Lower extremity exoskeleton for gait retraining
The Active Knee Rehabilitation Orthotic System (ANdROS) is a wearable and portable assistive tool for gait rehabilitation and monitoring of people with motor control deficits due to a neurological ailment, such as stroke. ANdROS reinforces a desired gait pattern by continually applying a corrective torque around the knee joint, commanded by a impedance controller. A sensorized yet unactuated brace worn on the unimpaired leg is used to synchronize the playback of the desired trajectory based on the user's intent. The device is mechanically grounded through two ankle foot orthoses (AFOs) rigidly attached to the main structure, which helps reduce the weight perceived by the user.
1. A lower extremity exoskeleton for gait rehabilitation comprising:
a pelvic brace;
an unactuated leg brace rotatably connected to the pelvic brace, further comprising:
first upper and first lower leg shanks joined by a first rotatable knee joint to provide flexion and extension of the unactuated leg brace, wherein the first upper and first lower leg shanks are adapted to be coupled to legs of a user; and
a sensor for measuring knee flexion and extension angles of the first rotatable knee joint;
an actuated leg brace rotatably connected to the pelvic brace, further comprising:
second upper and second lower leg shanks joined by a second rotatable knee joint to provide flexion and extension of the actuated leg brace, wherein the second upper and second lower leg shanks are adapted to be coupled to legs of a user; and
means for creating a torque around the axis of rotation of the second rotatable knee joint; and
an impedance controller for computing a desired knee angle at the first rotatable knee joint based in part on the sensor measurements and commanding a torque at the second rotatable knee joint based in part on the desired knee angle.
2. The system of claim 1 wherein the first and second upper and lower leg shanks are slotted for adjusting the distance from hip to the knee joint and from the knee joint to the ankle joint, respectively.
3. The system of claim 1 wherein the leg braces are each connected to the pelvic brace using a spherical joint that allows for flexion/extension, abduction/adduction, and rotation.
4. The system of claim 1 wherein the unactuated leg brace further comprises a sensor for measuring hip flexion and extension angles.
5. The system of claim 1 wherein the unactuated leg brace further comprises a sensor for measuring the vertical hip position.
6. The system of claim 1 wherein the unactuated leg brace further comprises a sensor for measuring ankle flexion and extension angles.
7. The system of claim 1 wherein the sensor includes a rotary potentiometer and a rotary encoder.
8. The system of claim 1 wherein each leg brace further comprises a telescopic structure that allows the exoskeleton structure to shorten during abduction.
9. The system of claim 1 further comprising a first ankle foot orthosis coupled to the unactuated leg brace and a second ankle foot orthosis coupled to the actuated leg brace.
10. The system of claim 9 wherein the first ankle foot orthosis includes a pressure transducer.
11. The system of claim 1 wherein the actuated leg brace is connected to the pelvic brace via a first hip joint that allows for flexion and extension and a second hip joint that allows for abduction and adduction; and
wherein the unactuated leg brace is connected to the pelvic brace via a third hip joint that allows for flexion and extension and a fourth hip joint that allows for abduction and adduction.
12. The system of claim 1 further comprising a pelvic rehabilitation system for addressing secondary gait deviations.
13. The system of claim 1 wherein the impedance controller measures at least one gait related physiological parameter of the user; and estimates the cadence of the user based on at least the one gait related physiological parameter.
14. The system of claim 1 wherein the impedance controller estimates the cadence of the user; and selects a reference gait trajectory based on the estimated cadence of the user.
15. The system of claim 1 wherein the impedance controller computes a desired joint angle based on an estimated gait phase of the user and an estimated cadence of the user.