Page 449 - Mechanical Engineers' Handbook (Volume 2)
P. 449
440 Basic Control Systems Design
Figure 54 Simulink model of a system with actuator saturation and a rate limiter.
they can often be modeled with low-order linearized models. The coordination of the various
low-level controllers is a nonlinear problem. High-order, nonlinear, multivariable systems
that cannot be controlled with classical methods cannot yet be handled by modern control
theory in a general way, and further research is needed.
In addition to the improvements, such as lower cost, brought on by digital hardware,
microprocessors have allowed designers to incorporate algorithms of much greater complex-
ity into control systems. The following is a summary of the areas currently receiving much
attention in the control systems community.
Figure 55 Computer control system for a boiler-generator. Each important variable requires its own
controller. The interaction between variables calls for coordinated control of all loops. 1
