Patent ID: 6999853
Filing Date: 2006-02-14
Classification: F15B,G05D

Abstract:
1. A method of operating a control loop for a control valve having a throttling element coupled to a pneumatically operated actuator defining at least a first control chamber, the control loop including a pneumatic amplifier having an inlet port in fluid communication with a supply of control fluid, a first outlet port in fluid communication with the first control chamber of the actuator, and a control fluid valve assembly responsive to a control pressure signal for controlling flow of control fluid between the inlet port and the first outlet port; and an I/P converter adapted to receive an I/P drive signal and generate the control pressure signal, the method comprising: storing a reference outlet pressure signal; generating the I/P drive signal based on the reference outlet pressure signal; receiving a measurement of a pressure level of control fluid from at least the pneumatic amplifier first outlet port; comparing the measured pressure level to the reference outlet pressure signal to generate an error signal; and modifying the I/P drive signal based on the error signal.