title: Improvement of accuracy in a high-capacity, six degree-of-freedom load cell: application to robotic testing of musculoskeletal joints.
abstract: This study investigated a previously unaccounted for source of error in a high-capacity, six degree-of-freedom load cell used in multi-degree-of-freedom robotic testing of musculoskeletal joints, an application requiring a load cell with high accuracy in addition to high load capacity. A method of calibration is presented for reducing the error caused by changes in universal force-moment sensor (UFS) orientation within a gravitational field. Uncorrected, this error can exceed a magnitude of 1% of the full-scale load capacity-the manufacturer-stated accuracy of the UFS. Implementation of the calibration protocol reduced this error by approximately 75% for a variety of loading conditions. This improvement in load cell accuracy (while maintaining full load capacity) should improve both the measurement and control of specimen kinetics by robotic/UFS and other biomechanical testing systems.
authors.affiliation: Musculoskeletal Research Center, Department of Orthopaedic Surgery, University of Pittsburgh, PA 15213, USA. larss+@pitt.edu
authors.forename: L G
authors.initials: LG
authors.lastname: Gilbertson
authors.forename: T C
authors.initials: TC
authors.lastname: Doehring
authors.forename: G A
authors.initials: GA
authors.lastname: Livesay
authors.forename: T W
authors.initials: TW
authors.lastname: Rudy
authors.forename: J D
authors.initials: JD
authors.lastname: Kang
authors.forename: S L
authors.initials: SL
authors.lastname: Woo
mesh_terms: D015982:Bias; D002138:Calibration; D019245:Compressive Strength; D006801:Humans; D007596:Joints / Q000502:physiology*; D016014:Linear Models; D017711:Nonlinear Dynamics; D015203:Reproducibility of Results; D012371:Robotics / Q000379:methods* / Q000592:standards*; D016474:Weight-Bearing