Motion-Laws [also called 'Cam-Laws'].
A Motion-Law specifies, with a mathematical expression, how an 'output variable' changes as a function of an 'input variable'.
The mathematical expression calculates displacement, velocity, acceleration and jerk values. All motion-derivatives are exact, evaluated motion-values.
The user does not need to know any mathematics. We plot the motion-laws.
In the Motion-Law Selector, we list the Motion-Laws alphabetically [English Language]
In this topic, we can separate the motion-laws into three broad groups.
Traditional Motion-Laws
Traditional Motion-Laws [sometime named Standard Motion-Laws] have been used for many years in cam mechanisms as 'Rise' and 'Return' segments, usually between two 'Dwell' Segments.
Their main disadvantage is that you cannot usually edit their velocity, acceleration and jerk values at their start and end.
The Traditional Motion-Laws are based on function that are:
| • | Trigonometric / Harmonic |
or
Traditional Motion-Laws:
| 3. | Cubic - Polynomial Function |
| 6. | Dwell - Polynomial Function |
| 14. | Ramp - Trigonometric Function |
| 16. | Sine-Constant-Cosine + SCCA with Constant-Velocity 20%, 33%, 50%, 66%.... - Trigonometric Function |
Also, use the 'Triple Harmonic' Controls in the Segment-Editor to give:
Throw Motion Laws [Symmetrical & Asymmetrical]
A Throw motion-law is a rise segment followed immediately by a return segment - no dwell between.
The Throw rise and return can be imagined as the motion of a ball thrown up in the air or the swing of a pendulum at the they change directions.
With the acceleration becomes zero at the transition from rise to return. With a Throw, the Acceleration motion-value does not return to zero. This makes the throw a so-called 'Quick Return'.
We construct Throw motion-laws with two Flexible Polynomial segments. Each segment can have the same or different motion-periods [time-duration].
The of 25 is greater than other motion laws. This means that backlash is traversed quickly to give a large velocity impact.
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Special Motion-Laws
These meet the needs of specific applications.
| 26. | Y–Inverse-Sinusoid : when applied to a the motion of a 'crank', it gives a constant linear velocity at the tip of a crank. Limited to one segment per crank rotation. |
| 27. | Crank-Constant-Velocity : an enhancement of Y-Inverse-Sinusoid, this motion-law can be applied more than one segment in a motion. |
| 29. | Ramp - a VERY useful motion law. |
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Imported Motion Data
When you select these 'Motion-Laws', you can import your own motion-values.
The Z-Raw-Data is the easiest to use, as it imports your data values directly.
The Position-List scales all of the values you import. The scale is in proportion to the difference between the start and end positions that you specify with the Blend-Point Editor - it is compatible with Camlinks.
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When to use the Flexible Polynomial OR a Traditional Motion-Law?
The Flexible Polynomial is the 'default' motion-law. It is very powerful tool. We strongly recommend that you learn how to use it effectively and efficiently.
Traditional Motion-Laws have advantages in some circumstances, especially for simple Rise-Dwell-Return motions.
Thus, we recommend, that you make the segments:
| • | All Flexible-Polynomials - most powerful and flexible motion design possibilities |
- or -
| • | All Traditional Motion-Laws - 'standard' motion-design requirements |
- or -
| • | A mixture of Flexible-Polynomial and Traditional Motion-Laws - least preferred. |
The Motion-Laws available in MotionDesigner exceed the German Technical VDI-guidelines 2143 Papers (Part) 1 and 2. Also bare in mind, that the motion at a cam-follower or servomotor is usually found by MechDesigner with Inverse-Kinematics. In this case, the motion at the cam-follower or servomotor will not be the same as the motion of the Motion-Part.
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