An Integrated Geometric and Hysteretic Error Model of a Three Axis Machine Tool and Its Identification With a 3D Telescoping Ball-Bar

Abstract

The ball-bar instrument is used to estimate a maximum number of hysteretic error sources. Machine error parameters include inter- and intra-axis errors as well as hysteresis effects. An error model containing cubic polynomial functions and modified qualitative variables, for hysteresis modeling, is proposed to identify such errors of the three nominally orthogonal linear axes machine. Such model has a total of 90 coefficients, not all of which being necessary. A numerical analysis is conducted to select a minimal but complete non-confounded set of error coefficients. Four different ball-bar test strategies to estimate the model coefficients are simulated and compared. The first one consists of circular trajectories on the primary planes XY, YZ, and XZ and the others use the XY plane, as an equator, and either four, five, or nine meridians. It is concluded that the five-meridian strategy can estimate the additional eight error coefficients: ECZ1, ECZ2, ECZ3, ECZb, EZY3, EZX3, ECX3, and ECXb. The Jacobian condition number is improved by increasing the number of meridians to 5. Further increasing the number of meridians from five to nine improves neither the number of estimable coefficients nor the conditioning, and so as it increases, the test time it was dismissed.

Tool Positioning Error Minimization during Robotic Milling Based on the Genetic Algorithm Technique

“…The combination of the obtained robot trajectories (Figure 13) and the roughness profiles (Figure 16) on a CAD model reveals the surface condition depicted in Figures (19,20). Figure 19 shows a notable machining path disturbance while the machined surface is relatively correct (figure 20).…”

“…Other authors use the QC20-W RENISHAW telescopic ball-bar with Bluetooth wireless technology, which was developed to evaluate the accuracy of machines in which the circular motion is generated by the simultaneous movement of two orthogonal linear axes, as in machine tools [20], and is limited for serial robots [21].…”