Gemini GV6K and Gemini GT6K Programmer's Guide

Enter/Exit
Following Mode
While Moving
Pause and
Continue
TVEL and TVELA
Commands
TASF, TAS & AS
Axis Status Bits
Changing
Feedback Sources
(Servo Axes only)
Following and
Other Motion
Conditional
Statements Using
PMAS
The FOLENØ command may be executed while a follower axis is moving at constant ratio. In
this case, the current velocity becomes the constant velocity, and the follower may accelerate
or decelerate to other velocities. The FOLEN1 command may not be executed while the
follower axis is moving in the non-Following mode. Attempting to do so will result in the
error response “MOTION IN PROGRESS”.
A program may be paused and continued, even if configured as a follower. The program does
not lose track of the master input, even though motion is stopped. As usual, if a program
finishes normally, or if COMEXS is set to zero (COMEXSØ), the program may not be continued.
If a program is resumed, partially completed Following moves will be completed; however, the
remainder of the move is completed over the entire original master distance (FOLMD value).
The TVEL and VEL commands have always reported an unsigned value (i.e. magnitude),
consistent with the fact that the V command is always positive, even if the move direction is
negative. When Following is enabled (FOLEN1), TVEL and VEL report the net magnitude of
commanded velocity due to following and/or shifting. For example, if the follower axis is
Following in the positive direction at 1 rps, TVEL reports 1.000. If a shift in the negative
direction of 1.5 rps is then commanded, TVEL will report 0.5 – still positive, even though the
net direction is negative.
By contrast, TVELA and VELA have always been signed. In the above example, TVELA will
report -0.5.
Axis Status (TASF, TAS and AS) bits 1-4 represent the motion status of an axis. Bits 1 and 2
represent the moving and direction status of the net motion of an axis, including the
combination of following and shifting.
Bits 3 and 4 represent acceleration and velocity, respectively. With Following disabled
(FOLENØ), the accel and velocity can only be due to a commanded time-based profile. With
Following enabled (FOLEN1), the net commanded velocity and accel could be due to
following the master and/or a simultaneous shift (time-based profile). Bits 3 and 4 only reflect
the acceleration and velocity status of the time-based profile, not the combined command.
For example, if the follower axis is Following in the positive direction at 1 rps, TAS reports
1ØØØ. If a continuous shift (FSHFC2) of 0.8 rps in the negative direction is then commanded,
TAS will report 1Ø1Ø, while the shaft is decelerating to 0.2 rps. When the continuous shift
velocity is reached, TAS will report 1ØØ1.
Changing feedback sources (SFB) may result in a follower axis Following its own feedback.
For this reason, changing feedback sources is not allowed while a master is specified
(FOLMAS).
Following motion is initiated with the GO command, just like normal motion. Other motion,
which does not depend on the motion of an external master, may not be used while a follower
axis is in Following mode (FOLEN1). These motion types include jog mode, joystick mode,
and homing. To use these motion types, Following must be disabled (FOLENØ) — see
Enter/Exit Following Mode While Moving above for precautions.
The master cycle position (PMAS) value may be used in the comparison argument of these
commands:
• WAIT & GOWHEN: If it is desired to WAIT or GOWHEN on a master cycle position of the
next master cycle, one master cycle length (value of FMCLEN) should be added to the
master cycle position specified in the argument. This allows commands that sequence
follower axis events through a master cycle to be placed in a loop. The WAIT or
GOWHEN command at the top of the loop could execute, even though the actual master
Chapter 7. Multi-Tasking 195