Modular Soft Exoskeleton Design and Control for Assisting Movements in Multiple Lower Limb Joint Configurations

Soft lower limb exoskeletons have shown potential to enhance mobility in patients with motor disorders and improve their quality of life. This study introduces a novel modular soft lower-limb exoskeleton that provides assistance to a single hip joint or/and a single ankle joint, configurable on either the left or right side according to clinical needs. The control system employs adaptive gait phase recognition and a hierarchical strategy to accurately identify user intentions and track desired assistance profiles. An assistance profile optimization method is also designed based on the users’ muscle surface electromyography signals, aiming to further enhance the adaptability of robotic assistance to different users and tasks. Multi-subject experiments were conducted with 10 participants. The experimental results demonstrated that the exoskeleton exhibited good modular performance and effectively assisted walking under different configurations. Specifically, compared to natural walking, the exoskeleton assistance reduced the net metabolic rate by up to 15.29% while the hip and ankle joints are assisted simultaneously. Furthermore, the optimized assistance profiles achieved lower metabolic rates and reduced muscle activation compared to the generic assistance. Note to Practitioners—Lower-limb exoskeletons are becoming an essential tool for improving mobility in individuals with motor impairments, yet many existing systems lack the flexibility to adapt to varying user needs and movement patterns. This work addresses this challenge by introducing a modular wearable suit and targeted optimized assistance profile to soft lower-limb exoskeletons that allow for personalized assistance at the hip and ankle joints. The system is designed to be highly flexible, enabling different combinations of joint assistance based on the user’s specific requirements, making it suitable for a wide range of rehabilitation and assistive applications. Stroke survivors with unilateral challenges or patients requiring partial joint support can benefit from this approach. To achieve this, the system employs an adaptive gait phase recognition method and hierarchical control strategy to ensure accurate tracking of user intentions and the use of corresponding assistance profiles. Additionally, the profiles are optimized using surface electromyography signals, enhancing the system’s ability to adjust to individual users and tasks. Experiments demonstrated that the use of the exoskeleton reduced the respiratory metabolic rate and muscle activation of the subjects while walking, and it also had good modular performance and could provide diverse assistance. While promising, current testing is limited to controlled environments. Further research is needed to validate the system in real-world scenarios, assess long-term durability, and explore multi-patient experiments. Future work will focus on enhancing multi-joint coordination, long-term stability, and integration into broader rehabilitation settings.