D2.1 Requirements and Specification - CORBYS

D2.1 Requirements and Specification
State­of­the­Art Relevant to the two Demonstrator Application Domains
16 State­of­the­Art in Gait Rehabilitation Systems (VUB)
Gait training, over ground or on a treadmill, has become an essential part of rehabilitation therapy in patients
suffering from gait impairment caused by disorders such as stroke, spinal cord injury, multiple sclerosis and
Parkinson's disease. Its effectiveness is increasingly evidenced by clinical trials and advancements in
neuroscience. Seemingly trivial, the notion of “(re)learning to walk by walking” hides some of the key
research questions that puzzle not only the field of rehabilitation science.
Similar to the neurological principles underlying human walking itself, the principles underlying motor
learning and neural recovery are not yet fully understood and are the subject of ongoing research. As a
consequence, research efforts in the field are focused on quantifying the rehabilitation process and identifying
rehabilitation practice that maximises outcome. In one of the existing practices, body-weight supported
treadmill training (BWSTT), the patient's body weight is partially supported by an overhead harness while
his/her lower limb movements are assisted by one up to three physiotherapists. The strenuous physical effort
encumbering the therapists and the resulting short training session duration was one of the main reasons for
introducing robotics into gait rehabilitation. Although this introduction was envisaged by therapists as well, it
was mainly driven by engineering, strengthened by technological advancements in robotics and prior research
into powered exoskeletons for humans. The advantages that were initially aimed at by automating therapy,
namely enhancing intensity, repeatability, accuracy and quantification of therapy, are indeed easily associated
with robotics. However, a robot operating in close physical contact with an impaired human requires an
approach to robot performance that differs significantly from the viewpoint of industrial robotics. Accurate
repeated motion imposed by a position controlled robot is considered contraproductive for many reasons: a
lack of adaptable and function specific assistance, a limitation of the learning environment, reduced
motivation and effort by the patient. Nowadays, the field of rehabilitation robotics is increasingly convinced
by a human-centred approach in which robot performance is focused on how the robot physically interacts
with the patient.
A focus on the human in the robot puts emphasis on the adaptability and task specificity of robotic assistance
required to achieve “assistance-as-needed”. At the same time, safety of inter-action, preventing harm and
discomfort, is mandatory. Variable stiffness or variable impedance is a promising concept in robot design and
control that addresses both safety and adaptability of physical human-robot interaction (pHRI). It implies that
the robot gives way to human interaction torques to a desired and adjustable extent. This adds to the high
requirements that were already imposed by the application, for instance with regard to wearability (compact
and light weight design, adjustable to the individual) and actuator performance (high torque output, high
power-to-weight ratio). Hence, in the development of novel prototypes rehabilitation roboticists are faced
with the challenge of combining suitable design concepts, high performance actuator technologies and
dedicated control strategies in view of improved physical human-robot interaction. Improvement, that should
lead to a better insight into the effects and effectiveness of robot-assisted rehabilitation and ultimately, leads to
better therapies.
16.1 Gait rehabilitation
In persons with damage to the central nervous system, for instance due to stroke (brain damage) or incomplete
SCI (spinal cord damage), task-specific and intensive gait training leads to (partial) recovery of motor
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