Browsing by Subject "Telerobotics"

Now showing 1 - 3 of 3

Open Access
Explicit time-delay compensation in teleoperation: an adaptive control approach
(John Wiley and Sons Ltd, 2016) Abidi K.; Yildiz, Y.; Korpe, B. E.
This paper proposes a control framework that addresses the destabilizing effect of communication time delays and system uncertainties in telerobotics, in the presence of force feedback. Force feedback is necessary to obtain transparency, which is providing the human operator as close a feel as possible of the environment where the slave robot is operating. Achieving stability and providing transparency are conflicting goals. This is the major reason why, currently, a very few, if at all, fully operational force feedback teleoperation devices exist except for research environments. The proposed framework handles system uncertainty with adaptation and communication time delays with explicit delay compensation. The technology that allows this explicit adaptive time-delay compensation is inspired by Massachusetts Institute of Technology (MIT)'s Adaptive Posicast Controller. We provide simulation results that demonstrate stable explicit adaptive delay compensation in a force-reflecting teleoperation set up. Copyright Â© 2016 John Wiley & Sons, Ltd. Copyright Â© 2016 John Wiley & Sons, Ltd.
Open Access
An investigation of the effects of human dynamics on system stability and performance
(2018-08) Yousefi, Ehsan
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.
Open Access
Stability analysis of a human-in-the-loop telerobotics system with two independent time-delays
(Elsevier B.V., 2017) Yousefi, Ehsan; Yıldıray, Yıldız; Sipahi, Rıfat; Yücelen, Tansel
In this paper, stability of a human-in-the-loop telerobotics system with force feedback and communication delays is investigated. A general linear time-invariant time-delayed mathematical model of the human operator is incorporated into the system dynamics based on the interaction of the human operator with the rest of the telerobotic system. The resulting closed loop dynamics contains two independent time-delays mainly due to back and forth communication delay and human reaction time delay. Stability of this dynamics is characterized next on the plane of the two delays by rigorous mathematical investigation using Cluster Treatment of Characteristic Roots (CTCR). An illustrative numerical example is further provided in the results section along with interpretations.