What Is Assistive Technology for Rehabilitation?
Loss of physical mobility limits one's ability to participate as much as possible in preferred activities and, in the worst-case scenario, completely prohibits involvement. This study examines the latest developments in assistive technology to enhance the mobility of individuals with disabilities. It draws from observations made while visiting European academic and industrial research facilities. A more seamless combination of the user's capabilities with assistive technology is the central idea of this new effort. This enhanced integration covers a wide range of technologies, such as wearable exoskeletons, prosthetic limbs, motorized wheelchairs, and functional electrical stimulation. Three strategies are being used to achieve better integration:
1) Enhancing the mechanics of assistive technology.
2) Enhancing the physical interface between the user and the technology;
3) Facilitating control sharing between the user and the technology.
What Are The Improved User-Technology Integration In Assistive Technology For Mobility?
As said in the abstract, a more seamless integration of the user's capabilities with assistive technologies is the unifying theme or trend of the studies we witnessed. The methods used to increase integration that have been noticed can be roughly categorized into three non-exclusive areas:
1) Enhancements to the mechanics of assistive technology;
2) Enhancements to the physical interface between the user and the technology; and
3) Enhanced shared control between the user and the technology. Advancements in software and hardware are examples of improvements in technology mechanics.
Enhancements to the hardware interface usually concentrate on better using the user's abilities to manipulate the technology and offering easier-to-use device control.
In four major technology areas—powered wheelchairs, prosthetic limbs, functional electrical stimulation, and robotic exoskeletons—the panel saw a shift towards improved user-technology integration.
Powered Wheelchair Mobility:
Traditionally, a joystick and one or more switches that alter the function the joystick controls are used to drive power wheelchairs. Wheelchair mobility, seat tilt, backrest recline, footrest elevation, and seat elevation are some features. Not everyone who could benefit from a motorized wheelchair has the cognitive and neuromuscular ability to use a joystick to navigate a dynamic environment. A "shared" control strategy combined with a different interface is recommended for these users.
Wheelchair mobility that is motorized has already been studied with shared control. A typical shared control system uses assistive technology to help users navigate their journey. Typically, shared control systems provide multiple modes that adjust movement algorithms and the level of support (i.e., user autonomy). According to Millan et al., shared control techniques fall into one of two categories: Mode changes can be either:
1) Manually prompted by the user using a button or trigger or
2) Hard-coded to happen only under certain circumstances.
There could be issues with either strategy. In addition to adding complexity and potential fatigue, requiring the user to initiate mode changes makes the system less user-friendly. Hard coding mode adjustments might not enable customization to the person and their unique set of skills.
Control of Prosthetic Limbs:
Replacing both the efferent neural system (which controls movement) and the afferent nervous system (which controls sensory feedback) is a problem in prosthetic development. Proper replacement of both the efferent and afferent systems will result in adequate control of prosthetic limbs. In Europe, three cutting-edge methods for improving user-prosthetic interface have been noted:
1) Peripheral Nervous System: Interfaces an example of an improved interface;
2) Computer-vision enhanced control: An example of an improved device and shared control system; and
3) Kinematic/kinetic-based control: A method that uses software to improve the limb's mechanics and create a better interface. The third strategy focuses on the lower limb, while the first two target prosthetic control in the upper limb.
Improved Control With Computer Vision:
A person's hand takes a specific position and opens to accept an object when they reach to grasp it. Because the user must plan the grasp and create step-by-step signals to position and shape the hand, prosthetic hand control typically entails a high mental cost. While this technology allows for a high degree of flexibility, consumers prefer straightforward controls that require less cognitive effort. Researchers at the University of Aalborg have created a camera-based shared control system that employs image recognition to independently choose the appropriate grip size, shape, and orientation based on manipulated pictures of the object to provide a less taxing control technique. The camera-based control chooses and applies the grasp type and size; the user must aim, trigger, and orient the hand. The user burden is reduced by giving the prosthesis more autonomy. Thirteen non-disabled participants tested the technology successfully, using it to operate an artificial hand.
Control of the Peripheral Nerve System Interface (PNS):
The multitude of motions that can be controlled and the restricted number of locations for conventional control interfaces make upper extremity prosthetic control difficult. Using the same nerve that initially delivered afferent and sensory information to operate a prosthetic arm or hand is an interesting alternative. Using the same nerve that formerly transmitted afferent and efferent signals between the arm and brain to operate a prosthetic hand or arm is an attractive alternative. This strategy might provide a channel for delivering sensory feedback and be more user-friendly.
Dr. Silvestro Micera has investigated this possibility at Scuola Superiore Sant'Anna in Italy by implanting thin-film longitudinal intrafasicular electrodes in a trans-radial amputee's median and ulnar nerves. A prosthetic hand was placed directly on the distal end of the remaining radius in the individual. The patient was instructed to visualize three different hand/finger movements throughout a four-week experiment, and the resulting muscle activity was measured.
Kinematic and Kinetic Management:
Dr. Heinke Vallery of ETH Zurich's Sensory Motor Systems lab has created a cutting-edge method for managing a transfemoral prosthetic leg fitted with a "powered" knee. Joint motions are tightly connected when walking. Using the physiological inter-joint couplings of the intact leg, Dr. Vallery's method, known as Complementary Limb Motion Estimation (CLME), instantaneously estimates the motion required of the prosthetic leg. The estimated motion controls the prosthetic limb's motion, which serves as a reference. A benefit of CLME is that it provides an extensive range of motion and synchronizes the prosthetic limb with the non-impaired limb by nature. It has been tested on an amputee while walking on a treadmill and climbing and descending stairs.
Robot Exoskeleton:
The military started researching and developing robotic exoskeletons in the 1960s. Nonetheless, research on robotic exoskeletons has recently shifted its attention to the movement of individuals with disabilities. Early research on robotic exoskeletons has primarily focused on therapeutic uses; one example is the Lokomat gait training robot, described in a companion study. The use of robotic exoskeletons for assistive technology, where the exoskeleton is made to support functional activities in the home and community, is currently receiving more attention. According to a recent analysis, robotic exoskeletons need to have four qualities to reach their full potential as assistive and rehabilitative technology:
1) Solid cognitive contact between humans and robots in multiple dimensions.
2) Secure and trustworthy physical interaction.
3) Actual wearability and portability.
Conclusion
During its tour, the panel did not see the development of any radically new assistive technologies; instead, the primary trend in assistive technology development that was noted was the creative improvement of already existing assistive technology to improve its ability to interact with the user's capabilities. Improved technology mechanics (e.g., knee-ankle-foot orthoses, kinetic control of prosthetic limbs); improved user interfaces (e.g., tongue or whole-body controllers, electrodes implanted in the central and peripheral nervous systems); and automated target control functions that combine the machine's assistance with the user's natural abilities are some of the ways that these refinements are being made, application by application.
