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Bipod Calculational Motor

Two-legs table calculational motor transforming two translations into a rotation and a translation.

One or more rotation center can be defined.

Conventions for bipod calculations

A direct coordiante system (x,y,z) is used:

                ^
                | Z axis
                |
    X axis      |
      <----------
               /
              /
             / Y axis
            /
            v

The rotations are named rotx, roty and rotz around respectively the X, Y and Z axes with counterclockwise positive value.

Parameters relative to legs are following the same convention:

  • coordinates of “lega” are named: “ax”, “ay”
  • coordinates of “legb” are named: “bx”, “by”
  • …

The calculation takes into account the “unit” defined for each real or calculated motors. If the “unit” field is missing, the universal units are used: meters (m) for distance, radians (rad) for angles.

  • the 2 legs are tagged lega and legb
  • the height of the table is tagged trans
  • X-axis is the axis passing through lega and legb, positive direction: from lega to legb
  • The rotation is around Y-axis, perpendicular to the [lega-legb] axis (X-axis)
  • the rotation is tagged ry
  • C is the center of rotation and its height is represented by the position of the rz axis
  • C is the origin of the X/Y/Z coordinates system
  • ax is the coordinate of lega in the X/Y/Z coordinates system
  • bx is the coordinate of legb in the X/Y/Z coordinates system

Example of yml file with 2 centers.

Note

At least one center is mandatory.

  • center_id = inside:
  • C is inside of the legs
  • ax is a negative value in meter
  • bx is a positive value in meter
                   Z-axis
                        ^
                        |
                  ______|______________
                 /      |             /
                /       |...ax..>|   /
     X axis    /        |        |  /     X axis
     <--------/-.-------C--------.-/----<------
             /  |<.bx../         |/
            /   |     /          |
           /____|____/__________/|
                |   /            |
                |  v Y-axis      |
                |                |
              legb             lega
  • center_id = outside
  • C is outside of the legs
  • ax is a positive value in meter
  • bx is a positive value in meter
                                        Z-axis
                                          ^
                                          |
                  _____________________   |
                 /                    /   |
                /<.......bx...............|
     X axis    /|                   /     |    X axis
     <--------/-.----------------.-/------C----------
             /  |                |/      /
            /   |                |<.ax../
           /____|_______________/|     /
                |                |    /
                |                |   v Y axis
                |                |
              legb             lega

- plugin: emotion
  module: bipod
  class: bipod
  name: btable
  centers:
    - center_id: inside
      ax: -0.3
      bx: 0.3
    - center_id: outside
      ax: 0.3
      bx: 0.9
  axes:
    - name: $sim_btz1
      tags: real lega
    - name: $sim_btz2
      tags: real legb
    - name: sim_btz
      tags: tz
      unit: mm
    - name: sim_btr
      tags: ry
      unit: deg

Warning

Take care to specify unit otherwise meters are used.