Joong-Ho Shin

Bio: Joong-Ho Shin is an academic researcher from Changwon National University. The author has contributed to research in topics: Gerotor & Gear pump. The author has an hindex of 7, co-authored 16 publications receiving 195 citations.

Analytical Wear Model of a Gerotor Pump without Hydrodynamic Effect

Abstract: The contact stress in a gerotor pump is addressed in this paper because the gerotor pump cannot be adjusted for wear. The first part of this paper presents a simple and exact rotor profile equations of the gerotor pump. In the second part of this paper, an explicit formula to avoid undercut in the inner-rotor of the gerotor pump is proposed by examining the minimum radius of curvature of the inner-rotor tooth profile on the convex section. It is found that undercut does not occur so long as the minimum value of the radius of curvature on the convex section is not less than zero. Next, the contact stresses without hydrodynamic effect between the inner and outer-rotors are evaluated through the calculation of the Hertzian contact stress in the rotor teeth. Based on the above results, we finally present the wear characteristics of pHVs factor, which is proportional to the wear rate, between the rotors of the gerotor pump under quasi-static and dry contact conditions.

Optimal rotor wear design in hypotrochoidal gear pump using genetic algorithm

Abstract: The wear rate between the rotors of a hypotrochoidal gear pump is characterized. Using the knowledge of shape design on the rotors, the contact stresses without hydrodynamic effect between the rotor teeth were evaluated through the calculation of the Hertzian contact stress. Based on the above results and the sliding velocity between the rotors, a genetic algorithm (GA) was used as an optimization technique for minimizing the wear rate proportional factor (WRPF). The result shows that the wear rate or the WRPF can be reduced considerably, e.g. approximately 12.8%, throughout the optimization using GA.

Rotor profile design in a hypogerotor pump

Abstract: A geometric approach for the outer-rotor profile as a conjugate to the inner-rotor in a hypotrochoidal rotor pump (hypogerotor pump) is proposed by means of the principle of the instantaneous center and the homogeneous coordinate transformation. The inner-rotor profile is defined by the combination of two circular arcs. Next, the radius of curvature of the outer-rotor is derived with the relationships of the trochoid ratio and the inner-rotor tooth size ratio. Then by examining the minimum radius of curvature of the extended hypotrochoidal outer-rotor profile on the convex section, an explicit formula to avoid undercutting in the hypogerotor pump is proposed. It is found that undercut or self-intersection does not occur so long as the minimum value of the radius of curvature on the convex section is not less than zero. Design examples are presented to simulate the operation and to demonstrate the feasibility of the approaches using a computer-aided design program developed on C++ language.

A Study on Optimal Wear Design for a Gerotor Pump

Abstract: A disadvantage in the design of gerotor pump is a lack of parts that can be adjusted to compensate for wear in the rotor set, and as a consequence, it causes a sharp reduction of efficiency. In this paper, an attempt has been made to reduce the wear rate between the rotors of a gerotor pump. To do this, floating genetic algorithm (FGA) is used as an optimization technique for minimizing the wear rate proportional factor (WRPF). The result shows that the wear rate can be reduced considerably, e.g. approximately 8% in this paper, throughout the optimization using FGA.

Unified Approach to Cycloid Drive Profile, Stress, and Efficiency Optimization

Abstract: Cycloid drives are compact, efficient speed reducers. In this paper, a unified set of equations is presented to optimize their design. The conceptual framework and profile design are described. Sources and effects of tolerance are then introduced, including profile reduction, backlash and torque ripple, and maximum gear-ratio. Equations for stress, efficiency, and moment of inertia are provided.

Cycloid vs. harmonic drives for use in high ratio, single stage robotic transmissions

Abstract: Harmonic and cycloid drives are both compact, high ratio transmissions appropriate for use in anthropomorphic robots, although cycloid drives are rarely used in the field. This paper describes the design parameters for cycloid drives and shows the results of six cycloid models designed to match corresponding harmonic drives. Cycloid drive models were compared with manufacturing data from corresponding harmonic drives with respect to maximum gear ratio, transmission thickness, efficiency, backlash/gear ratio ripple, and reflected inertia. Cycloid drive designs were found to be thinner, more efficient, and to have lower reflected inertia than corresponding harmonic drives. However, the cycloid designs had larger gear ratio ripple and substantial backlash, and they could not meet the maximum gear ratio provided by the corresponding harmonic drives in two out of six models for equal applied torques. Two cycloid drives were manufactured to confirm efficiency predictions and demonstrated moderate to high efficiency across a range of output torques. Cycloid drives should be considered for robotic and prosthetic applications where smaller thickness/higher efficiency requirements dominate over low backlash/gear ratio ripple considerations.

Dynamics Analysis of Cycloidal Speed Reducers With Pinwheel and Nonpinwheel Designs

Abstract: Cycloidal speed reducers are composed primarily of an eccentric shaft, output parts, and a set comprising a cycloidal gear and pinwheel with pins or a cycloidal gear and cycloid internal gear. This paper investigates the contact and collision conditions of these components, as well as their stress variations during the transmission process. To do so, a system dynamics analysis model of a cycloidal speed reducer is constructed, together with dynamics analysis models for two design types: A traditional pinwheel design and a nonpinwheel design (i.e., a design in which a cycloid internal gear replaces the pinwheel). Based on the theory of gearing, a mathematical model of the pinwheel with pins, cycloidal gear, and cycloid internal gear is then built from which the component geometry can be derived. These dynamics analysis models, constructed concurrently, are used to investigate the components' movements and stress variations, and determine the differences between the transmission mechanisms. The results indicate that the nonpinwheel design effectively reduces vibration, stress value, and stress fluctuation, thereby enhancing performance. An additional torsion test further suggests that the nonpinwheel design's output rate is superior to that of the traditional pinwheel design.