Parameterisation of extended systems

The Youla-Jabr-Bongiorno-Kucera (YJBK) parameterisation approach to stabilising controllers is extended to handle systems with additional sensors and/or actuators. It is shown that the closed-loop transfer function is still an affine function of the YJBK parameters in the nominal case. Furthermore, some closed-loop stability results are also given for uncertain systems. These results are important in connection with fault-tolerant control.