A Soft-Inflatable Exosuit for Knee Rehabilitation: Assisting Swing Phase During Walking

Abstract

In this paper, we present a soft-inflatable exosuit to assist knee extension during gait training for stroke rehabilitation. The soft exosuit is designed to provide 25% of the knee moment required during the swing phase of the gait cycle and is integrated with inertial measurement units (IMUs) and smart shoe insole sensors to improve gait phase detection and controller design. The stiffness of the knee joint during level walking is computed using inverse dynamics. The soft-inflatable actuators, with an I cross-section, are mechanically characterized at varying angles to enable generation of the required stiffness outputs. A linear relation between the inflatable actuator stiffness and internal pressure as a function of the knee angle is obtained, and a two-layer stiffness controller is implemented to assist the knee joint by providing appropriate stiffness during the swing phase. Finally, to evaluate the ability of the exosuit to assist in swing motion, surface-electromyography (sEMG) sensors are placed on the three muscle groups of the quadriceps and two groups of the hamstrings, on three healthy participants. A reduction in muscle activity of the rectus femoris, vastus lateralis, and vastus medialis is observed, which demonstrates feasibility of operation and potential future usage of the soft inflatable exosuit by impaired users.

Knee Joint Biomechanics in Physiological Conditions and How Pathologies Can Affect It: A Systematic Review

“…There are about 7.0 million stroke survivals in China and 6.6 million in the United States [109,110]. Stroke is known as the cause of paralysis, loss of motor function, paresis-weakness of muscle, plegia-complete loss of muscle action, and muscle atrophy [34,108,109]. Impaired walking and sit-stand transition are the main reason that poststroke patients cannot live independently [107,108].…”

“…Impaired walking and sit-stand transition are the main reason that poststroke patients cannot live independently [107,108]. And about 30% of poststroke patients have difficulty in ambulation without assistance [109]. Some evidences showed that 70% of poststroke patients can recover their walking capabilities by rehabilitation [108,111].…”

“…The biomechanical effects of stroke were shown in Table 14. Sridar et al [109] indicated that the kinematic and kinetic performance of the poststroke patients will degrade, such as reduced walking speed, quadriceps muscle moment, and quadriceps muscle power. Chen et al [112] revealed that the poststroke patients had lower knee flexion in the swing phase of walking.…”

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

“…This suit uses electric foot switches for the motion detection. Sridar et al [29] developed a soft-inflatable exosuit for knee rehabilitation. This device uses IMUs and shoe insole sensors.…”

Development and validation of a soft robotic exosuit for assistance of the upper limbs

“…Exosuits actively transmit power to the human body either using cables, moved by electric motors (Figure 2.3.b), or soft pneumatic actuators (Figure 2.3.c), embedded in the garment. The latter paradigm was probably among the first to be proposed [41] and has been explored to assist stroke patients during walking [42], to increase shoulder mobility in subjects with neuromuscular conditions [43], to help elbow movements [44] and for rehabilitation purposes to train and aid grasping [45][46][47].…”