Partial Relative Gain: A New Tool for Control Structure Selection

A new procedure for analysis and selection of control structures is presented. In addition to the relative gain array (RGA) for the entire openloop system, the RGA for the system under partial control is considered. This partial relative gain (PRG) provides necessary conditions for a control configuration to be integral controllable with integrity. The PRG also solves the variable pairing problem in cases where conventional use of the RGA fails or is ambiguous, whichmay occur for systems larger than 2 × 2. Furthermore, it may be inferred from the PRG when block-decentralized control should be considered