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High speed linear actuator required

High speed linear actuator required

High speed linear actuator required

(OP)
Hi all,

I'm basically after a linear actuator on steroids.

Here are the required specs:

0-80mm stroke, 1040N Force, 0-10m/s speed.

I have found a few products that would almost be suitable: http://www.tacrockford.com/product/machine-compone...
But they do no meet the requirements of opening at 10m/s...

Background of use of product:

I work for an electrical switchgear company. We are basically looking at developing some new linear switches, and require a mechanism that can be used to test some new concepts.

I've been searching and contacting companies for the last two weeks have pretty much just gone around in circles.

Do you have any advice on how I can approach this problem?

Thank you in advance.

RE: High speed linear actuator required

Your spec is confusing.
You say 0-10 m/s, then suggest that you need a minimum speed of 10 m/s.
You say 0-80 mm stroke. Do you also mean a minimum of 80 mm stroke?

The context suggests that you do.
I.e., you want to propel some mechanical doohickey by 80mm in 8ms or less.

If it only has to work once, explosives become a possibility.

If repeated operations are a requirement, then you need to look at mechanisms that store energy at some slow rate and release it at a much faster rate.
I think air rifles would be a good place to start.

Mike Halloran
Pembroke Pines, FL, USA

RE: High speed linear actuator required

(OP)
Apologies for the confusing spec - and thank you for bearing with me in trying to suggest a solution.

It will need to be used mulitiple times and is not a once off solution.

10 m/s is the opening speed for an 80mm distance.

If it is a 70 mm distance, the opening speed required is : 8.75 m/s.
If it is 60 mm; opening speed is: 7.5 m/s

Basically it needs to complete the opening motion for a specified travel length varying between 2-80mm, within 8milliseconds.

As the gap reduces - the required opening speed decreases.

In the worst case scenario: it needs to open 80mm in 8 milliseconds .. which means the mechanism needs to travel at 10m/s.


RE: High speed linear actuator required

Except speed 10m/s, you need calculate acceleration/deceleration also. And ones maybe very high also - your speed profile even can't reach such speed! It seems that the only possible solution will be linear motor based actuator.

RE: High speed linear actuator required

Given that this is a switchgear application, is there a reason why the tried and trusted stored energy system using springs and a charging motor can't be employed? As a switchgear end-user, spring tripping mechanisms are simple and have low external demands for the tripping supply - high power motors sound like a headache and a liability.

Sorry if that sounds negative, it isn't intended to be, I'm just trying to understand what your objectives are in this exercise.

RE: High speed linear actuator required

If this is just for testing then have you looked at air or hydraulic cylinders? You'd likely need to create a fixed cylinder travel operating a level with an adjustable motion ratio to allow your varying travel requirements. Either that, or a very rugged adjustable stop.

RE: High speed linear actuator required

hmmmm... ok, buy a linear motor to do it.

you just need 40,000# (140,000N) thrust for the 221,500 in/sec/sec (5,624m/sec/sec) accel & decel rate to make that 8msec trapazoidal move of 80mm. oh, ya, your top speed is 590.5 in/sec (15m/sec).

but good news! at least you won't need hearing protection against a sonic boom - speed of sound is 13,397 in/sec!

RE: High speed linear actuator required

I forgot to list the accel in G: 573.4G

RE: High speed linear actuator required

(fun_on, with physics 101)

Just one last spec: at the peak of the 2msec accel ramp, putting out this force and speed, will take approximately 2,110,000 watts (given a typical linear motor).

that would be 220,000 vac 3ph @ 294 amps assuming the linear motor can handle these values.

(/fun_off)

You won't find a linear motor that can do what you want.

RE: High speed linear actuator required

Since the application is not a single one shot move (no pun intended), maybe you should check out how much energy and speed is in a moving bullet; seriously. a .45 bullet is still under 50 cents each, and I can tell you a plinking target gets rotated real nice and fast when hit. maybe you can just put a 3/8" thick hardened steel 'handle' on the device to move? It could even be fun to shoot at! Mike Halloran is probably leading you down the right path!

RE: High speed linear actuator required

khonfam,

If you're looking for an actuator with this level of Force, Speed and Stroke and you need a range, you might want to take a look at LinMot. They are an excellent servo controlled, linear actuator.

Regards,

Rich.....viking

Richard Nornhold, PE
http://www.energizer.com

RE: High speed linear actuator required

(OP)
Thanks for the suggestion ScottyUK - for the actual device - we plan to use the trusted stored energy system.

Right now while we develop the interrupting device we need to develop a mechanism to do the testing for various configurations. With the stored energy system, there is not much room for varying the mechanisms specifications once it has been made.

Hahaha - "won't need hearing protection against a sonic boom"

- thank you all for the input. Honestly, thank you so much for the suggestions.


I'm glad I put this question up. It definitely helped me clear up that it's not a very simple solution. I put it up, incase I missed something very obvious. I've been looking into servo controlled linear actuators in more detail. I think the concept of rifles/bullets will require too much work to from an OH&S(occupational health and safety) perspective.


I may have to adjust my requirements to see if I can still 'test' the new products we plan to develop.. anyway, I'll hopefully be able to adjust my requirements once I bring this up with the switchgear engineers.

Thanks guys.


Right now this is what I'm leaning more towards: A reciprocating engine with a clutch type mechanism. The motor will be able to be started up and will be spinning the output shaft at the required speeds. As soon as I need it to engage and open the mechanism; It's a matter of 'dumping' the clutch, and hopefully with that the acceleration will be achievable.



RE: High speed linear actuator required

Hydraulics can achieve some pretty rapid movements, especially if you use oil one direction and a spring in the other. When the spring moves the actuator the speed is largely governed by how fast oil can be vented, and that can be pretty quick. Anecdotally, governor valves on a turbine typically use this sort of system: when the hydraulic oil is dumped in a trip situation the valves close very rapidly considering their size. That's from a system designed principally for precision control rather than pure speed - I'm sure it could be optimised for the latter.

There are some very knowledgeable guys in forum1083: Fluid Power engineering who could tell you more than I can about where the limits are.

RE: High speed linear actuator required

As an EE I admit I don't recall the name of it, but you might also consider the old railroad wheel drive mechanism - a wheel with a slot in it that moves a linear rod.... If I did the math correctly, a 10" dia wheel with a slot in it or hole to attach the rod to, rotating at 7,500rpm could make that 80mm move in 8msec also. Not sure how you would make it live long but maybe that is not an issue to a good ME designer for the short time you need to run each test?

A free motion sizing program such as Motioneering by Kollmorgen can help you try different types of actuators such as linear motors, rotating wheels, etc:

http://www.kollmorgen.com/en-us/service-and-suppor...

RE: High speed linear actuator required

Some hydraulic systems use compounding for a fast return. When a retracted cylinder is to be extended rapidly, pressure is applied to both ports. The effective cylinder area becomes the area of the rod, rather than the area of cylinder. The travel speed is increased by the ratio of the cylinder area to the rod area.
If you are considering clutches, look at the flywheels and air operated clutches used to drive alligator shears such as are used to cut re-bar. If you go that route, look for a high slip motor to drive it.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: High speed linear actuator required

(OP)
Thanks again for your response.

I will look into the Motioneering Program today.

In regards to designing the hydraulic system... I really don't want to have to go into the specifics too much myself. Ideally I would like a company with the experience in making them to specify what I need for my requirements.

For Example, it's like buying a car: I want a car that does 0-60mph in under 6 seconds. I am not going to learn everything about forced induction or v8's (etc)... I just want a manufacturer to tell me; "here, our VW Golf R meets your requirements, it uses a turbo charger on 2.0L motor".

Does that sort of make sense? I want to have a general idea of how the mechanics work... but not in the full detail that would require me to design the entire mechanism myself.




RE: High speed linear actuator required

How many millions will you be needing?

Mike Halloran
Pembroke Pines, FL, USA

RE: High speed linear actuator required

(OP)
You mean quantity or are you referring to money? Haha.

RE: High speed linear actuator required

Either way.

Mike Halloran
Pembroke Pines, FL, USA

RE: High speed linear actuator required

(OP)
I don't know why I didn't think of this earlier. The solution was staring me in the face....


I can get a high speed electric cylinder/cylcindrical linear motor... (http://www.tacrockford.com/product/machine-compone...)
couple this with a effective lever type mechanism, and get the required opening speeds!

So if this thing can open at a maximum of 1 m/s... then I couple it with a lever that moves 10 times the distance for every 1m this mechanism moves(http://images.tutorvista.com/cms/images/38/lever.P...)... and then Boom! I have a device opening at 10m/s!
Only issue is the applied force, but my force requirements are quite low in comparison to what can be outputted in these devices!

RE: High speed linear actuator required

Uh, yeah.

Before you get all lathered up about electromechanical stuff, review the kinetics that Mike Kilroy outlined above.

Don't forget the time that it will take to build current and force against the inductance of the forcing device. You probably lose at least a millisecond there, but you need to work it out for yourself.

Or rent a systems guy.

Mike Halloran
Pembroke Pines, FL, USA

RE: High speed linear actuator required

Consider the very common use of energy stored in a mass. It's extremely calculable because it follows simple kinematic equations. The standard in metal strength testing is a simple pendulum weight. You can precisely set the speed and force available by simply changing the height the pendulum is "cocked to".

The same technique is used for glass testing. A large weight lifted on a cable. The weight is dropped from an exact height and swings down in an arc to hit the glass. The weight, cable length, and height completely specifies the speed and energy at impact. You could do the same having the hammer strike a rod to impart your linear motion.

Keith Cress
kcress - http://www.flaminsystems.com

RE: High speed linear actuator required

Having never built a switchgear tester, I have no idea the requirements other what has been stated here.

Having said that, I HAVE turned off breakers and switches, and it never seemed to me I had to do it in 8 msec.

So, is it possible this may NOT be a requirement after all? Please tell us why this is required for the test; mind you, I am not saying is not required, but it is hard to understand why it would be important.

Keith's idea of hitting a nail with a hammer device sounds intriguing too.... reminds me of the hydraulic lifters in a car pushing valve up and down (sure it is on nice smooth cam but maybe something in the idea would help too..)

RE: High speed linear actuator required

Mike,

There's a world of difference between the speed you operate the handle and the speed at which the internal mechanism actually travels. Most breakers use stored energy in springs to provide the high speed operation, as distinct from 'dependent manual operation' types in which the contact movement is governed by the skill of the user. DMO switches have a long history of disruptive failures, often resulting in an arcing fault. DMO gear is virtually extinct these days, and that is a wholly positive step.

RE: High speed linear actuator required

Scotty, thanks for the info. Guess then what I don't understand is why anyone would need to test the stored energy motion part separate from the spring-energy-release part. 'Course I don't mfgr these devices so am pretty dumb on them. But what is wrong with using the scheme that does the internal flip? Obviously there is a reason, I am just really curious what it is. What exactly is being tested?

RE: High speed linear actuator required

(OP)
Scotty, thanks for explaining to Mike the difference between the operators speed and the actual mechanisms speed.

Mike - The critical component of most switchgear is the interrupting device. Some switchgear manufacturers just buy this part off the shelf. I need to test these different off the shelf solutions, and I need a device that can accommodate for varying lengths and open and close the switch to it's required specifications.

I think the simplest way to explain it is by using an analogy of a car. Right now, I want to test a 4 cylinder, a v6 and a v8 engine. I haven't decided what's best for my car yet. I need a chassis that can accommodate for all of these. Once, I have actually chosen my engine... then i will design the specific body for it.


" why anyone would need to test the stored energy motion part separate from the spring-energy-release part." ... Most of these mechanisms are very specific, and work for one specific case. Currently I need to evaluate a whole series of devices. This is a little CAD file I made earlier to show the internals of the switch.



8.333m/s - This is the time it takes for 1/2 a 60hz cycle.

RE: High speed linear actuator required

(OP)
I need to be able to open and close the switch in 1/2 a 60hz cycle (8.333m/s). If the contact seperation distance is 80 mm.. this means 10 m/s average speed + Some ridiculous acceleration/deceleration....

RE: High speed linear actuator required

Close that fast may not be possible. Opening that fast happens when "blow open" contacts are used. The blow open contact uses the magnetic forces of high current fault to blow the contacts open before anything else even begins to operate. Anything other than magnetic response to high fault currents is likely to take longer than a half cycle.

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