Error analysis and auto-calibration for a Cartesian-guided tripod machine tool
Source: The International Journal of Advanced Manufacturing Technology, Volume 24, Numbers 11-12, December 2004 , pp. 899-909(11)
Abstract:This paper focuses on the error analysis and calibration methodologies for a parallel kinematic machine (PKM) called a Cartesian-guided tripod (CGT). The CGT volumetric error due to the geometric error, kinematic parameter error and nonlinear machine stiffness were studied. It is well known that the PKM nonlinear machine stiffness can produce significant volumetric errors from several tens to several hundreds of micrometres depending on the averaged value and deviation range for the machine stiffness. For most PKMs, joint level sensors are used to estimate the virtual Cartesian movements of the cutting tool. The nonlinear stiffness effect is not detected by this indirect metrology method and must be compensated for by a calibration methodology. A solution for the nonlinear stiffness effect implemented on the CGT involves using a passive Cartesian guiding/metrology leg that is independent of the driving legs to directly measure the Cartesian movement of the motion platform. Because the metrology loop of the Cartesian guiding/metrology leg is separated from the kinematic loops of the driving legs, the volumetric accuracy of the CGT is immunised against thermal errors and load deformations on the drive mechanisms. The passive Cartesian guiding/metrology leg is also used for the auto-calibration of the CGT kinematic parameters. The auto-calibration methodology and simulation results were studied and reported.
Document Type: Research article
Affiliations: 1: Precision Instrument Development Center, National Science Council, The Executive Yuan, 20 R&D Road VI, Hsinchu Science-Based Industrial Park, Hsinchu, 300, Taiwan, Email: email@example.com 2: Department of Mechanical Engineering, National Chung-Cheng University, 160, San-Hsing, Ming-Hsiung, Chia-Yi, 621, Taiwan, Email: firstname.lastname@example.org
Publication date: 2004-12-01