Patent•
The strain wave gearing
24 Sep 2013-
TL;DR: In this paper, ausen verzahnter Verzahnungsbereich (7, 9) werden so verbogen, dass sie elliptische Formen haben, deren Phasen um eine Rotationszentralachse (1a) um 90° gegeneinander verdreht sind.
Abstract: Ein erster und ein zweiter ausen verzahnter Verzahnungsbereich (7, 9) eines Verformungswellgetriebes (1) werden durch einen Wellgenerator (10) in eine elliptische Form verbogen, um in ein erstes bzw. in ein zweites innen verzahntes Zahnrad (2, 4) einzugreifen. Der erste und der zweite ausen verzahnte Verzahnungsbereich (7, 9) werden so verbogen, dass sie elliptische Formen haben, deren Phasen um eine Rotationszentralachse (1a) um 90° gegeneinander verdreht sind. Zwischen dem ersten und dem zweiten ausen verzahnten Verzahnungsbereich (7, 9) ist ein ausen verzahntes Kopplungsverzahnungsbereich (8) ausgebildet, der eine kreisformige Querschnittsform behalt, die sich nicht verbiegt. Der ausen verzahnte Kopplungsverzahnungsbereich (8) wird so auf eingreifende Art und Weise mit einem innen verzahnten Kopplungszahnrad (3) gekoppelt gehalten. Das Verformungswellgetriebe (1) hat eine hohe Eingriffssteifigkeit und ist in der Lage, ein groses Drehmoment zu ubertragen.
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TL;DR: A new approach is taken to model the torsional compliance and hysteresis behavior in harmonic drives by modeling the compliance behavior of the flexspline and the wave generator instead of modeling the individual behaviors of the overall harmonic drive transmission.
Abstract: Nonlinear torsional compliance and hysteresis are associated with harmonic drives, and their accurate modeling is crucial for improving performance of the control system of harmonic drive-based devices such as robot joints. In this paper, a new approach is taken to model the torsional compliance and hysteresis behavior in harmonic drives. The proposed model is derived by modeling the compliance behavior of the flexspline and the wave generator instead of modeling the individual behaviors of the overall harmonic drive transmission. The hysteresis loss is captured by taking the wave generator torsional compliance into account. The proposed model is validated through numerical simulations and subsequently with experimental data.
62 citations
Cites background from "The strain wave gearing"
...HARMONIC drives, invented in 1950s [1], are widely used in servo systems, such as robots, due to their desirable characteristics of near-zero backlash, compactness, light weight, high torque capacity, high gear ratio, and coaxial assembly....
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TL;DR: The use of bulk metallic glasses (BMGs) as the flexspline in strain wave gears (SWGs), also known as harmonic drives, is presented and may significantly reduce the cost of SWGs, enabling lower-cost robotics.
Abstract: The use of bulk metallic glasses (BMGs) as the flexspline in strain wave gears (SWGs), also known as harmonic drives, is presented. SWGs are unique, ultra-precision gearboxes that function through the elastic flexing of a thin-walled cup, called a flexspline. The current research demonstrates that BMGs can be cast at extremely low cost relative to machining and can be implemented into SWGs as an alternative to steel. This approach may significantly reduce the cost of SWGs, enabling lower-cost robotics. The attractive properties of BMGs, such as hardness, elastic limit and yield strength, may also be suitable for extreme environment applications in spacecraft.
60 citations
Cites background from "The strain wave gearing"
...They are (1) a stiff outer spline, also called a circular spline, with internal gear teeth, (2) a thin-walled flexspline with external teeth numbering two less than the outer spline, and (3) an elliptical wave generator with steel ball bearings confined in an elliptical race by a steel band....
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...As such, research in SWGs primarily focuses on how to (1) lower cost, (2) achieve better performance in the intended environment, (3) lower mass, (4) integrate new materials and (5) make smaller drives....
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...Despite this unknown, BMGs exhibit two detracting features for possible use as a replacement for steel in a flexspline: (1) lower fatigue limits than steel and (2) lower fracture toughness than steel16....
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14 Aug 2020
TL;DR: An assessment framework strongly conditioned by HRI applications is proposed, and it is proposed to use virtual power as a suitable way to assess the inherent limitations of a gearbox technologies to achieve high efficiencies.
Abstract: On the eve of Human-Robot-Interaction (HRI) becoming customary in our lives, the performance of HRI robotic devices remains strongly conditioned by their gearboxes. In most industrial robots, two relatively unconventional transmission technologies – Harmonic Drives © and Cycloid Drives – are usually found, which are not so broadly used in other industries. Understanding the origin of this singularity provides valuable insights in the search for suitable, future robotic transmission technologies. In this paper we propose an assessment framework strongly conditioned by HRI applications, and we use it to review the performance of conventional and emerging robotic gearbox technologies, for which the design criterion is strongly shifted towards aspects like weight and efficiency. The framework proposes to use virtual power as a suitable way to assess the inherent limitations of a gearbox technologies to achieve high efficiencies. This paper complements the existing research dealing with the complex interaction between gearbox technologies and the actuators, with a new gearbox-centered perspective particularly focused on HRI applications.
41 citations
Cites methods from "The strain wave gearing"
...The Strain Wave gearbox was invented by Musser (1955) and found broad application in the 70’s, originally in aerospace....
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TL;DR: In order to decrease the force on flex Spline, by means of conjugate method, the parameters of flexspline and circular spline’s tooth profiles are optimized and the meshing characteristics of the tooth pairs with optimized parameters are improved significantly.
Abstract: Considering the fact that load distribution of the flexspline under alternating dynamic loads is complicated, and it’s difficult to measure the stress of the flexspline by experiment, a d ynamic simulation model of harmonic gear drives is established to study the intensity of the flexspline in the operating process of harmonic gear drives based on finite element method. In order to decrease the force on flexspline, by means of conjugate method, the parameters of flexspline and circular spline’s tooth profiles are optimized. A D-100 harmonic drive is simulated based on the contact theory and the explicit algorithm of the finite element method. The parameterized finite element grid of the whole harmonic gear drive model is realized by Matlab, and then the assembly process of the wave generator is simulated by ABAQUS. Meanwhile, the distribution of the flexspline stress and the load characteristics of the flexspline tooth during dynamic transmission process of a harmonic gear with parameters, before and after optimization, are analyzed. The meshing characteristics of the tooth pairs with optimized parameters are improved significantly. The fatigue fracture position on the flexspline is forecasted according to the simulation results.
39 citations
01 Mar 2016
TL;DR: In this article, the authors describe variations in pitch lengths when teeth move on a strain wave geodesic bearing (SWG) on the flex spline of a Flex Spline.
Abstract: Originally fixed and uniform circular pitches of flex spline (FS) teeth of a ‘Strain Wave Gearing’ or ‘Harmonic Drive’ (HD) experience variations in pitch lengths when teeth move on ‘strain wave ge...
20 citations
References
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TL;DR: A new approach is taken to model the torsional compliance and hysteresis behavior in harmonic drives by modeling the compliance behavior of the flexspline and the wave generator instead of modeling the individual behaviors of the overall harmonic drive transmission.
Abstract: Nonlinear torsional compliance and hysteresis are associated with harmonic drives, and their accurate modeling is crucial for improving performance of the control system of harmonic drive-based devices such as robot joints. In this paper, a new approach is taken to model the torsional compliance and hysteresis behavior in harmonic drives. The proposed model is derived by modeling the compliance behavior of the flexspline and the wave generator instead of modeling the individual behaviors of the overall harmonic drive transmission. The hysteresis loss is captured by taking the wave generator torsional compliance into account. The proposed model is validated through numerical simulations and subsequently with experimental data.
62 citations
TL;DR: The use of bulk metallic glasses (BMGs) as the flexspline in strain wave gears (SWGs), also known as harmonic drives, is presented and may significantly reduce the cost of SWGs, enabling lower-cost robotics.
Abstract: The use of bulk metallic glasses (BMGs) as the flexspline in strain wave gears (SWGs), also known as harmonic drives, is presented. SWGs are unique, ultra-precision gearboxes that function through the elastic flexing of a thin-walled cup, called a flexspline. The current research demonstrates that BMGs can be cast at extremely low cost relative to machining and can be implemented into SWGs as an alternative to steel. This approach may significantly reduce the cost of SWGs, enabling lower-cost robotics. The attractive properties of BMGs, such as hardness, elastic limit and yield strength, may also be suitable for extreme environment applications in spacecraft.
60 citations
14 Aug 2020
TL;DR: An assessment framework strongly conditioned by HRI applications is proposed, and it is proposed to use virtual power as a suitable way to assess the inherent limitations of a gearbox technologies to achieve high efficiencies.
Abstract: On the eve of Human-Robot-Interaction (HRI) becoming customary in our lives, the performance of HRI robotic devices remains strongly conditioned by their gearboxes. In most industrial robots, two relatively unconventional transmission technologies – Harmonic Drives © and Cycloid Drives – are usually found, which are not so broadly used in other industries. Understanding the origin of this singularity provides valuable insights in the search for suitable, future robotic transmission technologies. In this paper we propose an assessment framework strongly conditioned by HRI applications, and we use it to review the performance of conventional and emerging robotic gearbox technologies, for which the design criterion is strongly shifted towards aspects like weight and efficiency. The framework proposes to use virtual power as a suitable way to assess the inherent limitations of a gearbox technologies to achieve high efficiencies. This paper complements the existing research dealing with the complex interaction between gearbox technologies and the actuators, with a new gearbox-centered perspective particularly focused on HRI applications.
41 citations
TL;DR: In order to decrease the force on flex Spline, by means of conjugate method, the parameters of flexspline and circular spline’s tooth profiles are optimized and the meshing characteristics of the tooth pairs with optimized parameters are improved significantly.
Abstract: Considering the fact that load distribution of the flexspline under alternating dynamic loads is complicated, and it’s difficult to measure the stress of the flexspline by experiment, a d ynamic simulation model of harmonic gear drives is established to study the intensity of the flexspline in the operating process of harmonic gear drives based on finite element method. In order to decrease the force on flexspline, by means of conjugate method, the parameters of flexspline and circular spline’s tooth profiles are optimized. A D-100 harmonic drive is simulated based on the contact theory and the explicit algorithm of the finite element method. The parameterized finite element grid of the whole harmonic gear drive model is realized by Matlab, and then the assembly process of the wave generator is simulated by ABAQUS. Meanwhile, the distribution of the flexspline stress and the load characteristics of the flexspline tooth during dynamic transmission process of a harmonic gear with parameters, before and after optimization, are analyzed. The meshing characteristics of the tooth pairs with optimized parameters are improved significantly. The fatigue fracture position on the flexspline is forecasted according to the simulation results.
39 citations
01 Jul 2015
TL;DR: The MAGDRIVE project as discussed by the authors proposed a new concept of noncontact interactions among magnets, soft magnetic materials, and superconductors to provide a high reduction ratio gear that smoothly and naturally operates at cryogenic environments.
Abstract: Harmonic drives are profusely used in aerospace mainly because of their compactness and large reduction ratio However, their use in cryogenic environments is still a challenge Lubrication and fatigue are non-trivial issues under these conditions The objective of the Magnetic-Superconductor Cryogenic Non-contact Harmonic Drive (MAGDRIVE) project, funded by the EU Space FP7, is to design, build, and test a new concept of MAGDRIVE Non-contact interactions among magnets, soft magnetic materials, and superconductors are efficiently used to provide a high reduction ratio gear that smoothly and naturally operates at cryogenic environments The limiting elements of conventional harmonic drives (teeth, flexspline, and ball bearings) are substituted by contactless mechanical components (magnetic gear and superconducting magnetic bearings) The absence of contact between moving parts prevents wear, lubricants are no longer required, and the operational lifetime is greatly increased This is the first mechanical reducer in mechanical engineering history without any contact between moving parts In this paper, the test results of a −1:20 inverse reduction ratio MAGDRIVE prototype are reported In these tests, successful operation at 40 K and 10−3 Pa was demonstrated for more than 15 million input cycles A maximum torque of 3 N·m and an efficiency of 80% were demonstrated The maximum tested input speed was 3000 rpm, six times the previous existing record for harmonic drives at cryogenic temperatures
30 citations