Terminal sliding mode control for aeroelastic systems

An aeroelastic system is a nonlinear system with two freedoms, i.e., the plunge displacement and the pitch angle, in a dynamic system model. A chaos effect or a limit cycle oscillation is presumably attributed to the nonlinear effect of the pitch angle mentioned above or the interaction between the aerodynamic behaviors. It is that a single trailing edge input in an aeroelastic system is employed as a way to suppress the limit cycle oscillation with an exclusive choice between the plunge displacement and the pitch angle for a control law design. Consequently, the remaining inevitably turns into an internal dynamics, whose stability is adversely affected by the flight speed and structure parameters, a problem improved by no means using a singe control input design. Toward this end, this work presents a controller design criterion with multiple input channels for both the leading and training edges to remove the uncertainty effect of internal dynamics, and render more room for the response design of the plunge displacement as well as the pitch angle. Mostly due to external disturbance and unknown uncertainty, there is a deviation between the intended and implemented system performances for a robust control design, a mainstream research issue in the modern control. As a consequence of a sliding mode control utilized here, the limit cycle oscillation suffered in an aeroelastic system is removed effectively by the use of a terminal sliding mode control, and the chattering phenomenon seen in the control signal is hence eliminated by his method. It is seen from simulations that the control system is stably assured to reach the target within a limited time frame with an addition of a saturation function to the control law.