Patent ID: 8147436

Claim:
A powered orthosis adapted to be secured to a corresponding body portion of a user for guiding motion of the user, the orthosis comprising: a plurality of structural members; and one or more joints adjoining adjacent structural members, each joint having one or more degrees of freedom and a range of joint angles, one or more of the joints comprising: at least one back-drivable actuator governed by at least one joint actuator controller for controlling the joint angle, the one or more joint actuator controllers comprising force-field controllers that define a virtual tunnel for movement of the orthosis, the force-field controllers synchronized to cause the corresponding joint actuators to generate forces for assisting the user to move the orthosis at least in part under the user's power along a desired trajectory within an allowed tolerance, the generated forces comprising tangential forces along the desired trajectory and normal forces perpendicular to the trajectory, the tangential forces being inversely proportional and the normal forces being directly proportional to deviation from the desired trajectory.