Ameya Godbole

ORCID Identifier(s)

0000-0002-8622-5547

Graduation Semester and Year

2019

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering

Department

Mechanical and Aerospace Engineering

First Advisor

Kamesh Subbarao

Abstract

The research focuses on the mathematical modeling and control of an unmanned aerial vehicle with cable suspended payload. A comprehensive mathematical model is derived for a quadcopter with a cable suspended payload using the Newton-Euler method and the Euler-Lagrange formulation. These methods assume that the cable is massless and always taut and cannot be used to simulate the cases when the cable is flexible. Hence, an alternative approach to model the flexibility of the cable is presented using Lagrangian mechanics by approximating the cable to be a chain of serially connected links. The motion of the payload induces disturbances on the aerial platform and must be mitigated for stable operation. The solution to this control problem is presented through the implementation of a passivity based controller, and an extended state observer based active disturbance rejection controller. The implementation of the passivity based controller requires the knowledge of time derivatives of the payload oscillations. Assuming only the swing angles of the payload with respect to the unmanned aerial vehicle are measured, these states (primarily the angular velocity) are estimated using a continuous-discrete Kalman Filter. Alternately, since the payload cable swing angles are difficult to measure or requires additional on-board sensors, an active disturbance rejection controller is designed and implemented wherein the disturbances induced in the system due to the motion of the payload are estimated using the extended state observer. A comparison between the passivity based controller and the extended state observer based active disturbance rejection controller is performed using a high fidelity numerical simulation. The simulation results are verified experimentally using a quadcopter platform in the Aerospace Systems Laboratory at The University of Texas at Arlington. Furthermore, the mathematical modeling of a multi-agent system consisting of multiple quadcopters connected to a rigid body payload via cables is presented. A distributed extended state observer based active disturbance rejection controller is implemented on this system to achieve the cooperative control task of safely transporting the payload while attenuating the swing of the payload.

Keywords

Multi-copter, Extended state observer, Active disturbance rejection control, Distributed cooperative control, Unmanned aerial vehicles

Disciplines

Aerospace Engineering | Engineering | Mechanical Engineering

Comments

Degree granted by The University of Texas at Arlington

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