Load-adaptive shape sensing and control of a tendon-driven continuum robot actuated by SMA springs

In this paper, a load-adaptive continuum robot with accurate shape sensing and control capabilities through tendon tension modulation is presented. First, three shape memory alloy (SMA) springs actuate the bioinspired continuum robot to achieve 3D deformation. Second, the bending shape can be accurately estimated in real time using the tensions of the SMA springs based on the forward kinematics of a modified Cosserat model that considers friction between the tendons and disks. For a desired position, the required tensions of the SMA springs can be obtained using the inverse kinematics of the proposed model. Finally, a closed-loop control method is implemented to test the continuum robot’s shape control performance. Experiments demonstrate that the robot exhibits accurate tracking results for different complex trajectories, both with and without an external load at the end effector, based on the proposed model’s forward and inverse kinematics. In conclusion, SMA actuation combined with tension feedback control enables accurate load-bearing capacity, shape sensing, and position tracking, representing a promising approach for developing future design guidelines for continuum robots.