Neural Based Powered Lower Limb Prosthesis

The microprocessor-controlled ankle has an actuator, multiple sensors and a hip that work together to perform to aid the user. It either adapts to the surface the foot is contacting or remains stationary. When it comes to choosing ankle-foot Prosthetics, patients have to choose from a wide variety o

Project Title

Neural Based Powered Lower Limb Prosthesis

Project Area of Specialization

Robotics

Project Summary

The microprocessor-controlled ankle has an actuator, multiple sensors and a hip that work together to perform to aid the user. It either adapts to the surface the foot is contacting or remains stationary. When it comes to choosing ankle-foot Prosthetics, patients have to choose from a wide variety of prosthetics and often the patient need to compromise on characteristics such as flexibility and stability.

The vast majority of available ankle-foot components are passive mechanisms with fixed ankles, such as energy-storing and -returning (ESAR) feet. Limitations of SACH, single-axis, and ESAR designs have been described with recommendations to develop feet that allow foot flat earlier in the gait cycle to reduce heel-only loading while simultaneously preserving limb stability and allowing tibial progression. ESAR feet can store energy more efficiently compared to SACH feet, but fixed-ankle ankle-foot components cannot adapt with changes in terrain. Hydraulic ankles do realign to changes in terrain through a viscoelastic response. However, the hydraulic resistance settings remain constant throughout the ankle range of motion and do not adapt with variations in terrain or walking speed.

Microprocessor-controlled prosthetic ankles (MPAs) provide distinct functional differences compared to passive ankle-foot mechanisms commonly used today. MPAs employ two distinct strategies to control ankle articulation. The first strategy adapts the ankle angle to match the slope of the terrain during swing phase but maintains a solid ankle during stance phase. With this approach, several steps are required to recognize the slope and adapt the ankle for subsequent steps (inter-step ankle adaptation). The second strategy approaches ankle articulation through a hydraulic cylinder during stance phase and adapts to a slope on each step-through (within-step ankle adaptation). Some MPAs provide within-step hydraulic ankle adaptation and inter-step terrain recognition with ankle adaptation for subsequent steps.

Project Objectives

Active Ankle Prosthetics find their application in easier walking, climbing stairs and slopes. Active ankle prosthetics moves the foot for the amputee. This ankle avoids letting itself be dragged on the surface like most Fixed Prosthetics. When this ankle contacts the ground, it can resist unnecessary movement and adapt and conform to the ground surface. An actuator simulates human leg muscles. With this ankle in place the amputee walks without instabilities.

Prosthetic ankles available now are static, but they don’t anticipate movement and adjust the feet to different terrains. Many users swing the prosthetic leg outward ever so slightly during regular walking to make up for feet that don’t naturally roll through the motion of walking.

This ankle operates an actuator with a microprocessor and aids to the amputee in walking, climbing stairs and irregular terrains.

The project requires work with the amputee, gathering feedback from the sensors and making adjustments based on both the data and the amputee’s user experience.

Prosthetic limbs have evolved considerably from the rudimentary wooden appendages of just a few decades ago. They can be bionic, brain-controlled and loaded with features -- and even mimic the sense of touch. But they're still a way off truly replicating the real thing, largely because of issues imitating the many subtle movements and sensations that come naturally to real limbs. Now, however, a new prosthetic ankle is overcoming these challenges.

Unlike existing prosthetic ankles, which work to passively absorb shock via springs and padding, the prototype can adapt to different ground surfaces and the way its user walks. It moves on its own in the style of a real ankle, controlling the tilt of the foot, lifting the big toe away from the ground and managing unstable or irregular surfaces.

It works with an actuator inside the joint, which is controlled by a chip that senses motion and regulates each step. The device first and foremost adapts to what's around it. The users can walk up and down slopes and stairs, and the device figures out what you're doing and functions the way it should. Most prosthetics offer a single axis motion without a powered actuator, this induces the user with pain at joints. In other words, by adding a microprocessor the ankle has an increased adaptability.

Project Implementation Method

It is important to consider the advantages and disadvantages of MPA components. A thorough assessment of specific limitations experienced by patients using solid ankle feet and their functional goals is necessary for making decisions regarding MPA technology. Combined with knowledge of the benefits supported by research, familiarity with the unique programming functions of the MPA technology will assist in deciding how patients would benefit most from this technology.

Taking into account research on general gait analysis, individual gait, user experience and data – the microprocessor-controlled ankle would mimic the human gait and then aid in his/her movement.

The ankle has already been manufactured and the actuator is in running condition. The first step is realize what kind of movement the user desires by realizing the kind of terrain. The next step is to actuate the motor accordingly to help the amputee. The main focus is to design a control strategy to operate the ankle. The final step is to test the ankle on an amputee for refining results.

Benefits of the Project

MPAs provide advantages that can be experienced during level ground walking, while the greatest benefits are experienced on uneven and sloped terrain. Over level ground, MPAs aim to mimic the three rockers of stance phase, which require rapid foot flat while simultaneously maintaining stability for weight acceptance. Following foot flat, MPAs provide a true articulation about the ankle and tibial progression through the second rocker of stance phase. The resistance can be controlled by the microprocessor to adapt ankle stiffness to changes in walking speed. Patients describe the benefits of ankle articulation during the second rocker of stance phase as having no “dead spot,” a phenomenon experienced with fixed-ankle feet that inhibit tibial progression. This reduces the risk of stumbles and falls. MPAs that only provide inter-step ankle adaptation and present a fixed-ankle during stance may not exhibit these advantages over level ground.

These advantages over level ground are experienced to a greater extent over uneven and sloped terrain. The lack of articulation of fixed-ankle feet induces greater ankle reaction torque and pressure on the residual limb. This causes patients to adopt accommodation strategies or limits their mobility on these terrains as the residual limb and proximal joints are unable to tolerate the increased loads. MPAs have been shown to reduce the peak pressures experienced on ramp ambulation by accommodating the slope of a ramp. Another advantage is the reduced stress on proximal joints during prolonged seating.

Technical Details of Final Deliverable

The final deliverable requires us to program the actuator such that it aids the amputee by first realizing the kind of terrain on which the user is walking using multiple sensors. This requires high processing power of a controller. At the end of the project amputee satisfaction and experience with the product counts reducing the pain in joints to the minimum and maximizing aid to walking on different terrains.

Final Deliverable of the Project

HW/SW integrated system

Type of Industry

Medical

Technologies

Artificial Intelligence(AI), Robotics, Wearables and Implantables

Sustainable Development Goals

Good Health and Well-Being for People

Required Resources

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