Controlling Linear Actuator via Load Cell

[AMac]

Hello,

I need to control the position of a linear actuator based on the force feedback from a load cell (rated up to 100 ft/lbs) connected to the tip of the linear actuator.  What I want to be able to do is to set a force and have the linear actuator (driven by a stepper motor) move until it is within 0.1 ft/lb of the force setpoint.  Once within 0.1 ft/lb of the setpoint, I would like to hold and control to the setpoint based on a user configured hold time.

I have the following hardware:

PXI-1033 chassis

PXI-7340 Motion controller card

UMI-7764 Terminal Block

P7000 Drive

Omega Engineering Load Cell model number LC201-100

Omega CCT-80 Load Cell Signal Conditioner

Omega FAR-1 Power Supply

I have the + output of the CCT-80 connected to the Analog Input (AIN1) and the - output connected to the Analog Input Ground (AIGND).  This output signal is -10V to +10V (verified by DMM)

I have the ADC range set to -10 to +10

I'm reading the ADC as fast as possible (get about 700 samples/second) and this just isn't fast enough to control to the precision that I need.  Also, it seems like there is a substantial amount of noise on this line.

Does anyone have any recommendations on improving the speed of the ADC read, or how to reduce the noise on the line?

If my requirement of holding to 0.1ft/lb is too strict for this hardware (7340 motion card) is there something else that I should try?

If I'm missing any other info that is needed to help me out, let me know and I'll update this post.

Thanks!

[kyleshook]

Hello AMac,

I have a setup similar to yours with a load cell attached to a linear stage. I want to use position control of the stage to apply a set load on the load cell (position-based explicit force control). Do you have a example VI I could look at if yours was successful?

Thanks,

Kyle