Choose a Termination Type

The termination type determines when the instruction is complete. It also determines how the instruction blends its path into the queued MCLM or MCCM instruction, if there is one.
To choose a termination type:
If you want the axes to (vector speeds)
And you want the instruction to complete when
Then use this Termination Type
stop between moves.
Speed TT 0
The following occurs:
  • Command position equals target position.
  • The vector distance between the target and actual positions is less than or equal to the Actual Position Tolerance of the Coordinate System.
0 - Actual Tolerance
The command position equals the target position.
1 - No Settle
keep the speed constant
except
 between moves.
Speed TT 2
The command position gets within the Command Position Tolerance of the coordinate system.
2 - Command Tolerance
The axes get to the point at which they must decelerate at the deceleration rate.
3 - No Decel
transition into or out of a circle without stopping.
Speed TT 4
4 - Follow Contour Velocity Constrained
accelerate or decelerate across multiple moves.
Speed TT 5
5 - Follow Contour Velocity Unconstrained
use a specified Command Tolerance
Speed TT 2
The command position gets within the Command Position Tolerance of the coordinate system.
6 - Command Tolerance Programmed
To make sure that this is the right choice for you:
  • Review these tables.
    Termination Type
    Example Path
    Description
    0 - Actual Tolerance
    PositionTT0 (2)
    The instruction stays active until both of these happen:
    • Command position equals target position.
    • The vector distance between the target and actual positions is less than or equal to the Actual Position Tolerance of the coordinate system.
    At that point, the instruction is complete and a queued MCLM or MCCM instruction can start.
    Important:
     Make sure that you set the Actual Tolerance to a value that your axes can reach. Otherwise the instruction stays in process.
    1 - No Settle
    PositionTT0 (2)
    The instruction stays active until the command position equals the target position. At that point, the instruction is complete and a queued MCLM or MCCM instruction can start.
    2, 6 - Command Tolerance
    PositionTT2
    The instruction stays active until the command position gets within the Command Tolerance of the Coordinate System. At that point, the instruction is complete and a queued MCLM or MCCM instruction can start.
    If you don’t have a queued MCLM or MCCM instruction, the axes stop at the target position.
The
Logix Designer
 application compares
To the
And uses the
For the
100% of the configured length of the first instruction using a Command Tolerance termination type
configured Command Tolerance for the Coordinate System
shorter of the two lengths
command Tolerance length used for the
first
 instruction
100% of the configured length of the last move instruction using a Command Tolerance termination type
configured Command Tolerance for the Coordinate System
shorter of the two lengths
command Tolerance length used for the
next to last
 instruction
50% of each of the lengths of all other move instructions
configured Command Tolerance for the Coordinate System
shorter of the two lengths
command Tolerance length used for
each individual
 instruction
Termination Type
Example Path
Description
3 - No Decel
PositionTT3
The instruction stays active until the axes get to the deceleration point. At that point, the instruction is complete and a queued MCLM or MCCM instruction can start.
  • The deceleration point depends on whether you use a trapezoidal or S-curve profile.
  • If you don’t have a queued MCLM or MCCM instruction, the axes stop at the target position.
4 - Follow Contour Velocity Constrained
PositionTT4 (2)
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 will not decelerate between moves. If the moves are too short, the axes decelerate between moves.
5 - Follow Contour Velocity Unconstrained
PositionTT4 (2)
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.
Important Considerations
If you stop a move (that is, using an MCS or by changing the speed to zero with an MCCD) during a blend and then resume the move (that is, by reprogramming the move or by using another MCCD), it will deviate from the path that you would have seen 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 will most likely be a slight deviation.
Velocity Profiles for Collinear Moves
Collinear moves are those 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
This illustration shows the velocity profile of two collinear moves 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.
Velocity Profile of Two Collinear Moves When the Second Move has a Lower Velocity than the First Move and Termination Type 2 or 6 is Used
velprotwocoll1
This illustration shows the velocity profile of two collinear moves using a Command Tolerance (2) termination type. The second MCLM instruction has a
higher
 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.
Velocity Profile of Two Collinear Moves When the Second Move has a Higher Velocity than the First Move and Termination Type 2 or 6 is Used
velprotwocoll2
Velocity Profiles for Collinear Moves with Termination Types 3, 4, or 5
This illustration shows a velocity profile of two collinear moves. The second MCLM instruction has a
lower
 velocity than the first MCLM instruction and one of these termination types are used:
  • No Decel (3)
  • Follow Contour Velocity Constrained (4)
  • Follow Contour Velocity Unconstrained (5)
When the first MCLM instruction reaches the deceleration point, it decelerates to the programmed velocity of the second move. The first move is over and the .PC bit is set.
Velocity Profile of Two Collinear Moves When the Second Move has a Lower Velocity than the First Move and Termination Type 3, 4, or 5 is Used
velprotwocoll3
This illustration shows a velocity profile of two collinear moves. The second MCLM instruction has a
higher
 velocity than the first MCLM instruction and one of these termination types are used:
  • No Decel (3)
  • Follow Contour Velocity Constrained (4)
  • Follow Contour Velocity Unconstrained (5)
The .PC bit is set when the first move reaches its programmed endpoint.
Velocity Profile of Two Collinear Moves When the Second Move has a Higher Velocity than the First Move and Termination Type 3, 4, or 5 is Used
velprotwocoll4
Symmetric Profiles
Profile paths are symmetric for all motion profiles.
Programming the velocity, acceleration, and deceleration values symmetrically in the forward and reverse directions generates the same path from point A to point C in the forward direction, as from point C to point A in the reverse direction.
While this concept is most easily shown in a two-instruction sequence, it applies to instruction sequences of any length provided that they are programmed symmetrically.
Refer to this Example of a Symmetric Profile for more details.
ExSymProf
IMPORTANT:
We recommend that you terminate any sequence of moves by either Termination Type 0 or 1, that is, TT0 or TT1.
To guarantee that your trajectory is symmetric, you must terminate any sequence of moves by either Termination Types 0 or 1. You should also use a Termination Type of 0 or 1 at the Reversal Point of a profile that moves back on itself.
TermTyp0or1
Using a TT2, TT3, TT4, TT5, ot TT6 as the last move in a profile (or the reversal point) is safe. However, the resulting trajectory from A to B may not always be the same as that from B to A. Explicit termination of the sequence of moves helps the controller to optimize the velocity profile, reduce the CPU load, and guarantee a symmetric profile.
How To Get a Triangular Velocity Profile
If you want to program a pick and place action in four moves, minimize the Jerk rate, and use a triangular velocity profile.
TriVelProf
Then, use termination type 5. The other termination types may not let you get to the speed you want.
Termination Types 2, 3, 4, or 6
TermTyp23or4
The length of each move determines its maximum speed. As a result, the axes will not reach a speed that causes them to overshoot the target position during deceleration.
Termination Type 5
TermTyp5
The axes accelerate to the speed that you want. You must calculate the starting speed for each move in the deceleration-half of the profile.
Blending Moves at Different Speeds
You can blend MCLM and MCCM instructions where the vector speed of the second instruction is different from the vector speed of the first instruction.
If the next move is
And the Termination Type of the first move is
Then
Slower
2 - Command Tolerance
3 - No Decel
4 - Contour Velocity Constrained
5 - Contour Velocity Unconstrained
6 - Command Tolerance Programmed
bldmve1
Faster
2 - Command Tolerance
3 - No Decel
6 - Command Tolerance Programmed
bldmve2
4 - Contour Velocity Constrained
5 - Contour Velocity Unconstrained
bldmve3
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