Auto tune

The modern DDC controller has only the control function PID. PLC controllers used in process installations may contain more complex regulation functions, for example, the fuzzy or auto-tuning of PID functions. Most DDC controllers are self-sufficient and independent of the controllers or computer programs that are used for system configuration. 

QuanOptimize from Micromass also allows automated method development for quantitative LC/MS/MS. It automatically identifies the best method for each compound, then runs batches of samples for quantitative analyses and report results in a QuanLynx browser. Thermo recently launched a similar product for automatic MS tuning. Known as QuickQuan, it generates data and stores it in a central Microsoft Access or Oracle database for future access. The infusion-based valve switching auto-tuning device allows individual compounds to be fully and automatically optimized in about 1 min. 

Simulate several first-order lag and second-order lag plus deadlime processes on a digital computer with a relay feedback. Compare the ultimate gains and frequencies obtained by the auto-tune method with the real values of cu and obtained from the transfer function. 

In another method, called ATV (auto-tune variation), the controller is replaced by a relay of amplitude h%. The period is divided in each cycle by two up to the occurrence of oscillations. If a is the amplitude of oscillations, the ultimate gain can be calculated as ... 

S.V. Serak, N.V. Tabiryan, T.J. Bunning, Nonlinear transmission of photosensitive cholesteric liquid crystals due to spectral bandwidth auto-tuning or restoration. J. Nonlinear Opt. Phys. Mater 16, 471-483 (2007)... 

The proprietary computer software Auto-Tune, which adjusts recorded singing to the right note or pitch, has been described as Photoshop for the human voice. It was creatively misused in the recording of Cher s 1998 hit Believe. ... 

By automatic tuning (or auto -tuning), we mean a method which enable the controller to be tuned automatically on demand from an operator or an external signal. 

Fortunately, the first two disadvantages can be avoided by using either the relay auto-tuning method or the step test method described later in this section. Alternatively, if a process model is available, Kcu and can be determined from a frequency response analysis, as described in Chapter 14. 

Astrom and Hagglund (1984) have developed an attractive alternative to the continuous cycling method. In their relay auto-tuning method, a simple experimental test is used to determine Kcu and Pu> For this test, the feedback controller is temporarily replaced by an on-off controller (or relay). After the control loop is closed, the controlled variable exhibits a sustained oscillation that is characteristic of on-off control (cf. Section 8.4). The operation of the relay auto-tuner includes a dead zone as shown in Fig. 12.14. The dead band is used to avoid frequent switching caused by measurement noise. 

Figure 12.14 Auto-tuning using a relay controller.

The relay auto-tuning method also has a disadvantage. For slow processes, it may not be acceptable to subject the process to the two to four cycles of oscillation required to complete the test. 

For on-line controller tuning, the relay auto-tuning and step response methods are recommended. 

Hang, C. C., K. J. Astrdm, and Q. G. Wang, Relay Feedback Auto-Tuning of Process Controllers—A Tutorial Review, J. Process Control, 12,143 (2002). 

When a cascade control system is tuned after installation, the secondary controller should be tuned first with the primary controller in the manual mode. Then the primary controller is transferred to automatic, and it is tuned. The relay auto-tuning technique presented in Chapter 12 can be used for each control loop. If the secondary controller is retuned for some reason, usually the primary controller must also be retuned. Alternatively, Lee et al. (1998) have developed a tuning method based on Direct Synthesis where both loops are tuned simultaneously. When there are limits on either controller (saturation constraints), Brosilow and Joseph (2002) have recommended design modifications based on the Internal Model Control (IMC) approach. 

Relay auto-tuning can also be used to tune multiloop control systems. The loops can be tuned in a sequential... 

Taylor series, 65,97 artificial neural net (ANN), 124 ARX model, 126 assignable cause, 412,414,415 auctioneering control, 298 automatic mode, 139,143 autoregressive model, 126, 335-336 auto-tuning, 294 average run length, 418,419 averaging level control, 229... 

The auto-tune variation or ATV technique of Astrom is one of a number of techniques used to determine two important system constants called the ultimate period and the ultimate gain. Tuning values for proportional, integral and derivative controller parameters may be determined from these two constants. All methods for determining the ultimate period and ultimate gain involve disturbing the system and using the disturbance response to extract the values of these constants. 

---