There is often a need for the motion-values of a Motion Law to start and end:
•at two different positions,
•with two equal velocities,
•and with zero accelerations.
The Flexible Polynomial motion law, that is preceded and followed by Constant-Velocity segments, is easily configured with these motion constraints.
However, there is the occasional request to add two motions, where one is Constant-Velocity and the other is a Traditional motion-law, such as a Mod-Sine.
This topic describes how you can do this with a Math FB.
Notes:
Care must be taken to use consistent units. The math in the Math FB uses SI units, e.g radians, or meters. You can edit the Motion FB to select its output data-type as Motion, Linear, or Rotary. However, when it is to be connected with wire to the input of a Math FB, you must select Linear or Rotary as the output data-type. Do NOT select “Motion” as the data-type in the Motion FB. |
A MechDesigner Model to add two Motions
The Function-Blocks and wires.
The image below shows wires that connect the output from two Motion FBs to the input of one Math FB.
The Motion FB
You muse edit the Motion FB to change Output Data-Type to Linear or Rotary.
Note: blue wires indicate the data-type is set to Linear.
Motion FB - Output Data-type
The Math FB
The equations for the three data-channels in the Math FB add the position ( p(0)+p(1) ), velocity ( v(0)+v(1) ), and acceleration ( a(0)+a(1) ) values of the two wires at the input to the Math FB.
The Output Data-Type from the Math FB is set to Linear Coordinates -
Note: the units of each data-channel are [Dis.], [Vel.], and [Acc.], which are Linear units.
Wires are connected from the Motion FBs and the Math FB to a Graph FB to give graph plots.
•The Green plot is the displacement of a Motion FB with an indexing motion that indexes by 100mm in one machine-cycle.
•The Blue plot is the displacement of a Motion FB with a Constant-Velocity motion that increases by 100mm in one machine cycle.
•The Orange plot is from the Math FB - it shows the addition of the other two - it increases by 200mm in 1 machine-cycle)
You can connect wires from the Math FB to a Motion-Dimension FB of Slider or a Rocker.
Personally, if I was to connect the output to a Rocker, I would edit the Motion FBs to edit the output data-types to Rotary and edit the Math FB to change the Output Data-Type to Rotary Coordinates.
