共查询到20条相似文献,搜索用时 31 毫秒
1.
Jianfeng Zhou Yuwen Sun Dongming Guo 《The International Journal of Advanced Manufacturing Technology》2014,71(9-12):1873-1882
A good adaptive feedrate will be helpful for improving machining accuracy and efficiency, as well as avoiding the excess of the machine’s physical capabilities and feed fluctuations during machining. Therefore, it is highly desirable to consider the constraints of geometric error, cutting performance, and drive constraints in the feedrate scheduling of the parametric curve interpolator for five-axis computer numerical control machining. In this paper, a novel multiconstraints feedrate scheduling method is proposed for the parametric curve interpolator in five-axis machining. In the method, the feed optimization model is first built with the constraints of geometric error, the maximum feedrate and acceleration of cutter tip, and the maximum feedrate and acceleration of five-drive axes. Then, the relations between each constraint and the cutter tip feedrate are derived by means of near arc length parameterization. After that, a linear programming algorithm is applied to obtain the optimal feed profile on the sampling positions of the given tool path. Finally, illustrated examples are given to validate the feasibility and applicability of the proposed feedrate scheduling method. The comparison results show that the proposed method has an ability of the simultaneous guarantees of geometric accuracy, cutting performance, and drive characters of machine tools. 相似文献
2.
Five-axis machining plays an important role in manufacturing by dint of its high efficiency and accuracy. While two rotation axes benefit the flexibility of machining, it also brings limitations and challenges. In order to further balance machining precision and efficiency, an improved feedrate scheduling method is presented considering geometric error and kinematic constraints for the Non Uniform Rational B-Spline (NURBS) interpolation in five-axis machining. A simplification method is proposed to calculate the geometric error which describes the deviation between the ideal tool path and the real tool path induced by the non-linear movement. A linear relation between geometric error and feedrate is built to limit the feedrate. The constraints determined by single axis kinematic performance and tangential kinematic performance are also considered. Under these constraints, a constrained feedrate profile is determined. Aiming to get more constant feedrate in the difficult-to-machine areas, this work proposes a scheduling method which combines morphological filtering and S-shape acceleration/deceleration (acc/dec) mode. Simulations and experiments are performed to compare the proposed feedrate scheduling method with two previous feedrate scheduling method and the results prove that the proposed feedrate scheduling method is reliable and effective. 相似文献
3.
A cutter orientation modification method for five-axis ball-end machining with kinematic constraints
Yuwen Sun Yurong Bao Kaixuan Kang Dongming Guo 《The International Journal of Advanced Manufacturing Technology》2013,67(9-12):2863-2874
Cutter orientation modification with kinematic constraints is very necessary and effective for five-axis machining especially machining at high speed. It is very helpful for achieving a smooth cutter motion and keeping the process steady. Therefore, a cutter orientation adjustment method is proposed to obtain an optimized tool path which makes best use of the kinematic characteristics of angular feed for five-axis machining. For the given five-axis cutter location path and the feed profile of cutter tip point both expressed by b-spline formats with the same parameterization, the analytic relations of angular feed, angular feed acceleration, and jerk with respect to the geometric and tangential feed parameters of the cutter tip trajectory are first derived. Then, the conditional inequalities of these kinematic constraints used for orientation adjustment are built. Subsequently, the determination method of feasible cutter orientation and detailed algorithm of orientation adjustment are given. Finally, illustrated examples are conducted to validate the proposed orientation adjustment method. The results show that the developed method is effective and can be applied to optimize geometrically complex five-axis tool path by taking the angular feed, angular feed acceleration, and jerk into account. 相似文献
4.
Cunliang Yan Daoshan Du Congxin Li 《The International Journal of Advanced Manufacturing Technology》2007,35(1-2):169-178
The interpolator is the key part of a CNC system, which has strong effect on machining accuracy, tool motion smoothness, and
machining efficiency. In this paper, a real-time adaptive interpolator is developed for non-uniform rational B-spline curves
(NURBS) interpolation while considering the maximum acceleration/deceleration of the machine tool. In this proposed interpolator,
both constant feedrate and high accuracy are achieved while the inconsistency of feedrate is dramatically reduced as well.
In order to deal with the acceleration/deceleration around the feedrate-sensitive sharp corners, a look-ahead function is
introduced to detect and adjust the feedrate adaptively. Furthermore, a parameter compensation scheme is proposed to eliminate
the parametric truncation error which has been analyzed by several researchers but still not incorporated into any real-time
interpolator so far. A case study was conducted to evaluate the feasibility of the developed interpolator. 相似文献
5.
X. Zhiming C. Jincheng F. Zhengjin 《The International Journal of Advanced Manufacturing Technology》2002,20(4):270-276
This paper presents a real-time interpolation algorithm for NURBS curves. In contrast to the existing linear and circular
interpolators, the proposed interpolator can maintain small contour errors and feedrate fluctuations. Feedrate components,
acceleration components and the servomotor driving force for each axis are precalculated from the given curve shape and themachine
tool dynamic properties. As a sudden change in the geometrical properties of the tool path can increase contour errors and
cause a sudden change of driving force of each servomotor, a new strategy of variable feedrate machining based on the geometrical
properties of tool path is suggested. Real-time performance measurement of this interpolator is performed to demonstrate its
practical feasibility. 相似文献
6.
根据计算机数字控制系统的实际性能和非均匀有理B样条曲线的几何特性,设计了一种能够实现加速度平滑过渡的高效非均匀有理B样条曲线插补器。首先,该插补器利用快速插补计算模拟实际加工过程,找到加速度不连续的点;然后,采用S曲线加减速方法向后逆求减速点,并通过约束速度和加速度的方法,预估S曲线加减速第三阶段起点,不仅提高了所求减速点位置的精度,还实现了减速点处加速度的连续性。仿真结果表明,该插补器能在保证加工精度的前提下,以较高效率实现加速度的平滑过渡。 相似文献
7.
8.
Daoshan Du Yadong Liu Cunliang Yan Congxin Li 《The International Journal of Advanced Manufacturing Technology》2007,32(9-10):999-1008
In this paper, an adaptive parametric curve interpolator with a real-time look-ahead function is developed for non-uniform rational B-spline curves (NURBS) interpolation, which considers the maximum acceleration/deceleration of the machine tool. In the proposed interpolator, both constant feedrate and high accuracy are achieved while the inconsistency of feedrate is reduced dramatically as well. In order to deal with the acceleration/deceleration around the feedrate sensitive corners, a look-ahead function is introduced to detect and adjust the feedrate adaptively. Two cases were respectively studied to evaluate the feasibility of the developed interpolator: one is for feedrate sensitive arc corner; the other is for feedrate sensitive sharp corner. 相似文献
9.
In-Hugh Choi Min-Yang Yang Won-Pyo Hong Tae-Sung Jung 《The International Journal of Advanced Manufacturing Technology》2005,25(3-4):325-333
Finish machining of a curved surface is often carried out by an NC system with curve interpolation in the field. This function, called a NURBS interpolation, adopts a feedrate optimizing strategy based on both the geometrical information of the curved path and dynamic properties such as the curvature of the curve, the allowable acceleration and the time constant. However, in the case of a finish cut using a ball-end mill, the curve interpolator needs to take the machining process into account for improved surface roughness, while reducing the polishing time. This surface roughness on high-speed machining is theoretically defined by the feed per tooth and the pickfeed at the given radius of the tool. In this study, the effect of low machinability at the bottom of a tool on surface roughness is also considered. A curve interpolation algorithm is proposed for generating particular feedrate commands that are able to control the roughness of a curved surface. The simulation of the machined surface by the proposed algorithm was carried out, and experimental results are presented. A feedrate scheme that depends on the inclination angle has important potential application in part finishes consistent with prescribed surface roughness. The results show that the proposed algorithm is potentially useful for roughness-controlled machining of curved surface products. 相似文献
10.
M. Sekar V. N. Narayanan Seung-Han Yang 《The International Journal of Advanced Manufacturing Technology》2008,37(5-6):545-552
A method for obtaining smooth, jerk bounded feedrate profile in high speed machining has been developed. This study proposes
a NURBS interpolator based on adaptive feedrate control with a well developed lookahead algorithm. It is found that the values
of the feedrate of the down stream sharp corner have profound effect on the feedrate of the upstream sharp corners causing
a ripple effect (RE). By using a windowing scheme the feedrate profile obtained after lookahead is re-interpolated to obtain
a continuous velocity and acceleration profiles which reduces the jerk related problems. This is compared with the adaptive
NURBS interpolator to show the effectiveness of the proposed method. Simulation results indicate that the consideration of
ripple effect is important in avoiding jerk and thereby increasing the machining accuracy. 相似文献
11.
Jiangang Li Tinghua Zhang Zexiang Li 《The International Journal of Advanced Manufacturing Technology》2012,63(5-8):719-729
As a key technique in CNC machining, nonuniform rational B-spline (NURBS) interpolator has been proposed to overcome the drawbacks caused by linear and circular interpolator, such as large data size, velocity discontinuity, shocks or variations in mechanical systems, and low machining efficiency. To improve machining quality and efficiency, an adaptive off-line interpolator was developed for NURBS curves in this paper. Both the chord accuracy and the acceleration/deceleration capability of machine tool are considered in the algorithm. There are four modules in the algorithm, adaptive feed rate adjustment, acceleration/deceleration disposal, feed rate modification, and S-type velocity generation. The acceleration/deceleration around the sharp corners is carefully calculated by those modules. A case study was provided to evaluate the feasibility of the interpolator. 相似文献
12.
Jingchun Feng Yuhao Li Yuhan Wang Ming Chen 《The International Journal of Advanced Manufacturing Technology》2010,48(1-4):227-241
With recent advances in high-speed and high-accuracy machining, the NURBS interpolator has shown significant effect on dealing with the free-form curves and surfaces. The existing study aims at developing the adaptive interpolator which confines the chord error, the tangent acceleration, and jerk. However, the excessive axis acceleration is still unavoidable at the sharp corners and will deteriorate the contour accuracy. In this paper, a real-time adaptive NURBS interpolator considering the acc/dec capacity for each individual axis is developed to confine both the chord error and the axis acceleration. The maximum feasible feed and tangent acceleration range are deduced, respecting the given axis acc/dec limit. A two-stage feed determination scheme is applied to calculate the adaptive feed rate for each sampling period. A look-ahead window is utilized to improve the calculation performance for real-time application. Simulations and experiments are performed to verify the resulting feed rate, acc/dec profiles, and the real-time performance of the proposed interpolator. 相似文献
13.
Adaptive parametric interpolation scheme with limited acceleration and jerk values for NC machining 总被引:3,自引:2,他引:1
Rong Zhen Xu Le Xie Cong Xin Li Dao Shan Du 《The International Journal of Advanced Manufacturing Technology》2008,36(3-4):343-354
Parametric interpolation has many advantages over the traditional linear or circular interpolation in computer numerical control
(CNC) machining. The existing work in this regard is reported to have achieved constant feedrate, confined chord error and
limited acceleration/deceleration in one interpolator. However, the excessive jerk still exists due to abrupt change in acceleration
profile, which will cause shock to the machine as well as deteriorate the surface accuracy. In this paper, an adaptive interpolation
scheme incorporating machine’s dynamics capability consideration is proposed and illustrated in details. In the proposed algorithm,
the commanded feedrate is maintained at most of the time and adaptively reduced in large curvature areas to meet the demand
of the machining accuracy requirement, while at the same time, the acceleration and jerk values are limited within the machine’s
capabilities during the whole interpolation process. It ensures a high machining accuracy, eliminates the phenomenon of overshoot/undershoot
and reduces mechanical shock to the machine tools. The real-time performance of this interpolator is also measured to demonstrate
its practical application. Two non-uniform rational B-spline (NURBS) curve interpolation experiments are provided to verify
the feasibility and advantages of the proposed scheme. 相似文献
14.
Yuwen Sun Zhenyuan Jia Fei Ren Dongming Guo 《The International Journal of Advanced Manufacturing Technology》2008,36(1-2):60-68
In precision machining of free-form surfaces at high speed, it is very important to ensure part accuracy and machining properties.
To achieve this, this paper develops a guide spline-based feedrate scheduling method for machining along curvilinear paths
with simultaneous constraints of chord errors and ac/deceleration. Based on two metrics about feedrate scheduling from the
view of geometric and kinematic properties, the nonlinear relationships between the arc-length parameter and path parameter
are subsequently established with a parameter correction spline. Then a guide spline associated with the modified curvature
radius of paths is constructed to the schedule feedrate. It is shown that determining the largest safe feedrate with constant
chord error can be reduced to the issue of changing the feedrate proportionally with the square root of path curvature radii
and ensuring the safe feed acceleration can be converted into the issue of presetting the largest slope of guide spline. The
simulation results prove that the proposed feedrate scheme has potential applications in the field of finish machining. 相似文献
15.
Liqiang Zhang Jingchun Feng Yuhan Wang Ming Chen 《The International Journal of Advanced Manufacturing Technology》2009,40(11-12):1191-1201
In free-form surface machining, it is essential to optimize the feedrate in order to improve the machining efficiency. Conservative constant feedrate values have been mostly used up to now since there was a lack of physical models and optimization tools for the machining processes. The overall goal of this research is the integration of geometric and mechanistic milling models for force prediction and feedrate scheduling in five-axis CNC free-form surface machining. For each tool move, the geometric model calculates the cut geometry, and a mechanistic model is used along with a maximum allowable cutting force to determine a desired feedrate. The results are written into the part NC program with optimized feedrates. When the integrated modeling approach based feedrate scheduling strategy introduced in this paper was used, it was shown that the machining time can be decreased significantly along the tool path. 相似文献
16.
Feedrate fluctuation caused by approximation errors of interpolation methods has great effects on machining quality in NURBS interpolation, but few methods can efficiently eliminate or reduce it to a satisfying level without sacrificing the computing efficiency at present. In order to solve this problem, a high accurate interpolation method for NURBS tool path is proposed. The proposed method can efficiently reduce the feedrate fluctuation by forming a quartic equation with respect to the curve parameter increment, which can be efficiently solved by analytic methods in real-time. Theoretically, the proposed method can totally eliminate the feedrate fluctuation for any 2nd degree NURBS curves and can interpolate 3rd degree NURBS curves with minimal feedrate fluctuation. Moreover, a smooth feedrate planning algorithm is also proposed to generate smooth tool motion with considering multiple constraints and scheduling errors by an efficient planning strategy. Experiments are conducted to verify the feasibility and applicability of the proposed method. This research presents a novel NURBS interpolation method with not only high accuracy but also satisfying computing efficiency. 相似文献
17.
In the machining of sculptured surfaces, five-axis CNC machine tools provide more flexibility to realize the cutter position as its axis orientation spatially changes. Conventional five-axis machining uses straight line segments to connect consecutive machining data points, and uses linear interpolation to generate command signals for positions between end points. Due to five-axis simultaneous and coupled rotary and linear movements, the actual machining motion trajectory is a non-linear path. The non-linear curve segments deviate from the linearly interpolated straight line segments, resulting in a non-linearity machining error in each machining step. These non-linearity errors, in addition to the linearity error, commonly create obstacles to the assurance of high machining precision. In this paper, a novel methodology for solving the non-linearity errors problem in five-axis CNC machining is presented. The proposed method is based on the machine type-specific kinematics and the machining motion trajectory. Non-linearity errors are reduced by modifying the cutter orientations without inserting additional machining data points. An off-line processing of a set of tool path data for machining a sculptured surface illustrates that the proposed method increases machining precision. 相似文献
18.
Lin Zhu Shuang-Shuang Peng Cheng-Long Yin Tien-Chien Jen Xi Cheng Yi-Hsin Yen 《The International Journal of Advanced Manufacturing Technology》2014,70(5-8):995-1007
In this paper, using the specifications of nodal points on a nonuniform rational B-spline (NURBS) curve of three degrees with respect to NURBS curve parameter and defining the coefficients for the velocity and acceleration vectors on these points, a new method is presented to design a tool path via C2 PH spline curves. Values of the velocity/acceleration vector coefficients corresponding to the nodal points on the original NURBS curve are computed by pattern search algorithm. To this end, the normal distance between the constructed C2 PH spline curve and its corresponding original NURBS curve is considered as the objective function. Using combination of the time-dependent feed rate interpolation in the acceleration/deceleration phase of the motion and the constant feed rate interpolation in the middle region of the motion, the position commands of the designed NURBS-based C2 PH spline curve are generated. Several improved NURBS-based C2 PH spline curve following tasks were implemented with pseudo-derivative feedback feed forward (PDFF) controller. The experimental and simulation results confirm that the devised interpolator with designed PDFF controller is not only feasible for machining the complicated tool path represented in the improved NURBS-based C2 PH spline form but also yields satisfactory contouring performance under variable feed rate. 相似文献
19.
Chung-Wei Cheng Wen-Peng Tseng 《The International Journal of Advanced Manufacturing Technology》2006,30(1-2):98-104
In recent years, various parametric curve interpolators have been proposed for high-speed and high-accuracy machining. However, these methods are based on a constant cutter location (CL) velocity. Hence, the cutter contact (CC) velocity along the surface tends to vary, resulting in a nonuniform machining performance. Furthermore, machining complex surfaces requires the provision of a large number of tool paths and therefore the associated NC data files are generally very large. To overcome these limitations, the current study presents a novel real-time NURBS surface interpolator which ensures a constant CC velocity along the CC paths and its intervals. A PC-based real-time motion control network utilizing SSCNET is developed to achieve the goal of multi-axis synchronous motion. In this study, both the NURBS surface interpolator algorithms and the SSCNET communication protocols are realized by Embedded XP with the RTX real-time kernel. The experimental results confirm that the proposed real-time NURBS surface interpolator is capable of achieving a satisfactory performance. 相似文献
20.
C.-W. Cheng M.-C. Tsai 《The International Journal of Advanced Manufacturing Technology》2004,23(11-12):865-873
This paper presents a real-time control algorithm based on Taylor’s expansion for implementing variable feed rate non-uniform rational B-spline (NURBS) curve interpolators using a digital signal processor for precision CNC machining. To efficiently compute the NURBS curve and its derivatives in real-time, an effective method is proposed. The variable feed rate NURBS curve interpolator can be used to realise the ACC/DEC before feed rate interpolation in which the ACC/DEC (acceleration/deceleration) planning on the feed rate command executes before the interpolation takes place, so that the path command errors caused by conventional ACC/DEC planning using the post feed rate interpolation can be effectively eliminated. To demonstrate the performance of the proposed algorithm, an X-Y table driven by two servomotors is controlled to track command paths represented by multiple blocks of NURBS curves. Experimental results verify the effectiveness of the proposed method. 相似文献