EPOS2 / EPOS4: Homing auf aktuelle Position

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Topic:

The Homing Method "Actual position" (or called "Current position" too) has got a different number if the EPOS2 (-> method '35') and EPOS4 (-> method '37') is compared.

• What is the reason for this modified "Homing method" number by the two product lines?
• What number has to be used by the "EPOS Command Library"?

Technical background:

The number of the Homing Method "Actual position" has changed from '35' (EPOS2) to '37' (EPOS4) by the EPOS firmware specification because the CiA402 specification by the "CAN in Automation" organization has changed it. maxon products always focus to adapt on the latest CiA402 state of development when the product line is released.

• CiA402 has just mentioned the "Homing method" number '35' to be used for "Actual position" when the EPOS2 was developed.
• The CiA402 specification defines that "Homing method" number '37' has to be used for "Actual position" nowadays. The former "Homing method" number '35' will be even deleted by the next version of the IEC 61800-7-201.
• maxon decided to adapt to this latest CiA402 standard by the development of the EPOS4 again.

The up-to-date CiA402 states the following:

• Homing method 35: "Current position" (= "Actual position")
  
  
• Homing method 37: "Current position" (= Actual position")
  

Solution:

Direct configuration of the "Homing Method" by the object 0x6098:

• If there is an EPOS2 to in use, a value of '35' has to be written to object "Homing Method" 0x6098 to use the "Actual position" as the new home position.
• If there is an EPOS4 to in use, a value of '37' has to be written to object "Homing Method" 0x6098 to use the "Actual position" as the new home position.

Using the EPOS Command Library:

The EPOS Command Library (or LabView VI) is a high-level wrapper which typically processes even more than one object access by each function call. It is also internally adapts the resulting required object access to the EPOS, EPOS2, EPOS4, or IDX product line in use. The "EPOS Command Library" makes it easier for software engineers to focus on the required functionality but take less care about CiA402 implementation details.

The EPOS Command Library (and LabView VIs) function call "VCS_FindHome" handle the usage of '35' or '37' internally properly depending if an EPOS2 or EPOS4 is connected.

• If VCS_FindHome configures "HM_ACTUAL_POSITION" (35) in case of an EPOS2, the "EPOS Command Library" writes a value of '35' to object 0x6098.
• If VCS_FindHome configures "HM_ACTUAL_POSITION" (35) or a value of '37' in case of an EPOS4, the "EPOS Command Library" writes a value of '37' to object 0x6098 automatically in any case.

There is no need for an application code programmer to check the product type and adapt the "Homing method" number if there is the "EPOS Command Library" in use. It is possible to use "HM_ACTUAL_POSITION" (35) independent what EPOS product type is in use.

Conclusion in case of the "EPOS Command Library":
You can always use '35' by the function call "VCS_FindHome" (resp. the LabView VI) of the "EPOS Command Library". This works for the EPOS2 and EPOS4 as well. The "EPOS Command Library" configures the object "Homing method" (0x6098) properly for both controllers.