Furnace Temperature Control via Fuzzy Feed-Forward PID
Solution Overview
Problem
Conventional methods for controlling furnace temperature in continuous annealing furnaces face challenges due to high thermal lag and inertia, leading to oscillations and prolonged transition times, which affect product quality and yield, as they struggle to balance quick response and stability.
Innovation Solution
A control system combining fuzzy control, multiple feed forward control, and PID control to adjust coal gas and air flow, utilizing discrepancy values and gradient calculations to optimize furnace temperature adjustments, allowing for quick responses and stability improvements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If PID control is used to pursue quick response, then transit time is shortened, but overshooting increases making furnace temperature hard to stabilize
Solution Approach 1:
The patent implements feed-forward control that predicts future temperature deviations based on current trends and burner power changes. By calculating predicted temperature deviations and applying compensatory control actions in advance, the system prepares for upcoming changes rather than merely reacting to them, thus achieving quick response without excessive overshooting.
Solution Approach 2:
The patent dynamically adjusts control parameters based on real-time furnace conditions. The control system continuously monitors actual temperature, calculates predicted deviations, and adapts the control output accordingly. This dynamic adjustment allows the system to optimize between response speed and stability depending on the current operational state.
2Measurement precision
If PID control is used to pursue stability, then furnace temperature precision is improved, but transit time becomes very long
Solution Approach 1:
The feed-forward control component predicts future temperature deviations and applies compensatory actions in advance. This preliminary action reduces the need for lengthy corrective adjustments, thereby maintaining temperature precision while significantly reducing the transit time required to reach and maintain target temperatures.
Solution Approach 2:
The patent combines feed-forward prediction with feedback control. The system continuously monitors actual temperature, compares it with predicted values, and uses the deviation information to refine control actions. This feedback mechanism ensures temperature precision while the feed-forward component prevents excessive delays.
3Power
If high power burners are used for temperature control, then heating capability is improved, but thermal lag and thermal inertia increase causing temperature oscillations
Solution Approach 1:
The control system continuously monitors actual furnace temperature and uses this feedback to adjust burner power output. By comparing actual temperature with target temperature and predicted deviations, the system makes real-time adjustments to burner power, preventing overheating and temperature oscillations even when high power levels are required.
Solution Approach 2:
The patent implements dynamic control that continuously adapts burner power based on real-time conditions. Rather than using fixed high power settings, the system dynamically adjusts power output according to actual temperature measurements, predicted deviations, and rate of change, thereby maintaining heating capability while preventing thermal lag-induced oscillations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system enhances furnace temperature control precision, reduces overshooting, and shortens transition times by using fuzzy control for steady-state and multiple feed forward control for unsteady-state conditions, improving overall temperature stability and product quality.
Implementation Method 1
a thermocouple disposed adjacent to a burner, and used for detecting furnace temperatures
Data Source
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AI summary
A method for controlling furnace temperature of a fired heating furnace is disclosed, comprising: measuring furnace temperatures to obtain furnace temperature feedback values; calculating the differences between furnace temperature setting values and the furnace temperature feedback values as discrepancy values DV1, in accordance with the furnace temperature feedback values and the furnace temperature setting value; calculating the differences between the furnace temperature setting values and the furnace temperature feedback values in a unit time, i.e., the gradient of furnace temperature change values, as discrepancy values DV2; obtaining a speed V of a fired heater machine set from a speed adjuster of the fired heater machine set, and obtaining a first multiple feed forward output components FFV in accordance with the speed V of the machine set (V); obtaining a second multiple feed forward output components FFT in accordance with the differences between the furnace temperature setting values and the furnace temperature feedback values, i.e., the discrepancy values DV1; looking up a PID control parameter in accordance with the discrepancy values DV1 and DV2, based on fuzzy control rule, and creating an adjusting control parameter OP1 in accordance with the PID control parameter; controlling a valve for regulating coal gas flow and a valve for regulating air flow by combining the adjusting control parameter OP1 with the first multiple feed forward components FFV and the second multiple feed forward components FFT as a final control output value.