Week 04 of 15 – Terms	Name: Answer Sheet

In your own words, write a definition for each of the following terms. Plagiarism will be checked and not tolerated. 5-pts./each

Points: 5 pts/each = 8 * 5 = 40 pts

Feedforward

A control action that is taken to compensate for the effect of a sensed input disturbance. Also called open-loop control or anticipatory control.

Ratio control

A control that maintains a predetermined ratio between two or more variables or that maintains the magnitude of a controlled variable at a fixed ratio to another variable.

Wild variable

In ratio control, it is the variable that fluctuates according to requirements of the process.

Cascade control

1. Control action in which the output of one controller is the set point for another controller. [ANSI/ISA-77.42.01-1999] 2. A control system composed of two loops where the set point of one loop (the inner loop) is the output of the controller of the other loop (the outer loop). 3. A control technique that incorporates a master and a slave loop. The master loop controls the primary control parameters and establishes the slave-loop set point. The purpose of the slave loop is to reduce the effect of disturbances on the primary control parameter and to improve the dynamic performance of the loop.

Selective control

Selective control, as in cascade control, uses two controllers and only one final control element. The difference being that in selective control, each controller is independent from the other. Either one of the controllers may be in control at any moment; however, when one of the controllers is in control, the other one is overridden and will be ineffective.

Auctioneering

A device that automatically selects either the highest or the lowest input signal from among two or more input signals. This device is sometimes referred to as a “signal auctioneer.” [ANSI/ISA-51.1-1979 (R1993)]

Split-Range control

An action in which two or more signals are generated or two or more final control elements are actuated by an input signal. Each signal responds consecutively, with or without overlap, to the magnitude of that input signal. [ANSI/ISA-51.1-1979 (R1993)]. Also referred to as Signal Amplitude Sequencing.

Algorithm

1. A finite set of well-defined rules for solving a problem in a finite number of steps. [ISA-TR50.02, Part 9-2000] 2. Detailed procedures for giving instructions to a computer. 3. Contrast with heuristic and stochastic. 4. A recursive computational procedure. 5. A step-by-step procedure for solving a problem or accomplishing an end. 6. Sometimes used to refer to a firmware or a software program.