Development of a Miniature 5-DOF Modularized Flexible Instrument With Distal Rotation Capability for Dual-Armed Upper Gastrointestinal Endoscopic Robots

The clinical endoluminal flexible instruments exhibit limited degrees of freedom (DOFs) and operational dexterity, making reorientation or repositioning challenging during the complex flexible endoscopic procedure, particularly in endoscopic submucosal dissection (ESD). This work presents a novel 5-DOF miniature flexible instrument for dual-armed upper gastrointestinal endoscopic robots with only 2.6 mm in diameter. It employs a continuum bending section featuring interlocking discrete joints and superelastic NiTi driving rods to achieve high dexterity, accurate positioning with inconspicuous motion hysteresis, and sufficient loading/clamping capacities. The design enables 360° unrestricted distal independent rotation of the forceps, unlike the entire rotation of typical flexible instruments. The central forceps movement slightly impacts the overall positioning accuracy of the instrument with a crosstalk error of less than 1 mm. Kinematic parameter calibration improves the instrument's motion accuracy, achieving an average distal positioning error of 1.56 mm within ±100° in the 2-D plane and 2.29 mm in 3-D space. The distal loading stiffness is 0.29 N/mm and the clamping force exceeds 0.8 N, providing adequate tissue interaction forces during ESD procedures. The modularized instrument prompts the seamless integration of diverse surgical tools, ultimately establishing a dual-armed endoscopic robot. Ex-vivo experiments have been performed to verify its effectiveness in ESD procedures.