In robotic automation, compact layouts and the limited range of measurement devices often confine the robot’s calibration space, leading to ill-conditioned Jacobian matrices for length parameters and significant estimation errors. To address this issue, joint configurations in the confined calibration space are modeled as perturbations around those under a fixed end-effector position. By applying matrix perturbation theory, the relationship between the smallest singular value of the identification matrix and the joint configuration perturbations is established. Building on this theoretical basis, a novel dual-tool distance constraint method is introduced to alleviate the ill-conditioning of the identification matrix and enhance parameter identification accuracy. The proposed method was validated using an ABB IRB 4600 industrial robot. Experimental results in the confined calibration space demonstrate that, compared with conventional methods, the proposed approach not only mitigates ill-conditioning but also significantly improves the robot’s positioning accuracy.

Robot-assisted gastrointestinal endoscopic surgery (RAGES) has emerged as a critical approach for minimally invasive procedures, including Endoscopic Submucosal Dissection, polypectomy, hemostasis, and therapeutic interventions. However, manual manipulation of flexible endoscopes remains technically demanding and limits surgical precision. To enhance surgical efficiency, this paper proposes a joystick-controlled Endoscopic Robotic System (ERS) comprising a Flexible Arm Delivery Device (FDD) and Main Body Driving Device (MDD). Through systematic structural design and validation, the ERS achieves stable four-DOF control: 360° circumferential rotation, 180° bending, 280–330 mm axial delivery, and ±15° rotational compensation. Key innovations include dual-encoder slippage detection in the FDD and a gripper assembly addressing circumferential angle loss through real-time torque sensing. Experimental results confirm compatibility with dual-channel endoscopes without custom modifications. The system demonstrates proof-of-concept for comprehensive endoscopic control while maintaining compact design (<0.2 m² per module) and low manufacturing cost. Although force-sensing capabilities require further refinement, this work establishes a foundation for accessible robotic platforms in gastrointestinal endoscopy, with identified limitations guiding future development toward clinical viability.