An investigation of the effects of human dynamics on system stability and performance
Author
Yousefi, Ehsan
Advisor
Yıldız, Yıldıray
Date
2018-08Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
143
views
views
79
downloads
downloads
Abstract
Considered as a challenging element of closed-loop structures, the human operator,
and his/her interactions with the underlying system, should be carefully
analyzed to obtain a safe and high performing system. In this thesis, the interaction
between human dynamics and the closed loop system is investigated
for two different scenarios. The first scenario consists of a
ight control system
controlled by an adaptive controller. A telerobotic system where the controllers
are conventional linear controllers is analyzed in the second scenario. Although
model reference adaptive control (MRAC) offers mathematical design tools to
effectively cope with many challenges of the real world control problems such
as exogenous disturbances, system uncertainties, and degraded modes of operations,
when faced with human-in-the-loop settings, these controllers can lead to
unstable system trajectories in certain applications. To establish an understanding
of stability limitations of MRAC architectures in the presence of humans, a
mathematical framework is developed for the first scenario, whereby an MRAC
is designed in conjunction with a class of linear human models including human
reaction delays. This framework is then used to reveal, through stability analysis
tools, the stability limit of the MRAC-human closed loop system and the range
of model parameters respecting this limit. An illustrative numerical example of
an adaptive
ight control application with a Neal-Smith pilot model is utilized to
demonstrate the effectiveness of the developed approaches. The effect of a linear
filter, inserted between the human model and MRAC, on the closed loop stability
is also investigated. Related to this, a mathematical approach to study how
the error dynamics of MRAC could favorably or unfavorably in
uence human
operator's error dynamics in performing a certain task is analyzed. An illustrative
numerical example concludes the study. For the second scenario, stability
properties of three different human-in-the-loop telerobotic system architectures
are comparatively investigated, in the presence of human reaction time-delay and
communication time-delays. The challenging problem of stability characterization
of systems with multiple time-delays is addressed by implementing rigorous
stability analysis tools, and the results are verified via numerical illustrations.
Practical insights about the results of the stability investigations are also provided.
Finally, apart from these scenarios, after the observation that a simple
linear transfer function model for a real force re
ecting haptic device, which is
used in telerobotics applications, is missing, a data-driven and first principles
modeling of the Geomagic®
Touch™ (formerly PHANToM®
Omni®
) haptic device
is considered. A simple linear model is provided for one of the degrees of
freedom based on fundamental insights into the device structure and in light of
experimental observations.
Keywords
Human-in-the-Loop SystemsModel Reference Adaptive Control
Closed-Loop System Stability
Telerobotics
Time-Delay Systems
Modelling
PHANToM®
Omni®