Chapter 7 Motion Control ASDA-A2
Revision February, 2017 7-27
7.11 The Description of E-Cam Function
E-Cam is a virtual cam which is implemented by software. It includes Master axis and Slave axis.
The illustration is as the following:
In PT mode, the position command (slave) is issued by the external pulse input (master). The two
is merely the linear scaling relation (its scaling equals to e-gear ratio). However, instead of linear
scaling, E-Cam is defined by cyclic curve profile, just like the cam shape. In physical machine cam,
slave axis can operate as variable speed motion, alternating motion, intermittent motion, etc by
master axis with the constant speed motion. It is very extensive in application. Using E-Cam could
have similar effect. The following table describes the differences between E-Cam and Machine
Cam.
Machine Cam E-Cam
Structure
Return to the original position
after rotating a cycle.
It might not return to the original position
after rotating a cycle. The structure could
be in spiral shape like mosquito coil
incense.
Smooth
Performance
It is determined by the fineness of
the real process.
It is interpolated by cubic curve via
software
Position
Accuracy
Very precise (when it has no
vibration)
The command is very precise, but the
actual position might have deviation due
to the servo delay.
Long Distance
Motion
The longer the slave axis is, the
bigger the cam will be. It is not
easy to make.
Change the value of the table will do. It is
easy to realize.
The Necessity
of Master Axis
The master axis is necessary.
The master axis is unnecessary when it is
applied to constant speed motion. It will
do by using the internal signal of the
servo drive.
Flexibility
It is inconvenient to change and
modify and it is expensive as well.
It will do by re-setting the parameter.
Maintenance
Machine will wear and the
maintenance is necessary.
No need to maintain.
Others
The master axis needs space and
it consumes energy as well.
Save the space and energy which
protects the environment.
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