This paper describes a powered orthosis for lower limbs which restores the gait of locomotion disabled persons such as paraplegics, and its clinical experiments. It supports the patient's weight, has four electrohydraulic digital actuators to motorize hip and knee joints, as well as sensors to detect joint angles, plantar contacts. Each joint angle is controlled by microcomputer in such a way that an appropriated gait pattern is restored for a stable powered level walk. This second prototype of the powered orthosis has been designed and developed to test on patients to see the effectiveness of the powered orthosis. For the control of this orthosis, the gait pattern is generated by a 16-bit master microcomputer using the preprogrammed pattern which is synthesized with 20 parameters; Gsix 8-bit slave microcomputers measure and control joint angles. Further a desktop microcomputer is used for the change of parameters as well as for the dialog with the master computer. The orthosis weighs only 19.5kg, and hydraulic power unit 68kg. Clinical experiments of this prototype have been carried out on two paraplegics. A powered walk of 6.0 sec/step was realized for the first time and then 4.5 sec/step for about 10 meters.
