Design and Analysis of Helical Teeth Harmonic Drive

This study analyses the energy consumption of an active magnetorheological knee (AMRK) actuator that was designed for transfemoral prostheses. The system was developed as an operational motor unit (MU), which consists of an EC motor, a harmonic drive and a magnetorheological (MR) clutch, that operates in parallel with an MR brake. The dynamic models of the MR brake and MU were used to simulate the system’s energetic expenditure during over-ground walking under three different working conditions: using the complete AMRK; using just its motor-reducer, to operate as a common active knee prosthesis (CAKP), and using just the MR brake, to operate as a common semi-active knee prosthesis (CSAKP). The results are used to compare the MR devices power consumptions with that of the motor-reducer. As previously hypothesized, to use the MR brake in the swing phase is more energetically efficient than using the motor-reducer to drive the joint. Even if using the motor-reducer in regenerative braking mode during the stance phase, the differences in power consumption among the systems are remarkable. The AMRK expended 16.3 J during a gait cycle, which was 1.6 times less than the energy expenditure of the CAKP (26.6 J), whereas the CSAKP required just 6.0 J.

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Output Torque for Electromagnetic Harmonic Drive

Advances in Mechanical Engineering ◽

10.1155/2014/721543 ◽

2014 ◽

Vol 7 (2) ◽

pp. 721543 ◽

Cited By ~ 3

Author(s):

Lizhong Xu ◽

Yongli Liang

Keyword(s):

Harmonic Drive ◽

Output Torque

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

Volume 8: 11th International Power Transmission and Gearing Conference; 13th International Conference on Advanced Vehicle and Tire Technologies ◽

10.1115/detc2011-48849 ◽

2011 ◽

Cited By ~ 1

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.

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Evidence of secondary tooth contact in harmonic drive, with involute toothed gear pair, through experimental and finite element analyses of stresses in flex-gear cup

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406216682541 ◽

2016 ◽

Vol 232 (2) ◽

pp. 341-357 ◽

Cited By ~ 6

Author(s):

Vineet Sahoo ◽

Rathindranath Maiti

Keyword(s):

Finite Element Analysis ◽

Finite Element ◽

Major Axis ◽

Initial Stresses ◽

Gear Pair ◽

Ring Gear ◽

Harmonic Drive ◽

Strain Wave ◽

Element Analysis ◽

Full Load

Stresses in flex spline/gear cup in harmonic drives with involute toothed gear pair and conventional strain wave generating cam are analyzed using finite element method in ANSYS® environment and experiments. The most innovative part of this investigation is establishing the evidence of secondary contacts and probable load shared by those contacts experimentally over the finite element analysis. Aiming at the performance improvement of gearing in harmonic drives, with involute toothed gear pair, the investigations are carried out through the following analyses. (a) Initial stresses in flex gear cup due to cam insertion only. (b) Stresses in flex gear cup at no load in fully assembled harmonic drive components i.e. flex gear, ring gear, and strain wave generating cam. (c) Stresses in flex gear cup at full load passing through the two pitch points, i.e. the intersection points of ring gear pitch circle, flex gear pitch curve, and major axis on both sides. Finally, (d) stresses in flex gear cup at full load distributed over all possible primary and secondary contacts, in proportion to their contact intensities. Recorded strains of the flex-gear cup while the cam being rotated showed very good agreement with the results obtained by finite element analysis with proper modeling of loading.

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