A Motion Control of Soft Gait Assistive Suit by Gait Phase Detection Using Pressure Information

Abstract

Power assistive devices have been developed in recent years. To detect the wearer’s motion, conventional devices require users to wear sensors. However, wearing many sensors increases the wearing time, and usability of the device will become worse. We developed a soft gait assistive suit actuated by pneumatic artificial rubber muscles (PARMs) and proposed its control method. The proposed suit is easy to wear because the attachment unit does not have any electrical sensors that need to be attached to the trainee’s body. A target application is forward walking exercise on a treadmill. The control unit detects the pre-swing phase in the gait cycle using the pressure information in the calf back PARMs. After the detection, the suit assists the trainee’s leg motion. The assist force is generated by the controlled PARM pressure, and the pressure input time is changed appropriately considering the gait cycle time. We conducted walking experiments; (1) verifies the proposed control method works correctly, and (2) verifies whether the gait assistive suit is effective for decreasing muscular activity. Finally, we confirmed that the accurate phase detection can be achieved by using the proposed control method, and the suit can reduce muscular activity of the trainee’s leg.

Leg Load Increase Training Using Soft Gait-assistive Suit and Its Experimental Validation

“…As described in Ref. 12, the load reduction experiment using the gaitassistive suit was carried out, and its performance was confirmed. However, the load increase experiment using the gait-assistive suit has not been evaluated.…”

“…In the load reduction experiment described in Ref. 12, the assisting force was applied during the activity period of the nearby muscle where the PARM was attached, and the electromyogram (EMG) signal was reduced in the gait cycle. On the other hand, in the proposed load increase training, an external force acting as a load is applied to the trainee's leg using the suit so that the muscle activity increases throughout the gait cycle.…”

“…The gait-assistive suit (12) used in this paper is shown in Fig. 1, which was upgraded from the suit described in Ref.…”

“…1, which was upgraded from the suit described in Ref. 12. A shoulder belt was installed to hang a waist supporter and prevent the deviation of the suit supporters' position caused by the PARM contraction force.…”

“…As one of the conventional research studies, the authors developed a gait-assistive suit that reduces leg load during walking. (12) This gait-assistive suit helps the trainees walk by actuating a pneumatic artificial rubber muscle (PARM) attached to the leg. The PARMs contract at appropriate timings in gait cycles, as determined by a proposed gait phase detection method.…”