Noncontact Material Identification and Distance Measurement Using Effective Capacitance With CdS Cells
We propose a novel noncontact sensing method for material identification and for detection of the distance between the sensor and the surface of a material by using its electrical and optical properties. In the proposed method, capacitance between the terminals of a pair of CdS cells, called the effective capacitance, is measured, and several capacitance values are obtained by changing the emission strength of the light emitting diode, thus changing the resistance value of the CdS cells. From these values, it is possible to identify the materials and to detect the distance between the CdS cells and the material. In this paper, we compare four kinds of effective capacitance measurement methods using a pair of CdS cells and describe the proposed measurement method. In addition, this paper discusses the measurement accuracy of effective capacitance values in the proposed method and demonstrates its ability to identify six material samples-clear, white, and black acrylic, clear vinyl chloride, brown bakelite, and aluminum-and to detect the distance between the CdS cells and the material.
Surface Type Classification With a Laser Range Finder
This paper presents a system for surface classification using a laser range finder. It is shown that the return intensities and range errors provide sufficient information to distinguish a wide range of surfaces commonly found in a number of environments. A supervised learning scheme (using curves representing the return intensity and range error as a function of angle of incidence) is used to classify the surface type of planar patches. Extensive experimental evidence is presented to demonstrate the potential of the proposed technique. The surface type classification, which uses a typical laser range finder, is targeted for use with autonomous robotic systems in which significantly different interaction is required for each of the various materials present. Results from an on-site experiment demonstrate that the information from the laser range finder is sufficient to identify the different materials (via their surface properties) present in a scene where a bridge structure is being prepared for grit blasting.
Noncontacting microstrip monitor for liquid film thickness
A UHF/microwave technique that measures the wave propagation velocity along a modified microstrip line to determine the thickness of an adjacent film of water (up to about 1 mm) on a metallic surface is described. The technique may be extendable to the measurement of the thickness of coatings on both metallic and nonmetallic surfaces.