MISO structure based control-relevant identification of MIMO systems

The prefilter based open loop control-relevant identification scheme proposed for single input single output (SISO) systems by Rivera et al. is extended here for multi input multi output (MIMO) systems using a multi input single output (MISO) structural framework. By selecting input output pair for control, the MIMO system is partitioned into individual SISO systems with the interacting branches acting on each SISO loop being treated as structured measured disturbances (in addition to the regular disturbance at each output). With this consideration, a methodology is proposed for design of separate prefilters for the individual channels, taking into account the performance specifications for each loop. The use of an uncorrelated set of inputs is proposed for obtaining accurate estimation of individual channel elements. The prefiltering for each individual loop has been shown to give good estimates of the control-relevant model for the direct as well as the interacting branches. Closed loop simulations, using decoupled internal model controllers, involving representative processes taken from literature demonstrate the validity of the approach.