Eigenstructure Assignment for the Control of Highly Augmented Aircraft

Eigenstructure assignment is utilized to design flight control laws for aircraft with many control effectors. We show that a previous eigenstructure design for the Flight Propulsion Control Coupling (FPCC) aircraft lateral dynamics with three control surfaces exhibits a lack of stability robustness because the control distribution matrix is nearly rank-deficient. We present a method for reducing the control space to two dimensions by using the singular value decomposition. After the design is complete, we map the controller back to the original three-dimensional control space. This design approach yields a controller with both smaller gains and improved multivariable stability margins at the aircraft inputs. An interesting charcteristic of the control mapping, as applied to our example, is that the most effective inputs have the larger gains while the less effective inputs have smaller gains.