ElmoMC SimplIQ Digital Servo Drives-Bell Command Reference - Manual (Page 276)

6.2.5.1 Jump-free Motor Starting Policy
Upon starting a motor using the MO=1 command, the motor should never jump. The first
and most important reason is safety. The other reason is to avoid an excessive position
error fault immediately after the motor is started.
To prevent the motor from jumping, the initial software reference is automatically set to
the present position of the motor, and the software command remains stationary until a
motion instruction is accepted. After setting MO=1, the motion mode is idle so that
sending a BG command without the prior specification of another motion mode will not
launch any motion.
Example 1:
Suppose that
MO=0, RM=0 and PX=1000
(motor is off, no external reference, present
position is 1000 counts). Entering
MO=1
will automatically set the software position
reference to 1000 counts, in Idle mode. The command sequence
PA=0;BG
will launch a
PTP motion from the position of 1000 counts to the zero position.
Example 2:
Suppose that
MO=0, RM=1, FR[3]=1, PY=3000
and
PX=1000
(motor is off, external
reference is generated by auxiliary encoder input with a unit follower ratio, the auxiliary
position is 3000 and the present position is 1000 counts). Entering
MO=1
will
automatically set the software position reference so that the total position reference will
equal PX, Therefore, the initial, automatic software command will be:
PX - FR[3] * PY = 1000 - 1*3000 = -2000
.
If the auxiliary encoder input is stable, the command sequence
PA=0,BG
will launch a PTP
motion from the position of 1000 counts to the position of 3000.
6.2.5.2 On-the-fly Switching of External Reference
Parameters
The parameters of the external reference generator can be changed on-the-fly only if the
software reference generator is idle. This can be verified by the motion status: MS should
return 0 or 1. When the parameters of the external reference generator are changed, the
software reference is set so that the motor will not jump at the instant the parameters are
set. The setting of the software reference is similar to that described in
section 6.2.5.1 .
The external reference parameters that can be changed on-the-fly are:
Parameter Description
FR[N] Follower ratio
EM[N] ECAM parameters
HY[N] Reading of auxiliary encoder
Table 6-16: External Reference Parameters for On-the-fly Changes
SimplIQ for Steppers Application Note The Position Reference Generator
MAN-STECR (Ver. 1.1)
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