Torsional Negative Stiffness Mechanism for Bidirectional Morphing Aircraft Actuation

Description

Traditional morphing concepts require external energy input to achieve the
desired changes to the shape of aircraft structures, often working against the inherent stiffness of these structures. This can lead to a requirement for large actuators, and a significant negative impact on system level performance due to the added mass and energy requirements. This work investigates an energy efficient concept for bidirectional morphing aircraft actuation by using a negative stiffness mechanism. The negative stiffness mechanism reduces the actuation requirements for morphing structures by strategically locating negative stiffness devices in parallel to the positive stiffness of the morphing structure to create a net zero stiffness system and therefore to tailor the required deployment forces and moments with minimal energy requirements.
The torsional negative stiffness with an off centre spring (TNSOCS) mechanism
proposed here uses a pre-tensioned spring to convert the decreasing spring force available in the spring into increasing output balanced torque. The kinematics of the negative stiffness mechanism is first developed to achieve bidirectional actuation and its geometry is then optimised by employing an energy conversion efficiency function. The performance of the optimised negative stiffness mechanism is evaluated through net torque, the total required energy and energy conversion efficiency. Exploiting the negative stiffness mechanism has a significant benefit not only in the field of morphing
aircraft but many other energy sensitive applications.

Period	9 Oct 2018
Event title	6th Aircraft Structural Design Conference
Event type	Conference
Conference number	6
Location	Bristol, United Kingdom
Degree of Recognition	National