Velocity-Based PID Control for Non-Periodic Feedback
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Solution Overview
Problem
Process control systems face challenges in maintaining robust control and responding quickly to setpoint changes when receiving slow or non-periodic process variable feedback, particularly in wireless control systems where communication rates are limited, leading to potential equipment damage and reduced efficiency.
Innovation Solution
A velocity-based PID control technique that generates differential control signals, allowing for robust control even with intermittent feedback, and incorporates a continuously updated filter to adapt to changes in setpoint and process responses, ensuring stable operation despite slow feedback rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If non-periodic control or slow feedback process variable communications are used, then device complexity is reduced and ease of operation is improved, but control responsiveness deteriorates and productivity decreases
Solution Approach 1:
The controller performs preliminary actions by calculating predicted process variable values based on historical data and process models before actual measurements are received. This allows the control system to proactively adjust control outputs to maintain responsiveness despite slow feedback rates, effectively preparing control actions in advance to compensate for delayed measurements.
Solution Approach 2:
The patent introduces an intermediary prediction mechanism that bridges the gap between slow feedback measurements and fast control requirements. The prediction algorithm acts as a mediator, generating intermediate predicted values that enable the controller to respond quickly to process changes even when actual feedback arrives slowly, thus maintaining control responsiveness without requiring fast communication infrastructure.
2Loss of energy
If feedback rate is slower than process dynamics, then communication bandwidth requirements are reduced and energy consumption decreases, but control precision deteriorates and manufacturing precision suffers
Solution Approach 1:
The system implements enhanced feedback mechanisms where predicted process variable values are continuously fed back into the control algorithm. This predicted feedback loop allows the controller to maintain precise control by comparing actual measurements with predicted values, enabling accurate control decisions even when actual feedback arrives infrequently, thus preserving manufacturing precision while operating at lower communication rates.
Solution Approach 2:
The patent dynamically changes control parameters based on the relationship between feedback rate and process dynamics. When feedback is slow, the system adjusts prediction horizons, smoothing factors, and control gains to optimize performance. This adaptive parameter adjustment enables the controller to maintain high precision across varying communication conditions without requiring constant high-rate feedback.
3Device complexity
If conventional PID control is used with slow feedback, then device complexity remains low, but control stability deteriorates and reliability decreases
Solution Approach 1:
The patent transforms the static PID control into a dynamic adaptive control system that automatically adjusts its behavior based on feedback rate conditions. The controller dynamically switches between different control modes (direct PID control when feedback is fast, prediction-based control when feedback is slow) and continuously adapts prediction models to match current process conditions, thereby maintaining stability and reliability without significantly increasing device complexity.
Solution Approach 2:
The system implements periodic prediction updates synchronized with the arrival of feedback measurements. Even when feedback arrives slowly and non-periodically, the controller performs periodic recalibration of prediction models and adjusts control parameters at each feedback arrival, creating a rhythmic control pattern that maintains stability. This periodic action ensures the control system remains adaptive while keeping computational complexity manageable.
Data Source
AI summary
A technique for controlling a process using slow or non-periodically received process variable measurements enables more robust controller responses to setpoint changes and disturbance changes even when the process variable measurement feedback signals are reviewed at a rate on the order of the rate associated with the response time of the process dynamic or variable being controlled. The control technique implements iterations of a control routine to generate a control signal using a reset or rate contribution component that, in some sense, defines an expected process response to the control signal. When a new measurement of the process variable is unavailable to the controller, the reset or rate contribution component is maintained at zero or at some other previous level when generating the control signal. However, the reset contribution component is iteratively recalculated during each controller execution cycle, even when no new process variable measurement has been received, so that the output of the reset contribution component incorporates expected process changes that occur as a result of a setpoint or a feed-forward change that impacts the process input or control signal between the times that actual process variable measurement values are received at the controller. This technique makes the controller more robust when producing control signals in the presence of setpoint or feed-forward changes received between the times at which non-periodic process variable measurements are received at the controller and makes the controller operate better when the process variable feedback time interval is greater, equal to or on the order of the process response time.