Modeling the Pilot Detection of Time-Varying Aircraft Dynamics

Abstract

T HE human pilot is typically required to control aircraft in which the dynamics of the vehicle vary with time. This variation may occur naturally as the aircraft changes flight condition, it can be deliberately induced by changes in the stability and command augmentation system (SCAS), or it may result from airframe damage or control system failures. The means by which the pilot is able to accommodate these changes has led to studies describing the “adaptive human pilot,” (e.g., [1–3]). The work in [4] used a simplified pursuit-control model of the human operator derived from the more complete structural pilot model of [5]. The simplification in [4] allowed implementation of an adaptive control structure in computer simulation of control tasks with time-varying controlledelement dynamics as reported in [6]. It is desirable to hypothesize the manner in which the more complete structural model might be employed to explain human pilot detection of time-varying vehicle dynamics. The structural pilot model is shown in Fig. 1 in a form suitable for a simple single-axis task, such as an aircraft/rotorcraft pitch-attitude tracking task. The pilot model includes three feedback loops defined as visual, vestibular, and proprioceptive. For the purposes of this initial discussion, the vestibular loop will be ignored (K _ m 0). A detailed description of each of the elements in the model is given in [5]. Here, with the exception of the element YPF, the elements will only be briefly described. In themajority of applications, the element Ye is a simple gain. The time delay 0 is set to 0.2 s. YNM is a simple second-order transfer function representing the neuromuscular dynamics in the particular limb that is driving the cockpit inceptor (e.g., control stick or rudder pedals). The element YFS represents the cockpit inceptor force/feel system dynamics. Yc represents the vehicle dynamics in the control axis in question (i.e., the transfer function between vehicle pitch attitude and longitudinal control inceptor input ). The proprioceptive feedback element YPF is assumed to be of the form such that