State observer for MIMO nonlinear systems

A state observer design for a special class of MIMO nonlinear systems which has a block triangular structure is presented. For this purpose an extension of the existing design for SISO triangular systems to MIMO cases is performed. Since the gain of the proposed observer depends on both the nonlinear and linear parts of the system, it improves the transient performance of the high gain observer. Also, by using a generalised similarity transformation for the error dynamics, it is shown that under a boundedness condition, the proposed observer guarantees the global exponential convergence of the estimation error. Finally, an illustrative example is included to show the validity of the design approach.