Study examines electromagnetic driving system for 5-DOF manipulation in intraocular microsurgery

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A team of researchers in China recently detailed a novel electromagnetic driving system that consists of 8 optimized electromagnets arranged in an optimal configuration and employs a control framework based on an active disturbance rejection controller (ADRC) and virtual boundary.

According to a Beijing Institute of Technology news release, the electromagnetic driving systems are proposed for the flexible 5-DOF magnetic manipulation of a micro-robot within the posterior eye, enabling precise targeted drug delivery.¹

The team recently published their findings in Cyborg and Bionic Systems.² The research was supported by the National Natural Science Foundation of China

The researchers noted that intraocular microsurgery has been fertile ground for innovation, transitioning from the utilization of conventional handheld surgical tools to the adoption of robot-assisted surgery, owing to its ability to effectively mitigate the surgeons’ physiological tremors during procedures and achieve precise motion scaling.

However, the researchers explained that the closer to the posterior eye they get, robot-assisted devices could inadvertently position the instruments too deeply or exert too much scleral force under the surgeon’s control, which can damage the retina or sclera and result in hemorrhages or even severe injury. These issues have led to the incidence of intraoperative and postoperative complications ranging from 2% to 30%.¹

According to the news release, the 5-DOF electromagnetic driving systems can create an actuation paradigm compared with the existing robotic-assisted systems. The system typically uses a force-controlled mode instead of a position-controlled mode, which makes the micro-robot a safer instrument for interacting within the posterior eye. In force-controlled mode, the electromagnetic driving system can minimize the risk of causing irreparable retinal damage by imposing limits on interacting forces, even in situations involving patient movement or system failure.

However, generating high-intensity magnetic fields and magnetic forces within a large workspace can prove to be a challenge. As a result, the researchers noted the design optimization of the system configuration and electromagnet parameters for providing a high magnetic field and magnetic force generation capacity has been emerging and attracting broad attention.

As a result, it is key study suitable control frameworks due to disturbances introduced by many factors such as inaccurate modeling of electromagnetic coils, changes in interaction forces in the liquid environment.¹

In order to address those issues, the research team offers a novel electromagnetic driving system for 5-DOF magnetic manipulation in intraocular microsurgery. Two-step design optimization trying to secure optimal system configuration and electromagnet parameters have been presented and implemented to enhance the capacity for sustained work. With the proposed configuration optimization procedure and the multi-objective optimization of the electromagnets, the system can perform a more precise and stable manipulation and has obtained a stronger capacity for sustained work.

According to the news release, the system utilizes a control framework incorporating the ADRC controller and virtual boundary to enhance robustness and security in intraocular microsurgery.

Researchers performed simulation and analysis in order to evaluate the influences of the proposed design optimization and control framework. They explained the performance evaluation and trajectory tracking performance tests in different operation modes were implemented with the presented control framework incorporating the ADRC controller and virtual boundary, validating its performances and effectiveness compared with PID and TDE controllers.¹

The results, according to the news release, indicate a decrease in both the maximum error and maximum RMS error during disturbance-free performance tests, with reductions ranging from 47.1% to 65.4% and 62.7% to 84.4%, respectively.

Moreover, the performance tests conducted in this work have additionally taken into account disturbances that were overlooked by other related works. The obtained results demonstrate the system’s remarkable robustness in the presence of disturbances, as evidenced by the maximum error and RMS error being below 172.2 and 35.8 μm, respectively.¹

Meanwhile, the realization of virtual boundaries enhances interactive security by facilitating collision avoidance. Hence, the proposed system is more suitably designed for performing intricate magnetic manipulation within the posterior eye during intraocular microsurgery.²

“Characterization experiments have been conducted to evaluate the performances of the proposed system in terms of magnetic field generation capacity, thermal performance under natural heat dissipation, and trajectory tracking performance with disturbances,” the researchers concluded in the study. “Future work will further consider the robotization and integration of additional instruments for the micro-robot’s injection with the proposed 5-DOF electromagnetic driving system to form a milli-micro combination ophthalmic surgical system.”

Looking to the future, the researchers will employ a more accurate magnetic field-current model to further enhance the positioning accuracy and enhance usable workspace within the open volume. Furthermore, future work will also explore implementing fiber Bragg grating (FBG)-based real-time detection of electromagnet temperatures, aiming to enhance safety measures.

References:

1. A novel electromagnetic driving system for 5-DOF manipulation in intraocular microsurgery. EurekAlert! Published May 31, 2024. Accessed June 2, 2024. https://www.eurekalert.org/news-releases/1046491

2. Yangyu Liu, Dezhi Song, Guanghao Zhang, Qingyu Bu, Yuanqing Dong, Chengzhi Hu, Chaoyang Shi. A Novel Electromagnetic Driving System for 5-DOF Manipulation in Intraocular Microsurgery. Cyborg Bionic Syst. Published March 24, 2024. Accessed June 2, 2024.2024;5:0083.DOI:10.34133/cbsystems.0083