Natural control for prosthetics and robotic limbs

A recent study conducted by researchers at the Istituto Italiano di Tecnologia (IIT) in Italy and Imperial College London in the UK has demonstrated a link between hand movement patterns and motoneuron control. These findings pave the way for developing prosthetic limbs that feel more natural to users, significantly improving their usability and functionality.  

Traditional prosthetic limbs often fail to meet the expectations of users, leading to high abandonment rates. Many prostheses do not respond intuitively to movement and control needs, making them difficult to integrate into daily life. The European Research Council (ERC)-funded project "Natural BionicS" aims to overcome these challenges by developing prosthetic solutions that interact with the environment in a way similar to a real human limb. 

Antonio Bicchi from IIT and Dario Farina from Imperial College London lead the research teams. Their work is based on the theory of sensorimotor synergies, which describes how coordinated muscle activation and joint movements drive human motion. Understanding these synergies enables the design of prosthetic devices that can seamlessly integrate with the nervous system. 

The research highlights for the first time that two key neural structures – synergies at the spinal motoneuron level and those governing hand movements – are interconnected. Using advanced algorithms, researchers decoded the electrical signals produced by muscles, uncovering how specific neural structures control hand postures. 

By mapping these signals, researchers could determine distinct neural groupings responsible for dexterous movements. This knowledge allows for more intuitive human-machine interactions, extending beyond prosthetics to fields such as assistive robotics and human augmentation. 

As part of the study, the research team designed a soft prosthetic hand capable of executing movements based on two primary postural synergies. The device features two degrees of actuation, allowing for more natural hand postures. 

The prosthetic hand was tested in real-time scenarios with 11 participants without physical impairments and three prosthesis users. Researchers employed an advanced online method that mapped neural synergies to continuous operation of the prosthetic hand, demonstrating that integrating neural and postural synergies results in precise, coordinated, and natural multidigit control. 

These findings have significant implications for prosthetic limb users, offering: 

• A more natural and intuitive user experience 

• Improved ability to perform dexterous tasks, such as in-hand manipulation 

• Greater autonomy in daily activities 

By leveraging neural decoding and multi-synergistic prosthetic designs, researchers are making strides toward prostheses that closely replicate the fluidity and functionality of natural limbs. Their work not only benefits individuals with limb differences but also contributes to the broader field of human-machine interaction. 

REHACARE.com; Source: Istituto Italiano di Tecnologia – IIT