Over the last five years a wide variety of WirelessHART transmitters have been introduced by the major manufacturers of field devices. The PIDPlus enables closed loop control using the slower update rate provided by a wireless transmitter. The broad acceptance of wireless transmitters has generated an interest in the application of wireless throttling valves in control. However, when using a wireless valve the control must be structured to utilize the slower update rate of a wireless actuator and to handle loss of communications to the actuator. To address these added requirements the PIDPlus is designed to use communicated valve stem position in the positive feedback network that is used to create the integral contribution as illustrated below.
By structuring the PIDPlus in this manner it is possible to automatically accommodate the slower update rate to the valve. Also, this enables the PIDPlus to outperform the PID during and after loss of communication with the valve as shown below.
The use of valve position feedback in control when using a wireless valve was first address in our original work on the PIDPlus. Since that time we have explore and made further enhancements that allow a broad range of control application to be addressed using a wireless throttling valve .