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

In this article, an 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 40 km 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. The protocol Bluetooth is used between the local PC and the robot. Internet-based remote systems are subject to variable time delays (including communication and data-sampling delays) and data packets losses (due to the unstable Internet network). We have continuously tested the RTT (round-trip-time) between the two PCs in the daytime and nighttime by the protocol ICMP (Internet Control Message). From these tests, an evaluation of the maximal time delay is obtained. Our 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.