CN103056772A - Compensation method of grinder rigidity based on negative flexibility principle - Google Patents

Abstract

The invention discloses a compensation method of grinder rigidity based on a negative flexibility principle, belongs to the technical field of accurate grinding and mainly solves the elastic deformation problem caused by shortage of grinder rigidity during grinding. The compensation of the grinding system rigidity is achieved by utilizing a negative flexibility controllable workbench which is provided with a piezoceramic driver and a flexible mechanism. The compensation method of the grinder rigidity based on the negative flexibility principle comprises a, measuring normal rigidity of a grinder on a real grinding surface and rigidity of two corners which rotate along axial directions of two axes which are perpendicular to each other; b, analyzing mechanical characteristics of a grinding system and building a negative flexibility outputting model of a workbench; and c, establishing a corresponding feedback control system and achieving online compensation of the grinder rigidity. The compensation method of the grinder rigidity based on the negative flexibility principle has the advantages of improving grinding technology, improving grinding efficiency, having important application value in guaranteeing material quantity for grinding, smoothness of grinding surfaces and size accuracy of a workpiece and playing an important role in grinding hard and brittle materials such as engineering ceramics.

Description

A kind of grinding machine rigidity compensation method based on negative flexibility principle

Technical field

The invention belongs to the accurate grinding processing technique field, relate to a kind of grinding machine rigidity compensation method based on negative flexibility principle, mainly solve the strain that is caused by grinding machine rigidity deficiency and can't accurately control grinding dosage to realize the problem of machine parts'precise grinding.

Background technology

Grinding is a kind of topmost precision optical machinery processing mode, can obtain very high surface quality of workpieces by this processing method.But in Grinding Process, the strain of lathe is difficult to avoid, this so that the machining accuracy of part and surface quality be difficult to effectively be guaranteed.This invention is except being used for the grinding of common metal material (such as structural steel, tool steel, mould steel etc.), and the grinding of hard brittle material (such as engineering ceramics, glass etc.) is the main application of its one.

Because the hard fragility of engineering ceramic material, the impact of the factors such as the large and the rigidity of machine tool of grinding force ratio, the very large difficulty of accurate grinding processing existence of engineering ceramic material.For guaranteeing the grinding in the ductile mode of engineering ceramics, need to be controlled at micron order to grinding dosage.In Grinding Process, can produce interaction force between emery wheel and the workpiece, add the grinding system insufficient rigidity, cause the strain of grinding system that the engineering ceramics quality is had a significant impact.In order to reduce the workpiece machining error that is caused by strain, improve grinding quality, need to realize online rigidity compensation to grinding system.

Adopted the controlled accurate grinding workbench of negative stiffness of a kind of parallel 3-DOF among the patent ZL201020641069.X (a kind of rigidity compensating mechanism of grinding technology system based on negative rigidity principle) to realize among the present invention.

Summary of the invention

The object of the present invention is to provide a kind of grinding machine rigidity compensation method based on negative flexibility principle, mainly solve the strain that is caused by grinding machine rigidity deficiency and can't accurately control grinding dosage to realize the problem of machine parts'precise grinding.

A kind of grinding machine rigidity compensation method based on negative flexibility principle, utilize a kind of Three Degree Of Freedom flexibility compensation mechanism that is driven by 3 piezoelectric ceramic actuators to compensate the rigidity of grinding machine, it is characterized in that measuring in real time the grinding force between grinding process medium plain emery wheel and the workpiece, export to compensate the strain of grinding machine in the grinding process according to the negative flexibility of the size adjustment flexibility compensation mechanism of grinding force, the method may further comprise the steps:

A. measure rigidity and the rotation stiffness of two orthogonal 2 axial-rotations in grinding face respectively of grinding machine on the normal direction of actual grinding face;

At first measure the quiet rigidity of grinding machine, comprise the stiffness K on the normal direction of grinding face _Z, the rotation stiffness K of two orthogonal 2 axial-rotations in grinding face respectively _αAnd K _β

$K_Z=\frac{\mathrm{\Δ}{F}_z}{\mathrm{\ΔZ}}---\left(1\right)$

$K_{\mathrm{\α}}=\frac{\mathrm{\Δ}{M}_X}{\mathrm{\Δ\α}}---\left(2\right)$

$K_{\mathrm{\β}}=\frac{\mathrm{\Δ}{M}_Y}{\mathrm{\Δ\β}}---\left(3\right)$

Wherein Z axis is the normal direction on grinding plane, and X, Y-axis form a rectangular coordinate system perpendicular to Z axis in the grinding plane; Δ F _ZThe recruitment of the load that applies for the normal orientation at grinding face, Δ Z is the increment of the deflection on the loading direction in loading; Δ M _XBe the recruitment of the moment of torsion that rotates around X-axis that applies in X-direction, Δ α is for loading medium plain emery wheel around the increment of the corner of X-direction; Δ M _YBe the recruitment of the moment of torsion that rotates around Y-axis that applies in Y direction, Δ β is for loading medium plain emery wheel around the increment of the corner of Y direction.

B. analyze the mechanical characteristic of negative flexibility Controllable Worktable, set up the negative flexibility compensation model of grinding system;

The Three Degree Of Freedom flexibility compensation mechanism of placing at Grinder bench is the compliant mechanism that piezoelectric ceramic actuator, moving platform, flex link, base, main body and the flexible ring by 3 parallel connections consists of, and can adjust by the elongation of adjusting piezoelectric ceramic actuator the flexibility output of compliant mechanism; When being subject to grinding force, the flexibility compensation mechanism that workpiece is installed does the time spent, the grinding force size that gets according to Real-time Measuring is adjusted the elongation of each piezoelectric ceramic actuator on the workbench, make the flexibility compensation mechanism produce a distortion with this grinding force opposite direction and export, the elongation of adjusting in real time piezoelectric ceramic actuator keeps the ratio of this distortion and grinding force namely to bear the flexibility opposite sign but equal magnitude of flexibility and grinding machine.

When workbench is subject to grinding force F=[F _Z, M _X, M _Y] ^TDo the time spent, workbench is by adjusting the elongation Δ L of each piezoelectric ceramic actuator ₁, Δ L ₂, Δ L ₃Thereby, drive the flexible working platform and produce a deflection G with the opposite direction of this power _W

G _W=[ΔZ,Δα,Δβ] ^T=g(ΔL ₁,ΔL ₂,ΔL ₃) （4）

In order to compensate the strain G of grinding machine _M, need to guarantee the following formula establishment.

$G_W=\frac{F}{K}=\left[\begin{array}{c}\mathrm{\ΔZ}\\ \mathrm{\Δ\α}\\ \mathrm{\Δ\β}\end{array}\right]=-\left[\begin{array}{c}{F}_Z/K_Z\\ M_X/K_{\mathrm{\α}}\\ M_Y/K_{\mathrm{\β}}\end{array}\right]---\left(5\right)$

G in the formula (5) _WRealize that by the elongation of adjusting piezoelectric ceramic actuator grinding force F Real-time Measuring in the grinding process of part gets.Formula (4) is carried out the elongation that corresponding abbreviation conversion can obtain piezoelectric ceramic actuator

[ΔL ₁,ΔL ₂,ΔL ₃] ^T=g ^-1(ΔZ,Δα,Δβ) （6）

C. build corresponding feedback control system, measure the size of grinding force in the grinding process, realize the online compensation of grinding machine rigidity.This part action mainly is building of hardware platform and controls writing of software.Feedback control system comprises that grinding force measurement mechanism, signal processing and analysis system, control instruction actuating unit are piezoelectric ceramic actuator etc.

Technique effect of the present invention is embodied in: the present invention compensates the flexibility (rigidity) of flat surface grinding system, change in the little situation at the relative position between emery wheel and the workpiece, the rigidity of grinding machine can be regarded definite value as, do not change with grinding force, so compensation process is realized easily; The present invention adopts negative flexibility controllable mechanism, comes the elongation of On-line Control piezoelectric ceramic actuator by real-time measurement grinding force, thereby adjusts the negative flexibility output of workbench in Grinding Process; The present invention can realize three rigidity compensation on the direction, and the strain on these three directions is the main distortion that affects grinding surface quality; The present invention can the Effective Raise working (machining) efficiency, does not need just to cut and can realize accurate grinding to hard brittle material (such as engineering ceramics) through the multiple reversal regrinding, guarantees grinding depth, improves suface processing quality and working (machining) efficiency.

Description of drawings:

The definition of rigidity compensation coordinate system when Fig. 1 adopts vertical surface grinding machine to carry out cross grinding;

The definition of rigidity compensation coordinate system when Fig. 2 adopts horizontal surface grinder to carry out peripheral milling;

The structure diagram of the negative flexibility Controllable Worktable that Fig. 3 the present invention adopts;

The local structural graph of the negative flexibility Controllable Worktable of Fig. 4;

Fig. 5 the present invention uses schematic diagram in part processing;

Shown in the figure: 1 base, 2 times flexible ring, flexible ring on 3,4 main bodys, 5 moving platforms, 6 flex links, 7 piezoelectric ceramic actuators, 8 strain gauge adhesion positions, 9 emery wheels, 10 workpiece, 11 negative flexibility Controllable Worktables, 12 Grinder bench, 13 Piezoelectric Driving power supplys, 14 grinding force measurement mechanisms, 15 computers.

The specific embodiment:

The present invention is a kind of grinding machine rigidity compensation method based on negative flexibility principle.Before the method is implemented, at first need to set up rigidity compensation coordinate system, for the definition of the grinding plane X Y plane of vertical surface grinding machine and horizontal surface grinder and normal direction respectively shown in OXYZ coordinate system among Fig. 1 and Fig. 2.The main strain error that affects grinding surface quality is the strain of Z-direction and around the corner distortion of X, Y-axis, therefore for the purpose of the present invention, can adopt as shown in Figure 3 and Figure 4 negative flexibility Controllable Worktable to realize the compensation of grinding machine rigidity.The overall dimensions of the workbench that adopts (Fig. 3) is Φ 130 * 145mm ³, the parameter of piezoelectric ceramic actuator (7) is: maximum thrust 3000N, axial rigidity 200N/ μ m.Moving platform 5 lower surfaces are bolted by three fulcrums and upper flexible ring 3 and flex link 6.Upper flexible ring 3 can be carried out the motion control of three direction frees degree simultaneously, and it is fixed on three extended positions in main body 4 outer rings, only uses in the present invention the lifting that the vertical direction one degree of freedom realizes moving platform 5.Flex link 6 can prevent that excessive Moment is on piezoelectric ceramic actuator.Piezoelectric ceramic actuator 7 is fixed on the lower flexible ring 2, is bolted, and upper end and connector 6 are threaded connection.Be pasted with foil gauge 8 to measure the piezoelectric actuator power output at the base 1 that is fixedly connected with both sides, main body 4 position on the lower flexible ring 2.

As shown in Figure 5, negative flexibility Controllable Worktable 11 is fixed on the Grinder bench 12, and negative flexibility Controllable Worktable 11 upper surfaces are installed workpiece 10.Piezoelectric ceramic actuator 7 is connected with foil gauge and is connected with the grinding force measurement mechanism by Piezoelectric Driving power supply 13 respectively is that deformeter is connected with computer 15.The output voltage of computer 15 control Piezoelectric Driving power supplys 13 drives piezoelectric ceramic actuator 7 elongations, and piezoelectric ceramic actuator 7 has feedback control system, and its elongation can accurately control to 0.01 μ m level.By the elongation of three piezoelectric ceramic actuators 7 of adjusted in concert, simultaneously piezoelectric ceramic actuator 7 feeds back to computer to elongation.Measured simultaneously the strain value of lower flexible ring 2 by foil gauge 8, input computers through grinding force measurement mechanism 14, thereby obtain the power output F=[F of piezoelectric ceramic actuator according to the relation of strain and power _Z, M _X, M _Y] ^TThen F substitution formula (5) is obtained the attitude control target [Δ Z, Δ α, Δ β] of moving platform (5) ^T, the rigidity value K of lathe in the formula (5) _Z, K _αAnd K _βBe that lathe is surveyed the inherent characteristic parameter, can directly measure according to formula (1)～formula (3).

$K_Z=\frac{\mathrm{\Δ}{F}_z}{\mathrm{\ΔZ}}---\left(1\right)$

$K_{\mathrm{\α}}=\frac{\mathrm{\Δ}{M}_X}{\mathrm{\Δ\α}}---\left(2\right)$

$K_{\mathrm{\β}}=\frac{\mathrm{\Δ}{M}_Y}{\mathrm{\Δ\β}}---\left(3\right)$

$G_W=\frac{F}{K}=\left[\begin{array}{c}\mathrm{\ΔZ}\\ \mathrm{\Δ\α}\\ \mathrm{\Δ\β}\end{array}\right]=-\left[\begin{array}{c}{F}_Z/K_Z\\ M_X/K_{\mathrm{\α}}\\ M_Y/K_{\mathrm{\β}}\end{array}\right]---\left(5\right)$

[ΔL ₁,ΔL ₂,ΔL ₃] ^T=g ^-1(ΔZ,Δα,Δβ) （6）

Calculate at last elongation [the Δ L of piezoelectric ceramic actuator (7) according to formula (6) ₁, Δ L ₂, Δ L ₃] ^TThereby concern to realize negative stiffness effects according to output shift quantity and power output, the strain that the compensation manufacturing process system causes because of the rigidity deficiency, realization regulates and control to compensate the not enough elastic deformation amount who produces of manufacturing process system rigidity to the negative stiffness of the rigidity controllable parts of structure.

Claims (3)

1. grinding machine rigidity compensation method based on negative flexibility principle, it compensates the rigidity of grinding machine based on a kind of negative flexibility Controllable Worktable of the Three Degree Of Freedom as the flexibility compensation mechanism that is driven by 3 piezoelectric ceramic actuators, the grinding force measurement mechanism links to each other with grinding machine, the input and output of signal processing and analysis system connect respectively grinding force measurement mechanism and Three Degree Of Freedom flexibility compensation mechanism, it is characterized in that: measure in real time the grinding force between grinding process medium plain emery wheel and the workpiece, export to compensate the strain of grinding machine in the grinding process according to the negative flexibility of the size adjustment flexibility compensation mechanism of grinding force, the method may further comprise the steps:

A. measure rigidity and the rotation stiffness of two orthogonal 2 axial-rotations in grinding face respectively of grinding machine on the normal direction of actual grinding face;

At first measure the quiet rigidity of grinding machine, comprise the stiffness K on the normal direction of grinding face _Z, the rotation stiffness K of two orthogonal 2 axial-rotations in grinding face respectively _αAnd K _β

$K_Z=\frac{\mathrm{\Δ}{F}_z}{\mathrm{\ΔZ}}---\left(1\right)$

$K_{\mathrm{\α}}=\frac{\mathrm{\Δ}{M}_X}{\mathrm{\Δ\α}}---\left(2\right)$

$K_{\mathrm{\β}}=\frac{\mathrm{\Δ}{M}_Y}{\mathrm{\Δ\β}}---\left(3\right)$

Wherein Z axis is the normal direction on grinding plane, and X, Y-axis form a rectangular coordinate system perpendicular to Z axis in the grinding plane; Δ F _ZThe recruitment of the load that applies for the normal orientation at grinding face, Δ Z is the increment of the deflection on the loading direction in loading; Δ M _XBe the recruitment of the moment of torsion that rotates around X-axis that applies in X-direction, Δ α is for loading medium plain emery wheel around the increment of the corner of X-direction; Δ M _YBe the recruitment of the moment of torsion that rotates around Y-axis that applies in Y direction, Δ β is for loading medium plain emery wheel around the increment of the corner of Y direction;

B. analyze the mechanical characteristic of negative flexibility Controllable Worktable, set up the negative flexibility compensation model of grinding system;

The Three Degree Of Freedom flexibility compensation mechanism of placing at Grinder bench is the compliant mechanism that piezoelectric ceramic actuator, moving platform, flex link, base, main body and the flexible ring by 3 parallel connections consists of, and can adjust by the elongation of adjusting piezoelectric ceramic actuator the flexibility output of compliant mechanism; When being subject to grinding force, the flexibility compensation mechanism that workpiece is installed does the time spent, the grinding force size that gets according to Real-time Measuring is adjusted the elongation of each piezoelectric ceramic actuator on the workbench, make the flexibility compensation mechanism produce a distortion with this grinding force opposite direction and export, the elongation of adjusting in real time piezoelectric ceramic actuator keeps the ratio of this distortion and grinding force namely to bear the flexibility opposite sign but equal magnitude of flexibility and grinding machine;

When workbench is subject to grinding force F=[F _Z, M _X, M _Y] ^TDo the time spent, workbench is by adjusting the elongation Δ L of each piezoelectric ceramic actuator ₁, Δ L ₂, Δ L ₃Thereby, drive the flexible working platform and produce a deflection G with the opposite direction of this power _W

G _W=[ΔZ,Δα,Δβ] ^T=g(ΔL ₁,ΔL ₂,ΔL ₃) （4）

In order to compensate the strain G of grinding machine _M, need to guarantee the following formula establishment;

$G_W=\frac{F}{K}=\left[\begin{array}{c}\mathrm{\ΔZ}\\ \mathrm{\Δ\α}\\ \mathrm{\Δ\β}\end{array}\right]=-\left[\begin{array}{c}{F}_Z/K_Z\\ M_X/K_{\mathrm{\α}}\\ M_Y/K_{\mathrm{\β}}\end{array}\right]---\left(5\right)$

G in the formula (5) _WRealize that by the elongation of adjusting piezoelectric ceramic actuator grinding force F Real-time Measuring in the grinding process of part gets; Formula (4) is carried out the elongation that corresponding abbreviation conversion can obtain piezoelectric ceramic actuator

[ΔL ₁,ΔL ₂,ΔL ₃] ^T=g ^-1(ΔZ,Δα,Δβ) （6）。

2. according to claims 1 described a kind of grinding machine rigidity compensation method based on negative flexibility principle, it is characterized in that: measure in real time the size of grinding force, the rigidity of grinding machine is carried out online compensation.Grinding force is in continuous variation in the compensation process, and the rigidity of grinding machine is constant, and the negative flexibility of workbench output then keeps and grinding machine flexibility opposite sign but equal magnitude it by piezoelectric ceramic actuator adjustment.

3. according to claims 1 described a kind of grinding machine rigidity compensation method based on negative rigidity principle, it is characterized in that: negative flexibility Controllable Worktable drives to guarantee that by piezoelectric ceramic actuator workbench has enough rigidity and precise Positioning Control.

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