A study of flow-level cascade control with WirelessHARTTM transmitter using LabVIEW

Abstract

This work presents a cascade control architecture to combat network induced delays in Wireless network controlled systems. Specifically a flow-level cascade control system is considered whereby the primary process variable is liquid level, and the secondary process variable is the flow rate. The flow-level process variables are measured by Wireless HART differential Pressure (DP) transmitter and sent through a WirelessHART gateway. Control actions are provided by a control valve actuator which is manipulated through a PLC. The PLC and the WirelessHART gateway are managed by an OPC server providing a medium of communication. The PID controller gains are designed through the LabView software, in which the network induced delays is offset by adjusting the controller interval until the responses are satisfactory. Results show that cascade control outperformed the single loop control, in both handling network induced delays and coping with disturbances.