Electromagnetic Actuator

Often called a linear motor or voice/speaker coil, the electromagnetic actuator is versatile and relatively easy to design/build.

Step 1: Design the actuator you have always wanted.

There are two ways to do this: you may either go through the attached voiceCoilEquations.pdf, find all my mistakes, and develop your own magnetic circuit model, OR you can download the attached solidworks files and excel spreadsheet and just use the parametric model I have built.

Step 2: Enter the specifications

Solidworks comes with with this handy feature called a design table. It is an excel spread sheet which can, and in this case does, contain a bunch of equations that drive the design. So, open the spreadsheet - either in excel or in solidworks - and in the yellow hightlighed area, enter in the pertinent parameters: desired force, throw, lateral clearance, and magnet strength/geometry.

You will have to manipulate the gap height parameter to find the gap height that gives the best flux density (least power) while not exceeding whatever spatial limitations you might have. As you play with this, you will not that the equations break if you choose this parameter unusually low or high.

Step 3: Machine the stator and bobbin

After tweaking the design in solidworks, output some drawings and take them to the machine shop.

A couple of tips on this step. Machining a deep pocket in Iron (or soft steel) for the stator is a pain. As a alternative, you may machine a cylinder and a disc. Place the cylinder on a hot plate and the disc in ice water. After the cylinder is at 500 oF and the disc at 30 oF, slam them together using an arbor press (exciting). The bobbin should be made out of aluminum or plastic. Be careful while assembling the magnet and flux puck into the stator cup. It is recommended to machine a guide for the magnet and puck so as to avoid losing digits.

Step 4: Wind bobbin

Scrolling to the bottom of the design table spreadsheet will reveal a number of wire guage choices. Hopefully, one of these will work with your amplifier.

Wind the magnet wire onto the bobbin. With either a lathe or a bobbin winding machine. Try to keep relatively constant tension on the wire as you wind the coil.

Wrap electrical tape around the finished windings or pot in epoxy.

Comments

[mac.rodge]

Hi!
Nice work.
I want to design a actuator to lift 160 Kg load, with stroke of 20 cm.
Can it be possible with your method?

[mac.rodge]

Hi!
Nice work.
I want to design a actuator to lift 160 Kg load. Can it be possible with your method?

[Gambiarra Inc.]

Does this equations works with a 2cm or 3cm stroke?
I talked to my Professor about design and construction of these kind of actuators, and he said that it's not a trivial thing to do. Also, it's hard to achieve linearity and a long stroke.
And would you tell us where did you get the references?

Thank you!
And congratulations, it looks great!

[balle75]

Great article!

Is it important that the stator is in iron/steel? As far as I know theonly place where iron is important i for the flux puck, where you wantto concentrate and magnify the magnetic field.

What is the "throw"? The expected variation of the radialbobbin clearance?

[corwin]

Thank you.

The throw is the displacement of the actuator - the range of the actuator in the direction of actuation. There is a term in the excel file for radial clearance.

[gateon]

if memory serves me right, an electromagnetic actuator in simple terms turns electrical energy into linear motion

[imshanedulong]

You know, it kind of annoys me when people put mouseover note INSIDE mouseover notes. You can never read them!

[cotton]

 SAME!

[kikiclint]

Thank you for the instructable. Some tips.  The introduction needs to be a little clearer, since I am still not sure what this is used for.  Only that it is versatile.  Some kind of demonstration after it is finished would be great too.  This would help to see what it is or does.  You give lots of technical details, but not the kind of details which will help someone understand why you did it the way you did.  I would love to see a revised version.

[sneakyshitnl]

i think they use this thing for radars on ships.

[balle75]

What does it do? In my terms:

Actuator: An actuator moves other objects, see: http://en.wikipedia.org/wiki/Actuator

Stewart platform: A platform that can be controlled to move an objectthat is attached to it inn all directions: http://en.wikipedia.org/wiki/Stewart_platform

Vibration isolator: A mechanism that stops vibrations from beingtransfered to an object. For the stewart platform the ground can bevibrating, but the thing attached to it can be free of vibrations. http://en.wikipedia.org/wiki/Vibration_isolation

[_soapy_]

Where is step 5? Surely you want to say that you now put the two halves together, and wire the rest of the circuit up to control things? Anyway, the magnet containing half is pulled and pushed by the magnetic field generated by current flowing through the wire coil on the other half. If you short the two ends of the wire together, you will also have a stiff shock absorber, and with them apart you will have a floppy piston. A diode could be used to have a stiff shock absorber that relaxes back to position almost instantly.

[strangebike]

so this would work for a car then ? coz to me it sounds like the perfect suspension damper.?

[corwin]

Some companies have considered voice coil dampers for vehicle suspensions, but they are not well suited because of their lack of low-frequency stiffness. Typically, active damping systems in vehicles are done with a variable orifice in a hydraulic system.

[strangebike]

seems a shame as you could use them to add power back in to the drive system. I'm sure with the right filter setup the low frequency stiffness could be improved.

[oxidase]

could someone explain to me what this thing does ?
thanks ^_

[armageddon]

what the hell is this and what does it do? and can you tell us in simple terms please?

[NetReaper]

just back away

[InsaneSam373]

i like it it was funny on step 5 when he was like put no bacon or any type of food on it:) great instructable!!! VERY CLEAR

[thermoelectric]

Step 5?

[vitruvian8807]

Uhmm, are these all the steps?

[corwin]

more or less - what is confusing?

[vitruvian8807]

hmm, wow, I thought I knew enough about electronics and stuff, but I really don't know much by looking at this. I have some idea of what it does, but not enough knowledge to build it. I may be Bright, but not a Genius.

[thunderw]

where is the diagram and what software do you use to view it

[corwin]

The diagram is the sldasm file - view it in solidworks.

[ven]

Is the magnet magnetized diametrically or axially? also, do the north and south pole positions matter? Thanks

[corwin]

Magnetization is axial. North and south pole positions do not matter unless you only want to go in one direction.

[ven]

Have seen a design with magnets magnetized radially, south pole facing outside
http://www.beikimco.com/appguides/BEIKimco-VCA-AppGuide2002.pdf#VoiceCoilActuators.

Your axially magnetized magnet (north and south poles through thickness) are easy to purchase, while radially magnetized seem impossible to find. Maybe they are special made.

Are there other advantages in one design over the other?

[Punkguyta]

Would it be possible to wind the core with a finer gauge of wire to add a bit more strength/accuracy?

[corwin]

Accuracy is independent of wire guage (to reasonable limits). The force that the actuator is able to create is also largely independent of wire guage. The force is dictacted by the size/strength of the magnet and the geometry of the gap. The wire guage controls the relationship between voltage and current - e.g. a larger guage wire will operate at a lower voltage but will require a higher current. Hence, choose your wire guage based on what your drive electronics are happy to supply.

[Punkguyta]

Ok, makes sense. So have had any succesful experiments with this with either salt or water?

[stonehenge360]

im probabily going to sound like an idiot, but what exactly does this do?