In this paper, eddy current sensors and thermocouple sensors were employed to measure the thermal field and thermal deformation of a spindle of a telescopic CNC boring-milling machine tool, respectively. A linear regr...In this paper, eddy current sensors and thermocouple sensors were employed to measure the thermal field and thermal deformation of a spindle of a telescopic CNC boring-milling machine tool, respectively. A linear regression method was proposed to establish the thermal error model. Furthermore, two compensation methods were implemented based on the SIEMENS 840D system by using the feed shaft of z direction and telescopic spindle respectively. Experimental results showed that the thermal error could be reduced by 73.79% when using the second compensation method, and the thermal error could be eliminated by using the two compensation methods effectively.展开更多
Error compensation is an effective method to improve the accuracy of NC machine tool.The compensation results are greatly affected by the error modeling and error measurement,so how to establish an accurate error mode...Error compensation is an effective method to improve the accuracy of NC machine tool.The compensation results are greatly affected by the error modeling and error measurement,so how to establish an accurate error model and accurately detect the geometric errors of machine tool are particularly important.In the paper,the volumetric error model of a multi-axis NC machine tool is established based on the multi-body system theory.The relative position deviations between the rotary axis and linear axis of the machine tool are considered in the modeling.To achieve quick and accurate detection,a laser tracker is based on the multi-station and time-sharing measurement principle to detect the geometric errors of machine tool,and each error of linear axis and rotary axis can be identified by this method.With the error model,error compensation can be carried out by modifying the machining process(G code),and the machining accuracy can be improved with the new G code.Experiment results show that the motion errors of a milling machine are significantly reduced after compensation,which verifies the effectiveness of compensation method.展开更多
Contour following is one of the most important issues faced by many computer-numerical-control(CNC) machine tools to achieve high machining precision. This paper presents a new real-time error compensation method aimi...Contour following is one of the most important issues faced by many computer-numerical-control(CNC) machine tools to achieve high machining precision. This paper presents a new real-time error compensation method aiming at reducing the contouring error caused by facts such as servo lag and dynamics mismatch in parametric curved contour-following tasks. Due to the lack of high-precision contouring-error estimation method for free-form parametric curved toolpath, the error can hardly be compensated effectively. Therefore, an adaptive accurate contouring-error estimation algorithm is proposed first, where a tangential-error backstepping method based on Taylor's expansion is developed to rapidly find the closest point on the parametric curve to the actual motion position. On this foundation, the contouring error is compensated using a proposed nonlinear variable-gain compensation method, where the compensation gain is obtained according to not only the contouring-error magnitude but also its direction variation. The stability of the system after compensation is analyzed afterwards according to the Jury stability criterion.By design of the compensator in accordance with the presented contouring-error compensation method as well as the stability analyzation result, the balance between the response speed and the contour control stability can be effectively made. Experimental tests demonstrate the feasibility of the presented methods in both contouring-error estimation and contour-accuracy improvement.Contributions of this research are significant for enhancing the contour-following performance of the CNC machine tools.展开更多
文摘In this paper, eddy current sensors and thermocouple sensors were employed to measure the thermal field and thermal deformation of a spindle of a telescopic CNC boring-milling machine tool, respectively. A linear regression method was proposed to establish the thermal error model. Furthermore, two compensation methods were implemented based on the SIEMENS 840D system by using the feed shaft of z direction and telescopic spindle respectively. Experimental results showed that the thermal error could be reduced by 73.79% when using the second compensation method, and the thermal error could be eliminated by using the two compensation methods effectively.
基金supported by the National Natural Science Foundation of China (Grant No.51175415)the China Technology Major Project(Grant No.2011ZX04016-101)
文摘Error compensation is an effective method to improve the accuracy of NC machine tool.The compensation results are greatly affected by the error modeling and error measurement,so how to establish an accurate error model and accurately detect the geometric errors of machine tool are particularly important.In the paper,the volumetric error model of a multi-axis NC machine tool is established based on the multi-body system theory.The relative position deviations between the rotary axis and linear axis of the machine tool are considered in the modeling.To achieve quick and accurate detection,a laser tracker is based on the multi-station and time-sharing measurement principle to detect the geometric errors of machine tool,and each error of linear axis and rotary axis can be identified by this method.With the error model,error compensation can be carried out by modifying the machining process(G code),and the machining accuracy can be improved with the new G code.Experiment results show that the motion errors of a milling machine are significantly reduced after compensation,which verifies the effectiveness of compensation method.
基金the National Natural Science Foundation of China(Grant Nos 51515081 and 51675081)National Science and Tech-nology Major Project of China(Grant No 2016ZX04001-002)+2 种基金Innovation Project for Supporting High-level Talent in Dalian(Grant No 2016RQ012)Science Fund for Creative Research Groups(Grant No 51621064)the Fundamental Research Funds for the Central Universities(Grant NoDUT17LAB13)
文摘Contour following is one of the most important issues faced by many computer-numerical-control(CNC) machine tools to achieve high machining precision. This paper presents a new real-time error compensation method aiming at reducing the contouring error caused by facts such as servo lag and dynamics mismatch in parametric curved contour-following tasks. Due to the lack of high-precision contouring-error estimation method for free-form parametric curved toolpath, the error can hardly be compensated effectively. Therefore, an adaptive accurate contouring-error estimation algorithm is proposed first, where a tangential-error backstepping method based on Taylor's expansion is developed to rapidly find the closest point on the parametric curve to the actual motion position. On this foundation, the contouring error is compensated using a proposed nonlinear variable-gain compensation method, where the compensation gain is obtained according to not only the contouring-error magnitude but also its direction variation. The stability of the system after compensation is analyzed afterwards according to the Jury stability criterion.By design of the compensator in accordance with the presented contouring-error compensation method as well as the stability analyzation result, the balance between the response speed and the contour control stability can be effectively made. Experimental tests demonstrate the feasibility of the presented methods in both contouring-error estimation and contour-accuracy improvement.Contributions of this research are significant for enhancing the contour-following performance of the CNC machine tools.
