Project Readiness Package Rev 10 June 2010

Project Summary

A number of optical and mechanical assemblies used in aerospace applications require mounting on steerable gimbals or vibration and shock isolation mounting systems. Rapidly damping out mechanical oscillations due to rapid motion or vibration is essential to enable accurate pointing of an optical system or prevent noise in data due to oscillations. This project calls for design and demonstration of a prototype magnetic eddy-current damping assembly usable for aerospace systems. Deliverables include a mathematical model describing system damping behavior and prototype hardware validating the model.

Administrative Information:

Project Name: Magnetic Damper
Project Number: P11566
Project Track: n/a
Project Family: n/a
Parent Roadmap: n/a
Planning Term: Fall 2010
Start Term: Winter 2010
End Term: Spring 2011 / Faculty: Alan Raisanen (RIT)
Industry Guide: P. Vallone (ITT)
Project Customer: ITT
Project Sponsor: ITT
Project Budget: TBD

Project Context:

This project will involve design and construction of a prototype magnetic damping system for moving parts in aerospace applications. Cameras and other optical systems are mounted on pointing systems such as gimbals to allow tracking of objects, or rapid switching between objects. Quickly moving massive camera platforms will often cause the platform to oscillate when it reaches the intended position, and no useful data can be collected until the oscillations damp out and the platform orientation becomes stable. Similarly, shock- and vibration-sensitive items are often mounted on springs to prevent damage, but it is desirable that oscillations of these items are rapidly damped out to prevent noise from interfering with measurements. Conventional damping systems such as hydraulic shock absorbers have the disadvantage of oil leakage near sensitive optical components, change in performance at temperature extremes, and are not well suited for space applications. A solid-state dampener which is not sensitive to temperature variations is ideal.

Magnetic damping systems make use of the physical principle that moving a conductor through a strong magnetic field will induce an eddy current in the conductor. This eddy current establishes its own magnetic field, which opposes the motion of the first magnetic field, thus damping the relative motion of the conductor and the magnet. Essentially, the magnetic field moving through the conductor generates an electric current which is dissipated as heat, robbing the conductor of some kinetic energy. This appears as a damping force impeding the motion of the conductor. The damping force is larger as the relative velocity increases according to the formula F=Kv, where v is the relative velocity and K is the damping coefficient determined by device geometry, resistance of the conductive material, and magnetic field strength. All components are solid-state, eliminating concerns about oil leakage in space or on sensitive optical surfaces, and are relatively insensitive to temperature variations. As an example of this type of system, a simulation is shown of a conductive rotating disk mounted between a set of magnetic poles. COMSOL Multiphysics finite-element analysis software is used to calculate the magnetic field, eddy current distribution, and velocity change with time of the disk as it rotates through the magnetic field with some initial angular velocity w. The magnetic field strength is shown in color superimposed on the disk at time zero, illustrating how the induced eddy currents distort the initially uniform magnetic field between the pole pieces. The inset at top left shows the evolution of the angular velocity of the disk (w) as a function of time, illustrating the magnetic braking force applied to the disk. A device capable of providing similar motion damping in a linear mode is desired for this project. Candidate designs and simulations for a linear shock-absorber type of device capable of damping out 300-lb loads will need to be developed, and hardware will be constructed to verify the simulation behavior.

Customer Needs Assessment and Engineering Specifications:

Project Interfaces:

This project is a stand-alone task specific to ITT. The magnetic damper device may be used to suppress vibration and overshoot in a fast mirror pointing system, as part of another proposed ITT project, “ITT Mirror Steering System”.

Staffing Requirements:

Use this section to describe the number and type of engineering students needed to complete this project. You should justify the people you need (who), why you need them, what they will do, when, how, and where they will do it.

Position Title / Position Description
Lead Engineer (ME/IE) / The Lead Engineer is a mechanical or industrial engineer responsible for maintaining project schedule, coordinating project tasks, and systems integration.
The lead engineer should have strong leadership ability and communications skills. The lead engineer will be responsible for establishing realistic compromise device architecture and engineering parameters to meet desired performance objectives using commercially available components such as permanent magnets. Basic familiarity with electromagnetism, finite element analysis/MATLAB, and vibration analysis is highly desirable. The lead engineer should have taken the DPM course.
Simulation Engineer (ME) / The simulation engineer will be a mechanical engineer responsible for finite element analysis and MATLAB modeling of the magnetic damping system. Using commercially available components such as rare-earth magnets, the design engineer will model candidate system architectures to predict damping performance, and then optimize these architectures for maximum damping behavior.
Extensive familiarity with MATLAB and a finite element modeling package such as ANSYS or COMSOL is a must. Basic knowledge of electromagnetic field physics is highly desirable.
Fabrication Engineer (ME) / The fabrication engineer will be a mechanical engineer responsible for physical implementation of the magnetic damper device.
Knowledge of mechanical metal fabrication techniques such as machine shop operations and welding is required.
Test Engineer (ME/IE) / The test engineer will be a mechanical or industrial engineer responsible for design and fabrication of a test bed to demonstrate the damping behavior of the candidate magnetic damping device. A mass of approximately 300-lb will be suspended on springs, and the damping behavior of the damper system will be measured for single impulse deflections and vibrations with various amplitude and frequency.
Knowledge of mechanics, metal fabrication techniques, use of data acquisition systems, and data analysis with MATLAB or Excel will be required.

Project Constraints:

System must function with commercially available permanent magnets and commonly-available aerospace materials. Use of superconductors, cryogenic magnets, and other ultra-high performance components will not be practical.

Required Faculty / Environment / Equipment:

Describe resources necessary to support successful Development, Implementation and Utilization of the project. This would include specific faculty expertise for consulting, required laboratory space and equipment, outside services, customer facilities, etc. Indicate if required resources are available.

Category / Source / Description / Resource Available (mark with X)
Faculty / Dr. Alan Raisanen / Finite element analysis and physics advice / X
Dr. Hany Ghoneim / Finite element analysis and vibration analysis / X
Environment / Test area / Assembly and operation of heavy test fixture / X
Equipment / Machine Shop / Fabrication / Welding of magnetic damper and test fixture / X
FEA software / Simulation software (ANSYS, COMSOL, MATLAB, etc) / X
Materials / magnets / High strength rare earth magnets / Purchase
metal / Copper, aluminum, etc for structural materials of damper and test fixture / Purchase
Other / Data acquisition / Simple velocity/position data acquisition components / X (borrow)

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