plc_user1973
Member
Peter is going throw up all over what I am about to present, but I have had success with this setup in the image attached.
PLC Triangle Research
www.tri-plc.com
MD Series, or F Series
10khz high speed encoder counter
PWM, PID
Ladder Logic with BASIC instructions executable on each rung.
Command Controls proportional valve.
http://www.commandcontrols.com/catalog/11/11-102.pdf
The prop valve I used was a bit bigger than the above.
Depending on how your programming works, you will have to make a decision for normally open or normally closed. My suggestion would be a normally open valve so you wouldn't need to use the PWM output on the PLC for normal full speed jogging. When the prop valve has no signal it it allows full flow. I know that a true proportional or servo valve is the best idea, but since you already have the tandem valve...
I have used the PID algorithm on the PLC and quadrature encoder as the feedback device. Depending what result of the algorithm returns you can turn on the directional valve depending on a positive or negative value returned by the algorithm and set the PWM depending on the absolute value of this same value returned by the algorithm.
I have got this to work on a sawmill where I work with a jog average speed of 6 inches/sec.
Tuning of the PID was tricky, but was satisfactory for me.
Not knowing any of the dynamics of your system, I can't say this is going to help you, but has worked for me who is on a very small budget.
The only thing I have had trouble with was the high speed counter was gaining/losing pulses which caused the display to show an inaccurate height measurement, a homing sensor would help with that. I really haven't been able to determine why its doing this. I am sure its something on my part and it doesn't happen often.
I truly don't want to aggravate Peter with my mess, but it does work. At the moment, it probably isn't worth mentioning any of my specifics as to pump size, valve size, type of gear reduction, etc. because I am probably going to get laughed out of here.
Regards
PLC Triangle Research
www.tri-plc.com
MD Series, or F Series
10khz high speed encoder counter
PWM, PID
Ladder Logic with BASIC instructions executable on each rung.
Command Controls proportional valve.
http://www.commandcontrols.com/catalog/11/11-102.pdf
The prop valve I used was a bit bigger than the above.
Depending on how your programming works, you will have to make a decision for normally open or normally closed. My suggestion would be a normally open valve so you wouldn't need to use the PWM output on the PLC for normal full speed jogging. When the prop valve has no signal it it allows full flow. I know that a true proportional or servo valve is the best idea, but since you already have the tandem valve...
I have used the PID algorithm on the PLC and quadrature encoder as the feedback device. Depending what result of the algorithm returns you can turn on the directional valve depending on a positive or negative value returned by the algorithm and set the PWM depending on the absolute value of this same value returned by the algorithm.
I have got this to work on a sawmill where I work with a jog average speed of 6 inches/sec.
Tuning of the PID was tricky, but was satisfactory for me.
Not knowing any of the dynamics of your system, I can't say this is going to help you, but has worked for me who is on a very small budget.
The only thing I have had trouble with was the high speed counter was gaining/losing pulses which caused the display to show an inaccurate height measurement, a homing sensor would help with that. I really haven't been able to determine why its doing this. I am sure its something on my part and it doesn't happen often.
I truly don't want to aggravate Peter with my mess, but it does work. At the moment, it probably isn't worth mentioning any of my specifics as to pump size, valve size, type of gear reduction, etc. because I am probably going to get laughed out of here.
Regards
