Sampling Rate Scheduling and Digital Filter Co-design of Networked Supervisory Control System

A networked supervisory control system is one type of networked control systems (NCS) in which a supervisor monitors and analyzes remote plants via communication network. This paper proposes an adaptive multiple sampling rate scheduling (AMSRS) methodology with digital filters in the signal process steps of the control loop to maintain the transmitted measurement signals' fidelity in order to help supervisor's decision making under normal and faulty operating conditions. Specifications of digital filters are chosen according to the system's frequency domain characteristics to bound the signal sampling and reconstruction errors as well as conserve available resource. A networked high throughput screening (HTS) process supervisory control system is used as a case study in this paper to demonstrate the effectiveness of using digital filters in the sampling rate scheduling method. A comparison between using the digital filter and previous zero-order hold approach (Z. Li and M.-Y. Chow, 2006) in signal reconstruction shows that digital filters can further reduce the reconstruction error. Furthermore, the use of filters extensively reduces the amount of consuming bandwidth (resource) in signal sampling and transmission (e.g., 40% and 56% bandwidth saved by two types of digital filters in specific case), and improves the system performance bounded by the limited resources.