Suppression of Pilot-Induced Oscillation (PIO)
Suppression of Pilot-Induced Oscillation (PIO)

Author: Donald A. Johnson

Publisher:

Published: 2002-03-01

Total Pages: 203

ISBN-13: 9781423512158

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Closed loop instability caused by excess phase lag induced by actuator rate limiting has been suspected in many pilot-induced oscillations (PIOs) and oscillatory departures from controlled flight. As part of the joint AFIT/TPS program, a longitudinal pilot command notch filter activated by a real- time oscillation verifier (ROVER) algorithm was developed to eliminate the PIO source for any developing, severe PIO. Closed loop computer simulations were conducted to prepare for the flight test. The HAVE ROVER flight test project was flown using the NF-16D Variable Stability In-flight Simulator Test Aircraft (VISTA). A programmable heads-up display (HUD) was used to generate a tracking task simulating Category A fighter maneuvers. 6 of the 12 evaluation sorties were flown against an airborne target aircraft. Flight test results showed the stick filter was pivotal in preventing aircraft oscillatory departures and suppressing PIOs. With the original threshold settings, the ROVER algorithm correctly characterized pilot observations of the aircraft motion 72% of the time. Further analysis indicated that a high false detection rate was responsible for this relatively low correct detection rate. These results suggested that the threshold values used by ROVER to detect PIO were set too low. By varying the threshold values as part of a parametric study, a maximum overall correct detection rate of 82% was attained.

An In-flight Investigation of Pilot-induced Oscillation Suppression Filters During the Fighter Approach and Landing Task
An In-flight Investigation of Pilot-induced Oscillation Suppression Filters During the Fighter Approach and Landing Task

Author:

Publisher:

Published: 1982

Total Pages: 154

ISBN-13:

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An investigation of pilot-induced oscillation suppress ion (PIOS) filters was performed using the USAF/Flight Dynamics Laboratory variable stability NT-33 aircraft, modified and operated by Calspan. This program examined the effects of PIOS filtering on the longitudinal flying qualities of fighter aircraft during the visual approach and landing task. Forty evaluations were flown to test the effects of different PIOS filters. Although detailed analyses have not been undertaken, the results indicate that PIOS filtering can improve the flying qualities of an otherwise unacceptable aircraft configuration (Level 3 flying qualities). However, the ability of the filters to suppress pilot-induced oscillations appears to be dependent upon the aircraft configuration characteristics. Further, the data show that the filters can adversely affect landing flying qualities if improperly designed. The data provides an excellent foundation from which detail analyses can be performed.

Results of Attempts to Prevent Departure And/or Pilot-Induced Oscillations (PIO) Due to Actuator Rate Limiting in Highly-Augmented Fighter Flight Control Systems (HAVE FILTER).
Results of Attempts to Prevent Departure And/or Pilot-Induced Oscillations (PIO) Due to Actuator Rate Limiting in Highly-Augmented Fighter Flight Control Systems (HAVE FILTER).

Author:

Publisher:

Published: 1999

Total Pages: 0

ISBN-13:

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The objective of this effort was to evaluate the effects of software rate limiting the pilot command with and without a software pre-filter on a highly-augmented fighter aircraft flight control system. The software rate limiter and software pre-filter were designed to provide protection from departure and/or pilot-induced oscillation (PIO). In statically unstable aircraft stabilized with feedback, elevator/stabilator actuator rate limiting may lead to PIOs and/or departure during aggressive maneuvers. This project examined the use of a software rate limiter (SWRL) on the pilot command and compared the results with those for the unprotected airframe. Additionally, a nonlinear rate limiter pre-filter (RLPF) was used in conjunction with the SWRL. Previous attempts to suppress PIO and/or departure tendencies using similar technologies have encountered difficulty with noise-in-the-loop and out-of-trim bias development during filter operation. This project attempted to improve previous designs using a different algorithm for the RLPF. The SWRL was found to help prevent PIO and/or departure. The RLPF plus SWRL was generally found to be more helpful than the SWRL alone at preventing PIO and/or departure. However, handling qualities deficiencies arose when using low SWRL settings and worsened with low SWRL settings used in conjunction with the RLPF.

Design of a Nonlinear Adaptive Filter for Suppression of Shuttle Pilot-Induced Oscillation Tendencies
Design of a Nonlinear Adaptive Filter for Suppression of Shuttle Pilot-Induced Oscillation Tendencies

Author: National Aeronautics and Space Administration (NASA)

Publisher: Createspace Independent Publishing Platform

Published: 2018-07-26

Total Pages: 30

ISBN-13: 9781724283573

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Analysis of a longitudinal pilot-induced oscillation (PIO) experienced just prior to touchdown on the final flight of the space shuttle's approach landing tests indicated that the source of the problem was a combination of poor basic handling qualities aggravated by time delays through the digital flight control computer and rate limiting of the elevator actuators due to high pilot gain. A nonlinear PIO suppression (PIOS) filter was designed and developed to alleviate the vehicle's PIO tendencies by reducing the gain in the command path. From analytical and simulator studies it was shown that the PIOS filter, in an adaptive fashion, can attenuate the command path gain without adding phase lag to the system. With the pitch attitude loop of a simulated shuttle model closed, the PIOS filter increased the gain margin by a factor of about two. Smith, J. W. and Edwards, J. W. Armstrong Flight Research Center NASA-TM-81349, H-1119 RTOP 992-07

Unified Pilot-Induced Oscillation Theory, Volume 3. PIO Analysis Using Multivariable Methods
Unified Pilot-Induced Oscillation Theory, Volume 3. PIO Analysis Using Multivariable Methods

Author:

Publisher:

Published: 1995

Total Pages: 110

ISBN-13:

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This work was conducted as part of a USAF initiative to develop a comprehensive theory to predict pilot-induced oscillation (PIO) tendencies due to the combined effect of all influencing elements. A PIO is a very complicated phenomenon stemming from a dynamic interaction between the pilot and the aircraft. When tight control is required of the pilot, an undesired oscillation can result. However, the adaptive nature of the human pilot makes such oscillations difficult to predict. This report describes an analysis method capable of predicting PIO tendencies due to several simultaneous dynamic factors. A unified approach involving pilot modeling, stability robustness analysis, and multivariable describing function analysis is applied to the problem of identifying aircraft with PIO tendencies. The approach is shown to have ties to existing PIO criteria and is successfully applied to the prediction of PIO tendencies of the M2-F2 lifting body.