AXY:Shadow Axis Concept

Shadow Axis Concept

This article describes shadow axes from the motion point of view.

On the picture above there are:

• three different(separated) SERCOS rings

• two MC controllers each connected to two SERCOS rings

• first SERCOS ring connects Drive#1 to MC#1

• second SERCOS ring connects MC#1 with MC#2

• third SERCOS ring connects MC#2 with Drive #2

First MC has:

• one axis (Axis) connected to the first SERCOS ring to a Drive#1
• second axis (Remote) connected via second SERCOS ring to MC#2

Second MC has:

• one axis (Shadow master) connected to the second SERCOS ring to a MC#1
• second axis (Shadow slave) connected via third SERCOS ring to Drive#2

Virtual Connection consists of:

• Remote axis on MC#1 running on S3net.master
• Shadow master on MC#2 running on S3net.slave
• Connection between S3net.master and S3net.slave swaps pcmd with pfb and drive status (ds) with drive control word (dcw)

Shadow axis pair consist of:

• Shadow master
• Shadow slave

With the following swapping of variables:

Shadow Master	direction	Shadow Slave
pfb	→	pcmd
pcmd	←	pfb
vfb	→	vcmd
vcmd	←	vfb
drive status	→	drive control word
drive control word	←	drive status

New Syntax

We are adding new option (value=10) to the existing options of the <axis>.slave values. Using the <axis>.MasterSource property for defining master axis.

<shadow slave axis>.MasterSource = <shadow master axis>.pcmd
<shadow slave axis>.slave = 10

	NOTE
	Shadow slave axis can be only enabled if both <shadow master axis> is enabled (sending enabled drive status) and <shadow slave axis>.en = 1

	NOTE
	Both shadow master or slave axis does not accept any motion command (MOVE, JOG, ....) while they are in a shadow-relationship.

	NOTE
	Both shadow master or slave axis can not belong to a group.

	NOTE
	Shadow master can not be a slave axis. (i.e its slave property must be 0)

	NOTE
	Remember that axes with lower elementid number are called before. This can influence additional propagation delay.

Implementation Details

• Assigning <axis>.slave = 10 both <axis> and <axis>.MasterSource become pair of master-slave shadow axes.

• During <axis>.slave = 10 assignment all the conditions of master-slave shadow pair are checked.

• Rearranging RTK priorities is skipped.

See Also:

Virtual Axis