MC_GrpReadActVel

Description

MC_GrpReadActVel 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 via the 'PathVelocity' output. This function block does not cause any motion.

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• • 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 to learn more.

Figure 7-173: MC_GrpReadActVel

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 Axes Group array. If a index in the Axes Group is unassigned then the velocity value for that array element in the Velocity array will be 0. If the element does contain an axis then the velocity value will be filled with the current actual velocity for that axis. Here is an example to illustrate how this works:

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• This function or function block returns cached data. See Programming a Dual Core Controller for more information.

Related Functions

MC_GrpReadActPos, MC_GrpReadActAcc, MC_GrpReadCmdPos, MC_GrpReadCmdVel

Coordinated Motion, the top-level topic for Coordinated Motion.

Arguments

For more detail on how inputs and outputs work, refer to PLCopen Function Blocks - General Rules.

Input

Enable	Description	If True, then this function block will read the current actual velocity of the group and the axes in the group
	Data type	BOOL
	Range	0, 1
	Unit	N/A
	Default	—
AxesGroup	Description	The axes group from which the actual velocity will be read
	Data type	AXES_GROUP_REF
	Range	N/A
	Unit	N/A
	Default	—
CoordSystem	Description	The coordinate system used when reading the actual velocity
	Data type	SINT
	Range	One of the following enumeration values: MC_COORDINATE_SYSTEM_ACS = 0 MC_COORDINATE_SYSTEM_MCS = 1 MC_COORDINATE_SYSTEM_PCS = 2
	Unit	N/A
	Default	—
Velocity[]	Description	An array where the velocity data will be 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 MC_CreateAxesGrp that is used to create axes groups.
	Data type	LREAL
	Range	N/A
	Unit	User units per second
	Default	—

Output

Valid	Description	If true, the velocities have been read without error.
	Data type	BOOL
Error	Description	If true, an error has occurred.
	Data type	BOOL
ErrorID	Description	Indicates the error if Error output is set to TRUE. See the table PLCopen Function Block ErrorID Output
	Data type	INT
PathVelocity	Description	The current measured path velocity of the group, measured by taking the square root of the sum of the squared velocities of each axis.
	Data type	LREAL
	Unit	User units per second

Example

Structured Text

Inst_MC_GrpReadActVel(DoRead, Group, CoordSys, VelList);

IL

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

FBD

FFLD

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