Delta RMC101 - Manual (Page 676)

RMC100 and RMCWin User Manual
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Note: For pressure/force axes, this command will take effect on the analog module’s drive
output, if one is available. Only 16-bit analog cards have drive outputs, therefore this command
will have no affect on 12-bit analog cards. Also, because drive outputs are only assigned to input
channels 0 and 2 on 16-bit cards, only analog or pressure axes using those input channels will
be able to issue this command. Otherwise, this command behaves normally on pressure/force
axes, except that no status registers other than the Drive field are modified by this command.
The Open Loop command allows the Controller to directly specify values for the analog output.
The output range is -10000 to 10000 and is given in millivolts. However, the drive outputs are not
precision outputs. You cannot rely on the output being exactly the value you specify. Look up
specifications in the online help index for the tolerance on your particular interface module’s drive
outputs.
The O command uses the following parameters from the last open loop profile specified:
The Command Value field specifies the desired drive in millivolts to output. The current null drive
is added to this value.
The Speed field is not used.
The Acceleration and Deceleration fields control the rate at which the drive output ramps to the
requested value. Acceleration is used when the drive output is moving away from 0 and
deceleration is used when drive output is moving toward 0. The actual meaning of the values
depends on the Acceleration/Deceleration mode bits in the Mode word. Notice that only modes 1,
2 and 3 are used:
Mode 1
Acceleration and deceleration are given in millivolts per millisecond. For example, if the current drive
output is 0 millivolts, and the Command value is 1000 millivolts, and the Acceleration is 50, then it will
take 20 milliseconds for the drive output to reach 1000 millivolts.
Mode 2
Acceleration and deceleration are given as distances. That is, the drive will be ramped over the
distance specified. This mode is most useful when stopping on poor performing hydraulics. This
mode cannot be used for starting from a stop because no drive will be applied since the position does
not move, and conversely, the position does not move because there is no drive. For example, if the
current drive output is 1000 millivolts, and the Command value is 0 millivolts, and the Deceleration is
4000, then the axis will ramp the drive down to 0 in the time it takes the axis to move 4000 position
units.
Mode 3
Acceleration and deceleration are given in milliseconds. For example, if the current drive output is 0
millivolts, the Command value is 1000 millivolts, and the Acceleration is 50, then it will take 50
milliseconds for the drive output to reach 1000 millivolts, as the drive will increase 20 millivolts each
millisecond.
Note: If a move crosses 0 drive, then Deceleration will be used until the drive reaches 0, and
then Acceleration will be used until the final drive is reached.
Tip: If you are going to be changing from closed loop to open loop, you must be aware of the following.
While in closed loop and holding a position, the drive may be switching back and forth between small
positive and negative drives. If an open loop command is given to go to a non-zero drive, the starting
drive may have a sign opposite of the requested drive. In this case, the drive will decelerate down to
zero millivolts and then accelerate up to the new drive. For example, if the current drive is -10 millivolts
and an open loop command requests a drive of 2000 millivolts (2V), the drive will ramp from -10 to 0