Design and fabrication of an autonomous Octorotor flying robot

In this paper, the full procedure of the mechanical design and electronic subsystems of a new Octorotor flying robot is discussed. The number of motors from four motors is increased to eight motors which all of motors set as coaxial and they are installed two by two. It means that four motors are placed on top of the robot and another four motors are placed on down of the robot coaxially. This structure can be use for carrying more pay load. In addition, there are many factors in control of a flying robot which its motion affects from eight motors. In fact, the main factor of flying robot motion is done by these brushless DC motors which achieves to the desired area. Also, IMU works as a stabilizer in the motion control system. Since the robot needs more flight time, it should have light-weight and official materials such as fiber carbon. It should be note that the equal distance is considered between the shaft centers of the motors in Octorotor. Also, the movement control system of Octorotor is supplied by the designed PID controller which will be discussed.

I. Introduction

IN the last years, multirotors are a challenge research problem [1] which has become prevalent by researchers as in [2]–[5]. Multirotors are robust and simple helicopters while they do not have the complicated swashplates and linkages found in conventional rotorcraft [6]. The main restrictions on the use of helicopters caused the human to use flying robots which have low weight and less cost and more secure flights. In this regard, Unmanned Aerial Vehicles (UAVs) are being used more often for military and civilian purposes such as traffic monitoring, patrolling for forest fires, surveillance, landslide and rescue, in which risks to pilots are often high. Military applications currently represent the lion's part of the unmanned flying vehicle market, and this industrial sector is growing strongly. UAV can also be used in indoor and outdoor applications. Here, one kind of UAVs that can be used in all the applications is Quadrotor. Quadrotors are placed in Micro Aerial Vehicle (MAVs) families. MAVs can be operated on wide area regardless of the effect of ground configuration. An X4-Rotor UAV has been conceived by a team from the Australian National University [7] to be used as a highly-reliable experimental platform. The merit of MAVs is maximized for the practical use in the places where it is dangerous and difficult to approach. Furthermore, MAVs are much cheaper and safer in dangerous tasks than piloted aircrafts. Attempts to build fully-operational and open-source Quadrotor at a moderate cost can be found in [8]–[9]. Other experimental flying platforms with vertical takeoff and landing capabilities are studied in [10]–[11]. The full design of an UAV quadrotor as a platform for monitoring indoor environments is also reported in [12]. If the small size is considered, the best choice among UAVs is multi-rotors. Coaxial Quadrotor is an Octorotor that uses four arms, with motors arranged coaxially placed up and down. Certainly, when the number of motors in MAVs is increased, this configuration is expected to makes the vehicle generates more thrust. Also, the number of the rotating propeller is expected to give more stability, since the coaxial configuration cancels the torque one another. So, this fact results in the robot can carry more payload than 1 kg which consists of camera or other manipulated object. As similar to the Quadrotor, Octorotor is an under-actuated system with six degrees of freedom and (three translational and three rotational) and only four independent inputs (rotor speeds) and six outputs which are highly coupled.