A self-calibrating robot based upon a virtual machine model of parallel kinematics

ABSTRACT

A delta-type parallel kinematics system for Additive Manufacturing has been created, which through a probing system can recognise its geometrical deviations from nominal and compensate for these in the driving inverse kinematic model of the machine. Novelty is that this model is derived from a virtual machine of the kinematics system, built on principles from geometrical metrology. Relevant mathematically non-trivial deviations to the ideal machine are identified and decomposed into elemental deviations. From these deviations, a routine is added to a physical machine tool, which allows it to recognise its own geometry by probing the vertical offset from tool point to the machine table, at positions in the horizontal plane. After automatic calibration the positioning error of the machine tool was reduced from an initial error after its assembly of ±170 µm to a calibrated error of ±3 µm. Excelling by speed, the calibration was executed in less than 3 min.

KEYWORDS:

• Parallel kinematics
• delta robot
• machine calibration
• virtual machine
• additive manufacturing

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCiD

David Bue Pedersen http://orcid.org/0000-0002-7013-7614

Hans Nørgaard Hansen http://orcid.org/0000-0001-7829-6962

Jakob Skov Nielsen http://orcid.org/0000-0002-3337-5429