Abstract:Objective To address the ankle dorsiflexion disorder during gait swing in patients with foot drop, a lightweight, unpowered ankle dorsiflexion assist exoskeleton was designed to achieve precise mechanical assistance and verify its biomechanical efficacy. Methods Based on the biomechanical model of the ankle joint, a ratchet and pawl mechanism is adopted to control the energy storage and release sequence of the torsion spring. Lightweight exoskeletons are fabricated by applying FDM 3D printing technology and using PLA-related materials. The gait data of patients with foot drop after wearing exoskeletons were synchronously collected through the Vicon motion capture system, AMTI force platform and Ultium EMG electromyography system, and the kinematic, dynamic and electromyographic parameters of the affected side and the healthy side were compared. Results The ratchet pawl timing control mechanism responds rapidly, and the maximum torque of the back-flexion assist can reach 10N·m. In the middle stage of swing on the affected side, the dorsiflexion Angle was basically restored, effectively eliminating the phenomenon of toe dragging on the ground, and the symmetry of sagittal plane movement of the ankle joint was significantly improved. The root mean square (RMS) value of electromyography on the affected side decreased significantly: approximately 28.14% for the gastrocnemius muscle, approximately 41.41% for the peroneus longus muscle, and approximately 17.36% for the tibialis anterior muscle. The total mass of the device is approximately 483g, and the selected materials meet the strength requirements. Conclusions This unpowered exoskeleton precisely releases the energy stored by the torsion spring during plantar flexion through a ratchet and pawl mechanism, significantly improving the ankle dorsiflexion function and reducing the compensatory load on the muscle group. The 3D printing customized process provides a new paradigm for lightweight rehabilitation equipment. Low structural weight, maintaining the stability of mechanical properties.