SPIRAL PULLEY NEGATIVE STIFFNESS MECHANISM FOR MORPHING AIRCRAFT ACTUATION

The energy balancing concept seeks to reduce actuation requirements for a morphing structure by strategically locating negative stiffness devices to tailor the required deployment forces and moments. One such device is the spiral pulley negative stiffness mechanism. This uses a cable connected with a pre-tension spring to covert decreasing spring force into increasing balanced torque. The kinematics of the spiral pulley are firstly developed and its geometry is then optimised by employing an energy conversion efficiency function. The performance of the optimised spiral pulley is then evaluated through the net torque, the total required energy and energy conversion efficiency. An experiment demonstrates the negative stiffness property of the mechanism and compares its characteristics with the analytical result. Exploiting the negative stiffness mechanism has a significant interest in not only the field of morphing aircraft but many other power reduction applications an increasing output torque. The kinematics of the spiral pulley are firstly developed and its geometry is then optimised by employing an energy conversion efficiency function. The performance of the optimised spiral pulley is then evaluated through the net torque, the total required energy and energy conversion efficiency. An experiment demonstrates the negative stiffness property of the mechanism and compares its characteristics with the analytical result. Exploiting the negative stiffness mechanism has a significant interest in not only the field of morphing aircraft but also many other energy and power reduction applications.