This study details the development of an ultra-precision air-bearing stage that integrates real-time motion error measurement and compensation features. The motion errors addressed include horizontal and vertical straightness errors, as well as roll, pitch, and yaw errors. These errors are measured by an embedded system that incorporates five capacitive sensors and a reference mirror within the stage. A key advantage of this stage is its capability to perform real-time compensation using the internal measurement system and on-stage pneumatic regulators, eliminating the need for external measurement and compensation devices. Experimental results show a significant reduction in motion errors, with horizontal and vertical straightness errors decreasing from 3.09 and 1.95 μm to 0.29 and 0.25 μm, respectively. Additionally, roll, pitch, and yaw errors were reduced from 3.18, 3.45, and 4.93 arcsec to 0.35, 0.41, and 0.49 arcsec, respectively. These results clearly demonstrate the effectiveness of the proposed approach.
This paper presents a method for estimating the fatigue life of crossed roller bearings (XRBs). XRBs feature a single row of rollers arranged alternately at right angles, making them ideal for applications that require high precision and a compact design. In rolling-element bearings, fatigue life is a crucial design parameter for ensuring long-term reliability and performance. However, existing fatigue life estimation models for XRBs in the literature are limited to basic rating life, with no models available for reference rating life. To address this gap, we developed a comprehensive fatigue life prediction model specifically for XRBs. We formulated a corresponding dynamic load rating to align with the values provided by bearing manufacturers and calibrated an unknown adjustment factor for XRBs using a commercial program. Additionally, a parametric study was conducted to investigate the impact of varying diametral clearance, external loads, roller dimensions, and roller profile parameters on the fatigue life of XRBs.
This study investigates the influence of operating diametral clearance on the performance of angular contact ball bearings (ACBBs). It examines critical factors affecting diametral clearance, including mounting conditions, external loads, temperature fluctuations, and rotational speeds. A novel model combining quasi-static and fit-up approaches is proposed to analyze the effects of operating diametral clearances on ACBB performance. This model incorporates key elements such as ball-race contact loads, interactions between the shaft and inner ring, interference fits between the housing and outer ring, centrifugal expansion of the rotating shaft and inner ring, and temperature-induced changes. Internal clearance variations are computed using the thick-ring theory. Simulations are conducted to predict ACBB characteristics under various fit-up conditions, including contact load distribution and stiffness, with results validated using commercial software. The study also explores the impact of various operating diametral clearances on ACBB performance under differing fitting conditions, external loads, and rotational speeds.
In continuous-process systems, failures of rolling-element bearings typically cause accidents, reduced productivity, and production-related financial losses. Therefore, predicting both the lifespan of rolling-element bearings and their replacement time is crucial for preventing machine system failures. Accordingly, numerous studies have reported various machine and deep learning classifiers for predicting the lifespan of bearings. However, these studies did not consider degradation trends of bearings. Thus, this study aimed to develop an algorithm to predict the lifespan of a bearing by considering its degradation trend. A vibration dataset of bearings was obtained at low and high speeds. Using a second-order curve-fitting model, various degradation patterns in the dataset were classified. Appropriate time-domain or frequency-domain feature variables applicable to the design of a classifier were determined according to classified patterns. In addition, the classifier was trained using multiple bidirectional long short-term memories. Finally, the performance of the developed classifier was verified experimentally.
This paper presents an integrated thermo-mechanical model for analyzing angular contact ball bearings (ACBBs) operating under oil-jet lubrication. The proposed approach enables a comprehensive analysis of both the mechanical and thermal behavior of the ACBB system. The proposed formulation employs a quasi-static approach to accurately calculate contact loads and heat generation, taking into careful consideration variations in internal clearance resulting from factors such as surface pressure, centrifugal forces, and thermal expansion. For the thermal analysis, a refined thermal network model is utilized. The proposed thermal model incorporates a newly derived correlation for the drag coefficient under oil-jet lubrication, which is obtained through high-fidelity computational fluid dynamics simulations. The validity of the proposed model is confirmed through comparison with experimental data. Furthermore, extensive simulations are conducted to investigate the impact of bearing fit-up and thermal variations on the performance of ACBBs.
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Study on the Effects of Operating Diametral Clearance Change on the Characteristics of Angular Contact Ball Bearings Patrick John Po, Gilbert Rivera, Jin-Hyeok Sa, Seong-Wook Hong Journal of the Korean Society for Precision Engineering.2024; 41(12): 997. CrossRef
Automatic transmissions, which have the advantages of compact structure and smooth shifting, are installed in various vehicles with engines and hybrid power sources. Research and development are continuously being conducted to improve power and fuel efficiency. In this study, the influence of helix direction and helix angle of the planetary gear set on thrust-bearing power loss in an automatic transmission was analyzed. A sample automatic transmission model was constructed to analyze the axial load and bearing relative rotation speed, which are the main factors in thrust-bearing power loss. The relative rotation speed of the bearing was analyzed using the sample model, and the thrust-bearing load in the axial direction was analyzed according to the helix direction of the planetary gear set constituting the model and the helix angle of the planetary gear set. The power loss occurring in thrust-bearing was derived using the analysis results of relative rotational speed and load, and the influence of the helix direction and helix angle of the planetary gear set was analyzed.
Rolling bearing fatigue life is an essential criterion in industrial equipment design and manufacturing and requires precise maintenance and replacement predictions. ISO/TS 281:2007 and 16281:2008 are commonly used for angular contact ball bearing (ACBB) fatigue life calculations, but they do not account for the characteristics of individual bearing elements under combined loading conditions. This study proposes an enhanced formula for calculating fatigue life modification factors that considers individual element-specific contact loads and resulting film thickness variations. The proposed fatigue life formula provides longer life predictions than the conventional method of determining modification factors based solely on maximum contact loads. This difference is particularly noticeable in low-speed and/or heavy-loading applications. Analysis conducted using the proposed fatigue life formula on various factors affecting fatigue life revealed that fluid kinetic viscosity coefficients, temperature-associated density changes, and changes in radial loads and rotational speeds could significantly impact the fatigue life of ACBBs. The proposed fatigue life formula is expected to increase the accuracy of ACBB fatigue life predictions.
This paper presents the development of a design optimization module for achieving the best performance of hydrostatic bearings. The design optimization module consists of two components: a bearing performance analysis module and an optimization module that utilizes optimization algorithms. Widely recognized global search methods, genetic algorithm (GA), and particle swarm optimization (PSO) algorithm, were employed as the optimization algorithms. The design optimization problem was defined for hydrostatic bearings. Optimization design processes were carried out to improve load capacity, stiffness, and flow rate. Subsequent experimental validation was conducted through the fabrication of a practical experimental setup. The design optimization model demonstrated superior performance compared to the initial model while satisfying design conditions and constraints. This confirms the practical applicability of the design optimization module developed in this study.
Factors such as weight reduction and improved fuel efficiency of vehicles interfere with the efficiency of roller bearings in automobiles under harsh conditions. In particular, studies are ongoing to increase the load capacity and rigidity under highspeed conditions. The development of tapered roller bearings that can be used under high-speed conditions is accelerating. In the case of high-speed bearings, factors such as centrifugal force, gyroscopic moment, and slippage have a greater influence on the performance of the bearing, unlike the traditional operating mechanisms. The resulting lubrication characteristics have a profound impact on the failure mode of the bearing. In particular, unlike traditional roller bearings, system failure due to damage to the retainer frequently occurs, suggesting the need for prompt investigation. In this study, the rotational characteristics and strength of three models, a steel cage and two plastic cages for tapered roller bearings with the same internal structure, were examined. A comparative analysis of retainers with different shapes and materials can reveal the factors contributing to optimal performance under high-speed operating conditions and the optimal design of bearings.
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Grinding Characteristics of a Hybrid GrindingSuperfinishing Wheel for Precision Bearing Roller Finishing Kang-su Lee, Young-rin Song, Dong-ho Yang, Sang-hyeop Lee, Jong-chan Lee Journal of the Korean Society of Manufacturing Process Engineers.2026; 25(3): 95. CrossRef
This paper presents an improved formulation, to estimate the sliding friction torque of deep groove ball bearings (DGBBs). Running torque of rolling element bearings, is directly associated with heat generation in rotating machines. Among the components of running torque, sliding friction is a major friction source in ball bearings. For DGBBs, sliding friction is dominated by spinning and differential sliding between balls and races. This paper addresses the sliding friction torque components of DGBBs: Spinning friction, differential sliding friction due to the ball rotation, and differential sliding friction due to the ball orbital motion. An efficient and accurate computational method is proposed for the individual sliding friction sources, based on pure rolling lines in the elliptical contact area between the balls and races. The proposed method applies an updating algorithm, for estimating more accurate information about the pure rolling lines. The proposed method was validated in terms of comparison with other methods, and with the empirical formulae provided by a bearing manufacturer. Simulations were also conducted to investigate the impacts of important parameters on the sliding friction torque in DGBBs.
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Study on Thermo-mechanical Modeling and Analysis of High-speed Angular Contact Ball Bearings Under Oil-jet Lubrication Gilbert Rivera, Shinhyang Park, Chan-sik Kang, Dongjoo Kim, Seong-Wook Hong Journal of the Korean Society for Precision Engineering.2024; 41(7): 569. CrossRef
Analytical formulation for sliding friction torque in cylindrical roller bearings Gilbert Rivera, Patrick John Po, Chan-sik Kang, Seong-Wook Hong Journal of Mechanical Science and Technology.2024; 38(9): 4669. CrossRef
Development of a Statically Balanced Lifting Device for Repetitively Transporting Construction Materials Byungseo Kwak, Seungbum Lim, Jungwook Suh Journal of the Korean Society for Precision Engineering.2024; 41(12): 929. CrossRef
Effect of Surface Roughness on the Friction Moment in a Lubricated Deep Groove Ball Bearing Harsh Kumar, Vaibhav Gupta, Velamala Bharath, Mayank Tiwari, Surajit Kumar Paul, Lokesh Agrawal, Arendra Pal Singh, Ayush Jain Lubricants.2024; 12(12): 443. CrossRef
Magnetic bearings are being actively adopted by the turbo-chiller industry because of their higher efficiency during partial load, quieter operation, and smaller footprint than that which machines with ball bearings provide. Since magnetic bearings are open-loop unstable, feedback control is necessary. In the industry, traditional PID-based control is preferred to model-based control, because of its simplicity. When traditional control algorithms are used, significant resources are required to obtain and tune control parameters, which is an impediment to the widespread use of magnetic bearing technology in the industry. In this paper, we propose a mixed optimization method by combining genetic algorithm and sequential quadratic programming. To obtain the initial guess to be used for the mixed optimization, a phase-margin maximization algorithm is also proposed, based on the rigid-body model of the system. Mixed optimization results in suitable control parameters in less than 2.8% of the time it takes a genetic algorithm only to find similar solutions. The proposed optimization also ensures the robustness of the control parameters. The output sensitivity measured from a prototype compressor with magnetic bearings confirms the validity of the control parameters.
Magnetic bearings use electromagnetic force to support the rotating shaft without any mechanical contact and actively control shaft vibration; hence, there is no mechanical friction and wear due to contact during the operation, and it has a semi-permanent lifespan. Because magnetic bearings are unstable by themselves, a gap sensor is necessary to stably control the position of objects. However, there is a limit to the improvement in control performance because the sensor is installed on one side of the bearing and is not aligned with the electromagnet. This paper presents a newly developed collocated eddy-current PCB displacement sensor for magnetic bearings. The PCB sensor is designed and built to install between the poles of a magnetic bearing and to minimize the electromagnetic interference. A sensor calibration test is performed to evaluate the sensitivity and noise of the collocated PCB sensor. In addition, the control performance of the collocated PCB sensor is evaluated by measuring the closed-loop sensitivity function of a 1 DOF magnetic suspension test rig. The collocated PCB sensor has noise within ±1 μm and excellent vibration suppression performance.
Angular contact ball bearings (ACBBs) are widely used in rotating machinery due to their heavy load-carrying capacity and excellent accuracy in high-speed operation. However, employing an ACBB requires a careful analysis because the characteristics of the ACBB significantly depend on the operating condition. The ball-race contact condition of an ACBB is one of the most important factors that can change its properties. This study deals with the ball-race contact behavior concerning several important parameters, such as rotational speed, unloaded contact angle, and external loading. Between the ball and race under loading, an elliptical contact area is formed, in which pure rolling lines may exist. In the region other than the pure rolling lines, sliding dominates due to differential slippage in the elliptical contact area. We investigated the behavior of ball-race contact in terms of the pure rolling lines. A computational procedure was presented to determine the pure rolling lines. Through simulations, it was found that rotational speed, unloaded contact angle, axial preload, and radial load significantly affected the number and locations of pure rolling lines. The presented results are useful for investigating and estimating the sliding friction torque for ACBBs.
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Rolling contact bearing modelling solutions: Critical analysis and comparison Raúl Gismeros Moreno, Filipe Marques, Eduardo Corral Abad, Jesús Meneses Alonso, Paulo Flores Friction.2026; 14(3): 9441147. CrossRef
Influence of ball bearing contact angle on interface kinematics, load, and sliding power losses Pello Alberdi, Aitor Arana, Aitor Oyanguren, Jon Larrañaga, Ibai Ulacia Mechanism and Machine Theory.2026; 222: 106396. CrossRef
Influencia del ángulo de contacto en la cinemática y la distribución de carga de rodamientos a bolas Pello Alberdi Quevedo, Ibai Ulacia Garmendia, Aitor Arana Ostolaza, Jon Larrañaga Amilibia, Aitor Oyanguren Garcia Anales de Ingeniería Mecánica.2025;[Epub] CrossRef
A general kinematic model for lubricated ball bearings based on the minimum energy hypothesis Pello Alberdi, Aitor Arana, Aitor Oyanguren, Jon Larrañaga, Ibai Ulacia Tribology International.2024; 196: 109698. CrossRef
Analytical formulation for sliding friction torque in cylindrical roller bearings Gilbert Rivera, Patrick John Po, Chan-sik Kang, Seong-Wook Hong Journal of Mechanical Science and Technology.2024; 38(9): 4669. CrossRef
Stiffness characteristics and experimental study of angular contact ball bearings considering the influence of rotational speed Runlin Chen, Fan Xu, Gengzhou Liu, Jiakai Li, Shaodong Zhao, Xingyu Fan, Yanchao Zhang, Saisai Lv Advances in Mechanical Engineering.2024;[Epub] CrossRef
Study on Thermo-mechanical Modeling and Analysis of High-speed Angular Contact Ball Bearings Under Oil-jet Lubrication Gilbert Rivera, Shinhyang Park, Chan-sik Kang, Dongjoo Kim, Seong-Wook Hong Journal of the Korean Society for Precision Engineering.2024; 41(7): 569. CrossRef
Improved Formulation for Sliding Friction Torque of Deep Groove Ball Bearings Gilbert Rivera, Van-Canh Tong, Seong-Wook Hong Journal of the Korean Society for Precision Engineering.2022; 39(10): 779. CrossRef
This paper presents the characteristics of tapered roller bearings (TRBs) taking into consideration the effects of tapered roller angle error which may occur during manufacturing. To this end, a TRB model including tapered roller angle errors was developed. The effects of tapered roller angle error on the contact load distribution, bearing stiffness and fatigue life were investigated with respect to changes in the tapered roller angle error. A statistical analysis of the fatigue life of TRBs was also provided with respect to tapered roller angle error. Simulation results show that the tapered roller angle error changes the load distribution of the rollers and causes angular misalignment in TRBs, and subsequently, influences the bearing stiffness and fatigue life. The statistical analysis shows that the Weibull distribution is an acceptable method to represent the statistical fatigue life for the practical range of tapered roller angle errors.
Since sCO₂ (Supercritical Carbon Dioxide) turbomachinery are generally small and operate at high rotational speed, the bearings remain a significant challenge to the design of the turbomachinery for the sCO₂ power cycles. However, a fluid induced instability similar to the oil whirl may occur even with the magnetic bearing under high pressure and high speed conditions of the sCO₂ turbomachinery. This paper presents experimental investigation on the instability of a sCO₂ compressor supported by the magnetic bearing. First, we introduce the sCO₂ compressor supported by the magnetic bearing. The procedure to guarantee the rotordynamic performance of the sCO₂ compressor supported by the magnetic bearing is provided. Then, the effects of the working condition such as the pressure and rotating speed on the fluid induced instability are investigated experimentally. Finally, a strategy to resolve the fluid-induced instability with conventional PID control is proposed and experimentally verified.
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Turbomachine Operation with Magnetic Bearings in Supercritical Carbon Dioxide Environment Alexander Johannes Hacks, Dieter Brillert International Journal of Turbomachinery, Propulsion and Power.2022; 7(2): 18. CrossRef
A Study on the Efficient Optimization of Controller for Magnetic Bearings Supporting Oil-Free Turbo-Chiller Compressor Eunsang Kwon, Myounggyu Noh, Namsoo Lee, Seongki Baek, Young-Woo Park Journal of the Korean Society for Precision Engineering.2022; 39(2): 123. CrossRef
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