Abstract
Traditionally, people´s requirements for luxury car interior features, particularly of surface materials, have been mainly focused with appearance, for example that instrument panel and door trim look good. Recently, however, there is a growing demand for touch perception quality, for example, for plastic surfaces to be coated with `soft-feel paint´, which gives a softer feel.
When evaluating the touch perception used for interior parts, sensory values, such as dry or moist feel, are used as judgment indices. However, in order to determine the direction of future developments for materials with improved surface touch perception, we also need quantitative judgement indices. This paper discusses the development of evaluation method for quantifying the sensory values of surface touch perception.
The research focuses on `stick-slip´ sensation in order to quantify surface touch perception. The human texture perception mechanism can be described as `stick-slip´, which refers to the sensory perception felt by moving a finger over a material surface. Research conducted at Oxford University shows that the pressure response of the piezoelectric material polyvinylidene difluoride (PVdF) is similar to the output voltage response of skin sensory receptors.
The new evaluation equipment, developed by KANTO AUTO WORKS,LTD, incorporates a sensing device, covered with layers of PVdF, gauze and silicon rubber, with a sensing function that simulates the human fingertip. The material to be tested is mounted on a sliding block, which moves beneath the sensing device, so that the material surface moves in parallel to the sensor at a constant speed and pressure. The friction occurring between the sensing device and the surface material causes a distortion pulse to be transmitted to the PVdF. The piezoelectric character of the PVdF in turn causes a micro voltage output, convertible to a frequency which can be used to confirm the correlation with quantitative value analysis based on human texture perception frequency. As a result, it can express sensory values as quantitative values.
Summary
- The evaluation equipment that can measure surface touch perception has been developed.
- The equipment makes it possible to express sensory values of surface touch perception as quantitative values.
- The equipment will be utilized in the future development of surface materials that have a better touch perception.