How do you design decoupling control for multivariable processes?

Decoupling compensates for loop interactions using feedforward elements between loops. Design: calculate decoupler transfer functions from process model (ideal decoupler inverts off-diagonal elements), implement realizable approximations (may require lead-lag elements), and tune decoupled loops independently. Static decoupling uses steady-state gains only; dynamic decoupling matches time response. Partial decoupling may be practical when full decoupling is complex. Alternative: use MPC which handles interactions inherently. RGA analysis guides decoupler design - large off-diagonal elements indicate significant interaction requiring decoupling.