Variable sampling time discrete sliding mode control for a flapping wing micro air vehicle using flapping frequency as the control input

Abstract

In this article, two main assumptions commonly used in the reported literature are relaxed. First, instead of a continuous time controller, a discrete time controller is proposed. Second, the controller uses the flapping frequency as opposed to flapping force/moments as the control input commonly assumed by other research groups. A discrete time controller is more suitable for implementation and deployment to most real flapping wing micro aerial vehicles (FWMAVs), in which a computer controls a sampled system and the flapping wings are driven by servomotors. A robust reaching law based on the discrete sliding mode control method is proposed to stabilize the vertical altitude of a simulated FWMAV. The continuous time model of the FWMAV is converted to a discrete time model, and the discrete time sliding mode controller is developed for the new form of the model. Using the variable sampling time, the robust discrete sliding mode controller developed in this article is able to control a simulated FWMAV to successfully stabilize its position in spite of a 16% difference in model parameters, as well as a 0.7 m/s wind gust. The controller was able to withstand the wind gust with negligible deviation from its desired position. These simulation results further show an input frequency range similar to that of the experimentally derived model previously reported in the literature.

Keywords

• flapping wing
• air vehicle
• discrete sliding model control
• flapping frequency