Operation
The Accutune III algorithm provides
Once Accutune III has been enabled in the TUNE setup group, either “SLOW” or “FAST” tuning may be used. Which one is used is selected via the lower display during normal operation.
For the SLOW selection, the controller calculates conservative tuning constants with the objective of minimizing overshoot. If the controller determines that the process has appreciable dead time, it will automatically default to use Dahlin Tuning, which produces very conservative tuning constants. The SLOW selection may be useful for TPSC and Position Proportional applications, as it reduces “hunt” problems for the motor. This selection is also recommended for applications that have significant deadtimes.
For the FAST selection, the controller calculates aggressive tuning constants with the objective of producing quarter damped response. Depending upon the process, this selection will usually result in some overshoot. For this reason, it may be desireable to enable the FUZZY tune selection. See Section 4.6. When Fuzzy tune is enabled, it will work to suppress or eliminate any overshoot that may occur as a result of the calculated tuning parameters as the PV approaches the setpoint. This selection is best suited for processes with a single lag or for those that do not have any appreciable deadtime. FUZZY tuning does not work well for processes that have appreciable deadtime.
The Accutune III tuning process will cycle the controller’s output two full cycles between the low and high output limits while allowing only a very small Process Variable change above and below the SP during each cycle. A “T” shows in the upper display until tuning is completed.
At the end of the tuning process, the controller immediately calculates the tuning constants and enters them into the Tuning group, and begins PID control with the correct tuning parameters. This works with any process, including integrating type processes, and allows retuning at a fixed setpoint.
4.5.1 Tune for Simplex Outputs
After “TUNE” has been enabled, you can start Accutune as shown in Table
Table 4-5 Procedure for Starting “TUNE”
| Step | Operation |
| Press | Result |
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| 1 | Configure LSP1 |
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| Until SP (Local Setpoint 1) shows |
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| Lower |
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| Display |
| in the lower display. |
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2 |
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| or |
| Until LSP1 is to the desired value. |
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3 | Switch to |
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| Until the “A” indicator is lighted (on | |||
| Man |
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| “Automatic” Mode |
| Auto |
| controllers with Manual option). |
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4 | Show Tuning |
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| Until “TUNE OFF” is shown on |
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| Lower |
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| Prompt |
| Display |
| lower display. |
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| UDC3200 Universal Digital Controller Operator Manual | 04/08 | |||||
