Sync Gear Ratio

A gear ratio can be applied between the master and slave axes during synchronous control. The motion of the master axis is multiplied by the gear ratio when calculating the motion of the slave axis. (This gear ratio is different from the Gear Ratio Numerator and Gear Ratio Denominator parameters of each axis.)

The following plots show the positions and velocities of a pair of axes running in synchronous control mode with a sync gear ratio of 2.

The Sync Offset status is recalculated when the sync gear ratio is changed. Once the new sync gear ratio is set, the Sync Offset will remain constant, even though the actual position difference between the master axis and the slave axis will likely change unless the sync gear ratio is 1.

When operating sync control using sync groups (see SetSyncGroup), sync gear ratio that is not equal to 1 cannot be used with the CatchUp startup type.

Changing the Sync Gear Ratio While in Motion

The sync gear ratio may be changed while the master and slave axes are in motion. To prevent a sudden change in the slave axis velocity, a catch up motion is inserted to transition the slave from the old sync gear ratio to the new sync gear ratio. During the catch up motion, the slave will follow the motion of the master axis using the new sync gear ratio, but an additional offset will be added over a period of time determined by the profile parameters of the catch up motion. The time taken for the catch up motion to complete is not affected by changes to the master axis velocity during this time.

The following plots show the positions and velocities of a pair of axes with an initial sync gear ratio of 2 that is later changed to 2.5 while the axes are still in motion.

Starting Sync Control Specifying the Sync Gear Ratio

Sync control with a gear ratio may be started while the master and slave axes are in motion. This will cause the slave to execute a catch up motion similar to when the gear ratio is changed. The catch up motion will depend on the velocity of the slave and master axes, the sync gear ratio, and the profile parameters.

The following plots show the positions and velocities of a pair of axes which are initially moving independently, and then synchronized with a sync gear ratio of 0.5.

To initiate sync control with no gear ratio while the master and slave axes are in motion, sync control with a gear ratio can be started specifying a sync gear ratio of 1. However, the catch up motion will add a position offset between the master and slave axes, which may be compensated using functions such as sync phase offset.

The sync gear ratio that is currently applied can be checked with the Sync Gear Ratio status of the slave axis.