0000000000422263
AUTHOR
V. Casanova
Multi-rate PID Controller for a Networked Control System
In networked control systems several devices (controller, process and others) share a common communication bus. This feature can suppose delays when those devices try to transmit information through the unique bus, leading to a non- regular behaviour, that is, different variables are sampled and updated in a non-uniform way along the time. As a result, if the control system is designed by means of classical design techniques, control performance can be degraded, since these techniques used not to consider those delays. In order to undertake this problem, a solution based on a PID controller's parameters readjustment is proposed. This approach permits to retune these parameters depending on …
Kalman filtering applied to Profibus-DP systems. Multirate control systems with delayed signals
In networked control systems several devices (controllers, sensors and actuators) share a common communication resource. This feature can introduce variable and even random delays when those devices try to transmit information through the shared medium. The limited bandwidth capabilities of the transmission medium also can restrict the freedom to set the sampling periods in the control loop. An attempt to reduce the significance of the signal delays and save to some bandwidth can be based on high values of sampling periods. Usually this solution has remarkable effects in the system performance because with higher sampling periods closed loop response capabilities are decreased. This paper p…
A giant exoplanet orbiting a very-low-mass star challenges planet formation models
Surveys have shown that super-Earth and Neptune-mass exoplanets are more frequent than gas giants around low-mass stars, as predicted by the core accretion theory of planet formation. We report the discovery of a giant planet around the very-low-mass star GJ 3512, as determined by optical and near-infrared radial-velocity observations. The planet has a minimum mass of 0.46 Jupiter masses, very high for such a small host star, and an eccentric 204-day orbit. Dynamical models show that the high eccentricity is most likely due to planet-planet interactions. We use simulations to demonstrate that the GJ 3512 planetary system challenges generally accepted formation theories, and that it puts con…