Nonlinearities and PIO with Advanced Aircraft Control Systems
HOH AERONAUTICS INC LOMITA CA
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Design methods for advanced aircraft control systems include feedbacks to stabilize relaxed-static- stability vehicles, command and feedback shaping, and gain scheduling. Extensive use of such designs increases the risk of adverse nonlinear response to pilot control inputs. A common form of this adverse response is pilot-induced oscillation PIO. This paper examines the relationship between nonlinearities in advanced aircraft control systems and PIO. The results of recent research clearly demonstrate that actuator rate limiting, alone, does not always cause PIO. Other factors. such as the degree of instability of the unaugmented airplane and level of excess demand on the control surface, are greater determinants of PIO susceptibility. The paper evaluates two other, less thoroughly documented, contributors to PIO - command shaping sensitivity and hysteresis in the flight controls. Inferences about their impact on PIO may be made, but there is not enough data to draw specific conclusions.
- Flight Control and Instrumentation
- Theoretical Mathematics