Homing

The purpose of the reference run (homing method) is to synchronize the motor controller with the encoder index of the motor or position switch in a system.

To activate the mode, the value "6" must be set in object 6060_h(Modes Of Operation) (see "DS402 Power State machine").

If a reference and/or limit switch is used, these special functions first need to be activated in the I/O configuration (see "Digital inputs and outputs").

When using the motor in "Open Loop" mode the object 320A_h:04 needs to be set to the value "1" before starting the homing mode.

The following bits in object 6040_h(control word) have a special function:

• Bit 2 is used to trigger an quick stop. If it is set to "0", the motor carries out a quick stop with the ramp set in object 6085_h. The motor then goes into "Switch on disabled" mode (see the "DS402 Power State machine" section).
• Bit 4: If the bis is set to "1", the referencing is started. This is set forth until either the reference position is reached or bit 4 is set to "0" again.

The following bits in object 6041_h(status word) have a special function:

The following objects are required to control this mode:

• 607C_h (Home Offset): Specifies the difference between the zero position of the application and the reference point of the machine.

• 6098_h(Homing Method):

  Method used for referencing (see "Reference run method")

• 6099_h:01_h (Speed During Search For Switch):

  The speed for the search for the switch

• 6099_h:02_h (Speed During Search For Zero):

  The speed for the search for the index

• 609A_h(Homing Acceleration):

  Acceleration and deceleration for the reference run

• 2056_h(Limit Switch Tolerance Band):

  After moving to the positive or negative limit switch, the motor controller permits a tolerance range that the motor may not further travel. If this tolerance range is exceeded, the motor stops and the motor controller changes to the "Fault" state. If limit switches can be activated during the reference run, the tolerance range selected should be sufficiently large so that the motor does not leave the tolerance range when braking. Otherwise, the reference run cannot be completed successfully. After completion of the reference run, the tolerance range can be set back to "0" if this is required by the application.

• 203A_h:01_h (Minimum Current For Block Detection):

  Minimum current threshold that, when exceeded, detects blocking of the motor at a block.

• 203A_h:02_h (Period Of Blocking):

  Specifies the time in ms that the motor is nevertheless still to travel against the block after block detection.

• 203A_h:03_h (Block Detection Time)

  Specifies the time in ms that the current has to be at least above the minimum current threshold in order to detect a block

The reference run method is written into object 6098_h as a number and defines whether referencing should be performed on a switch flank (rising/falling), a current threshold for block detection or an index pulse is referenced, or in which direction the reference run should start. Methods that use the index pulse of the encoder are within the number range 1 to 14, 33 and 34. Methods that do not use the index-pulse of the encoder are between 17 and 30, but their travel profiles are identical with those of the methods 1 to 14. These numbers are shown in circles in the following figures. Methods that do not use a limit switch, and instead travel against a block is to be detected, must be called up with a minus in front of the method number.

For the following diagrams, the negative movement direction is to the left. The limit switch is located in front of the mechanical block in each case, and the reference switch (home switch) is between the two limit switches. The index pulses come from the encoder, which is connected with the motor shaft and motor controller.

For methods that use homing on block, the same illustrations apply as for the methods with limit switch. New illustrations are not shown as nothing changes except for the missing limit switches. In this case, the limit switches have to be replaced by a mechanical block in the illustrations.

Homing on block is currently working in Closed-Loop only.

"Homing on block" works like every other homing method except for positioning, a block (mechanical end stop) is used instead of a limit switch. Two settings need to be set:

Methods 1 to 14, and 33 and 34 use the index pulse of the encoder.

Methods 17 to 32 are identical with the methods 1 to 14 with the exception that referencing is only performed on the limit or home switch and not on the index pulse.

• Methods 1 to 14 contain an index pulse
• Methods 15 and 16 do not exist
• Methods 17 to 30 do not have an index pulse
• Methods 31 and 32 do not exist
• Methods 33 and 34 reference only to the next index pulse
• Method 35 references to the actual position

The following methods can be used for homing on block:

• Methods -1 to -2 and -7 to -14 contain an index pulse
• Methods -17 to -18 and -23 to -30 do not have an index pulse

Reference the limit switch and index pulse.

Method 1 references a negative limit switch and index pulse:

Method 2 references a positive limit switch and index pulse:

These methods reference the switch flank of the reference switch and index pulse.

In the methods 3 and 4, the left switch flank of the reference switch is used as a reference:

In the methods 5 and 6, the right switch flank of the reference switch is used as a reference:

These methods reference the home switch and index pulse (with limit switches).

For these methods, the actual position relative to the reference switch is unimportant. With method 10, referencing is for instance always to the index pulse on the right next to the right flank of the reference switch.

The methods 7 to 10 take the positive limit switch into account:

The methods 11 to 14 take the negative limit switch into account:

These methods reference the limit switch without the index pulse.

Method 17 references the negative limit switch:

Method 18 references the positive limit switch:

These methods reference the switch flank of the reference switch without the index pulse.

In the methods 19 and 20 (equivalent to methods 3 and 4), the left switch flank of the reference switch is used as a reference:

In the methods 21 and 22 (equivalent to methods 5 and 6), the right switch flank of the reference switch is used as a reference:

These methods reference the home switch without the index pulse (with limit switches).

For these methods, the actual position relative to the reference switch is unimportant. With method 26, referencing is for instance always to the index pulse on the right next to the right flank of the reference switch.

The methods 23 to 26 take the positive limit switch into account:

The methods 27 to 30 take the negative limit switch into account:

Reference the next index pulse.

For these methods, referencing is only to respective next index pulse:

References to the actual position.