A New Sensorized Prodder Device for the Detection of Vibrational Characteristics of Buried Objects

A new device is presented for the detection of compliant objects buried in shallow soil by their vibrational characteristics. The device is based on the concept of a sensorized prodder that can measure the acceleration of a point on the surface of the object with a rigid steel rod. This paper presents a simple model able to simulate the acceleration frequency response of the system composed of the prodder and a buried object. Direct laboratory measurements and/or parametric inspection of the mechanical characteristics of the prodder device and the test objects allow us to select a suitable frequency range to detect compliant objects. The developed equivalent lumped circuit model allows investigation of the natural resonant frequency of the designed prodder device and of the test objects at different depths. The object is vibrated applying a contact force generated by an electrodynamic actuator driven with a series of frequency-modulated burst signals. The fully assembled device is light and of compact size, and it has been tested both mounted on a robotic arm and handheld. In good agreement with the simulations, the results of the tests carried out in the laboratory and in an outdoor test bed showed that the responses of the compliant and rigid test objects were well distinguishable in the frequency range from 100 to 1000 Hz.