Fine Alignment and Contact Control of a Soft Semispherical Ultrasonic Probe Based on Its Frequency Signature

Abstract

Positioning and force control of an ultrasonic probe with soft contact against an object surface are important manipulation tasks for measurements in manual nondestructive contact ultrasonic testing. The use of a semispherical probe with soft contact allows a controlled increase of the contact force and energy transmission. However, successful application of contact ultrasonic testing depends on the control of the sensor’s pose and applied force at the mechanical contact between the probe and the surface of the inspected object. In this work we study the use of frequency signal information to control the alignment and force of the probe using a robotic arm to perform measurements on a rigid object assuming limited information of the surface orientation. A methodology of signal conditioning using a fast Fourier transform is implemented. The experimental results show that the proposed methodology based on frequency analysis allows a fine tuning of the probe pose with high sensitivity to load and misalignment, improving ultrasonic measurements.