Bosch 6000 User's Guide download pdf (Page 234)

Chapter 6. Following

219

Repeatability of

the Trigger

Inputs and

Sensors

Some applications may use the trigger inputs for functions like registration moves,

GOWHENs, or new cycles. For these applications, the repeatability of the trigger inputs and

sensors add to the overall position error.

In the 6000 controller, the position capture from the trigger inputs have approximately 100 µs

repeatability, and the sensor repeatability (SR) should be determined, too. Velocity ∗ time =

distance, so the error due to repeatability is (SR + 0.0001 seconds) ∗ speed = error. If the

sensor repeatability is given in terms of distance, that value can be added directly.

Preset vs. Continuous Following Moves

When a slave performs a preset (MCØ) move in Following mode (FOLEN1), the commanded

position is either incremental or absolute in nature, but it does have a commanded endpoint.

The direction traveled by the slave will be determined by the commanded endpoint position,

and the direction the master is counting.

Let's illustrate this with an example. Assume all necessary set-up commands have been

previously issued for our slave (axis #1) and master so that distances specified are in

revolutions:

FOLRN3 ; Set Following slave-to-master ratio numerator to 3

FOLRD4 ; Set Following slave-to-master ratio denominator to 4

; (ratio is 3 revs on the slave to 4 revs on the master)

FOLEN1 ; Enable Following on axis #1

FOLMD10 ; Set preset move to take place over 10 master revolutions

MC0 ; Set slave to preset positioning mode

MA1 ; Set slave to absolute positioning mode

PSET0 ; Set current absolute position reference to zero

D5 ; Set move distance to absolute position 5 revolutions

GO1 ; Initiate move to absolute position 5

If the master is stationary when the GO1 command is executed, the slave will remain

stationary also. If the master begins to move and master pulses are positive in direction, the

slave will begin the preset move in the positive direction. If the master pulses stop arriving

before 10 master revolutions have been traveled, the slave will also stop moving, but that

GO1 command will not be completed. If the master then starts to count in the negative

direction, the slave will follow in the negative direction, but only as far as it's starting

position. If the master continues to count negative, the slave will remain stationary. The

GO1 command will not actually be completed until the master has traveled at least 10

revolutions in the positive direction from where it was at the time the GO1 command was

executed. If the master oscillates back and forth between it's position at the start of the GO1

command to just under 10 revolutions, the slave will oscillate back and forth as well.

The master must be counting in the positive direction for any preset (MCØ) GO1s commanded

on the slave to be completed. If mechanics of the system dictate that the count on the source

of the master pulses is negative, a minus (-) sign should be entered in the FOLMAS command

so that 6000 controller sees the master counts as positive.

Continuous slave moves (MC1) react much differently to master pulse direction. Whereas a

preset move will only start the profile if the master counts are counting in the positive

direction, a continuous move will begin the ramp to its new ratio following the master in

either direction. As long as the master is counting in the positive direction, the direction

towards which the slave starts in a continuous move is determined by the argument (sign) of

the D command. The slave direction is positive for D+ and negative for D-.

If the master is counting in the negative direction when slave begins a continuous move, the

direction towards which the slave moves is opposite to that commanded with the D command.

The slave direction is positive for D- and negative for D+.

If the master changes direction during a continuous slave move, the slave will also reverse

direction. As with standard continuous moves, the GO1 will continue until terminated by S,

K, end-of-travel limits, stall condition, or command to go to zero velocity. As with preset

moves, the sign on the FOLMAS command determines the direction of master counting with

respect to the direction of actual counting on the master input.

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Bosch 6000 User's Guide Page 234

Comments to this Manuals

Bosch 6000 User's Guide Page 234

Comments to this Manuals

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