Wearable Lower Limb Exoskeleton Robot For Rehabilitation And Its Gait Control Strategy

Wearable lower extremity rehabilitation exoskeleton robot is a bionics inspired of humachined intelligent system, aiming to help the lower limb disabled people to stand and walk again, as well as rehabilitation training. Unlike traditional rehabilitation equipment limit to be used in fixed indoor environment, it moves training outdoor, even without the presence of medical staff, and comes to be used at home. The purpose of this paper is to develop a exoskeleton system which is suitable for the paraplegia patient. The main contents include the design of the external skeleton, the control system and the gait control algorithm.Inspired by the biomimetics, this paper designed a exoskeleton with 8 DOFs (degrees of freedom), including four active and two passive and two limited ones. The main structure comprises a joint driving mechanism, backpack, ankle, crutches and man-machine force interaction structure. The drivable joint requires a high power to volume ratio, which is a difficult point in structural design. By referring to the relevant literature, the types of existing joint mechanisms are summarized, and the feasibility of the scheme of the four link mechanism of variation plane is discussed in detail. A visible parameters adjusting method is proposed based on local kinematics, by which we can make joint structure accords with the human lower limb joint motions and the rules conveniently. Through the finite element simulation analysis, the weak link in the joint is determined, and then be reinforced.The.robot uses the battery to facilitate long-distance walking, using industrial control host as the control center, integrating angle sensor, attitude sensor, pressure sensor, etc., to achieve closed-loop control of the robot. According to the habit of human subconscious, a simple but effective walking control logic was exhibit, which can reduce the possibility of improper operation by mistake. The host computer software is mainly designed for debug at present. In addition, relays are artfully used to obtain the temporary protection mechanism.Among 7 kinds of lower limb auxiliary control strategy, we discussed which of them can be applied on the paraplegic trial; and further analyze the feasibility of paraplegia patients to stand and walk again. A gait modification method is proposed, which can not only solve problem of interfere between toe and floor, but also generate gaits suitable for slope walking.2 paraplegia volunteers are participated in the walking test, which verified the reliability of the robot system, and the effectiveness of the gait correction method.Finally, according to the special needs of sit-to-stand and stand-to-sit, we make a three quality bar model and build its stable space, based on which the speed compliant control method is proposed. The compliance mechanism can alleviate the impact on balance caused by inappropriate crutch force. Experimental results show that, compared with the traditional trajectory control method, the compliant control method improves the success rate significantly.