Remote Absolute Roll-Angle Measurement in Range of 180°Based on Polarization Modulation

Remote measurement of object orientation is often required in many applications.Out of the six degrees of freedom(DoF)that determine object orientation in space,the roll angle is the most difficult to measure using optical methods.In this letter,we propose a remote Stokes roll-angle sensor that measures roll angles from the detected Stokes vectors of modulated polarized light retroreflected from a sensing unit comprised simply of a retarder and a planar reflection mirror.Experimental results have shown that the proposed sensor can realize absolute roll angle measurement in an unprecedented range of 180°with a maximum absolute error of less than 0.25°and a measurement resolution of better than 0.01°.The proposed sensor adopts a coaxial design and takes the advantages of compactness,simplicity and low cost,and moreover,can be further expanded to a three-DoF angle sensor due to the sensitivity of the sensing unit to other two kinds of angles(pitch and yaw).

A comprehensive survey on the methods of angle of attack measurement and estimation in UAVs

Angle of Attack(AOA) is a crucial parameter which directly affects the aerodynamic forces of an aircraft.The measurement of AOA is required to ensure a safe flight within its designed flight envelop.This paper intends to summarise a comprehensive survey on the measurement techniques and estimation methods for AOA, specifically in Unmanned Aerial Vehicle(UAV) applications.In the case of UAVs, weight constraint plays a major role as far as sensor suites are concerned.This results in selecting a suitable estimation method to extract AOA using the available data from the autopilot.The most feasible and widely employed AOA measurement technique is by using the Multi-Hole Probes(MHPs).The MHP measures the AOA regarding the pressure variations between the ports.Due to the importance of MHP in AOA measurement, the calibration methods for the MHP are also included in this paper.This paper discusses the AOA measurement using virtual AOA sensors, their importance and the operation.

Numerical and experimental investigation to design a novel morphing airfoil for performance optimization

Optimizing flying objects’wing performance has attracted a significant attention in the last few decades.In this article,some of the main mechanisms for changing the geometry of the wing were investigated and a new mechanism is proposed to improve the aerodynamic performance of the airplane wing.The designs have been simulated and analyzed from both aerodynamic and control points of view.In aerodynamic simulations using CFD methods,two airfoils of NACA series 6 with specifications 65-212 and 65-2012 were modeled.The results indicated that both airfoils used have a better performance compared to others in a certain range of the angle of attack.Subsequently,a new mechanism is proposed to change the wing geometry to optimize its structure.In the proposed mechanism,the structures of airfoils and wings consist of two fixed and moving parts,which can change their geometry with the help of a control circuit.The fixed part has a grooved track,and as the moving part moves in the direction of the grooves,the curvature of the upper and lower parts of the wing changes.The design control circuit includes an angle sensor,a micro controller,and a servomotor.The CFD results are entered into the micro controller as code.At any moment,the micro controller receives the angle data from the angle sensor and by comparing them with the CFD data,and issuing a command to the servomotor,it situates the wing curvature in the optimal state at all times.The built mechanism was tested at an attack angle of 0°and 25°.The results showed that the different parts of the mechanism work with very high precision and put the geometric shape of the wing in an optimal state in a completely intelligent way.It should be noted that the average error in test for t/c and Xt/c was 15.3% and 9%,respectively.