Navigation of mini swimmers in channel networks with magnetic fields

Controlled navigation of swimming micro robots inside fluid filled channels is necessary for applications in living tissues and vessels. Hydrodynamic behavior inside channels and interaction with channel walls need to be understood well for successful design and control of these surgical-tools-to-be. In this study, two different mechanisms are used for forward and lateral motion: rotation of helices in the direction of the helical axis leads to forward motion in the viscous fluid, and rolling due to wall traction results with the lateral motion near the wall. Experiments are conducted using a magnetic helical swimmer having 1.5 mm in length and 0.5 mm in diameter placed inside two different glycerol-filled channels with rectangular cross sections. The strength, direction and rotational frequency of the externally applied rotating magnetic field are used as inputs to control the position and direction of the micro swimmer in Y- and T-shaped channels

Comparison on experimental and numerical results for helical swimmers inside channels

Swimming micro robots are becoming feasible in biomedical applications such as targeted drug delivery, opening clogged arteries and diagnosis owing to recent developments in micro and nano manufacturing technologies. It has been demonstrated at various scales that micro helices with magnetic coating or attached to a magnet can move in fluids with the application of external rotating magnetic fields. The motion of micro swimmers interacting with flow inside channels needs to be well understood especially for medical applications where the motion of micro robots inside arteries and conduits in the body become pertinent. In this work, swimming of helical micro robots with magnetic heads inside tubes is modeled with the resistive force theory (RFT) and validated with experiments conducted in glycerin filled mini glass channels placed in rotational magnetic fields. The time-averaged forward velocities of magnetically driven micro swimmers that are calculated by the RFT model agree very well with experimental results

Design of a low-mass high-torque brushless motor for application in quadruped robotics

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 77).The Biomimetic Robotics Group is attempting to build the fastest quadruped robot powered by electromagnetic means. The limitations in achieving this goal are the torque produced from motors used to power the robot, as well as the mass and power dissipation of these motors. These limitations formulate the need for a lowmass high-torque low-loss motor. This thesis outlines the process of designing a permanent-magnet synchronous motor that meet the goals of the robot while minimizing the total mass. The motor designed from this thesis is compared to motors currently used by the Group when quantifying improvements made. In the process of achieving the goal, a design was formulated using fundamental electromagnetic principles. This design was then tested using finite element analysis. The final design was fabricated in house and wired by hand. The fabricated motor was tested to quantify key performance parameters such as peak cogging torque, peak motor torque, and thermal time constant under robot conditions. The motor designed by this thesis was able to produce more torque than the current motor being used by the Biomimetic Robotics Group, by a factor of 1.6, while decreasing the mass by 23%. A lower than desired packing factor was achieved since the motor was wired by hand resulting in a higher power dissipation and lower than expected motor torque. This design will be used in the quadroped robot after improvements are made to the cogging torque and packing factor.by Niaja Nichole Farve.S.M

A novel dual-rotor ultrasonic motor for underwater propulsion

Micro underwater vehicles (MUVs) have been highlighted recently for underwater explorations because of their high maneuverability, low price, great flexibility, etc. The thrusters of most conventional MUVs are driven by electromagnetic motors, which need big mechanical transmission parts and are prone to being interrupted by the variance of ambient electromagnetic fields. In this paper, a novel dual-rotor ultrasonic motor with double output shafts, compact size, and no electromagnetic interference is presented, characterized, and applied for actuating underwater robots. This motor was composed of a spindle-shaped stator, pre-pressure modulation unit, and dual rotors, which can output two simultaneous rotations to increase the propulsion force of the MUV. The pre-pressure modulation unit utilized a torsion spring to adjust the preload at the contact faces between the stator and rotor. The working principle of the ultrasonic motor was developed and the vibration mode of the stator was analyzed by the finite element method. Experimental results show that the no-load rotary speed and stalling torque of the prototype ultrasonic motor were 110 r/min and 3 mN m, respectively, with 150 V peak-to-peak driving voltage at resonance. One underwater robot model equipped with the proposed ultrasonic motor-powered thruster could move at 33 mm/s immersed in water. The dual-rotor ultrasonic motor proposed here provides another alternative for driving MUVs and is appropriate for developing specific MUVs when the electromagnetic interference issue needs to be considered. © 2019 by the authors

Design of an Autonomous Swimming Miniature Robot Based on a Novel Concept of Magnetic Actuation

Abstract-In this work, we propose a new concept for locomotion of a miniature jellyfish-like robot based on the interaction of mobile permanent magnets. The robot is 35 mm in length and 15 mm in width, and it incorporates a rotary actuator, a magnetic rotor, several elastic magnetic tails and a polymeric body embedding a wireless microcontroller and power supply. The novel magnetic mechanism is very versatile for numerous applications and can be tailored and adapted on the basis of different specifications. An analytical model of the magnetic mechanism allows to shape the robot design based on the specific application. The working principle of the robot together with the design, prototyping and testing phases are illustrated in this paper

Design and control of a voice coil actuated robot arm for human-robot interaction

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (leaf 68).The growing field of human-robot interaction (HRI) demands robots that move fluidly, gracefully, compliantly and safely. This thesis describes recent work in the design and evaluation of long-travel voice coil actuators (VCAs) for use in robots intended for interacting with people. The basic advantages and shortcomings of electromagnetic actuators are discussed and evaluated in the context of human-robot interaction, and are compared to alternative actuation technologies. Voice coil actuators have been chosen for their controllability, ease of implementation, geometry, compliance, biomimetic actuation characteristics, safety, quietness, and high power density. Several VCAs were designed, constructed, and tested, and a 4 Degree of Freedom (DOF) robotic arm was built as a test platform for the actuators themselves, and the control systems used to drive them. Several control systems were developed and implemented that, when used with the actuators, enable smooth, fast, life-like motion.by John M. McBean.S.M

Actuation, Sensing And Control For Micro Bio Robots

The continuing trend in miniaturization of technology, advancements in micro and nanofabrication and improvements in high-resolution imaging has enabled micro- and meso-scale robots that have many applications. They can be used for micro-assembly, directed drug delivery, microsurgery and high-resolution measurement. In order to create microrobots, microscopic sensors, actuators and controllers are needed. Unique challenges arise when building microscale robots. For inspiration, we look toward highly capable biological organisms, which excel at these length scales. In this dissertation we develop technologies that combine biological components and synthetic components to create actuation, sensing and assembly onboard microrobots. For actuation, we study the dynamics of synthetic micro structures that have been integrated with single-cell biological organisms to provide un-tethered onboard propulsion to the microrobot. For sensing, we integrate synthetically engineered sensor cells to enable a system capable of detecting a change in the local environment, then storing and reporting the information. Furthermore, we develop a bottom-up fabrication method using a macroscopic magnetic robot to direct the assembly of inorganic engineered micro structures. We showcase the capability of this assembly method by demonstrating highly-specified, predictable assembly of microscale building blocks in a semi-autonomous experiment. These magnetic robots can be used to program the assembly of passive building blocks, with the building blocks themselves having the potential to be arbitrarily complex. We extend the magnetic robot actuation work to consider control algorithms for multiple robots by exploiting spatial gradients of magnetic fields. This thesis makes contributions toward actuation, sensing and control of autonomous micro systems and provides technologies that will lead to the development of swarms of microrobots with a suite of manipulation and sensing capabilities working together to sense and modify the environment

Doctor of Philosophy

dissertationThis dissertation presents results documenting advancements on the control of untethered magnetic devices, such as magnetic \microrobots" and magnetically actuated capsuleendoscopes, motivated by problems in minimally invasive medicine. This dissertationfocuses on applying rotating magnetic elds for magnetic manipulation. The contributions include advancements in the way that helical microswimmers (devices that mimicthe propulsion of bacterial agella) are controlled in the presence of gravitational forces, advancements in ways that groups of untethered magnetic devices can be dierentiated and semi-independently controlled, advancements in the way that untethered magnetic device can be controlled with a single rotating permanent magnet, and an improved understanding in the nature of the magnetic force applied to an untethered device by a rotating magnet