This study aims to develop a clinging device for structural inspection robots, which are expected to be used to reduce the cost of inspection of aging civil infrastructure and industrial structures. In a previous study, an electro-permanent magnet (EPM)-based clinging device that could electrically turn on and off the magnetic adhesive force against steel structures was proposed. In this study, a more versatile design of the clinging device was firstly presented, and a considerable difficulty regarding the activation process of the EPM which might impair the reliability of the clinging device was stated based on mathematical modeling and experiments. The concept of a two-step activation process was then presented to overcome the stated difficulty, and its implementation using a limit switch-based contact sensor was successfully demonstrated through collision tests. Furthermore, sensorless realization of contact detection by measuring the induced voltage across the coil of the EPM was proposed, and its feasibility was validated.

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