Interlude: Book Review--Advanced PID Control by Astrom and Hagglund

Every so often, a book comes out that takes a very complex subject, and renders it easy to understand, without trivializing the subject, or leaving all the good stuff out. That's my take on Advanced PID Control by Karl J. Astrom (there's supposed to be diacritical marks in his name, and his co-author's but I can't do 'em here) and Tore Hagglund. Both teach at the Lund Institute of Technology, in Sweden, and are world-class authorities on control engineering. Karl Astrom is a member of the Process Automation Hall of Fame. They begin by pointing out that like many control algorithms, PID is independent of technology, having been used 250 years ago in Holland to control the speed of windmills and water mills, with some ingenious design producing mechanical integral control. PID has survived the transition from mechanical governors to digital control, to all software systems and remains "one of the key tools in the control engineer's toolset." They are also found, say Alstrom and Hagglund, "in systems as diverse as CD and DVD players, cruise control for cars, and atomic force microscopes. In process control, more than 95 percent of the control loops are of PID type;; most loops are actually PI control." Starting with the development of PID controllers, the authors lead the reader carefully to a detailed understanding of the state of the art in advanced control using PID algorithms. This is an excellent addition to the engineer's bookshelf, and you are encouraged to go to www.isa.org and buy it. Walt