This paper deals with the current technology status and technology development direction on shape shifting drone. A shape shifting drone is defined as a drone for which its shape and/or function of its platform in flight can be changed by shape shifting technology in order to fulfill a variety of missions effectively in harsh mission environment. A shape shifting drone can be classified as a rotary-wing based, a fixed-wing based, or a biomimetic based shape shifting drone. This work describes technology trends of domestic and foreign countries. It identifies core technologies and development direction. This work will be useful for planning research and development programs on required technology for the development of shape shifting drone in the future.
This paper proposed the simulation model of the servo system with three-stage reducer and presented the result of frequency analysis of the servo system considering backlash ratios and motor input voltage. By virtue of this work, we realized that if the motor input voltage of the system was large, the influence of each stage backlash ratio could be minimized or removed. Besides, we also found that if the motor input voltage was small, this created an optimal backlash ratio combination which could maximize the anti-resonance and resonance frequency of the servo system. This paper could be useful for determining each stage backlash ratio in designing a three-stage geared servo system with fast response.
This paper addresses two methods to estimate the target incapacitation distance and probability of the arbitrary fragmentation warhead under the static detonation test condition. One is based on the probability equation suggested by Sperrazza and Kokinakis. The other is originated from the stationary detonation test concept to measure the performance of the fragmentation warhead. In the arbitrary fragmentation warhead, the target incapacitation probabilities obtained from the two methods were compared with each other. We found that the size of the fragment with cubic shape should be more than 3.5 mm to maximize the target incapacitation distance in the test method. And we also realized that the difference between the target incapacitation distance of the analysis method based on the test (AMBT) and that of the analysis method based on the probability equation (AMBPE) is decreased according to the increase of the fragment size. In conclusion, this paper can be useful for the estimation of the fragmentation warhead performance at the design stage.
This study proposed the proper detonation delay time of a main warhead after a precursor warhead detonation in an arbitrary tandem shaped charge missile as 407 μsec. In addition, the available detonation delay time range of the main warhead was proposed to be between 396 μsec and 418 μsec. The proposed figures were based on the analysis of the target protection capability and the scattering reactor behaviors of the explosive reactive armor with dual reactive panels. By virtue of this work, the determination of main warhead detonation delay time is more effective and convenient. Finally, the tandem shaped charge missile with more effective penetration performance also could be developed in the future.
The design of subminiaturized natural fragment warhead is based on the analysis of its effectiveness against target personnel. Toward this end, the personnel incapacitation probability suggested by Sperrazza and Kokinakis was used. The effectiveness of various natural fragment warhead designs was analyzed by altering the fragment mass, velocity, number, and the target distance. A preliminary optimal design value of the natural fragment warhead in a subminiaturized missile was suggested, which was greater than the threshold value of the fragment mass to cope with air resistance. We also determined that the appropriate fragment mass was about 2.1204 × 10-4 kg (3.3 grain) in case of a subminiature warhead. This work facilitates the development of final optimal design stage of the natural fragment warhead in a subminiaturized missile and can also be utilized for the analysis and design of different types of fragment warhead.
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Analysis Method based on Probability Equation and Analysis Method based on Test in order to Estimate the Target Incapacitation Distance of Fragmentation Warhead Joo Hyun Baek, Young Hwan Jo, Byung Uk Lee, Gu Hyun Ryu Journal of the Korean Society for Precision Engineering.2020; 37(10): 751. CrossRef
Determination Method of Main Warhead Detonation Delay Time based on the Analysis about the Protection Capability of Target and the Scattering Behavior of Explosive Reactive Armor Joo Hyun Baek, Se Lin Yu, Geun Jong Jeon, Won Young Lee, Young Hwan Jo, Byung Uk Lee Journal of the Korean Society for Precision Engineering.2019; 36(10): 937. CrossRef
This paper investigated the influence of the backlash ratio on frequency response characteristic in servo systems with twostage gear reducer, according to the change of magnitude of motor input voltage. The backlash ratio is defined as the ratio of the first gear stage backlash magnitude in relation to total backlash magnitude. This paper presents that the maximum anti-resonance and resonance frequency of the system can take place at the maximum backlash ratio if the motor input voltage of the system is large. On the other hand, if the motor input voltage is small, the maximum anti-resonance and resonance frequency of the system will occur at an arbitrary backlash ratio. In order to develop the geared servo system with fast response, it is effective to increase the maximum allowable motor input voltage and to reduce the magnitude of backlash on the second gear reduction stage.
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Frequency Analysis of the Servo System with Three-Stage Reducer considering the Backlash Ratios and Motor Input Voltage Joo Hyun Baek, Tae Young Chun, Jong Geun Jeon, Young Hwan Jo Journal of the Korean Society for Precision Engineering.2021; 38(9): 691. CrossRef
Backlash Compensation for Accurate Control of Biopsy Needle Manipulators having Long Cable Transmission Gun Rae Cho, Seong-Tae Kim, Jung Kim International Journal of Precision Engineering and Manufacturing.2018; 19(5): 675. CrossRef
A Review of Recent Advances in Design Optimization of Gearbox Zhen Qin, Yu-Ting Wu, Sung-Ki Lyu International Journal of Precision Engineering and Manufacturing.2018; 19(11): 1753. CrossRef
In this paper, a study on the effectiveness of micro-peening was accomplished for improvement of fatigue characteristics for reduction gear of manned and unmanned aircraft. The Almen saturation curve was obtained by various peening injection pressure supplied from a commercial air jet peening machine. The effective micro-peening process condition was adopted as five bar. The four points rotary bending fatigue test was conducted by using test specimen made of AISI alloy that was carburized based on AMS standard in this work. From the fatigue test result, the fracture life of specimen peened by nozzle pressure with five bar and six bar was higher than the un-peened specimen by approximately 323 percent and 146 percent respectively. However, the fracture life of specimen peened by the nozzle pressure with six bar was lower by approximately 221 percent than the peened specimen by five bar. For this reason, the peening nozzle pressure with five bar was decided as the optimum micro-peening condition. Effectiveness of micro-peening was validated and this micropeening technique will be used for real manned and unmanned aircraft gear parts or other durability mechanical parts.
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A Review of Recent Advances in Design Optimization of Gearbox Zhen Qin, Yu-Ting Wu, Sung-Ki Lyu International Journal of Precision Engineering and Manufacturing.2018; 19(11): 1753. CrossRef
Recently, the use of composite materials in the defense system has grown dramatically. The strength/weight and stiffness/weight ratios of composite structures are normally higher than of metals. Woven composites, especially, are increasingly considered for a variety of applications, because they offer good workability for complicated structures. HPW193/RS1222 is one of the most famous woven composites and has been used in many types of Korean military equipment, such as antenna pedestals and radar systems. In this study, we predicted the elastic modulus of HPW193/RS1222 using the principles of unidirectional composite stiffness predictions, such as ROM (Rule of Mixture), HSR (Hart Smith 10% Rule), CLA (Classical Laminate Analysis) and LAP (Laminate Analysis Program). We compared the dynamic characteristics with the experimental predictions and finite-element analysis (FEA). From our results we concluded that transversely isotropic materials are similar to isotropic materials when the shape of the composite structure is complicated.
Electro-Mechanical Actuator installed on the aircraft plays a key role in an aircraft’s flight control through flight control computer. Reliable prediction of the actuator is important for the aircraft. To estimate the lifetime of a product, it is necessary to test full target life. However, it is very difficult to perform it due to the long life time of actuator but short period of development time with increasing cost. Therefore, accelerated life test has been used to reduce the test time for various reasons such as reducing product’s development cycle and cost. In this paper, to predict the lifetime of the actuator, we analyzed the flight profile of aircraft and adapted the method of accelerated life test in order to accelerate failure modes that might occur under user conditions. We also set up an endurance test equipment for validating the demanded lifetime of an actuator and performed accelerated life test.
The purpose of this study is to verify the energy efficiency of the integrated system combining human and a lower extremity exoskeleton robot when it is applied to the proposed gait pattern. Energy efficient gait pattern of the lower limb was proposed through leg function distribution during stance phase and the dynamic-manipulability ellipsoid (DME). To verify the feasibility and effect of the redefined gait trajectory, simulations and experiments were conducted under the conditions of walking on level ground and ascending and descending from a staircase. Experiments to calculate the metabolic cost of the human body with or without the assistance of the exoskeleton were conducted. The energy consumption of the lower extremity exoskeleton was assessed, with the aim of improving the efficiency of the integrated system.
There have been many researches about SUGV (Small Unmanned Ground Vehicle) mechanism regarding off-road mobility and obstacle negotiation. This paper introduces an analysis of geometry parameters to enhance the vertical obstacle negotiation ability for the SUGV. Moreover, this paper proposes an anti-shock structure analysis of wheels to protect the main body of the SUGV when it falls off a vertical obstacle. Major system geometry parameters will be determined under certain constraints. The constraints and optimization problem for maximizing the ability of vertical obstacle negotiation will be presented and discussed. Dynamic simulation results and experiments with manufactured platform will also be presented to validate the analysis. Several types of wheel materials and structures will be compared to determine the best anti-shock wheel design through FEM (Finite Element Method) simulations.
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