The rotation accuracy evaluation methods for the high-speed spindle of machining robots
High speed machining robots is designed for a number of high speed machining applications, the precision of which is one of the essential features. To increase precision of the robots, the study of accuracy evaluation methods is important. First, according to the demands for robots, key information of high-speed spindle of machining robots is determined, then it will be extracted by sensors and data acquisition card. Second, four different evaluating methods are introduced to assess the rotation accuracy, the results respectively solved by which are compared in detail. Furthermore, the particle swarm algorithm based on simulated annealing (SA-PSO) is introduced and theory analysis about the impact of simulated annealing factor is carried on to provide basis for giving the parameter better value. Finally, through the contrast between the evaluation results obtained by the proposed method and other optimization methods, the availability and precision of the SA-PSO is verified.
A multi-orientation error separation technique for spindle metrology of miniature ultra-high-speed spindles
Abstract This paper presents a multi-orientation error separation technique to remove the artifact form error from the radial measurements to obtain the radial spindle error motions of miniature ultra-high-speed (UHS) spindles. Unlike the existing approaches, the present technique neither relies on high-accuracy fixtures, nor necessitates measurements from specific orientations of the artifact. Rather, the spindle error motions are measured from a set of arbitrary artifact orientations using laser Doppler vibrometry (LDV). The angle of each artifact-setup orientation with respect to the spindle is determined with high precision through reflectivity measurement of the marks made on both the artifact and the spindle using another LDV. Although the presented approach can be applied by using different sensors (e.g., capacitance probes), we demonstrate the approach using LDVs. With the displacement measurement direction fixed, measurements are conducted from both LDVs for multiple orientations of the artifact. Using the unique implementation scheme developed in this paper, data from these orientations are post-processed to compute the artifact form error and further remove it from the radial motion measurements to obtain the synchronous radial spindle error motions. A thorough experimental evaluation is presented to quantify both the repeatability of the measured artifact form errors as well as the bandwidth of error separation for various number of artifact orientations. The spindle error motions measured from both the sphere and stem portions of a custom fabricated sphere-on-stem artifact mounted on a typical miniature UHS spindle, are seen to be similar in shape and within 5 nm in magnitude across the revolution, thus demonstrating the effectiveness of the technique. Using this technique, spindle error motions at ultra-high speeds up to 150 krpm were successfully quantified. Although the implementation scheme is demonstrated for miniature UHS spindles, it is readily applicable for error separation on macro-scale spindles without the need for any high-precision fixtures and precise setting of angles.
Circularity error evaluation: Theory and algorithm
Many procedures for the evaluation of circularity error based on different criteria have been developed. The procedures that are based on the minimum radial separation criterion are either too complex or lack an algorithmic approach to find optimal solution. This paper presents an optimization-based technique to find the value of circularity error based on the minimum radial separation criterion. The problem is formulated as a nonlinear optimization problem. Based on the developed necessary and sufficient conditions a generalized nonlinear optimization procedure is presented. The performance of the developed procedure is analyzed for different size problems generated using a simulation program. Results indicate that the procedure is accurate and very efficient in solving large size real life problems.