Velocity Profiles For Collinear Moves - Allen-Bradley 1756-M02AS User Manual

Termination Type Example Path
4 - Follow Contour Velocity
Constrained
5 - Follow Contour Velocity
Unconstrained
Move 1 Move 2
Move 3
Move 1 Move 2
Move 3
Important Considerations
If you stop a move by using an MCS or by changing the speed to zero with an
MCCD during a blend and then resume the move by reprogramming the move
or by using another MCCD, it deviates from the path that displayed if the
move had not been stopped and resumed. The same phenomenon can occur if
the move is within the decel point of the start of the blend. In either case, the
deviation is most likely a slight deviation.

Velocity Profiles for Collinear Moves

Collinear moves are moves that lie on the same line in space. Their direction
can be the same or opposite. The velocity profiles for collinear moves can be
complex. This section provides you with examples and illustrations to help you
understand the velocity profiles for collinear moves programmed with MCLM
instructions.
Velocity Profiles for Collinear Moves with Termination Type 2 or 6
Figure 4 shows the velocity profile of two collinear moves by using a Command
Tolerance (2) termination type. The second MCLM instruction has a lower
velocity than the first MCLM instruction. When the first MCLM instruction
reaches its Command Tolerance point, the move is over and the .PC bit is set.
Rockwell Automation Publication MOTION-UM002E-EN-P - June 2016
Configure a Cartesian Coordinate System
Description
The instruction stays active until the axes get to the target position. At that point,
the instruction is complete and a queued MCLM or MCCM instruction can start.
• This termination type works best with tangential transitions. For example, use it
to go from a line to a circle, a circle to a line, or a circle to a circle.
• The axes follow the path.
• The length of the move determines the maximum speed of the axes. If the
moves are long enough, the axes do not decelerate between moves. If the moves
are too short, the axes decelerate between moves.
This termination type is similar to the contour velocity constrained. It has these
differences:
• Use this termination type to get a triangular velocity profile across several
moves. This reduces jerk.
• To avoid position overshoot at the end of the last move, you must calculate the
deceleration speed at each transition point during the deceleration-half of the
profile.
• You must also calculate the starting speed for each move in the deceleration half
of the profile.
Chapter 2
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