Analysis of Pilot-Induced-Oscillation and Pilot Vehicle System Stability Using UAS Flight Experiments

Abstract

This paper reports the results of a Pilot-Induced Oscillation (PIO) and human pilot control characterization study performed using flight data collected with a Remotely Controlled (R/C) unmanned research aircraft. The study was carried out on the longitudinal axis of the aircraft. Several existing Category 1 and Category 2 PIO criteria developed for manned aircraft are first surveyed and their effectiveness for predicting the PIO susceptibility for the R/C unmanned aircraft is evaluated using several flight experiments. It was found that the Bandwidth/Pitch rate overshoot and open loop onset point (OLOP) criteria prediction results matched flight test observations. However, other criteria failed to provide accurate prediction results. To further characterize the human pilot control behavior during these experiments, a quasi-linear pilot model is used. The parameters of the pilot model estimated using data obtained from flight tests are then used to obtain information about the stability of the Pilot Vehicle System (PVS) for Category 1 PIOs occurred during straight and level flights. The batch estimation technique used to estimate the parameters of the quasi-linear pilot model failed to completely capture the compatibility nature of the human pilot. The estimation results however provided valuable insights into the frequency characteristics of the human pilot commands. Additionally, stability analysis of the Category 2 PIOs for elevator actuator rate limiting is carried out using simulations and the results are compared with actual flight results.

Parameters design for feel system of aircraft active inceptor controller

“…The bandwidth phase criterion [17] evaluates the PIO tendency of the system by calculating two charact eristic values which are the bandwidth 𝜔 and the system time delay 𝜏 , making it suitable for study ing the delay characteristics of the feel system. 𝜔 𝑚𝑖𝑛 𝜔 • , 𝜔 • (6) Where 𝜔 ° is the frequency value when the phase angle is -180°, 𝜔 • is the frequency value corresponding to the amplitude when the phase angle is -180° plus 6 dB, 𝜔 • is the frequency v alue when the phase angle is -135°.…”

Evaluation of the controllability of a remotely piloted high-altitude platform in atmospheric disturbances based on pilot-in-the-loop simulations

“…The same is true for the measurement signals that are obtained by the sensors on board, sent to the control station on ground and monitored there. Depending on the respective aircraft and the order of magnitude of the latencies, these latencies can lead to pilotinduced oscillations [20][21][22] or at least impede the pilot from assessing the current flight conditions properly. Therefore, latencies can bear a risk with respect to flight safety.…”

Prediction of limit cycle oscillations in piecewise linear systems with multiple piecewise nonlinearities

“…In other words, if we can find a positive definite matrix P that satisfies (9), the absolute stability of the system 5 is guaranteed by the KYP lemma and the Popov criterion.…”

“…Now we need to check if this configuration is absolutely stable. We try to find the matrix P in (9), which is equivalent to the following LMI problem [33].…”

“…By approximating the input and output signal as a unimodal sinusoidal form, DF of a PN is modeled as a phasor representation to enable the linear steady state frequency response analysis. The simplicity and accuracy of DF analysis has entailed many studies on the piecewise linear systems including the flight control systems involving the LCO analysis [7][8][9][10][11]. If, however, the frequency of LCO turns out to be relatively low compared to the system bandwidth of the linear part, or if there are more than two PNs in parallel, then the accuracy of the LCO parameter prediction significantly decreases [12].…”