MC_GearInPos, MCP_GearInPos – Engage the master/slave velocity ratio in defined position

Block SymbolsLicensing group: MOTION CONTROL

Function Description

The MC_GearInPos and MCP_GearInPos blocks offer the same functionality, the only difference is that some of the inputs are available as parameters in the MCP_ version of the block.

The functional block MC_GearInPos engages a synchronized motion of master and slave axes in such a way that the ratio of velocities of both axes is maintained at a constant value. Compared to MC_GearIn, also the master to slave position ratio is determined in a given reference point, i.e. following relation holds:

\frac{S l a v e P o s i t i o n - S l a v e S y n c P o s i t i o n}{M a s t e r P o s i t i o n - M a s t e r S y n c P o s i t i o n} = \frac{RatioNumerator}{RatioDenominator} .

In case that the slave position does not fulfill this condition of synchronicity at the moment of block activation (i.e. in an instant of positive edge of Execute input and after execution of previous commands in buffered mode), synchronization procedure is started and indicated by output StartSync. During this procedure, proper slave trajectory which results in smooth synchronization of both axes is generated with respect to actual master motion and slave limits for Velocity, Acceleration, Deceleration and Jerk (these limits are not applied from the moment of successful synchronization). Parameter setting MasterStartDistance=0 leads to immediate start of synchronization procedure at the moment of block activation (by the Execute input). Otherwise, the synchronization starts as soon as the master position enters the interval MasterSyncPosition $\pm$ MasterStartDistance.

Notes:
1. The synchronization procedure uses two algorithms: I. The algorithm implemented in MC_MoveAbsolute is recomputed in every time instant in such a way, that the end velocity is set to actual velocity of master axis. II. The position, velocity and acceleration is generated in the same manner as in the synchronized motion and a proper 5th order interpolation polynomial is added to achieve smooth transition to the synchronized state. The length of interpolation trajectory is computed in such a way that maximum velocity, acceleration and jerk do not violate the specified limits (for the interpolation polynomial). The first algorithm cannot be used for nonzero acceleration of the master axis whereas the second does not guarantee the compliance of maximum limits for the overall slave trajectory. Both algorithms are combined in a proper way to achieve the synchronized motion of both axes.

2. The block parameters (execution of synchronization and velocity/acceleration limits) have to be chosen so that the slave position is close to SlaveSyncPosition approximately at the moment when the master position enters the range for synchronization given by MasterSyncPosition and MasterStartDistance. Violation of this rule can lead to unpredictable behaviour of the slave axis during the synchronization or to an overrun of the specified limits for slave axis. However, the motion of both axes is usually well defined and predictable in standard applications and correct synchronization can be performed easily by proper configuration of motion commands and functional block parameters.

Inputs

uMaster	Master axis reference	Reference
uSlave	Slave axis reference	Reference
Execute	The block is activated on rising edge	Bool
RatioNumerator	Gear ratio Numerator	Long (I32)
RatioDenominator	Gear ratio Denominator	Long (I32)
MasterSyncPosition	Master position for synchronization	Double (F64)
SlaveSyncPosition	Slave position for synchronization	Double (F64)
MasterStartDistance	Master distance for starting gear in procedure	Double (F64)
Velocity	Maximal allowed velocity [unit/s]	Double (F64)
Acceleration	Maximal allowed acceleration [unit/s $^{2}$ ]	Double (F64)
Deceleration	Maximal allowed deceleration [unit/s $^{2}$ ]	Double (F64)
Jerk	Maximal allowed jerk [unit/s $^{3}$ ]	Double (F64)
BufferMode	Buffering mode	Long (I32)
	1 .... Aborting (start immediately) 2 .... Buffered (start after finish of previous motion) 3 .... Blending low (start after finishing the previous motion, previous motion finishes with the lowest velocity of both commands) 4 .... Blending high (start after finishing the previous motion, previous motion finishes with the lowest velocity of both commands) 5 .... Blending previous (start after finishing the previous motion, previous motion finishes with its final velocity) 6 .... Blending next (start after finishing the previous motion, previous motion finishes with the starting velocity of the next block)
SyncMode	Synchronization mode (cyclic axes only)	Long (I32)
	1 .... CatchUp 2 .... Shortest 3 .... SlowDown

Outputs

yMaster	Master axis reference	Reference
ySlave	Slave axis reference	Reference
StartSync	Commanded gearing starts	Bool
InSync	Slave axis reached the cam profile	Bool
CommandAborted	Algorithm was aborted	Bool
Busy	Algorithm not finished yet	Bool
Active	The block is controlling the axis	Bool
Error	Error occurred	Bool
ErrorID	Result of the last operation	Error
	i .... REXYGEN general error
SyncDistance	Position deviation of the slave axis from synchronized position	Double (F64)

Example

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