WO2019047458A1 - 一种五轴双样条曲线插补速度规划方法 - Google Patents

一种五轴双样条曲线插补速度规划方法 Download PDF

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WO2019047458A1
WO2019047458A1 PCT/CN2018/071689 CN2018071689W WO2019047458A1 WO 2019047458 A1 WO2019047458 A1 WO 2019047458A1 CN 2018071689 W CN2018071689 W CN 2018071689W WO 2019047458 A1 WO2019047458 A1 WO 2019047458A1
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speed
point
acceleration
sensitive interval
axis
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French (fr)
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贾振元
马建伟
宋得宁
陈思宇
贺广智
王福吉
刘巍
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大连理工大学
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Priority to US16/322,290 priority Critical patent/US11188056B2/en
Publication of WO2019047458A1 publication Critical patent/WO2019047458A1/zh

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    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05BCONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00Programme-control systems
    • G05B19/02Programme-control systems electric
    • G05B19/18Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
    • G05B19/416Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by control of velocity, acceleration or deceleration
    • G05B19/4163Adaptive control of feed or cutting velocity
    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05BCONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00Programme-control systems
    • G05B19/02Programme-control systems electric
    • G05B19/18Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
    • G05B19/41Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by interpolation, e.g. the computation of intermediate points between programmed end points to define the path to be followed and the rate of travel along that path
    • G05B19/4103Digital interpolation
    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05BCONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00Program-control systems
    • G05B2219/30Nc systems
    • G05B2219/34Director, elements to supervisory
    • G05B2219/34015Axis controller
    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05BCONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00Program-control systems
    • G05B2219/30Nc systems
    • G05B2219/34Director, elements to supervisory
    • G05B2219/34083Interpolation general
    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05BCONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00Program-control systems
    • G05B2219/30Nc systems
    • G05B2219/34Director, elements to supervisory
    • G05B2219/34135Spline
    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05BCONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00Program-control systems
    • G05B2219/30Nc systems
    • G05B2219/35Nc in input of data, input till input file format
    • G05B2219/35261Use of mathematical expression, functional equation
    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05BCONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00Program-control systems
    • G05B2219/30Nc systems
    • G05B2219/43Speed, acceleration, deceleration control ADC
    • G05B2219/43059Accelerate, decelerate all axis as function of max, min, average speed axis
    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05BCONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00Program-control systems
    • G05B2219/30Nc systems
    • G05B2219/43Speed, acceleration, deceleration control ADC
    • G05B2219/43156Feed rate

Definitions

  • the invention belongs to the technical field of precise and efficient intelligent multi-axis numerical control machining, and relates to a double-spline curve interpolation speed planning method under the constraint of the physical axis driving performance of a five-axis numerical control machine tool.
  • the curve interpolation technique has been widely concerned and studied because of its advantages such as high precision of machining trajectory and ideal model, stable motion of the processing process, and easy storage and transmission of processing codes compared with traditional linear and circular interpolation techniques.
  • the planning of the feed rate at each position on the curve is the prerequisite for achieving high quality and efficient machining. If the feed rate planning is too high, it is easy to cause the actual speed, acceleration, and jerk of each physical axis to exceed the corresponding allowable limit, thereby inducing sudden changes in motion, machine tremor, etc., affecting machining accuracy and processing quality.
  • the adaptive and reasonable planning of the curve interpolation feed rate is of great significance for the realization of precise and efficient machining.
  • the feed rate planning method for triaxial curve interpolation has been studied more, the feed rate planning strategy for five-axis double spline curve interpolation is still rarely reported.
  • the five-axis tool path is determined by a curve representing the movement of the tool tip point and a curve representing the movement of the other point outside the tool tip on the tool axis.
  • Prior Art Document 1 "Feedrate interpolation with axis jerk constraints on 5-axis NURBS and G1tool path", Beudaert et al, International Journal of Machine Tools and Manufacture, 2012, 57: 73-82, which is based on a five-axis tool path
  • the time step is discrete, and the displacement interval corresponding to the point is obtained according to the driving performance constraint at each discrete point, and then the time-optimized feed rate is planned by the binary iteration.
  • the planned feed rate of the method changes in real time during the interpolation process, that is, the speed fluctuation is frequent, although the processing efficiency is maximized, but it is not conducive to the improvement of the surface quality of the processing.
  • the invention aims to overcome the defects of the prior art, and invents a speed-sensitive interval constant-speed five-axis double-spline curve interpolation speed planning method under the constraint of physical axis driving performance with high computational efficiency, which adopts the contour of the interpolation curve to be processed, etc.
  • the arc length is discrete, and the differential order of each physical axis position to the arc length parameter is obtained. Then, the limit condition of the shaft driving performance is taken as the constraint, and the processing quality and processing efficiency are balanced, and the speed sensitive interval is optimized.
  • the two-way scanning is used to determine The speed value of each speed sensitive section and the starting point curve parameters of the rising and falling speeds adopt the determined constant feed speed in the sensitive interval, and the smooth feed rate is planned in the non-sensitive section by the S-shaped acceleration/deceleration mode.
  • the method can effectively balance the processing efficiency and processing quality of the five-axis curve interpolation, and the algorithm has a light calculation burden and good real-time performance.
  • the technical solution adopted by the invention is a five-axis double-spline curve interpolation speed planning method, which is characterized in that the method calculates the position of each physical axis on the basis of the arc length discretization of the tool nose point trajectory.
  • the first-order to third-order differential of the parameters so as to obtain the relationship between the physical axis motion and the tool path; with the limit condition of the shaft drive performance as the constraint, to balance the smoothness of the machining operation and the processing efficiency, optimize the speed sensitive interval;
  • Two-way scanning determining the speed value of each speed sensitive section and the starting and falling point curve parameters, using the determined constant feed rate in the sensitive interval, and using the S-shaped acceleration/deceleration mode to plan the smooth feed rate in the non-sensitive section; Specific steps are as follows:
  • the first step is to establish the relationship between the physical axis motion and the tool path.
  • C' P (u d,i ) and C′′ P (u d,i ) are respectively C P (u) for the parameter u at u d,i First and second order guides;
  • q s,i represents the first-order derivative of the physical axis motion position vector at the i-th tool tip point to the arc length of the tool nose point trajectory
  • q ss,i represents the physical axis motion position vector pair at the i-th tool tip point
  • the second-order derivative of the arc length of the tool nose point, q sss, i represents the third-order derivative of the physical axis motion position vector at the i-th tool tip point to the arc length of the tool nose point trajectory
  • the formula (3) is the physical axis. Equation of relationship between motion and tool path;
  • Step 2 Determine the speed sensitive interval
  • the relationship between the physical axis motion velocity, acceleration and jerk and the tangential velocity, acceleration and jerk of the tool tip point motion is:
  • the first-order, second-order, and third-order derivatives of the physical axis motion position vector versus time that is, the physical axis motion velocity vector, the acceleration vector, and the jerk vector
  • the first-order, second-order, and third-order differentials of the movement position of the tool tip point with respect to time are respectively, that is, the movement speed of the tool tip point, the tangential acceleration and the tangential jerk;
  • the set tool nose point motion speed limit is v max , firstly, the tool tip point motion tangential acceleration limit a t,max is equal to The minimum value of the acceleration limit of the motion of the three linear motion axes, and the tangential jerk limit j t,max of the tool point point motion is equal to The minimum of the kinetic acceleration limit of the three linear motion axes, and secondly, the goal of balancing the machining efficiency and the running smoothness, optimizing the values of a t, max and j t, max and determining the speed sensitive interval; defined at the tool tip point
  • the range of motion speed, acceleration and jerk of each physical axis may exceed the corresponding limit constraint condition as the speed sensitive interval. According to formula (4), it is obtained:
  • Constant speed operation although it can meet the smooth operation, but the processing efficiency is too low, so the values of a t, max and j t, max are optimized at this time, and then the speed sensitive interval is optimized.
  • the specific method is, at zero The minimum of the acceleration limit of the motion of the three linear motion axes and zero to Between the minimum values of the kinetic acceleration limits of the three linear motion axes, the dichotomy method is used to find the appropriate a t,max and j t,max values, so that the total arc length l sr of the corresponding speed sensitive interval is equal to the tool tip point motion.
  • the third step determines the allowable feed rate for each speed sensitive interval.
  • the initial allowable speed value of each speed sensitive section is calculated by the physical axis driving performance constraint; in order to ensure the smooth movement of the tool tip point and improve the calculation efficiency, a constant feed rate is planned in the speed sensitive range.
  • Tangential acceleration Tangential jerk Both are zero, according to formula (4), the initial allowable speed value of the kth speed sensitive interval is obtained. for:
  • min() represents the minimum function
  • the speed sensitive interval allowable speed value is updated in the S-shaped acceleration/deceleration mode; when the tangential acceleration and jerk limits are a t,max and j t,max respectively, Starting speed in S-shaped acceleration/deceleration mode Add, decelerate to end speed
  • acceleration and deceleration process maximum acceleration value a max j t,max t 1 , acceleration/deceleration time t 1 , constant acceleration/deceleration time t 2 , deceleration/deceleration time t 3 are:
  • int() denotes the downward rounding function
  • the starting area of the interpolation curve belongs to the speed sensitive interval, and the formula (8) is used to calculate the speed from the starting speed of 0 to Required displacement value Calculate the arc length l k of the speed sensitive interval by using formula (10);
  • the final updated feed rate value is obtained. That is, the final planned value of the kth speed sensitive interval feed rate that satisfies the physical axis drive performance constraint;
  • the fourth step is to calculate the starting point parameters of the rising and falling speeds and the corresponding speed values.
  • the feed rate corresponding to the end point of the speed reduction is v max ;
  • Step 5 Interpolation of each interpolation point parameter and corresponding feedrate
  • the parameter interval [ur i , ur i+1 ] where the current interpolation point curve parameter u j is located is judged, and t 1 , t 2 , t 3 are calculated:
  • the invention has the beneficial effects that the method is a five-axis double-spline curve interpolation speed planning method with physical axis driving performance constraints, and can realize the movement speed of the tool tip point with the constraints of various physical axis speeds, accelerations and jerk limits.
  • Fast and smooth planning the planning method generates a constant feed rate in the speed sensitive interval without iterative planning of the overall feed velocity profile.
  • the algorithm can realize the efficiency of 5-axis double spline curve interpolation processing with high computational efficiency. Coordination between the smoothness of movement.
  • the method can effectively balance the processing efficiency and processing quality of the five-axis curve interpolation, and the algorithm has a light calculation burden and good real-time performance.
  • Fig. 2 is a geometrical model diagram of a five-axis double-spline curve in a Cartesian coordinate system; wherein, curve 1 represents a trajectory curve of the tool tip point, and curve 2 represents a trajectory curve of the tool axis except a tool tip;
  • Figure 3 The planned feed rate of the tool tip point motion; where the A axis represents the spline curve parameter and the B axis represents the tool tip point motion feed rate in mm/s;
  • Figure 4 The actual movement speed of the linear axis; the A axis represents the spline curve parameter, the B axis represents the linear axis motion velocity value, the unit is mm/s, the curve 1 is the machine tool X axis motion speed, and the curve 2 is the machine tool Y axis motion speed. Curve 3 is the Z-axis movement speed of the machine tool;
  • Figure 5 The actual moving speed of the rotating shaft;
  • the A axis represents the spline curve parameter
  • the B axis represents the rotational axis motion speed value
  • the unit is rad/s
  • the curve 1 is the machine A axis moving speed
  • the curve 2 is the machine tool C axis moving speed.
  • Figure 6 The actual motion acceleration of the linear axis; where the A axis represents the spline curve parameter, the B axis represents the linear axis motion acceleration value in mm/s 2 , the curve 1 is the machine tool X axis motion acceleration, and the curve 2 is the machine tool Y axis motion. Acceleration, curve 3 is the Z-axis motion acceleration of the machine tool;
  • Figure 7 The actual motion acceleration of the rotating axis; the A axis represents the spline curve parameter, the B axis represents the rotational axis motion velocity value, the unit is rad/s 2 , the curve 1 is the machine A axis motion acceleration, and the curve 2 is the machine tool C axis motion. Acceleration
  • Figure 8 The actual motion jerk of the linear axis; where the A axis represents the spline curve parameter, the B axis represents the linear axis motion jerk value, the unit is mm/s 3 , the curve 1 is the machine tool X axis motion jerk, and the curve 2 is the machine tool Y-axis motion jerk, curve 3 is the Z-axis motion jerk of the machine tool;
  • Figure 9 The actual motion jerk of the rotary axis; where the A axis represents the spline curve parameter, the B axis represents the rotational axis motion velocity value, the unit is rad/s 3 , the curve 1 is the machine A axis motion jerk, and the curve 2 is the machine tool C Axial motion jerk;
  • FIG. 1 is a general flow chart of a method
  • FIG. 2 is a geometrical model diagram of a five-axis double-spline curve in a Cartesian coordinate system.
  • the tool rail shown in FIG. 2 is taken as an example to describe in detail a specific implementation process of the present invention.
  • Curve 1 the parameter of the tool nose point trajectory curve is: order: 2; control point: ⁇ (0,0,0), (5,-5,-2), (10,0,0),( 0,20,2),(10,30,5),(30,30,5),(40,20,2),(30,0,0),(35,-5,-2),( 40,0,0) ⁇ ; weight factor: ⁇ 1;0.5;2;1;2;2;1;2;0.5;1 ⁇ ; node vector: ⁇ 0,0,0,1/8,2/8 , 3/8, 4/8, 5/8, 6/8, 7/8, 1, 1, 1 ⁇ , the order, weight factor and node vector of curve 2 are the same as curve 1, and the control points are: ⁇ ( 0,0,2),(5,-6,0),(10,0,2),(-5,20,4),(10,33,7),(30,33,7),( 45, 20, 4), (30, 0, 2), (35, -6, 0), (40, 0, 2) ⁇ .
  • the five-axis double-spline curve interpolation speed planning is performed.
  • the specific steps are as follows:
  • the arc length of the point motion track is discrete, and the tool tip point and the tool axis vector are calculated by the formula (2).
  • the physical axis motion position vector q is obtained, and then the physics is obtained according to the formula (3).
  • Step 2 Determine the speed sensitive interval: Calculate the physical axis motion velocity vector according to formula (4) Acceleration vector And jerk vector The relationship between q s , q ss and q sss is set to limit the movement speed of X, Y and Z axes of the five-axis machine tool to 300mm/s, the axial acceleration limit is 1000mm/s 2 , and the axial acceleration limit is 20000mm.
  • a and C axis motion speed limit is 30rad/s
  • axis acceleration limit is 100rad/s 2
  • axis acceleration limit is 2000rad/s 3
  • ie Set the tangential speed limit v max 30mm/s of the tool nose point, calculate the speed sensitive interval parameter set according to the physical axis driving performance limit condition, and calculate the tangential acceleration limit a t,max and the jerk limit j t,max ;
  • the third step is to determine the allowable feed rate for each speed sensitive interval: first, the physical axis drive performance limit is used as the constraint condition, and the initial allowable speed value of each speed sensitive interval is calculated according to formula (7). According to the tangential acceleration and the tangential jerk limit, the permissible feed rate of each speed sensitive interval is updated based on the two-way scanning method. At the same time, calculate the tangential acceleration limit a b,max of the initial speed increase process, the final acceleration process jerk limit a f,max , the initial speed increase process tangential jerk limit j b,max , the last speed reduction process plus Acceleration limit j f,max ;
  • the fifth step is to interpolate the parameters of each interpolation point and the corresponding feed rate in real time: firstly determine the interval of the current interpolation point parameter, and then calculate the current interpolation point speed according to the content of the fifth step in the invention, and then calculate according to formula (24).
  • Next interpolation point parameter judge whether the end point of the curve is reached. If it does not arrive, return to the fifth step to calculate the feed rate of the next interpolation point. If it arrives, the algorithm ends.
  • Figure 3 shows the feedrate speed of the tool tip point motion finally calculated according to the above steps, wherein the A axis represents the spline curve parameter, and the B axis represents the tool tip point motion feed speed in mm/s; It can be seen that, except for the smooth transition of part of the transition area, the planned five-axis double-spline curve interpolation feed rate is kept constant, which is beneficial to coordinate the processing efficiency and the running smoothness.
  • Figure 4 shows the actual linear motion speeds of the three linear axes obtained by the planned feed speed machining; the A axis represents the spline curve parameters, the B axis represents the linear axis motion speed value, the unit is mm/s, and the curve 1 is The X-axis movement speed of the machine tool, curve 2 is the Y-axis movement speed of the machine tool, and curve 3 is the Z-axis movement speed of the machine tool; it can be seen that the absolute value of the actual movement speed of each linear axis is less than the linear axis movement speed limit setting value of 300 mm/s.
  • Figure 5 shows the actual movement speeds of the two rotating shafts obtained by the planned feed speed machining; where the A axis represents the spline curve parameter and the B axis represents the rotational axis motion speed value in rad/s, curve 1 is The A-axis movement speed of the machine tool, curve 2 is the C-axis movement speed of the machine tool; the absolute value of the actual movement speed of each rotation axis is smaller than the rotation axis movement speed limit setting value 30rad/s.
  • Figure 6 shows the actual motion accelerations of the three linear axes obtained by the planned feed rate machining, where the A axis represents the spline curve parameter and the B axis represents the linear axis motion acceleration value in mm/s 2 , curve 1 For the X-axis motion acceleration of the machine tool, curve 2 is the Y-axis motion acceleration of the machine tool, and curve 3 is the Z-axis motion acceleration of the machine tool. It can be seen that the absolute value of the actual motion acceleration of each linear axis is less than the linear axis motion acceleration limit setting value of 1000mm/s. 2 .
  • Figure 7 shows the actual motion acceleration of two rotating axes obtained by machining at the planned feed speed, where the A axis represents the spline curve parameter and the B axis represents the rotational axis motion speed value in rad/s 2 , curve 1
  • curve 2 is the C-axis motion acceleration of the machine tool; it can be seen that the absolute value of the actual motion acceleration of each rotary axis is less than the rotational axis motion acceleration limit setting value of 100 rad/s 2 .
  • Figure 8 shows the actual motion jerk of three linear axes obtained by machining at the planned feed speed.
  • the A axis represents the spline curve parameter and the B axis represents the linear axis motion jerk value in mm/s 3 .
  • Curve 1 is the X-axis motion jerk of the machine tool
  • curve 2 is the Y-axis motion jerk of the machine tool
  • curve 3 is the Z-axis motion jerk of the machine tool. It can be seen that the absolute value of the actual motion jerk of each linear axis is smaller than the linear axis motion jerk.
  • the limit setting is 20000mm/s 2 .
  • Figure 9 shows the actual motion jerk of two rotating axes obtained by machining at the planned feed rate, where the A axis represents the spline curve parameter and the B axis represents the rotational axis motion speed value in rad/s 3 , the curve 1 is the acceleration of the A-axis motion of the machine tool, and the curve 2 is the acceleration of the C-axis motion of the machine tool. It can be seen that the absolute value of the actual motion jerk of each rotary axis is less than the set value of the rotational axis motion jerk limit of 2000 rad/s 3 .
  • the planned five-axis double-spline curve interpolation feed rate can be kept constant in most of the curve, and can meet the limit constraint of each physical axis drive performance.
  • the method adopts the speed-sensitive interval constant-speed five-axis double-spline curve interpolation speed planning method with the physical axis driving performance limit as the constraint, coordinates the five-axis machining efficiency and running stability, and improves the performance of the five-axis CNC machine tool.

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Abstract

一种五轴双样条曲线插补速度规划方法,涉及一种五轴数控机床物理轴驱动性能约束下的速度敏感区间恒速双样条曲线插补速度规划方法。本方法在对刀尖点轨迹曲线(1)进行等弧长离散的基础上,计算五轴机床各物理轴位置对刀尖点轨迹弧长参数的一阶到三阶微分,从而获得物理轴运动与刀具轨迹间关系。以轴驱动性能极限条件为约束,以平衡加工运行平稳性和加工效率为目标,优化求取速度敏感区间。通过双向扫描,确定各速度敏感区间的速度值及升、降速起始点曲线参数。本方法可有效平衡五轴曲线插补加工效率和加工质量,且算法计算效率高,实时性好。

Description

一种五轴双样条曲线插补速度规划方法 技术领域
本发明属于精密高效智能化多轴数控加工技术领域,涉及一种五轴数控机床物理轴驱动性能约束下的双样条曲线插补速度规划方法。
背景技术
目前,曲线插补技术因相比于传统直线、圆弧插补技术具有加工轨迹与理想模型逼近精度高、加工过程运动平稳、加工代码易于存储与传输等优势,受到了广泛关注和研究。在曲线插补加工过程中,曲线上各位置处进给速度的规划是实现高质高效加工的前提。若进给速度规划过高,易导致各物理轴实际速度、加速度、加加速度等超出相应的许用极限,从而诱发运动突变、机床震颤等现象,影响加工精度和加工质量。若进给速度规划过低,则虽可满足轴驱动性能约束,但易由于速度过于保守而降低加工效率。因此,根据数控机床物理轴运动性能许用极限条件,进行曲线插补进给速度的自适应合理规划,对实现精密高效加工具有重要意义。虽然针对三轴曲线插补的进给速度规划方法已有较多研究,但面向五轴双样条曲线插补的进给速度规划策略仍鲜有报道。在五轴双样条曲线插补过程中,五轴刀具轨迹由一条表示刀尖点运动的曲线和一条表示刀轴上刀尖外另一点运动的曲线共同确定。因除三个直线轴运动外,引入了两个旋转轴运动以实现刀轴方向的连续变化,导致五轴双样条曲线插补加工过程中物理轴运动和刀尖点运动间具有极强的非线性关联关系,为刀尖点运动进给速度的合理规划提出了巨大挑战。如何以五个物理轴驱动性能极限为约束条件,规划双样条曲线插补加工过程中的刀尖点进给速度,已成为五轴数控曲线插补技术亟需解决的难题之一。
现有技术文献1“Feedrate interpolation with axis jerk constraints on 5-axis NURBS and G1tool path”,Beudaert等,International Journal of Machine Tools and Manufacture,2012,57:73-82,该文献通过对五轴刀具轨迹进行等时间步长离散,在每个离散点处依据驱动性能约束求取该点对应的位移区间,进而通过二分迭代规划时间最优的进给速度。然而,该方法所规划进给速度在插补过程中实时变化,即速度波动频繁,虽最大程度上提高了加工效率,但不利于加工表面质量的提高,此外,该方法进行速度插补时,需要复杂的迭代算法,实时性差。文献2“A smooth curve evolution approach to the feedrate planning on five-axis toolpath with geometric and kinematic constraints”,Sun等,International Journal of Machine Tools and Manufacture,2015,97:86-97,该文献利用曲线演化的思想,基于进给速度的比例调节,对五轴曲线插补过程中进给速度轮廓进行迭代规划,以满足轴驱动性能约束条件。然而,该方法计算量大,属离线方法,难以应用到实时插补过程中。
发明内容
本发明旨在克服现有技术缺陷,发明一种计算效率高的物理轴驱动性能约束下速度敏感区间恒速五轴双样条曲线插补速度规划方法,该方法通过对待插补曲线轮廓进行等弧长离散,获得各物理轴位置对弧长参数的各阶微分;进而以轴驱动性能极限条件为约束,以平衡加工质量和加工效率为目标,优化求取速度敏感区间;通过双向扫描,确定各速度敏感区间的速度值及升、降速起始点曲线参数,在敏感区间采用所确定的恒定进给速度,在非敏感区间利用S形加减速模式规划平滑进给速度。该方法可有效平衡五轴曲线插补加工效率和加工质量,且算法计算负担轻,实时性好。
本发明采用的技术方案是一种五轴双样条曲线插补速度规划方法,其特性在于,该方法在对刀尖点轨迹进行等弧长离散的基础上,计算各物理轴位置对弧长参数的一阶到三阶微分,从而获得物理轴运动与刀具轨迹间关联关系;以轴驱动性能极限条件为约束,以平衡加工运行平稳性和加工效率为目标,优化求取速度敏感区间;通过双向扫描,确定各速度敏感区间的速度值及升、降速起始点曲线参数,在敏感区间采用所确定的恒定进给速度,在非敏感区间利用S形加减速模式规划平滑进给速度;方法具体步骤如下:
第一步 建立物理轴运动与刀具轨迹间关联关系
设待插补双样条曲线中的刀尖点运动轨迹曲线方程为C P=C P(u),刀轴上除刀尖外另一点运动轨迹曲线方程为C Q=C Q(u),首先对刀尖点运动轨迹曲线进行等弧长离散,设弧长步长为δ s,离散后第i个离散点对应的曲线参数为u d,i,则利用二阶泰勒级数展开,第i+1个离散点对应的曲线参数u d,i+1由如下递推公式计算:
Figure PCTCN2018071689-appb-000001
其中,|| ||表示欧几里得范数,C′ P(u d,i)和C″ P(u d,i)分别为C P(u)对参数u在u d,i处的一阶和二阶导矢;
令R=[R x,R y,R z] T表示刀尖点,O=[O x,O y,O z] T表示刀轴矢量,在得到离散点对应的曲线参数u d,i,i=1,2,…,N d后,N d表示离散点总数,计算离散后第i个刀尖点R i=[R x,i,R y,i,R zi,] T和第i个刀轴矢量O i=[O x,i,O y,i,O z,i] T
Figure PCTCN2018071689-appb-000002
利用五轴机床运动学变换,根据公式(2)获得的刀尖点和刀轴矢量,计算出五个物理轴运动位置,令q表示物理轴运动位置向量,且q为五行一列的向量,其中五个元素对应于机床的五个物理轴,将对应于第i个刀尖点和第i个刀轴矢量的第i个物理轴运动位置向量表示为q i,由此,计算物理轴位置对刀尖点轨迹弧长的一阶到三阶微分:
Figure PCTCN2018071689-appb-000003
其中,q s,i表示第i个刀尖点处物理轴运动位置向量对刀尖点轨迹弧长的一阶导矢,q ss,i表示 第i个刀尖点处物理轴运动位置向量对刀尖点轨迹弧长的二阶导矢,q sss,i表示第i个刀尖点处物理轴运动位置向量对刀尖点轨迹弧长的三阶导矢,公式(3)即为物理轴运动与刀具轨迹间关联关系方程;
第二步 确定速度敏感区间
依据微分原理,物理轴运动速度、加速度及加加速度与刀尖点运动切向速度、加速度及加加速度关系为:
Figure PCTCN2018071689-appb-000004
其中,
Figure PCTCN2018071689-appb-000005
分别为物理轴运动位置向量对时间的一阶、二阶、三阶导矢,即物理轴运动速度向量、加速度向量及加加速度向量;
Figure PCTCN2018071689-appb-000006
分别为刀尖点运动位置对时间的一阶、二阶、三阶微分,即刀尖点运动速度、切向加速度及切向加加速度;
设物理轴运动速度极限为
Figure PCTCN2018071689-appb-000007
物理轴运动加速度极限为
Figure PCTCN2018071689-appb-000008
物理轴运动加加速度极限为
Figure PCTCN2018071689-appb-000009
设定的刀尖点运动速度极限为v max,首先令刀尖点运动切向加速度极限a t,max等于
Figure PCTCN2018071689-appb-000010
中三个直线运动轴运动加速度极限的最小值、令刀尖点运动切向加加速度极限j t,max等于
Figure PCTCN2018071689-appb-000011
中三个直线运动轴运动加加速度极限的最小值,其次,以平衡加工效率和运行平稳度为目标,优化a t,max和j t,max取值并确定速度敏感区间;定义在刀尖点以最大速度、加速度和加加速度运动的情况下,各物理轴运动速度、加速度和加加速度可能超出相应的极限约束条件的区间为速度敏感区间,根据公式(4),可得:
Figure PCTCN2018071689-appb-000012
据此,扫描各刀尖点运动轨迹离散点,将满足不等式|q s,i|v max>q max
Figure PCTCN2018071689-appb-000013
之一的离散点作为速度敏感区间内的点,设得到的速度敏感区间总段数为N sr,第k段速度敏感区间的起始、结束位置对应的离散点序号分别为n s,k和n e,k,则速度敏感区间对应的离散点序号集合可表示为{[n s,k,n e,k]},k=1,2,…,N sr;因此,刀尖点运动轨迹曲线上速度敏感区间的总弧 长l sr为:
Figure PCTCN2018071689-appb-000014
设刀尖点运动轨迹曲线的总弧长为l t,若l sr<l t/2,说明运动轨迹上大部分区域属于非速度敏感区间,可以以最大速度v max进行恒速运行,即可同时保证运行平稳和高效率加工,故此时规划的速度敏感区间较优;反之,若l sr>l t/2,说明运动轨迹上大部分区域属于速度敏感区间,需以区间内最小许用速度进行恒速运行,虽然可满足运行平稳,但加工效率过低,故此时对a t,max和j t,max的取值进行优化,进而优化速度敏感区间,具体方法为,在零到
Figure PCTCN2018071689-appb-000015
中三个直线运动轴运动加速度极限的最小值之间以及零到
Figure PCTCN2018071689-appb-000016
中三个直线运动轴运动加加速度极限的最小值之间,利用二分法寻找合适的a t,max和j t,max取值,使得对应的速度敏感区间总弧长l sr等于刀尖点运动轨迹曲线总弧长l t的一半,即l sr=l t/2;通过上述步骤,得到最终的速度敏感区间曲线参数集合表示为{[u s,k,u e,k]},k=1,2,…,N sr
第三步 确定各速度敏感区间许用进给速度
首先,以物理轴驱动性能为约束计算各速度敏感区间初始许用速度值;为保证刀尖点进给运动平稳,同时提高计算效率,在速度敏感区间内,规划恒定的进给速度,此时,切向加速度
Figure PCTCN2018071689-appb-000017
切向加加速度
Figure PCTCN2018071689-appb-000018
均为零,根据公式(4),得第k个速度敏感区间的初始许用速度值
Figure PCTCN2018071689-appb-000019
为:
Figure PCTCN2018071689-appb-000020
i∈{n s,k,…,n e,k},j∈{1,…,5}
其中,min()表示取最小值函数;
其次,以切向加速度、加加速度为约束,在S形加减速模式下更新速度敏感区间许用速度值;当切向加速度、加加速度极限分别为a t,max和j t,max时,在S形加减速模式下,从起始速度
Figure PCTCN2018071689-appb-000021
加、减速到结束速度
Figure PCTCN2018071689-appb-000022
过程所需要的位移值
Figure PCTCN2018071689-appb-000023
为:
Figure PCTCN2018071689-appb-000024
其中,加减速过程最大加速度值a max=j t,maxt 1,加加/减速时间t 1,恒加/减速时间t 2,减加/减速时间t 3为:
Figure PCTCN2018071689-appb-000025
通过双向扫描更新速度敏感区间许用速度值
Figure PCTCN2018071689-appb-000026
具体步骤如下:
从k=N sr到k=1进行逆向扫描,规划降速过程各速度敏感区间许用速度,其流程为:
1)令k=N sr
2)若k=N sr,判断n e,k=N d是否成立,若成立转第3)步,若不成立,转第5)步;若k≠N sr,转第6)步;
3)此时,插补曲线的结束区域属于速度敏感区间,利用公式(8)计算从起始速度
Figure PCTCN2018071689-appb-000027
减速到0所需要的位移值
Figure PCTCN2018071689-appb-000028
及该速度敏感区间弧长l k
l k=δ d·(n e,k-n s,k)  (10)
Figure PCTCN2018071689-appb-000029
直接转第4)步,否则,在0到
Figure PCTCN2018071689-appb-000030
之间利用二分法寻找速度值
Figure PCTCN2018071689-appb-000031
使得
Figure PCTCN2018071689-appb-000032
Figure PCTCN2018071689-appb-000033
更新该速度敏感区间许用速度值
Figure PCTCN2018071689-appb-000034
并重新计算
Figure PCTCN2018071689-appb-000035
转第4)步;
4)因当插补曲线的结束区域属于速度敏感区间时,最终降速过程必须在速度敏感区间内完成,故判断该降速过程中是否出现超出物理轴驱动性能极限约束的情况,计算降速过程所经历的离散点数量n f
Figure PCTCN2018071689-appb-000036
其中int()表示向下取整函数;根据S形加减速过程位移与切向速度、加速度、加加速度关系,反求第N sr个速度敏感区间内降速过程各离散点处刀尖点速度
Figure PCTCN2018071689-appb-000037
切向加速度
Figure PCTCN2018071689-appb-000038
切向加加速度
Figure PCTCN2018071689-appb-000039
j∈{n d-n f,…,n d},并代入公式(4),求得第N sr个速度敏感区间内降速过程各离散点处所需轴速度向量
Figure PCTCN2018071689-appb-000040
轴加速度向量
Figure PCTCN2018071689-appb-000041
轴加加速度向量
Figure PCTCN2018071689-appb-000042
j∈{n d-n f,…,n d},计算最末降速过程最大轴驱动极限与所需轴运动参数比值的最小值K f
Figure PCTCN2018071689-appb-000043
i∈{1,…,5},j∈{n s,k,…,n e,k}
比较K f与1的大小,确定第N sr个速度敏感区间内降速过程切向速度、加速度、加加速度值调整比例K f,t
K f,t=min(K f,1)  (13)
令第N sr个速度敏感区间内降速过程许用切向加速度
Figure PCTCN2018071689-appb-000044
第N sr个速度敏感区间内降速过程许用切向加加速度
Figure PCTCN2018071689-appb-000045
更新该速度敏感区间许用速度值
Figure PCTCN2018071689-appb-000046
5)当k=N sr且n e,k≠N d时,说明最后一个速度敏感区间结束位置与插补曲线结束间存 在非速度敏感区间,因此,在该非速度敏感区间内规划降速过程;利用公式(8)计算从起始速度
Figure PCTCN2018071689-appb-000047
减速到0所需要的位移值
Figure PCTCN2018071689-appb-000048
同时计算最末非速度敏感区间弧长l f
l f=δ d·(N d-n e,k)  (14)
Figure PCTCN2018071689-appb-000049
在0到
Figure PCTCN2018071689-appb-000050
之间利用二分法寻找速度值
Figure PCTCN2018071689-appb-000051
使得
Figure PCTCN2018071689-appb-000052
Figure PCTCN2018071689-appb-000053
更新该速度敏感区间许用速度值
Figure PCTCN2018071689-appb-000054
转第7)步;
6)判断是否为减速过程,若
Figure PCTCN2018071689-appb-000055
则为升速过程,转第7)步,否则,计算从
Figure PCTCN2018071689-appb-000056
降速到
Figure PCTCN2018071689-appb-000057
所需要的位移值
Figure PCTCN2018071689-appb-000058
及第k个非速度敏感区间弧长l r,k
l r,k=δ d·(n s,k+1-n e,k)  (15)
Figure PCTCN2018071689-appb-000059
时,在0到
Figure PCTCN2018071689-appb-000060
之间利用二分法寻找速度值
Figure PCTCN2018071689-appb-000061
使得
Figure PCTCN2018071689-appb-000062
Figure PCTCN2018071689-appb-000063
更新该速度敏感区间许用速度值
Figure PCTCN2018071689-appb-000064
转第7)步;
7)若k=1,结束,否则,令k=k-1,转第2)步;
从k=1到k=N sr进行正向扫描,规划升速过程各速度敏感区间许用速度,其流程为:
1)令k=1;
2)若k=1,判断n s,k=1是否成立,若成立转第3)步,若不成立,转第5)步;若k≠1,转第6)步;
3)此时,插补曲线的起始区域属于速度敏感区间,利用公式(8)计算从起始速度0升速到
Figure PCTCN2018071689-appb-000065
所需要的位移值
Figure PCTCN2018071689-appb-000066
利用公式(10)计算该速度敏感区间弧长l k
Figure PCTCN2018071689-appb-000067
直接转第4)步,否则,在0到
Figure PCTCN2018071689-appb-000068
之间利用二分法寻找速度值
Figure PCTCN2018071689-appb-000069
使得
Figure PCTCN2018071689-appb-000070
Figure PCTCN2018071689-appb-000071
更新该速度敏感区间许用速度值
Figure PCTCN2018071689-appb-000072
并重新计算
Figure PCTCN2018071689-appb-000073
转第4)步;
4)因当插补曲线的起始区域属于速度敏感区间时,初始升速过程必须在速度敏感区间内完成,故判断该升速过程中是否出现超出物理轴驱动性能极限约束的情况,计算升速过程所经历的离散点数量n b
Figure PCTCN2018071689-appb-000074
根据S形加减速过程位移与切向速度、加速度、加加速度关系,反求第1个速度敏感区间内升速过程各离散点处刀尖点速度
Figure PCTCN2018071689-appb-000075
切向加速度
Figure PCTCN2018071689-appb-000076
切向加加速度
Figure PCTCN2018071689-appb-000077
j∈{1,…,n b},并代入公式(4),求得第1个速度敏感区间内升速过程各离散点处所需轴速度向量
Figure PCTCN2018071689-appb-000078
轴加速度向量
Figure PCTCN2018071689-appb-000079
轴加加速度向量
Figure PCTCN2018071689-appb-000080
j∈{1,…,n b},计算初始升速过程最大轴驱动极限与所需轴运动参数比值的最小值K b
Figure PCTCN2018071689-appb-000081
i∈{1,…,5},j∈{1,…,n b}
比较K b与1的大小,确定第1个速度敏感区间内升速过程切向速度、加速度、加加速度值调整比例K b,t
K b,t=min(K b,1)  (18)
令第1个速度敏感区间内升速过程许用切向加速度
Figure PCTCN2018071689-appb-000082
第1个速度敏感区间内升速过程许用切向加加速度
Figure PCTCN2018071689-appb-000083
更新该速度敏感区间许用速度值
Figure PCTCN2018071689-appb-000084
5)当k=1且n s,k≠1时,说明第1个速度敏感区间起始位置与插补曲线起始位置之间存在非速度敏感区间,因此,在该非速度敏感区间内规划升速过程;利用公式(8)计算从起始速度0升速到
Figure PCTCN2018071689-appb-000085
所需要的位移值
Figure PCTCN2018071689-appb-000086
同时利用公式(15)计算第k个非速度敏感区间弧长l r,k
Figure PCTCN2018071689-appb-000087
在0到
Figure PCTCN2018071689-appb-000088
之间利用二分法寻找速度值
Figure PCTCN2018071689-appb-000089
使得
Figure PCTCN2018071689-appb-000090
Figure PCTCN2018071689-appb-000091
更新该速度敏感区间许用速度值
Figure PCTCN2018071689-appb-000092
转第7)步;
6)判断是否为升速过程,若
Figure PCTCN2018071689-appb-000093
则为降速过程,转第7)步,否则,计算从
Figure PCTCN2018071689-appb-000094
升速到
Figure PCTCN2018071689-appb-000095
所需要的位移值
Figure PCTCN2018071689-appb-000096
及第k个非速度敏感区间弧长l r,k
Figure PCTCN2018071689-appb-000097
时,在0到
Figure PCTCN2018071689-appb-000098
之间利用二分法寻找速度值
Figure PCTCN2018071689-appb-000099
使得
Figure PCTCN2018071689-appb-000100
Figure PCTCN2018071689-appb-000101
更新该速度敏感区间许用速度值
Figure PCTCN2018071689-appb-000102
转第7)步;
7)若k=N sr-1,转第8)步,否则,令k=k+1,转第2)步;
8)当n e,k=N d且K f,t<1时,判断第N sr个速度敏感区间的许用速度
Figure PCTCN2018071689-appb-000103
是否在升速过程速度规划过程中被更新,若是,计算更新后速度与更新前速度比值K ba,令K f,t=K ba·K f,t,再次更新第N sr个速度敏感区间内降速过程许用切向加速度
Figure PCTCN2018071689-appb-000104
第N sr个速度敏感区间内降速过程许用切向加加速度
Figure PCTCN2018071689-appb-000105
结束双向扫描;
经过上述逆向扫描降速过程进给速度规划和正向扫描升速过程进给速度规划,得到最终更新的进给速度值
Figure PCTCN2018071689-appb-000106
即为满足物理轴驱动性能约束的第k个速度敏感区间进给速度最终规划值;
第四步 升、降速起始点参数及相应速度值计算
判断非速度敏感区间弧长l r,k是否大于进给速度从第k个速度敏感区间的许用速度
Figure PCTCN2018071689-appb-000107
增加到设定的刀尖点运动进给速度极限v max再降低到第k+1个速度敏感区间的许用速度
Figure PCTCN2018071689-appb-000108
所需位移之和,即判断不等式(19)是否成立:
Figure PCTCN2018071689-appb-000109
若不等式(19)成立,从第k个到第k+1个速度敏感区间之间执行升速(从
Figure PCTCN2018071689-appb-000110
增加到v max)和降速(从v max降低至
Figure PCTCN2018071689-appb-000111
两个过程;升速起始点参数为u e,k,相对应的进给速度值为
Figure PCTCN2018071689-appb-000112
降速起始点参数u dc为:
Figure PCTCN2018071689-appb-000113
降速结束点对应的进给速度为v max
若不等式(19)不成立,为保证进给速度轮廓平滑,第k个到第k+1个速度敏感区间之间仅执行升速或降速过程;若
Figure PCTCN2018071689-appb-000114
执行升速过程,升速起始点参数为u e,k,相对应的进给速度值为
Figure PCTCN2018071689-appb-000115
Figure PCTCN2018071689-appb-000116
执行降速过程,降速起始点参数u dc为:
Figure PCTCN2018071689-appb-000117
该降速起始点相对应的进给速度值为
Figure PCTCN2018071689-appb-000118
设经上述步骤获得的升、降速起始点共n个,将升、降速起始点参数及相应进给速度集合记为{ur i,vu i},i=1,2,…,n,其中ur i为第i个升/降速起始点参数,vu i为第i个升/降速起始点速度;
第五步 各插补点参数及相应进给速度实时插补
在实时插补过程中,判断当前插补点曲线参数u j所在的参数区间[ur i,ur i+1],计算t 1、t 2、t 3
Figure PCTCN2018071689-appb-000119
其中,当i=1时,
Figure PCTCN2018071689-appb-000120
当i=n时,
Figure PCTCN2018071689-appb-000121
Figure PCTCN2018071689-appb-000122
否则a t,m=a t,max、j t,m=j t,max
当插补参数进入该区间的总时间t<t 1+t 2+t 3时,当前插补点进给速度v j为:
Figure PCTCN2018071689-appb-000123
其中,a m=j f,max·t 1;当插补参数进入该区间的总时间t≥t 1+t 2+t 3时,当前插补点进给速度v j=vu i+1;根据二阶泰勒展开法计算下一插补点参数u j+1
Figure PCTCN2018071689-appb-000124
其中T为插补周期;判断是否到达曲线终点,若到达终点,则结束插补,否则,令j=j+1,重新执行第五步;据此,实现满足物理轴驱动能力极限约束的五轴双样条曲线插补速度规划。
本发明的有益效果是:该方法是物理轴驱动性能约束的五轴双样条曲线插补速度规划方法,可实现以各个物理轴速度、加速度、加加速度极限为约束条件的刀尖点运动速度快速平滑规划;该规划方法在速度敏感区间生成恒定的进给速度,无需对整体进给速度轮廓进行迭代规划,算法可在计算效率高的情况下实现五轴双样条曲线插补加工效率和运动平稳性间的 协调。该方法可有效平衡五轴曲线插补加工效率和加工质量,且算法计算负担轻,实时性好。
附图说明
图1—方法整体流程图;
图2—直角坐标系中五轴双样条曲线刀轨几何模型图;其中,曲线1表示刀尖点运动轨迹曲线,曲线2表示刀轴上除刀尖外一点运动轨迹曲线;
图3—规划的刀尖点运动进给速度;其中A轴表示样条曲线参数,B轴表示刀尖点运动进给速度,单位为mm/s;
图4—直线轴实际运动速度;其中A轴表示样条曲线参数,B轴表示直线轴运动速度值,单位为mm/s,曲线1为机床X轴运动速度,曲线2为机床Y轴运动速度,曲线3为机床Z轴运动速度;
图5—旋转轴实际运动速度;其中A轴表示样条曲线参数,B轴表示旋转轴运动速度值,单位为rad/s,曲线1为机床A轴运动速度,曲线2为机床C轴运动速度;
图6—直线轴实际运动加速度;其中A轴表示样条曲线参数,B轴表示直线轴运动加速度值,单位为mm/s 2,曲线1为机床X轴运动加速度,曲线2为机床Y轴运动加速度,曲线3为机床Z轴运动加速度;
图7—旋转轴实际运动加速度;其中A轴表示样条曲线参数,B轴表示旋转轴运动速度值,单位为rad/s 2,曲线1为机床A轴运动加速度,曲线2为机床C轴运动加速度;
图8—直线轴实际运动加加速度;其中A轴表示样条曲线参数,B轴表示直线轴运动加加速度值,单位为mm/s 3,曲线1为机床X轴运动加加速度,曲线2为机床Y轴运动加加速度,曲线3为机床Z轴运动加加速度;
图9—旋转轴实际运动加加速度;其中A轴表示样条曲线参数,B轴表示旋转轴运动速度值,单位为rad/s 3,曲线1为机床A轴运动加加速度,曲线2为机床C轴运动加加速度;
具体实施方式
结合技术方案与附图详细说明本发明的具体实施方式。
在五轴双样条曲线插补加工过程中,由于五轴刀轨运动与物理轴运动间存在极强非线性对应关系,导致以物理轴驱动能力为约束的进给速度规划困难。为解决这一难题,实现高效进给速度规划,提高五轴加工效率及加工质量,发明一种五轴双样条曲线插补速度规划方法。
附图1为方法整体流程图,附图2为直角坐标系中五轴双样条曲线刀轨几何模型图,以附图2所示刀轨为例,详细说明本发明具体实施过程,其中,曲线1,即刀尖点运动轨迹曲线的参数为:阶数:2;控制点:{(0,0,0),(5,-5,-2),(10,0,0),(0,20,2),(10,30,5),(30,30,5),(40,20,2),(30,0,0),(35,-5,-2),(40,0,0)};权因子:{1;0.5;2;1;2;2;1;2;0.5;1};节点向量:{0,0,0,1/8,2/8,3/8,4/8,5/8,6/8,7/8,1,1,1},曲线2的阶数、权因子及节点向量与曲线1相同,控制点为:{(0,0,2),(5,-6,0),(10,0,2),(-5,20,4),(10,33,7),(30,33,7),(45,20,4),(30,0,2),(35,-6,0),(40,0,2)}。
根据附图1所示方法整体流程,以AC双转台五轴机床为例,进行五轴双样条曲线插补速度规划,具体步骤为:
第一步 建立物理轴运动与刀具轨迹间关联关系:根据附图2中曲线1所示刀尖点运动轨迹曲线方程,取弧长步长δ s=0.05mm,利用公式(1)进行刀尖点运动轨迹等弧长离散,利用公式(2)计算刀尖点及刀轴矢量,根据AC双转台五轴机床的运动学变换,得到物理轴运动位置向量q,进而根据公式(3)获得物理轴运动位置对刀尖点轨迹弧长的一阶到三阶微分q s、q ss、q sss
第二步 确定速度敏感区间:根据公式(4),计算物理轴运动速度向量
Figure PCTCN2018071689-appb-000125
加速度向量
Figure PCTCN2018071689-appb-000126
及加加速度向量
Figure PCTCN2018071689-appb-000127
与q s、q ss、q sss间关系,设定五轴机床的X、Y、Z轴运动速度极限均为300mm/s,轴加速度极限均为1000mm/s 2,轴加加速度极限均为20000mm/s 3,A、C轴运动速度极限均为30rad/s,轴加速度极限均为100rad/s 2,轴加加速度极限均为2000rad/s 3,即
Figure PCTCN2018071689-appb-000128
Figure PCTCN2018071689-appb-000129
设定刀尖点运动切向速度极限v max=30mm/s,根据物理轴驱动性能极限条件,计算速度敏感区间参数集合,同时计算切向加速度极限a t,max、加加速度极限j t,max
第三步 确定各速度敏感区间许用进给速度:首先以物理轴驱动性能极限为约束条件,根据公式(7)计算各速度敏感区间初始许用速度值
Figure PCTCN2018071689-appb-000130
进而根据切向加速度、切向加加速度极限,基于双向扫描法,更新各速度敏感区间许用进给速度
Figure PCTCN2018071689-appb-000131
同时计算初始速升速过程切向加速度极限a b,max、最末降速过程加加速度极限a f,max、初始速升速过程切向加加速度极限j b,max、最末降速过程加加速度极限j f,max
第四步 升、降速起始点参数及相应速度值计算:根据发明内容中第四步内容,计算升、降速起始点参数及相应的进给速度集合{ur i,vu i},i=1,2,…,n;
第五步 各插补点参数及相应进给速度实时插补:首先判断当前插补点参数所属区间,其次根据发明内容中第五步内容计算当前插补点速度,进而根据公式(24)计算下一插补点参数;判断是否到达曲线终点,若未到达,返回第五步计算下一插补点进给速度,若到达,结束算法。
附图3所示为根据上述步骤最终规划的刀尖点运动进给速度,其中A轴表示样条曲线参数,B轴表示刀尖点运动进给速度,单位为mm/s;从附图3中可见,除部分过渡区域的平滑过渡外,所规划的五轴双样条曲线插补进给速度均保持恒定,这有利于协调加工效率与运行平稳性。
附图4所示为利用所规划进给速度加工获得的三个直线轴实际运动速度;其中A轴表示样条曲线参数,B轴表示直线轴运动速度值,单位为mm/s,曲线1为机床X轴运动速度,曲线2为机床Y轴运动速度,曲线3为机床Z轴运动速度;图中可见,各直线轴实际运动速度绝对值均小于直线轴运动速度极限设定值300mm/s。
附图5所示为利用所规划进给速度加工获得的两个旋转轴实际运动速度;其中A轴表示样条曲线参数,B轴表示旋转轴运动速度值,单位为rad/s,曲线1为机床A轴运动速度,曲线2为机床C轴运动速度;图中可见各旋转轴实际运动速度绝对值均小于旋转轴运动速度极限设定值30rad/s。
附图6所示为利用所规划进给速度加工获得的三个直线轴实际运动加速度,其中A轴表示样条曲线参数,B轴表示直线轴运动加速度值,单位为mm/s 2,曲线1为机床X轴运动加 速度,曲线2为机床Y轴运动加速度,曲线3为机床Z轴运动加速度;图中可见,各直线轴实际运动加速度绝对值均小于直线轴运动加速度极限设定值1000mm/s 2
附图7所示为利用所规划进给速度加工获得的两个旋转轴实际运动加速度,其中A轴表示样条曲线参数,B轴表示旋转轴运动速度值,单位为rad/s 2,曲线1为机床A轴运动加速度,曲线2为机床C轴运动加速度;图中可见,各旋转轴实际运动加速度绝对值均小于旋转轴运动加速度极限设定值100rad/s 2
附图8所示为利用所规划进给速度加工获得的三个直线轴实际运动加加速度,其中A轴表示样条曲线参数,B轴表示直线轴运动加加速度值,单位为mm/s 3,曲线1为机床X轴运动加加速度,曲线2为机床Y轴运动加加速度,曲线3为机床Z轴运动加加速度;图中可见,各直线轴实际运动加加速度绝对值均小于直线轴运动加加速度极限设定值20000mm/s 2
附图9所示为利用所规划进给速度加工获得的两个旋转轴实际运动加加速度,其中A轴表示样条曲线参数,B轴表示旋转轴运动速度值,单位为rad/s 3,曲线1为机床A轴运动加加速度,曲线2为机床C轴运动加加速度。图中可见,各旋转轴实际运动加加速度绝对值均小于旋转轴运动加加速度极限设定值2000rad/s 3
综上可见,所规划的五轴双样条曲线插补进给速度可以实现在曲线的大部分区间保持恒定,且能够满足各物理轴驱动性能极限约束。该方法以物理轴驱动性能极限为约束的速度敏感区间恒速五轴双样条曲线插补速度规划方法,协调五轴加工效率与运行平稳性、进而提高五轴数控机床性能。

Claims (1)

  1. 一种五轴双样条曲线插补速度规划方法,其特性在于,该方法在对刀尖点轨迹进行等弧长离散的基础上,计算各物理轴位置对弧长参数的一阶到三阶微分,从而获得物理轴运动与刀具轨迹间关联关系;以轴驱动性能极限条件为约束,以平衡加工运行平稳性和加工效率为目标,优化求取速度敏感区间;通过双向扫描,确定各速度敏感区间的速度值及升、降速起始点曲线参数,在敏感区间采用所确定的恒定进给速度,在非敏感区间利用S形加减速模式规划平滑进给速度;方法具体步骤如下:
    第一步建立物理轴运动与刀具轨迹间关联关系
    设待插补双样条曲线中的刀尖点运动轨迹曲线方程为C P=C P(u),刀轴上除刀尖外另一点运动轨迹曲线方程为C Q=C Q(u),首先对刀尖点运动轨迹曲线进行等弧长离散,设弧长步长为δ s,离散后第i个离散点对应的曲线参数为u d,i,则利用二阶泰勒级数展开,第i+1个离散点对应的曲线参数u d,i+1由递推公式(1)计算:
    Figure PCTCN2018071689-appb-100001
    其中,|| ||表示欧几里得范数,C′ P(u d,i)和C″ P(u d,i)分别为C P(u)对参数u在u d,i处的一阶和二阶导矢;
    令R=[R x,R y,R z] T表示刀尖点,O=[O x,O y,O z] T表示刀轴矢量,在得到离散点对应的曲线参数u d,i,i=1,2,…,N d后,N d表示离散点总数,计算离散后第i个刀尖点
    Figure PCTCN2018071689-appb-100002
    和第i个刀轴矢量O i=[O x,i,O y,i,O z,i] T
    Figure PCTCN2018071689-appb-100003
    利用五轴机床运动学变换,根据公式(2)获得的刀尖点和刀轴矢量,计算出五个物理轴运动位置,令q表示物理轴运动位置向量,且q为五行一列的向量,其中五个元素对应于机床的五个物理轴,将对应于第i个刀尖点和第i个刀轴矢量的第i个物理轴运动位置向量表示为q i,由此,计算物理轴位置对刀尖点轨迹弧长的一阶到三阶微分:
    Figure PCTCN2018071689-appb-100004
    其中,q s,i表示第i个刀尖点处物理轴运动位置向量对刀尖点轨迹弧长的一阶导矢,q ss,i表示第i个刀尖点处物理轴运动位置向量对刀尖点轨迹弧长的二阶导矢,q sss,i表示第i个刀尖点处物理轴运动位置向量对刀尖点轨迹弧长的三阶导矢,公式(3)即为物理轴运动与刀具轨迹间关联关系方程;
    第二步确定速度敏感区间
    依据微分原理,物理轴运动速度、加速度及加加速度与刀尖点运动切向速度、加速度及加加速度关系为:
    Figure PCTCN2018071689-appb-100005
    其中,
    Figure PCTCN2018071689-appb-100006
    分别为物理轴运动位置向量对时间的一阶、二阶、三阶导矢,即物理轴运动速度向量、加速度向量及加加速度向量;
    Figure PCTCN2018071689-appb-100007
    分别为刀尖点运动位置对时间的一阶、二阶、三阶微分,即刀尖点运动速度、切向加速度及切向加加速度;
    设物理轴运动速度极限为
    Figure PCTCN2018071689-appb-100008
    物理轴运动加速度极限为
    Figure PCTCN2018071689-appb-100009
    物理轴运动加加速度极限为
    Figure PCTCN2018071689-appb-100010
    设定的刀尖点运动速度极限为v max,首先令刀尖点运动切向加速度极限a t,max等于
    Figure PCTCN2018071689-appb-100011
    中三个直线运动轴运动加速度极限的最小值、令刀尖点运动切向加加速度极限j t,max等于
    Figure PCTCN2018071689-appb-100012
    中三个直线运动轴运动加加速度极限的最小值,其次,以平衡加工效率和运行平稳度为目标,优化a t,max和j t,max取值并确定速度敏感区间;定义在刀尖点以最大速度、加速度和加加速度运动的情况下,各物理轴运动速度、加速度和加加速度可能超出相应的极限约束条件的区间为速度敏感区间,根据公式(4),可得:
    Figure PCTCN2018071689-appb-100013
    据此,扫描各刀尖点运动轨迹离散点,将满足不等式|q s,i|v max>q max
    Figure PCTCN2018071689-appb-100014
    之一的离散点作为速度敏感区间内的点,设得到的速度敏感区间总段数为N sr,第k段速度敏感区间的起始、结束位置对应的离散点序号分别为n s,k和n e,k,则速度敏感区间对应的离散点序号集合可表示为{[n s,k,n e,k]},k=1,2,…,N sr;因此,刀尖点运动轨迹曲线上速度敏感区间的总弧长l sr为:
    Figure PCTCN2018071689-appb-100015
    设刀尖点运动轨迹曲线的总弧长为l t,若l sr<l t/2,说明运动轨迹上大部分区域属于非速度敏感区间,以最大速度v max进行恒速运行,即可同时保证运行平稳和高效率加工,故此时规划的速度敏感区间较优;反之,若l sr>l t/2,说明运动轨迹上大部分区域属于速度敏感区间,需以区间内最小许用速度进行恒速运行,虽然可满足运行平稳,但加工效率过低,故此时对a t,max和j t,max的取值进行优化,进而优化速度敏感区间,具体方法为,在零到
    Figure PCTCN2018071689-appb-100016
    中三个直线运动轴运动加速度极限的最小值之间以及零到
    Figure PCTCN2018071689-appb-100017
    中三个直线运动轴运动加加速度极限的最小值之间,利用二分法寻找合适的a t,max和j t,max取值,使得对应的速度敏感区间总弧长lsr等于刀尖点运动轨迹曲线总弧长l t的一半,即l sr=l t/2;通过上述步骤,得到最终的速度敏感区间曲线参数集合表示为{[u s,k,u e,k]},k=1,2,…,N sr
    第三步确定各速度敏感区间许用进给速度
    首先,以物理轴驱动性能为约束计算各速度敏感区间初始许用速度值;为保证刀尖点进给运动平稳,同时提高计算效率,在速度敏感区间内,规划恒定的进给速度,此时,切向加速度
    Figure PCTCN2018071689-appb-100018
    切向加加速度
    Figure PCTCN2018071689-appb-100019
    均为零,根据公式(4),得第k个速度敏感区间的初始许用速度值
    Figure PCTCN2018071689-appb-100020
    为:
    Figure PCTCN2018071689-appb-100021
    其中,min()表示取最小值函数;
    其次,以切向加速度、加加速度为约束,在S形加减速模式下更新速度敏感区间许用速度值;当切向加速度、加加速度极限分别为a t,max和j t,max时,在S形加减速模式下,从起始速度
    Figure PCTCN2018071689-appb-100022
    加、减速到结束速度
    Figure PCTCN2018071689-appb-100023
    过程所需要的位移值
    Figure PCTCN2018071689-appb-100024
    为:
    Figure PCTCN2018071689-appb-100025
    其中,加减速过程最大加速度值a max=j t,maxt 1,加加/减速时间t 1,恒加/减速时间t 2,减加/减速时间t 3为:
    Figure PCTCN2018071689-appb-100026
    Figure PCTCN2018071689-appb-100027
    t 3=t 1
    通过双向扫描更新速度敏感区间许用速度值
    Figure PCTCN2018071689-appb-100028
    具体过程如下:
    从k=N sr到k=1进行逆向扫描,规划降速过程各速度敏感区间许用速度,其流程为:
    1)令k=N sr
    2)若k=N sr,判断n e,k=N d是否成立,若成立转第3)步,若不成立,转第5)步;若k≠N sr,转第6)步;
    3)此时,插补曲线的结束区域属于速度敏感区间,利用公式(8)计算从起始速度
    Figure PCTCN2018071689-appb-100029
    减速到0所需要的位移值
    Figure PCTCN2018071689-appb-100030
    及该速度敏感区间弧长l k
    l k=δ d·(n e,k-n s,k) (10)
    Figure PCTCN2018071689-appb-100031
    直接转第4)步,否则,在0到
    Figure PCTCN2018071689-appb-100032
    之间利用二分法寻找速度值
    Figure PCTCN2018071689-appb-100033
    使得
    Figure PCTCN2018071689-appb-100034
    Figure PCTCN2018071689-appb-100035
    更新该速度敏感区间许用速度值
    Figure PCTCN2018071689-appb-100036
    并重新计算
    Figure PCTCN2018071689-appb-100037
    转第4)步;
    4)因当插补曲线的结束区域属于速度敏感区间时,最终降速过程必须在速度敏感区间内完成,故判断该降速过程中是否出现超出物理轴驱动性能极限约束的情况,计算降速过程所经历的离散点数量n f
    Figure PCTCN2018071689-appb-100038
    其中int()表示向下取整函数;根据S形加减速过程位移与切向速度、加速度、加加速度关系,反求第N sr个速度敏感区间内降速过程各离散点处刀尖点速度
    Figure PCTCN2018071689-appb-100039
    切向加速度
    Figure PCTCN2018071689-appb-100040
    切向加加速度
    Figure PCTCN2018071689-appb-100041
    并代入公式(4),求得第N sr个速度敏感区间内降速过程各离散点处所需轴速度向量
    Figure PCTCN2018071689-appb-100042
    轴加速度向量
    Figure PCTCN2018071689-appb-100043
    轴加加速度向量
    Figure PCTCN2018071689-appb-100044
    j∈{n d-n f,…,n d},计算最末降速过程最大轴驱动极限与所需轴运动参数比值的最小值K f
    Figure PCTCN2018071689-appb-100045
    比较K f与1的大小,确定第N sr个速度敏感区间内降速过程切向速度、加速度、加加速 度值调整比例K f,t
    K f,t=min(K f,1) (13)
    令第N sr个速度敏感区间内降速过程许用切向加速度
    Figure PCTCN2018071689-appb-100046
    第N sr个速度敏感区间内降速过程许用切向加加速度
    Figure PCTCN2018071689-appb-100047
    更新该速度敏感区间许用速度值
    Figure PCTCN2018071689-appb-100048
    5)当k=N sr且n e,k≠N d时,说明最后一个速度敏感区间结束位置与插补曲线结束间存在非速度敏感区间,因此,在该非速度敏感区间内规划降速过程;利用公式(8)计算从起始速度
    Figure PCTCN2018071689-appb-100049
    减速到0所需要的位移值
    Figure PCTCN2018071689-appb-100050
    同时计算最末非速度敏感区间弧长l f
    l f=δ d·(N d-n e,k) (14)
    Figure PCTCN2018071689-appb-100051
    在0到
    Figure PCTCN2018071689-appb-100052
    之间利用二分法寻找速度值
    Figure PCTCN2018071689-appb-100053
    使得
    Figure PCTCN2018071689-appb-100054
    Figure PCTCN2018071689-appb-100055
    更新该速度敏感区间许用速度值
    Figure PCTCN2018071689-appb-100056
    转第7)步;
    6)判断是否为减速过程,若
    Figure PCTCN2018071689-appb-100057
    则为升速过程,转第7)步,否则,计算从
    Figure PCTCN2018071689-appb-100058
    降速到
    Figure PCTCN2018071689-appb-100059
    所需要的位移值
    Figure PCTCN2018071689-appb-100060
    及第k个非速度敏感区间弧长l r,k
    l r,k=δ d·(n s,k+1-n e,k) (15)
    Figure PCTCN2018071689-appb-100061
    时,在0到
    Figure PCTCN2018071689-appb-100062
    之间利用二分法寻找速度值
    Figure PCTCN2018071689-appb-100063
    使得
    Figure PCTCN2018071689-appb-100064
    Figure PCTCN2018071689-appb-100065
    更新该速度敏感区间许用速度值
    Figure PCTCN2018071689-appb-100066
    转第7)步;
    7)若k=1,结束,否则,令k=k-1,转第2)步;
    从k=1到k=N sr进行正向扫描,规划升速过程各速度敏感区间许用速度,其流程为:
    1)令k=1;
    2)若k=1,判断n s,k=1是否成立,若成立转第3)步,若不成立,转第5)步;若k≠1,转第6)步;
    3)此时,插补曲线的起始区域属于速度敏感区间,利用公式(8)计算从起始速度0升速到
    Figure PCTCN2018071689-appb-100067
    所需要的位移值
    Figure PCTCN2018071689-appb-100068
    利用公式(10)计算该速度敏感区间弧长l k
    Figure PCTCN2018071689-appb-100069
    直接转第4)步,否则,在0到
    Figure PCTCN2018071689-appb-100070
    之间利用二分法寻找速度 值
    Figure PCTCN2018071689-appb-100071
    使得
    Figure PCTCN2018071689-appb-100072
    Figure PCTCN2018071689-appb-100073
    更新该速度敏感区间许用速度值
    Figure PCTCN2018071689-appb-100074
    并重新计算
    Figure PCTCN2018071689-appb-100075
    转第4)步;
    4)因当插补曲线的起始区域属于速度敏感区间时,初始升速过程必须在速度敏感区间内完成,故判断该升速过程中是否出现超出物理轴驱动性能极限约束的情况,计算升速过程所经历的离散点数量n b
    Figure PCTCN2018071689-appb-100076
    根据S形加减速过程位移与切向速度、加速度、加加速度关系,反求第1个速度敏感区间内升速过程各离散点处刀尖点速度
    Figure PCTCN2018071689-appb-100077
    切向加速度
    Figure PCTCN2018071689-appb-100078
    切向加加速度
    Figure PCTCN2018071689-appb-100079
    j∈{1,…,n b},并代入公式(4),求得第1个速度敏感区间内升速过程各离散点处所需轴速度向量
    Figure PCTCN2018071689-appb-100080
    轴加速度向量
    Figure PCTCN2018071689-appb-100081
    轴加加速度向量
    Figure PCTCN2018071689-appb-100082
    j∈{1,…,n b},计算初始升速过程最大轴驱动极限与所需轴运动参数比值的最小值K b
    Figure PCTCN2018071689-appb-100083
    比较K b与1的大小,确定第1个速度敏感区间内升速过程切向速度、加速度、加加速度值调整比例K b,t
    K b,t=min(K b,1) (18)
    令第1个速度敏感区间内升速过程许用切向加速度
    Figure PCTCN2018071689-appb-100084
    第1个速度敏感区间内升速过程许用切向加加速度
    Figure PCTCN2018071689-appb-100085
    更新该速度敏感区间许用速度值
    Figure PCTCN2018071689-appb-100086
    5)当k=1且n s,k≠1时,说明第1个速度敏感区间起始位置与插补曲线起始位置之间存在非速度敏感区间,因此,在该非速度敏感区间内规划升速过程;利用公式(8)计算从起始速度0升速到
    Figure PCTCN2018071689-appb-100087
    所需要的位移值
    Figure PCTCN2018071689-appb-100088
    同时利用公式(15)计算第k个非速度敏感区间弧 长l r,k
    Figure PCTCN2018071689-appb-100089
    在0到
    Figure PCTCN2018071689-appb-100090
    之间利用二分法寻找速度值
    Figure PCTCN2018071689-appb-100091
    使得
    Figure PCTCN2018071689-appb-100092
    Figure PCTCN2018071689-appb-100093
    更新该速度敏感区间许用速度值
    Figure PCTCN2018071689-appb-100094
    转第7)步;
    6)判断是否为升速过程,若
    Figure PCTCN2018071689-appb-100095
    则为降速过程,转第7)步,否则,计算从
    Figure PCTCN2018071689-appb-100096
    升速到
    Figure PCTCN2018071689-appb-100097
    所需要的位移值
    Figure PCTCN2018071689-appb-100098
    及第k个非速度敏感区间弧长l r,k
    Figure PCTCN2018071689-appb-100099
    时,在0到
    Figure PCTCN2018071689-appb-100100
    之间利用二分法寻找速度值
    Figure PCTCN2018071689-appb-100101
    使得
    Figure PCTCN2018071689-appb-100102
    Figure PCTCN2018071689-appb-100103
    更新该速度敏感区间许用速度值
    Figure PCTCN2018071689-appb-100104
    转第7)步;
    7)若k=N sr-1,转第8)步,否则,令k=k+1,转第2)步;
    8)当n e,k=N d且K f,t<1时,判断第N sr个速度敏感区间的许用速度
    Figure PCTCN2018071689-appb-100105
    是否在升速过程速度规划过程中被更新,若是,计算更新后速度与更新前速度比值K ba,令K f,t=K ba·K f,t,再次更新第N sr个速度敏感区间内降速过程许用切向加速度
    Figure PCTCN2018071689-appb-100106
    第N sr个速度敏感区间内降速过程许用切向加加速度
    Figure PCTCN2018071689-appb-100107
    结束双向扫描;
    经过上述逆向扫描降速过程进给速度规划和正向扫描升速过程进给速度规划,得到最终更新的进给速度值
    Figure PCTCN2018071689-appb-100108
    即为满足物理轴驱动性能约束的第k个速度敏感区间进给速度最终规划值;
    第四步升、降速起始点参数及相应速度值计算
    判断非速度敏感区间弧长l r,k是否大于进给速度从第k个速度敏感区间的许用速度
    Figure PCTCN2018071689-appb-100109
    增加到设定的刀尖点运动进给速度极限v max再降低到第k+1个速度敏感区间的许用速度
    Figure PCTCN2018071689-appb-100110
    所需位移之和,即判断不等式(19)是否成立:
    Figure PCTCN2018071689-appb-100111
    若不等式(19)成立,从第k个到第k+1个速度敏感区间之间执行升速(从
    Figure PCTCN2018071689-appb-100112
    增加到v max)和降速(从v max降低至
    Figure PCTCN2018071689-appb-100113
    )两个过程;升速起始点参数为u e,k,相对应的进给速度值为
    Figure PCTCN2018071689-appb-100114
    降速起始点参数u dc为:
    Figure PCTCN2018071689-appb-100115
    降速结束点对应的进给速度为v max
    若不等式(19)不成立,为保证进给速度轮廓平滑,第k个到第k+1个速度敏感区间之间仅执行升速或降速过程;若
    Figure PCTCN2018071689-appb-100116
    执行升速过程,升速起始点参数为u e,k,相对应的进给速度值为
    Figure PCTCN2018071689-appb-100117
    Figure PCTCN2018071689-appb-100118
    执行降速过程,降速起始点参数u dc为:
    Figure PCTCN2018071689-appb-100119
    该降速起始点相对应的进给速度值为
    Figure PCTCN2018071689-appb-100120
    设经上述步骤获得的升、降速起始点共n个,将升、降速起始点参数及相应进给速度集合记为{ur i,vu i},i=1,2,…,n,其中ur i为第i个升/降速起始点参数,vu i为第i个升/降速起始点速度;
    第五步各插补点参数及相应进给速度实时插补
    在实时插补过程中,判断当前插补点曲线参数u j所在的参数区间[ur i,ur i+1],计算t 1、t 2、t 3
    Figure PCTCN2018071689-appb-100121
    Figure PCTCN2018071689-appb-100122
    t 3=t 1
    其中,当i=1时,a t,m=a b,max、j t,m=j b,max,当i=n时,a t,m=a f,max、j t,m=j f,max,否则a t,m=a t,max、j t,m=j t,max
    当插补参数进入该区间的总时间t<t 1+t 2+t 3时,当前插补点进给速度v j为:
    Figure PCTCN2018071689-appb-100123
    其中,a m=j f,max·t 1;当插补参数进入该区间的总时间t≥t 1+t 2+t 3时,当前插补点进给速度v j=vu i+1;根据二阶泰勒展开法计算下一插补点参数u j+1
    Figure PCTCN2018071689-appb-100124
    其中T为插补周期;判断是否到达曲线终点,若到达终点,则结束插补,否则,令j=j+1,重新执行第五步;据此,实现满足物理轴驱动能力极限约束的五轴双样条曲线插补速度规划。
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