Abstract
This paper considers a wireless networked control system (WNCS) where the controller and controlled object (plant) are connected via an unreliable wireless network. The control system should be designed considering the reliability of the given network while its network reliability is controllable by changing transmission power. Thus, this paper provides a joint optimization of transmission power and control-input for the focused WNCS, which is a kind of cross-layer design of communication and control layers. This work assumes that the total transmission power for the feedforward (from the controller to plant) and feedback (from the plant to controller) channels is limited and can be adaptively allocated to each wireless channel. If more transmission power is allocated to the feedforward channel, the control-input can be more reliably transmitted, while the control-state is less reliably transmitted over the feedback channel. Furthermore, the appropriate power allocation depends on the control-state and the previous communication results. Considering the above facts, this paper proposes a model-predictive control (MPC) based joint optimization and shows that the proposed system can provide appropriate power allocation and control-input and thus can enhance the quality of control.
Highlights
In the last few decades, the rapid development of control, computer, sensor, and communication technologies has changed the structure of control systems to networked control systems (NCSs)
This paper focuses on a wireless networked control system (WNCS) where the plant to be controlled and the controller are separately located and are connected via wireless links
It is emphasized that the uncertainties caused by the communication error at the feedforward and/or feedback channels are controllable by adopting appropriate power allocation
Summary
In the last few decades, the rapid development of control, computer, sensor, and communication technologies has changed the structure of control systems to networked control systems (NCSs). This work first makes the model of the WNCS correspond to the probabilities of the communication error at the feedforward and/or feedback channels and provides the cost function considering the quality of control at the plant and the accuracy of estimation at the controller. The cost function based on the quality of control and the accuracy of estimation depending on the probabilities of communication error at the feedforward and feedback channels are provided. Computer simulations show that the proposed optimization can adaptively change the transmission power and give the optimal control-input depending on the quality of control and the accuracy of the estimation result, which can enhance the robustness and reliability of the WNCS over fading channel. Let Pr(x) and E[X] be the probability of the event x and the expected value of a random variable X, respectively
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