Bionic Bird Claw Design for Grabbing and Perching Inspired by Tendon-Locking Mechanism

This letter proposes a novel bionic bird claw with a digit-locking mechanism inspired by a tendon-locking mechanism (TLM). First, the biological mechanisms of both the bird digit-locked TLM (tendon locking) and the leg automatic digit flexion mechanism (ADFM) (quick digit flexion) of birds are introduced. Then, a digit-locking mechanism that locks the flexion tendon on the digit based on the TLM is proposed, requiring only a tensioned cable to unlock the digit. A parallelogram fold leg mechanism is designed based on the ADFM to drive the digit's flexion and locking motions. The digit locking and unlocking statics, the claw's gripping range, and the gripping force were analyzed. Finally, a prototype is developed, and several experiments are conducted to measure digit locking and unlocking force, digit loading, claw gripping range, claw loading capability, and multi-angle dive grabbing of the claw. The load-to-weight ratio of the claw is 45.0-87.6. Moreover, the success rate of claw-grasping branches is found to reach 95${\%}$. The bionic bird claw closely mimics the TLM of the bird claw and demonstrates high reliability, serving as a valuable reference for unmanned aerial vehicles in perching, grabbing, and carrying tasks.