An Ultrasonic Proximity Sensing Skin for Robot Safety Control by Using Piezoelectric Micromachined Ultrasonic Transducers (PMUTs)

The safety issue of robot becomes a key challenge in modern manufacturing industry, especially in the scenario of frequent human-robot collaboration. This paper presents a flexible ultrasonic proximity sensing skin which can be integrated on the surface of robot arm to ensure the safe human-robot collaboration. The sensing skin is composed of three pieces of aluminum nitride based piezoelectric micromachined ultrasonic transducers (PMUTs) arrays at the resonance frequency of 115 kHz and chip size of 4 mm $\times 4$ mm $\times0.5$ mm. The three pieces of PMUTs arrays are evenly integrated on the flexible printed circuit board (FPCB) with a device size of 8.8 mm $\times60$ mm $\times1.7$ mm. The proximity sensing skin can detect obstacles within 300 mm and 60 degrees in front, and shows a large sensing coverage in comparison with capacitive/infrared devices. Besides, it is capable of sensing transparent materials like glass. Finally, since the small size and good scalability of micro-electro-mechanical system (MEMS), the PMUTs are easy to install onto robots and to integrate with other ultrasonic transducers in the future. This PMUTs based sensing skin will greatly enhance the sensing capability of robots and human safety during collaborative work.