A pressure control system for controlling pressure of a fluid in a chamber includes a pressure sensor configured to measure the pressure of the fluid in the chamber, and a valve configured to control the pressure of the fluid in the chamber by regulating flow of the fluid from the chamber. The pressure control system further includes a controller. The controller is configured to estimate the volume of the chamber, and to generate a pump speed curve of the valve. The controller is further configured to monitor and modify the pump speed curve so as to maintain a slope of the pump speed curve to at least a minimum value, and to use the modified pump speed curve to adjust the position of the valve in response to pressure measurements by the pressure sensor, so as to maintain the pressure in the chamber at a desired pressure setpoint.