Multivariable Control of the Bell 412 Helicopter

In December 2005 the first flight-test took place of an H-infinity controller on the National Research Council of Canada´s Bell 412 Advanced Systems Research Aircraft (ASRA). The ASRA is a helicopter which has been modified for research use; it is equipped with a programmable digital full-authority fly-by-wire control system. This paper presents results from the test, and discusses the collaborative project within which it took place. The aim of the project is to develop control laws meeting handling qualities criteria and providing structural load alleviation and flight envelope protection. Piloted simulation using Liverpool´s advanced flight simulator is a feature of the research. One of the first goals of the project was to produce simulation models of the test aircraft. The paper discusses how the new models were used in a control law design. Results from flight test of the control law are presented. Using linear analysis, closed-loop bandwidths of 4.2 rad/s in roll and 3.0 rad/s in pitch were accurately predicted