Design and realization of a tilting mechanism
Prasetyo, Agustinus Benyamin
Date of Issue2016-05-13
School of Mechanical and Aerospace Engineering
Unmanned Aerial Vehicle (UAV) has received a growing attention for the last few years. In terms of cost effectiveness and power efficiency, tricopter is better than other Vertical Take-Off and Landing (VTOL) vehicles. However, tricopter control and stability is more challenging compared to even numbers configuration such as quadcopter. Since it has odd number of propellers, tricopter utilizes tilting mechanism for yaw rotation. Main focus of this research will be about tilting mechanism and yaw rotation. Servomotor is normally used to control tilting mechanism because it is precise and strong. Communication and logic over servomotor can be controlled via Arduino or Pixhawk. Both Arduino and Pixhawk can be controlled from a distant via Xbee and receiver, respectively. Pixhawk is more favored for the control experiment because of its convenience and wider features compared to Arduino. Control design can be created in Simulink with additional blocks and compiler from Simulink-Pixhawk PX4 Embedded Coder which can be found in Mathworks (Pilot Engineering Group, 2015). Result from the first step of experiments is analyzed to generate parameter value for the system. Mathematical model of a system dynamics can be built in Simulink with the gathered parameter value to predict future behavior and to save future experiment time. If there are any dissimilarities between actual result and mathematical model characteristics, the mathematical model needs to be refined. The control used for this experiment is Proportional-Integral-Derivative (PID). PID is one of the most reliable and simple control mechanism (National Instruments, 2011). However, the downside of PID is the value often comes from trial and error. In addition to that, Simulink-Pixhawk PX4 Embedded Coder takes more than 5 minutes to successfully embed the code into the board. Thus, the mathematical model helps to cut a lot of experiment time in the future. All the systems tested on this experiment is mounted to the ground to avoid injuries for the researchers or to the UAV. To achieve this, Twin Rotor Multi Input-Multi Output (TRMS) system is developed for early control testing. Mounting for general UAVs is also developed to test control design of any UAV. UAV mounting constraints translational movement of a UAV and reduce the desgree-of-freedom into 3 for rotational movement. This research focus on the tilting mechanism which ultimately result in yaw moment. Through this experiment, the mathematical model for TRMS is created and tested. The mathematical model is reliable and it can explain most of general behavior of system’s yaw. From the understanding of dynamics in TRMS, especially about the significant value of static friction coefficient, tricopter yaw control is developed. Control for tricopter is still in the unreliable stage and can be continued for further research.
Final Year Project (FYP)
Nanyang Technological University