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hag
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Join Date: Dec 2006
Posts: 6

Speed Control of A Pneumatic Rotary Actuator

01/12/2007 3:22 AM

Hi,

A single acting (spring retract) rotary vane actuator(pneumatic) is connected to a 3/2 solenoid valve. An exhaust reducer is attached at the exhaust port of this solenoid valve.

1. During the forward stroke, the air pressure is constant throughout. So, is there any way of controlling the speed of the actuator? (The required torque reduces sinosoidally with angle, the actuator supplied torque reduces linearly)

2. During the backward stroke (retraction), the speed will be controlled (set to almost 0) using the exhaust reducer. Will I need to ensure that the back pressure on the actuator does not increase beyond the suppliers max pressure rating? or is it that the back pressure can simply not rise beyond the suppliers max pressure rating, coz at the end of forward stroke (ie: beginning of retraction) the pressure has to be less than the supplier rating?

Thanks,

hag
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ducon
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#1

Re: Speed Control of A Pneumatic Rotary Actuator

01/12/2007 9:22 AM

Better ask the Manufacturer

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NoSciFi
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#2

Re: Speed Control of A Pneumatic Rotary Actuator

01/12/2007 11:20 PM

Are you maybe looking for a constant speed on the forward stroke?

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hag
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Join Date: Dec 2006
Posts: 6
#3
In reply to #2

Re: Speed Control of A Pneumatic Rotary Actuator

01/12/2007 11:58 PM

i want to ensure that the stopping of the actuator at the end of the forward stroke is smooth with no impact or vibrations.
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jstolaruk
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Location: SE MI USA
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#4
In reply to #3

Re: Speed Control of A Pneumatic Rotary Actuator

01/13/2007 8:39 AM

There is nothing smooth about fluid power with air. But if thats your only choice, I would use a adjustable cushioned stop and overdrive the actuator.
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Anonymous Poster
#7
In reply to #4

Re: Speed Control of A Pneumatic Rotary Actuator

01/14/2007 11:38 AM

Is a cushioned stop possible for Rotary Actuator?
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jstolaruk
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#8
In reply to #7

Re: Speed Control of A Pneumatic Rotary Actuator

01/14/2007 1:26 PM

The typical rotary actuator is a cylinder connected to a rack that drives a gear on the rotating axis. The cushions can be internal (factory option) or on the rod if a portion of it is outside the cylinder body.
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NoSciFi
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#5
In reply to #3

Re: Speed Control of A Pneumatic Rotary Actuator

01/13/2007 8:39 AM

A spring is probably your best bet. Aim for about 60% compression at the force the actuator is capable of.

RichH

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dkwarner
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#6
In reply to #3

Re: Speed Control of A Pneumatic Rotary Actuator

01/13/2007 11:45 AM

If cost and complication isn't a problem (NOT KISS) (its an expensive device that MUST stop gently), then add an angular position sensor controlling a pneumatic A-B switch to change to a lower pressure for the last part of travel. Add a pneumatic or hydraulic dash-pot at the end of travel.

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Billy@Delta
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#9

Re: Speed Control of A Pneumatic Rotary Actuator

01/16/2007 12:52 AM

Since air is an easly compressed media,

This causes it to be irregulare keep the exhaust control closest to the cylinder.

Festo has exhaust regulators witch you place directly on the cylinder, giving you the best controll possible.

If slow speeds are needed over dimension the cylinder (more air you can controll, the better controll you have)!

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bhrescobar
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#10
In reply to #9

Re: Speed Control of A Pneumatic Rotary Actuator

02/01/2007 8:36 AM

I think this last one is your best choice, control the actuator speed by controlling the air flow in the exhaust of the unloaded side. Add a directional valve in parallel in the opposite direction, and you'll have controlled speed in forward direction, and free movement in the retract.

Some actuators and cylinders also have a restrictor that reduces the airflow in the end of their travels. Are you sure you are not able to use one of them?

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