Decentralized and Dynamic Bandwidth Allocation in Networked Control
Decentralized and Dynamic Bandwidth Allocation in Networked Control Systems Ahmad T. Al-Hammouri, Michael S. Branicky, Vincenzo Liberatore Case Western Reserve University Stephen M. Phillips Arizona State University April 25, 2006 Support by: NSF CCR-0329910, Department of Commerce TOP 39 -606/5/2005 Ahmad Al-Hammouri 04003, NASA NNC 04 AA 12 A, and an EESR Ohio. ICE Training grant` '05
Paper Overview n Control over Networks n NCSs, DCSs, SANETs, … n Control of Networks n Efficient BW allocation n Congestion control n Fairness n We propose a “Cof N” scheme to better serve “Cover N” Ahmad Al-Hammouri Decentralized and Dynamic Bandwidth Allocation in Networked Control Systems (WPDRTS’ 06) 2
Control over Networks Ahmad Al-Hammouri Decentralized and Dynamic Bandwidth Allocation in Networked Control Systems (WPDRTS’ 06) 3
Control over Networks Ahmad Al-Hammouri Decentralized and Dynamic Bandwidth Allocation in Networked Control Systems (WPDRTS’ 06) 4
Control over Networks n n Remote interaction (monitoring & control) with the physical world Applications: n n Industrial automation & process control Space exploration, e. g. , telerobotics Smart homes Medical sensing & surgical simulations n Automatic asset mgmt. (RFID) Ahmad Al-Hammouri Decentralized and Dynamic Bandwidth Allocation in Networked Control Systems (WPDRTS’ 06) 5
Control of Networks (Scope of the paper) n n A bandwidth allocation scheme Objectives: n n n Stability of control systems Efficiency & fairness Fully distributed, asynchronous, & scalable Dynamic & self reconfigurable Formulating the scheme in CT n NCSs regulate h based on congestion fed back from the network Ahmad Al-Hammouri Decentralized and Dynamic Bandwidth Allocation in Networked Control Systems (WPDRTS’ 06) 6
Sampling Rate & Network Congestion h=1/r l 1 Ahmad Al-Hammouri Decentralized and Dynamic Bandwidth Allocation in Networked Control Systems (WPDRTS’ 06) l 2 7
Problem Formulation n Define a utility fn U(r) that is n Monotonically increasing n Strictly concave n Defined for r ≥ rmin n Optimization formulation Ahmad Al-Hammouri Decentralized and Dynamic Bandwidth Allocation in Networked Control Systems (WPDRTS’ 06) 8
Distributed Implementation n Two independent algorithms n End-systems (plants) algorithm n Router algorithm (later on) NCS Plant p Router NCS Controller p p Ahmad Al-Hammouri Decentralized and Dynamic Bandwidth Allocation in Networked Control Systems (WPDRTS’ 06) 9
NCS-AQM Control Loop NCS Plant Model Plant q`=Σr(t) - C t P(s) = f Queue q(t) Queue p(t) f(q(t)) Controller G(s) tb Ahmad Al-Hammouri Decentralized and Dynamic Bandwidth Allocation in Networked Control Systems (WPDRTS’ 06) 10
Queue Controller G(s) n Proportional (P) Controller n GP(s) = kp n Proportional-Integral (PI) Controller n GPI(s) = kp + ki/s q 0 + Ahmad Al-Hammouri _ e G(s) u P(s) Decentralized and Dynamic Bandwidth Allocation in Networked Control Systems (WPDRTS’ 06) q(s) 11
Determination of kp and ki n Stability region in the ki–kp plane n Stabilizes the NCS-AQM closed-loop system for delays less or equal d n Analysis of quasi-polynomials, f(s, es) Ahmad Al-Hammouri Decentralized and Dynamic Bandwidth Allocation in Networked Control Systems (WPDRTS’ 06) 12
Simulations & Results 50 NCS Plants: [Branicky et al. 2002] [Zhang et al. 2001] Ahmad Al-Hammouri Decentralized and Dynamic Bandwidth Allocation in Networked Control Systems (WPDRTS’ 06) 13
Simulations & Results (cont. ) PI ¤ P ¤ Ahmad Al-Hammouri Decentralized and Dynamic Bandwidth Allocation in Networked Control Systems (WPDRTS’ 06) 14
Thank You n Questions Comments n Probing further: n http: //start. case. edu/~vxl 11/Net. Bots Ahmad Al-Hammouri Decentralized and Dynamic Bandwidth Allocation in Networked Control Systems (WPDRTS’ 06) 15
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