Summary of the invention:
Technical problem to be solved by this invention is to avoid existing weak point in the above-mentioned prior art, and a kind of single layer structure six-freedom micro displacement worktable and parallel control mode thereof are provided, and is used to realize accurate measurement and precision positioning.
The technical scheme that technical solution problem of the present invention is adopted is:
The design feature of six-freedom micro displacement worktable of the present invention is: adopt single layer structure, connect with eight bar symmetrical manner by the Piezoelectric Driving bar, the outer end of Piezoelectric Driving bar A-a, B-b, C-c, D-d, E-e, F-f, G-g, H-h links to each other with fixed station by flexible hinge A, B, C, D, E, F, G, H, and the inner links to each other with micropositioner by flexible hinge a, b, c, d, e, f, g, h.
The characteristics of control mode of the present invention are to adopt the parallel control mode, described parallel control mode is the length variations by eight Piezoelectric Driving bars of parallel control, the synchronized movement of a plurality of frees degree of workbench is carried out, and the independence that is controlled to be of each drive rod combines with local correlation.
The Piezoelectric Driving bar that is adopted among the present invention is flexible under applied voltage, can change the length of piezoelectric actuator by control applied voltage value.Utilize the variation of eight symmetrically arranged Piezoelectric Driving bars on length,, can realize the motion of the six degree of freedom of micropositioner in conjunction with the distortion of flexible hinge.Whole workbench is except the flexible hinge place produces distortion, and all the other all regard rigid body as.
Compared with the prior art, beneficial effect of the present invention is embodied in:
1, six-freedom worktable of the present invention adopts single layer structure, its with respect to sandwich construction have volume little, simple in structure, be easy to assemble, advantage that cumulative errors are little.
2, the present invention adopts Piezoelectric Driving bar eight pole pairs to claim structure, the independence that is controlled to be of each drive rod combines with local correlation, promptly realize the drive rod difference that each single dof mobility of workbench need be controlled, control two bars that have, control four bars that have, multifreedom motion is realized by each single dof mobility of Synchronization Control.This structure can be simplified driving control model, the six bar arrangement works platforms that are used for the robot motion are relatively controlled simply and are easy to improve kinematic accuracy and realize microminiaturized, the motion parallel control of each piezoelectric actuator, the motion of each free degree can be carried out synchronously, can reduce the required time of workbench orientation adjustment greatly like this, improve and measure speed and efficient.
3, to adopt flexible hinge be elastic guide for micropositioner of the present invention, and having does not have machinery friction, no gap, autokinesis advantages of higher, is driver with the piezoelectric ceramics, and compact conformation, is controlled simply micrometric displacement resolution ratio height, and does not have heating problem.This just makes workbench be easier to realize microminiaturized.
4, by setting up the kinematic accuracy of motion model analytical work platform, simplify the error bring in several nanometer range by model itself, cause that by processing, alignment error the flexible hinge error of coordinate also can influence kinematic accuracy, and the relative hinge error of coordinate of working table movement error has very big drawdown ratio, and therefore this error effect can be very little.Can reach nanoscale by the kinematic accuracy of calculating micropositioner, visible workbench can be realized nano level measurement and location.
The specific embodiment:
Referring to Fig. 1, Fig. 3, present embodiment adopts the Piezoelectric Driving bar, connect with eight bar symmetrical manner, the outer end of Piezoelectric Driving bar A-a, B-b, C-c, D-d, E-e, F-f, G-g, H-h links to each other with fixed station by flexible hinge A, B, C, D, E, F, G, H, and the inner links to each other with micropositioner by flexible hinge a, b, c, d, e, f, g, h.
In concrete the enforcement, as shown in Figure 1, be that the center that constitutes face with flexible hinge A, B, C, D fixed endpoint is initial point O, the plane at flexible hinge A, B, C, D fixed endpoint place is in the fixed coordinate system set up of XOY coordinate surface, the initial position of Piezoelectric Driving bar A-a, C-c and B-b, D-d is parallel with Y-axis or X-axis respectively, Piezoelectric Driving bar E-e, F-f, G-g, the H-h initial position is parallel with the Z axle, each hinge point relative coordinate initial point that links to each other with micropositioner is symmetrically distributed, and eight bar initial lengths equate.
Fig. 3 illustrates, and the Piezoelectric Driving bar that is adopted in this enforcement is a Piezoelectric Ceramic bar 1, and Piezoelectric Ceramic bar 1 extends under applied voltage, changes the length of drive rod 1 by control applied voltage value.During micropositioner 2 motions, strain only takes place in flexible hinge 3 positions, other parts all are considered to rigid body.
In the present embodiment, adopt the parallel control mode, this parallel control mode is the length variations by eight Piezoelectric Driving bars of parallel control, and the synchronized movement of a plurality of frees degree of workbench is carried out.
Be specially: length variations amount and the momental relation of each free degree of workbench with eight drive rods are set up the working table movement model; Realize the motion of a plurality of frees degree of workbench synchronously according to the length of model control Piezoelectric Driving bar.
Foundation about the working table movement model:
Show the motion of the various single-degree-of-freedoms of workbench respectively at Fig. 2 (a), 2 (b), 2 (c), 2 (d), 2 (e), 2 (f).
During following instruction book degree-of-freedom micro, the relation of worktable displacement and single drive rod deflection.
With drive rod A-a is example.Micro displacement workbench is along directions X translation Δ X (Fig. 2 (a)), then a point coordinates value (Xa, Ya Za) are changed to:
X′
a=X
a+ΔX,Y′
a=Y
a,Z′
a=Z
a,
Drive rod A-a length variations is:
L′
2 (A-a)=(X′
a-X
A)
2+(Y′
a-Y
A)
2+(Z′
a-Z
A)
2=L
2 (A-a)+2(X
a-X
A)ΔX+(ΔX)
2。
In like manner, micro displacement workbench has along Y direction translational Δ Y (Fig. 2 (b)):
X′
a=X
a,Y′
a=Y
a+ΔY,Z′
a=Z
a,
L′
2 (A-a)=L
2 (A-a)+2(Y
a-Y
A)ΔY+(ΔY)
2。
Micro displacement workbench has along Z direction translational Δ Z (Fig. 2 (c)):
X′
a=X
a,Y′
a=Y
a,Z′
a=Z
a+ΔZ,
L′
2 (A-a)=L
2 (A-a)+2(Z
a-Z
A)ΔZ+(ΔZ)
2。
Besides bright workbench rotates around fixed coordinate system, and establishing the torque of a point is Ra.
The micro displacement workbench list rotates Δ α (Fig. 2 (d)) around X-axis, then
Y
a=R
acosθ,
Z
a=R
asinθ。
The a point coordinates (Xa, Ya Za) are changed to:
X′
a=X
a,
Y′
a=R
acos(θ+Δα)=R
acosθcosΔα-R
asinθsinΔα=Y
acosΔα-Z
asinΔα,
Z′
a=R
asin(θ+Δα)=R
asinθcosΔα+R
acosθsinΔα=Z
acosΔα+Y
asinΔα,
In like manner, workbench rotates Δ β (Fig. 2 (e)) around Y-axis merely, has:
X
a′=X
acosΔβ-Z
asinΔβ,
Y′
a=Y
a,
Z′
a=Z
acosΔβ+X
asinΔβ,
Workbench rotates Δ γ (Fig. 2 (f)) around the Z axle merely, has:
X
a′=X
acosΔγ-Y
asinΔγ,
Y′
a=Y
acosΔγ+X
asinΔγ
Z′
a=Z
a
The derivation method of the length variations formula of eight bars is identical with drive rod A-a.
Since Δ X, Δ Y, Δ Z, Δ α, Δ β, Δ γ is very little, so can be approximated as follows:
ΔX
2→0,ΔY
2→0,ΔZ
2→0,sinΔα→Δα,sinΔβ→Δβ,sinΔγ→Δγ,cosΔα→1,cosΔβ→1,cosΔγ→1
Make Δ L
(A-a)=L '
(A-a)-L
(A-a), then (Δ L)
2→ 0
In the time of can getting the single-degree-of-freedom fine motion, following relation is arranged between drive rod A-a length variations amount and the worktable displacement amount:
L
(A-a)ΔL
(A-a)=(X
a-X
A)ΔX,
L
(A-a)ΔL
(A-a)=(Y
a-Y
A)ΔY,
L
(A-a)ΔL
(A-a)=(Z
a-Z
A)ΔZ,
L
(A-a)ΔL
(A-a)=(Z
aY
A-Y
aZ
A)Δα,
L
(A-a)ΔL
(A-a)=(Z
aX
A-X
aZ
A)Δβ,
L
(A-a)ΔL
(A-a)=(Y
aX
A-X
aY
A)Δγ。
During the multiple degrees of freedom fine motion, the relation of single drive rod length variations amount and worktable displacement amount
If fine motion is Δ X → Δ Y → Δ Z → Δ α → Δ β → Δ γ in proper order, be example still with the A-a bar.
X
a′(1)=X
a+ΔX X
a′(2)=X
a+ΔX X
a′(3)=X
a+ΔX
Y
a′(1)=Y
a Y
a′(2)=Y
a+ΔY Y
a′(3)=Y
a+ΔY
Z
a′(1)=Z
a Z
a′(2)=Z
a Z
a′(3)=Z
a+ΔZ
X
a′(4)=X
a+ΔX
Y
a′(4)=(Y
a+ΔY)cos(Δα)-(Z
a+ΔZ)sin(Δα)
Z
a′(4)=(Z
a+ΔZ)cos(Δα)+(Y
a+ΔY)sin(Δα)
X
a′(5)=(X
a+ΔX)cos(Δβ)-(Z
a+ΔZ)cos(Δα)sin(Δβ)-(Y
a+ΔY)sin(Δα)sin(Δβ)
Y
a′(5)=(Y
a+ΔY)cos(Δα)-(Z
a+ΔZ)sin(Δα)
Z
a′(5)=(Z
a+ΔZ)cos(Δα)cos(Δβ)+(Y
a+ΔY)sin(Δα)cos(Δβ)+(X
a+ΔX)sin(Δβ)
X
a′(6)=(X
a+ΔX)cos(Δβ)cos(Δγ)-(Z
a+ΔZ)cos(Δα)sin(Δβ)cos(Δγ)
-(Y
a+ΔY)sin(Δα)sin(Δβ)cos(Δγ)-(Y
a+ΔY)cos(Δα)sin(Δγ)
+(Z
a+ΔZ)sin(Δα)sin(Δγ)
Y
a′(6)=(Y
a+ΔY)cos(Δα)cos(Δγ)-(Z
a+ΔZ)sin(Δα)cos(Δγ)
+(X
a+ΔX)cos(Δβ)sin(Δγ)-(Z
a+ΔZ)cos(Δα)sin(Δβ)sin(Δγ)
-(Y
a+ΔY)sin(Δα)sin(Δβ)sin(Δγ)
Z
a′(6)=(Z
a+ΔZ)cos(Δα)cos(Δβ)+(Y
a+ΔY)sin(Δα)cos(Δβ)+(X
a+ΔX)sin(Δβ)
L′
2 (A-a)=(X
a′ (6)-X
A)
2+(Y
a′ (6)-Y
A)
2+(Z
a′ (6)-Z
A)
2
≈L
2 (A-a)+2(X
a-X
A)ΔX+2(Y
a-Y
A)ΔY+2(Z
a-Z
A)ΔZ
+2(Z
aY
A-Y
aZ
A)Δα+2(Z
aX
A-X
aZ
A)Δβ+2(Y
aX
A-X
aY
A)Δγ
The derivation of equation method of other drive rod is the same.Can demonstrate,prove, the fine motion order does not influence conclusion.
During parallel moving, the Mathematical Modeling of drive rod Deformation control
The formula of deriving is previously concluded, can be got the relation between each bar distortion and each degree-of-freedom micro:
This is when each bar is parallel to move, the Mathematical Modeling of driver control.If length, the position of each bar are perfect condition, then following formula can be simplified to:
This driving control model is derived under perfect condition, realize as can be seen that by model the drive rod that each single free degree motion of workbench will be controlled has nothing in common with each other, control two bars that have, control four bars that have, will realize that the workbench multifreedom motion will each single dof mobility of Synchronization Control, the independence that is controlled to be of each drive rod combines with local correlation.X will control drive rod A-a and C-c along directions X translation Δ, Y will control drive rod B-b and D-d along Y direction translational Δ, Z will control drive rod E-e along Z direction translational Δ, F-f, G-g, H-h, rotate Δ α around X-axis merely and will control drive rod F-f and H-h, rotate Δ β around Y-axis merely and want drive rod E-e and G-g, rotate Δ γ around the Z axle merely and will control drive rod A-a, B-b, C-c, D-d, the multivariant motion of workbench will be to the control of being correlated with of each drive rod, each drive rod length variations amount has nothing in common with each other when realizing the micropositioner multifreedom motion, single layer structure six-freedom micro displacement worktable concurrency control method, exactly according to the amount of exercise Δ X of above-mentioned model by each free degree that will realize, Δ Y, Δ Z, Δ α, Δ β, Δ γ calculates the length variations amount of each Piezoelectric Driving bar, the relevant control of motion to piezoelectric actuator, the motion of each free degree can be carried out synchronously, reaches the purpose to the workbench parallel control.Can significantly reduce the required time of workbench orientation adjustment by this concurrency control method, improve and measure speed and efficient.