ElmoMC SimplIQ Digital Servo Drives-Bell Command Reference - Manual (Page 279)

Position Command Clipping (No. 1 in Figure 6-14)
The position command is clipped to the following values:
VH[3] above and VL[3] below, if the position feedback sensor counts linearly
XM[2] above and XM[1] below in UM=4
YM[2] above and YM[1] below in UM=5
The clipping is necessary because, in some circumstances (explained previously), the sum
of the software command and the external command, or even the software command
alone, may exceed the command limits.
Hard Stop (No. 2 in Figure 6-14)
This block stops the desired position reference to its present position if a Hard Stop
switch is sensed.
Right Limit Switch (No. 3 in Figure 6-14)
This block stops the desired position reference to its present position if an RLS switch is
sensed, and if the output of the position reference generator is less than the controller
position command.
Forward Limit Switch (No. 4 in Figure 6-14)
This block stops the desired position reference to its present position if an FLS switch is
sensed, and if the output of the position reference generator is greater than the controller
position command.
Rate and Acceleration (No. 5 in Figure 6-14)
This block limits the speed and acceleration of the controller position command. The
block limits both the acceleration and the deceleration to the SD parameter, and the speed
command (the derivative of the position command) is limited to VL[2] from below and
VL[3] from above.
The rate and acceleration limiter block intervenes in the following situations:
The position command to the controller experiences an abrupt change; for example,
when a Hard Stop switch is sensed or when a Hard Stop switch is released.
The reference generator tries to control the motor in the permitted position range,
but at too great a speed.
The position command moves towards its permitted boundary (VL[3] or VH[3]) at a
speed greater than can be braked until the boundary with SD acceleration. For example,
near VH[3], the upper speed limit may be much lower than VH[2]. When the position
command equals VH[3], the maximum allowed speed command is zero.
Example:
The software reference generator generates a sine, using PVT.
The low position limit is
VL[3]= -5000
. The input to the stop manager and its output
(the position command to the controller) are depicted in the following figure:
SimplIQ for Steppers Application Note The Position Reference Generator
MAN-STECR (Ver. 1.1)
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