Magnetic interaction can be utilized for remote actuation of surgical manipulators. However, platforms currently available for that purpose have limited workspaces, inadequate field strength or very low bandwidth of the electrical subsystem. In this paper, we present BigMag, a novel platform capable of magnetic steering of continuum manipulators for medical purposes. BigMag comprises of 6 mobile coils and is capable of generating the fields of at least 40 mT in any direction at every point of its workspace. Moreover, we introduce a mathematical model for 3D mobile coil arrays. Each coil is modelled using finite element data adjusted by measurementbased correction, (a maximum observed mean error between the model and the prediction of 3.36 ± 5.62%). The model for a full system is validated in two tasks. In the first task, the system executes a prescribed rotating field (mean error between the model and measurement of 7.51% and minimum R 2 of 0.964). The second task tests the estimation of the field for known 3D trajectories (minimum R 2 of 0.967). The investigation concludes with a demonstration of BigMag capabilities in actuation of magnetic catheters in confined spaces usinguser-controlled steering.

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Magnetic soft robots have the combined advantages of contactless actuation, requiring no on-board power source, and having flexible bodies that can adapt to unstructured environments. In this study, four milli-scale soft robots are designed (Inchworm, Turtle, Quadruped and Millipede) and their actuation under external magnetic fields is investigated with the objective of reproducing multi-limbed motion patterns observed in nature. Magnetic properties are incorporated into a silicone polymer by mixing in ferromagnetic microparticles (PrFeB) before curing. The magnet-polymer composite is used to fabricate soft magnetic parts, with predetermined magnetization profiles achieved using a 1 T field. The resulting soft robots are actuated under external magnetic fields of 10-35 mT which are controlled using an array of six electromagnetic coils. The achieved motion patterns are analyzed over five iterations and the motions are quantified in terms of body lengths traversed per actuation cycle and speed of displacement. The speed of the specimens is calculated to be in the range of 0.15-0.37 mm/s for the actuation field used here. The ability of the soft robots to traverse uneven terrain is also tested, with the Turtle and the Millipede demonstrating successful motion.

Automated steering of endovascular catheters has a potential of improving the outcome of minimally invasive surgical procedures. Nevertheless, actuation, tracking, and closed-loop position control of catheters remain a challenge. In this study, we present a modular framework for a three-dimensional (3-D) position control of magnetically actuated endovascular catheter. The catheter is fitted with a permanent magnet and deflected using externally generated magnetic field provided by BigMag-An array of mobile electromagnets. Pseudorigid-body modeling is used to formulate an inverse-model closed-loop position controller of the catheter. The shape feedback is reconstructed from a 3-D point cloud of catheter silhouette, obtained using stereo vision. Magnetic actuation is enabled using an inverse field map technique, mapping the reference magnetic field to BigMag configuration variables. The framework is tested in a series of experiments. The inverse map is validated, showing a mean magnetic field error of 2.20%. The accuracy of the shape reconstruction algorithm is 0.59 mm. Finally, the magnetically actuated catheter is steered across a series of trajectories with maximum reported catheter deflection of 68.43 • and maximum tip speed of 5 mm/s. Across all trajectories, the best control performance metrics are the mean error of 0.57 mm and the RMS error of 0.77 mm.

Automation of flexible surgical instruments requires the development of robotic technologies capable of small-scale power transmission. Magnetic actuation has successfully been used for that purpose. Nevertheless, current systems for magnetic actuation suffer from small workspaces or poor bandwidth of magnetic field control. In this work, we design, develop, and test a novel magnetic actuation system called Advanced Robotics for Magnetic Manipulation (ARMM). The ARMM system employs a 6 DoF mobile electromagnetic coil capable of generating prescribed magnetic fields and gradients. The mobile coil approach allows for easy scaling of the actuation workspace, which depends on the range of robotic arm, and in our case spans up to 1.3 m. Due to limited end-effector payload of the robotic arm used in the ARMM system, the mobile coil has been designed using an optimization routine. For a given mass and heat dissipation constraints, this routine provides the coil geometry that maximizes the average magnetic field generated in the target region. Since the Vacoflux core of the fabricated coil saturates within operational conditions, we propose an actuation strategy employing an online-updated iterative map technique. Using this map, the ARMM system allows for precise generation of prescribed magnetic fields and gradients at the point of interest, while taking into account the effects of the non-linearities due to core saturation. The strategy is validated experimentally, showing the average error of 2.34% for magnetic field and 7.20% for the magnetic field gradient.