Ultrasonic sensing system with thermophone and its applications

Abstract

In recent decades, thermophone has been studied as a novel electro-acoustic transducer since it has notable features, such as thin, light weight, acoustic purity, and wide frequency range. Though power consumption and resulting temperature rise are considered fatal problem, they are drastically reduced by limiting operation within ultrasonic domain and adopting the pulse current drive. Ultrasonic sensing system consists of dedicated thermophone as transmitter and commercially available MEMS microphone as receiver is presented to demonstrate typical airborne ultrasonic application, such as range finder or obstacle detection. Applying pulse compression technique, few orders of improvement in distance resolution and effective noise rejection have been achieved. Details of the sensing system and applications cases as listed below will be disclosed. 1. Multiple miniature autonomous vehicles equipped the obstacle sensing system in order to verify the bats jamming avoidance behavior. 2. Bio-inspired active sonar system onboarded to the drone and demonstrated the obstacle avoidance navigation in a wild environment. 3. Small step identification with the obstacle sensing system for electric wheelchair and automatic guided vehicle (AGV). 4. Ultrasonic micro-meter level displacement measurement system for non-contact cardiac pulse monitoring.