Spinal Cord Injury Rehab with HAL

As the leading exoskeleton on the market, HAL can be used for Spinal Cord Injury rehab in a variety of different modes. For this case study, we’re going to be examining the progression from CVC to CAC mode in a client with a Spinal Cord Injury.

Background

Our client in this case study has a C4/C5 incomplete spinal cord injury. His overall level of injury is classified as ASIA B on the American Spinal Cord Injury Association Scale in terms of its severity.

In layman’s terms, this basically means that our client has some sensory function but a loss of motor function below the level of injury.

How HAL Works

As you might recall from our guide to HAL, there are three primary modes of operation for the HAL Exoskeleton. Cybernic Voluntary Control, Cybernic Autonomous Control and Cybernic Impedence Control. For this case study, we’re looking at the difference between Cybernic Voluntary Control and Cybernic Autonomous Control

Cybernic Autonomous Control (CAC)

CAC uses pre-programmed gait programs to detect shifts in the centre of gravity to provide a more minimal level of assistance. As with CVC, there are two sub modes:

Stand: Autonomously assists a standing up motion from a sitting posture and maintenance of a standing posture.

Walk: Estimates whether each leg is in the swing phase or the support phase based on plantar force detected from each sensor shoe. Provides autonomous assistance to each motion.

Cybernic Voluntary Control (CVC)

CVC is the next step from CAC, with clients typically transitioning after several weeks or months of training with CAC mode. 

CVC is all about detecting the wearer’s movement intent via electrodes, and then dynamically adjusting the level of assistance depending on the intended movement and wearer’s strength. CVC is further divided into two sub modes:

Stand: Biases the assistance torques so as to better support standing up from a seated posture, or to better support the maintaining of a standing posture. Gives upward assistance torque to support a gentle sit-down motion.

Walk: Gives assistance based on BES. Estimates whether each leg is in the swing phase or the support phase, based on the plantar force detected from each sensor shoe. Adjusts assistance torque to avoid knee buckling of the supporting leg and assists an easier forward swing of the swinging leg.

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