Networked control systems by PID controller Improvement of performance degradation caused by packet loss

This study was performed to examine the performance of networked control systems (NCSs) with a PID controller. Here, we discuss packet loss, especially improvement of the response degradation caused by manipulated variable (MV) packet loss. With MV packet loss, the actuator complements MV by inputting some value to the plant. This complemented value is different from the MV calculated by the controller. This results in an inappropriate internal state of the PID controller, such as integral value, which degrades the response. Here, we propose a compensation method that 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 at the sampling time point on which MV has been lost is modified such that the actual MV is calculated using the PV and the modified SV. In addition, we propose the MV complement method, which modifies the last available MV. Finally, the effectiveness of these methods is discussed based on the results of simulation studies.