Setpoint Path Generation for Control Response Reproducibility
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Solution Overview
Problem
Existing control techniques, such as those described in Japanese Patent No. 4310804, face challenges in suppressing overshoot and maintaining reproducibility when the target setpoint is repeatedly changed or disturbances are repeatedly applied, due to uncertainties and discontinuous setpoint changes, leading to decreased control response reliability.
Innovation Solution
A control device and method that includes a timing detection unit, a setpoint path generation unit, and a control computation unit, which determine a curved setpoint path for the generation setpoint to reach the target setpoint within a specified period, ensuring continuous behavior and gradual change, thereby reducing overshoot and improving reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a setpoint path is generated using the rate of change of deviation or process variable in every control computation cycle, then overshoot can be suppressed for the first setpoint change or disturbance application, but reproducibility decreases as setpoint changes or disturbances are repeated
Solution Approach 1:
The patent applies preliminary action by calculating the setpoint path in advance based on the relationship between setpoint change amount and process variable change amount, rather than computing it in real-time during each control cycle. This pre-calculated path is then followed during repeated setpoint changes or disturbance applications, ensuring consistent and reproducible control responses without requiring complex real-time computations.
2Reliability
If the setpoint ramping function is used to generate a linear setpoint path, then overshoot is suppressed when the target setpoint is changed, but the setpoint change occurs discontinuously and reproducibility decreases under repeated changes
Solution Approach 1:
The patent applies curvature by generating a setpoint path that follows a curved trajectory rather than a straight linear ramp. The setpoint path is calculated to gradually change the process variable from the current value to the target setpoint value, creating a smooth curved transition that eliminates discontinuities and ensures continuous, reproducible control responses during repeated setpoint changes.
3Adaptability or versatility
If a generation setpoint path is calculated as SLSP=SP+ΔPV/k using the rate of change, then the setpoint path can adapt to process conditions, but it is practically impossible to specify in advance a period for the generation setpoint to reach the target setpoint
Solution Approach 1:
The patent applies parameter changes by modifying the setpoint path generation approach to use a predetermined time period parameter. Instead of relying solely on real-time rate of change calculations, the system incorporates a specified time period for the setpoint to reach the target, adjusting the path calculation to ensure the process variable reaches the target within this predetermined time frame while maintaining adaptability to different process conditions.
Data Source
AI summary
A control device includes a timing detection unit, a setpoint path generation unit, and a control computation unit. The timing detection unit detects a timing at which an event indicating a change in a target setpoint or an event indicating application of a disturbance occurs, as a generation start timing at which generation of a path of a generation setpoint is started. The setpoint path generation unit determines the path of the generation setpoint in response to determination of the generation start timing at which generation of the path of the generation setpoint is started and outputs, in every control cycle, the generation setpoint that follows the determined path. In every control cycle, the control computation unit calculates a manipulated variable by performing control computation using a process variable and the generation setpoint as input values.