Quantitative feedback design and construction of a two by two system with large disturbances.
The quantitative feedback theory (QFT) of Horowitz is theoretically well developed for multivariable systems but there is not sufficient knowledge on its application to practical problems. A "flying machine" consisting of an airframe with two independently controlled sets of wings has been designed and constructed as a 2-input 2-output control problem. The airframe is constrained to move vertically on guide wires and to rotate about a pivot. Air flow over the wings is provided by two 7.SkW fans operated without any attempt at providing non-turbulent flow. The arrangement of the wings is such that in open loop, the dynamic behaviour of the airframe from the rear set of wings to the height is non-minimum phase. Additionally, the airframe is unstable for some flight conditions. This uncertain, non-linear and highly disturbed plant provides an ideal practical environment in which to test controller design theory. The construction, modelling, parameter estimation and simulation of the flying machine is described. Three different controller structures are disGussed, with actual controller designs arrived at from QFT understanding. The controller designs for the flying machine take into account parameter uncertainty and trade off disturbance attenuation against rate and amplitude saturation at the wing angle inputs.