Building the system

Procedure

1. Build the system shown.

2. Use Premier Submodel and save the system as MassSpringDamper.ame.

3. To ensure an equilibrium position set the value of the two duty cycle submodels so that they are constant and zero. Leave all values at their defaults.

4. Do a trial run to ensure the system is in equilibrium.

5. Plot strategic quantities like velocity and displacement against time.

6. If a steady state is not achieved, either check parameters or do a stabilizing run.

7. Switch to Linear Analysis mode and set the two output signals from the duty cycle submodels to control variables and the velocity and displacement in the mass to state observer.

8. Then set a single linearization time at the end of the run (10s) using Linear analysis > LA Times.

9. Start a new run.

10. Select Linear analysis > Frequency diagram to open the Frequency Response dialog box.

    The dialog box shown in figure Figure 91 appears. This allows you to select which control variable(s) and which observer variable(s) will be used, and the type of plot. The value of the start and final frequency, and the number of points are also displayed. Figure 91: Frequency response dialog box

    Note that you can choose the unit of frequency in Hz or Rad/s.

11. Try the Bode plot first and click on OK. Sometimes, the calculation process will not be instantaneous (depending on the number of state variables). You obtain the Bode plot directly as a semi-logarithmic strip plot as shown in figure Figure 92.

    Figure 92: Bode plot

12. Select Nichols to get a plot as shown in figure Figure 93,

    Figure 93: Nichols plot

13. Select Nyquist to get a plot as shown in figure Figure 94.

    Figure 94: Nyquist plot