1. Technical Field
The invention relates to a method and a device for estimating the temperature sensed upon contact with a surface.
2. Background Art
The measurement and/or estimation of the contact temperature of a surface can be required, for example, in order to be able to make a quantitative estimate of the visible and palpable authenticity and/or genuineness of materials. The so-called heat penetration coefficient can be determined here as a characteristic parameter. Materials with a high heat penetration coefficient (metals, for example) are felt or sensed (by a person touching a surface of the material) to be particularly cold when the temperature of the material is lower than that of the skin of the person touching the material. Materials with a low heat penetration coefficient (insulating materials or wood, for example) are felt/sensed to be warmer when in contact with skin, even if the temperature of the material is actually the same as for a material having a higher heat penetration coefficient. Currently, this heat penetration coefficient is usually only determined on test materials in large scale machines.
In some applications, such as in motor vehicles, however, there is a need to estimate the temperature sensed upon contact with different materials, particularly materials present in the vehicle interior, and/or to estimate the heat penetration coefficient of the materials present in the vehicle interior in a non-destructive, contactless fashion as well as independently of the surface configuration. At the same time, the size of the measuring device used for this purpose should be such that the measuring device can be effectively manipulated in relatively small confines, such as the interior of a motor vehicle, and preferably by an industrial robotic device.
DE 39 01 377 A1 discloses a method for determining thermal conductivity on the basis of measurements of thermoelectric voltage by means of an actuator/sensor system on a material in which a temperature gradient has been produced. In the disclosed method, the required temperature difference is produced by an actuator operated as a Peltier element in a first operating mode. The feeding and discharging of the current-proportional Peltier heat is interrupted briefly and periodically, the actuator operating during these interruptions as a sensor, which detects the instantaneous thermoelectric voltage proportional to the temperature difference, by being switched over electronically to a second operating mode.