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Oiwa, Takaaki Korean Society for Precision Engineering 2007 International Journal of Precision Engineering and Vol.8 No.2
A machining system that generates accurate relative motions between the tool and workpiece is required to realize ultra precise machining or measurements. Accuracy improvements for each element of the machine are also required. This paper proposes a machining system that uses a compensation device for the six-degree-of-freedom (6-DOF) motion error between the tool and workpiece. The compensation device eliminates elastic and thermal errors of the joints and links due to temperature fluctuations and external forces. A hexapod parallel kinematics mechanism installed between the tool spindle and surface plate is passively actuated by a conventional machine. Then the parallel mechanism measures the 6-DOF motions. We describe the conception and fundamentals of the system and test a passively extensible strut with a compensation device for the joint errors.
Takaaki Oiwa 한국정밀공학회 2007 International Journal of Precision Engineering and Vol.8 No.2
A machining system that generates accurate relative motions between the tool and workpiece is required to realize ultraprecise machining or measurements. Accuracy improvements for each element of the machine are also required. This paper proposes a machining system that uses a compensation device for the six-degree-of-freedom (6-DOF) motion error between the tool and workpiece. The compensation device eliminates elastic and thermal errors of the joints and links due to temperature fluctuations and external forces. A hexapod parallel kinematics mechanism installed between the tool spindle and surface plate is passively actuated by a conventional machine. Then the parallel mechanism measures the 6-DOF motions. We describe the conception and fundamentals of the system and test a passively extensible strut with a compensation device for the joint errors.
Toshiharu Tanaka,Takaaki Oiwa,Akira Kotani 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.11
A gear is used not only for power transmission but also in precision positioning. A conventional and general gear has only one degree of freedom motion. Therefore, the case of its use is limited. In this paper, we propose and manufacture an innovative spherical gear. The proposed spherical gear has a multiple degrees of freedom motion. Compared with other spherical gear, the proposed spherical gear does not have complex shape. Moreover, the handle of the proposed spherical gear is similar to that of a spur gear. The experimental apparatus using the spherical gear pair measures a transmission efficiency and an angular backlash between the gears. According to experimental results, the spherical gear teeth could mesh firmly and transmit power at any shaft angle. In addition, the maximum transmission efficiency and the angular backlash become about 87.1% and 16.9 mrad when the shaft angle is 0°, respectively.
Endocuff-Assisted versus Cap-Assisted Colonoscopy Performed by Trainees: A Retrospective Study
Yutaka Okagawa,Tetsuya Sumiyoshi,Yusuke Tomita,Shutaro Oiwa,Fumihiro Ogata,Takashi Jin,Masahiro Yoshida,Ryoji Fujii,Takeyoshi Minagawa,Kohtaro Morita,Hideyuki Ihara,Michiaki Hirayama,Hitoshi Kondo 대한소화기내시경학회 2020 Clinical Endoscopy Vol.53 No.3
Background/Aims: The adenoma detection rate (ADR) of screening colonoscopies performed by trainees is often lower than thatof colonoscopies performed by experts. The effcacy of cap-assisted colonoscopy (CAC) in adenoma detection is well documented,especially that of CACs performed by trainees. Endocuff, a new endoscopic cap, is reportedly useful for adenoma detection; however,no trials have compared the effcacy of Endocuff-assisted colonoscopy (EAC) and CAC conducted by trainees. Therefore, the presentstudy retrospectively compared the effcacy between EAC and CAC in trainees. Methods: This was a single-center, retrospective study involving 305 patients who underwent either EAC or CAC performed by threetrainees between January and December 2018. We evaluated the ADR, mean number of adenomas detected per patient (MAP), cecalintubation rate, cecal intubation time, and occurrence of complications between the EAC and CAC groups. Results: The ADR was significantly higher in the EAC group than in the CAC group (54.3% vs. 37.3%, p=0.019), as was the MAP (1.36vs. 0.74, p=0.003). No significant differences were found between the groups with respect to the cecal intubation rate or cecal intubationtime. No major complications occurred in either group. Conclusions: Our results suggest that EAC exhibits increased ADR and MAP compared to CAC when performed by trainees.
Influence of Rolling Friction in Linear Ball Guideways on Positioning Accuracy
Tanaka, Toshiharu,Ikeda, Kyohei,Otsuka, Jiro,Masuda, Ikuro,Oiwa, Takaaki Korean Society for Precision Engineering 2007 International Journal of Precision Engineering and Vol.8 No.2
Linear ball guideways have been used recently in precision or ultra-precision positioning devices. However, when the inner balls begin to roll or the moving direction reverses, these guideways are subject to rolling friction or nonlinear spring behavior. An ultra-precision device with a linear motor, referred to as a 'tunnel actuator' (TA), has been constructed to measure these phenomena. The application of a TA is beneficial for two reasons: it mostly cancels the attractive magnetic force between the stator and mover (armature), and its magnetic flux leakage is very low. The influence of the nonlinear spring behavior in ball guideways was investigated in this study using the pure driving force from a TA. The equilibrium between the driving force from the TA and the nonlinear spring force provided great accuracy for a positioning stage using a linear ball guideway.
Influence of Rolling Friction in Linear Ball Guideways on Positioning Accuracy
Toshiharu Tanaka,Kyohei Ikeda,Jiro Otsuka,Ikuro Masuda,Takaaki Oiwa 한국정밀공학회 2007 International Journal of Precision Engineering and Vol.8 No.2
Linear ball guideways have been used recently in precision or ultra-precision positioning devices. However, when the inner balls begin to roll or the moving direction reverses, these guideways are subject to rolling friction or nonlinear spring behavior. An ultra-precision device with a linear motor, referred to as a 'tunnel actuator' (TA), has been constructed to measure these phenomena. The application of a TA is beneficial for two reasons: it mostly cancels the attractive magnetic force between the stator and mover (armature), and its magnetic flux leakage is very low. The influence of the nonlinear spring behavior in ball guideways was investigated in this study using the pure driving force from a TA. The equilibrium between the driving force from the TA and the nonlinear spring force provided great accur acy for a positioning stage using a linear ball guideway.