Supervisory control via the Internet and time delay estimation

The main objective of this research is to demonstrate experimentally the feasibility of using the Internet for distributed real-time control. A ball magnetic levitation (maglev) system was developed as a test bed for the experimental verification. In the first part of this paper we present the successful establishment of supervisory control of the test-bed via the Internet. With the supervisory control it has been shown that a client can change the position commands, modify the control parameters, and receive the experimental results in real time. In the latter part of the paper a methodology to increase the upper bound for time delays that can be accommodated in the control loop has been presented. The upper bounds of time delays that can be accommodated in the control loop for a lead-lag compensator designed in the continuous domain were estimated experimentally for various sampling frequencies. The mean time delay that can be accommodated in the control loop is 90 s when the time delays vary according to uniform distribution. To increase this upper bound of time delays a new lead-lag compensator was designed directly in the digital domain and a methodology of timeout and sensor data estimation has been proposed. The methodology of sensor data estimation and the new digital lead-lag controller running at a sampling frequency of 333.3 Hz increased the upper bound of mean time delay from 90 s to 836 s for delays following a uniform distribution.

Supervisory control via the Internet and time delay estimation Conference Paper