Ultrasound Imaging Based Sensing of Human Ankle Motion Intent and Control Strategies for Ankle Assistance

Inclusion Criteria for participants without neurological disorders:

* Age between the ages of 18 and 64,
* Weight less than 220 lb,
* Able to perform ankle movements such as ankle up motion, ankle down motion, side motion towards inside, and side motion towards outside while seated, and
* Able to walk normally at a preferred speed without any assistive device.

Exclusion Criteria for participants without neurological disorders:

* Any difficulty or an orthopedic condition that would impede ankle movements such as ankle up motion, ankle down motion, side motion towards inside, and side motion towards outside,
* Any difficulty walking normally or without assistance,
* Absence of sensation in lower extremities,
* An allergy to adhesive skin tapes and/or US gels,
* Pregnant Females,
* No ankle muscle response to FES.

Inclusion Criteria for participants with neurological disorders:

* 18-64 years of age and have a primary diagnosis of traumatic/non-traumatic iSCI or demyelinating diseases like transverse myelitis,
* Weight less than 220 lb,
* Sub-acute or chronic phase (at least 3 months after injury) incomplete motor lesion (AIS C or D at enrollment) at cervical, thoracic or lumbar level,
* Ability to ambulate over ground independent using either a cane or rolling walker, as well as those that do not require any assistive devices but do have some mobility difficulties,
* Medically stable with medical clearance for participation, no evidence of cardiopulmonary or pulmonary disease, severe spasticity, and asymmetric hip positions,
* Ability to respond to FES on dorsiflexors and plantarflexors, and
* No use of any FES devices or already in use of a FES device for mobility support (like a Bioness device) but will not use the device during the study.

Exclusion Criteria for participants with neurological disorders:

* Subjects with other neuromuscular diseases such as polio, stroke, or multiple sclerosis,
* Presence of transmissible diseases such as (but not limited to) hepatitis or immunodeficiency virus,
* Any clinical condition contraindicating gait,
* Untreatable chronic pain,
* Severe spasticity (Ashworth scale score \> 3),
* Severe reduction in lower limb joint Range of Motion (ROM) higher than 20 deg,
* At a high risk of a fracture from osteoporosis,
* Any skin problem inhibiting robot usage, major depression or psychosis,
* Subjects with heart conditions and pacemakers,
* Concurrent severe medical disease, pressure sores, open wounds, existing infection, unstable spine, unhealed limber pelvic fractures, history of recurrent fractures, known orthopedic injury to lower extremities, and osteoporosis,
* Have open wounds,
* Pregnant Females,
* No ankle muscle response to FES.