Experimental design for attitude control of a 3-DOF helicopter based on the fully actuated system approach

The three-degree-of-freedom (3-DOF) helicopter exhibits inherent underactuation, strong nonlinearity, and dynamic coupling, posing considerable challenges to attitude control design in terms of global stability, disturbance rejection, and rapid convergence.

To address these issues, a prescribed-time attitude control strategy based on the fully actuated system approach is developed for the 3-DOF helicopter. A fully actuated mathematical model is first established by introducing virtual control variables. Through this transformation, the original underactuated dynamics are equivalently converted into a fully actuated system representation, providing a unified foundation for controller synthesis. On this basis, a prescribed-time controller is designed to ensure that the attitude tracking errors converge to the equilibrium within a predefined time bound, independent of initial conditions. To enhance robustness against external disturbances and modeling uncertainties, a structured disturbance observer is incorporated into the control framework, and the estimated disturbances are compensated through a feedforward mechanism.

Simulation results indicate that the prescribed-time controller achieves faster convergence than the proportional-derivative (PD) controller in both elevation and yaw tracking. Convergence is completed within approximately 5 s and 4 s under the proposed method, whereas the PD controller requires approximately 18 s and 10 s, respectively, with noticeable steady-state error. Experimental results show that stable regulation is achieved within approximately 8 s during the rising phase and 2 s during the falling phase, whereas the PD controller converges more slowly and exhibits more pronounced overshoot. These results demonstrate the superior dynamic and transient performance of the proposed method.

A prescribed-time control strategy based on the fully actuated system approach is successfully applied to the attitude control of a 3-DOF helicopter. Rapid convergence within a predefined time is guaranteed, and robustness against disturbances is effectively enhanced. Moreover, the experimental platform enables intuitive demonstration of helicopter attitude control for automation engineering education, promoting the integration of theoretical control methods with practical engineering applications and strengthening the capacity to address complex engineering problems.