Assume we have a 6DOF manipulator, take UR5 as an example. Does adding a linear rail, on which the robot sits, add a 7th DOF to the system, making it equivalent to a 7DOF manipulator? Any caveats?


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You are correct. Adding an external axis results in 6+1=7 DOF.

Caveats...the same as for any redundant system

  • solving IK requires a more complex approach (and then path/trajectory planning also)
  • precision/repeatability/accuracy can be affected if the external axis has a worse precision/repeatability//accuracy
  • same goes for dynamic performance
  • technical compatibility issues might arise (depending on how the external axis is controlled and what communication protocols are available at the robot controller)

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