Piezoelectric MEMS (Microelectromechanical systems) technology is an interesting transducer technology for miniaturised systems using ultrasound. Acoustic technologies have many applications areas and can fulfil several requirements for future smart Internet of Things (IoT)-devices such as: low power requirements, small volume, high performance, ease of manufacture and integration. Human Machine- and Machine to Machine interfaces is for example an application area that is gaining increased interest. Think of touchless activation and control without the need to wear and hold any controllers.
SINTEF has recently developed a tiny piezoelectric micro machined ultrasonic transducer (pMUT) that can be used for sending and receiving ultrasound. To further investigate the performance and possible applications of the pMUT we propose 3 projects:
I. Characterisation of pMUT
A microcontroller-based embedded system with 8 receive (RX) and 8 transmit (TX) channels has been developed by the Norwegian company Embida (now part of Inventas). The TX channel can be connected to a pMUT, and the RX channel is compatible to be used with either Knowles MEMS microphones or the Tx pMUT mounted on the RX PCBs fabricated by Embida. This project will focus on characterization measurements of the pMUT using the Embida system as a starting point. A possible extension can be to explore the use of the Embida system as an ultrasonic array sound card.
II. Controller for transmitting and receiving signals in an ultrasonic array using a wireless SoC
The project will investigate the performance and suitability of a commercially available wireless System on Chip (SoC) device to be used as the main controller for beam steering of an ultrasonic array. The ultrasound transducer (pMUT) can be controlled using a general-purpose digital output running at a high frequency. A Knowles MEMS microphone (available e.g., on the Microbit V2) with band pass filters and a sampling frequency of e.g., 48 kHz can be used as a receiver. Data can be transferred wirelessly to central unit for further processing. It is proposed to use a SoC device from the nRF product line of Nordic Semiconductors. The project will explore and optimise for the number of channels and bandwidth that can be used to control the ultrasonic array. A possible application can be imaging and localisation of humans in a room.
III. Relative positioning network using the Microbit V2
Every node in a network will use a pMUT as a sender together with the Knowles microphone on a Microbit V2 as a receiver. Each node will in turn work as a sender while the others are configured as receivers. This will be controlled by a wireless protocol to be developed as part of the project. Measuring the time delay between all of the devices, the relative position of each node can be calculated as an inverse problem solved by e.g., using Euclidean Distance Matrices (EDMs). A possible application can be a network of sensors used to locate objects as part of a virtual reality system.
The pMUT developed by SINTEF will be central in all projects. All projects will involve programming of embedded systems, signal processing, and measurements and experiments.
The projects will be part of the Gemini center called "New sensors, new images, and new applications" – a collaboration between SINTEF and the University of Oslo focusing on the development and applications of innovative technology based on non-optical imaging with miniaturised sensors. Co-supervison from SINTEF and relevant industrial partners may be considered.