CV [Constant Velocity] Inverse Crank is similar to the Y–Inverse Sinusoid Motion-Law.
We urge you to use this motion-law in preference to the Y-Inverse Sinusoid.
This segment can be used more than once in one machine cycle, whereas the Y-Inverse-Sinusoid can be used only one time.
This segment is best explained by considering the X and Y motion components of a Point that is at the end of a rotating Part or Crank.
When the Crank rotates with constant angular velocity, the horizontal* motion of a Point at the end of the Crank is 'Simple-Harmonic-Motion' [ a Sine function]
When you apply the 'Constant-Velocity Inverse-Crank' segment to a Crank, the Point can be made to move with a constant linear horizontal* velocity for a portion of the crank's rotation. Thus, the crank can make a full rotation in each machine cycle, but it does not rotate at constant velocity.
* Actually, the motion of a Point on a Crank projected on to any line is Simple-Harmonic-Motion.
In the Segment Editor - see image below with Segment-Parameters
You can set the:
If you use the Flexible-Polynomial Segment before and after this segment, you can:
Segment-Parameters of the 'Constant-Velocity Inverse
Schematic of Crank (green) made to give a constant linear velocity between the Start Angle(4) and End Angle(5).
Segment Editor : Segment-Parameters
Note: These angles are on the Y-axis of the motion. They are NOT angles on the X-axis.
Minimum Velocity : the Angle of Minimum Velocity
The angle, after the Base-Value* of the Crank, at which the angular velocity of the Crank is a minimum. At all other angles, within the range of this segment, the angular velocity of the Crank is greater than the Minimum Velocity. In full, we call this parameter the Angle of Minimum Velocity.
The direction of the Constant-Velocity vector for Point on the Crank is projected onto an imaginary Line, which is perpendicular to the Angle of Minimum Velocity.
*The Base-Value is the parameter defined in the Motion-Dimension FB dialog for the Crank, not by the position of the end of the Previous-Segment.
Rel. Start : the Relative Angle before the Minimum Velocity Angle
The angle, before from the Angle of Minimum Velocity, at which the Constant-Velocity of Point starts.
Rel. End : the Relative Angle after the Minimum Velocity Angle
The angle, after the Angle of Minimum Velocity, at which the Constant-Velocity of Point ends.
Rel. Start is less than Min Vel, and Rel. End more than Min Vel, when the Crank rotates Counter-Clockwise.
Rel. Start is more than Min Vel, and Rel. End less than Min Vel, when the Crank rotates Clockwise.
The velocity of the Point when projected on to the Line is constant while the crank moves within the angular range of:
Start Angle = + -
End Angle = + +
The linear velocity and the length of the Constant-Velocity of the Point along the line depends on the:
Two CV Inverse-Velocity Segments in one Motion
An example motion with four segments and two CV Inverse Crank
With these Parameters:
The Velocity, Acceleration and Jerk at the end of the Previous-Segment are made to match Start of this Segment.
The Position at the end of the Previous-Segment (the end of the Motion) is usually = 'Position at Start + 360º'
This makes sure the Crank rotates one time for each for each Machine Cycle
With these Parameters