Tethered Magnetic Serial Robots for Minimally Invasive Neurosurgery

The high-speed, non-ionizing, wireless power transfer capabilities of low-frequency magnetic fields make them an attractive option for actuating devices on the nanometer scale up to the centimeter scale, enabling a new suite of minimally-invasive techniques for a wide variety of medical procedures. There is a significant demand for smaller, more manoeuvrable, surgical robot tools to reduce the invasiveness of neurosurgical procedures. A magnetic approach to surgical robots could enable smaller tools, but no viable magnetic robot approach exists. Existing magnetic approaches to surgical tasks involve either untethered agents, serial arms with bulky surface-mount transmission units, or highly-underactuated continuum bodies. Surgical tasks, especially in delicate regions such as the brain, require precisely controlled trajectories and applied forces: they require fully-actuated robots.In this thesis, rigid-link serial robots with embedded magnets in each link are designed to achieve high forces and ensure full actuation over their configuration space. A novel analytical model was derived from a combination of magnetostatics and rigid-link serial robot dynamics to determine the equivalent actuator torques at the joints of the serial robot for a given actuating field, as well as the effective torsion-spring-like behaviour induced by interactions between the magnets in the serial robot. From this analytical model, a performance metric and novel design methodology was developed to improve the actuation performance and tailor the magnetic torsion-spring behaviour in the robot by adjusting the orientation and position of the embedded magnetic material. Several 3 mm - 4 mm diameter rigid-link robot prototypes were developed using this methodology, and their performance was evaluated according to key design criteria for microneurosurgical tasks. The tools can be operated open loop or closed loop with computer vision feedback, achieving step response rise times of less than 1 second and maximum output forces of up to 181 mN. By enabling smaller tools without a need for transmission components, more space is left in the trocar (surgical insertion point) for other systems, such as lighting, irrigation, or integrated sensing. Magnetic serial robots could thus enable a new class of multifunctional surgical tools.

Department dc:contributor.department

Mechanical and Industrial Engineering

Year dc:date.issued

2023

Author dc:creator

• Forbrigger, Cameron

Advisor dc:contributor.advisor

• Diller, Eric D

• Magnetic actuation
• Minimally invasive surgery (MIS)
• Robot surgery

Handle dc:identifier.uri

http://hdl.handle.net/1807/126916

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/126916