Online Profiling of Nonplanar Objects by High-Resolution Air-Coupled Ultrasonic Distance Measurements

Ultrasonic measurements are used in product sizing in various industrial technologies. The advantage of such techniques is that measurements can be performed contactless on a conveyer using an air-coupled ultrasonic method. Nevertheless, implementation of such systems is complicated due to temperature variations, a nonconstant movement velocity, and geometry of the object necessary to measure. In this paper, an ultrasonic technique for the measurement of geometric parameters of objects transported by a conveyer is presented. Operation of the system is based on precise measurements of the distance between the transducer and the surface of an object. The measurement technique includes such stages as detection of the object, recognition of a typical profile, using a feature extraction algorithm, and measurement of object dimensions at selected positions. As an example of implementation of such a measurement technique, the ultrasonic air-coupled system for the measurement of the thickness of chocolate during the production process is presented.