On Jan 21, 1:10 pm, szuhsien <x...@no.email> wrote:
> Thanks for ur attention.
> I just set up a oil hydraulic system and mechanism that is such a MTS(material test system).
> And my question is how to let my cylinder go forward at a constant velocity.
> Because when the cylinder contact my specimen(I have many different specimens), it will produce a reacting force and let the cylinder can't go forward at a constant velocity I set.
> So I know it needs adjusting input voltage to servo valve .
> I have looked much information from Ni discussion forums, but I totally have no idea about this.
> I only know that I need to use PID control. My feedback signal is from LVDT.
> What kind of ni card I need? I have pci-6033e, although its analogy outpout only can + - 10v.
> At least, 6033e can let me test servo valve between -5v to 5v.
> Can I use DAQ-card to achieve my goal? Because I'm not sure if 6033e supported pid toolkit.
> By the way, this question is just the beginning.
> I need to finish displacement control, force control, and fatigue loading control at 10Hz.
> servo valve: + - 10v input , 0v is at centered position. 10v is P port 100% to A Port. threshold<0.1%
> platform: XP, Labview 8.2 (includes Real-time module, PID toolkit)
First thing when you say MTS do you Mean the Company located in
Minneapolis, MN that makes hydraulic test systems that do the type of
testing you describe or are using the word as an acronym? Yes, you
will need a closed loop control system to do all you want to do. The
system should have both a load cell for measuring the axial force
applied to a specimen and a LVDT for measuring the displacement of the
piston and provisions for either load or position control. My
recommendation is you use Labview strictly for data acquisition and
you you use an all analog control system in your application. With
position control you could use a ramp input to move the piston at a
constant velocity. You can build an analog PI controller fairly
easily. You should not use the D part of PID in a closed loop system
that uses a hydraulic piston for an actuator.