Robust Fault Estimation Using the Intermediate Observer: Application to the Quadcopter.

Ngoc Phi Nguyen,Xuan Phu Do,Tuan Tu Huynh,Sung Kyung Hong,Nguyen Xuan Mung

doi:10.3390/s20174917

Abstract

In this paper, an actuator fault estimation technique is proposed for quadcopters under uncertainties. In previous studies, matching conditions were required for the observer design, but they were found to be complex for solving linear matrix inequalities (LMIs). To overcome these limitations, in this study, an improved intermediate estimator algorithm was applied to the quadcopter model, which can be used to estimate actuator faults and system states. The system stability was validated using Lyapunov theory. It was shown that system errors are uniformly ultimately bounded. To increase the accuracy of the proposed fault estimation algorithm, a magnitude order balance method was applied. Experiments were verified with four scenarios to show the effectiveness of the proposed algorithm. Two first scenarios were compared to show the effectiveness of the magnitude order balance method. The remaining scenarios were described to test the reliability of the presented method in the presence of multiple actuator faults. Different from previous studies on observer-based fault estimation, this proposal not only can estimate the fault magnitude of the roll, pitch, yaw, and thrust channel, but also can estimate the loss of control effectiveness of each actuator under uncertainties.

Highlights

Unmanned aerial vehicles (UAVs) have attracted attention over many years owing to their vital achievements and significant advantages in various applications, such as rescue [1,2], coastal surveillance [3,4], forest monitoring [5,6], military, defense [7,8], and robust control with uncertainties [9,10,11]
Faults with different magnitudes were injected into three actuators at time t = 68.5 s by 20% loss of control effectiveness (LoCE) in the third motor
After faults occur in the third motor, the PID controller can recover the system by increasing the Pulse width modulation (PWM) input of the desired position third actuator

Summary

Introduction

Unmanned aerial vehicles (UAVs) have attracted attention over many years owing to their vital achievements and significant advantages in various applications, such as rescue [1,2], coastal surveillance [3,4], forest monitoring [5,6], military, defense [7,8], and robust control with uncertainties [9,10,11]. In comparison with manned aerial vehicles, the control of UAVs is more complex since all tasks are operated autonomously through an embedded flight controller or by a pilot. Quadcopter, a type of UAV system, has been used and developed for various applications owing to its numerous advantages, such as simplicity, small size, indoor and outdoor operation, and agility, which have rendered it more famous than other types of UAV systems. An FTC can be Sensors 2020, 20, 4917; doi:10.3390/s20174917 www.mdpi.com/journal/sensors

Methods

Results

Conclusion