Joint trajectory generation and motion control of a wearable robot for complete paraplegics based on forward inflection walking

摘要

Wearable robots are regarded as a new transportation system in daily living for complete paraplegics due to spinal cord injury (SCI). For the motion control of a wearable robot, the normal gait pattern of people without disabilities is often applied as a reference input. When the natural dynamics of the human body can be utilized and the displacement of center of gravity (CoG) is possible, the normal gait pattern is effective to increase the gait speed with the minimal energy consumption. Complete paraplegics with high SCI level (i.e., above thoracic spine level), however, are able to voluntarily move neither the legs nor their waist, and thus they cannot control the CoG at all. Consequently, the normal gait pattern is not necessarily the best option for such complete paraplegics. In addition, the degree of freedom (DoF) of wearable robots is less than that of the human body; therefore, it is difficult to expect that the complete paraplegics naturally control the CoG even with the help of wearable robots. In this paper, a new gait pattern, called forward inflection walking (FIW), is proposed for the motion control of a wearable robot for complete paraplegics. The proposed FIW method enables to transfer the CoG to the leg ahead by modification and optimization of the joint angle trajectories for effective walking. Therefore, the FIW method intentionally moves the CoG of complete paraplegics with wearable robots according to the gait phase (i.e., stance and swing). The proposed method is verified by clinical experiments.