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.
Analysis of rotor manipulation mechanism for unmanned micro helicopters
The small size and low carrying capacity of unmanned micro helicopters requires a rotor manipulation mechanism that makes use of the rotor inertia and material elasticity and meets the requirement of the helicopter flying mode control. The mechanism quickly follows changes of the motor output moment. The equation for the rotor blade lag was derived using the Hamilton principle and solved using the extended Galerkin method. The blade lagging motion for the condition of varying angular velocities was analyzed. The results illustrate how the radius of the rigid center body and the various angular accelerations of the rotor affect the blade displacements and how the initial angular velocity of the rotor affects the blade lag frequency.
Global Occupational Health Issues
1. Occupational health problems in developing countries are more widespread and serious because they occur against a background of endemic risk factors for ill health. 2. In general, developing countries have less adequately developed occupational health personnel and programs and less adequately developed and enforced laws and regulations than developed countries. 3. Awareness of the importance of occupational health among workers, management, government officials, and the public is increasing with developing countries. 4. Occupational health professionals in developed countries can contribute in many ways to improving occupational health in developing countries.