A new suboptimal control for cascaded nonlinear systems

A new suboptimal control design technique is proposed for a class of cascaded nonlinear systems. The design is based on a forward recursive design rather than a backstepping design, and it utilizes a nonlinear tracker derived using the state-dependent algebraic Riccati equation approach. The proposed design has two features: 1) it provides suboptimal performance with respect to a performance index that is defined in terms of original state and control variables and thus can be prescribed; and 2) the forward recursive procedure eliminates differentiation of fictitious controls, which makes the design less conservative and much simpler in applications