Skip to Main Content
 

Global Search Box

 
 
 
 

ETD Abstract Container

Abstract Header

Harmonic disturbance rejection in feedback linearization control of a two degrees of freedom helicopter

Zarikian, Garo

Abstract Details

2004, Master of Science, Ohio State University, Electrical and Computer Engineering.
In this Masters degree thesis work, we tackle the problem of controlling the attitude of a small aerospace vehicle represented by a 2DOF (Degrees Of Freedom) helicopter subject to external harmonic disturbances at the level of the plant input and the velocity sensors. The thesis starts with deriving a mathematical model of the helicopter dynamics using Euler formalism. This is followed by system identification in order to identify or estimate the unknown system parameters. The method we use is based on the conservation of total energy which states that the work of forces applied to the system equals its total energy. A model linear in the parameters is derived and the Least Squares method is used to identify the parameters of the system. The next part of the thesis is the controller design. To regulate the attitude of the helicopter, we design an inner-loop controller based on feedback linearization. This controller is completed by a linear outer loop controller, designed using Linear Quadratic Regulator (LQR). We consider the case of tracking an arbitrary reference trajectory generated by a joystick which is supplied with the plant. Then, we con¬sider the design of the controller when the plant is subject to harmonic disturbances. In particular, we consider three cases: In the first case, we assume that a sum of harmonic signals of different frequencies, amplitudes and phases perturb the velocity sensors of the plant. We assume that the disturbance characteristics are all unknown, but lie within a certain known bound. The method we use to reject the disturbance is via a device that is placed outside the feedback loop of the original controller, which will construct the disturbance and allow its cancellation. The idea is to design a controller that achieves stabilization and tracking first, and then augment the controller with a mechanism that reconstructs and cancels the disturbance at the sensor level. Since the device in question is placed outside the main stabilizing feedback loop, it is referred to as an external model of the disturbance. The estimation of the unknown frequencies of the disturbance is done by an adaptive update law which proves its effectiveness. In the second case, we assume that the harmonic signals perturb the input of the plant. The method we use to reject this disturbance is also via an external model, but with a slight modification. Here, we assume that the frequencies of the disturbance are known but their amplitudes and phases are unknown. The third and final case is that of assuming both velocity sensors and plant input being perturbed by harmonic disturbances. As expected, there will be two external models, one for each disturbance. The duty of the external model of the velocity sensor will be to estimate the frequencies of the disturbance, cancel it at the sensors level and feed the input external model with the frequency estimates. The input external model, receiving those estimates will cancel its disturbance so that the plant can track any desired trajectory regardless of all those disturbances. We provide a large number of experimental results showing the effectiveness and robustness of the method even when changing the unknown characteristics of the disturbance (such as frequency, amplitude and phase) in real time.
Andrea Serrani (Advisor)
Stephen Yurkovich (Committee Member)
127 p.

Recommended Citations

Citations

  • Zarikian, G. (2004). Harmonic disturbance rejection in feedback linearization control of a two degrees of freedom helicopter [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1413476261

    APA Style (7th edition)

  • Zarikian, Garo. Harmonic disturbance rejection in feedback linearization control of a two degrees of freedom helicopter. 2004. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1413476261.

    MLA Style (8th edition)

  • Zarikian, Garo. "Harmonic disturbance rejection in feedback linearization control of a two degrees of freedom helicopter." Master's thesis, Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1413476261

    Chicago Manual of Style (17th edition)