Micro movable mechanism system and control method for the same

• US 7,088,492 B2
• Filed: 10/09/2002
• Issued: 08/08/2006
• Est. Priority Date: 10/11/2001
• Status: Expired due to Fees

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Yanagita, Yoshiho, Yoshizawa, Shin
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): ALSOMIRI, ISAM A
• Application Number:
  US10/266,634
• Publication Number:
  US 20030094914A1
• Time in Patent Office: 1,399 Days
• Field of Search: None
• US Class Current: 359/290
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: G02B 6/359 of the position of the moving element itself during switching, i.e. without monitoring the switched beams

Abstract

A micro movable mechanism system includes a micro movable mechanism. A target position generating section generates a signal indicative a target position of the micro movable mechanism. A nonlinear control unit outputs a controller output signal indicating a control value based on a difference between the target position signal and a signal indicating a current position of the micro movable mechanism. A root correction section drives the micro movable mechanism based on a signal proportional to a square root of the control value.

Claims

1. A micro movable mechanism system comprising:

a micro movable mechanism;

a target position generating section which generates a signal indicative a target position of said micro movable mechanism;

a nonlinear control unit which outputs a controller output signal indicating a control value based on a difference between said target position signal and a signal indicating a current position of said micro movable mechanism; and

a root correction section which drives said micro movable mechanism based on a signal proportional to a square root of said control value.

2. A micro movable mechanism system comprising:

a mirror mechanism which has a mirror surface;

a target position generating section which generates a signal indicating a target position θ

r of said mirror surface;

a mirror angle deriving section which derives a current angle θ

of said mirror surface;

a nonlinear control unit which outputs a controller output signal indicating a control value u based on an angle difference Δ

θ

between said current angle θ

of said mirror surface and said target angle θ

r; and

a root correction section which drives said mirror mechanism based on a signal of a drive voltage V proportional to a square root of said control value u such that said mirror surface is rotated.

3. The micro movable mechanism system according to claim 2, further comprising:

a correction value generating section which corrects said control value u, and

said root correction section drives said mirror mechanism based on the corrected control value such that said mirror surface is rotated.

4. The micro movable mechanism system according to claim 2, wherein said mirror mechanism comprises:

a movable electrode section which has said mirror surface and rotates around a rotation axis;

a support spring section which supports said movable electrode section in a predetermined angle position with elastic force; and

a fixed electrode section which is provided apart from said movable electrode section, and to which said drive voltage signal is applied from said root correction section, said drive voltage corresponding to a value proportional to the square root of said control value u, and

said movable electrode section is rotated in the electrostatic force generated based on said drive voltage V applied by said fixed electrode section.

5. The micro movable mechanism system according to claim 4, wherein said mirror angle deriving section measures a direction of a light reflected by said mirror surface to derive said current angle θ

.

6. The micro movable mechanism system according to claim 4, wherein said mirror angle deriving section comprises:

an angle sensor which measures a capacitance between said movable electrode section and said fixed electrode section and derives said current angle θ

based on said capacitance.

7. The micro movable mechanism system according to claim 4, wherein said mirror angle deriving section comprises:

a nonlinear model section which derives said current angle θ

using a mathematical model,

said current angle θ

from said predetermined angle position is a function in time t, and

said nonlinear model section derives said current angle θ

using a nonlinear gain f(θ

) as a function of said current angle θ

.

8. The micro movable mechanism system according to claim 7, wherein said fixed electrode section is provided apart from a projection line obtained by vertically projecting said rotation axis on a plane where said fixed electrode section exists,

said nonlinear gain f(θ

) is expressed by the following equation (3), using a distance D between said movable electrode section and said fixed electrode section, a distance L1 which is the shortest distance from said fixed electrode section to said projection line, a distance L2 (L2>

L1>

0) which is the longest distance from said fixed electrode section to said projection line, and a length W(x) in a direction parallel to said rotation axis;

$\begin{array}{cc}f<br><br>\left(\mathrm{\theta <br><br>}\right)={\int <br><br>}_{L_1}^{L_2}<br><br>\frac{W<br><br>\left(x\right)<br><br>x}{{\left\{\left(\frac{D}{\sin <br><br><br><br>\mathrm{\theta <br><br>}<br><br>}-x\right)<br><br>\mathrm{\theta <br><br>}\right\}}^2}<br><br>d<br><br>x& \left(3\right)\end{array}$

said constant number B is expressed by the following equation (4) using a dielectric constant ε

between said movable electrode section and said fixed electrode section;

$\begin{array}{cc}B=\frac{1}{2}<br><br>\mathrm{\varepsilon <br><br>}& \left(4\right)\end{array}$

said constant number J is an inertia moment of said movable electrode section,

said constant number C is a dumping of said support spring section,

said constant number K is a stiffness of said support spring section, and

said control value u is the following equation;

u=V².

9. The micro movable mechanism system according to claim 7, wherein said fixed electrode section has a rectangle, and is provided apart from a projection line when said rotation axis is vertically projected on a plane where said fixed electrode section exists,

said nonlinear gain f(θ

) is expressed by the following equation (5), using a distance D between said rotation axis to said fixed electrode section, a distance L1 from one side of said rectangle which is parallel to said rotation axis to said projection line, a distance L2 (L2>

L1>

0) from an opposite side to said side to said projection line, and a length W(x) in a direction parallel to said rotation axis;

$\begin{array}{cc}\begin{array}{c}f<br><br>\left(\mathrm{\theta <br><br>}\right)=<br><br>\frac{1}{{\mathrm{\theta <br><br>}}^2}[\left(\frac{\frac{D}{\sin <br><br><br><br>\mathrm{\theta <br><br>}<br><br>}}{\frac{D}{\sin <br><br><br><br>\mathrm{\theta <br><br>}<br><br>}-L_2}-\frac{\frac{D}{\sin <br><br><br><br>\mathrm{\theta <br><br>}<br><br>}}{\frac{D}{\sin <br><br><br><br>\mathrm{\theta <br><br>}<br><br>}-L_1}\right)+\\ <br><br>\left\{\log <br><br>\left(\frac{D}{\sin <br><br><br><br>\mathrm{\theta <br><br>}<br><br>}-L_2\right)-\log <br><br>\left(\frac{D}{\sin <br><br><br><br>\mathrm{\theta <br><br>}<br><br>}-L_1\right)\right\}]\end{array}& \left(5\right)\end{array}$

said constant number B is expressed by the following equation (6), using a length W of a side of said rectangle which is orthogonal to said rotation axis and a dielectric constant ε

between said movable electrode section and said fixed electrode section;

$\begin{array}{cc}B=\frac{1}{2}<br><br>\mathrm{\varepsilon <br><br>}<br><br><br><br>W& \left(6\right)\end{array}$

said constant number J is an inertia moment of said movable electrode section,

said constant number C is a dumping of said movable electrode section,

said constant number K is a stiffness of said support spring section, and

said control value u is the following equation;

u=V².

10. The micro movable mechanism system according to claim 7, wherein said nonlinear gain f(θ

) is approximated as a polynomial of said current angle θ

.

11. The micro movable mechanism system according to claim 2, wherein said mirror angle deriving section comprises:

a nonlinear model section which derives said current angle θ

based on a mathematical model and said control value u.

12. The micro movable mechanism system according to claim 11, wherein said mathematical model is a motion equation of said movable electrode section.

13. The micro movable mechanism system according to claim 2, wherein said mirror angle deriving section comprises:

a nonlinear model section which derives said current angle θ

based on a mathematical model and said drive voltage V.

14. The micro movable mechanism system according to claim 13, wherein said mathematical model is a motion equation of said movable electrode section.

15. The micro movable mechanism system according to claim 2, wherein said mirror angle deriving section comprises:

a nonlinear model section which derives said current angle θ

using a mathematical model.

16. The micro movable mechanism system according to claim 15, wherein said current angle θ

from said predetermined angle position of said movable electrode section is a function in time t, and

said nonlinear model section derives said current angle θ

from the following equation (1), using a nonlinear gain f(θ

) as a function of said current angle θ

, constant number J, C, K, and B, and said control value u;

$\begin{array}{cc}J<br><br>\frac{{d<br><br>}^2<br><br>\mathrm{\theta <br><br>}}{d<br><br>t^2}+C<br><br>\frac{d<br><br>\mathrm{\theta <br><br>}}{d<br><br>t}+K<br><br><br><br>\mathrm{\theta <br><br>}=\mathrm{Bf}<br><br>\left(\mathrm{\theta <br><br>}\right)<br><br>u.& \left(1\right)\end{array}$

17. The micro movable mechanism system according to claim 15, wherein said current angle θ

from said predetermined angle position is a function in time t, and

said nonlinear model section derives said current angle θ

from the following equation (2), using a nonlinear gain f(θ

) as a function of said current angle θ

, constant number J, C, K, and B, said drive voltage V;

$\begin{array}{cc}J<br><br>\frac{{d<br><br>}^2<br><br>\mathrm{\theta <br><br>}}{d<br><br>t^2}+C<br><br>\frac{d<br><br>\mathrm{\theta <br><br>}}{d<br><br>t}+K<br><br><br><br>\mathrm{\theta <br><br>}=\mathrm{Bf}<br><br>\left(\mathrm{\theta <br><br>}\right)<br><br>V^2.& \left(2\right)\end{array}$

18. The micro movable mechanism system according to claim 2, wherein said nonlinear control unit comprises:

a nonlinear state observer section which derives an estimation ω

o based on said control value u and said current angle θ

; and

a linear control unit which derives a new control value u through a linear calculation of said estimation ω

o and said current angle θ

.

19. The micro movable mechanism system according to claim 2, wherein said nonlinear control unit comprises:

a nonlinear state observer section which derives an estimation ω

o based on said control value u and said current angle θ

; and

a linear control unit which derives a new control value u through PID control of said estimation ω

o and said angle difference Δ

θ

.

20. The micro movable mechanism system according to claim 2, wherein said nonlinear control unit comprises:

a nonlinear state observer section which derives an estimation ω

o based on said control value u and said current angle θ

such that a new control value u is derived based on said estimation ω

o and said angle difference Δ

θ

.

21. The micro movable mechanism system according to claim 20, wherein said nonlinear state observer section comprises:

a nonlinear gain section which derives a nonlinear gain f(θ

) based on said current angle θ

; and

a linear state observer section which derives a function of said current angle θ

as said estimation ω

o based on the following equation (7) using constant numbers J, C, K, and B;

$\begin{array}{cc}J<br><br>\frac{{d<br><br>}^2<br><br>\mathrm{\theta <br><br>}}{d<br><br>t^2}+C<br><br>\frac{d<br><br>\mathrm{\theta <br><br>}}{d<br><br>t}+K<br><br><br><br>\mathrm{\theta <br><br>}=\mathrm{Bf}<br><br>\left(\mathrm{\theta <br><br>}\right)<br><br>u.& \left(7\right)\end{array}$

22. The micro movable mechanism system according to claim 21, wherein said estimation ω

o is angular speed dθ

/dt.

23. The micro movable mechanism system according to claim 21, further comprising:

a calibration section which derives a correction value based on said current angle θ and

said control value u, and

said linear state observer section updates said constant number J, C or K based on said correction value.

24. The micro movable mechanism system according to claim 23, wherein said nonlinear operation section updates said constant number L1, said constant number L2, said constant number D or said constant number W based on said correction value.

25. The micro movable mechanism system according to claim 23, wherein said nonlinear operation section updates said constant numbers of said polynomial approximation based on said correction value.

26. The micro movable mechanism system according to claim 20, further comprising:

a calibration section which derives a correction value based on said current angle θ and

said control value u; and

a gain correction section which updates said control value u based on said correction value, and

said root correction section outputs to said mirror mechanism, said drive voltage signal indicating said drive voltage V proportional to a square root of the updated control value u.

27. The micro movable mechanism system according to claim 2, further comprising:

a light intensity sensor which measures a light intensity of a light beam which is reflected by said mirror surface and is received by a light receiving area; and

a light intensity angle conversion section which derives said angle difference Δ

θ

based on said light intensity.

28. A micro movable mechanism system comprising:

a mirror mechanism which has a mirror surface rotatable around first and second rotation axes;

first and second units, each of which drives said mirror mechanism to rotate said mirror surface around a relating one of said first and second rotation axes, and

wherein each of said first and second unit comprises;

a target position generating section which generates a signal indicating a target position θ

r of said mirror surface for said relating rotation axis;

a mirror angle deriving section which derives a current angle θ

of said mirror surface for said relating rotation axis;

a nonlinear control unit which outputs a controller output signal indicating a control value u for said relating rotation axis based on an angle difference θ

between said current angle θ

of said mirror surface and said target angle θ

r for said relating rotation axis; and

a root correction section which drives said mirror mechanism for said relating rotation axis based on a signal of a drive voltage V proportional to a square root of said control value u for said relating rotation axis such that said mirror surface is rotated.

29. The micro movable mechanism system according to claim 28, wherein each of said first and second units further comprises:

a correction value generating section, which corrects said control value u for said relating rotation axis, and

said root correction section drives said mirror mechanism based on the corrected control value u such that said mirror surface is rotated.

30. The micro movable mechanism system according to claim 28, wherein said mirror mechanism comprises:

a movable electrode section which has said mirror surface and is rotatable around for said first rotation axis;

a movable electrode support spring section which supports said movable electrode section in the predetermined angle position for said first rotation axis with elastic force;

a movable frame section which is connected to said movable electrode support spring section and is rotatable around for said second rotation axis which is not parallel to said first rotation axis;

a movable frame support spring section which supports said movable frame section in a predetermined angle position for said second rotation axis with elastic force;

a first fixed electrode section which is arranged in a plane parallel to said first rotation axis;

a second fixed electrode section which is arranged in a plane parallel to said second rotation axis; and

said movable electrode section and said movable frame section are rotated with electrostatic force generated based on said drive voltage signals which are applied to said first and second fixed electrode sections.

31. The micro movable mechanism system according to claim 30, wherein said mirror angle deriving section measures a direction of a light reflected by said mirror surface to derive said current angle θ

for said relating rotation axis.

32. The micro movable mechanism system according to claim 30, wherein said mirror angle deriving section of said first unit comprises:

an angle sensor which measures a capacitance between said movable electrode section and said first fixed electrode section and derives said current angle θ

based on said capacitance,

wherein said mirror angle deriving section of said second unit comprises;

an angle sensor which measures a capacitance between said movable frame section and said second fixed electrode section and derives said current angle θ

based on said capacitance.

33. The micro movable mechanism system according to claim 30, wherein said mirror angle deriving section comprises:

a nonlinear model section which derives said current angle θ

using a mathematical model.

34. The micro movable mechanism system according to claim 33, wherein said current angle θ

from said predetermined angle position is a function in time t, and

said nonlinear model section derives said current angle θ

from the following equation (1), using a nonlinear gain f(θ

) as a function of said current angle θ

, constant number J, C, K, and B, and said control value u;

$\begin{array}{cc}J<br><br>\frac{{d<br><br>}^2<br><br>\mathrm{\theta <br><br>}}{d<br><br>t^2}+C<br><br>\frac{d<br><br>\mathrm{\theta <br><br>}}{d<br><br>t}+K<br><br><br><br>\mathrm{\theta <br><br>}=\mathrm{Bf}<br><br>\left(\mathrm{\theta <br><br>}\right)<br><br>u.& \left(1\right)\end{array}$

35. The micro movable mechanism system according to claim 33, wherein said current angle θ

from said predetermined angle position is a function in time t, and

said nonlinear model section derives said current angle θ

from the following equation (2), using a nonlinear gain f(θ

) as a function of said current angle θ

, constant number J, C, K, and B, said drive voltage V;

$\begin{array}{cc}J<br><br>\frac{{d<br><br>}^2<br><br>\mathrm{\theta <br><br>}}{d<br><br>t^2}+C<br><br>\frac{d<br><br>\mathrm{\theta <br><br>}}{d<br><br>t}+K<br><br><br><br>\mathrm{\theta <br><br>}=\mathrm{Bf}<br><br>\left(\mathrm{\theta <br><br>}\right)<br><br>V^2.& \left(2\right)\end{array}$

36. The micro movable mechanism system according to claim 30, wherein said mirror angle deriving section comprises:

a nonlinear model section which derives said current angle θ

using a mathematical model,

said current angle θ

from said predetermined angle position is a function in time t, and

said nonlinear model section derives said current angle θ

using a nonlinear gain f(θ

) as a function of said current angle θ

.

37. The micro movable mechanism system according to claim 36, wherein said fixed electrode section is provided apart from a projection line obtained by vertically projecting said relating rotation axis on a plane where a corresponding one of said first and second fixed electrode section exists,

said nonlinear gain f(θ

) is expressed by the following equation (3), using a distance D between said movable electrode section and said fixed electrode section, a distance L1 which is the shortest distance from said corresponding fixed electrode section to said projection line, a distance L2 (L2>

L1>

0) which is the longest distance from said corresponding fixed electrode section to said projection line, and a length W(x) in a direction parallel to said relating rotation axis;

$\begin{array}{cc}f<br><br>\left(\mathrm{\theta <br><br>}\right)={\int <br><br>}_{L_1}^{L_2}<br><br>\frac{W<br><br>\left(x\right)<br><br>x}{{\left\{\left(\frac{D}{\sin \left|\mathrm{\theta <br><br>}\right|}-x\right)<br><br>\mathrm{\theta <br><br>}\right\}}^2}<br><br>d<br><br>x& \left(3\right)\end{array}$

said constant number B is expressed by the following equation (4) using a dielectric constant ε

between a corresponding one of said movable electrode section and said movable frame section and said corresponding fixed electrode section;

$\begin{array}{cc}B=\frac{1}{2}<br><br>\mathrm{\varepsilon <br><br>}& \left(4\right)\end{array}$

said constant number J is an inertia moment of said movable electrode section,

said constant number C is a dumping of said support spring section,

said constant number K is a stiffness of said support spring section, and

said control value u is the following equation;

u=V².

38. The micro movable mechanism system according to claim 36, wherein said fixed electrode section has a rectangle, and is provided apart from a projection line when said rotation axis is vertically projected on a plane where said fixed electrode section exists,

said nonlinear gain f(θ

) is expressed by the following equation (5), using a distance D between said rotation axis to said fixed electrode section, a distance L1 from one side of said rectangle which is parallel to said rotation axis to said projection line, a distance L2 (L2>

L1>

0) from an opposite side to

said side to said projection line, and a length W(x) in a direction parallel to said rotation axis;

$\begin{array}{cc}f<br><br>\left(\mathrm{\theta <br><br>}\right)=\frac{1}{{\mathrm{\theta <br><br>}}^2}<br><br>\left[\left(\frac{\frac{D}{\sin \left|\mathrm{\theta <br><br>}\right|}}{\frac{D}{\sin \left|\mathrm{\theta <br><br>}\right|}-L_2}-\frac{\frac{D}{\sin \left|\mathrm{\theta <br><br>}\right|}}{\frac{D}{\sin \left|\mathrm{\theta <br><br>}\right|}-L_1}\right)+\left\{\log <br><br>\left(\frac{D}{\sin \left|\mathrm{\theta <br><br>}\right|}-L_2\right)-\log <br><br>\left(\frac{D}{\sin \left|\mathrm{\theta <br><br>}\right|}-L_1\right)\right\}\right]& \left(5\right)\end{array}$

said constant number B is expressed by the following equation (6), using a length W of a side of

said rectangle which is orthogonal to said rotation axis and a dielectric constant ε

between a corresponding one of said movable electrode section and said movable frame section and said corresponding fixed electrode section;

$\begin{array}{cc}B=\frac{1}{2}<br><br>\mathrm{\varepsilon <br><br>}<br><br><br><br>W& \left(6\right)\end{array}$

said constant number J is an inertia moment of said movable electrode section,

said constant number C is a dumping of said movable electrode section,

said constant number K is a stiffness of said support spring section, and

said control value u is the following equation;

u=V².

39. The micro movable mechanism system according to claim 36, wherein said nonlinear gain f(θ

) is approximated as a polynomial of said current angle θ

.

40. The micro movable mechanism system according to claim 28, wherein said mirror angle deriving section comprises:

a nonlinear model section which derives said current angle θ

based on a mathematical model and said control value u.

41. The micro movable mechanism system according to claim 40, wherein said mathematical model is a motion equation of said movable electrode section.

42. The micro movable mechanism system according to claim 28, wherein said mirror angle deriving section comprises:

a nonlinear model section which derives said current angle θ

based on a mathematical model and said drive voltage V.

43. The micro movable mechanism system according to claim 42, wherein said mathematical model is a motion equation of said movable electrode section.

44. The micro movable mechanism system according to claim 28, wherein said nonlinear control unit comprises:

a nonlinear state observer section which derives an estimation ω

o based on said control value u and said current angle θ

; and

a linear control unit which derives a new control value u through a linear calculation of said estimation ω

o and said current angle θ

.

45. The micro movable mechanism system according to claim 28, wherein said nonlinear control unit comprises:

a nonlinear state observer section which derives an estimation ω

o based on said control value u and said current angle θ

; and

a linear control unit which derives a new control value u through PID control of said estimation ω

o and said angle difference Δ

θ

.

46. The micro movable mechanism system according to claim 28, wherein said nonlinear control unit comprises:

a nonlinear state observer section which derives an estimation ω

o based on said control value u and said current angle θ

such that a new control value u is derived based on said estimation ω

o and said angle difference Δ

θ

.

47. The micro movable mechanism system according to claim 46, wherein said nonlinear state observer section comprises:

a nonlinear gain section which derives a nonlinear gain f(θ

) based on said current angle θ

; and

a linear state observer section which derives a function of said current angle θ

as said estimation ω

o based on the following equation (7) using constant numbers J, C, K, and B;

$\begin{array}{cc}J<br><br>\frac{{d<br><br>}^2<br><br>\mathrm{\theta <br><br>}}{d<br><br>t^2}+C<br><br>\frac{d<br><br>\mathrm{\theta <br><br>}}{d<br><br>t}+K<br><br><br><br>\mathrm{\theta <br><br>}=B<br><br><br><br>f<br><br>\left(\mathrm{\theta <br><br>}\right)<br><br>u.& \left(7\right)\end{array}$

48. The micro movable mechanism system according to claim 47, wherein said estimation ω

o is angular speed dθ

/dt.

49. The micro movable mechanism system according to claim 47, wherein each of said first and second units further comprises:

a calibration section which derives a correction value based on said current angle θ and

said control value u, and

said linear state observer section updates said constant number J, C or K based on said correction value.

50. The micro movable mechanism system according to claim 49, wherein said nonlinear operation section updates said constant number L1, said constant number L2, said constant number D or said constant number W based on said correction value.

51. The micro movable mechanism system according to claim 49, wherein said nonlinear operation section updates said constant numbers of said polynomial approximation based on said correction value.

52. The micro movable mechanism system according to claim 46, each of said first and second units further comprises:

a calibration section which derives a correction value based on said current angle θ and

said control value u; and

a gain correction section which updates said control value u based on said correction value, and

said root correction section outputs to said mirror mechanism, said drive voltage signal indicating said drive voltage V proportional to a square root of the updated control value u.

53. The micro movable mechanism system according to claim 28, each of said first and second units further comprises:

a light intensity sensor which measures a light intensity of a light beam which is reflected by said mirror surface and is received by a light receiving area; and

a light intensity angle conversion section which derives said angle difference Δ

θ

based on said light intensity.