Staubli CS8C, Instruction Manual

Page: 68 / 248

© Stäubli 2009 –
D28070504A
CS8C 68 / 248
Position reading
The position reading is done with the
e00CurrPos
analog input. The position is in degrees, with an accuracy of
360/(4* e00Counts )
.
The encoder position is updated every
4 ms
. When a preset is done while the encoder is moving, it applies to the
start of the current
4 ms
time interval. The encoder position is updated only with the next time interval, where it is
assigned the preset position plus the encoder movement of the last
4 ms
. In that way, no encoder movement is
lost with the preset.
Position capture (latching)
Position capture is used to record the encoder position on a rising signal for a fast input, and then read the position
later.
Position capture procedure:
•
Activate the
e00EnLatch
digital output.
•
On the next rising or falling signal for the fast input
e00LatchSig
, the encoder position is recorded in the
e00LatchPos
analog input and the
e00Latch
digital input is activated to show that the capture has been
executed. The
e00EnLatch
Input/Output is then automatically deactivated.
The precision of the capture is less than one microsecond. It is possible to cancel a capture request at any time
by deactivating the
e00EnLatch
output.
Note:
The position capture is made:
- On the rising edge of the
e00LatchSig
signal if the
e00LatchEdgFall
digital output is set to
False.
- On the falling edge if the
e00LatchEdgFall
digital output is set to True.
It is possible to filter out bounds on the latch signal by specifying a filter delay in milliseconds
using the
e00LatchFilter
analog output: the latch is then effective only if the signal remains
stable during the specified time. The latched position is then always the position at the rising or
falling edge of the latch signal.
Errors
An encoder reading error is signalled by the
e00HwErr
digital input. If the encoder is rotating too fast, it is not
possible for the controller to know for certain how many rotations the encoder has made. In this case, the
e00OvsErr
signal is activated. The maximum encoder speed is
7500
rpm.
Note:
When the encoder has moved by more than one turn, the system is able to detect its resolution
that is then written to the
e00CountsMes
analog input. If this resolution does not match the
specified resolution
e00Counts
, the encoder is in error and the
e00CountsErr
signal is
activated.
The
e00PowerErr
digital output is activated when the encoder power supply is not correct.
To reactivate the encoder after an error, it is necessary to reset it using the
e00RstErr
digital output.
CAUTION:
The internal encoder position counter uses only
32
bits. When the encoder position reaches
2 31*360/(4*e00Counts)
degrees, an overshoot occurs and the position becomes
-
2 31*360/(4*e00Counts)
.
No error is reported: The overshoot must be managed by software programming, either by
using a preset to avoid it, or by correcting the position with an offset of
2 32*360*4*e00Counts
degrees.
^
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