H∞ robust controller for autonomous helicopter hovering control

Purpose - The purpose of this paper is to present the synthesis of a robust controller for autonomous small-scale helicopter hovering control using extended H-infinity loop shaping design techniques. Design/methodology/approach - This work presents the development of a robust controller for smooth hovering operation required for many autonomous helicopter operations using H-infinity loop shaping technique incorporating the Vinnicombe-gap (v-gap) metric for validation of robustness to uncertainties due to parameter variation in the system model. Simulation study was conducted to evaluate the performance of the designed controller for robust stability to uncertainty, disturbance rejection, and time-domain response in line with ADS-33E level 1 requirements. Findings - The proposed techniques for a robust controller exhibit an effective performance for both nominal plant and 20 percent variation in the nominal parameters in terms of robustness to uncertainty, disturbance wind gust attenuation up to 95 percent, and transient performance in compliance with ADS-33E level 1 specifications. Research limitations/implications - The controller is limited to hovering and low-speed flight envelope. Practical implications - This is expected to provide efficient hovering/low-speed autonomous helicopter flight control required in many civilian unmanned aerial vehicles applications. Also, the technique can be used to simplify the number of robust gain-scheduled linear controllers required for wide-envelope flight. Social implications - The research will facilitate the deployment of low cost, small-scale autonomous helicopters in various civilian applications. Originality/value - The research addresses the challenges of parametric variation inherent in helicopter hovering/low-speed control using an extended H-infinity loop shaping technique with v-gap metric.