Enhanced frequency response estimator to guarantee pre-specified phase angle and static disturbance rejection with all harmonics removed

Sung, Su Whan; Lee, Jietae

doi:10.1007/s11814-008-0209-9

Cited by 3 publications

(3 citation statements)

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“…This section introduces the process activation method using sine signals to remove the harmonics of the process input completely, to guarantee the specified phase angle and to reject the effects of disturbances (Sung and Lee, 2008). Also, the stability conditions of the process activation method are discussed.…”

Section: Process Activation Methods Using Sine Signalsmentioning

confidence: 99%

“…They use a multistep signal, saturation-relay signal, sinusoidal signal or preload relay signal Sung et al, 1995;Shen et al, 1996;Tan et al, 2006). They use a multistep signal, saturation-relay signal, sinusoidal signal or preload relay signal Sung et al, 1995;Shen et al, 1996;Tan et al, 2006).…”

Section: Comparisons With Previous Approachesmentioning

confidence: 99%

“…As expected, the proposed method with t a ¼ 3 provides almost exact estimates for the range Àp/2 ffG(iv) Àp. The following process is simulated to compare Relay_SS with the previous methods of the conventional relay feedback method and Sung et al (1995): Table 13.12 shows the MATLAB code for Example 13.3.…”

Section: Example 133mentioning

confidence: 99%

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Modifications of Relay Feedback Methods

Sung

Lee

2009

Process Identification and PID Control

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This section introduces a closed-loop process activation method to reduce the harmonics and obtain more accurate frequency-response data of the process. It can also successfully remove the effect of the input nonlinearity by using the disturbance rejection technique. The method combines 10 pulses to generate one period of the relay signal. The 10 pulses are combined in an optimal way by solving a constrained nonlinear optimization problem to minimize the harmonics. In the implementation, the closed-loop process activation method uses the optimal solution obtained without continuing to solve the optimization problem any more. So, the implementation of the proposed method is almost as simple as that of the previous methods. Let us call it Relay_PS.The signal generated by Relay_PS (Je et al., 2009) has five pulses in the half-period, as shown in Figure 13.1. The first cycle is activated by the conventional relay feedback method. First, the relay output (equivalently, process input) u(t) ¼ ad is entered until the process output y(t) deviates from the initial value. After that, one cycle is determined as follows: u(t) ¼ Àad when y(t) ! 0 and u(t) ¼ ad when y(t) < 0. Here, d is the magnitude of the multi-pulse signal and a < 1 is introduced for a smooth transit from the conventional relay mode to the multi-pulse mode without changing the fundamental frequency term, which will be explained later. The multi-pulse signal of Relay_PS begins to enter after one cycle of the conventional relay signal, as shown in Figure 13.1. The process input of the kth cycle in the multi-pulse mode is determined as follows.When y(t) < 0, the following rules are applied, as shown in Figure 13.1:uðtÞ ¼ d; 0 t À t on;k < xð1ÞP on;k À 1 ð13:1ÞuðtÞ ¼ 0; xð1ÞP on;k À 1 t À t on;k < xð2ÞP on;k À 1 ð13:2Þ1 Enhanced process activation method to remove harmonics and input nonlinearity, Je et al. Journal of Process Control

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Section: Process Activation Methods Using Sine Signalsmentioning

confidence: 99%