A more natural gait: load cells in intelligent artificial limbs

Published On: September 30 2022

Artificial limb development has made a radical shift in the abilities (and public perception) of amputees, from being disabled to beating able-bodied runners on the running tracks!

We’ve covered the use of load cells in testing artificial limbs before, but a new intelligent limb takes this into new territory for above-knee amputees.

Intelligent artificial limbs

Clever as they are in mechanical terms, few artificial limbs are actually ‘smart’ or ‘intelligent’ in terms of being personalised to the user. Those that are can be very expensive.

A team from the IRSO (Indian Space Research Organisation) have developed a commercially viable intelligent artificial limb for above the knee amputees. Unlike “passive” limbs that do not use microprocessors, the IRSO team’s intelligent limb can analyse and replicate the action of the amputee’s natural gait, making it more comfortable and instinctive to use.

New knees

At the top of the limb is a microprocessor-controlled knee (MPK) equipped with sensors that, according to Tech Explorist:

“Can establish walking characteristics customized to amputees to increase comfort using computer-based software. In real-time, as you’re walking, the interface plots the parameters.”

The MPK consists of a microprocessor, hydraulic damper, load & knee angle sensors, composite knee-case, Li-ion battery, electrical harness, and interface elements. As an article at the IRSO states:

“The microprocessor detects the state of gait based on the sensor data. The control software estimates the real-time damping needed to attain the desired gait by changing the stiffness of the system that is achieved by a hydraulic damper operated by a DC motor. Walking parameters specific to amputees can be set using PC-based software to improve one’s comfort. The interface plots the parameters in real time during walking.”

To test the limb, the team put together various models of the system, including a custom-designed exo-socket allowing the models to be tested on non-amputees. The initial system used a solenoid valve-based damper, and a six-axis load cell. The final model added a:

“DC motor-based damper with a spool position sensor, pylon integrated load cell, miniaturised control electronics, and a Graphical user interface for parameter tuning.”

Bionic and big data

For more on artificial limb technology see our blog “Beyond blades: the future of robot prosthetics

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