hydraulic system - how to control a servo valve?

[BuddyHaun]

I teach an engineering lab and we do everything you are trying to do with with the PCI-6024E although if I were to choose a similar card today it would be the PCI-6221 M series. The 10Hz rate you are looking to achieve will be more a function of your physical setup than the data acquisition card and PC. We have one system that we can only drive at about 1Hz because of the size of the hydraulic pump, hydraulic cylinder size, and proportional valve response time. Others with smaller capacity hydraulic cylinders can cycle faster. We use a pressure sensor to measure the pressure on the hydraulic cylinder. That pressure times the area of the cylinder is used to calculate load on the specimen. It is much cheaper than load cells, not to mention the fact that the students find it much more difficult to destroy than accidently overloading a load cell. This has been adequate for the data resolution that we need. You will need to make the calculations on your system to see if it meets your needs. We are using a draw wire sensor for displacement on specimens like wood and plastics and attach strain gages for metals. Most of my controls students use one of the simple PID examples as the basis for their control algorithms. I hope this information helps.

Buddy Haun

CLA, VirtEx LCC, Colorado School of Mines

[szuhsien]

Thanks for ur reply.

I know everything you mentioned, but it just hard to deal. The 10Hz rate is the rate of my fatigue experiment.

My specimens are human bone. And my clinder's diameter

[szuhsien]

Thanks for ur reply.

I know everything you mentioned, but it just hard to deal. The 10Hz rate is the rate of my fatigue experiment.

My specimens are human bone. And my clinder's diameter is

[szuhsien]

Thanks for ur reply.

I know everything you mentioned, but it just hard to deal. The 10Hz rate is the rate of my fatigue experiment.

My specimen is human bone. And my cylinder's diameter are 50mm (piston side) and 30mm ( rod side). The stroke of my cylinder is 80 mm.

I know that I need to figure out Load Resonant Frequency to know how many closed loop frequency I can give and system drop pressure and Bode polt of dynamic response and stuff like that.

So I think I need to do many tests to finish it and use least loop to achieve my goal.

Because my servo valve has 90 degree phase lag when frequency of input is at 50Hz and although servo valve can achieve more than 50Hz, my cylinder maybe can't follow my servo valve.

It depends on overall stiffness of cylinder. so I will minimize frequency of the closed loop to avoid phase lag.

I was wondering if you could support me any labview VI to refer.

Anyway thanks a lot.

S.H. Chen  

[BuddyHaun]

Here is a simple PID algorithm that I have students use as the basis for their programming.