Measurements of the Airflow Velocity Using Ultrasonic Transducers

Abstract

Operation with control systems of moving objects requires taking into account the longitudinal and transverse components of the air flow velocity. For this purpose, the air flow velocity meters utilizing the acoustic method are used. These meters have a short response and no mechanically moving elements. However, their large size and the presence of construction units subjected to considerable deformation under the mechanical impact make it difficult to implement these meters as parts of moving objects. In this work, the operation algorithm of a device measuring the airflow velocity using the ultrasonic transducers is analyzed. We show that the reduction in the size of such devices leads to a decrease in the measurement accuracy without the improvement of the methods for determining the propagation time of an ultrasonic pulse between transducers and without periodic calibration of the device. The block diagram is developed and the main elements are considered for the computing device, which makes it possible to determine the longitudinal and transverse components of the airflow velocity using four ultrasonic transducers. The laboratory tests in an air tunnel with a distance between sensors of 60 mm showed that this device makes it possible to determine the airflow velocity with the maximum absolute measurement error of 2.5 m/s. This error is considerably affected by the structural elements of the device that obscure the measurement area but yield the required strength characteristics. The proposed error compensation algorithm based on the approximation method by trigonometric functions significantly reduces the maximum measurement error to 1.2 m/s. Further improvement of the device’s characteristics requires additional studies to find the shape of the sensor block and refinement of the error compensation algorithms.