In order to endow robots with human-like abilities to characterize and identify objects, they must be provided with tactile sensors and intelligent algorithms to select, control, and interpret data from useful exploratory movements. Humans make informed decisions on the sequence of exploratory movements that would yield the most information for the task, depending on what the object may be and prior knowledge of what to expect from possible exploratory movements. This study is focused on texture discrimination, a subset of a much larger group of exploratory movements and percepts that humans use to discriminate, characterize, and identify objects. Using a testbed equipped with a biologically inspired tactile sensor (the BioTac), we produced sliding movements similar to those that humans make when exploring textures. Measurement of tactile vibrations and reaction forces when exploring textures were used to extract measures of textural properties inspired from psychophysical literature (traction, roughness, and fineness). Different combinations of normal force and velocity were identified to be useful for each of these three properties. A total of 117 textures were explored with these three movements to create a database of prior experience to use for identifying these same textures in future encounters. When exploring a texture, the discrimination algorithm adaptively selects the optimal movement to make and property to measure based on previous experience to differentiate the texture from a set of plausible candidates, a process we call Bayesian exploration. Performance of 99.6% in correctly discriminating pairs of similar textures was found to exceed human capabilities. Absolute classification from the entire set of 117 textures generally required a small number of well-chosen exploratory movements (median = 5) and yielded a 95.4% success rate. The method of Bayesian exploration developed and tested in this paper may generalize well to other cognitive problems.
Keywords: texture discrimination, tactile sensor, vibration, fingerprints, exploratory movements, roughness, classification, Bayesian exploration
Citation: Fishel JA and Loeb GE (2012) Bayesian exploration for intelligent identification of textures. Front. Neurorobot. 6:4. doi: 10.3389/fnbot.2012.00004
Received: 20 March 2012; Paper pending published: 10 April 2012;
Accepted: 23 May 2012; Published online: 18 June 2012.
Edited by:Blythe Towal, California Institute of Technology, USA
Reviewed by:Juan Pablo Carbajal, University of Zürich, Switzerland
Copyright: © 2012 Fishel and Loeb. This is an open-access article distributed under the terms of the Creative Commons Attribution Non Commercial License, which permits non-commercial use, distribution, and reproduction in other forums, provided the original authors and source are credited.
*Correspondence: Jeremy A. Fishel, Department of Biomedical Engineering, University of Southern California, 1042 Downey Way, Denny Research Center (DRB 140), Los Angeles, CA 90089-1111, USA. e-mail: firstname.lastname@example.org