Real Step Action Controller - vs. Step Action Controller with position feedback
A position feedback is needed, when
- one really wants to see the valve position, or (<- Requirement)
- no Know-how of step action controller. (<- Disadvantage)
A usual PID controller calculates the control variable, in this case the position of the valve. A switched positioner coordinates the actual one with the desired position.
This has two disadvantages
- The dynamics of the servomotor isn't taken into account at the control.
- The remote position indicator is a wearing part, defined values of the control cannot be guaranteed.
PDPI-Step Action Controller (in every of our controllers)
The PDPI step action controllers of Gossen Metrawatt takes into account the complete control system after the self optimization and calculate directly the change in the position. The actual position isn't considered in the algorithm, neither measured nor estimated. The control system is closed and therefore improves the control as a rule.