Title:  Design Analysis of a Drone Mechanism with 3-axis of Rotation

by Varun Mathur and Raymond K. Yee

San Jose State University, CA

 

Abstract

  
A quadcopter is an Unmanned Aerial Vehicle (UAV) with 4 propellers providing required force for motion. A quadrotor helicopter is a UAV that has four equally spaced rotors, typically arranged at the corners of a central body.  With four independent rotors, the need for a swashplate mechanism like that in a regular helicopter is alleviated. Due to the rotation of the propellers attached to the quadcopter an upward thrust is generated. The maneuverability of the quadcopter is primarily controlled by adjusting the speed of each propeller attached to a rotor which in turn creates different lifting forces for maneuvering. The objective of this work is to design a 2-axes rotation mechanism for the shaft while the propeller rotates about its own axis in a 1 m by 1 m quadcopter. Besides the spinning of the propeller axis, the two other perpendicular axes in the mechanism are capable of rotating in a flight which dynamically modifies the thrust vector direction and enhances the quadcopter’s maneuverability.   
The project was accomplished by performing several key tasks involving mechanism design using bevel gears, shafts and motors, computational fluid dynamic analysis to determine aerodynamic thrusts and airflow pattern, rigid body dynamic analysis to evaluate forces and torques at different sections of the mechanism, and finite element analysis of mechanical components to optimize the stresses and fatigue as well as their corresponding safety factors.   
The final mechanism design provides mobility similar to a spherical joint capable of rotating from -45 degrees to 45 degrees along 2 orthogonal axes for a small size drone. The results of rigid body dynamics for a small size drone indicate that the required motor torque is about 0.5 N-m, based on using 40-mm driving nylon gear size with gear ratio 1:2 and aluminum shaft with its propeller rotating at 2000 rad/sec, the nylon gear is good for 10 million cycles, and the shaft’s fatigue life is close to 1 billion cycles.  Further study would be required in developing the control system for this quadcopter design and optimizing the entire structure of the drone, prototype verification of the mechanism design on flight maneuverability is also recommended.  A parallel study using layered composite design is currently undertaken. A comparison between metal and fiber composite shafts on weight reduction and performance of the mechanism would be made.


Design and Analysis of a Drone Mechanism With 3-Axis of Rotation

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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