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Non-Linear Control of a Tilt-Rotor Quadcopter using Sliding Mode Technique

Sridhar, Siddharth
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1592170442729443

Abstract Details

2020, PhD, University of Cincinnati, Engineering and Applied Science: Aerospace Engineering.
This research provides insights on the tilt-rotor quadcopter (TRQ) being a fully actuated system. The tilt-rotor quadcopters are a novel class of quadcopters with the capability of rotating each arm/rotor of the quadcopter to an angle using a servo motor. With the additional servo control inputs, the tilt-rotor quadcopters are fully actuated systems and hence can even hover with a non-zero attitude. Also, this type of a quadcopter can handle external disturbances better than a conventional quadcopter and is fault tolerant. The objective of this dissertation was to design a novel non-linear controller using sliding mode technique that enabled the TRQ to reach desired waypoints, perform robustly under wind disturbances and faults, and hold a commanded attitude and position simultaneously. Four different variants of the tilt rotor quadcopter, namely, TRQ v1, TRQ v2, TCop and TRQ v1H, are studied, and different non-linear control designs using sliding mode technique for each vehicle are presented. Firstly, in this study, the sliding mode control technique is utilized for the pitch, roll and yaw motions for the TRQ v1 while an independent PD controller provides the tilt angles to the servo motors. The dynamic model of the TRQ is presented, based on which sliding surfaces were designed to minimize the tracking errors. Using the control inputs derived from these sliding surfaces, the state variables converge to their desired values in finite-time. Further, the non-linear sliding surface coefficients are obtained by Hurwitz stability analysis. Numerical simulation results are presented that demonstrate the performance and robustness against disturbances using this proposed sliding mode control technique. Secondly, this dissertation studies the fault-tolerant behavior of tilt-rotor platforms. To achieve fault tolerance, the tilt-rotor quadcopter v2 transforms into a T-copter (TCop) design upon motor failure thereby abetting the UAV to cope up with the instabilities experienced in yaw, pitch and roll axes and still completing the flight mission. The dynamics of the TCop, a sliding mode flight controller and the derivation of the switching surface coefficients for this reconfigurable system, along with the numerical simulation results during motor failure are presented. Thirdly, the dynamics of the TRQ derived based on hardware developed in the laboratory, TRQ v1H is presented along with a smart sliding mode controller that helps the TRQ to hover with a non-zero attitude. Computational Fluid Dynamic (CFD) simulations were performed on a CAD model of the tilt-rotor quadcopter to obtain real time drag forces for various wind velocities. The robustness of the sliding mode controller is demonstrated under various wind disturbance scenarios while the quadcopter hovers at a non-zero attitude through numerical simulations. The robustness of the sliding mode controller is also shown with faulty motors. Benchmarked results against a PID controller on the TRQ, SMC and PID controllers on conventional quadcopter are also presented. Lastly, the hardware implementation of the designed sliding mode controller on the TRQ was explored. The design of the controller using SIMULINK and implementation of the same on a Pixhawk 2 flight controller with preliminary experimental tuning results have been presented.
Manish Kumar, Ph.D. (Committee Chair)
Shaaban Abdallah, Ph.D. (Committee Member)
Kelly Cohen, Ph.D. (Committee Member)
George T. Black, M.S. (Committee Member)
115 p.
Aerospace Materials
Sliding Mode Control; Tilt-Rotor Quadcopter; UAV; Non-Linear Control

Recommended Citations

Citations

  • Sridhar, S. (2020). Non-Linear Control of a Tilt-Rotor Quadcopter using Sliding Mode Technique [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1592170442729443

    APA Style (7th edition)

  • Sridhar, Siddharth. Non-Linear Control of a Tilt-Rotor Quadcopter using Sliding Mode Technique. 2020. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1592170442729443.

    MLA Style (8th edition)

  • Sridhar, Siddharth. "Non-Linear Control of a Tilt-Rotor Quadcopter using Sliding Mode Technique." Doctoral dissertation, University of Cincinnati, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1592170442729443

    Chicago Manual of Style (17th edition)

ucin1592170442729443
178
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This open access ETD is published by University of Cincinnati and OhioLINK.