Calibration of a hexapod machine tool using a redundant leg

Amit J. Patel, Kornel F. Ehmann

Research output: Contribution to journalArticlepeer-review

101 Scopus citations


Parallel configurations are recently being applied to the machine tool with the hopes of greater rigidity, stability, and accuracy than conventional multi-axis structures allow. However, the many calibration methods presently available for serial machine tools are not applicable to hexapod type structures. A calibration method is presented that uses a ball-bar or other simple length measuring device to act as an `extra leg,' allowing calibration of the hexapod's true kinematic parameters. This method utilizes a total least squares minimization, does not require any special hexapod configuration or difficult six degree of freedom pose measurements, and is effective with as few as one additional length sensor. Selection of calibration pose sets is briefly discussed, as well as the influence of measurement noise on calibration accuracy. Simulations show the potential for this algorithm to significantly reduce errors to the point where machining errors are within 5-10 times the measurement errors.

Original languageEnglish (US)
Pages (from-to)489-512
Number of pages24
JournalInternational Journal of Machine Tools and Manufacture
Issue number4
StatePublished - Mar 2000

ASJC Scopus subject areas

  • Mechanical Engineering
  • Industrial and Manufacturing Engineering


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