Homing modes¶

Overview¶

Axes without an absolute encoder can use the homing function to restore the position to a previously defined location.

This can be done at the current location.

CiA 402 profile specification: IEC61800-7-201:2015 defines different homing methods, SOMANET supports methods 33, 34, 35 and 37.

Homing method 33/34¶

Methods 33 and 34 (move to next or previous single-turn position or “index pulse”) can be used to center on the sensor’s reference position (in positive or negative direction).

The shaft will rotate less than one rotation.

Homing method 35/37¶

Methods 35 and 37 (zero the current position) are used to define the current position as home position.

Note

Homing method 35/37 can be performed in any operational state. All other homing methods require the drive to be in “operation enabled” state.

Use case: Homing on current position while operation is not enabled

If the axis is moved to a desired homing position by external force (for example manually), Homing Mode 35/37 can be used to determine the current position as home.

Use case: Relative position command

The current position can be taken as the reference point.

Use case: Homing on current position

When the motor is moved to the desired position in CSP the position can be taken as homing position.

Settings for homing mode¶

Homing method¶

You can select the desired homing method in object 0x6098: Homing Method.

Value	Description	Remark
0	No homing method assigned.	This is the default value.
33	Homing on negative index pulse.
34	Homing on positive index pulse.
35	Homing on current position.	Methods 35 and 37 are identical.
37	Homing on current position	Methods 35 and 37 are identical.

Homing speeds¶

Two homing speeds must be selected in object 0x6099: Homing Speed: in a typical cycle, the faster speed is used to find the home switch and the slower speed is used to find the index pulse.

Note

Homing speeds are not required in method 35/37.

Homing acceleration¶

In object 0x609A: Homing Acceleration a value for acceleration during homing must be defined.

Note

An acceleration is not needed in method 35/37.

How to perform homing¶

The following diagram shows the steps that are necessary to perform the homing function.

../../../../../_images/perform_homing.png

After the home position is found, the position controller stays active, holding the motor at that position (except for method 35/37).

Using the Halt bit¶

The halt bit (bit 8 of the Controlword can be used to stop the drive without disabling the controller:

Set the halt bit to 1 to stop the motion
When the halt bit is reset to 0, the motion continues

Communications¶

Status of the homing process¶

Bits 10, 12, 13 of the Statusword (0x6041) are used to indicate the current state of the homing process:

Bit 13: Homing error

Bit 12: Homing attained

Bit 10: Target reached

Objects used¶

0x6098 Homing Method

Specifies the homing method that shall be used.

0x607C Home Offset

Offset from user’s zero position to the home position.

0x6099 Homing Speeds

Speed with which to move during homing.

0x609A Homing Acceleration

Acceleration used during homing.

0x6040 Controlword

Set bit 8 to 0 and bit 4 to 1 to start homing.

0x6041 Statusword

Indicates the current state of the homing process.

0x60E3 Supported Homing Methods

Array of supported homing methods.