skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Feedback Stabilization of a Permanent Magnet Levitation System
A magnetic levitation system consists of a magnet facing groundward to attract a magnetic object against gravity and levitate it at a distance from the face of magnet. Due to the unstable nature of this system, it must be stabilized by means of feedback control, which adjusts the magnetic force applied to the levitating object depending on its measured position and possibly velocity. Conventionally, electromagnets have been used for magnetic levitation, as they can be simply controlled via their terminal voltages. This paper, however, studies a levitation system relying on a permanent magnet and a linear servomotor to control the applied magnetic force by changing the distance between the magnet and the levitating object. For the proposed system, which is highly nonlinear, a stabilizing feedback control law is developed using feedback linearization and other control design tools. Then, the closed-loop stability is examined against system parameters such as the size of the levitating object, the viscosity of the medium it moves in, and certain characteristics of the magnet in use. The emphasis here is on understanding the impact of intrinsic servomotor limitations, particularly its finite slew rate (cap on its maximum velocity), on the ability of feedback control to stabilize the closed-loop system. This particular limitation seems to be a major concern in utilizing permanent magnets for noncontact actuation and control.  more » « less
Award ID(s):
1941944
PAR ID:
10398927
Author(s) / Creator(s):
;
Date Published:
Journal Name:
2022 American Control Conference (ACC)
Page Range / eLocation ID:
5087 to 5092
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; (, IEEE)
    This paper presents the design, implementation, feedback stabilization, and experimental validation of a novel permanent magnet levitation system. Conventionally, magnetic levitation systems utilize electromagnets to levitate magnetic objects against gravity by stabilizing them around equilibrium points at which the applied magnetic force balances the gravity. This magnetic force must be dynamically adjusted by means of a stabilizing feedback loop, which is established by easy control of the electromagnet voltage. Despite the key advantage of easier control, electromagnets often produce much weaker magnetic forces compared to permanent magnets of similar size, weight, and cost. Therefore, this paper proposes the use of a permanent magnet to produce the magnetic force necessary for levitation, and the use of a linear servomotor to control the magnitude of this force by adjusting the distance between the magnet and the levitating object. To demonstrate this idea in practice, an experimental setup is designed, prototyped, and successfully stabilized using a computer-based feedback control loop. 
    more » « less
  2. ; ; (, IEEE)
    This paper presents the concept, implementation, feedback control, and experimental verification of a noncontact magnetic manipulator that relies on a controllable array of permanent magnets to manipulate magnetized objects inside a workspace encircled by the magnets. To gain control over the aggregate magnetic field inside the workspace, the position of each magnet is independently controlled by a linear servomotor that dynamically changes the distance between that magnet and the workspace. By feedback control of the array of servomotors, the magnetic force applied to a magnetized object inside the workspace is dynamically adjusted to steer it along a desired reference trajectory. The successful steering of a small magnetic bead is demonstrated by experiments performed on a planar magnetic manipulator, designed and prototyped with six linear servomotors and six permanent magnets. 
    more » « less
  3. ; (, 2020 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM))
    null (Ed.)
    A magnetic manipulator for noncontact steering of magnetic objects is considered. This system utilizes a flexible array of permanent magnets, each equipped with a servomotor to independently control its direction. The total magnetic field produced by the magnets can be shaped effectively by adjusting the directions of all magnets, which in turn, provides an effective control over the magnetic force it applies to a magnetic object. The dynamics of this object under such controlled magnetic force is inherently unstable and is represented by a set of highly nonlinear state-space equations. Despite the nonlinear nature of these equations, it is shown that an optimally designed linear state feedback can successfully stabilize the object and steer it along arbitrary reference trajectories inside a reasonably large operation region. The key to this success is the optimal scheme of this paper for linearizing the dynamics of the magnetic object. 
    more » « less
  4. ; ; ; (, 2021 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM))
    null (Ed.)
    Permanent magnet manipulators provide a unique potential for safe operation of magnetically driven medical tools inside the human body for noninvasive surgical, imaging, and drug targeting procedures. These systems manipulate magnetic objects from a distance without direct contact, by generating a magnetic field using strong permanent magnets, and controlling the shape of this field properly. Control over the magnetic field is gained by displacement of the magnets using independent mechanical actuators for each magnet. However, interactions between the magnets result in a coupling between the actuators, which prevents them from independent and precise operation. This paper develops a multivariate, nonlinear feedback control to cancel the magnetic coupling between the actuators in effect. This feedback control incorporates a complex mathematical model of the magnetic interactions between the actuators, which does not admit a simple analytical form. Instead, this model is constructed numerically using the finite element method. The decoupling performance of the proposed feedback control is verified by numerical simulations. 
    more » « less
  5. ; ; ; ; ; ; (, IEEE Robotics and Automation Letters)
    Ani Hsieh (Ed.)
    Reconfigurable modular robots can dynamically assemble/disassemble to accomplish the desired task better. Magnetic modular cubes are scalable modular subunits with embedded permanent magnets in a 3D-printed cubic body and can be wirelessly controlled by an external, uniform, timevarying magnetic field. This paper considers the problem of self-assembling these modules into desired 2D polyomino shapes using such magnetic fields. Although the applied magnetic field is the same for each magnetic modular cube, we use collisions with workspace boundaries to rearrange the cubes. We present a closed-loop control method for self-assembling the magnetic modular cubes into polyomino shapes, using computer vision-based feedback with re-planning. Experimental results demonstrate that the proposed closed-loop control improves the success rate of forming 2D user-specified polyominoes compared to an open-loop baseline. We also demonstrate the validity of the approach over changes in length scales, testing with both 10mm edge length cubes and 2.8mm edge length cubes. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email