Cooperative control of exoskeletal assistive system for paraplegic walk-transferring between sitting posture and standing posture, and going up and down on stairs

This paper presents a cooperative control algorithm for a paraplegic patient to walk stably as requested. The algorithm generates stable motions of a lower limb for a paraplegic walk, receiving patient´s preference related to his/her movement such as stand-to-sit and sit-to-stand transfers, walking and going up and down stairs. An exoskeletal walking support system assists motions of patient´s lower limb in accordance with a patient wishes when a patient indicates his/her wishes by using residual functions such as motions of an upper limb. In our project, a pair of gloves with several DOFs was developed to convey wearer´s wishes to the walking support system. The gloves measure his/her index fingers´ swing that simulates foot motions of his/her walking and measure flexion or deviation of his/her wrist joint. The cooperative control algorithm based on a cart-table model designs trajectories of each joint for stable motions that satisfy the wishes expressed by the wearer´s hand and wrist motions and then the designed motions are executed in realtime by the walking support system. As the first trial, a small humanoid robot is used for safety as a control target that corresponds to a combination of the patient body and the walking support system in an actual situation. Through some experiments it is confirmed that our algorithm enables the humanoid robot to start and stop stable walk with variable step length in the desired walking direction from a seated position and that it enables the robot to step aside and to go up and down stairs.