Method and device for displacing a moving body on a base mounted elastically with respect to the ground

• US 6,438,461 B1
• Filed: 07/27/1999
• Issued: 08/20/2002
• Est. Priority Date: 02/23/1999
• Status: Expired due to Term

• Current Assignee: Newport Corporation (MKS Instruments Incorporated)
• Original Assignee: Newport Corporation (MKS Instruments Incorporated)
• Inventors: Desailly, Roger, Nguyen, Van Diêp, Maneuf, Serge, Levine, Jean
• Primary Examiner(s): Picard, Leo
• Assistant Examiner(s): JARRETT, RYAN A
• Application Number:
  US09/362,643
• Time in Patent Office: 1,120 Days
• Field of Search: 700/280, 700/302, 700/56, 700/60, 700/63, 702/56, 735/70, 248/638
• US Class Current: 700/280
• CPC Class Codes: G03F 7/70716 Stages

Abstract

The present invention relates to a method and a device for displacing a moving body (4) on a base (2) mounted elastically with respect to the ground (S), the moving body (4) being displaced linearly with a predetermined displacement under the action of a controllable force (F).

According to the invention:

a) a mathematical relationship illustrating the movements of the entity formed by the base (2) and the moving body (4) is defined;

b) using said mathematical relationship there is determined a force (F) which, applied to the moving body (4), produces a combined effect on the moving body (4) so that it performs said predetermined displacement, and on the base (2) at least so that it is immobile at the end of the displacement of the moving body (4); and

c) the force (F) thus determined is applied to the moving body (4).

Claims

1. A method for displacing a moving body (4) on a base (2) mounted elastically with respect to the ground (S), said moving body (4) being displaced linearly with a predetermined displacement under the action of a controllable force (F), wherein:

a) a mathematical relationship illustrating the movements of the entity formed by the base (2) and the moving body (4) and dependent on parameters related to the base (2) and to the moving body (4) wherein said parameters vary during a displacement of the moving body, is defined;

(b) using said mathematical relationship, mathematical processing is used to determine a force (F) which, applied to said moving body (4), produces a combined effect;

on the one hand, on the moving body (4) so that it performs said predetermined displacement; and

on the other hand, on the base (2) at least so that it is immobile at the end of the displacement of the moving body (4); and

(c) the force (F) thus determined is applied to said moving body (4).

2. A method as claimed in claim 1, wherein by way of mathematical relationship in step a), use is made of the following relationship:

$y=x-\frac{\mathrm{k1}}{\mathrm{k0}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\stackrel{.}{x}+\frac{1}{m}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{mB}-\frac{{\mathrm{k1}}^2}{\mathrm{k0}}\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{xB}-\frac{\mathrm{mB}}{m}·<br><br>\frac{\mathrm{k1}}{\mathrm{k0}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\stackrel{.}{x}<br><br>B.$

in which;

y represents an imaginary variable;

k0 and k1 respectively represent the natural frequency and the damping of the elastically mounted base (2);

m and mB represent the masses of the moving body (4) and of the base (2), respectively;

x and xB represent the displacements of the moving body (4) and of the base (2), respectively; and

x and xB represent the speeds of displacement of the moving body (4) and of the base (2), respectively.

3. A method as claimed in claim 1, wherein, in step b), the mathematical processing operation employs a sum of sinusoidal functions.

4. A method as claimed in claim 1, wherein, in step b), the mathematical processing operation employs a polynominal decomposition.

5. A method as claimed in claim 2, wherein, in step b), the force F is determined from the following relationship:

$F=m<br><br>\text{\hspace{1em}<br><br>}<br><br>\stackrel{\mathrm{¨<br><br>}}{y}+m<br><br>\frac{\mathrm{k1}}{\mathrm{k0}}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^{\left(3\right)}+\frac{\mathrm{mmB}}{\mathrm{k0}}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^{\left(4\right)},$

ÿ

, y⁽³⁾ and y⁽⁴⁾ being the 2nd, 3rd and 4th-order derivatives of the variable y, respectively, and using the following polynomial decomposition of y(t);

6. A device, comprising:

a base;

a body coupled to said base;

an actuator coupled to said body; and

,

a computer that provides a control command to said actuator, said control command induces a force profile that causes said body to move from a start position at a start time to an end position at an end time, so that said base has a zero displacement at the end time, the force profile being dependent on parameters related to said base and said body, said parameters vary as said body moves from the start to end positions.

7. The device of claim 6, wherein the force profile is dependent upon an imaginary variable.

8. The device of claim 7, wherein the imaginary variable is the expression y=x−

k1/k0·

{dot over (x)}+1/m·

(mB−

k0)·

xB−

mB/m·

k1/k0·

{dot over (x)}B, where y is the imaginary variable, x is a position of a center of said body, xB is a position of a center of said base, {dot over (x)} and {dot over (x)}B are the time base derivatives of x and xB, respectively, m is a mass of said body, mB is a mass of said base, k0 is a natural frequency of said base and k1 is a damping of said base.

9. The device of claim 8, wherein the force profile causes said base to have a positive displacement and then a negative displacement when said body is moved by said actuator.

10. The device of claim 8, wherein the imaginary variable is expressed as a polynomial.

11. The device of claim 8, wherein the imaginary variable is expressed as a sinusoidal decomposition.

12. A device, comprising:

a base;

a body coupled to said base;

an actuator coupled to said body; and

,

calculation means for generating a control command that is provided to said actuator, said control command induces a force profile that causes said body to move from a start position at a start time to an end position at an end time, so that said base has a zero displacement at the end time, the force profile being dependent on parameters related to said base and said body, said parameters vary as said body moves from the start to end positions.

13. The device of claim 12, wherein the force profile is dependent upon an imaginary variable.

14. The device of claim 13, wherein the imaginary variable is the expression y=x−

k1/k0·

{dot over (x)}+1/m·

(mB−

k1/k0)·

xB−

mB/m·

k1/k0·

{dot over (x)}B, where y is the imaginary variable, x is a position of a center of said body, xB is a position of a center of said base, x and {dot over (x)}B are the time base derivatives of x and xB, respectively, m is a mass of said body, mB is a mass of said base, k0 is a natural frequency of said base and k1 is a damping of said base.

15. The device of claim 14, wherein the force profile causes said base to have a positive displacement and then a negative displacement when said body is moved by said actuator.

16. The device of claim 14, wherein the imaginary variable is expressed as a polynomial.

17. The device of claim 14, wherein the imaginary variable is expressed as a sinusoidal decomposition.

18. A method for moving a body relative to a base, comprising:

calculating a control command to move the body with a force; and

,

exerting a force onto the body, the force having a force profile that causes the body to move from a start position at a start time to an end position at an end time, so that said base has a zero displacement at the end time, the force profile being dependent on parameters related to said base and said body, said parameters vary as said body moves from the start to end positions.

19. The method of claim 18, wherein the force profile is dependent upon an imaginary variable.

20. The method of claim 19, wherein the imaginary variable is the expression y=x−

k1/k0·

{dot over (x)}+1/m·

(mB−

k1/k0)·

xB−

mB/m·

k1/k0·

{dot over (x)}B, where y is the imaginary variable, x is a position of a center of the body, xB is a position of a center of the base, {dot over (x)} and {dot over (x)}B are the time base derivatives of x and xB, respectively, m is a mass of the body, mB is a mass of the base, k0 is a natural frequency of the base and k1 is a damping of the base.

21. The method of claim 20, wherein the imaginary variable is expressed as a polynomial.

22. The method of claim 20, wherein the imaginary variable is expressed as a sinusoidal decomposition.