# about select hydralic value? **URL:** \ **Category:** RMCTools\ **Created:** [January 4, 2014, 5:13am UTC](https://forum.deltamotion.com/t/about-select-hydralic-value/241 "2014-01-04T05:13:34Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![mars\_bruce\_lee](https://forum.deltamotion.com/letter_avatar_proxy/v4/letter/m/a587f6/32.png) [@mars\_bruce\_lee](https://forum.deltamotion.com/u/mars_bruce_lee)\ **Post date:** [January 4, 2014, 5:13am UTC](https://forum.deltamotion.com/t/about-select-hydralic-value/241/1 "2014-01-04T05:13:34Z")
System Requirements： the velocity=1000mm/s the accelrate=decel rate=2000mm/s2 Question： How much ms of the value response at least. Current I consider like this : the value response must be the 10 times of machine and the electrical response must be 10 times of hydralic vale respones Is it right? ---
**Author:** ![Jacob\_Paso](https://forum.deltamotion.com/letter_avatar_proxy/v4/letter/j/439d5e/32.png) [@Jacob\_Paso](https://forum.deltamotion.com/u/Jacob_Paso)\ **Post date:** [January 6, 2014, 10:28pm UTC](https://forum.deltamotion.com/t/about-select-hydralic-value/241/2 "2014-01-06T22:28:50Z")
That is approximately right. However, it also depends on how well position must be controlled when an external force disturbs the system. ---
**Author:** ![mars\_bruce\_lee](https://forum.deltamotion.com/letter_avatar_proxy/v4/letter/m/a587f6/32.png) [@mars\_bruce\_lee](https://forum.deltamotion.com/u/mars_bruce_lee)\ **Post date:** [January 7, 2014, 2:03am UTC](https://forum.deltamotion.com/t/about-select-hydralic-value/241/3 "2014-01-07T02:03:51Z")
> [@Jacob Paso](#): > > That is approximately right. However, it also depends on how well position must be controlled when an external force disturbs the system. About “it also depends on how well position must be controlled when an external force disturbs the system” About other question What about the Positioning precision with？ it’s only Depends on encoder Resolution？ encoder Resolution is 10 times asked precision？ that’s ok? ---
**Author:** ![Jacob\_Paso](https://forum.deltamotion.com/letter_avatar_proxy/v4/letter/j/439d5e/32.png) [@Jacob\_Paso](https://forum.deltamotion.com/u/Jacob_Paso)\ **Post date:** [January 7, 2014, 6:56pm UTC](https://forum.deltamotion.com/t/about-select-hydralic-value/241/4 "2014-01-07T18:56:37Z")
Positioning resolution depends on the position sensor, the actuator, and the mechanical system. For the sensor, ten times the required resolution is probable a good choice. High resolution is also useful for poor systems that need advanced control. For example, if the valve is far from the cylinder, the system will tend to oscillate and it may be necessary to heavily use differential and double differential gain. High feedback resolution is very important in order to use those gains. ---
**Author:** ![mars\_bruce\_lee](https://forum.deltamotion.com/letter_avatar_proxy/v4/letter/m/a587f6/32.png) [@mars\_bruce\_lee](https://forum.deltamotion.com/u/mars_bruce_lee)\ **Post date:** [January 16, 2014, 3:29am UTC](https://forum.deltamotion.com/t/about-select-hydralic-value/241/5 "2014-01-16T03:29:48Z")
thank you for reply。 Several other questions： 1:In our project, many values ,Δp = valve pressure differential in bar=130bar, some people think is too big, the best should be 80 or less。 Is it ok? 2: about Frequency response characteristic curves, there are three Signals including 5%,25%,100%. which signal should i refer? How to link with other parameters(velocity,accelrate,decel rate Etc.) Give me a example ,thanks a lot. ---
**Author:** ![Peter\_Nachtwey](https://forum.deltamotion.com/letter_avatar_proxy/v4/letter/p/f17d59/32.png) [@Peter\_Nachtwey](https://forum.deltamotion.com/u/Peter_Nachtwey)\ **Post date:** [January 22, 2014, 9:06pm UTC](https://forum.deltamotion.com/t/about-select-hydralic-value/241/6 "2014-01-22T21:06:38Z")
> [@mars\_bruce\_lee](#): > > 1:In our project, many values ,Δp = valve pressure differential in bar=130bar, some people think is too big, the best should be 80 or less。 Is it ok? That isn’t big when the valve is closed. When the valve is closed the pressure difference across the valve is equal to the system pressure and 130bar is not a very high system pressure. Perhaps you can clarify why there is concern about the 130bar pressure difference. > [@](#): > > 2: about Frequency response characteristic curves, there are three Signals including 5%,25%,100%. > which signal should i refer? > > Give me a example ,thanks a lot. Use the 100% or 90% rating. You don’t buy a big valve just to use only 5% of it. In your example above you stated you want to move at 1m/s. I am assuming that would require the valve to be open about 90% of the way. You do want 10% margin for cases when the oil is cold or the load is a little higher. > [@](#): > > How to link with other parameters(velocity,accelrate,decel rate Etc.) Wow, this is a big topic but I use some rules of thumb to do quick calculations when a customer calls. Usually the customer wants to move a specified distance in a specified time. I use these 2 equations to calculate the required speed and acceleration v=1.5_Δx/Δt and a=4.5_x/Δt² the velocity, v, is the maximum velocity assuming 1/3 of the time is spent accelerating, 1/3 of the time is spend at constant velocity and 1/3 of the time is spent decelerating. The ‘a’ is the average acceleration. If you use linear ramps ( not recommended ) then the acceleration is constant but if you use s-curves then the peak acceleration is 1.5 times the average acceleration on the RMC75 and RMC150. This means the peek acceleration is a=1.5_4.5_x/Δt² There are more rules for sinusoidal motion. I have a wxMaxima work sheet that estimates the speed and acceleration of a hydraulic actuator here [deltamotion.com/peter/Maxima/VCCM%20difeq.html](http://deltamotion.com/peter/Maxima/VCCM%20difeq.html) After doing these calculations you must check if the desired motion profile will fit below the motion profile that the actuator can do. ---
**Author:** ![mars\_bruce\_lee](https://forum.deltamotion.com/letter_avatar_proxy/v4/letter/m/a587f6/32.png) [@mars\_bruce\_lee](https://forum.deltamotion.com/u/mars_bruce_lee)\ **Post date:** [January 27, 2014, 4:43pm UTC](https://forum.deltamotion.com/t/about-select-hydralic-value/241/7 "2014-01-27T16:43:35Z")
thanks peter for your reply。 mars\_bruce\_lee wrote: 1:In our project, many values ,Δp = valve pressure differential in bar=130bar, some people think is too big, the best should be 80 or less。 Is it ok? That isn’t big when the valve is closed. When the valve is closed the pressure difference across the valve is equal to the system pressure and 130bar is not a very high system pressure. Perhaps you can clarify why there is concern about the 130bar pressure difference. In my project，when the value open 50%，there is Still a 130bar Δp。Rexroth engineers tell me is Little big。 Is right？ should i reduce the Δp？ ---
**Author:** ![mars\_bruce\_lee](https://forum.deltamotion.com/letter_avatar_proxy/v4/letter/m/a587f6/32.png) [@mars\_bruce\_lee](https://forum.deltamotion.com/u/mars_bruce_lee)\ **Post date:** [January 27, 2014, 4:55pm UTC](https://forum.deltamotion.com/t/about-select-hydralic-value/241/8 "2014-01-27T16:55:10Z")
In your article refers“A safe rule of thumb to follow is to take the rise time from0 to 100% andmultiply it by 4, then divide this time into 1 to get the frequency for full travel.” that Conflicts“Use the 100% or 90% rating. You don’t buy a big valve just to use only 5% of it. In your example above you stated you want to move at 1m/s. I am assuming that would require the valve to be open about 90% of the way. You do want 10% margin for cases when the oil is cold or the load is a little higher.”