Part III: SISO Control Design
In the previous part of the book, we introduced the basic techniques by which control system synthesis could be achieved. These are the elements used to manipulate a controller to achieve given specifications.
It turns out, however, that the performance properties typically covered by specifications cannot be addressed separately by a design since they form an interwoven network of trade-offs and constraints. Fast compensation for disturbances for example, is not a separate degree of freedom from the common requirement of achieving insensitivity to modeling errors or conservation of control energy and utilities. Thus the control engineer needs to ease a feasible solution into this complex web of trade-offs, compromises and constraints. Doing this in a systematic and deliberate fashion is what we call control system design.
Design, which is the key task of the control engineer, is based on a thorough understanding of analysis, synthesis and design limitations. The first two chapters of this part of the book cover fundamental design limitations in both the time and frequency domains. The third chapter introduces ideas that are very commonly employed in practice including feedforward and cascade structures. The final chapter discusses ways of dealing with input saturations and slew rate limits. These are ubiquitous problems in real world control system design.