Mechanism and experiments of asymmetrical pitch system for MAV
In view of problem for miniaturizing Micro Air Vehicles (MAV), a novel asymmetrical pitch system faced to rotary wing MAV is introduced. The pitch mechanism and control characteristics are studied and analyzed. Because the deformation of elasticity link is key to generate the blade pitch, it is analyzed and calculated by elasticity finite element method. And the results illustrate the linear relationship between blade pitch angles and the output torque of the motor. Based on control system of asymmetrical pitch, mechanism experiments based on strain gauge are done, and the factors that affect the deformation of the elastic linkage is analyzed. Results indicate that mechanism of asymmetrical pitch is effective.
A novel asymmetrical pitch system for a rotor micro air vehicle
Concerning to problems of the traditional machine pitch system for miniaturizing Micro Air Vehicles (MAVs), A novel asymmetrical pitch method is put forward in this paper. This novel method makes use of the deformation of an elasticity link to generate the blade pitch meeting the requirement of the MAV flight mode control. This new pitch mechanism has been verified by means of two experiments. One experiment measures blade pitch angle by a non-contact measurement using the high speed camera and image processing and the other experiment measures deformation of the elasticity link which is key part in asymmetrical pitch system based on strain gauge and rotating electrical connector. From relationship between blade pitch angles and the output torque of the main motor and deformation curves of the elasticity link, the pitch mechanism that the deformation will periodically change once with the rotor blade rounding a lap is proved.
Evaluation of buckling load and dynamic performance of steel shear wall retrofitted with strips made of shape memory alloy
One of the most imperfections of the steel shear wall is out of plane displacements that cause severe damage in both structural and non-structural elements. In this paper, the effects of shape-memory alloys on steel shear walls are investigated. First, a numerical analysis using the finite element method in ABAQUS software has been carried out according to an experimental test. The results of the numerical analysis have been verified with experimental results. Next, shape-memory alloy fibers have been added vertically and horizontally to various parts of the steel shear wall. The results show that retrofitting with the shape-memory alloy reduces the out-of-plane displacement of the steel shear wall under both cyclic and seismic loadings. Besides, the buckling load in the steel shear wall increases when it is retrofitted with the shape-memory alloy. Also, the total out-of-plane movement (accumulated absolute displacements) of the steel shear wall and non-structural damage are controlled by the characteristic of a shape-memory alloy material called “super-elastic”.