Networked control and observation for Master-Slave systems

2009, 350 p. 110 illus., Hardcover. ISBN: 978-0-387-85594-3This chapter concerns the design of a remote control loop constituted by a Slave system (with computing and energy limitations) and a Master computer, communicating via an Internet connection. In such a situation, the communication cost is reduced but the Quality of Service of the Internet connection is not guaranteed. In particular, when the Slave dynamics are expected to be fast enough, the network induces perturbations (delays, jitters, packet dropouts and sampling) that may damage the performance. Here, the proposed solution relies on a delay-dependent, state-feedback control, computed by the Master on the basis of an observer. This last estimates the present Slave's state from its past sampled outputs, despite the various delays. Then, the computing task is concentrated in the Master. The theoretical results are based on the Lyapunov-Krasovskii functional and the approach of LMI, which guarantee the stabilization performance with respect to the expected maximum delay of the connection. Two strategies are applied: one is a constant controller/observer gain strategy, which takes into account a fixed upperbound for the communication delay. The second strategy aims at improving the performance by adapting the gains to the available network QoS (here, with two possible upperbounds)

Implementation of an Internet-based remote controller with guaranteed exponential stabilization

International audienceAn Internet-based remote control system is designed and implemented. The communication is based on the Master-Slave structure. The Master PC communicates with the Slave from about 40km away by UDP protocol. In order to guarantee the Master and Slave clocks to be synchronized, the NTP (Network Time Protocol) is used in both sides. The packets are sent together with time-stamps. The controller design (Master) relies on a remote observer that achieves a state prediction of the application (Slave), despite the variable communication delays. The Slave comprises a PC and a robot Miabot of Merlin company. Internet-based remote systems are subject to variable time delays (including communication and data-sampling delays). We have continuously tested the RTT (round-triptime) between the two PCs in the day-time and night-time by the protocol ICMP (Internet Control Message). From these tests, an evaluation of the maximal time delay is obtained. The structure allows one to guarantee an exponential stabilization performance, which is proven via a Lyapunov-Krassovski functional technique and involves the estimated delay upperbound. This means that the guaranteed decay rate is computed (via some LMI optimization) in relation to some maximal value of the communication delays. Of course, for greater delay values, the performance cannot be guaranteed anymore and an alternative solution has to be considered. In our system, we give a command for the robot to stop until the communication comes back to a sufficient quality

Coordination of passive systems under quantized measurements

In this paper we investigate a passivity approach to collective coordination and synchronization problems in the presence of quantized measurements and show that coordination tasks can be achieved in a practical sense for a large class of passive systems.Comment: 40 pages, 1 figure, submitted to journal, second round of revie