Manual Control Adaptation to Variations in Short-Period Natural Frequency and Damping

Abstract

This paper presents the results of a human-in-the-loop experiment performed to investigate the effects of variations in aircraft short-period mode characteristics on human operators' manual control behavior. In the experiment, 15 participants performed a tracking task for a factorial variation in both short-period mode natural frequency (five settings) and damping ratio (three settings). The baseline aircraft dynamics were those of a Cessna Citation aircraft, as used in a number of previous experiments, and the variations in short-period dynamics were chosen to span a range of interest with respect to available handling qualities criteria and Maximum Unnoticed Added Dynamics (MUAD) envelopes. To objectively quantify the induced adaptation of manual control behavior, human operator models were fitted to the collected tracking data. In addition to these control behavior measures also subjective ratings of the noticeability of differences with respect to the baseline aircraft were collected. Overall, the results show consistent adaptation of manual control behavior to variations in both short-period parameters and a worsening of task performance with decreased short-period natural frequency and decreased damping ratio settings. In spite of inconsistencies in the subjective rating data, the overall objective adaptation of manual control dynamics correlates with the subjective noticeability ratings, as well as correspondence of the tested configurations with available MUAD envelopes.

Assessment of Maximum Unnoticeable Added Lag-Lead or Lead-Lag Dynamics with a Cybernetic Approach

“…Equivalent to earlier experiments, 10,11,13,14 the target forcing function signal f t for the pitch tracking task was defined as a multisine signal, consisting of N t = 10 sine waves with independent frequencies that spanned the frequency range of interest for manual control: 1,15 f…”

“…After this baseline run, participants gave a subjective rating of the noticeability any difference of the tested dynamics and the baseline, using the four-point rating scale listed in Table 3. 10,14 Of the three runs performed for each condition, the first was discarded as participants may have needed to adjust their control behavior for each condition transition. The last two measured runs were used for data analysis.…”

“…Especially added lag-lead dynamics were found to result in significantly degraded task performance and increased lead-time constants also for very low T lag . Hence, Hypothesis H3 is rejected, which implies that for the development of objective "manual control adaptation" envelopes, 12,14 with discrete envelope limits such as the MUAD of Ref. 7, extreme care needs to be taken in settings limits on the likely continuous human control behavior adaptations.…”

“…Overall, the results presented in this paper contribute to the further development of objective "manual control adaptation" envelopes, as also proposed in earlier papers. [10][11][12]14 An important next step, given the hypothesized dependency of human noticeability of added dynamics (H added (s)) on the the baseline controlled system (H baseline (s)), 8,11 an important next step is to also consider the baseline controlled dynamics as an additional degree-of-freedom. The agreement between simulation predictions and experiment data in this paper suggests that a first-order estimate of the effects of varying H baseline (s) can be obtained from a similar offline simulation analysis.…”