MC_GrpReadActVel

 Function Block A function block groups an algorithm and a set of private data. It has inputs and outputs. - Reads the actual velocity of the group and the axes in the group.

Inputs

Input	Data Type	Range	Unit	Default	Description
Enable	BOOL	0, 1	N/A	No default	If TRUE, this function block reads the current actual velocity of the group and the axes in the group.
AxesGroup	AXES_GROUP_REF	N/A	N/A	No default	The axes group the actual velocity is read from.
CoordSystem	SINT	One of these enumeration values: MC_COORDINATE_SYSTEM_ACS = 0 MC_COORDINATE_SYSTEM_MCS = 1 MC_COORDINATE_SYSTEM_PCS = 2	N/A	No default	The coordinate system used when reading the actual velocity.
Velocity[ ]	LREAL	No range	User unit/sec	No default	An array where the velocity data is written. The length of the array must equal the maximum number of axes allowed in the group. The maximum number of axes is an argument to the MC_CreateAxesGrp function block used to create axes groups.

Outputs

Output	Data Type	Range	Unit	Description
Valid	BOOL	No range	N/A	If TRUE, the velocities were read without error.
Error	BOOL	No range	N/A	If TRUE, an error has occurred.
ErrorID	INT	No range	N/A	Indicates the error if Error output is TRUE. See the table in PLCopen Function Block ErrorIDs.
PathVelocity	LREAL	No range	User unit/sec	The current measured path velocity of the group. This is measured by taking the square root of the sum of the squared velocities of each axis.

Remarks

• 
  

• This function or function block returns cached data.
  See Program a Multi-Core Controller for more information.

• See Coordinated Motion, the top-level topic for Coordinated Motion.
• See Function Blocks - General Rules for more information about how inputs and outputs work.
• The MC_GrpReadActVel function block fills the array specified by the Velocity argument with the actual velocity of the system in the coordinate system specified by the CoordSystem argument.
  • The measured path velocity is also calculated and reported by the PathVelocity output.
• This function or function block does not generate any motion.

• 
  

• • The actual velocity is smoothed over the last 10 samples.
    This reduces the error in velocity estimation but introduces a small amount of phase delay in the reported velocities.
  • Currently, only the ACS coordinate system is supported.
    See Coordinate Systems for more information.

• There is a one-to-one correspondence between the axes in the Axes Group and the velocity values in the Velocity Array.
• Each element in the Velocity Array corresponds to the axis element in the Axis Group array.
• If a index in the Axes Group is unassigned, the velocity value for that array element in the Velocity array is 0 (zero).
• If the element does contain an axis, the velocity value is filled with the current actual velocity for that axis.
  • This is an example of how this works:
    

Figure 6-141: MC_GrpReadActVel

FBD Language Example

FFLD Language Example

IL Language Example

            BEGIN_IL "Instruction List"
This is a low-level language and resembles assembly
     CAL Inst_MC_GrpReadActVel(DoRead, Group, CoordsSys, VelList)
END_IL

ST Language Example

Inst_MC_GrpReadActVel(DoRead, Group, CoordSys, VelList);

See Also

• MC_GrpReadActAcc
• MC_GrpReadActPos
• MC_GrpReadCmdPos
• MC_GrpReadCmdVel