Emergency Position Recovery Using Forward Kinematics in Robotic Patient Positioning Systems for Radiosurgery

Precise patient positioning is paramount in radiosurgery to ensure the accurate targeting of tumors while minimizing damage to surrounding healthy tissues. This study focuses on the development and validation of a robust forward kinematics (FK) model for a robotic patient positioning system, specifically designed to handle emergency interruptions such as power loss or emergency stops. The FK model integrates data from high-resolution primary encoders within the actuators and secondary encoders post-load on each axis, providing real-time feedback and ensuring sub-millimeter positional accuracy. The control architecture leverages a dual-loop feedback system to enhance precision and stability during operation and recovery. The simulation and experimental results demonstrate that the FK model, combined with encoder feedback, reliably determines the patient bed's exact position during interruptions and guides the system's safe and accurate resumption of treatment. These findings underscore the critical role of FK and encoder integration in improving the safety, reliability, and precision of robotic radiosurgery systems, addressing key challenges in medical robotics for radiation therapy.