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

Robotic therapies aim to improve limb function in individuals with neurological injury. Modulation of robotic assistance in many of these therapies is achieved by measuring the extant volitional strength of limb muscles. However, current sensing techniques, such as electromyography, are often unable to correctly measure the voluntary strength of a targeted muscle. The difficulty is due to their inability to remove ambiguity caused by interference from activities of neighboring muscles. These discrepancies in the measurement can cause the robot to provide inadequate assistance or over-assistance. Improper robotic assistance slows function recovery, and can potentially lead to falls during robot-assisted walking. An ultrasound imaging approach is an alternative voluntary strength detection methodology, which can allow direct visualization and measurement of muscle contraction activities. The aim is to formulate an electromyography-ultrasound imaging-based technique to sense residual voluntary strength in ankle muscles for individuals with neuromuscular disorders. The estimated voluntary strength will be involved in the advanced controller's design of robotic rehabilitative devices, including powered ankle exoskeleton and functional electrical stimulation system. It is hypothesized that the ankle joint voluntary strength will be estimated more accurately by using the proposed electromyography-ultrasound imaging-based technique. And this will help the robotic rehabilitative devices achieve a more adaptive and efficient assistance control, and maximize the ankle joint rehabilitation training benefits.