|Lovely Son||Structural Dynamic Laboratory, Mechanical Engineering Department, Universitas Andalas, Padang 25163, West Sumatera, Indonesia|
|Kevin Eldyf Adipta||Structural Dynamic Laboratory, Mechanical Engineering Department, Universitas Andalas, Padang 25163, West Sumatera, Indonesia|
|Mulyadi Bur||Structural Dynamic Laboratory, Mechanical Engineering Department, Universitas Andalas, Padang 25163, West Sumatera, Indonesia|
A landing gear model using a four-bar linkage mechanism is proposed in this study. The simulation study was conducted to evaluate the effect of the link dimension variation and coil spring constant on the equivalent stiffness and static deflection of the landing gear. The simulation results show that increasing the landing gear dimension affects the static deflection of the landing gear. However, the linear stiffness of the landing gear system is not much affected by the landing gear dimension variation. Furthermore, the landing gear stiffness characteristic is nonlinear for large landing gear displacement.
Dynamic; Impact; Landing gear; Simulation; Vibration
Unmanned aerial vehicles (UAVs), also known as drones, are pilotless aircraft controlled remotely using a computer or radio controller (RC). They are created with various sizes, designs, and purposes and can fly autonomously using a pre-flight path planning program (Yao et al., 2015; Yang et al., 2016; Sutresman et al., 2017). Given their sophistication and technological ease, UAVs are widely used in areas such as monitoring, mapping, search and rescue operations, goods shipping, civil infrastructure inspection, and military weapons (Jha, 2009; Sung, 2014).
One of the most important components in UAVs is the landing gear system. Generally, a landing gear system consists of shock absorbers, steering, a shimmy control, wheels, and brakes (Prasad & Gangadharan, 2015). The landing gear system is used to hold the UAV load during parking and taxiing (Bahkali, 2013) as well as to reduce the force transmission and acceleration of a UAV body during landing. Furthermore, it must keep the UAV wheel in contact with the ground for steering stability. These important features should be considered in designing an optimum UAV landing gear system.
Different types and characteristics of UAV landing gear systems depend on a number of factors, including UAV weight, stiffness, and vibration characteristics. Several studies have been conducted to evaluate UAV landing gear system performance in reducing impact-induced vibration during landing. An interesting feature is landing gear stability during braking and maneuvering on the ground, which can be improved by using longer axles, stiffer springs, a smaller wheel mass, and lower aircraft landing speeds (Sadrey, 2012).
Although high stiffness in the landing gear system is very necessary for aircraft stability, this condition also has the side effect of increasing the shock force transmission to the UAV structure during landing. This large shock load increases UAV acceleration response and causes damage to the electronic components inside the UAV body (Mikulowski, 2008; Son et al., 2018).
Effective shock isolation performance in a landing gear system is normally achieved by increasing the energy storage capacity of the landing gear elastic element; however, the significant energy storage requires large deformations of the landing gear, and space is normally limited. In addition, the landing gear structure must be able to dissipate the impact energy to reduce residual vibrations. An alternative method to reduce vibration response is to increase the structural damping using fiber reinforced materials (Murali et al., 2014). Active vibration control methods have proposed by researchers to attenuate vibration response occurred in mechanical systems. Mohebbi and Hashemi (2016) proposed an active vibration control technique for reducing the vibration response of an unbalanced rotary engine. In his study, the unbalanced rotary engine was modeled by a one-degree of freedom vibration system. The application of the active vibration control to a two-degree of freedom unbalanced engine model was also proposed by Mohebbi and Hashemi (2017).
Shock vibration isolation systems with nonlinear elements have been used by several researchers to improve shock isolation performance. Snowdon (1963) was one of the first to investigate the shock isolation characteristics of nonlinear elements. Much later, Carrella et al. (2008) proposed a high-static and low-dynamic stiffness isolator using a combination of linear springs. Meanwhile, Son et al. (2019) have found that the stiffness nonlinearities could be advantageous in reducing impact induced vibration in terms of rebound displacement and acceleration response in comparison with linear elastic elements.
In this study, the static analysis of a landing gear system based on a four-bar linkage mechanism is performed. The simulation study was conducted to evaluate the effects of spring stiffness and the landing gear dimension variation on the nonlinear characteristic and the static deflection of the landing gear system.
A new model for a UAV landing gear system using a four-bar linkage mechanism has been proposed here, and static analysis was conducted to evaluate the stiffness characteristic and static deflection of the landing gear. Several conclusions were obtained as follows: (1) The stiffness characteristic of the four-bar linkage mechanism landing gear system is nonlinear; (2) The nonlinear behavior of the landing gear system with a high-static stiffness and low-dynamic stiffness characteristic can improve the dynamic response of the landing gear; (3) Increasing the landing gear dimension does not much affect the linear stiffness. However, it can increase the static displacement of the landing gear.
This research is partly funded by the Faculty of Engineering, Andalas University. The researcher gives thanks for the financial support provided to develop this project.
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