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Multi-rate networked control of conic (dissipative) systems

Multi-rate networked control of conic (dissipative) systems,Nicholas Kottenstette,Heath LeBlanc,Emeka Eyisi,Xenofon Koutsoukos

Multi-rate networked control of conic (dissipative) systems  
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This paper presents a novel multi-rate digital- control system which preserves stability while providing robust- ness to time-delay and data loss. In addition, this architecture allows for high-order anti-aliasing filters to be included which do not adversely affect system stability. Therefore, it allows for improved noise-rejection and system performance as compared to traditional digital control systems. It is shown that this frame- work, based on passivity-based networked control principles, can be used to control not only passive-(dissipative) systems (systems inside the sector (0;1)) but conic-(dissipative) systems which are inside the sector (愻b ) in which |a| < b, 0 < b � 1. We demonstrate the applicability of our result through the direct position control of a single-degree of freedom haptic paddle which is inside the sector ( �;1) in which 0 < � < 1. I. INTRODUCTION Our team has investigated the use of passivity for the design of Networked Control Systems (NCS) (1) in the presences of time-varying delays (2), (3). This paper presents an important new step in the design of networked control systems as it applies to control of a conic-(dissipative) plant inside the sector (a;b) in which jaj < b, 0 < b � 1 . Passive systems (4) are a special case of conic-(dissipative) systems inside the sector (0;1 ), thus this paper expands the applicability of our framework. Our approach employs wave variables to transmit infor- mation over the network for the feedback control while remaining passive when subject to arbitrary fixed time delays and data dropouts (5), (6). The primary advantage of using wave variables is that they tolerate most time-varying delays, such as those occurred when using the TCP/IP transmission protocol. In addition, our architecture adopts a multi-rate digital control scheme to account for: i) different time scales at different part of the network; and ii) bandwidth constraints. This paper provides sufficient conditions for stability of conic systems that are interconnected over wireless networks, and which can tolerate networked delays and data loss. The continuous-time bounded results can be achieved for linear and nonlinear conic systems. The paper also demonstrates how the proposed architecture can be implemented using a new linear passive sampler. Finally, our architecture can be used to isolate wideband and correlated noise without affecting stability through the use of a discrete-time anti- aliasing filter HLP(z) which was synthesized by applying
Published in 2011.
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