Master of Engineering - Research
School of Electrical, Computer and Telecommunications Engineering
Luo, Qiongjie, Networked control for bilateral teleoperation, Master of Engineering - Research thesis, School of Electrical, Computer and Telecommunications Engineering, University of Wollongong, 2012. http://ro.uow.edu.au/theses/3728
In last few decades, an increasing number of people are beginning to realize that bilateral teleoperation plays an important role in the extension of human manipulation in fields such as space, underwater exploration, medical surgery and hazardous environments.
When it comes to the teleoperation system, the greatest consideration is the time delay over the transmission which influences the performance of the system. With the development of the Internet, in recent years an increasing number of teleoperation applications are applied over this global network. There is no denying the fact that dealing with the time delay issue on the Internet has been considered as the primary challenge as it can deteriorate system performance and even destabilize it. Many studies in the literature address the problem of the transmission delay of teleoperation across the Internet. Those among them that consider the controller design and experimental simulations are mostly focused on two kinds of time delays: constant time delay and time-varying delay. As time-varying and asymmetric delays often occur in network-based bilateral teleoperation systems, designing an appropriate control system to maintain their stability has proved to be critical.
This thesis focuses on the control of bilateral teleoperation systems across the Internet. We design a controller that takes the time-varying and asymmetric delays into account. Its key features include adaptability to time-varying asymmetric delays and stability with good transparency performance. We use new controller synthesis methods to develop the system by defining appropriate Lyapunov-Krasovskii functional. This method is developed by applying tighter bounding technology in a cross terms and weighting matrix approach. Furthermore, the controller synthesis conditions are expressed as matrix inequalities, which are solvable by existing methods. We then apply the designed controller to a linear system model with increasing forward and backward delays. Finally, an experimental validation of the developed theoretical methods is used to demonstrate the effectiveness of the proposed method, the results show that the proposed criteria improve the force tracking with less response time and less overshoot as well as with an acceptable position error.
The main contributions of this thesis are:
The study presented in this thesis provides a teleoperation system control strategy which is robust to asymmetric time-varying delay environments, improves position error control based on passivity and guarantees stability when applied across the network. This strategy adapts to realistic packet-switch communication.
This study also provides a fully networked teleoperation hardware-in-the-loop practical platform which enhances the experiment credibility, improves the results observability and makes it portable for presentation. This platform is a real-time test-bed which can be used in multi-task validations in the future.
The control strategy is tested by simulation and two hardware-in-the-loop practical platforms. One platform is a computer with two motor applications which is delay-free environment; the other platform constitutes two computers with corresponding motor applications and this platform includes realistic delay. This experiment method covers both simulation and practical validations.