# Servo/Proportional Pneumatics



## Hippie Crane (Sep 17, 2019)

Hello,

Has anyone here had any experience with Servo-Pneumatics or Servo-Hydraulics? If so I would like to know how it played out for anyone who has tried it.

It involves using an LVDT or linear hybrid potentiometer to measure the postition of the actuator, while an error detector card compares the target and feedback value to control a servo-valve which brings the actuator to the desired position.

I have achieved extremely smooth pneumatic position control but I am having issues with it lifting weight.

Does anyone have any knowledge of this?
I need to use proportional pneumatics or hydraulics (or large servos if I hit a dead end) to build a 5ft tall animatronic crane that plays guitar.


-Canaan


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## Hippie Crane (Sep 17, 2019)

I would also like to mention the reason why I need to use air or oil for the movements. There are several large movements in the character.

2 of those movements include a boom arm that moves his body up, down, left, and right to give the allusion that he is slightly crouched and bopping around while he is playing the guitar.


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## Hippie Crane (Sep 17, 2019)




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## Hippie Crane (Sep 17, 2019)

*example*


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## DarkOne (Oct 16, 2012)

Since you've figured out motion control, is the issue of lifting the weight that your cylinder is too small?


Just because I'm curious and want to use this type of control as well, are you using double acting valves and some type of PID controller? An arduino maybe, or something commercial?


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## Hippie Crane (Sep 17, 2019)

*reply*



DarkOne said:


> Since you've figured out motion control, is the issue of lifting the weight that your cylinder is too small?
> 
> Just because I'm curious and want to use this type of control as well, are you using double acting valves and some type of PID controller? An arduino maybe, or something commercial?


I am using specifically a mac 45a 4-way poppet valve that switches at very low flow rates at 24vDC. The test was running on 100PSI and I had a secondary valve which is an enfield technologies PFV electronic flow control valve I was using to control the speed of the air cylinder. the position feedback was a simple 10k rotary pot and I used an arduino to write the PID control loop. I think I might need to try to use a fully proportional valve. Currently I use a directional control valve and an additional 2 way proportional valve. I think maybe if I use 2 of those proportional valves to meter out I could have a result with better control.


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## Hippie Crane (Sep 17, 2019)

DarkOne said:


> Since you've figured out motion control, is the issue of lifting the weight that your cylinder is too small?
> 
> Just because I'm curious and want to use this type of control as well, are you using double acting valves and some type of PID controller? An arduino maybe, or something commercial?


Also, the program storage is a 8 channel surround sound audio player that has several instrument and vocal tracks and a data track that contains 9600 baud Biphase Mark Code (BMC) tape data. its basically serial with a combined clock so I dont need a computer to play back shows. The serial data is stored in the audio and decoded by the arduino.


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## Hippie Crane (Sep 17, 2019)




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## DarkOne (Oct 16, 2012)

What is the bore of your cylinder?


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## Hippie Crane (Sep 17, 2019)

DarkOne said:


> What is the bore of your cylinder?


for the pneumatic cylinder its 2".

I'm going to make a switch to servo-Hydraulics though so the cylinders wont need a bore of more than 1".


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## Hippie Crane (Sep 17, 2019)

Here is a test I made.


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## Batbuddy (Sep 3, 2014)

My only concern with going to Hydraulic is oil leakage. I have worked with hydraulic machinery a bunch and there is an inevitable leakage of oil, which is messy and might be an issue. Just something to consider... Leaking air is not so messy.


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## Greg G (Nov 4, 2012)

Wow, that pneumatic position control looks pretty smooth. I've wanted something like that to give me better control of the back up/down motion of my prop, although those enfield technologies PFV electronic flow control valves aren't cheap even on e-bay (I haven't looked for other brands though).

Greg


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## Hippie Crane (Sep 17, 2019)

Greg G said:


> Wow, that pneumatic position control looks pretty smooth. I've wanted something like that to give me better control of the back up/down motion of my prop, although those enfield technologies PFV electronic flow control valves aren't cheap even on e-bay (I haven't looked for other brands though).
> 
> Greg


you can use those RC hydraulic valves with the little rc servo on them. they are proportional but may leak air slightly because the seal is just metal on metal. but that is ok because most proportional valve have slight air leak.


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