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This paper considers the NCSs (Networked Control Systems) by PID controller. We discuss the packet losses, especially, the improvement of the response degradation caused by the MV (Manipulated Variable) packet losses. When MV packet is lost, the actuator complements the MV by some value, which is input to the plant. This complemented value is different from the MV calculated by the controller. This makes the internal state of the PID controller such as integral value inappropriate, and it degrades the response. We propose the compensation method which corrects the internal state of the PID controller. When the actual values of MV are obtained after the MV has been lost by packet loss, the value of SV (Set point Variable) at the sampling time point on which MV has been lost is modified such that the actual MV is calculated using the PV (Process Variable) and the modified SV. Moreover, we propose the MV complement method that modifies the method which holds the last available MV. And we demonstrate the effectiveness of these methods by simulation studies.

This paper proposes optimization of the PD controller gains by minimizing H∞ norm for flexible spacecraft attitude control. Solving the problem is known to be difficult because it is described by a bilinear matrix inequality (BMI) that cannot be transformed into linear matrix inequalities (LMIs). In order to solve it within practical computation time, we revise the branch and bound algorithm and incorporate the quantization of the variable domains. The ETS-VI mathematical model is used to demonstrate its ability.