosity information can be derived from the applied method of the present invention. For higher repeatability, the entire seat or seat 2 and back 3 elements can be mounted on a rigid frame 7. In a first step, the settings for the control unit 12 are defined. According to the seat type, surface structure, and seat 2 or back 3 structure, predefined time characteristics for the control signals for heating / cooling elements 4 and fan elements 5 are selected. State of the art machine learning methods (e.g. image recognition) can be used for this step as well as manual selection of different classes of seats. In a second step, the thermal conditioning units are positioned according to the measurement specifications. At least one thermal conditioning unit is either placed and fixed on the surface manually by an operator or pressed against predefined positions of the seat 2 or back 3 surface by means of a robot arm 14 or any other automated positioning device. The constant pressure between surface and thermal conditioning device is achieved by force control. For thermal measurements the thermal 21 08 24 conditioning units are typically placed perpendicular to the surface while for porosity measurements the thermal conditioning units are typically positioned in flat angle to the surface. In a third step, the thermal conditioning units are operated, which means that the heating / cooling elements 4 as well as the fan elements 5 are operated according to the control signals of the control unit 12. With a predefined air flow 9 and a predefined temperature, the thermal conditioning units provide temperature introduction into seat 2 or back 3 until the temperature introduction is stable and the intended spot is sufficiently heated or cooled. Control data is sent to the evaluation and output unit 15 for further processing. In a fourth step, the thermal conditioning units are removed from the seat 2 or back 3 surface and are no longer in the range of the thermal camera 10. In case of robot arm 14 operation, the robot arm 14 tip and the hence the thermal conditioning unit is removed from the field of view of thermal camera 10. In a fifth step, the heat distribution of the seat 2 or back 3 is determined by means of the thermal camera 10, that acquires a time sequence of thermal 2D images of the surface. Temperature distribution data is sent to the evaluation and output unit 15 for further processing. The steps 2 to 5 are repeated for all required surface positions at the seat 2 or back 3. In a sixth step, the parameters of interest (especially thermal inertia and thermal capacity as well as porosity of the seat at different positions) are evaluated in the evaluation and output unit 15 according to the laws of physics and well-known mathematical inverse problems or other state of the art evaluation methods such as machine learning and based on the known values of temperature and fan speed from the control unit 12. In a seventh step, the parameters of interest are output and stored in data-readable form in the evaluation and output unit 15. For better understanding of the invention, figures are provided. These figures show in: Fig. 1: a thermal conditioning unit consisting of the heating / cooling element 4 with air tunnels 4a to allow for controlled air flow 9 through the heating cooling elements 4 into the seat 2 or back 3 Fig. 2: top view of a specific embodiment of a thermal conditioning unit with mounting brackets 13 to link several thermal condition units with linking elements 7 together to form a larger array with adjustable distance between the thermal conditioning units Fig 3: a set of thermal conditioning units placed or mounted on the seat 2 surface and the temperature distribution 6a and 6b. The top figure shows inactive heating / cooling elements 4 and inactive fans 5. The figure in the middle shows the temperature distribution 6a when the heating / cooling elements 4 are controlled with constant temperature and the fans are controlled at lower air flow 9. The bottom figure shows the temperature distribution 6b when the heating / cooling elements 4 are at the same constant temperature as in the middle figure but when the fans are controlled at high air flow 9. Fig. 4: an exemplary embodiment of the invention where one thermal conditioning unit consisting of heating / cooling element 4 and fan element 5 is positioned at the seat 2 and one at the back 3 surfaces. Fig. 4 also shows an exemplary array of thermal conditioning units positioned on the seat 2 surface. Fig. 5: an exemplary embodiment of the invention where the thermal conditioning units are fixed with fixation straps 8. Fig. 5 also shows the exemplary embodiment of the invention with thermal camera 10, control unit 12 and evaluation and output unit 15. Fig. 6: an exemplary embodiment of the invention where the thermal conditioning units are positioned by means of a robot arm 14, which holds one thermal conditioning unit and presses this unit against the seat 2 or back 3 surface with predefined force Fig. 7: a flow diagram of the method with the seven major steps 21 08 24

Claims

21 08 241. A device for objective determination of thermal seat comfort comprisingat least one thermal conditioning unit consisting of a Peltier-type heating / cooling element 4 with air tunnels 4a that allow air flow 9 through the heating / cooling element 4 and a fan element 5 mounted on top of the heating / cooling element so that the diameter of the fan elements 5 covers the major part of the heating / cooling element 4 and provides air flow 9 through the air tunnels 4a of the heating / cooling elements 4,an evaluation and output unit 15 that determines, evaluates and outputs parameter of interest such as thermal inertia, thermal capacity and porosity of the seat material by means of state of the art laws of physics or state of the art machine learning models,a control unit 12 that provides control signals to operate the heating / cooling elements 4 and the fan elements 5 to introduce a predefined temperature at a predefined position of the seat 2 or back 3 and that sends control data to the evaluation and output unit 15,a thermal camera 10 mounted on a stationary or dynamic frame 11 that faces the surface of the seat 2 or back 3 and determines 2D thermal images of the surface and sends the temperature distribution data to the evaluation and output unit 15.

2. A device according to claim 1 where a robot arm 14 is used to position one thermal conditioning unit at a predefined position of the seat 2 or back 3 surface with predefined contact force between thermal conditioning unit and surface.

3. A method for objective determination of thermal seat comfort comprising in a first step the definition of the settings for the control unit 12, in a second step the positioning of at least one thermal conditioning unit on the surface of the seat 2 or back 3 and the positioning of a thermal camera 10 to observe the seat surface, in a third step the operation of the thermal conditioning units with predefined control signals for temperature and fan speed,in a fourth step the removal of the thermal conditioning units out of the sensing range of the thermal camera 10,in a fifth step the heat distribution measurement by means of the thermal camera 10 and the transmission of temporal 2D temperature data from the thermal camera 10 to the evaluation and output unit 15, the repeating of step 2 to step 5 for all intended positions of the thermal conditioning units, in a sixth step the evaluation of thermal inertia, thermal capacity and porosity in the evaluation and output unit 15, andin a seventh step the parameter output and parameter and the provision of parameters in machine-readable form for further processing.

Images