Getting Started

Bode Diagram Design

One technique for compensator design is to work with Bode diagrams of the open-loop response (loop shaping). Using Bode diagrams, you can design to gain and phase margin specifications, adjust the bandwidth, and add notch filters for disturbance rejection.

Example: DC Motor

The following sections use the DC motor example to show how create a compensator using Bode diagram design techniques. From "SISO Example: the DC Motor" on page 2-4, the transfer function of the DC motor is

• Transfer function:
         1.5
  ------------------
  s^2 + 14 s + 40.02
  

For this example, the design criteria are as follows:

• Rise time of less than 0.5 second
• Steady-state error of less than 5%
• Overshoot of less than 10%
• Gain margin greater than 20 dB
• Phase margin greater than 40 degrees

Loop Responses

Adjusting the Compensator Gain