Laser Displacement Sensors for Wind Tunnel Model Position Measurements

Abstract

Wind tunnel measurements of two-dimensional wing sections, or airfoils, are the building block of aerodynamic predictions for many aerodynamic applications. In these experiments, the forces and pitching moment on the airfoil are measured as a function of the orientation of the airfoil relative to the incoming airflow. Small changes in this angle (called the angle of attack, or α) can create significant changes in the forces and moments, so accurately measuring the angle of attack is critical in these experiments. This work describes the implementation of laser displacement sensors in a wind tunnel; the sensors measured the distance between the wind tunnel walls and the airfoil, which was then used to calculate the model position. The uncertainty in the measured laser distances, based on the sensor resolution and temperature drift, is comparable to the uncertainty in traditional linear encoder measurements. Distances from multiple sensors showed small, but statistically significant, amounts of model deflection and rotation that would otherwise not have been detected, allowing for an improved angle of attack measurement.

Laser Sensors for Displacement, Distance and Position

“…The papers can be classified based on sensors’ measurement principles: Triangulation sensor [1,2,3,4], time-of-flight sensor [5,6,7], confocal sensor [8], interferometric sensor [9], fiber Bragg grating sensor [10], and laser Doppler velocimetry [11]. There are also three papers [12,13,14], which are not classified in the above categories.…”

“…In [1], angle change of airfoils inside a wind tunnel is measured using four commercial triangulation sensors (Acuity AR700-32). Small changes in this angle (called the angle of attack) can create significant changes in the forces and moments, so accurately measuring the angle of attack is critical.…”

“…The four sensors measure the distance between the wind tunnel walls and the airfoil, which was then used to calculate the model position. The proposed system in [1] is able to detect model deflection and rotation that would otherwise not have been detected by other sensors. Since the measured distance tends to drift slightly with temperature, a temperature compensation algorithm is proposed.…”

Development of mobile robot for measuring distance using optical quadrature encoder

“…A mobile robot needs to be equipped with appropriate and suitable sensors so that a safe and effective path can be found. Kuester [7] are using laser displacement sensor while modelling the wind tunnel position measurement and conclude that the length output from the lasers was found to drift slightly with temperature. Laser displacement sensor has been used in [8][9][10][11] which conclude that the measurement using this method provide more convenient operation and ease to be used.…”

Investigations of dynamic phenomena of precision length measurement system

“…The optical encoder module makes it much easier to control simple control methods such as proportional-integral (PI) or proportional-integral-differential (PID) at low speeds using low-resolution devices [1,7].…”