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Data transfer

ServoOne User Manual SERCOS II and III

ID no.: 1108.26B.3-00 Date: 04/2020

Data transfer

on the display changes to 5 and the corresponding bits in the drive status word are set/
cleared.
The readiness for the control (drive follows the reference values) is represented via bit
15, bit 14 and bit 3 in the status word.
In the ideal case, the actual value is to be read by the controller during the start of
control and specified as the reference value until the controller signals readiness
in the status word. If the drive moves during the start of control (e.g. due to motor
autocommutation on linear drives, here the drive signals that it is not yet ready, drive
state 4), the position changes are applied automatically by the controller.
Controllers that "only" obtain the current actual position once before the start of
control, specify this value as the reference value and do not update it again after
autocommutation (no evaluation of the status word), will have a reference value
difference. A shutdown due to a tracking error may be the consequence.
To prevent this situation arising, the drive can move, under drive control, to the position
specified by the controller at the start of regulation by setting P 0156 Enable
operation option code to MOVE_COMMAND(1). A shutdown or jerking movement to
the target position due to a reference value difference in the axis at the start of control
will then be prevented.
This function also depends on the configuration of P 0743 maximum tracking error.

If P 0743 is equal to 0,

the position tracking error is disabled. The drive switches on without a

correction and sends the position reference value from the NC directly to

the controller. The drive may move to the specified reference position with a

jerk. Larger distances will result in a speed tracking error, depending on the

parameter configuration. A jerking axis movement will be the consequence.

If P 0743 is not equal to 0,

the position tracking error is enabled. The drive reads the reference

position from the controller and moves, under drive control, to this position

(position correction). If the difference between the position specified by the

controller and the actual position is greater than the tracking error P 0743,

the drive switches to the error state, however without moving (no large axis

movement). Otherwise the drive corrects the difference using the slow jog

speed P 0168[1] and the acceleration from P 2242 quick stop. Once the

position is reached, the drive changes to state 5 and the drive follows the

reference values from the controller (only now is readiness signalled in the

status word).

IMPORTANT:

Using the scaling, the ramp setting that the system accesses is also to be set to
correct, realistic values. This aspect relates to the parameters:

P 2242 quick stop, depending on the configuration this parameter comes

into effect if there is an error

P 0168 (jog, index 0: fast jog speed, index 1: slow jog speed)

The position correction described above can take a very long time with a very slow jog
speed or, for example with P 0168[1] = 0, will not occur at all. In this situation the drive
would remain in system state 4, because the reference value cannot be achieved.

Bit 13: Drive STOP (feed enable)

The "Drive stop" signal is state-controlled and is active low; i.e. if the signal
"Drive stop = 0", the drive is in the state "Drive stop". The input signal is represented by
bit 13 in the master control word.

7.3.4

Drive status word S-0-0135.0.0

The drive status word contains all important control information for the drive and must
be mapped to the cyclic part of the AT.

Bit no.

Description

15 – 14

Ready

00: Drive not ready for switching on the power, because the internal checks have

not yet been completed successfully.

01: Drive ready for switching on the power.

10: Drive control section ready and power supply switched on, there is no drive

torque and the power stage is inhibited.