The Mechanical Efficiency of Harmonic Drives: A Simplified Model

2020 ◽  
pp. 1-17
Author(s):  
Federico Gravagno ◽  
Victor Mucino ◽  
Ettore Pennestri
Keyword(s):  
Mechanical Efficiency ◽  
Angular Speed ◽  
Gear Train ◽  
Simplified Model ◽  
Significant Feature ◽  
Main Concern ◽  
Harmonic Drive ◽  
Space Applications ◽  
New Model ◽  
Epicyclic Gear

Abstract Harmonic drives are widely used devices in robotic and space applications. As for any device transmitting motion, its mechanical efficiency is one of the main concern for the designer. In this paper it is proposed a new model to estimate this significant feature. The proposed approach makes use of the kinematic correspondence between the harmonic drive and an epicyclic gear train. Although the authors introduced crude approximations to describe the complex tribological phenomena during harmonic drive teeth meshing, the numerical results match the trend of experimental. In particular, assuming the harmonic drive working at the rated torque, the plots of the mechanical efficiency versus different parameters such as temperature and angular speed have been reported.

Cycloid Drives With Machining Tolerances

1989 ◽  
Vol 111 (3) ◽  
pp. 337-344 ◽  
Author(s):  
J. G. Blanche ◽  
D. C. H. Yang
Keyword(s):  
High Efficiency ◽  
Dynamic Instability ◽  
Torque Ripple ◽  
Gear Train ◽  
Space Applications ◽  
Input Shaft ◽  
Epicyclic Gear ◽  
Speed Reducer ◽  
Planet Gear ◽  
Gear Mechanism

The cycloidal speed reducer, or cycloid drive, is an epicyclic gear train in which the profile of the planet gear is an epitrochoid and the annular sun gear has rollers as its teeth. The cycloid drive has very high efficiency and small size, in comparison with a conventional gear mechanism, making it an attractive candidate for limited space applications. On the other hand, in this type of transmissions there exist two major drawbacks, namely, backlash and torque ripple. Backlash, the angle through which the output shaft can rotate when the input shaft is held fixed, has a degrading effect on the output accuracy. Torque ripple, the variation in mechanical advantage as the input shaft rotates, causes vibrations and could lead to dynamic instability of the machinery. If the cycloid drive were manufactured to the ideal dimensions, there would be no backlash nor torque ripple. However, in reality, there will always be some machining tolerances. In this paper an analytical model is developed which models the cycloid drive with machining tolerances. Consequently, the effect of machining tolerances on backlash and torque ripple are investigated. It is found that both the backlash and the torque ripple are inherent periodic functions of the input crank angle.

Cycloid Drives With Machining Tolerances: Part I — Kinematic Analysis

1987 ◽  
Author(s):  
J. G. Blanche ◽  
D. C. H. Yang
Keyword(s):  
High Efficiency ◽  
Dynamic Instability ◽  
Torque Ripple ◽  
Gear Train ◽  
Space Applications ◽  
Design Synthesis ◽  
Input Shaft ◽  
Epicyclic Gear ◽  
Speed Reducer ◽  
Gear Mechanism

Abstract The cycloidal speed reducer, or cycloid drive, is an epicyclic gear train in which the profile of the planet gear is an epitrochoid and the annular sun gear has rollers as its teeth. The cycloid drive has very high efficiency and small size, in comparison with a conventional gear mechanism, making it an attractive candidate for limited space applications. On the other hand, in this type of transmissions there exist two major drawbacks, namely, backlash and torque ripple Backlash, the angle through which the output shaft can rotate when the input shaft is held fixed, has a degrading effect on the output accuracy. Torque ripple, the variation in mechanical advantage as the input shaft rotates, causes vibrations and could lead to dynamic instability of the machinery. If the cycloid drive were manufactured to the ideal dimensions, there would be no backlash nor torque ripple. However, in reality, there will always be some machining tolerances. In this paper an analytical model is developed which models the cycloid drive with machining tolerances. This model is used in Part II of this investigation to determine the effect of machining tolerances on backlash and torque ripple. As a result, simple and practical equations for design synthesis of this type of drives are formulated.

scholarly journals Mechanical Efficiency of HMCVT under Steady-State Conditions

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Guangqing Zhang ◽  
Hengtong Zhang ◽  
Yanyan Ge ◽  
Wei Qiu ◽  
Maohua Xiao ◽  
...  
Keyword(s):  
Steady State ◽  
Mechanical System ◽  
Hydraulic System ◽  
Power Flow ◽  
Ride Comfort ◽  
Mechanical Efficiency ◽  
Gear Train ◽  
Epicyclic Gear ◽  
Physical Prototype ◽  
Variable Transmission

Hydromechanical continuously variable transmission (HMCVT) technology has been widely used due to its advantages of ride comfort and fuel economy. The relatively uniform efficiency expression of HMCVT is obtained by studying torque and transmission ratios to reveal steady-state characteristics and predict the output torque. Mathematical models of torque ratios are derived by analyzing the HMCVT system power flow and calculating the equivalent meshing power of epicyclic gear train and efficiency for the hydraulic system. The relationship between mechanical system transmission and hydraulic system parameters is established using the torque ratios, and a mechanical system demanding surface is proposed. Two numerical examples of the HMCVT system with single and dual variable units are demonstrated to establish an effective and convenient method. The method is validated through a physical prototype TA1-02 test.

Mechanical Efficiency Analysis of a 16-Speed Bicycle Transmission Hub

2013 ◽  
Vol 284-287 ◽  
pp. 810-814 ◽  
Author(s):  
Yi Chang Wu ◽  
Pei Wun Ren
Keyword(s):  
Analytical Method ◽  
Power Flow ◽  
Planetary Gear ◽  
Mechanical Efficiency ◽  
Angular Speed ◽  
Efficiency Analysis ◽  
Gear Train ◽  
Flow Diagram ◽  
Gear Mesh ◽  
Analysis Process

This paper proposes an analytical method to evaluate the mechanical efficiency of the bicycle transmission hub. A 16-speed transmission hub, which consists of two transmission units and one differential unit, is presented first. By applying the concept of fundamental circuits, a step by step analysis process is then described to numerically calculate the angular speed, ideal torque and power flow, and actual torque and power flow by considering the gear-mesh loss of each link of the planetary gear train. Based on the power flow diagram, the mechanical efficiency at each speed of the transmission hub can be estimated.

A review of graph theory application research in gears

2015 ◽  
Vol 230 (10) ◽  
pp. 1697-1714 ◽  
Author(s):  
Hui-Ling Xue ◽  
Geng Liu ◽  
Xiao-Hui Yang
Keyword(s):  
Graph Theory ◽  
Power Flow ◽  
Planetary Gear ◽  
Mechanical Efficiency ◽  
Gear Train ◽  
Synthesis Process ◽  
Epicyclic Gear ◽  
Analysis And Synthesis ◽  
Theory Application ◽  
Gear Trains

Graph theory has been applied to gear train analysis and synthesis for many years, and it is an effective and systematic modeling approach in the design process of gear transmission. Based on more than 100 references listed in this paper, a review about the graph-based method for kinematic and static force analysis, power flow, and mechanical efficiency computation is presented. The method is based on the concept of fundamental circuit corresponding to a basic epicyclic gear train. A 1-dof epicyclic gear train and a two-stage planetary gear train are used to illustrate the application of this method. Besides, isomorphism identification in the synthesis process and enumeration of 1-dof epicyclic gear train graphs are surveyed particularly. Also, the computerized methods for detection of redundant gears and degenerate structures in epicyclic gear trains are reviewed, respectively.

A New Concept of High-Performance Marine Reversing Reduction Gears

1988 ◽  
Vol 110 (4) ◽  
pp. 572-577
Author(s):  
D. J. Folenta
Keyword(s):  
Gas Turbine ◽  
High Performance ◽  
Power Transmission ◽  
High Reliability ◽  
Mechanical Efficiency ◽  
Gas Turbine Engine ◽  
Turbine Engines ◽  
Turbine Engine ◽  
Epicyclic Gear ◽  
Gear Technology

This paper presents a brief description and several illustrations of a new concept of marine reversing gears that utilize high-performance differentially driven epicyclic gear arrangements. This new marine power transmission has the potential to offer high reliability, simplicity, light weight, high mechanical efficiency, compactness, and technological compatibility with aircraft derivative marine gas turbine engines. Further, this new reversing gear minimizes the danger of driving the free turbine in reverse as might be the case with conventional parallel shaft reversing gear arrangements. To illustrate the weight reduction potential, a modern naval ship propulsion system utilizing an aircraft derivative gas turbine engine as the prime mover in conjunction with a conventional parallel shaft reversing gear can be compared to the subject reversing gear differential. A typical 18,642 kW (25,000 hp) marine gas turbine engine might weigh approximately 5000 kg (11,000 lb) and a conventional marine technology parallel shaft reversing gear might weigh on the order of 90,000 to 136,000 kg (200,000 to 300,000 lb). Using gear technology derived from the aircraft industry, a functionally similar differentially driven marine reversing gear might weigh approximately 13,600 kg (30,000 lb).

Topological Synthesis of Epicyclic Gear Trains Using Vertex Incidence Polynomial

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Vinjamuri Venkata Kamesh ◽  
Kuchibhotla Mallikarjuna Rao ◽  
Annambhotla Balaji Srinivasa Rao
Keyword(s):  
High Velocity ◽  
Mechanical Energy ◽  
Gear Train ◽  
Recursive Method ◽  
Gear Pair ◽  
Simple Method ◽  
Epicyclic Gear ◽  
Thick Line ◽  
Gear Trains ◽  
Isomorphic Graphs

Epicyclic gear trains (EGTs) are used in the mechanical energy transmission systems where high velocity ratios are needed in a compact space. It is necessary to eliminate duplicate structures in the initial stages of enumeration. In this paper, a novel and simple method is proposed using a parameter, Vertex Incidence Polynomial (VIP), to synthesize epicyclic gear trains up to six links eliminating all isomorphic gear trains. Each epicyclic gear train is represented as a graph by denoting gear pair with thick line and transfer pair with thin line. All the permissible graphs of epicyclic gear trains from the fundamental principles are generated by the recursive method. Isomorphic graphs are identified by calculating VIP. Another parameter “Rotation Index” (RI) is proposed to detect rotational isomorphism. It is found that there are six nonisomorphic rotation graphs for five-link one degree-of-freedom (1-DOF) and 26 graphs for six-link 1-DOF EGTs from which all the nonisomorphic displacement graphs can be derived by adding the transfer vertices for each combination. The proposed method proved to be successful in clustering all the isomorphic structures into a group, which in turn checked for rotational isomorphism. This method is very easy to understand and allows performing isomorphism test in epicyclic gear trains.

Design of an Epicyclic Transmission for Speed Control of a Turbine-Generator System

1992 ◽  
Author(s):  
Indranil Barman ◽  
Donald R. Flugrad
Keyword(s):  
Control Method ◽  
Equations Of Motion ◽  
Speed Control ◽  
Gear Train ◽  
Turbine Generator ◽  
Generator System ◽  
Epicyclic Gear ◽  
The Face ◽  
Fine Control ◽  
Parameter Values

Abstract An improved speed control method is proposed for a turbine-generator system. Whereas the present method employs a steam valve to control the flow of steam according to the desired output, the proposed system uses an epicyclic gear train to provide fine control of the speed, while coarse control is still maintained through the steam valve. The systematic design of such a gear train is the objective of this project. Two configurations are considered as suitable candidates. After the transmissions are analyzed to obtain the speed and torque relations, the dynamic equations of motion and control equations for the systems are derived for simulation purposes. The simulations are then conducted for various load cases and parameter values to determine a suitable design for application in the power industry. The final configuration allows constant generator output speeds to be reliably maintained in the face of significant load disturbances.

Meshing Efficiency Analysis of Two Degree-of-Freedom Epicyclic Gear Trains

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Essam Lauibi Esmail
Keyword(s):  
Reference Frame ◽  
Power Efficiency ◽  
Power Flow ◽  
Flow Direction ◽  
Efficiency Analysis ◽  
Degree Of Freedom ◽  
Gear Train ◽  
Epicyclic Gear ◽  
Gear Trains ◽  
Two Degree Of Freedom

The concept of potential power efficiency is introduced as the efficiency of an epicyclic gear train (EGT) measured in any moving reference frame. The conventional efficiency can be computed in a carrier-moving reference frame in which the gear carrier appears relatively fixed. In principle, by attaching the reference frame to an appropriate link, torques can be calculated with respect to each input, output, or (relatively) fixed link in the EGT. Once the power flow direction is obtained from the potential power ratio, the torque ratios are obtained from the potential power efficiencies, the particular expression of the efficiency of the EGT is found in a simple manner. A systematic methodology for the efficiency analysis of one and two degree-of-freedom (DOF) EGTs is described, and 14 ready-to-use efficiency formulas are derived for 2DOF gear pair entities (GPEs). This paper includes also a discussion on the redundancy of the efficiency formulas used for 1DOF GPEs. An incomplete in the efficiency formulas in previous literature, which make them susceptible to wrong application, is brought to light.

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