Design and evaluation of a reaction-force series elastic actuator configurable as biomimetic powered ankle and knee prostheses

All commercial leg powered prostheses have been, up to this point, a one-size fits-all design, and of those existing systems, none has yet managed to fully achieve biological walking range of motion, torque and power. Yet, no human body is the same as the next. A configurable prosthesis potentially offers improvements in battery run-time, prosthesis mass, acoustic noise, user comfort, and even enables sport and economy modes within the same fundamental hardware. In this thesis, a reaction-force, series-elastic actuator (RFSEA) is presented that is capable of achieving biomimetic ankle and knee kinetics and kinematics during level-ground walking across a range of body masses, heights and walking styles. The platform is configurable to inertial load by swapping a simple-to-manufacture flat-plate composite spring that allows tuning the actuator dynamics to match different user requirements. The RFSEA also comprises a high torque and pole-count drone motor that directly drives a ball screw with a tunable, low-gear ratio lead. The design enables high dynamic range providing a closed-loop, torque-controlled joint that can demonstrate arbitrary levels of impedance. This control fidelity is important to support smooth control in free-space and high-inertial output conditions, such as the swing and late-stance phases of walking, respectively. A simulation framework is presented that defines mechatronic design specifications for the motor, spring, and gear-reduction components. The optimization procedure clamps output joint dynamics to subject-specific biological gait data, and searches for minimum electric energy solutions across the motor, gear-reduction and spring component space. A second optimization procedure then searches for optimal linkage and spring geometry to best approach the design targets as constrained by the availability of discrete drivetrain components. In this thesis, ankle and knee designs are presented with optimized components using biological joint data from a non-amputee subject walking at 2.0m/sec with a body mass equal to 90Kg. For these designed biomimetic joints, system specifications are verified using bench test evaluations, and preliminary human gait studies.

Name thesis:degree_name

Doctoral

Department dc:contributor.department

Program in Media Arts and Sciences (Massachusetts Institute of Technology)

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2020

Author dc:creator

• Carney, Matthew Eli.

Advisor dc:contributor.advisor

• Hugh M. Herr.

• Program in Media Arts and Sciences

Statement dc:rights

• MIT theses may be protected by copyright. Please reuse MIT thesis content according to the MIT Libraries Permissions Policy, which is available through the URL provided.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1721.1/145212

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/145212