Inspection of the Integrity of a Multi-Bolt Robotic Arm Using a Scanning Laser Vibrometer and Implementing the Surface Response to Excitation Method (SuRE)

Hadi Fekrmandi,Bulent Kaya,Sezai Taskin,Jason Campbell,Javier Rojas,Ibrahim Nur Tansel

doi:10.36001/ijphm.2014.v5i1.2202

Abstract

The integrity of a robotic arm was examined remotely via a scanning laser vibrometer (SLV) in order to detect loose bolts. A piezoelectric element (PZT) was bonded on the robot arm for excitation of surface guided waves. A spectrum analyzer generated surface waves within the 20-100 kHz range. The propagation of the waves was monitored with the SLV at the programmed grid points on the robot arm.The surface response to excitation (SuRE) method was used to calculate the spectrums of the signals, and compare the reference scan with the altered scan. Comparisons of before and after the scan showed that after loosening the bolt on the robot arm, spectrums of all the grid points changed to some extent, however, the largest changes occurred in the vicinity of the loosened bolts.The study shows that the SuRE method was capable of detecting the presence and location of loosening bolts using only one PZT element on a complex structure. There are two most important advantages of the SuRE method over the widely used impedance-based technique. The first advantage is the elimination of an expensive impedance analyzer; the second advantage is remotely monitoring capability as long as the surface is excited properly.

Highlights

Many structural health monitoring (SHM) techniques are developed to improve the reliability and safety of the systems while the maintenance costs and service time are reduced
The tests were performed on a robot arm with a bolted joint that was connected to the main structure via 18 bolts and nuts, out of which 16 were considered for this study (Figure. 5)
High frequency surface waves were employed and the changes in the measured spectrums were used for detection of the single and multi-loose bolts similar to the impedance method

Summary

Introduction

Many structural health monitoring (SHM) techniques are developed to improve the reliability and safety of the systems while the maintenance costs and service time are reduced. Some of these methods are developed for detection of the loose bolts. Bolt joints have been widely used in many civil, mechanical and aero-space structures. Any failure could have catastrophic consequences and manual inspection of the bolts is not feasible. The development of remote monitoring techniques is necessary to address these applications. The integrity of bolted plates of a robot was inspected by implementation of the surface response to the excitation (SuRE) method

Methods

Results

Conclusion