We propose a novel quadrotor with a tilting frame using a parallel link mechanism. It consists of the tilting frame and a main body, and an angle between them is called a tilt angle. Using only one servo motor, it can tilt its frame in the pitch direction, that is, it has 5 DoF (Degrees of Freedom), so that its frame is folded vertically. However, due to the tilting mechanism of the frame, it has a singularity such that the input torque in the pitch direction equals 0 when the tilt angle is 90 or -90 degrees. Therefore, we focus on a challenging stabilization problem of the quadrotor around the singularity and propose a novel reference tilt angle generator to overcome the singularity, which will be called a RTAG. In experiments, we show that it can be stabilized around the singularity by using the proposed RTAG, and also demonstrate applications of the tilting and folding functions.

We propose a novel quadrotor with a 2-axis tilting frame using a parallelepiped mechanism. Using its parallelepiped mechanism, it has 6 DoF, that is, it can tilt its frame in the roll and the pitch direction independently by actuating only additional two servo motors. Also, it has same efficiency as the conventional quadrotor since all rotor surfaces are always kept parallel by the dual-axis tilting mechanism. Furthermore, we show a design procedure for the mechanism that achieves the given maximum folding ratio without the rotor overlapping vertically in any transformation state. In flight experiments, we confirm that it is capable of hovering at a desired position and translational motion in a desired circular trajectory with the dual-axis transformation in the roll and the pitch direction.

We propose a novel quadrotor with a 3-axis deformable frame using parallel link modules. By adding three servo motors to the frame, it has two configurations, namely, roll-pitch deformation mode and yaw deformation mode. In the roll-pitch deformation mode, it can tilt and fold the frame in the roll and pitch directions independently, which gives it 6 Degrees of Freedom (DoF). In the yaw deformation mode, it can contract the whole frame in the yaw direction. We propose a design method without thrust loss at any deformed state in both modes. In experiments, we show that it can fly stably even when deformed in both modes by the extended conventional control method. Furthermore, its applications are presented to demonstrate its high versatility. See the webpage for details.