Disturbance Rejection for an Unmanned Rotary Aircraft System Using Strain Sensing

This paper presents a bioinspired approach for fast reaction to external disturbances as applied to small unmanned aerial systems platforms. A disturbance rejection method for a quadrotor vehicle is proposed by means of force-adaptive feedback using strain measurements. These strain measurements provide a reactive mechanism to counteract atmospheric disturbances acting on the vehicle. The reactive response from force-sensitive strain measurements is initiated before the disturbance propagates to lower-order pose and velocity states, while simultaneously reducing the latency in the feedback. These measurements are provided by means of strain gauges attached to the quadrotor arms. The location and feedback gain of the strain gauges were determined based on expected forces and moments as well as regions of high strain. The airframe section that hosted the strain sensors was manufactured and designed for a balance between structural stability and force sensitivity. The response of the quadrotor system was characterized using an induced disturbance to simulate a vertical gust. This heave perturbation was mitigated using a strain feedback controller. Improvements in gust response were demonstrated by measuring the effects of the disturbance on vehicle states.