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LATERAL CONTROL OF HOVERING VEHICLES WITH AND WITHOUT SLING LOADS.
SYSTEMS TECHNOLOGY INC HAWTHORNE CA
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Open-loop and closed-loop lateral dynamics of hovering vehicles with and without sling loads are analyzed. Both human and automatic control are considered. Equations of motion are derived and factored transfer functions are presented for typical single- and tandem-rotor helicopters. The open-loop dynamics are shown to be similar to the longitudinal dynamics described in a preceding report. The effect of various feedbacks on closed-loop dynamics is studied. Particular attention is given to their effectiveness in relieving the load on the pilot, and he is included in the analysis through use of the human pilot describing function. The sensitivity vector method of analyzing multiloop feedbacks is introduced this method facilitates swift assessment of complicated and unusual feedbacks, such as lateral acceleration, sling angle relative to the vehicle centerline, and the output of tilted rate gyros. These feedbacks, and some others, are examined, but it is concluded that they are inferior to the conventional feedbacks of bank angle and roll rate to roll control, and heading and yaw rate to yaw control. It is shown that even the latter feedbacks require adjustment to cope effectively with differences between the with sling and no sling conditions. Author
APPROVED FOR PUBLIC RELEASE