ALEX is a series of exoskeletons designed for gait training. One of the fundamental features of ALEX is the ability to control forces at the foot in response to errors in the trajectory of the foot. A variety of studies have been performed with ALEX to show the feasibility of gait training of human subjects using a combination of force feedback, visual feedback, and audio feedback. ALEX II is a one-leg exoskeleton for gait training of stroke patients. ALEX III is a bilateral exoskeleton. A series of human studies have been performed with these exoskeletons to demonstrate the effectiveness of gait retraining.

Active Leg EXoskeleton

Alex 2

ALEX II is a unilateral, leg exoskeleton capable of controlling hip and knee flexion/extension of the left or right leg and passively allows movement for hip abduction/adduction, ankle plantar/dorsiflexion, and at the pelvis, rotation about the vertical axis and translation in all three directions.  The support structure allowing pelvic movement is passively compensates for the weight of the robot so the wearer doesn’t have to support the weight of the device.

The ALEX II control architecture is similar to those of the whole family of ALEX devices: forces are applied to the foot in response to errors in template of the motion of the ankle center point and foot orientation. All details of trajectory thresholds, foot force field strategy, and magnitude of assistive or resistive forces can be programmed and customized. Augmented multimodal feedback provides the user with information about the desired target and the current performance with respect to the target, with the aim to promote each subject's active effort and participation.

Alex 3

ALEX III is a bilateral leg exoskeleton with 12 active degrees-of-freedom. This creates a highly functional device for testing various aspects of gait training to determine how to best provide care. Using this tool we can test aspects of control and mechanical design, which can be applied to future exoskeleton design to produce more effective and cost efficient devices. Additionally, we can use it to probe the motor control system to increase or understanding of how people learn and recover from neural injury.