Delta RMC151 - Manual (Page 169)

3 Controller Features
• Curve Start (Prs/Frc) (87)
• Curve Start Advanced (Prs/Frc) (89)
Exiting Pressure or Force Control
To exit pressure/force control, issue the Open Loop Rate (10) or Direct Output (9)
command. An Open Loop Halt or Direct Output Halt will also cause the axis to exit
pressure/force control.
Pressure/Force Limit
Pressure/Force Limit can be used on a pressure-only or force-only axis, although it is
typically not very useful. Pressure/force limit is most useful on axes that also have
position or velocity feedback. On pressure/force axes, pressure/force limit can only limit
the pressure/force while moving the axis with the Open Loop Rate (10) command.
For example, consider an axis on which force limit is enabled. If the is moving with an
open loop Control Output of 2 volts, and the Target Force is 300 lbs, the axis will move
with 2 volts Control Output until the Actual Force reaches 300 lbs. Then, the Control
Output will be limited so that the force will not exceed 300 lbs.
Notice that with a large open loop voltage, a pressure/force limited axis will behave
similarly to an axis in pressure/force control. That is, the pressure/force can be controlled
very accurately, even with the specialty pressure/force commands, such as a sine wave
(using the Sine Start (Prs/Frc) (76) command) or a cam (using the Curve Start (Prs/Frc)
(87) command).
Pressure/force limit cannot be used simultaneously with pressure/force control. If the axis
is in pressure/force limit, and a command is issued that puts the axis in pressure/force
control, the pressure/force limit will no longer be active and the axis will start controlling
the pressure/force. However, the Pressure/Force Limit Enabled status bit will still be set,
and if the axis exits pressure/force control, it will resume pressure/force limit.
Pressure/Force Control Status Bits
The following status bits give the status of the pressure/force control. These tell you what
the control is doing, and can also be very useful in user programs.
At Pressure/Force
When the axis is in Pressure/Force control or Pressure/Force Limit and the Target
Pressure/Force reaches the Requested Pressure/Force and the Actual Pressure/Force
is within the At Pressure/Force Tolerance window from the Target Pressure/Force, the At
Pressure/Force Status bit will be set. This bit indicates that the ramp is complete and the
axis is at the pressure/force.
Pressure/Force Control
The Pressure/Force Control Status bit indicates that the axis is in closed-loop
pressure/force control.
Pressure/Force Limit Enabled
This bit indicates that pressure/force limit is enabled. If an axis is in pressure/force
control, pressure/force limit will not be active. If the axis exits pressure/force control to
open loop or closed-loop position or velocity control, it will enter pressure/force limit if the
Pressure/Force Limit Enabled bit is on.
Pressure/Force Limited
This bit indicates that pressure/force limit is enabled and the axis is limiting the
pressure/force. If an axis is in pressure/force control, pressure/force limit will not be
active and this bit will not be set.
Pressure/Force Target Generator Bits
The Pressure/Force Target Generator bits in the Status Bits register indicate which
portion of the move the axis is currently in. These bits are useful when programming
complex motion sequences.
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