Creep and Hysteresis Compensation in Pressure-Sensitive Mats for Improving Center-of-Pressure Measurements

Abstract

Large area tactile sensors are used to image the pressure exerted by human body parts. More specifically, they can be used to measure plantar pressure on human stability tests. The Center of Pressure trajectory is the primary outcome of such tests. Previous research has shown that the parameters obtained from the trajectory correlate with those obtained from a reference instrument, i.e. a force platform. However, there are still noticeable differences. In this work, a low cost prototype of a pressure sensitive mat has been built and compared with a force platform in stability tests. The sensitive material is Velostat, which is readily available. Such a mat could make objective stability tests more accessible. A model of two non-linear effects, hysteresis and creep, has been considered to compensate for them. Given that it was rather difficult to characterize the large mat with a pneumatic device, a small-sized sensor array was first characterized in a controlled environment. Then the model was extended to the large mat using a suitable scaling factor. The experimental results show that compensating for the non-linear effects led to a decrease in the differences between the two instruments, the force platform and the mat, with an average improvement of 26% in the distance between the trajectories.