Assisted Neck Movement under High G+ Situations

The objective of this research is to investigate smart actuator technology for an adaptive neck brace to assist pilots during high g+ maneuvers. Analysis and experiments were conducted to develop a simplified analytical model of the neck, determine the effectiveness of using a brace to prevent neck injury under high acceleration loads, identify actuator technology capable of actuating the mechanism effectively and efficiently, and to experimentally validate the chosen mechanism and actuator. The experiment successfully demonstrated that an adaptive neck brace can successfully reduce the displacement experienced by acceleration forces. The physical model utilized a scissor mechanism brace configuration using shape memory alloy (SMA) wire for actuation. The presence of the brace avoided high resonant peaks and introduced damping to the original model. Introduction and Background The existence of neck injury for fighter pilots has become well documented in the past decade. It is widely accepted that these injuries are primarily a result of the intense acceleration forces experienced by a pilot during a typical sortie. 1-9 Methods of study undergone to quantify sustained G force effects range to include monitoring the electromyography (EMG) of pilots during these extreme conditions, questioning the pilots on perceived discomfort in flight, comparing neck muscle strength between pilots and non-pilots, as well as investigating medical procedures undergone by pilots recovering from G force induced injuries. 1-7,9 Typical injuries resulting from G force induced muscle strain vary from mild sprains to flight career ending debilitations, and have been shown to be experienced by 90% of fighter pilots during their career. 2,4 Research has concluded that these injuries are more likely to occur when the head is away from the neutral position (the head rested squarely on the shoulders looking forward), as this greatly increases the loads directly supported by the neck. 2,4,5,6,8 This danger drastically increases once the neck rotates past a 35 degree angle. 2 At such angles muscle activation has been measured as high as 257% maximum voluntary isometric contraction. 6 One study found the pilots head to be away from the neutral position 68% of the time during air combat, quantifying the large amount of time fighter pilots endure these dangerous neck loading conditions. 4 As a result of fatigue, fighter pilots will often unload imposed G forces before rotating their neck, often compromising the effectiveness with which they can achieve their mission or carry out evasive maneuvering. 1,2 As fighter aircraft becomes increasingly maneuverable and technology continues to add to the weight of the pilot’s helmet (i.e. Head-Mounted displays), the problem of cervical spine injury promises to become more prevalent. 2,5,6 Despite the vast amount of research dedicated to studying the affect of G forces on pilots, little work has been done to identify preventative devices and mobility aides to assist pilots under these extreme conditions. Most of the methods studied to combat injury involve undergoing workout regimes to increase the strength and flexibility of the muscles supporting the neck. 2,4,7 One study attempted to quantify the benefits of using a lumbar support around the lower back. The results revealed a slight benefit in comfort for some pilots while causing discomfort for others. For the pilots that experienced increased comfort, improvement in EMG readings proved too small to be considered statistically relevant. 9