- Title
- Control and scheduling for systems affected by random packet loss
- Creator
- Peters, Edwin G.W.
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2018
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Modern technologies in manufacturing, transportation, energy generation and distribution, smart buildings, smart cities and so on heavily involve large-scale, distributed networked control systems (NCSs). Nowadays, the communication between sub-systems within a NCS occurs mostly over wired networks. However, in large scale systems, the cost of installation and maintenance of these wired networks can be significant. One method of cost reduction while also gaining flexibility, is to replace these wired networks with wireless networks. Utilizing wireless networks within NCSs allows for greater flexibility, since no new cables have to be installed when adding new sensors and/or actuators. Further, it opens upfor the use of remote sensors and actuators in locations, that are prohibitive with cabled networks. These sensors and actuators can be battery powered and mounted on moving objects, such as vehicles or drones. This opens up for entirely new possibilities for control and sensing within NCSs. However, wireless networks introduce network effects that can severely affect the performance of the sub-systems, and in some cases, lead to instability. These effects include, but are not limited to, congestion, interference, packet loss and bandwidth limitations. In this thesis, we address the controller and estimator design for NCSs that are connected with wireless networks. We show, that designs that take these network effects into account can not only achieve increased performance, but also guaranteed closed-loop stability. The first part of this thesis considers the synthesis and analysis of controllers and estimators for networks affected by random packet loss. In particular, Chapter 3 considers controller and estimator synthesis and analysis for linear systems affected by independent and identically distributed packet loss. We establish a form of duality that extends the duality in the classical linear quadratic Gaussian result to the design for systems affected by packet loss. Chapter 4 extends the results from Chapter 3 and presents a method to synthesise controllers for networks where the packet loss model contains memory as well. This however results in a large number of controllers. To reduce the amount of controllers, we present three methods that trade-off controller complexity and control performance. The second part of this thesis (Chapters 5 and 6) considers the control design problem for a large distributed system with a bandwidth limited wireless network. The wireless transmission protocol features a limited number of reliable transmission slots with negligible packet dropouts and a more widely available transmission period, where packet collisions and delays occur more frequently. We propose a controller and scheduler co-design that optimally selects both the schedule on which actuators to address, and the control inputs for the sub-systems that are addressed. Simulation studies illustrate that the online optimal co-design method results in significantly improved performance over heuristic scheduling. However, the computational complexity for the online algorithms makes practical implementations of the proposed method prohibitive. To reduce the computational complexity, the design is extended by the use of a novel model predictive control (MPC) algorithm that combines approximations to infinite horizon cost functions with a short online prediction horizon. This results in improved control performance while maintaining relatively low computational complexity. In this thesis, we show that taking networks effects, such as packet loss and bandwidth limitations, directly into account in the controller and estimator design phase leads to significant performance gains and in some cases, guaranteed closed-loop stability.
- Subject
- networked control; control over networks; packet loss; packet dropouts; scheduling
- Identifier
- http://hdl.handle.net/1959.13/1385396
- Identifier
- uon:32217
- Rights
- Copyright 2018 Edwin G.W. Peters
- Language
- eng
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 1 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 354 KB | Adobe Acrobat PDF | View Details Download |