Designing a Bow-Inspired Rigidable Exosuit for Adaptive Support

This letter introduces a “rigidable exosuit” inspired by bow mechanics, which can dynamically alter its frame rigidity based on the tension of the attached string. The exosuit affords posture assistance (rigid phase) or unrestricted movement (flexible phase) as required by tasks. In the flexible phase, relaxed strings enable free shoulder and waist movements, reducing entanglement likelihood. Conversely, during strength-demanding tasks (rigid phase), pulled strings provide waist support. The tension in the string enables seamless transitioning between rigid and flexible configurations as required by the task at hand. The waist posture support prototype features a carbon fiber reinforced plastic bow structure and a tension control mechanism utilizing a twisted string actuator. Experiments using the prototypes demonstrated that movements in the flexible phase were comparable to those in the unworn states. During the rigid phase, while performing lifting tasks, the erector muscle electromyography signal decreased by over 20% and the motion angle by approximately 40% after wearing the device. The exosuit thus has significant potential to enhance human performance across various physical activities and implications in wearable robotics. By providing seamless transitioning between rigid and flexible configurations, the exosuit can aid support workers in diverse occupational settings, ultimately improving safety and productivity.