Hydraulic Control Advances

Jasonc24

Member
Join Date
Jun 2005
Posts
11
Greetings everyone... I am new to this group (third time to the site), but it looks pretty good thus far; there is a lot of good information.

I am writing an article regarding advances in hydraulic technology that allow machine designers to do new and different things. Some advantages that could be realized could include performance, cost, size, etc.

Therefore, I was hoping that some of you in this community would have ideas of new applications and/or products that have made a difference to the applications you work on.

If you want to be referenced in the article, please include your name, position, and the company you work for!

Thanks in advance for your help!

Regards...
 
Jasonc24 said:
Greetings everyone... I am new to this group (third time to the site), but it looks pretty good thus far; there is a lot of good information.

I am writing an article regarding advances in hydraulic technology that allow machine designers to do new and different things. Some advantages that could be realized could include performance, cost, size, etc.

Therefore, I was hoping that some of you in this community would have ideas of new applications and/or products that have made a difference to the applications you work on.

If you want to be referenced in the article, please include your name, position, and the company you work for!

Thanks in advance for your help!

Regards...

So you are writing an article about something you don't actually now anything about?
 
Interesting.

Jason24, where is the article going to be published?
Why did you ask here instead of a hydraulic forum?
I am asking because the trade magazines would know where and who to ask for this information. Most of the time the editors just e-mail their sources asking for opinions on various topics.

Pierre, often editors don't know a lot about the articles they write. That is why they ask the people they consider to be industry experts and quote them.
 
K!

I was assuming that he did not know anything 'bout hydraulics because of where he was posting, i.e. this forum, when there is a lot of ressource on the web to go first.

Last night when I read this post, you where on the site and i tought you where the one to give the best answers.

In the other hand, I've read sooooo many papers that where published by poeples just writing other people knowledge down. A pitty.
 
OK, a teaser, but who are you?

Go to http://www.deltacompsys.com/ If you did a google search for hydraulc motion control you would find this link.

If the rest of you want to know about the advances in hydraulic motion control then say so here. Otherwise this should be covered on a hydraulic forum http://www.patchn.com/forum1/viewforum.php?f=7
where the information will not get lost ( hopefully ) in all the other threads here.

I don't like tell me all you know questions. Be specific.

Pierre, this is one of the places to find information on hydraulic motion control. As a long time member of this and Ron's forum you should know that. I just don't say much about it because Phil doesn't like advertising and only %1 of the people on the forum care and finally, this is a PLC forum.
 
Thank you for the assistance... Pierre, you are quite witty!

As for the selection of the forum... I have found that typically in a PLC forum you find Controls Engineers. These Engineers design control systems of all sorts, and typically not just the PLC portion of it. All of us are required to do thing outside the PLC, like servos, pneumatics, hydraulics, HMIs, etc.

The perception at many places is that hydraulics are simple, and that they are handled by machine repairmen. Therefore, at the hydraulic forums I have found there to be a lot of mainteance guys participating, not design engineers that implementing the latest technology.

Regardless, thank you gentlemen for your assistance and participation!
 
Peter:

Please forgive me... I neglected to answer your questions with my first reply.

The article is for Control Design Magazine. They have supplied me with a bunch of names and contacts, however these contact names have mostly been for manufacturers. Manufacturers are very valuable, of course, but I was hoping to obtain some more information from actual SIs, as they don't get clouded with marketing buzz.

I am interested in seeing how some hydraulic advances have allowed hydraulic actuation to replace servos in some applications. The company I work for recently did a tool changer for a large machining system with all hydraulics, as it was more cost effective than servos while still providing the necessary cycle time. This is the kind of information I am looking for.

Anyway, thank you for the assistance.

Best regards...
 
To date my knowledge about advanced hydraulic motion control is somewhere close to zero, so I would be happy to read over your shoulder while you discuss the subject!
 
Something that is PLC related, Communication & hydraulic motion control

Early on in our history we realized that commincations between the PLC and motion controller was very important for two reasons. The first is performance. We could see that using a serial port was very slow compared to transfering the data across the back plane of a PLC ( back in those days it was a mulitbus or VME bus ). Our first controllers were designed with the cooperation of the PLC manufacturers and designed to their specifications. This provided quick and easy access to the controller from the PLC. However, this required a different module for each PLC. There wasn't an economy of scale and there was a PLC religious issue. If the customer didn't like the PLCs for which we designed motion controllers we were out of luck. Sometimes a customer would buy the PLC just to get the motion controller but that was rare. We could see that field buses were the future and made our own product that could communicate using Ethernet and field bus. A controller that can use many field buses and many different application layers on Ethernet can work well with almost any PLC. The motion controller must get a good grade in 'plays well with others'. Today, the leading hydraulic motion controllers either fit in the rack or communicate using a field bus or Ethernet. The only major hydraulic motion controllers that fit in the PLC rack are the 1746-QS, 1756 HYD02 and 1756 M02AS. Since Rockwell dominates the market in the US, it still makes sense for Rockwell to have motion controllers that fit in the rack. The Control Logix motion modules have a very nice set of motion blocks that make writing a state machine in ladder pretty easy. A key goal of both Delta and Rockwell, with the Control Logix, is to make the motion control look pretty much the same to the PLC user whether the axis is a servo motor or a hydraulic cylinder. Often times our customers will have both types of axes in a system. Having a unified simple way of mixing and matching axis types to fit the application is a big plus. The SLC is as different story. Each SLC motion module is very different from the others. This not only makes mixing and matching axis difficult but learning the different controllers is difficult for both the customer and the tech support. Our first generation motion controllers suffered from the same flaw since we only made the hydraulic motion controllers and not the servo motor controllers. I am less familiar with the Rexroth HNC modules. I will let Norm speak for the HNC.

More to come. 'What make a hydraulic motion controller different from a servo controller?'
 
Maybe you can write an article about the tool changing system that you worked on in Control Design Magazine?
I would sure like to read it.
I don't know nuthin from nuthin, but I do find it surprising that Hydraulics are replacing servos, and not the other way around.
One thing is for sure Peter will know.
Please post here.
I know it's not a hydraulic forum, but it sounds like it would be great reading.
 
Hydraulic vs Servo Motor

gbradley said:
Maybe you can write an article about the tool changing system that you worked on in Control Design Magazine?
I would sure like to read it.

I have a couple articles in Control Design. Can you tell me which month? I think I know the application. I think there was a Parker HSE ( hydraulic systems specialist ) involved that did the real work. If so, his name is Bruce Besch. I will check
I can find out more from him. I didn't get involved in why the old application didn't work. I just gave some tech support on getting the hydraulic design to work.

gbradley said:
I don't know nuthin from nuthin, but I do find it surprising that Hydraulics are replacing servos, and not the other way around.
You aren't alone. Servo motors and hydraulic systems have different strengths and weakness. Servo motors are better for smaller applications and some of the bigger applications that have a continuous duty cycle. Hydraulic systems are better for large mass applications, low duty cycle applications and those where one needs to apply force or torque as in a press.
Read this
http://www.controldesign.com/Media/MediaManager/wp_010_delta_electrohydrailics.pdf

Cost wise it is easy to see that servo motors and especialy stepper motors are much cheaper than a small hydraulic system. Servo motors are also very efficient on applications like conveyors were there are few mechanical loses and the motor is running continuosly. Servo motors also have an advantage in that I bet most of you would try to make a servo motor to run before trying to get a hydraulic system to running. There is a built in prejudice toward servo motors over hydraulics.

Now for the hydraulic advantages.
1. ONE motor/pump can supply pressurized oil ( read energy ) to many actuators or hydraulic motors. The motor/pump only needs to supply enough energy during cover the energy needs during one cycle. When an actuator isn't moving, energy can be stored in accumulators for use during peak usage. Servo motors must each be sized for the peak loads and each axis must have its own motor.
2. Hydraulic systems are ideal for applying a force or torque as in a press. When the hydraulic system applies force, there is very little energy consumed. There is just a little leakage. A motor must apply torque which will cause heat and possibly destroy the servo motor.
3. On big systems the motor/pump can be mounted remotely so the power unit is not part of the system being moved. Hydraulic motors and cylinders are small relative to the force that can be applied. The ability to use hose to transport energy from one point to another is a big advantage in some applications. Some ships have hydraulic drives. This isn't as efficient as a direct drive to propeller but then the shaft doesn't need to be perfectly aligned, in fact the propeller can be rotated if need be. That can be handy when docking.
4. Hydraulic works well with either motors ( rotary ) or cylinders ( linear ).

Hydraulic disadvantages.
1. Hydraulics are non-linear. This can be minimized by proper design but too many hydraulic designers don't know how to properly design a system.
2. Hydraulics with servo valves can be in-efficient. A lot of energy can be lost as the oil flow through a servo valve.
3. It can leak and be a environmental mess. One of the things I stess is using a servo controller to make 'smooth moves'. Acceleration and deceleration ramps using S curves reduces the hydraulic shock. This puts less stress on the system which means fewer break downs and leaks.

Think of hydraulics as just a way to get energy from one point to another much like a drive shaft gets energy to the rear wheels of a car. The hydraulic guys may take offense to this. They like to talk about does a pump pump oil or pressure. It is a religious issue. I think of oil as just a way to move energy from one point to another. It just happens to be very flexible.

Finally, I really don't know right know why that customer, mentioned in Control Designed, switched to hydraulics. My guess is that it is an application that should have been a hydraulic application in the first place but someone decided that servo motors were the latest craze without evaluating the relative merit of hydraulic vs servo motor.

I am done for the night.
 
thanks peter for the posts. i am really starting in the control automation world (1 year), and it is for me very valuable to know whats behind other control methods. i am an electronic eng. and i never thought of hydraulics. it seems that i must start looking and learning a little more of it.
 

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