The robot industry has greatly improved over the past 50 years. It is expected that in the era of the 4th industrial revolution the field of applying robots will expand. Motors are essential in order to operate and control robots. However, robots’ precision requires the application of robot reducers. In particular, many types of harmonic drive reducers have been applied to robots. Harmonic drive reducers have theoretically zero-backlash, but they actually exist for tolerances of Oldham coupling parts. In this paper, dynamic analysis adapted dimensional tolerances of oldham coupling was used to figure out the system backlash characteristics of harmonic drives.
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Method for Radial Stiffness Measurement of Strain Wave Gear Flexspline Sangwoong Lee, Daegwon Koh, Jong-Geol Kim, Murim Kim Journal of the Korean Society for Precision Engineering.2024; 41(12): 923. CrossRef
Due to the recent 4th industrial revolution and explosive interest in smart factories, the demand for industrial robots and related technologies is rapidly increasing. In order to develop a precision reducer for robots, a measurement technology of the small teeth of a gear is very important. This paper developed a method to measure the tooth shape of a precision harmonic reducer for robots and to evaluate the tooth shape measurement error quantitatively. The tooth shape of the flexspline of a harmonic drive was measured using three instrumental devices: a stylus, a projector, and a laser line scanner. A mathematical tool was also developed to evaluate the error by comparing the designed and measured teeth. The measured tooth profile was quantitatively assessed with maximum, average, and root mean square error. The measurement method using a stylus has disadvantages of careful measurement effort and a small measuring range. However, it has better precision. On the other hand, the projection method shows a moderate performance without much effort during measurement.
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The Prediction of the Angular Transmission Error of a Harmonic Drive by Measuring Noncontact Tooth Profile and Considering Three-dimensional Tooth Engagement Beom-Seok Kim, Seung-Tae Jeong, Hyeong-Joon Ahn International Journal of Precision Engineering and Manufacturing.2023; 24(3): 371. CrossRef
Actuators for exoskeleton robots comprise various types such as electric, hydraulic, and pneumatic and it is necessary to apply the correct actuator according to the purpose. Most exoskeleton robots mainly use electric actuators, and some special-purpose robots, such as for heavy-load transport requiring large force, use hydraulic actuators. In this paper, friction of the actuation module consisting of a harmonic drive and a brushless DC motor is measured through experiments. And the friction characteristics of the actuation module are analyzed. The harmonic drive transmission system has various advantages, but it also has hysteresis and nonlinear friction characteristics. The friction compensation control of the actuation module enables precise control of the exoskeleton robot, and improves the robot’s performance. Appropriate friction model selection and design affects friction compensation performance. In this study, static and dynamic friction models are designed and analyzed based on the friction data of the actuation module.
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Method for Radial Stiffness Measurement of Strain Wave Gear Flexspline Sangwoong Lee, Daegwon Koh, Jong-Geol Kim, Murim Kim Journal of the Korean Society for Precision Engineering.2024; 41(12): 923. CrossRef
A Recurrent Neural Network for 3D Joint Angle Estimation based on Six-axis IMUs but without a Magnetometer Chang June Lee, Woo Jae Kim, Jung Keun Lee Journal of the Korean Society for Precision Engineering.2023; 40(4): 301. CrossRef
Friction Compensation of Electric-Motor Driven Revolute Joint with Harmonic Gear Seong-Hee Cho, Young-Seog Kim, Jung-Yup Kim Journal of the Korean Society of Manufacturing Technology Engineers.2020; 29(3): 259. CrossRef
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