H-Infinity Static Output-feedback Control for Rotorcraft

  • Authors:

  • Jyotirmay Gadewadikar;Frank L. Lewis;Kamesh Subbarao;Kemao Peng;Ben M. Chen

  • Affiliations:

  • Systems Research Institute, Alcorn State University, Lorman, USA 39096;Automation and Robotics Research Institute, University of Texas at Arlington, Fort-Worth, USA 76118;Department of Mechanical and Aerospace Engineering, University of Texas at Arlington, Arlington, USA 76018;Temasek Laboratories, National University of Singapore, Singapore, Republic of Singapore 117508;Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Republic of Singapore 117576

  • Venue:
  • Journal of Intelligent and Robotic Systems
  • Year:
  • 2009

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Abstract

The problem of stabilization of an autonomous rotorcraft platform in a hover configuration subject to external disturbances is addressed. Necessary and sufficient conditions are presented for static output-feedback control of linear time-invariant systems using the H-Infinity approach. Simplified conditions are given which only require the solution of two coupled matrix design equations. This paper also proposes a numerically efficient solution algorithm for the coupled design equations to determine the output-feedback gain. A major contribution is that an initial stabilizing gain is not needed. The efficacy of the control law and the disturbance accommodation properties are shown on a rotorcraft design example. The helicopter dynamics do not decouple as in the fixed-wing aircraft case, so that the design of helicopter flight controllers with a desirable intuitive structure is not straightforward. In this paper an output feedback approach is given that allows one to selectively close prescribed multivariable feedback loops using a reduced set of the states. Shaping filters are added that improve performance and yield guaranteed robustness and speed of response. This gives direct control over the design procedure and performance. Accurate identification of the System parameters is a challenging task for rotorcraft control, addition of loop shaping facilitates implementation engineers to counteract unmodeled high frequency dynamics. The net result yields control structures that have been historically accepted in the flight control community.