Thrust Control Loop Design for Electric-Powered UAV

  • Heejae Byun
  • Sanghyuk Park
Original Paper


This paper describes a process of designing a thrust control loop for an electric-powered fixed-wing unmanned aerial vehicle equipped with a propeller and a motor. In particular, the modeling method of the thrust system for thrust control is described in detail and the propeller thrust and torque force are modeled using blade element theory. A relation between current and torque of the motor is obtained using an experimental setup. Another relation between current, voltage and angular velocity is also obtained. The electric motor and the propeller dynamics are combined to model the thrust dynamics. The associated trim and linearization equations are derived. Then, the thrust dynamics are coupled with the flight dynamics to allow a proper design for the thrust loop in the flight control. The proposed method is validated by an application to a testbed UAV through simulations and flight test.


Electric-powered aircraft Thrust modeling Thrust control Unmanned aerial vehicle 

List of Symbols

\(\alpha \)

Angle of attack [rad]

\(\beta \)

Propeller twist angle [rad]

\(D_\mathrm{prop} \)

Propeller diameter [m]


Propeller elemental lift [N]


Propeller elemental drag [N]


Current [A]

\(i_0 \)

No-load current [A]

\(I_\mathrm{rotor} \)

Rotor inertia

\(I_\mathrm{prop} \)

Propeller inertia


Advance ratio [-]

\(K_V \)

Velocity constant [(rad/s)/V]

\(K_\mathrm{bemf} \)

Back electromotive force constant [V/(rad/s)]

\(K_\mathrm{Q} \)

Torque constant [N m/A]

\(k_\mathrm{T} \)

Thrust coefficient [-]

\(k_\mathrm{Q} \)

Torque coefficient [-]

\(a_\mathrm{T} \)

Second order coefficient of approximated thrust coefficient

\(b_\mathrm{T} \)

First order coefficient of approximated thrust coefficient

\(c_\mathrm{T} \)

Zero order coefficient of approximated thrust coefficient

\(a_\mathrm{Q} \)

Second order coefficient of approximated torque coefficient

\(b_\mathrm{Q} \)

First order coefficient of approximated torque coefficient

\(c_\mathrm{Q} \)

Zero order coefficient of approximated torque coefficient




Revolution per second [RPS]



\(Q_\mathrm{motor} \)

Motor torque [N  m]

\(Q_\mathrm{prop} \)

Propeller torque [N  m]

\(R_\mathrm{motor} \)

Estimated motor resistance [Ohm]

\(R_\Omega \)

Measured motor resistance [Ohm]

\(\rho \)

Air density [\({m^{3}}/{kg}\) ]

\(T_\mathrm{prop} \)

Propeller thrust [N]

\(\upsilon \)

Viscous friction coefficient [N\(\cdot \)m/(rad/s)]

\(V_\infty \)

Forward air speed [m/s]

\(\omega \)

Angular velocity [rad/s]

\(\omega _\mathrm{prop} \)

Propeller angular velocity [rad/s]

\(\beta _\mathrm{gear} \)

Gear ratio

\(V_{in} \)

Input voltage [V]

\(\omega _{co} \)

Crossover frequency [rad/s]


Phase margin [\(^{\circ }\)]


Gain margin [-]

\(\theta \)

Pitch angle [rad]



This research was supported by Basic Science Research Program through the National Research Foundation of Korea (KRF) funded by the Ministry of Education (NRF-2015R1D1A1A01060574).


  1. 1.
    Rubin R (2014) Drones : Quickly Navigating toward commercial Application, Starting With E-Commerce and Retail. Report, BI Intelligence, USA, Jan. 23Google Scholar
  2. 2.
    Hickey J (2015) Integrating UAS into the U.S Airspace System : ICAO RPAS Symposium, Montreal, Canada, 23–27 Mar 2015Google Scholar
  3. 3.
    Wang CJ, Sern Yung VC (2015) Unmanned aerial vehicle development trends & technology forecast. Report, DSTA Horizons, SingaporeGoogle Scholar
  4. 4.
    Jonathan PH (2004) Aircraft stability and control. MIT Open courseware of Massachusetts Institute of Technology, Cambridge (fall)Google Scholar
  5. 5.
    Park Sanghyuk (2015) Guidance and control of flight vehicles. Graduate level lecture of Korea Aerospace University, GoyangGoogle Scholar
  6. 6.
    Yuan W, Jayakody H, Katupitiya J (2012) Dynamic modelling and analysis of a vectored thrust aerial vehicle. In: Proceedings of Australasian Conference on Robotics and Automation, Wellington, New Zealand, 3–5 Dec 2012Google Scholar
  7. 7.
    Lee Byung-Yoon, Yoo Dong-Wan, Tahk Min-jea (2013) Performance comparison of three different types of attitude control systems of the Quad-Roter UAV to perform flip maneuver. Int J Aeronaut Space Sci 14(1):58–66CrossRefGoogle Scholar
  8. 8.
    Sharf I, Nahon M, Harmat A, Khan W, Michini M, Speal N, Trentini M, Tsadok T, Wang T (2014) Ground effect experiments and model validation with Draganflyer X8 Rotorcraft. In: 2014 International Conference on Unmanned Aircraft Systems. Orlando, USA, 27 – 30 MayGoogle Scholar
  9. 9.
    Stančić I, Ljubičić A, Cecić M (2015) Identification of UAV engine parameters. Wseas Trans Syst Control 10:179–185Google Scholar
  10. 10.
    Grau JJ (2012) Testing bench design and tilting propeller system identification for the development and control of a thrust-vectoring hovercraft. Master thesis, South Dakota School of mines and Technology, USAGoogle Scholar
  11. 11.
    Podharadský M, Bone J, Coopmans C (2013) Battery model-based thrust controller for a small, low cost multirotor unmanned aerial vehicles. In : 2013 international Conference on Unmanned Aircraft Systems, Atlanta, USA, 28–31 May, 2013Google Scholar
  12. 12.
    Mathew S (2006) Wind energy fundamentals, resource analysis and economics. Springer, Berlin (ISBN-10 3-540-30905-5)Google Scholar
  13. 13.
    Brandt JB, Selig MS (2011) Propeller performance data at low Reynolds numbers. AIAA paper 2011-1255, January 2011Google Scholar
  14. 14.
    Kenjo TAK (1991) Electric motors and their controls. Oxford University Press, New YorkGoogle Scholar
  15. 15.
    Hanselman Duane(2003) Brushless permanent magnet motor design 2\(^{nd}\) edition. Writers’ Collective, Ohio (ISBN : 1-932133-63-1)Google Scholar
  16. 16.
    Jr Hendershot JR, Miller THE (1994) Design of Brushless permanent-magnet motors. Oxford university press, New York (ISBN : 1-881855-03-1)Google Scholar

Copyright information

© The Korean Society for Aeronautical & Space Sciences and Springer Nature Singapore Pte Ltd. 2018

Authors and Affiliations

  1. 1.Korea Aerospace UniversityGoyangRepublic of Korea

Personalised recommendations