Lead-lag filter for electro-pneumatic valve response
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Solution Overview
Problem
Electro-pneumatic control systems with volume boosters experience slow dynamics in response to small amplitude control signals, leading to significant delays in valve movement, particularly in compressor control systems where quick response is critical for preventing compressor surging.
Innovation Solution
A lead-lag filter is introduced into the control loop, with a user interface to manipulate the lead-to-lag ratio and artificial initial conditions, providing an artificial drive signal to overcome slow dynamics by increasing the output signal and compensating for differences between expected and artificial initial conditions, thereby enhancing valve response to small amplitude signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If volume boosters are designed with a built-in dead band to stabilize loop dynamics, then system stability is improved, but valve response speed to small amplitude signals deteriorates
Solution Approach 1:
The lead-lag filter performs preliminary action by generating a lead signal that anticipates the need for valve movement before the volume booster's dead band would normally trigger response. The filter creates an artificial drive signal that pushes the valve off the seat in advance, overcoming the stabilizing dead band's inertia and enabling faster response to small amplitude signals while maintaining overall loop stability.
2Speed
If bypass restrictions are incorporated in volume boosters to increase sensitivity, then response to small amplitude signals is improved, but device complexity increases
Solution Approach 1:
The lead-lag filter acts as an intermediary device that mediates between the control signal and the volume booster. Instead of modifying the volume booster's internal bypass restrictions, the filter introduces a signal processing layer that generates an artificial drive signal, effectively bypassing the dead band's restrictive effect without physically altering the volume booster's structure or increasing its complexity.
3Manufacturing precision
If positioners use travel cutoffs to ensure full seat load, then positioning accuracy is improved, but valve response time from cutoff state deteriorates
Solution Approach 1:
The lead-lag filter applies preliminary anti-action by generating a lead signal that counteracts the sluggishness introduced by travel cutoffs. When the valve approaches a cutoff state, the filter's lead component creates an artificial drive signal that prevents the valve from stalling at the cutoff, effectively anticipating and counteracting the delayed response that would otherwise occur when the positioner must wind or unwind pneumatics from the cutoff state.
Data Source
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AI summary
Systems and methods for urging a valve plug off a seat of a control valve and toward a set point in the absence of significant delay. Adjustable, user-selected input parameters to the input of a lead-lag filter in communication with the input of a control loop facilitates achieving tunable response by a control valve upon application of small amplitude inputs.