A new microrobot manipulation technique with high precision (nano level) positional accuracy to move in a liquid environment with diamagnetic levitation is presented. Untethered manipulation of microrobots by means of externally applied magnetic forces has been emerging as a promising field of research, particularly due to its potential for medical and biological applications. The purpose of the presented method is to eliminate friction force between the surface of the substrate and microrobot. In an effort to achieve high accuracy motion, required magnetic force for the levitation of the microrobot was determined by finite element method (FEM) simulations in COMSOL (version 5.3, COMSOL Inc., Stockholm, Sweden) and verified by experimental results. According to position of the lifter magnet, the levitation height of the microrobot in the liquid was found analytically, and compared with the experimental results head-to-head. The stable working range of the microrobot is between 30 µm to 330 µm, and it was confirmed in both simulations and experimental results. It can follow the given trajectory with high accuracy (<1 µm error avg.) at varied speeds and levitation heights. Due to the nano-level positioning accuracy, desired locomotion can be achieved in pre-specified trajectories (sinusoidal or circular). During its locomotion, phase difference between lifter magnet and carrier magnet has been observed, and relation with drag force effect has been discussed. Without using strong electromagnets or bulky permanent magnets, our manipulation approach can move the microrobot in three dimensions in a liquid environment.

This article presents an untethered magnetic manipulation technique for controlling a microrobot position under high rate laminar flows up to 4.5 mL/min. An increase in flow rate exponentially increases the drag force on the microrobot and negatively impacts its positioning accuracy. Increasing the longitudinal force generated by the microrobot’s driving apparatus helps in overcoming the disruptive effects of the fluid flow and increases longitudinal motion stability. To this end, we propose a magnetic configuration with two ring-shaped magnets, one above and the other below the microfluidic channel. This configuration causes the magnetic field lines emanating from the ring-shaped magnets to converge on both sides of the microrobot. Thus, the magnetic trapping forces that hold the microrobot in position are increased. To the best of our knowledge, no prior study exists on investigating the longitudinal motion for high flow velocities ( $>$ 5 mm/s). Investigating the longitudinal forces (along the x -axis) that affect a magnetically driven microrobot is a novel research topic that has many potential application areas, such as cell research, micromanipulation, and lab-on-a-chip systems. The microrobot’s dynamical motion is modeled as a second-order system, and using this model as a guideline, we demonstrate the ability of a microrobot in a square-shaped microfluidic channel ( $900$ $\times 900\,{\mu \text{m}}^{2}$ ) to follow a linear trajectory with a relative velocity up to 132.6 ${\text{mm/s}}$ . A straight and longitudinal trajectory of 4000 $\mu \text{m}$ has been successfully followed in the same and opposite directions to the flow for different flow rates (1–4.5 mL/min) and different robot speeds (10–50 mm/s).

Power quality problems are increasing with the widespread use of electronic equipments, which cause harmonic distortion of voltages and currents. Individually, a low power single-phase nonlinear load may not pose many serious harmonic problems but large concentrations of these loads have the potential to raise harmonic voltages and currents to unacceptable levels and harmonic current "pollution" is a one of the major power quality problem in electrical power systems. In this study, nonlinear resistance and harmonic models of the equipments with switch mode power supply (SMPS) are carried out using MATLAB^reg. Afterwards, Simulink^reg single-phase and three-phase simulations are developed for both phase and neutral harmonic activity analysis. The symmetrical components theory is implemented under balanced nonsinusoidal conditions.

The importance of an untethered microrobotic platform that can operate on high flowrate microfluidic channels for in vitro applications is increasing rapidly. This article presents a method to manipulate a microrobot in a fluidic chip when high flowrates (4 ml/min, 82.304 mm/s) are applied. This method is based on a novel permanent magnet-based diamagnetic levitation configuration. This configuration includes a thin layer of pyrolytic graphite, which is placed just below the microrobot. In this way, microrobot stability and manipulation capability are increased. Also, we aim to increase the longitudinal forces imposed on the microrobot to withstand the drag force proportional to the flowrate. Hence, magnetic field lines are generated more linearly around the microrobot by a different combination of permanent magnets. The proposed magnetic configuration, named “KERKAN configuration,” significantly improves the microrobot’s longitudinal forces. In this configuration, two different ring-shaped ferromagnetic magnets are used. One of the magnets has a smaller diameter than the other magnet. A combination of one smaller and one bigger magnet is placed above and below the microrobot. To validate the advantages of this configuration, analytical and simulation studies are conducted. Their results are then compared with experimental results. Experimental results are on par with analytical and simulation studies. KERKAN configuration has a lower displacement than the next best configuration at the highest flowrate we applied (relatively 3301 μm, %21.8).

In this study, a flexible conveyance system driven by linear motors and hybrid magnets for magnetic levitation is proposed. For modelling purposes, nonlinear analytic models are derived and extended to 3 axis of movement and controlled with those nonlinear equations. For energy efficiency, each pole is controlled with voltage driving zero power levitation method. Since the system only has displacement sensors for feedback, to fully control and understand the systems characteristics and disturbances, all axis are observed by disturbance observer and integrated to controller algorithm for better response and robustness, which is achieved multiplying the disturbance observer's output with system gain and feedforwarded. The proposed system and control algorithms are well confirmed by numerical results.

PRECISE POSITIONING OF DIAMAGNETICALLY LEVITATED MICROROBOT