Moog servo control


Thread Starter

Steve Cooper.

I need to replace an antiquated, read dying, control......

Can anyone help? I have to re-fit several machines with four hydraulic rams controlled by Moog servo valves. I would like to use PC based
control and I need to know is there any simple way, via DAC perhaps, that an 8 bit TTL I/O port can be persuaded to do the deed!

Any help will be greatly appreciated.

Steve Cooper.
A couple of years ago I did a refit for 7 hydraulic presses with Rexroth servo valves, (I have also used Moog, just not on this instance)
and found that the best solution was to use a servo valve controller and use the PC to send it commands via RS484. For very accurate pressure control you will need 300-500 hz response on your control loop. I used Rexroth's DLC-100 valve controllers and achieved better than 1 psi apparent pressure control at a setpoint of 18000 PSI output from an intensifier. (I note apparennt pressure, because my transducer calibration error is greater than the apparent errror, but the point is the control loop followed setpoint). I chose to use the secondary controller for a number of reasons, but the primary driving factor was safety and reliability, and there was no way we were going
to get the required loop response from a PC at that time. PCs are somewhat faster now, but you still need to carefully weigh the safety issues in light of your particular application. You don't want someone getting hurt. Rexroth now has a new controller out that is supposedly even better and can take commands via control-net, device-net, ether-net, and a number of other protocols, perhaps Moog has one as well. These usually incorporate the valve amplifier which will you will need to purchase anyways. Let your supplier do the legwork there and earn his commission.

Peter Nachtwey

> Can anyone help?

There are hydraulic motion controllers that can connect to a PLC using Ethernet or Profibus DP.
Search 'hydraulic motion control' or 'hydraulic Ethernet' or 'hydraulic Profibus' on google. You could control all your machines from one

>I would like to use PC control

The PC would be mainly a HMI.

> and I need to know is there any simple way,
> via DAC perhaps, that an 8 bit TTL I/O port can > be persuaded to do the deed!

8 bits is coarse. There are much better boards with 12+ bit DACs.
I have recently worked with some Moog servo valves on hydraulic drives. The first question is how fast of a system response do you need? Next is are you doing position, velocity and/or target pressure control? Why I ask is because I doubt you can achieve fast / precise control with a PC's DAQ I/O board. If the whole process is slow and coarse, then no problem as long as your I/O board can provide enough current (+/- 200mA) per valve.

But, you certainly can achieve it if you are using the DAQ I/O board to provide a setpoint to one of the Servo-Controller/Amplifiers available
from Moog, or other vendors. In effect, if you use the PC-DAQ device to output an analog signal (+/- 10 vDC) to the Servo-Controller, it will look after the position/velocity loops for you. They are relatively cheap, and it will keep the heat from the drivers out of your PC. Good luck,

Ian Lippert

James Johnson

I did a job similar to yours last year. I replaced 4 Moog servo controllers with a PLC with 12 bit analog outputs. It works great. I could have thrown a computer on the com port for HMI but a 4 line/20 Char OIU saved my customer $$$
Good luck,
Have Fun,
James Johnson
M/D Control Systems, Inc.
[email protected]
We do Plastic Parison closed loop servo control using CTC PLC's and an error amp and a servo amp. The CTC generates a profile command based on a millisecond clock. It receives up to 300 profile points from a cheap PC using quick basic. The control looks very similar to dedicated parison controllers. It is adjusted while running, profiles are readily saved and manipulated, and the system once set runs without the PC.

It is my experience with parison control in the plastics industry that no matter what control you have you need to allow for mother nature or the helpful henry which will cause the system to go full speed to one end of the travel or the other. Our tooling is designed to do that.

thank you,

John Ross
Mohawk Molding
[email protected]
Hi, I had a similar task a few years ago using 760 moog valves. We went for a simple 386 based ind pc using 8 bit amplicon pc30 cards (DAC
o/p). Due to the 760's being current control devices, we interface them with the existing driver circuit of the valves. I believe that Moog
still offer these cards in analog format if that's easier. The software was developed in house and was for driving single actuators, at
1m/s, 20kn load, +/- 1mm. The load control was via strain guage load cell devices, position via LVDT, and overshoot via accelerometer. The
system was very successfull, and was built into 7 production lines in the UK with no problems at all. The machines have, after 7 years service, been transfered into europe to continue working, unlike the human elements that were made redundant !
Dear Steve,
It's a simple thing to control anything with PC.

Use your centronics (Parallel Port. fed 8 data lines of your LPT1 with Opto Isolator MOC 3041. and subsequent circuitary of Triac. with triac you will be able to control any dam device....

then a 6 line program in C will do u r work.

i hope that's enough.....

feel free to ask me more


Harko Schwartz

Hi Steve
I have a pc based cnc controller that is capable of analog output and can run up to 32 axes. The system is MachineMate and it can control up to 6 machines at the same time.

Harko Schwartz
Moog servo valves are used to control the coilbox transfer arm in hot strip mill of Tisco.There are two close loop working in the control system, one is position loop, another is speed loop. when other variables are unchanged why some time servo ref become abnormal rather not usual resulting unusual jerk in the transferarm, is there any prblem with moog servo valve or hydraulic motor or hydraulic line.
Hi there,

I wonder if someone actually reads this old topic, but I do hope so. I've stumbled upon an old PC30 I/O card that I can't seem to able to get any drivers or software to. I hope that "K.Smith" reads this, or anyone else who might have drivers or any information at all on this old card. The thing is that I need card like this to finish my graduation project at my university. So if someone has any knowledge what so ever on this card please let me know.

Thanks in beforehand,

Lars Bark
[email protected]
A number of years ago we retrofitted a Unimate 2000B 6 axis hydraulic robot. We used a PC running RTLinux and later used RTX+Win2000 for real time control. We designed an inteface that was purely digital (no D/A) using 6 PWM channels driving the MOOG servovalves. We were able to replace the 8 original A3 size PCBs with a single A5 PCB and a PC. Also went from point to point to path control with 4th order interpolation for jolt control.

It worked very well and resulted in a number of conference papers on the subject.