3.1.3.5.4.4 Common Use Cases
3.1.3.5.4.4.1 Use Case 1: Motion is allowed during commissioning
Method 0/1 should be used
Method 0 gives perfect precision without any previous tuning.
If the final system has coupled joints or heavy or single side loads it might be required to perform Offset
detection before assembly for optimal performance.
If the movement of up to one pole pair is not acceptable method 1 can be selected, where the movement
can be much less. The PID controller used for method 1 needs to be tuned carefully.
Note
Try moving the arm to a position in which gravity has no or little impact, for optimal performance of the
detection. For example the center of gravity should be right above or right below the axis of motion.
3.1.3.5.4.4.2 Use Case 2: Motion is not allowed during commissioning
When no movement is allowed during commissioning, method 2 can be used. This may happen when the
setup is already in the application. Note that the method has less detection accuracy, thus the commutation
efficiency can be less. In this case, it’s recommended to redo Offset Detection when the setup is allowed to
move.
3.1.3.5.4.4.2.1 Special case: Offset detection Method 2 with an Incremental encoder with
index
If an ABI encoder is used for commutation, a routine called “finding index” is usually required when enabling
the drive (the first time after booting the system), which will rotate the motor to find the index of the sensor.
With commutation method 2, the drive can find an internal temporary offset and use this offset until the index
is detected. Once the index is detected, it replaces the temporary offset by its corresponding value in the
object dictionary. In practice, Offset Detection can be carried out with method 0/1 during commissioning, the
result can be saved and method 2 can be executed. This way, no movement is required when enabling the
setup, and the torque control performance of the setup is still promised.
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