Hello,
I am trying to control the speed of a pneumatic cylinder's piston using pressure as input. I have a pressure regulator to control the pressure at the top of the cylinder and a passive flow control valve (not based on flow feedback) at the bottom of the cylinder, which I can use to change the resistance to the flow out of the bottom side of the cylinder.
My plan is to control the downward speed of the cylinder's piston.
I am running the attached labview code and it is giving me trouble. I am measuring the downward speed of the piston using an encoder and a counter (NI 9361). I am controlling the pressure at the top of the cylinder using NI 9263 Analog output, which is connected to a regulator (fast acting) which control the pressure at the top of the cylinder.
I am using digitalout (NI 9472) to switch the direction of motion of the cylinder. When I want to go down I, electronicaly, connect top to the regulator and bottom to flow control valve. When I want to go up I connect the bottom to supply pressure and top to atmosphere. I am not worried about stroke going up.
Problem durin down stroke: When I run the program, the counter (which measures downward speed of piston) lags the cylinder by a few seconds. SO the feedback control is useless since the piston takes only 0.25 seconds to reach bottom and the lag in the speed in a few seconds.
I think it's a programing issue since I can get the counter task itself working without any lag and at 2000 Hz. With the feedback loop, I can hardly get 200 Hz and I still run into buffer issues in about 10 seconds.
Any help is appreciated.