Page 426 - Mechanical Engineers' Handbook (Volume 2)

8 Compensation and Alternative Control Structures 417

Figure 35 Passive electrical compensators: (a) lead; (b) lag; (c) lead–lag.

8.4 State-Variable Feedback
There are techniques for improving system performance that do not fall entirely into one of
the three compensation categories considered previously. In some forms these techniques
can be viewed as a type of feedback compensation, while in other forms they constitute a
modification of the control law. State-variable feedback (SVFB) is a technique that uses
information about all the system’s state variables to modify either the control signal or the

Figure 36 Cascade control structure.