The present invention is directed to an autonomous exoskeleton device that includes one or more actuators, one or more controllers, one or more sensors with one or more unidirectional transmissions. The present invention provides a mechanical joint in parallel with a biological joint. The exoskeleton device preferably includes and electric motor and winch, chain, belt, cam transmission or other mechanism for providing unidirectional force to assist rotation about the biologic joint. Moreover, a controller, a motor angle sensor, joint angle sensor and/or force sensor may be used for additional control and monitoring of the device. The motor may be any type of motor, but is preferably brushless in configuration where its diameter is larger than its length to provide a compact and lightweight exoskeleton device.