This topic describes how to control pressure on a hydraulic cylinder without position feedback. Pressure feedback is still required. For details on position-pressure control, see Position-Pressure Overview.
See the Controlling Solely Position, Pressure, or Force topic for details on the module required for pressure control.
To enter pressure control, set up an Event Step sequence to do the following:
Use the Open Loop command to get the axis close to where the pressure begins to increase. Note that the pressure may spike due to stiction in the cylinder. Therefore, do not start pressure control until the axis is close to where you want to start controlling pressure.
Issue the Set Pressure Command to set up the pressure control.
Issue an Open Loop command with the Monitor Pressure mode bit set. Note that the Monitor Pressure bit may not appear in the Mode word dialog. The Monitor Pressure bit is bit 8 in the Mode word. To set the Monitor Pressure bit, OR the Mode word with 0x0100.
When the Actual Pressure exceeds the Pressure Set A, the axis will enter pressure control. You will have to tune the system to correctly handle the transition to pressure control. See the Position-Pressure Overview for details on pressure tuning.
To change the pressure, issue the Set Pressure command.
To exit pressure control, issue an Open Loop command with the Monitor Pressure bit cleared. If the Actual Pressure is less than the Pressure Set B, the axis will exit pressure control.
Copyright (c) 1997-2015 by Delta Computer Systems, Inc.