H∞-model of the human pilot controlling unstable aircraft

An H_∞-model of the human pilot is proposed to assess the compensation efforts required for the pilot to comply with the Neal-Smith criteria (1970) in controlling an unstable aircraft. It is shown that the Neal-Smith criteria can be reduced to an H_∞ -norm to make a mixed-sensitivity problem. The H_∞-optimal problem is solved by the Ozbay´s method (1993) and the Kwakernaak´s method (1985) for aircraft with static instability and with dynamic instability. The obtained H_∞ -pilot models agree generally well with the corresponding experimental describing function data, if the bandwidth frequency is varied as a parameter for the fitting. It is suggested that the H_∞-modeling of the human pilot may lead to a theoretical correlation of the controllability limit with the pilot´s compensation efforts