Hybrid mobile robot is the system that will practically combine legged walking and skated driving in the same system. Therefore, this robot has own problems of inverse kinematics that are not considered in typical walking robots. In this paper, I fully categorized the inverse kinematics problems for hybrid mobile robot with general motion by walking and driving on an inclined plane, including switching end-effectors between foots and blades. I also solved the inverse kinematics for each case of problems. I here actively adopted the coordinate transformation derived from the inclined plane to cope with the random motion of foots and blades on the plane. I then presented several examples of the inverse kinematics problems with specific situations, and verified the validity of the analysis method from the results.

In this study, the effects of repetition of assembly and disassembly of polymer electrolyte membrane fuel cells on electrochemical performance were systematically investigated. Additionally, the effects of additional activation on polymer electrolyte membrane fuel cells were evaluated. All fuel cells were measured every three days. For the disassembled polymer electrolyte membrane fuel cells, membrane electrode assemblies were stored in a vacuum desiccator. For the maintained assembly, fuel cells were stored at room temperature. The performance and electrochemical characteristics of the fuel cell were analyzed by electrochemical impedance spectroscopy. As a result, the addition of activation to maintained assembly fuel cells showed the best performance among fuel cells with other assembly and activation conditions. Repetition of assembly and disassembly, as well as insufficient activation, caused degradation of the performance of fuel cells.

Total hip replacement is a representative treatment for avascular necrosis of the femoral head. However, the stress shielding caused by the replacement induces dissociation of the artificial hip joint and various complications. Many studies have tried to explore the stress shielding but, most studies have been conducted at macro level and not at micro level. Thus, this study aimed to quantitatively analyze the structural behavior of the proximal femur according to total hip replacement at the micro level to explore the stress shielding. For this purpose, this study selected the artificial hip joint of the single wedge type and implanted the joint into a proximal femur that has a high resolution of 50 μm. Then the structural behavior of the implanted femur was analyzed by comparing that of the intact femur under three daily activity loads. As a result, the high possibility was confirmed that the stress shielding will occur in both cortical and cancellous bones under the one-legged stance movements. Additionally, it was discovered that the cancellous bone had a considerably lesser chance of adducting at an angle similar to the neck shaft angle of an artificial hip joint.

This paper proposes a new rotary welding torch with a ball-jointed mechanical seal structure that simultaneously realizes the enclosure of CO₂ gas, the energization of welding current, and the insulation for system protection. In order to effectively compare the operation mechanism of the proposed device with the conventional rotary welding torch, a schematic technique is introduced to clearly visualize the operation and connection structure of the model. The kinematic state and constraint degrees of freedom of the tool are clearly shown, and it is easy to distinguish between the two designs that use different component parts and connection structures but result in the same final motion. In addition, the four dynamic characteristics of a rotary torch operating at 20 Hz (driving torque, vibration reaction force, natural frequency, and inertial mismatch) were analyzed to demonstrate superior performance to conventional products. The welding test showed that the tool normally operated even in a harsh welding environment, verifying its applicability in the field.

Recently, the demand for electric vehicles is intensively increasing in accordance with environmental issues in automotive industries. Given that noise level from the electric vehicles is significantly lower than that from conventional vehicles with internal combustion engine, noise management has become more critical. Conventionally, glass run channel (GRC) is used to block the noise and contaminants from outside of vehicle. In this work, the friction and degradation characteristics of GRC with thermoplastic vulcanizate substrate were assessed. The tests were performed using the reciprocating tribo-tester developed to replicate the contact sliding between GRC and window glass. Also, the test conditions were determined in consideration of operating condition of GRC. As a result, the plastic deformation of the lips due to creep and wear of the slip coating deposited on the lip surface were found to be major degradation mechanisms. Furthermore, it was shown that the friction and degradation increased significantly due to the misalignment between GRC and window glass, associated with the significant increase in the reaction force. The results of this work provide fundamental understanding of the degradation characteristics of GRC, and therefore are expected to be useful for the design of GRC with improved performance.

The utilization of aerospace technology is growing to meet various requirements of climate change sensing, communications, and the military. Large aperture and precise reflective optical systems such as mirrors are needed to acquire high-quality data, and the requirements of lightness, low cost, and low deformation should also be met to operate in the space environment. In this review, we highlight the recent progress of reflective optical systems for aerospace applications. In particular, optical systems for artificial satellites and homing optics are mainly introduced, and optical and mechanical simulations are discussed according to operating environments. We also discuss various reflective optic designs, materials, and operating principles for aerospace applications, such as a homing head and optical payload. We hope that this review provides approaches for developing surveillance systems, exploring space, and addressing the climate crisis.

The linear motion guideway (LM guide) is one of the key parts of precision motion and positioning, and it requires high straightness, form accuracy, stiffness, and surface quality. LM guides are actively used in manufacturing facilities for automobiles, aerospace, optics, semiconductors, robots, displays, and portable communication equipment. At present, most of LM guides are based on rolling contact, using either balls or rollers. Roller LM guides have been in high demand in recent years in various industrial fields that require high rigidity. In this study, the friction characteristics of ball and roller LM guides with the same rail width were compared, and friction behavior was analyzed. An experimental setup consisting of a driving unit, specimen, force sensor, and signal acquisition unit was constructed, and signals were collected under various conditions. Three lubrication conditions were used: no lubrication (dry surface), ISO-VG 32, and 68, and a wide feed-rate range from 1 to 100 mm/s was selected. The experimental results showed that the ball LM guide and the roller LM guide had significantly different friction characteristics, which were analyzed from the aspect of Stribeck curve components. In conclusion, friction behavior differed according to lubrication conditions in the no-payload state of the ball and roller LM guides, and the effect of lubrication conditions on friction behavior was shown.

In this study, we successfully demonstrated a fuel cell fabrication method using a platinum-samarium-doped ceria (Pt-SDC) composite cathode, which could reduce the platinum content while maintaining the same thickness as the functional layer. The Pt-SDC composite cathode was deposited by a sputtering process in which two materials were simultaneously deposited by a co-sputtering system. Despite the decreased platinum content in the composite cathode, we achieved high performance of the fuel cell since Pt-SCD was able to form triple-phase boundaries (TPBs) not only at the interface between the cathode and the electrolyte but at the entire volumetric surface of the cathode. This composite cathode revealed that Pt-SDC could enhance the oxygen reduction reaction rate by enlarging the TPB site in the cathode. The fuel cell fabricated in this study with a composite cathode demonstrated improved performance at 1.66 times the peak power density of a pristine fuel cell.

Anomaly detection models using big data generated from facilities and equipment have been adopted for predictive maintenance in the manufacturing industry. When facility faults or defects occur, different patterns of abnormal data are shown owing to their component behaviors. By detecting these pattern changes, it is possible to determine whether a facility abnormality occurs. This study evaluated the anomaly detection results from a combined driving system consisting of three driving motors for about six months at a manufacturing site. The learning data with an autoencoder model for about a month at the beginning of vibration data collection and continuous monitoring of anomalies using reconstruction errors showed that a component defect occurred in one driving motor, and the reconstruction error increased progressively about three months earlier than a facility manager found the failure. In addition, the micro-electro-mechanical systems sensor showed high amplitude in the entire frequency domain when high reconstruction errors occurred. However, the integrated electronics piezoelectric sensor showed different patterns as high amplitude in a specific frequency domain. The results of this study will be helpful for detecting facility abnormalities in combined driving systems using vibration sensors.

Recently, with the development of the space, mobility, semiconductor, and precision machinery industries, the processing of precision mechanical parts has been recognized as an important and a high value-added technology. Research on ultra-precision processing is actively underway to produce such products. In addition, eco-friendliness and 0% carbon are emerging as key keywords in modern industrial society, and the need for this is also increasing in the ultra-precision processing field. As the industry advances, environmental issues are becoming a major concern, and in the processing technology field, environmental destruction caused by cutting oil is becoming an issue. To solve this problem, this study measured the movement precision of the global feed system and instaled a Fine Servo that corrects the nm-level movement of the feed system in real time, using a piezoelectric actuator, to finely drive the cutting tool to control the movement necessary for machining. We intended to control variables for ultra-precision machining and measure cutting heat generation in real time to establish a dry cooling method using thermoelectric elements without using cutting oil.