Abstract
This paper details an investigation of shape memory alloy (SMA) filaments which are used to drive a flight control system with precision control in a real flight environment. An antagonistic SMA actuator was developed with an integrated demodulator circuit from a JR NES 911 subscale UAV actuator. Most SMA actuator studies concentrate on modeling the open-loop characteristics of such a system with full actuator performance modeling. This paper is a bit different in that it is very practically oriented and centered on development of a flight-capable system which solves the most tricky, practical problems associated with using SMA filaments for aircraft flight control. By using well-tuned feedback loops, it is shown that intermediate SMA performance prediction is not appropriate for flight control system (FCS) design. Rather, capturing the peak behavior is far more important, along with appropriate feedback loop design. To prove the system, an SMA actuator was designed and installed in the fuselage of a 2 m uninhabited aerial vehicle (UAV) and used to control the rudder through slips and coordinated turns. The actuator was capable of 20 degrees of positive and negative deflection and was capable of 7.5 in-oz (5.29 N cm) of torque at a bandwidth of 2.8 Hz.
Highlights
IntroductionIrreversible aircraft flight control is typically achieved by using some form of conventional hydraulic or electromechanical servoactuators
Because the cost of the shape memory alloy (SMA) filaments with respect to electromechanical actuator cores is competitive, there exists a window of opportunity to demonstrate a highly useful form of flight control with SMA filaments, this study will examine its utility as an actuator replacing a single servoactuator on a 2 m sized uninhabited aerial vehicle (UAV)
The UAV would remain in the traffic pattern and test the SMA actuator during a series of maneuvers performed on each pass along the flight field
Summary
Irreversible aircraft flight control is typically achieved by using some form of conventional hydraulic or electromechanical servoactuators These types of actuators are often quite large, heavy, and use numerous moving parts. The earliest inklings of flight control via adaptive aerostructures were seen in the 1980s with experiments on various kinds of twisting and bending plates [1,2,3] These early experiments were followed by a slew of innovations directed towards control of rotorcraft via actively twisting structures, flaps, and pitch activation mechanisms [4]. These adaptive rotors were morphed into the DoD’s first successful Micro Aerial Vehicles with a program starting in 1994 This early effort eventually lead to 6 internal combustion-engine powered, adaptive structures controlled rotorcraft successfully flying off in a DARPA competition at Quantico, VA, in 1990 [11]. Because the cost of the SMA filaments with respect to electromechanical actuator cores is competitive, there exists a window of opportunity to demonstrate a highly useful form of flight control with SMA filaments, this study will examine its utility as an actuator replacing a single servoactuator on a 2 m sized UAV
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