Simulations of an Optical Tactile Sensor Based on Computer Tomography

Abstract

In order to create a robotic tactile sensor of thin shape, a new optical tactile sensor is developed by applying a CT (Computer Tomography) algorithm. The present tactile sensor is comprised of infrared emitting diode arrays, receiving phototransistor arrays and a transparent acrylic plate and a black rubber sheet with projections. Infrared rays emitted from the diode array are directed into one end of the plate and their intensity distribution is measured by the phototransistor array mounted on the other end. If the CT algorithm is directly applied to the tactile sensor, there are two shortcomings: the shape of the sensing area is limited to a circular region and there is a long calculation time. Thus, a new CT algorithm oriented to tactile sensing is proposed for overcoming these problems. In the present algorithm, a square sensing area is divided into an N-by-N array and algebraic equations are derived from the relationship between the input and output light intensities on the assumed light projections. Several reconstruction methods are considered for obtaining pressure values caused in the squares. In the present study, the ART (Algebraic Reconstruction Technique) and LU decomposition methods were employed, and these methods were compared to select the best reconstruction method. In a series of simulations, it was found that the LU decomposition method held an advantage for the present type of tactile sensor because of its robustness against disturbance and short calculation time.

Sensing Characteristics of an Experimental CT Tactile Sensor

“…Therefore, we apply the CT technique to inverse-identification of pressure distribution based on the information from around a tactile sensor. In a previous paper, (11) we established the architecture of the CT tactile sensor and surveyed tactile sensors based on a reconstruction algorithm (12) (13) to develop a new architecture for a tactile sensor. After we designed the CT tactile sensor, we evaluated two reconstruction algorithms suited for it: one is the Algebraic Reconstruction Technique (ART) based on iteration; the other is the numerical solution method for linear algebraic equations (hereafter called LUD because LU decomposition is adopted as the numerical linear algebraic solution).…”