Centralized PI controllers for interacting multivariable processes by synthesis method

► Two methods of designing a centralized control system for multi-input, multi-output (MIMO) processes are presented. ► The inverse of the process transfer function matrix is approximated based on the relative gain array concept. ► The method is improved by using a relative normalized gain array, and an equivalent transfer function. ► The controllers reduce the interactions better than recently reported decentralized controllers do.