A new method for the design of network-based control systems, together with mathematical tools for closedloop stability assessment, is proposed. In order to preserve the closed-loop stability under random network time delays, the variable selective control (VSC) methodology is introduced, which combines the idea of variable sampling control with the packetbased control methodologies. In the proposed method, eventdriven sensors are employed, which sample the plant output just after a new control input signal is received by the actuator. The advantages are as follows: 1) the latest actual sampling period becomes equal to the most recent time delay, which is known by direct measurement; 2) better estimation of the actual plant states can be performed in the predictive controller; 3) less frequent and shorter packets need to be transferred through the network; and 4) the stability analysis becomes simpler and does not depend on variable-size matrices. In order to deal with packet dropout issue, a simple, yet effective, algorithm is adopted in the controller, where packet losses are considered as variable time delays. In light of this formulation, the networked control system can be considered as a switched linear system and, therefore, previously existing theoretical results are adopted for stability analysis of the VSC method. Simulation studies on a well-known benchmark problem demonstrate the effectiveness of the proposed method.Index Terms-Network-based control system, networked control system, packet-based control, variable sampling period, variable selective control (VSC).
In this paper, the robust vibration control of a rotating carbon nanotube reinforced composite beam subjected to a temperature rise is studied. The governing mathematical partial differential equations are derived by Hamilton’s principle based on Euler–Bernoulli beam theory. The Galerkin method is then used to obtain the temporal ordinary differential equations and therefore to perform vibration analysis. For the purpose of vibration control, piezoelectric patches are used as sensors to measure the displacement of the beam and as actuators to implement control forces. A model-free adaptive fuzzy sliding mode controller is utilized to suppress the vibration of the rotating carbon nanotube reinforced composite beam. Since the plant’s state vector cannot be measured for control purposes and only the piezoelectric sensor’s output is available, a model-free adaptive fuzzy sliding mode observer is proposed here. Simulation studies demonstrate the effectiveness of the proposed method.
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