An ultrasonic MEMS-based airspeed sensor for lightweight drones

Abstract

This thesis is conducted together with the Swedish Sea Rescue Society (SSRS), where an ultrasonic airspeed sensor for lightweight fixed-wing drones is developed. The project acts as an alternative to the currently used sensor on the drone, which is based on a Pitot-static system. The ultrasonic technique has shown significant potential for airspeed measurement. This work further explores the technique with the aim of developing a compact sensor design better suited for small aerial vehicles. To achieve this, ultrasonic Micro Electro Mechanical Systems (MEMS) are utilized. The developed prototype consists of three main parts. First, two transceiver modules which are facing each other at a 45◦ angle relative to the airflow, enabling collection of upwind and downwind data. Second, a microcontroller software that controls the transceivers and produces airspeed estimations. Third, a control circuit which enables communication between microcontroller software and transceiver modules. The core of the airspeed estimation is based on the difference between upwind and downwind data, along with different signal processing techniques. The results demonstrate that the prototype offers advantages in terms of size, weight and power consumption, with the potential to match conventional Pitot-static systems. Furthermore, the developed prototype is able to accurately record airspeed in one direction. It also demonstrates the limitations of this kind of hardware, as well as the ultrasonic airspeed measurement technique in general.