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Design of a Setup for Simultaneous Control of Multiple Magnetic Microrobots

Khalesi, Ruhollah | 2022

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 55537 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Nejat Pishkenari, Hossein; Vossughi, Gholamreza
  7. Abstract:
  8. Microrobots (MRs) have attracted a lot of attention during recent years due to their promising biomedical applications. Due to their small size, these robots have limited capability to carry energy sources, sensors, or actuators, so researchers try to transfer energy from outside as much as possible. For this purpose, various actuation methods such as optical, acoustic, electric, and magnetic have been proposed. Magnetic field is the most used energy source. The current study deals with the design and implementation of a system for simultaneous independent control of multiple swimming magnetic MRs. The ability to control multiple MRs simultaneously and independently could lead to higher performance, and even make new applications possible. The two main methods for this purpose are the use of heterogeneous and homogeneous MRs. In the first category, MRs have different dimensions and magnetic properties, and will react differently against the same magnetic field. In the second category, MRs have the same properties and must be controlled independently by applying different fields or gradients. In current study, two novel designs based on heterogeneous MRs and one design based on homogeneous MRs are presented. For the heterogeneous MRs, dynamic equations are written and design parameters are discussed. Based on conducted simulation, three MRs controlled in 3D space simultaneously where the robot speed reaches 520 um/s. For homogeneous MRs, we have proposed a system for simultaneous and independent control of the position of multiple MRs in a plane. The system consists of 2N permanent magnets (PMs) with a circular arrangement in the plane around the workspace and a pair of Helmholtz coil to control N MRs. PMs are rotated by servomotors, and the coil aligns the orientation of the MRs normal to the plane. A sliding mode controller, as a robust approach, is designed to eliminate the undesired effects of disturbances and uncertainties. The position control of three MRs with dimensions of 250 µm, and a maximum speed of 330 µm/s is experimentally demonstrated using this controller. We’ve also improved the system’s stability by adding a larger MR (stabilizer MR). This MR can be moved all around the workspace and works as a moving internal magnetic field source. Thanks to this moveable magnetic field, other MRs are more stable against environmental disturbances. We illustrate simultaneous and independent control of multiple MRs by simulation and show the benefits of using the stabilizer MR (more than 20 percent reduction in tracking error and control effort). In addition, we evaluate experimentally our proposed method to independently control the position of three MRs using a stabilizer MR demonstrating the efficacy of the strategy. We also demonstrated a method for simultaneous control of two swarms using implemented setup by creating two stable equilibrium points. We also shown the validity of the simulation experimentally
  9. Keywords:
  10. Swarm Control ; Magnetic Fields ; Simultaneous Control ; Low Reynolds Number ; Swimming Microrobot ; Stabilizer Microrobot ; Heterogeneous Microrobot ; Independent Control ; Swimming Magnetic Microrobots

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