Designed to be easy to manufacture, assemble, and repair
The Open-Source Leg hardware is a robust and relatively inexpensive system that can be easily manufactured, assembled, and controlled. Through this website, researchers have access to downloadable hardware files so that they can enter the research field without having to design a prosthetic leg themselves. Ultimately, having a ubiquitous leg will help facilitate comparison between control strategies, potentially streamlining the field towards highly functional robotic prosthetic legs.
The OSL is assembled from both machined and stock components. In selecting components, we minimized price, lead times for machined parts, and the number of vendors. To ensure broad accessibility for researchers across diverse backgrounds, we adhered to key design principles.
The OSL is designed to be assembled, controlled, and maintained with moderate 'hands-on' skills. We streamlined the number of components and suppliers, with the majority of parts machined from a single supplier, minimizing dependencies on precision machine components.
We prioritized portability by ensuring the OSL weighs less than its biological counterpart. Each joint is equipped with on-board batteries, sensing, and control, facilitating research activities outside of traditional laboratory settings.
The OSL is a cost-effective solution, ranging from approximately $10,500 to $23,000, depending on degrees of freedom and sensing options. This stands in stark contrast to commercial powered prostheses, which can cost up to $100,000.
| Component | Price (USD) |
|---|---|
| Machined Parts | $5,453.00 |
| Actuators and Batteries | $12,630.00 |
| Belts | $162.00 |
| Bearings and Fasteners | $1,323.00 |
| Sensors & Electronics | $3,532.00 |
| Total | $23,100.00 |
Thanks to Rachel Gehlhar Humann for providing the latest prices for machined parts, actuators, bearings, and fasteners.
The OSL is designed to be highly customizable. Researchers have the flexibility to tailor the device to their specific needs, including adjusting the knee's series elastic element, selecting the foot type, and incorporating a load cell, among other options. Both the knee and ankle function either as a series elastic actuator (SEA) or rigid actuator, and the stiffness can be selected using custom designed spring disks that fit inside the output pulley without changing the OSL's volume.
The OSL v2 represents a significant evolution informed by community feedback, focusing on simplicity, portability, and enhanced technical capabilities.
The Open-Source Leg is a modular and extensible platform designed to support a wide range of research applications. Researchers can swap out any of the components described below to create a custom system for their specific research needs and share their designs with the community.
Build your own Open-Source Leg with complete design files, detailed documentation, and video tutorials. This approach offers maximum flexibility and learning opportunities.
For research groups who prefer to purchase rather than build, you can get either a preassembled Open-Source Leg or a kit of parts from Humotech, a commercial supplier of wearable robotics devices. Humotech has supplied 7+ OSLs across USA, Canada, and Europe. We do not profit from any of the commercial services that Humotech offers, our collaboration with Humotech is designed only to occasionally help them support their customers with any technical questions and make the Open-Source Leg platform readily accessible for the research community.
Complete technical specifications for the Open-Source Leg hardware platform
| Property | Value |
|---|---|
| Mass (Knee + Ankle, w/ batteries and electronics) | 5.4kg |
| Minimum Build Height | 451mm |
| Knee Range of Motion | 0° to 120° |
| Ankle Range of Motion | -30° to 30° |
| Transmission Ratio (At the Joint) | 41.5:1 |
| Planetary Gear Reduction (Motor) | 9:1 |
| Belt Drive Reduction (External) | 5.44:1 |
| Series Elasticity | 0-600 Nm/rad (Customizable) |
| Peak Torque (Continuous) | ~29Nm |
| Peak Torque (Instantaneous) | ~145.25Nm |
| Peak Speed | 6.13rad/s |
| Torque Constant | 0.14Nm/A |
| Bus Voltage | 33.3V |
• Minimum build height is measured from the ground to the top of the knee pyramid with a variflex foot.
• Peak instantaneous and continuous torque values are calculated based on Dephy's actuator specifications at 25A and 5A respectively.
• Series elasticity can be customized using spring disks with different stiffness values.
