Reset setpoint for large error

[Valentino]

Hello all,

I am using DASYLab to control a servo valve to operate a single acting hyraulic cylinder for material testing (crushing rocks).  I want to apply a constant rate of force (eg. 50 lbf/sec).  I am using a counter and scaling module to get a linear increasing setpoint, and a PID to control output to the valve.  For sudden large errors I would like to be able to reset my setpoint to start at the actual current load and continue to increase at the defined rate of load from that point. For example if my system is at 35000lb and the sample cracks the actual load may drop to 25000 lb, while the setpoint stays at 35000lb and continues to increase at 50lb/s.  I want to be able to set a limit for the error, and if exceeded, resest the setpoint to that point and continue at linear rate. Therefore the system would continue to increase the load from the 25000lb at 50lb/s rather than rushing to catch up to the 35000lb setpoint.

Any help would be appreciated.

Thanks,

Frank

[TomRizzo]

Frank,

To trigger, I would create a formula subtracting the command versus the setpoint and trigger it when the difference is grater than you desire. 

I would suggest you to use a variable to add or subtract to your setpoint so that, everytime you trigger an event, you can change the variable with a "Set Variable" module.  This would be the best way to do it.

Also, I would be very carefull using DASYLab for real time controll because you cannnot control Windows responce and idle time and this could make your actuator loose control.