University of Twente Student Theses
Design of magnetically actuated rotational joint with a locking mechanism based on shape memory polymer for minimally invasive surgery
Kroon, P.S. (2024) Design of magnetically actuated rotational joint with a locking mechanism based on shape memory polymer for minimally invasive surgery.
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| Abstract: | Robotic manipulators are a growing field of research due to their ability to assist in minimally invasive surgery. Recently, magnetically-actuated robots have been proposed that are highly manoeuvrable to access hard-to-reach surgical sites. These robots, which are actuated by an externally applied magnetic field, consist of multiple joints which need to be able to shape-lock and unlock separately in order for the robot to move. This thesis is about the design of a mechanical locking mechanism to shape-lock the degree of freedom of a 360° rotational joint for an end-effector for minimally invasive surgery. The end-effector consists of a 3D printed shaft which can rotate with respect to an outer housing because of a permanent magnet attached to its tip placed in an external magnetic field. Ceramic ball-bearings allow the rotation while a locking-mechanism blocks this rotation. The locking mechanism consists of a lasercut locking ring and a 3D printed beam connected to the shaft. The beam made from shape memory polymer (SMP) has two states. A stiff state in which rotation of the shaft is shape-locked until at least a torque of 4.2 Nmm and a soft state stimulated by heat in which the SMP is flexible and deforms, allowing rotation from a torque of 0.859 Nmm. Finite element analysis and calculations determine the deflection of the beam in a stiff state at 0.0983 mm and in a soft state at 1.333 mm. The maximum bending stress in the beam in a stiff state is 33.94 N/mm2 close to the yield strength of 40 MPa. Experiments in an electromagnetic coil setup confirm the locking mechanism shape-locks in a stiff state and rotates in a soft state. The design however has a backlash of 18 °in the locked state is a discrete locking mechanism. |
| Item Type: | Essay (Bachelor) |
| Faculty: | TNW: Science and Technology |
| Programme: | Biomedical Technology BSc (56226) |
| Link to this item: | https://purl.utwente.nl/essays/105102 |
| Export this item as: | BibTeX EndNote HTML Citation Reference Manager |
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