Kinematic and static analysis of a rigid-flexible hybrid robot with combined elastomer configuration of driving shafts and spinal rods

Flexible shafts, exhibiting excellent tensile and torsional transmission characteristics, serve as an ideal power transmission medium for the design of flexible continuum robots. This study introduces a novel rigid-flexible hybrid robotic mechanism employing six flexible shaft actuators to achieve seven degrees of freedom (DOFs). The design integrates a dual-segment flexible body with a single-segment rigid body. A comprehensive kinematic model was derived to describe the hybrid structure’s motion. Concurrently, a static model was developed, incorporating driving forces, external loads, gravitational effects, and the combined elastic forces from the flexible driving shafts and spinal rods. Based on this static model, 182 combinations of flexible shaft pulling forces and distal loads were applied to control the robot’s posture. Experimental results indicated that the maximum positional errors for the single- and dual-segment configurations were 2.67% and 5.97% of the manipulator length, respectively. The maximum root mean square error for spatial configuration repeatability is 0.4 and 5.1 mm for single- and dual-segment flexible robots, respectively. The kinematic and static models developed in this research accurately predict the spatial configuration of the flexible continuum robot, which features an integrated elastic arrangement of driving shafts and spinal rods, thereby facilitating rapid deployment in similar flexible robotic systems.