Design, Modeling, and Control of a Compact SMA-actuated MR-conditional Steerable Neurosurgical Robot

The letter presents a compact shape memory alloy (SMA)-actuated magnetic resonance (MR)-conditional neurosurgical robotic system. It consists of a 2-degree of freedom (DoF) cable-driven steerable end effector, an antagonistic SMA springs-based actuation module, and a quick-connect module, packaged into a single integrated device measuring 305 mm length × 76 mm diameter. The system is also highly adaptable, such that it could operate a cable-driven end effector up to a maximum of 4-DoFs and its length can be easily modified due to the acrylic plate-based modular construction. In addition to the kinematics of the robotic end effector and the SMA constitutive model, we also present the antagonistic SMA springs model under the known tension and cable displacement from the robotic end effector. We performed extensive characterization experiments to obtain SMA model parameters and integrated a feedforward component in our controller to achieve improved tracking of a sinusoidal reference up to 80° bending angle amplitude and 100 s period. Lastly, proof-of-concept robot demonstrations were performed in a gel phantom and in the MRI that confirmed the robot motion capability in the brain and MRI compatibility of the robot.