ExperTune's Output/Valve Characterizer
Does your process oscillate towards one end of the range and is sluggish at the other? ExperTune's characterizer, helps you linearize your process for the best loop performance at any production rate.
Many control loops are difficult to tune because they are non-linear. This means that the process gain changes as a function of the measurement or controller output. Without any linearization, the controller will need to be tuned for the condition when the process gain is the highest. This results in sluggish tuning everywhere else. Linearizing these loops will improve control since the controller will be better tuned over the complete operating range.
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With a characterizer, you may be able to get uniform performance across the entire range of your process - so you can run your production at its optimum rather than de-tuning for oscillations. Use ExperTune to design a characterizer wherever servo control is important, to linearize flow loops, jacket temperature in split-range chemical reactors, slave loops in cascades or for any loop where the setpoint will change. Also use the characterizer to develop the code to use for valve characterization in MPC Controllers.
A characterizer takes the output of a PID or MPC controller and transforms it to a value so that the control loop is linear over the entire range of control. A control loop with a characterizer should allow you to have robust optimal tuning parameters anywhere over the CO range. ExperTune's method guarantees a good fit of a characterizer with the installed characteristic of the valve and process. Testing the valve alone outside the rest of the process does not guarantee a good fit to the process. Too much depends on the rest of the elements in the loop.
ExperTune's characterizer writes the code for you to use in FORTRAN, Basic, C, Structured Text, or X Y endpoints of lines. Copy and paste the characterizer code into any Windows application to use in your controller.
Steps to Build Your Characterizer
Step 1: Direct ExperTune software to develop the process characteristic: a PV vs. CO plot.
Step 2: Select a Piecewise Linear Fit to create a characterizer that is split into several line segments or Select Hyperbolic Fit to create a characterizer that uses one equation.
Step 3: With the mouse, Drag the red or blue boxes to position the lines to match or be on top of your process characteristic.
Step 4: Select the programming language you want ExperTune to use to write the code for the characterizer. If you are using a linear fit, you can also specify a listing of XY points. You can edit, copy, or cut the code from the code box.