About Defining Machine Kinematics

The basic information regarding machine kinematics, that is, creating joints or commands for an assembled product and validating the inverse kinematics is described below.

Related Topics
Assembling Components to Build a Machine

Rules for Validating the Inverse Kinematics of the Machine

First asemble a product to build a machine, then create Commands or Joints to fix these products to the NC resource, using the Mechanical Design > Assembly Design workbench. Once this is done, you can validate the inverse kinematics of the machine. The rules below, if respected when building the NC resource, results in the automatic inverse kinematics solver being successful assigned.

  • Machines can be built as a single chain or as a maximum of two chains.

    For a machine that has two chains, if one chain contains the spindle then the other must have the table.

  • A minimum of one Prismatic connection is necessary to complete the NC resource kinematics definition.
  • The direction of the Prismatic command can be modeled along any direction and need not necessarily be along the three principal directions.
  • One of the following combinations of Rotary and Prismatic commands is necessary to complete the automatic assignment of inverse kinematics.
    1. Upto two Rotary commands without any Prismatic commands.

      Constraint: In case there are two Rotary commands, their axes of rotation must not be parallel.

    2. Upto three Prismatic commands without any Rotary commands.

      Constraint : In case of multiple Prismatic commands located on the same chain, their axes must not be parallel. The axes can be parallel only if the commands are located on separate chains.

    3. Three Prismatic and upto two Rotary commands.

      Same constraints applicable mentioned in point 1 and 2.

  • The axis of rotation of the Revolute connection can be along any direction in space.
  • There cannot be more than two Revolute connections on the NC resource.
  • The rotary joints can be located anywhere in a chain.
  • The mount points (workpiece and tool) must be defined for the automatic inverse kinematics solver to work correctly.
  • In case a machine consists of a chain in which a number of parts are joined together, then:
    • In a bifurcated chain, the mount points must be located on the last part of the chain which belongs to the last connection.
    • In a single-chain machine, the workpiece mount point can be located on the Fixed part, while the tool mount point can be located on the last joint part of the chain.
  • Inverse kinematics is also supported for a machine consisting of:
    • two Prismatic joints on one chain, and
    • one Rotary joint on the other chain, with the axis of rotation parallel to one of the prismatic joints

    The linear motion required along the normal to the two Prismatic commands is made by using the rotation of the part in the second chain.