Nonlinear Robust Control on Yaw Motion of a Variable-Speed Unmanned Aerial Helicopter under Multi-Source Disturbances

Peng Tang,Junfeng Chen,Yuehong Dai

doi:10.3390/aerospace9010042

Peng Tang, Junfeng Chen + Show 1 more

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https://doi.org/10.3390/aerospace9010042

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Abstract

This paper studies the multi-source disturbances attenuation problem on the yaw motion of unmanned aerial helicopter with a variable-speed rotor. The yaw motion subsystem dominated by an electrically-driven tail rotor is firstly introduced, and its trajectory accuracy requires particularly close attention. To this end, we establish a fourth-order yaw error dynamic equation; subsequently, a nonlinear robust control scheme based on optimal H∞ principle is developed, consisting of laws of virtual functions, parameter estimation and a compensation signal. The novelty of this scheme lies in unifying the techniques to deal with the uncertain parameters, noise perturbations, actuator output fault and external airflow turbulence into a simple framework. Stability analysis guarantees that the yaw closed-loop system has the predefined performance of disturbance suppression in the sense of a finite L2-gain. Comparison results with the extended state observer based backstepping controller verify the effectiveness and superior performance of proposed scheme in an aircraft prototype.

Highlights

The unmanned aerial helicopter (UAH) has always gained attention due to its advantages of high efficiency, hover and cruise flight, but its attitude stabilization, especially the yaw channel, is much more difficult compared with that of a quadrotor aircraft, because it has strong coupling with the dynamics of the main rotor and is sensitive to manual operation
The proposed yaw controller was tested in the Xcell60 unmanned helicopter simulation platform, not just in a pure yaw dynamic model
A nonlinear robust control scheme is proposed to deal with multisource disturbances in the sense of UUB and finite system L2 -gain for a small UAH yaw channel operated in pure variable-speed mode

Summary

Introduction

The unmanned aerial helicopter (UAH) has always gained attention due to its advantages of high efficiency, hover and cruise flight, but its attitude stabilization, especially the yaw channel, is much more difficult compared with that of a quadrotor aircraft, because it has strong coupling with the dynamics of the main rotor and is sensitive to manual operation. Small unmanned helicopters almost all have a separate electronic stabilizer called an artificial yaw damping system (AYDS), which consists of an amplifier, a proportional–integral controller, an angular rate sensor and a high-frequency servo, it obviously increases the costs and reduces system reliability. For small or micro-sized UAH, it can control the yaw motion by only adjusting speed of the driven motor. This operation manner can remove the rotor’s variable-pitch mechanism, and even the traditional AYDS. The yaw control method this paper considered is deployed in that type of helicopter

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