Go Down

Topic: Position control (Read 2 times) previous topic - next topic

zoomkat

Quote
This is a stand alone hydraulic unit with built in resivoir and pump.....max speed of unit is 3.1" a second and it has a hiqh force that will be adequate for what I am doing. This actuator will work but it is just a dc motor driving it! I need some sort of position control for my application.


You could attach a linear pot to the moving shaft, or simply use foward and reverse travel limit switches.
Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

John_S

Quote
I am curious if I can get accurate position control probably within the .0325"
I doubt you could get that sort of positional accuracy. Hydraulics tend to be for brute force rather than pinpoint precision. having a system that's capable of such precision would require the right pump and valves rather than any electronic position sensor.

retrolefty


Quote
I am curious if I can get accurate position control probably within the .0325"
I doubt you could get that sort of positional accuracy. Hydraulics tend to be for brute force rather than pinpoint precision. having a system that's capable of such precision would require the right pump and valves rather than any electronic position sensor.


I strongly disagree. I worked at a oil refinery and we used many different forms of hydraulic actuators for things like throttle control on large steam driven turbines and other large mechanical equipment. Such control required very high precision positioning and a well designed system could have both large brute force strength combined with pinpoint precision. Typical position feedback sensors used were LVDT sensors ( http://www.ni.com/cms/images/devzone/tut/a/f841fe69729.gif ) mechanically coupled to the moving actuator arm or shaft. Electronic P&ID controllers were used to sense the actual position Vs desired position (setpoint) and drive the electro-hydraulic control in a classic feedback loop. The various electro-hydraulic components were very expensive made to very tight tolerances, there was no slop and minuet movements as well as fast movements could easily be made.

Lefty

Robparsons86


Quote
This is a stand alone hydraulic unit with built in resivoir and pump.....max speed of unit is 3.1" a second and it has a hiqh force that will be adequate for what I am doing. This actuator will work but it is just a dc motor driving it! I need some sort of position control for my application.


You could attach a linear pot to the moving shaft, or simply use foward and reverse travel limit switches.


If I use a pot as a feedback device then use another pot as an input device to change the position? For every change of voltage the shaft will move a certain distance? Would that work?

retrolefty



Quote
This is a stand alone hydraulic unit with built in resivoir and pump.....max speed of unit is 3.1" a second and it has a hiqh force that will be adequate for what I am doing. This actuator will work but it is just a dc motor driving it! I need some sort of position control for my application.


You could attach a linear pot to the moving shaft, or simply use foward and reverse travel limit switches.


If I use a pot as a feedback device then use another pot as an input device to change the position? For every change of voltage the shaft will move a certain distance? Would that work?


In theory, yes. I reality it depends on the quality, resolution, environmental ruggedness of the pot as well as how well and backlash free your mechanical connection to the pot is. The only time I saw pots used in commercial actuator applications is where it was built inside the actuator body itself.

Lefty

Go Up