Reference traverse
ASCII: NREF
Default: 0 valid for OPMODE 8
You can choose which type of reference traverse should be performed. A preset zero-point offset (screen page
"Encoder" is taken into account for the position output and display.
Exception: Homing5—inthis case the true current position is displayed.
You can shift the zero-crossing point of the motor shaft within one turn, at will, by using the "NI offset"
parameter (screen page "Encoder").
Zero-point recognition: the reference point is set to the first zero-crossing point of the feedback unit (zero mark)
after recognition of the reference switch transition. Two-pole resolvers and all encoders have just one
zero-crossing per turn, so the positioning at the zero mark is unambiguous within a motor turn. For 4-pole
resolvers there are two zero-crossings per turn, and for 6-pole resolvers there are three zero-crossings.
If the transition of the reference switch lies very close to the zero-crossing point of the feedback unit, then the
positioning to the zero mark can vary by one motor turn.
The repetition accuracy o f homing operations that are made withou t zero-point
recognition depend s on the traversing speed and the mechanical d esign of the
reference switch or limit-switch.
Homing 0 Sets the reference point to the setpoint position (the following error is lost).
Homing 1
Traverse to the reference switch with zero-mark recognition.
In this case, a reference traverse can also be made without hardware limit-switches. The precondition is one of
the initial situations shown below:
negative traverse,
positive rotation
negative traverse,
negative rotation
Homing 2
Move to hardware limit-switch, with zero-mark recognition. The reference point is set to the first
zero-crossing of the feedback unit (NM, zero mark) beyond the limit-switch.
Homing 3
Move to reference switch, without zero-mark recognition. The reference point is set to the
transition of the reference switch.
Homing 4
Move to hardware limit-switch, without zero-mark recognition. The reference point is set to the
transition of the hardware limit-switch.
Homing 5
Move to the next zero-mark of the feedback unit. The reference point is set to the next
zero-mark of the feedback unit.
Homing 6 Sets the reference point to the actual position (the following error is not lost).
Homing 7
Move to mechanical stop, with zero-mark recognition. The reference point is set to the first
zero-crossing of the feedback unit (NM, zero mark) beyond mechanical stop.
The pulse current is set by the parameter REF.-IPEAK on the screen page "Current controller".
Homing 8
Drives to an absolute SSI position. At the start of the homing run, a position is read in from the
SSI input (GEARMODE=7), converted according to the scaling factors GEARI and GEARO and
the reference offset, and then used a the target position.
On the following pages you can find the paths traversed during homing types 1 to 5 for every
possible initial situation (positive rotation, negative and positive directions of motion).
The meanings of the abbreviations in the drawings are:
N
limit-switch NSTOP
P
limit-switch PSTOP
SP
start position
R
reference switch
vref
preset velocity
NM
zero mark of the resolver
58 Setup Software
Screen page "Homing" 07/03 BECKHOFF
To Next Page
Loading...