IEEE/ASME TRANSACTIONS ON MECHATRONICS, VOL. 12, NO. 5, OCTOBER 2007 565 Development of a Cyclogyro-Based Flying Robot With Variable Attack Angle Mechanisms Kazuo Tanaka, Ryohei Suzuki, Takanori Emaru,Yoshiyuki Higashi, and Hua O. Wang Abstract—This paper presents an experimental study on the develop- ment of a cyclogyro-based flying robot with a new variable angle of attack mechanism. A cyclogyro is a flying machine supported in the air by power- driven rotors that rotate about a horizontal axis, like the paddle-wheels of a steamboat. Machines of this type have been designed by some companies but there has been no record of any successful flights. Our design starts with a new variable angle of attack mechanism with an eccentric (rota- tional) point in addition to a rotational point connecting to a motor. The main feature of the mechanism with the eccentric rotational point is the ability to change attack of angles in accordance with the wing positions (as determined by the rotational angles of the cyclogyro) without actuators. The design parameters (wing span, the number of wings, and eccentric dis- tance) of the flying robot are determined through a series of experiments. Experimental results show that the cyclogyro-based flying robot with the new variable angle of attack mechanism is capable of generating sufficient lift force for flying. Index Terms—Cyclogyro, eccentric point, flying robot, variable attack angle mechanism. I. INTRODUCTION In parallel with studies on manipulator-type robots, there has been decades of research on mobile robots. Starting in the late 1960s, wheeled or legged mobile robots were the subject of worldwide re- search efforts. From the 1970s through the 1990s, research and de- velopment activities for mobile robots have been steadily increasing. Recent years have witnessed a significant surge in mobile robot research as reflected by the large number of publications [1]–[5]. In particular, with the renewed interest in unmanned aerial vehicles, the number of studies on flying robots has also been on the rise. For the purpose of this paper, flying robots refer to heavier-than-air flying machines. Therefore, lighter-than-air (blimp) platforms utiliz- ing lift forces generated from helium gas [6], [7] are not considered. Flying robots so defined typically feature complex and nonlinear dy- namics. The development and control of flying robots are challenging problems in robotics research. An interesting class of flying robots is the micro air vehicle- (MAV) [8]. In particular, the Defense Advanced Research Projects Agency (DARPA) project [9], [10] on MAVs is well known. Most of the MAV research activities involves the conventional fixed-wing airplane or helicopter type of vehicles. For instance, model identification of an airplane-type MAV was studied in [11], and several ARX models were obtained by system identification techniques. With respect to mechanism of generating lift forces, a unique mech- anism, named the cyclogyro, was proposed in the 1930s. An airplane with the mechanism was conceived and designed at the time. Fig. 1 shows a drawing of a cyclogyro-based airplane planned in the 1930s. The cyclogyro (or cyclogyre)-based airplane is lifted and propelled by horizontal assemblies of rotating wings. According to [12], very few Manuscript received May 4, 2006; revised January 8, 2007. Recommended by Technical Editor C. Mavroidis. K. Tanaka, R. Suzuki, T. Emaru, and Y. Higashi are with the Depart- ment of Mechanical Systems and Intelligent Systems, University of Electro- Communications, Tokyo 182-8585, Japan (e-mail: ktanaka@mce.uec.ac.jp; ryohei@rc.mce.uec.ac.jp; emaru@rc.mce.uec.ac.jp; y.higashi@rc.mce.uec. ac.jp). H. O. Wang is with the Department of Aerospace and Mechanical Engineer- ing, Boston University, Boston, MA 02215 USA (e-mail: wangh@bu.edu). Digital Object Identifier 10.1109/TMECH.2007.905720 Fig. 1. Drawing of a cyclogyro-based airplane planned in the 1930s. prototypes were ever built, and those constructed were completely un- successful. The essential principle of the cyclogyro is that the angle of attack of the rotating wings should be varied as they go a round, al- lowing the lift/thrust vector to be altered, which would, in turn, enable a cyclogyro-based airplane to rise vertically, hover, and even go back- wards. Thus, a cyclogyro-based flying robot has the potential of being a highly maneuverable MAV. The maneuverable merits of cyclogyro- based flying robots will be summarized in Section II. To the best of our knowledge, there has been no reported effective and practical mech- anism of varying angles of attack in the context of cyclogyro-based flying robots. There has been no record of any successful flights though prototypes have been developed by some companies. The most important aspect of this paper is that we propose a new variable angle of attack mechanism that is simple and effective. In addi- tion, we demonstrate that a cyclogyro-based flying robot with the new variable angle of attack mechanism can hover along a vertical guide. So far, as this robot does not have any controller to stabilize its body, a vertical guide to assist its flight becomes necessary. Nevertheless, this encouraging result demonstrates the feasibility of cyclogyro-based flying in that the robot can generate sufficient lift force to fly, i.e., to overcome its own weight. The focus of this paper is on the experimental study on a cyclogyro- based flying robots. As such, we have carried out several rounds of build and test development cycles to study the effects of design parameters. Even with a relatively small number of builds and tests, we are able to demonstrate the feasibility of cyclogyro-based flying robots. Theoret- ical and numerical studies are ongoing to understand the experiments and further the development effort. II. NEW V ARIABLE A TTACK ANGLE MECHANISM The key feature of the developed variable angle of attack mechanism [13]–[15] in a cyclogyro-based flying robot is to have an eccentric (rotational) point in addition to a rotational point connecting to a motor. This allows attack of angles to vary quickly according to the wing positions (as determined by the rotational angles of the cyclogyro) without actuators. Fig. 2 shows the flying robot prototype developed in this research. The flying robot has two sets of cyclogyro wings rotated by two motors. The airfoil is NACA0012. Figs. 3 and 4 show the outline of cyclogyro-based wings with/without the new variable attack angle mechanism, respectively. As shown in Fig. 3, for the cyclogyro-based wings without the new variable angle of attack mechanism, the lift and drag forces generated by all the wings are canceled due to the symmetry of the attack of angle. One way of overcoming the difficulty is to change the angle of attack according to the wing positions, that is, the rotational angle θ. As mentioned before, some ideas have been proposed, but there has no record of any successful flights.