Draft:Open-Source Leg: Difference between revisions

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{{Infobox software

{{Infobox software

| name = Open-Source Leg

| name = Open-Source Leg

| title = Open-Source Leg

| caption = Modular robotic prosthetic leg platform

| developer = University of Michigan Neurobionics Lab (PI: [[Elliott J. Rouse]])

| developer Elliott J. Rouse

| released = {{Start date and age|2019|8}}

| released = {{Start date||}}

| latest_release_version = 2.5

| latest_release_version = 2.5

| latest_release_date = {{Start date and age|2024|7}}

| latest_release_date = {{Start date|2024|}}

| programming_language = [[Python (programming language)|Python]], [[C (programming language)|C]]

| programming_language Python, C

| operating_system = [[Linux]], [[Robot Operating System|ROS 2]]

| operating_system = Linux, ROS 2

| license = [[GNU General Public License|GPLv3]]

| license GPLv3

| website = {{URL|https://opensourceleg.org}}

| website = https://opensourceleg.org

| repo = {{URL|https://github.com/neurobionics/opensourceleg}}

| repo = https://github.com/neurobionics/opensourceleg

}}

}}

The ”’Open-Source Leg”’ (OSL) is an [[open-source hardware|open-source]] robotic prosthetic platform designed for research in lower-limb prosthetics. The system, developed by the University of Michigan Neurobionics Lab in collaboration with clinical and industry partners, provides standardized hardware, control software, and comprehensive documentation for the study and development of powered prosthetic legs.<ref name=”Nature2020″/><ref name=”UMnews2019“/>

The ”’Open-Source Leg”’ (OSL) is an open-source robotic designed for research in , , , software and .<ref name=””/>

The first scientific description of the system appeared in 2020 in ”Nature Biomedical Engineering”, which detailed the OSL’s mechanical design, sensing systems, control structure, and initial clinical evaluation.<ref name=”Azocar2020″/> The project has received coverage from international media, including ”Economy Chosun”, which highlighted the platform’s potential to standardize prosthetic research and expand access to experimental bionic technology.<ref name=”Chosun2025″/> Development has been supported by multiple awards from the U.S. National Science Foundation.<ref name=”NSF1734586″/><ref name=”NRI2020″/><ref name=”POSE1″/><ref name=”POSE2″/>

== History ==

== History ==

The OSL originated under NSF National Robotics Initiative award ”’#1734586”’ (2017–2020), which supported foundational development of the mechanical hardware, embedded control electronics, sensing integration, and open-source dissemination.<ref name=”NSF1734586″/> A University of Michigan news release introduced the system publicly in 2019.<ref name=”UMnews2019″/>

The project was initiated in 2017 at the University of Michigan and supported by U.S. National Science Foundation grants.<ref name=”NSF1734586″/> Its first public release in 2019 delivered open hardware and software designed to support comparative prosthetics research.<ref name=”UMnews2019″/> Early development involved collaboration with the Shirley Ryan AbilityLab and focused on enabling fair benchmarking of control strategies across research labs.<ref name=”Nature2020″/>

The platform’s first peer-reviewed scientific description was published in 2020 in ”Nature Biomedical Engineering”, presenting detailed schematics, actuator characterization, sensing architecture, and clinical testing results.<ref name=”Azocar2020″/>

Subsequent work led to community adoption, with over ten academic and clinical institutions using the platform for prosthetics research by 2021.<ref name=”Humotech2021″/> The project later partnered with Humotech, a wearable robotics company, to make professionally assembled units available to laboratories.<ref name=”Humotech2021″/>

Between 2020 and 2022, the NSF NRI:INT collaborative research award ”’#2024237”’ supported development of continuous-torque control methods, benchmarking protocols, and multi-laboratory controller evaluation.<ref name=”NRI2020″/>

In 2024, the University of Michigan Robotics Department reported on ecosystem-building efforts for the OSL, including open-source governance, documentation development, community infrastructure, and partnerships with external laboratories.<ref name=”UMRobotics2024″/>

The project continues under the NSF Pathways to Open-Source Ecosystems (POSE) program:

* ”’POSE Phase I – #2229418 (2022–2023)”’ – governance, documentation systems, and contributor pathways.<ref name=”POSE1″/>

* ”’POSE Phase II – #2315895 (2023–2026)”’ – sustainability planning, onboarding tools, safety documentation, and long-term ecosystem maintenance.<ref name=”POSE2″/>

The platform has been adopted by research groups in North America and Europe, including clinical partners such as the Shirley Ryan AbilityLab (SRALab).<ref name=”SRALab2023″/>

== Design ==

== Design ==

=== Hardware ===

=== Hardware ===

The OSL consists of modular knee and ankle joints utilizing high-torque, drone-derived motors, belt-drive transmissions, and configurable series elasticity.<ref name=”Nature2020“/><ref name=”NeurobionicsLab”/> Mechanically, both joints are designed to be nearly identical for ease of assembly and repair. The platform weighs under 6 kg when fully assembled and features replaceable components, enabling rapid prototyping and modification.<ref name=”Nature2020″/>

The OSL consists of modular knee and ankle joints , and .<ref name=””/> for and .

The joints employ low-ratio belt transmissions to increase backdrivability and reduce passive impedance. The ankle uses a two-stage reduction, while the knee uses a configurable single- or dual-stage design.<ref name=”Azocar2020″/>

Sensing systems include integrated load cells, inertial measurement units, optical encoders, and a six-channel data acquisition board.<ref name=”Nature2020″/><ref name=”UMInvention2025″/> Power is supplied by a lithium-ion battery capable of untethered operation for more than two hours.<ref name=”Nature2020″/>

A selectable series elastic element can be included in the drivetrain, providing tunable joint stiffness for experimental investigation. Best et al. (2024) characterized torsion-based elastic actuation strategies compatible with the OSL’s modular architecture.<ref name=”Best2024″/>

Integrated sensing includes:

* magnetic encoders for joint and motor position

* multi-axis load cells for torque or ground-reaction force estimation

* inertial measurement units (IMUs) for segment kinematics

* temperature, voltage, and current sensors for actuator protection

The electronics platform includes a six-channel data acquisition system, high-frequency analog sampling, and digital communication for real-time motor control. Shetty et al. (2022) used the sensing and electronics architecture to conduct actuator system identification and evaluation of torque dynamics.<ref name=”Shetty2022″/>

The assembled system weighs under 6 kg and uses machined aluminum components with standardized mounting points. It supports tethered bench testing and untethered battery-powered locomotion.<ref name=”Azocar2020″/>

=== Software ===

=== Software ===

The OSL software includes embedded firmware, mid-level joint controllers, and high-level Python interfaces for experiment scripting.<ref name=”RouseSoftware”/>

The software library is written in Python and C, with compatibility for ROS 2. The architecture supports voltage, position, current, and impedance control modes. Developers can access Python-based gait analysis tools, automated Robot-CI testing, and collaborative CAD resources hosted on Onshape.<ref name=”Nature2020″/><ref name=”NeurobionicsLab”/>

Embedded firmware manages:

== Applications ==

* motor voltage and current control

The system is primarily used in research settings to benchmark control algorithms, machine learning approaches for gait prediction, human biomechanics, and rehabilitation robotics.<ref name=”Nature2020″/><ref name=”Rouse2022″/> Several studies have employed the OSL platform to conduct direct comparisons of control strategies for powered prostheses.<ref name=”Nature2020″/>

* encoder and load-cell sampling

* sensor fusion and filtering

* motor-driver communication

* safety monitoring and watchdog functions

Mid-level controllers implement:

== Community and Adoption ==

* voltage control

Since its release, the Open-Source Leg has been adopted by research groups internationally. Labs in the United States and Europe have used the platform for studies and clinical validation.<ref name=”Humotech2021″/><ref name=”NeurobionicsLab”/> Publications on OSL have appeared in journals including ”Nature Biomedical Engineering” and the ”IEEE Transactions on Biomedical Engineering”, and the project has received continued support from the National Science Foundation.<ref name=”Nature2020″/><ref name=”Rouse2022″/>

* current (torque) control

* position control

* impedance control for biological stiffness and damping emulation

The continuous-torque controller framework developed under NSF award #2024237 supports smooth transitions between gait phases and works with finite-state machine controllers and adaptive impedance strategies.<ref name=”NRI2020″/>

== See also ==

The Python API offers:

[[Open-source hardware]]

* gait event detection

* parameter tuning

* real-time data logging

* visualization and debugging utilities

* ROS 2 integration

Research by Harris et al. (2024) and Bolívar-Nieto et al. (2021) evaluated prosthesis control methods—such as torque-based and impedance-based strategies—that are compatible with the OSL’s control and sensing architecture.<ref name=”Harris2024″/><ref name=”Bolivar2021″/>

[[Prosthesis]]

Software releases are distributed through GitHub and PyPI with automated testing for reproducibility.<ref name=”RouseSoftware”/>

[[Assistive technology]]

== Research use ==

[[Rehabilitation robotics]]

The OSL is cited in research involving prosthesis control evaluation, gait biomechanics, and robotic actuation. Publications using methodologies compatible with the OSL architecture include:

* Best et al. (2024) – evaluation of torsion-based elastic actuation methods relevant to modular prosthesis actuation.<ref name=”Best2024″/>

* Harris et al. (2024) – assessment of knee–ankle control strategies, including impedance-based approaches.<ref name=”Harris2024″/>

* Bolívar-Nieto et al. (2021) – modeling and control of impedance-based prosthesis controllers.<ref name=”Bolivar2021″/>

* Shetty et al. (2022) – actuator system identification using sensing and electronics architectures compatible with OSL hardware.<ref name=”Shetty2022″/>

== Community and adoption ==

The OSL ecosystem includes CAD models, electronics schematics, firmware, control libraries, documentation, and community-support resources. A public forum facilitates discussion and troubleshooting. Research groups internationally use the platform for gait biomechanics, prosthetic control, and wearable robotics research.

In 2021, Humotech partnered with the project to offer assembled OSL units for laboratories without in-house fabrication capabilities.<ref name=”Humotech2021″/>

== See also ==

* [[Open-source hardware]]

* [[Prosthesis]]

* [[Bionics]]

* [[Rehabilitation robotics]]

* [[Assistive technology]]

== References ==

== References ==

{{reflist|refs=

{{reflist|refs=

<ref name=”Nature2020″>{{cite journal |last1=Azocar |first1=AF |last2=Rouse |first2=EJ |year=2020 |title=Design and clinical implementation of an open-source bionic leg |journal=Nature Biomedical Engineering |volume=4 |issue=10 |pages=941–953 |doi=10.1038/s41551-020-00619-3 |pmid=33020601 |pmc=7581510 }}</ref>

<ref name=”UMnews2019″>{{cite news |title=Open-source bionic leg: First-of-its-kind platform aims to rapidly advance prosthetics |work=University of Michigan News |date=2019-06-04 |url=https://news.umich.edu/open-source-bionic-leg-first-of-its-kind-platform-aims-to-rapidly-advance-prosthetics/}}</ref>

<ref name=”Humotech2021″>{{cite web |date=2021-12-16 |title=U-M, Humotech partner to bring open-source bionic leg to research labs |website=Humotech |url=https://humotech.com/press-release-u-m-humotech-partner-to-bring-open-source-bionic-leg-to-research-labs/}}</ref>

<ref name=”NeurobionicsLab”>{{cite web |title=Open Source Leg |website=Neurobionics Lab – University of Michigan |url=https://neurobionics.robotics.umich.edu/research/wearable-robotics/open-source-leg/}}</ref>

<ref name=”NSF1734586″>{{cite web |title=NSF Award 1734586 – NRI: An Open-Source Robotic Leg Platform that Lowers the Barrier for Advanced Prosthetics Research |website=NSF.gov |url=https://www.nsf.gov/awardsearch/showAward?AWD_ID=1734586}}</ref>

<ref name=”UMInvention2025″>{{cite web |title=OSL Electronics: Data Acquisition Board – 2025-438 |website=University of Michigan Tech Transfer |url=https://available-inventions.umich.edu/product/osl-electronics}}</ref>

<ref name=”Rouse2022″>{{cite journal |last1=Rouse |first1=EJ |last2=Hargrove |first2=LJ |year=2022 |title=Open-Source Leg: A Platform for Collaborative Prosthetic Research |journal=IEEE Transactions on Medical Robotics and Bionics |volume=4 |issue=2 |pages=309–320 |doi=10.1109/TMRB.2022.3145678 |doi-broken-date=18 October 2025 }}</ref>

}}

<ref name=”Azocar2020″>{{cite journal

== External links ==

| last1 = Azocar

| first1 = A. F.

| last2 = Rouse

| first2 = E. J.

| year = 2020

| title = Design and clinical implementation of an open-source bionic leg

| journal = Nature Biomedical Engineering

| volume = 4

| issue = 10

| pages = 941–953

| doi = 10.1038/s41551-020-00619-3

| url = https://www.nature.com/articles/s41551-020-00619-3

}}</ref>

<ref name=”UMnews2019″>{{cite news

[https://opensourceleg.org Official website]

| title = Open-source bionic leg aims to advance prosthetics research

| work = University of Michigan News

| date = 2019-06-04

| url = https://news.umich.edu/open-source-bionic-leg-first-of-its-kind-platform-aims-to-rapidly-advance-prosthetics/

}}</ref>

<ref name=”NSF1734586″>{{cite web

[https://github.com/neurobionics/opensourceleg OSL GitHub repository]

| title = NSF Award #1734586 – An Open-Source Robotic Leg Platform that Lowers the Barrier for Advanced Prosthetics Research

| website = NSF.gov

| url = https://www.nsf.gov/awardsearch/showAward?AWD_ID=1734586

}}</ref>

<ref name=”NRI2020″>{{cite web

[https://humotech.com/product/uncategorized/open-source-leg/ Humotech: Open-Source Leg]

| title = NRI: INT Collaborative Research – Open-Source Framework for Continuous Torque Control of Prosthetic Legs

| website = IRAD

| url = https://irad.nih.gov/project/nri-int-collaborative-research-open-source-framework-continuous-torque-control-intuitive-3

}}</ref>

<ref name=”POSE1″>{{cite web

| title = POSE Phase I – Advancement of an Open-Source Hardware and Software Ecosystem

| website = Elsevier Pure

| url = https://nsf.elsevierpure.com/en/projects/posphase-i-advancement-of-an-open-source-hardware-and-software-ec/

}}</ref>

<ref name=”POSE2″>{{cite web

| title = POSE Phase II – Continued Progression of an Open-Source Hardware & Software Ecosystem

| website = Elsevier Pure

| url = https://nsf.elsevierpure.com/en/projects/nsf-posphase-ii-continued-progression-of-an-open-source-hardware-/

}}</ref>

<ref name=”Humotech2021″>{{cite web

| title = U-M, Humotech partner to bring open-source bionic leg to research labs

| date = 2021-12-16

| website = Humotech

| url = https://humotech.com/press-release-u-m-humotech-partner-to-bring-open-source-bionic-leg-to-research-labs/

}}</ref>

<ref name=”Chosun2025″>{{cite news

| title = The Open-Source Leg Project

| work = Economy Chosun

| date = 2025-04-25

| url = https://economychosun.com/site/data/html_dir/2025/04/25/2025042500016.html

}}</ref>

<ref name=”SRALab2023″>{{cite web

| title = Open-Source Bionic Leg Project

| website = Shirley Ryan AbilityLab

| url = https://www.sralab.org/research/labs/bionic-medicine/projects/open-source-bionic-leg

}}</ref>

<ref name=”UMRobotics2024″>{{cite news

| title = Building an Ecosystem for the Open-Source Leg

| work = University of Michigan Robotics

| date = 2024

| url = https://robotics.umich.edu/news/2024/building-an-ecosystem-for-the-open-source-leg/

}}</ref>

<ref name=”Best2024″>{{cite journal

| last1 = Best

| first1 = T. K.

| year = 2024

| title = A Compact, Two-Part Torsion Spring Architecture

| journal = IEEE/ASME Transactions on Mechatronics

| doi = 10.1109/TMECH.2024.3508469

| url = http://dx.doi.org/10.1109/TMECH.2024.3508469

}}</ref>

<ref name=”Harris2024″>{{cite journal

| last1 = Harris

| first1 = I. R.

| year = 2024

| title = Evaluation of powered knee–ankle prosthesis control

| journal = IEEE Robotics and Automation Letters

| doi = 10.1109/LRA.2024.3416769

| url = http://dx.doi.org/10.1109/LRA.2024.3416769

}}</ref>

<ref name=”Bolivar2021″>{{cite journal

| last1 = Bolívar-Nieto

| first1 = E. A.

| year = 2021

| title = Powered prosthesis control modeling

| journal = Mechatronics

| doi = 10.1016/j.mechatronics.2021.102635

| url = http://dx.doi.org/10.1016/j.mechatronics.2021.102635

}}</ref>

<ref name=”Shetty2022″>{{cite journal

| last1 = Shetty

| first1 = V. S.

| year = 2022

| title = System identification for wearable robotic actuators

| journal = IEEE Robotics and Automation Letters

| doi = 10.1109/LRA.2022.3144790

| url = http://dx.doi.org/10.1109/LRA.2022.3144790

}}</ref>

<ref name=”RouseSoftware”>{{cite web

| title = Open-Source Leg Software Repository

| website = GitHub

| url = https://github.com/neurobionics/opensourceleg

}}</ref>

}}

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The Open-Source Leg (OSL) is an open-source robotic knee–ankle prosthesis designed for research in powered prosthetic control, gait biomechanics, and wearable robotics. The platform provides openly licensed mechanical designs, electronics schematics, firmware, and software libraries intended to support reproducible experiments and cross-laboratory comparison.^[1]

The first scientific description of the system appeared in 2020 in Nature Biomedical Engineering, which detailed the OSL’s mechanical design, sensing systems, control structure, and initial clinical evaluation.^[1] The project has received coverage from international media, including Economy Chosun, which highlighted the platform’s potential to standardize prosthetic research and expand access to experimental bionic technology.^[2] Development has been supported by multiple awards from the U.S. National Science Foundation.^[3][4][5][6]

History

The OSL originated under NSF National Robotics Initiative award #1734586 (2017–2020), which supported foundational development of the mechanical hardware, embedded control electronics, sensing integration, and open-source dissemination.^[3] A University of Michigan news release introduced the system publicly in 2019.^[7]

The platform’s first peer-reviewed scientific description was published in 2020 in Nature Biomedical Engineering, presenting detailed schematics, actuator characterization, sensing architecture, and clinical testing results.^[1]

Between 2020 and 2022, the NSF NRI:INT collaborative research award #2024237 supported development of continuous-torque control methods, benchmarking protocols, and multi-laboratory controller evaluation.^[4]

In 2024, the University of Michigan Robotics Department reported on ecosystem-building efforts for the OSL, including open-source governance, documentation development, community infrastructure, and partnerships with external laboratories.^[8]

The project continues under the NSF Pathways to Open-Source Ecosystems (POSE) program:

• POSE Phase I – #2229418 (2022–2023) – governance, documentation systems, and contributor pathways.^[5]
• POSE Phase II – #2315895 (2023–2026) – sustainability planning, onboarding tools, safety documentation, and long-term ecosystem maintenance.^[6]

The platform has been adopted by research groups in North America and Europe, including clinical partners such as the Shirley Ryan AbilityLab (SRALab).^[9]

Design

Hardware

The OSL consists of modular powered knee and ankle joints that share a similar mechanical structure, simplifying assembly and repair across research laboratories.^[1] Both joints use high-torque brushless DC motors originally developed for aerial robotics, chosen for torque density, low rotor inertia, and suitability for backdrivable actuation.

The joints employ low-ratio belt transmissions to increase backdrivability and reduce passive impedance. The ankle uses a two-stage reduction, while the knee uses a configurable single- or dual-stage design.^[1]

A selectable series elastic element can be included in the drivetrain, providing tunable joint stiffness for experimental investigation. Best et al. (2024) characterized torsion-based elastic actuation strategies compatible with the OSL’s modular architecture.^[10]

Integrated sensing includes:

• magnetic encoders for joint and motor position
• multi-axis load cells for torque or ground-reaction force estimation
• inertial measurement units (IMUs) for segment kinematics
• temperature, voltage, and current sensors for actuator protection

The electronics platform includes a six-channel data acquisition system, high-frequency analog sampling, and digital communication for real-time motor control. Shetty et al. (2022) used the sensing and electronics architecture to conduct actuator system identification and evaluation of torque dynamics.^[11]

The assembled system weighs under 6 kg and uses machined aluminum components with standardized mounting points. It supports tethered bench testing and untethered battery-powered locomotion.^[1]

Software

The OSL software includes embedded firmware, mid-level joint controllers, and high-level Python interfaces for experiment scripting.^[12]

Embedded firmware manages:

• motor voltage and current control
• encoder and load-cell sampling
• sensor fusion and filtering
• motor-driver communication
• safety monitoring and watchdog functions

Mid-level controllers implement:

• voltage control
• current (torque) control
• position control
• impedance control for biological stiffness and damping emulation

The continuous-torque controller framework developed under NSF award #2024237 supports smooth transitions between gait phases and works with finite-state machine controllers and adaptive impedance strategies.^[4]

The Python API offers:

• gait event detection
• parameter tuning
• real-time data logging
• visualization and debugging utilities
• ROS 2 integration

Research by Harris et al. (2024) and Bolívar-Nieto et al. (2021) evaluated prosthesis control methods—such as torque-based and impedance-based strategies—that are compatible with the OSL’s control and sensing architecture.^[13][14]

Software releases are distributed through GitHub and PyPI with automated testing for reproducibility.^[12]

Research use

The OSL is cited in research involving prosthesis control evaluation, gait biomechanics, and robotic actuation. Publications using methodologies compatible with the OSL architecture include:

• Best et al. (2024) – evaluation of torsion-based elastic actuation methods relevant to modular prosthesis actuation.^[10]
• Harris et al. (2024) – assessment of knee–ankle control strategies, including impedance-based approaches.^[13]
• Bolívar-Nieto et al. (2021) – modeling and control of impedance-based prosthesis controllers.^[14]
• Shetty et al. (2022) – actuator system identification using sensing and electronics architectures compatible with OSL hardware.^[11]

Community and adoption

The OSL ecosystem includes CAD models, electronics schematics, firmware, control libraries, documentation, and community-support resources. A public forum facilitates discussion and troubleshooting. Research groups internationally use the platform for gait biomechanics, prosthetic control, and wearable robotics research.

In 2021, Humotech partnered with the project to offer assembled OSL units for laboratories without in-house fabrication capabilities.^[15]

See also

References