Bolt loosening detection using multi-purpose robot hand

Inspection is an important part of the manufacturing process. One example of the important inspections is bolt loosening detection. Many studies have been carried out on the detection of bolt loosening. However, most of the research required specialized actuators and sensors for estimating the state of bolts. In the manufacturing process, there is a growing demand for general-purpose robots to achieve high-mix low-volume production, and automating inspection processes with general-purpose robots is important. Thus in this research, we tried to automate the bolt loosening detection with general-purpose robots and a simple 6-axis force sensor mounted on the robot. We tried to detect the loosening by vibrating the objects for short seconds and analyzing the force signal. Using the simple feature values, we succeeded in detecting loosening of bolts in three types of objects, one of which includes invisible bolt loosening.