Theoretical and Experimental Analysis of a Cycloidal Speed Reducer

Journal of Mechanical Design (Impact Factor: 1.25). 11/2008; 130(11). DOI: 10.1115/1.2978342


Compared with common speed reducers, the cycloidal ones (also known as cycloid drives) cover a wider range of transmission ratios, have a higher load-carrying capacity, are smaller, exhibit a smoother running and a good efficiency. These characteristics make them attractive for industrial applications, especially for robotics applications, machine tools and linear axis positioning in assembly machinery. In this paper, a theoretical and experimental investigation on an innovative cycloidal speed reducer will be presented. The typical cycloid drive has a planet wheel, the profile of which is the inner offset of an epitrochoid, meshing with cylindrical rollers connected to the case. This reducer, on the contrary, has an external ring gear, the transverse profile of which is the external offset of an epitrochoid, and engages with the planet wheel by means of cylindrical rollers. This paper will investigate the structural characteristics and the kinematical principles of this type of reducer. A theoretical approach based on the envelope theory (following Litvin’s approach) will be developed and compared with a development of Blanche and Yang’s approach. Furthermore, a simplified procedure to calculate force distribution on cycloid drive elements, as well as its power losses and theoretical mechanical efficiency will be presented. The effects of design parameters on the values of the forces will be studied, for an optimal design of this type of reducer. The theoretical model will be then tuned using the results of tests on a specific rig. As a result of the experimental tests, the reducer mechanical efficiency dependency on speed and torque will be described. The aim of this work is to perform the fine tuning of a theoretical model in order to predict the operating behavior of the cycloid drive, and to improve its design procedure.

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    • "A double crank ring-plate-type cycloid drive which is able to transfer larger torque than a typical existing planetary cycloid drive is presented in Ref. [21]. Gorla et al. [22] developed a new type of cycloidal speed reducer with an external ring gear and cylindrical rollers mounted on the cycloid disc. They derived a procedure for calculating the contact forces on cycloid drive elements , power losses, and theoretical mechanical efficiency. "
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    ABSTRACT: A new design of a two-stage cycloidal speed reducer is presented in this paper. A traditional two-stage cycloidal speed reducer is obtained by the simple combination of single-stage cycloidal speed reducers. A single-stage reducer engages two identical cycloid discs in order to balance dynamical loads and to obtain uniform load distribution. Consequently, the traditional two-stage reducer has four cycloid discs, in total. The newly designed two-stage cycloidal speed reducer, presented in this paper, has one cycloid disc for each stage, that is, two cycloid discs in total, which means that it is rather compact. Due to its specific concept, this reducer is characterized by good load distribution and dynamic balance, and this is described in the paper. Stress state analysis of cycloidal speed reducer elements was also realized, using the finite elements method (FEM), for the most critical cases of conjugate gear action (one, two, or three pairs of teeth in contact). The results showed that cycloid discs are rather uniformly loaded, justifying the design solution presented here. Experimental analysis of the stress state for cycloid discs was realized, using the strain gauges method. It is easy to conclude, based on the obtained results, that even for the most critical case (one pair of teeth in contact) stresses on cycloid discs are in the allowed limits, thus providing normal functioning of the reducer for its anticipated lifetime.
    Journal of Mechanical Design 08/2011; 133(8):085001-1. DOI:10.1115/1.4004540 · 1.25 Impact Factor
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    ABSTRACT: This paper introduces an original analytical procedure for the computation of the planar curve in meshing with a general two dimensional curve. Considering a planar gear mechanism with a constant transmission ratio, in this work a general expression of the explicit solution of the equation of meshing is presented. Besides, an original method to evaluate the undercutting conditions, based on the explicit solution of the equation of meshing, is shown. Taking into account a generating curve in homogeneous coordinates and the transformation matrixes which define the relative motion between the profiles, the solution of the equation of meshing and consequently the profile conjugated to the generating curve can be directly found, by a simple coordinate transformation. The explicit solution is expressed with the general conventions of the theory of gearing. Once the equation of the conjugated curve is obtained, a direct method for the evaluation of the undercutting condition can be applied. The proposed method allows to implement effective and affordable computer codes for the computation of conjugate planar profiles.
    Computer Methods in Applied Mechanics and Engineering 05/2009; 198(27-29):2218-2224. DOI:10.1016/j.cma.2009.02.005 · 2.96 Impact Factor
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    ABSTRACT: Rapid prototyping is a technology using a CAD/CAM, and a molding machine, which manufactures a prototype model rapidly. Since it can make products with complex shapes of three dimensions, the cost and time for development is reduced. It is convenient in the production of a wide range of prototypes, particularly in a product's development. The purpose of our research was to manufacture an effective motor reducer to develop a robot with high mobility. To achieve this, it was necessary both to reduce the weight of the robot using a 3D processing machine and a 3D molding machine, and to develop a robot with high rigidity. In this paper, a cyclo gear reducer was developed using the rapid prototyping. The cyclo gear reducer has a deceleration ratio of engagement that is two and three times higher than the usual involute gears. Also, the transmission efficiency of the cyclo gear reducer is usually designed to be high, which means that it is usually difficult to achieve precision in gear teeth, such as those of the spur wheel and involute gear of the planetary gear, using resin material. Since the curved shape of the teeth used in an epitrochoid gear are not sharp, the gear and gear box can be made using a simple 3D processing machine even if the material has low rigidity, as in the case of plastics. Furthermore, we are planning to develop the cyclo gear reducer that can semi-continuously change the deceleration ratio by installing the mechanism where the slide moves along the direction of the rotation axis in the epitrochoid gear, as one of the applications of the cyclo gear reducer.
    01/2010; DOI:10.1109/TENCON.2010.5686752
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