Novel Design Optimizes Electromagnetic System for Safer Eye Surgery

In a recently published study in Cyborg and Bionic Systems, researchers introduced a new type of electromagnetic drive system. It uses a control framework based on an Active Disturbance Rejection Controller (ADRC) and virtual boundary, and it comprises eight optimized electromagnets placed in an optimal configuration. The flexible 5-DOF magnetic manipulation of a micro-robot inside the posterior eye is proposed for precise targeted drug delivery.

Robot-assisted surgery has replaced traditional handheld surgical instruments in intraocular microsurgery because it can more accurately perform motion scaling and efficiently mitigate physicians' physiological tremors during procedures.

As they get closer to the posterior eye, robot-assisted instruments can inadvertently place the instruments too deeply or apply too much scleral force under the surgeon's control. This could cause stress to the retina or sclera, resulting in bleeding or severe injury. This has led to the incidence of intraoperative and postoperative problems ranging from 2 % to 30 %.

Comparing these 5-DOF electromagnetic drive systems to the current robotic-assisted systems, a new actuation paradigm is presented. The micro-robot is a safer tool for interacting inside the posterior eye since it usually uses a force-controlled mode instead of a position-controlled mode.

The force-controlled mode of the electromagnetic drive system can effectively reduce the possibility of irreversible retinal injury by restricting interaction forces, even when the patient moves or the device malfunctions. Nevertheless, producing strong magnetic fields and forces in a large workspace is difficult.

As a result, there has been a growing interest in optimizing the electromagnet parameters and system configuration to produce a strong magnetic field and magnetic force generation capability. Appropriate control framework research is required due to disturbances caused by various variables, including changes in the liquid environment's interaction forces and erroneous electromagnetic coil modeling.

To address the aforementioned problems, the researchers introduce a unique electromagnetic driving system for 5-DOF magnetic manipulation in ophthalmic microsurgery. To improve the ability to work continuously, a two-step design optimization process that aims to find the ideal system configuration and electromagnet parameters has been created and implemented.

By implementing the suggested configuration optimization process and multi-objective electromagnet optimization, the system has enhanced its ability to operate steadily and precisely and its capacity for prolonged operation. The system uses a virtual border and ADRC controller-integrated control architecture to improve security and resilience in intraocular microsurgery.

Simulation and analysis have been conducted to assess the effects of the suggested design optimization and control framework. The proposed control framework, which incorporates the ADRC controller and virtual boundary, is used to implement trajectory tracking performance testing and performance evaluation in various operation modes.

Its efficacy and performance are validated in comparison to PID and TDE controllers. With reductions ranging from 47.1 % to 65.4 % and 62.7 % to 84.4 %, respectively, the results show a considerable drop in both the maximum error and maximum RMS error during disturbance-free performance tests.

Furthermore, disturbances missed by previous related efforts have also been considered in the performance testing carried out in this work.

The obtained findings demonstrate the system's exceptional resilience to shocks, with the maximum error and RMS error less than 172.2 and 35.8 μm, respectively.

The researchers plan to utilize an even more precise magnetic field-current model to improve usable workspace inside the open volume and positioning precision. In addition, future research will investigate the application of Fiber Bragg Grating (FBG)-based real-time magnetic temperature detection to improve safety precautions.

Yangyu Liu, Dezhi Song, Guanghao Zhang, Qingyu Bu, Yuanqing Dong, and Chaoyang Shi from the University of Tianjin, Tianjin, and Chengzhi Hu from the Southern University of Science and Technology, Shenzhen, are co-authors.

The study was funded by the National Natural Science Foundation of China.

Journal Reference:

‌ Liu, Y., et al. (2024) A Novel Electromagnetic Driving System for 5-DOF Manipulation in Intraocular Microsurgery. Cyborg and Bionic Systems. doi.org/10.34133/cbsystems.0083