Motion Cues

The pilot in the actual flight of the aircraft experiences the natural motion cues; this is more so in the case of a fighter aircraft. Some motion (cues) aid the pilot in stabilizing and maneuvering the aircraft by confirming that the pilot’s internal model response and the aircraft responses match very well. Some other motions of the aircraft alert the pilot to ensuing system failures [1]. In a fixed-base flight simulator motion cues are absent and the only cue is via the visual cues from the instruments and the simulated view of the outside world. These visual cues of motion are very important low-frequency cues. The vestibular system of the human is a sensor of motion and position. The semicircular canals in the inner ears are the rotational and motion sensors. They act as damped angular accelerometers. Three such canals form an almost orthogonal axes system in each ear and sense angular accelerations as low as 0.1 °/s2. The linear motion is sensed by the otoliths of the inner ears. They sense specific forces, the external or nongravity force, with the threshold as low as 0.02 m/s2 and can detect a tilt of 2°. A system approach to human perception of orientation and motion has been developed. The vestibular sensors are modeled as mechanical systems. The parameters of these models have been validated by several experiments of human perception IFSs. The semicircular canal model is given as [1]:

Afferent firing rate (°/s2) 0.07s3(s + 50)

Physical stimuli (°/s2) (s + 0.05) (s + 0.03)

The velocity threshold for this model is 2.5°/s. The otolith TF is given as

yoto _ 2.02(s + 0.1)

f _ (s + 0.2)

The velocity threshold for this model is 0.2 m/s. There are other physiologically based cues like the visual, proprioceptive, and tactile cues. In general the proprio­ceptive sensors are associated with the vestibular system, the joints, muscles, and the internal organs of the human body. Very interestingly the processing of the sensor signals by the central nervous system can be effectively modeled by a steady-state KF. The spectrum of sensing spans a lower frequency (visual) to higher band due to proprioceptive and other cues, thus the earliest recognition of the motion is possible and hence the usefulness and importance of motion cues/sensing in flight-training simulators. The motion system’s bandwidth should be at least slightly greater than the simulated aircraft’s rigid body dynamics. Also, various tasks which need to excite the motion cues (sensors) should be such that they fall within the bandwidth of 0.1—1.5 Hz, the body sensors’ active sensitive region. In general elaborate visual cues are effective for many piloting tasks IFSs; however, human eyes are slow in perceiving motion. Before any visual cue sensing takes place the human brain receives the acceleration cues. Many body sensors detect the acceleration and the signals are communicated to the brain in milliseconds. If the motion cues are needed then, the motion system should be systematically designed and integrated. This will enhance the quality and utility of motion cues.