“…Over the past two decades, there has been extensive study on singular systems encompassing such issues as solvability [1,3,4], controllability and observability [9,10,20,27,28], pole assignment and the elimination of impulsive behavior [7,10], LQG control [2,6,8,19,26], output regulation [17,22], and input-output decoupling [23], and so on. Such efforts not only have extended many research results on normal systems to this more general class of dynamic systems, but also led to many practical applications involving economics [24], power systems [14], robot control [25], etc.…”