Matlab bode function

The use of decibels merely results in a rescaling of the Bode plot AR axis. The decibel unit is employed in electrical communication and acoustic theory and is seldom used today in the process control field. Note that the MATLAB bode routine uses decibels as the default option however, it can be modified to plot AR results, as done in Fig 14.2. In the rest of this chapter, we only derive frequency responses for simple transfer function elements (integrator, first-order, second-order, zeros, time delay). Software should be used for calculating frequency responses of combinations of these elements. 

For now, we ll take a look at the construction of Bode and Nyquist plots of transfer functions that we have discussed in Chapters 2 and 3. Keep in mind that these plots contain the same information G(jco). It is important that you run MATLAB with sample numerical values while reading the following examples. Yes, you need to go through MATLAB Session 7 first. 

The MATLAB function bode () returns the actual magnitude even though the documentation says dB. This is a detail that we can check with the function f reqresp () as explained on our Web Support, especially with future upgrades of the software. 

The MATLAB Control Toolbox makes it quite easy to generate frequency response plots for both openloop and closedloop systems. Table 11.3 gives a MATLAB program that generates Bode plots and Nichols plots. The process example is the three-heated-tank system with the openloop transfer function... 

The Bode plot is shown in Fig. 14.5. The steady-state gain (K = 5) is the value of AR when w 0. The phase angle at high frequencies is dominated by the time delay. The MATLAB listing for generating a Bode plot of the transfer function is shown in Table 14.1. In this listing the normalized AR is used (AR/ ). 

Using MATLAB, plot the Bode diagram of the following transfer function ... 

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