A Novel Quadcopter with A Tilting Frame using Parallel Link Mechanism

This paper is concerned with a novel quadcopter with a tilting capability using a parallel link mechanism. The proposed quadcopter consists of the tilting frame and a main body, and an angle between them is called a tilt angle. A ratio of the current width to the maximum one of the quadcopter is called a folding ratio. Using only one servo motor, it can tilt in the pitch direction and be folded vertically within a user-specified ranges of the tilt angle and the folding ratio, respectively. We show a procedure of determining design parameters of the tilting frame to satisfy specifications given by the user. Due to the tilting mechanism of the frame, the proposed quadcopter is not well-controlled as the tilt angle approaches +/-pi/2. Therefore, we focus on a stabilization problem of the quadcopter at a desired tilt angle specified by a user around +/-pi/2 and propose a novel reference tilt angle generator based on the pitch angle. In simulations, we show an effectiveness of the proposed strategy for the reference tilt angle by comparing it with a conventional PID controller under the existence of a disturbance.