A Novel Harmonic Drive With Pure Involute Tooth Gear Pair

2004 ◽  
Vol 126 (1) ◽  
pp. 178-182 ◽  
Author(s):  
Rathindranath Maiti
Keyword(s):  
New Wave ◽  
Harmonic Drive ◽  
Tooth Gear ◽  
Circular Arcs ◽  
Wave Generator ◽  
Involute Gears ◽  
Cam Profile ◽  
Pitch Curve ◽  
Engagement And Disengagement ◽  
Circular Pitch

Consider commercially available “harmonic drives” or “strain wave gearings” (all patented designs). The tooth profiles of the mating pairs of teeth of the noncircular (pitch curve) flex gear and circular (pitch circle) ring gears are nearly conjugate and noninvolute. Evidently none of them offers ideal gear kinematics. In this paper, we propose a new wave generator (or cam) to drive flex gears of harmonic drives with fully conjugate gear pairs of purely involute profiles. The cam profile is made of circular arcs at the two diametrically opposite contact zones and shifted elliptical curves for the other two zones. The geometric construction is done in such a way that tip interference is properly avoided for both engagement and disengagement with nominally stubbed or full depth tooth involute gears. We develop the theory of geometric and gearing conditions. We have also built a physical model in order to verify the geometry of tooth interference and other relevant gearing kinematics.

A Wave Generator of New Concept for Flex Gear of Harmonic Drive With Pure Involute Tooth Gear Pairs

2000 ◽  
Author(s):  
R. Maiti ◽  
A. K. Roy
Keyword(s):  
New Wave ◽  
Harmonic Drive ◽  
Tooth Gear ◽  
Circular Arcs ◽  
Wave Generator ◽  
Accurate Performance ◽  
Involute Gears ◽  
Cam Profile ◽  
Engagement And Disengagement ◽  
Made In

Abstract A new wave generator (or cam) is proposed (Maiti, Patent 1995) to drive the flex gear of strain wave gearing i.e., harmonic drives with gear pairs of pure involute profiles. The cam profile is made of circular arcs at the two contact zones and shifted elliptical curves for the other zones. The geometric constniction is made in such a way that tip interference is properly avoided for both engagement and disengagement with nominally stubbed or full depth involute gears. The theories are established to verify other geometric and gearing conditions. Evidently, in the existing products (all are patented design) the profiles are non-involute and none of them offers ideal gear kinematics. It is expected that this new harmonic drive will offer the best gearing kinematics and will have desired accurate performance.

Design and development of strain wave generating cam for a new concept ‘harmonic drive’

2012 ◽  
Vol 227 (8) ◽  
pp. 1870-1884 ◽  
Author(s):  
Rathindranath Maiti ◽  
Indraneel Biswas ◽  
Vivek Nema ◽  
Saurabh Basu ◽  
Bhabani Sankar Mahanto ◽  
...  
Keyword(s):  
Harmonic Drive ◽  
Strain Wave ◽  
Assembly Method ◽  
Circular Arcs ◽  
Single Piece ◽  
Cam Profile ◽  
Active Zones ◽  
Gear Contact ◽  
Inner Race ◽  
Center Distance

A split cam design is proposed to solve the problem of assembly of the single piece cam in the flexible raced bearing of an earlier proposed novel harmonic drive system, which shows better torque characteristics and capacities in comparison to the conventional one of same size with oval-shaped strain wave generating cam. The cam profile has circular arcs at two working zones at 180° phases. The proposed profile shape is identified as the cause of trouble in assembly if the cam is made single piece. The split cam is made of two identical pieces having circular arc edges. These pieces constitute the cam in assembly after putting it inside the inner race of the flex bearing and adjusted by an adjuster. The design, kinematics, and the assembly method of the proposed split cam are presented in this article. The split cam arrangement not only solves the assembly problem but also gives a scope of fine adjustment of center distance (eccentricity). Such an adjustment is not possible in conventional oval wave generating cam. Stresses in flex gear cups assembled with both type cams at load and no-load conditions are estimated using finite element method. Some results are verified experimentally. Although the flex gear cup with the proposed split cam experiences lower stresses at load transmitting active gear contact zones, it shows higher stresses at some non-active zones (where teeth are free of load). It is apparent from results that stresses at those non-active zones do not increase substantially with the increase in torque, as they are away from active zones.

On a Gearing Problem in Conventional Harmonic Drives With Involute Toothed Gear Set

2011 ◽  
Author(s):  
Bikash Routh ◽  
Rathindranath Maiti
Keyword(s):  
Applied Load ◽  
Harmonic Drive ◽  
Strain Wave ◽  
Base Circle ◽  
Pitch Curve

Circular pitches of flex spline teeth of a ‘Strain Wave Gearing’, also known as a ‘Harmonic Drive’, are deformed when the Strain Wave Generating Cam is inserted into the flex spline cup. In the present work the deformed pitch distances considering that flex spline teeth remain rigid while the rim deforms, are estimated. No applied load is considered. It is also shown that if the cam is elliptical then the pitch curve is not an ellipse and vice versa. Geometries of such curves can be defined following the analysis presented in this paper. Cases of both undeformed flex spline with circular spline and deformed flex spline with circular spline, with involute teeth, are considered to find out tooth positions. Geometries of involute teeth profiles in mesh are examined and compared considering oval shaped (on deformation) base drum of flex spline where as base circle of circular spline remained circular.

Spline Based Design of Cam Contours for Improved Dynamic Performance

1993 ◽  
Author(s):  
Holly K. Ault ◽  
James C. Wilkinson
Keyword(s):  
Dynamic Performance ◽  
Integrated Design ◽  
Polynomial Functions ◽  
Piecewise Polynomial ◽  
Cam Design ◽  
Piecewise Polynomial Functions ◽  
Cam Follower ◽  
Cam Profile ◽  
Pitch Curve ◽  
Design And Manufacture

Abstract A method for the integrated design and manufacture of radial plate cams is discussed. Currently, a cam-follower system is designed by specifying constraints on the motion of the follower. The physical cam contour or cam pitch curve are not mathematically defined. The cam is manufactured from the discretized follower motion program. A new method for cam design is proposed which will produce a smooth, mathematically defined cam pitch curve while maintaining the proper constraints on the follower motion. Piecewise polynomial functions in the form of rational and/or non-rational splines may be used. Cams will be manufactured using smoothed profiles and tested for improved dynamic performance. The results of initial investigations of cam profile design for this research are presented.

scholarly journals Loop-Type Wave-Generation Method for Generating Wind Waves under Long-Fetch Conditions

2017 ◽  
Vol 34 (10) ◽  
pp. 2129-2139 ◽  
Author(s):  
Naohisa Takagaki ◽  
Satoru Komori ◽  
Mizuki Ishida ◽  
Koji Iwano ◽  
Ryoichi Kurose ◽  
...  
Keyword(s):  
Wind Wave ◽  
Wind Waves ◽  
Peak Frequency ◽  
Wave Generation ◽  
New Wave ◽  
Wave Tank ◽  
Irregular Wave ◽  
Wind Speeds ◽  
Type Wave ◽  
Wave Generator

AbstractIt is important to develop a wave-generation method for extending the fetch in laboratory experiments, because previous laboratory studies were limited to the fetch shorter than several dozen meters. A new wave-generation method is proposed for generating wind waves under long-fetch conditions in a wind-wave tank, using a programmable irregular-wave generator. This new method is named a loop-type wave-generation method (LTWGM), because the waves with wave characteristics close to the wind waves measured at the end of the tank are reproduced at the entrance of the tank by the programmable irregular-wave generator and the mechanical wave generation is repeated at the entrance in order to increase the fetch. Water-level fluctuation is measured at both normal and extremely high wind speeds using resistance-type wave gauges. The results show that, at both wind speeds, LTWGM can produce wind waves with long fetches exceeding the length of the wind-wave tank. It is observed that the spectrum of wind waves with a long fetch reproduced by a wave generator is consistent with that of pure wind-driven waves without a wave generator. The fetch laws between the significant wave height and the peak frequency are also confirmed for the wind waves under long-fetch conditions. This implies that the ideal wind waves under long-fetch conditions can be reproduced using LTWGM with the programmable irregular-wave generator.

Study on Meshing Characteristic and CAM Technology of Eccentric Involute Gears

2012 ◽  
Vol 479-481 ◽  
pp. 917-920
Author(s):  
Yong Ping Liu ◽  
Peng Fei Meng ◽  
Chi Bing Hu
Keyword(s):  
Design Method ◽  
Shape Design ◽  
Digital Manufacturing ◽  
Transmission Characteristics ◽  
Systemic Theory ◽  
Theoretical Design ◽  
Parameterized Modeling ◽  
Involute Gears ◽  
Noncircular Gears ◽  
Pitch Curve

According to the meshing principle of noncircular gears, the meshing characteristic and digital manufacturing technology of eccentric involute gears is studied. Based on analyzing the parameterized modeling of pitch curve, transmission characteristics and convex-concave property on eccentric involute gears, the transmission feasibility of this type gear is proved. Through tooth shape design, CAM calculation and processing simulation, the validity and manufacturability of theoretical design method on this type gear is proved. The research results can provide more systemic theory basis for the design, manufacture, measure and application of eccentric involute gears.

Loaded Tooth Contact Pattern Analysis for Strain Wave Gear With Non-Elliptical Wave Generator

2019 ◽  
Author(s):  
Zhiyuan Yu
Keyword(s):  
Finite Element ◽  
Pattern Analysis ◽  
Element Model ◽  
Tooth Surface ◽  
New Wave ◽  
Contact Pattern ◽  
Strain Wave ◽  
Tooth Contact Analysis ◽  
Tooth Contact ◽  
Wave Generator

Abstract This paper presents a new non-elliptical wave generator for strain wave gear to improve its contact pattern quality. The new wave generator has a polynomial profile at one cross section, then crowned along the lead direction. The lead crowning uses a parabolic function with crowning amount controlled by parabolic coefficient. Loaded tooth contact pattern analysis based on finite element method is used to evaluate the new design. The result shows that the new design will avoid the edge contact between wave generator and flexspline, which reduces contact pressure and improve the wearing life of the gear. It also improves the contact pattern quality of the tooth surface. Comparing with elliptical wave generator, the new wave generator with polynomial profile and lead parabolic crowned surface offers more design freedom to improve strain wave gear’s performance. The parametric equation of the new wave generator is defined intuitively, and it can be easily adapted for any type of strain wave gear. Furthermore, the finite element model for the strain wave gear is a new development and application for Loaded Tooth Contact Analysis (LTCA).

scholarly journals Cylindrical Gears with Changing Ratio

2017 ◽  
Vol 61 (2) ◽  
pp. 130
Author(s):  
András Bendefy ◽  
Péter Horák
Keyword(s):  
Cylindrical Geometry ◽  
Cylindrical Gear ◽  
Cylindrical Gears ◽  
Additional Costs ◽  
Pitch Curve ◽  
Circular Pitch

Changing ratio gears are noncircular. It means that if they are combined with a conventional cylindrical gear a changing axis distance will be given. Changing axis distance can generate a lot of difficulties and additional costs in the construction. Our goal was to create changing ratio gears that have cylindrical geometry and interlock with conventional cylindrical gears at a constant axis distance. This can be achieved by applying continuously changing profile shift. Profile shift modifies the diameter of the gears, however it does not have any effect on the ratio; regardless if that is constant or changing. The point of our calculation is that some gears with noncircular rolling curves can have circular pitch curve with the help of changing profile shift.

Synthesis of Stationary Cams

1999 ◽  
Vol 121 (1) ◽  
pp. 169-172 ◽  
Author(s):  
L.-I. Wu ◽  
P.-H. Fang
Keyword(s):  
Design Process ◽  
Transition Curve ◽  
Gradual Change ◽  
Tool Magazine ◽  
Cam Design ◽  
Circular Arcs ◽  
Automatic Tool ◽  
Pitch Curve ◽  
Straight Lines ◽  
Transition Curves

This paper presents a method for designing stationary cams with constant speed roller followers. A stationary cam is immovable, but it guides its follower to produce a desired motion with the follower being driven by other links. In order to avoid infinite jerk of the follower motion, the pitch curve of a stationary cam should consist of pieces of transition curve, which provide gradual change in curvature and are interposed between straight lines and circular arcs. The general parametric equations of transition curves are derived and the cam design process is demonstrated. This method is applicable for designing the guideways of tool magazine in automatic tool-changing system of the machine center.

Deformation of Flexspline under Transmission Force in Harmonic Drive

2010 ◽  
Vol 97-101 ◽  
pp. 3536-3539 ◽  
Author(s):  
Xiao Xia Chen ◽  
Shu Zhong Lin ◽  
Jing Zhong Xing
Keyword(s):  
Elastic Deformation ◽  
Shell Element ◽  
Beam Element ◽  
Tangential Displacement ◽  
Harmonic Drive ◽  
Ansys Software ◽  
Neutral Layer ◽  
Experimental Distribution ◽  
Wave Generator ◽  
Tangential Forces

Method to investigate the elastic deformation of a flexspline in harmonic driver was developed under assembly force from wave generator and transmission force. Shell element and tapered beam element were applied to model the flexspline cone and the teeth on the flexspline respectively. Forced displacement of the flexspline in assembly state was imposed by contact analysis between the flexspline and wave generator. According to experimental distribution of tangential forces in transmission state, applying forces at the teeth tips on the flexspline in mesh state, deformation distribution under transmission torque loading was obtained. Simulations of assembly state and transmission state were realized in ANSYS software. In three sections of tooth ring vertical to the axis, the deformation distributions of the flexspline under specified displacement in assembly state were compared with the theory results. Deformation between tip of tooth and neutral layer in assembly state and in transmission state were compared respectively. The deformation results agreed well with the theory results in assembly state, while difference was found in tangential displacement on tooth tips in transmission state, which may influence mesh property evidently under transmission loading.

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