NREF

ASCII - Command	NREF
Syntax Transmit	NREF [Data]
Syntax Receive	NREF <Data>	Available in
Type	Variable rw	MMI	Yes
ASCII Format	Integer8	CANBus Object Number	35AD (hex)
DIM	-	PROFIBUS PNU	1773 (dec) IND = 0000xxxx (bin)
Range	0 .. 20	DPR	173 (dec)
Default	0
Opmode	All	Data Type Bus/DPR	Integer8
Drive State	-	Weightning
Start Firmware	1.20
Configuration	No	Revision	1.8
Function Group	Position Controller	EEPROM	Yes
Short Description	Homing Mode

Description

For linear movements, before a positioning movement can be started, a homing operation must be carried out. The reference point set in this operation is valid until the next hardware reset of the amplifier. An attempt to start positioning without a reference point being set causes a warning (LCD display n09). Any previously set reference point is cancelled before the homing operation begins.

A preset zero-point offset is considered for the position output and display. Exception: Homing=5. In this case, the true current position is displayed. You can shift the zero-crossing point of the motor shaft within one turn by using ENCZERO.

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 four-pole resolvers, there are two zero-crossings per turn. For six-pole resolvers, there are three zero-crossings per turn. If the transition of the reference switch lies very close to the zero-crossing point of the feedback unit, the positioning to the zero mark can vary by one motor turn. The repetition accuracy of homing operations made without zero-point recognition depends on the traversing velocity and the mechanical design of the reference or limit switch.

For homing modes 1 and 3, a digital input must be configured as a zero-mark input (home position) (INxMODE=12 or I/O expansion card).

For homing modes 2 and 4, a digital input must be configured as a hardware limit switch (INxMODE=2 or INxMODE=3).

For homing modes 1, 2, 3, 4, 5, and 7, the setting of the zero-pulse offset for the Encoder Equivalent Output (EEO) output is taken into account (the zero point is set so both the output of the zero pulse and the display of the zero position appear at zero-pulse offset).
The setting of the reference offset (ROFFS) is taken into account for all homing modes. The zero point is assigned to a freely chosen absolute position value.

If a multiturn encoder is used, every homing move can be started. If the homing move is ready, RSOFFS is calculated automatically and a

SAVE command is executed. Wenn the drive is switched off and on, the drive has the same position.

Status	Short Description	Additional Description
NREF=0	Set Reference at actual position	The actual position becomes the refernce point ( the target and the actual position are set to ROFFS). The distance between the actual and the target position is lost.
NREF=1	Traverse to the reference switch with zero-mark recognition.	The drive starts a move using DREF, until a positive edge at the reference switch is detected. Then the distance to the next zero point of the resolver is calculated and a move to this position is started. If the reference switch is present (input signal = high), a move in the opposite direction of DREF is startet until a negative edge is detected. Then the homing move is started. If a hardware limit switch is detected (start of the homing move behind the reference switch), the direction is changed and a move is started, until a positive and a negative level edge is detected at the reference switch. Then the homing move is started. At the end of the homing move, the target and the actual position are set to ROFFS.
NREF=2	Move to hardware limit-switch, with zero-mark recognition.	The drive starts a move using DREF until the hardware limit switch is reached. Then the direction is changed and the drive moves to the next zero point of the resolver. At the end of the homing move, the target and the actual position are set to ROFFS.
NREF=3	Move to reference switch, without zero-mark recognition.	The drive starts a move using DREF, until a positive edge at the reference switch is detected. The position at the edge of the reference move is eqivalent to ROFFS. Then the drive stops. If the reference switch is present (input signal = high), a move in the opposite direction of DREF is startet until a negative edge is detected. Then the homing move is started. If a hardware limit switch is detected (start of the homing move behind the reference switch), the direction is changed and a move is started, until a positive and a negative level edge is detected at the reference switch. Then the homing move is started. The real stop position is not the edge of the reference switch and depends on the selected speed and the deceleration ramp.
NREF=4	Move to hardware limit-switch, without zero-mark recognition.	The drive starts a move using DREF, until the hardware limit switch is detected. Then the direction is changed, and a move is started until the hardware limit switch is high again. The position at the edge of the hardware limit switch is eqivalent to ROFFS. Then the drive stops. The real stop position is not the edge of the hardware limit switch and depends on the selected speed and the deceleration ramp.
NREF=5	Move to the next zero-mark of the feedback unit.	Homing to the next zero point of the resolver. The moving direction is given by variable DREF. DREF=0 negative DREF=1 positive DREF=2 the direction is given by the shortest distance.
NREF=6	Set Reference at actual position, without loosing target position	The actual position becomes the reference point ( the position setpoint and the actual position are set to ROFFS). The difference to NREF=0 is, that the distance between target and actual position is not lost (position error).
NREF=7	Move to mechanical stop with zero-mark recognition	When the homing mode 7 is started, the peak current limit threshold IPEAK is set to REFIP (peak current for the homing mode in A) in the drirection given by DREF (DREF=0 positive, DREF=1 negative). When the drive moves the motor, the contouring error is monitored and if the error becomes higher than PEMAX / 2 (half of the contouring error window), the direction is changed and a move to the next zero point of the resolver is startet. The motor stops in that position and sets the actual and the target position to ROFFS. The peak current of the drive is set back to the original value of IPEAK.
NREF=8	Move to absolute SSI-position	When a homing mode 8 is started, the actual position of an external Multiturn SSI encoder (GEARMODE=7) is read, calculated with GEARI and GEARO to internal counts and an offset value ROFFS2 is added. The result is a target position for a motion task that is started. When the target position is reached, the IN-POSITION bit is set. This function is done for a gantry application with multiturn encoder feedback and coupling of the two drive using SSI multiturn,
NREF=9	Move to mechanical stop without zero-mark recognition	When the homing mode 7 is started, the peak current limit threshold IPEAK is set to REFIP (peak current for the homing mode in A) in the drirection given by DREF (DREF=0 positive, DREF=1 negative). When the drive moves the motor, the contouring error is monitored and if the error becomes higher than PEMAX / 2 (half of the contouring error window), this position is used to set the actual and the target position to ROFFS. The peak current of the drive is set back to the original value of IPEAK.