Design, implementation and preliminary evaluation of displacement and force control sticks on a flight simulator

Abstract

Recent advances in aviation technology have led to fundamental changes in aircraft flight control systems. The increasing popularity of fly-by-wire systems necessitates an investigation into the design of the interface between the pilot and the flight control computers that drive the actuators of the control surfaces. Maintaining the basic cockpit configuration alleviates problems of transition, however, the control input devices should ensure that the benefits of the new system are well utilized. A control stick that converts pilot control actions into representative electrical signals for input to the on-board computers is a valid choice in this context. This choice presents the design options of either using the force applied on the control stick, or its angular displacement, or both, as bases for the electrical input signals. In this study, a force side-stick and a displacement center-stick are designed and installed on a fixed-base simulator and a preliminary evaluation of both devices is conducted. There are four stages of development in this project. The first is the modification of the existing Texas A&M University Flight Mechanics Laboratory flight simulator to upgrade it to a level at which the force and displacement devices can be compared. This phase involves design and fabrication of mechanical and electronic hardware, and software development. The second stage is the design and installation of the two types of control input devices. The third is the evaluation test design. The fourth and last stage is the conduct of these tests and the analysis of the results. The preliminary evaluation by eight test subjects, six of whom have prior flying experience, validates the design concepts and provides direction for further improvement of the devices. The results of the comparative tests indicate that preferences for either of the devices are aircraft type and task specific. The force stick is preferred for the more aggressive maneuvers of high performance fighter type aircraft while the displacement stick performs better for maneuvers in general aviation class aircraft. The force stick is very sensitive and enables quick response while the displacement stick provides feedback in the form of positional cues to the pilot, though it is not as sensitive. The primary drawback with the force stick is that it does not cue the pilot about the control input that the system receives, while that of the displacement stick is biasing due to friction. The force/response gradient for the force stick and the displacement/response gradient for the displacement stick are slightly high in the opinion of experienced test subjects. Suggestions for modifications of the control sticks and the test design are listed for a more detailed and conclusive study. These include providing an armrest for the force-stick and centering detents for both devices. Revisions in experimental method include using more test subjects (approximately 20)with more learning time to enable consistent performance of tasks.