Anti-windup Filter for Control Signal Clamping
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Solution Overview
Problem
Standard anti-windup systems require knowledge of the input range and the ability to adjust the controller integrator value, which is not feasible in scenarios where communication between the controller and the connected system is limited, such as in cases like room temperature controllers with fan coil units or during retrofitting, leading to delayed reactions and poor control quality.
Innovation Solution
An anti-windup reference shaping filter that receives output from the controller and adjusts it to stay within the system's time-variable range limits without needing feedback to the controller, using a block diagram implementation that includes upper and lower limits to offset the input signal and maintain the output within acceptable ranges, allowing for real-time adaptation to environmental changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard anti-windup system is used to adjust the controller integrator value, then the controller output can be kept within the input range, but the system requires communication channels that are not available in retrofitting scenarios or when connected to systems like fan coil units
Solution Approach 1:
The patent introduces an intermediary anti-windup system that sits between the controller and the controlled system. This intermediary monitors the controller output and adjusts the integrator value without requiring direct communication with either the controller or the controlled system, thus resolving the contradiction by adding a mediating component rather than modifying existing communication infrastructure
Solution Approach 2:
The patent implements a feedback mechanism where the anti-windup system monitors the actual output of the controlled system and uses this information to adjust the controller integrator value. This feedback loop enables the system to maintain reliability by keeping the output within the input range without requiring advance knowledge of the input range or direct communication channels
2Device complexity
If simple clamping of the controller output is used without anti-windup system, then the device complexity is reduced, but the controller reaction becomes delayed and control quality deteriorates due to unconstrained integrator values
Solution Approach 1:
The patent applies preliminary action by proactively adjusting the controller integrator value before the output can become excessively constrained. The anti-windup system continuously monitors and makes preventive adjustments to the integrator, ensuring that the controller can react promptly to disturbances without the delays that would result from simple clamping
Solution Approach 2:
The feedback mechanism in the anti-windup system enables real-time monitoring of the controller output and immediate adjustment of the integrator value when needed. This continuous feedback loop prevents the accumulation of large integration errors that would cause delayed response, thereby maintaining fast controller reaction without requiring complex system structure
3Reliability
If the controller integrator value is adjusted to maintain output within range, then control quality improves, but this requires the controller to know the correct input range which is not available in communication-limited scenarios
Solution Approach 1:
The patent uses feedback to eliminate the need for the controller to know the input range in advance. The anti-windup system monitors the actual output of the controlled system and feeds this information back to adjust the integrator value, thereby achieving output range compliance through observation rather than prior knowledge
Solution Approach 2:
The anti-windup system acts as an intermediary that bridges the information gap between the controller and the controlled system. It monitors the output and translates this information into appropriate integrator adjustments, allowing the controller to maintain output within range without direct knowledge of the input range requirements
Data Source
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AI summary
A device includes an upper limit input to provide an upper limit value, a lower limit input to provide an upper limit value, a control signal input to receive a control signal from a controller, an output, and circuitry coupled to the upper limit input, the lower limit input, and the control signal input to provide an output signal on the output that is constrained by the upper limit value and the lower limit value and that follows the control signal derivative if possible.