Systems and methods of clamp compensation

Patent metadata

Field	Value
Publication number	US-12057286-B2
Application number	US-202218084430-A
Country	US
Kind code	B2
Filing date	Dec 19, 2022
Priority date	Nov 15, 2019
Publication date	Aug 6, 2024
Grant date	Aug 6, 2024

Abstract

A method of producing a compensation signal to compensate for misalignment of a drive unit clamp element can include applying a clamp element drive signal to a drive unit clamp element to engage a mover element, determining a first displacement of the mover element, and determining a first compensation signal based at least in part on the first displacement. The method can further comprise applying the first compensation signal to the drive unit shear elements and the clamp element drive signal to the drive unit clamp element and determining a second displacement of the mover element. If the second displacement is less than a preselected threshold, the first compensation signal can be combined with an initial shear element drive signal to produce a modified shear element drive signal. If the second displacement is greater than the preselected threshold, a second compensation signal can be determined.

First claim

We claim:

1. A method, comprising:
applying a clamp element drive signal to a drive unit clamp element to engage a mover element;
determining a first displacement of the mover element;
determining a first compensation signal to be applied to one or more drive unit shear elements based at least in part on the first displacement;
applying the first compensation signal to the one or more drive unit shear elements and the clamp element drive signal to the drive unit clamp element;
determining a second displacement of the mover element in response to the first compensation signal and the clamp element drive signal; and
comparing the second displacement to a preselected threshold;
for a second displacement less than the preselected threshold, combining the first compensation signal with an initial shear element drive signal to produce a modified shear element drive signal; and
for a second displacement greater than the preselected threshold, determining a second compensation signal to be applied to the one or more drive unit shear elements.

2. The method of claim 1 , further comprising applying the clamp element drive signal to the drive unit clamp element while applying the modified shear element drive signal to the one or more drive unit shear elements.

3. The method of claim 1 , wherein determining the compensation signal comprises multiplying the displacement of the mover element by an inverse shear constant of the one or more shear elements.

4. The method of claim 1 , further comprising:
applying the first compensation signal and the second compensation signal to the one or more drive unit shear elements and the clamp element drive signal to the drive unit clamp element;
determining a third displacement of the mover element;
comparing the third displacement to the preselected threshold; and
for a third displacement less than the preselected threshold, combining the second compensation signal with an initial shear element drive signal to produce a modified shear element drive signal; and
for a third displacement greater than the preselected threshold, determining a third compensation signal to be applied to the one or more drive unit shear elements.

5. The method of claim 4 , wherein the compensation signal is a first compensation signal, and wherein determining the second compensation signal comprises multiplying the second displacement of the mover element by an inverse shear constant of the one or more shear elements and subtracting the result from the first compensation signal.

6. The method of claim 1 , wherein determining the displacement of the mover element comprises measuring the displacement of the mover element with a position encoder.

7. The method of claim 1 , wherein the displacement of the mover element is caused at least in part by misalignment between the drive unit clamp element and the mover element.

8. The method of claim 1 , wherein the drive unit clamp element and the one or more drive unit shear elements together comprise a drive unit, and wherein the drive unit is a walking piezo drive unit.

9. The method of claim 8 , wherein the drive unit clamp element is positioned adjacent a first surface of the mover element, and the one or more drive unit shear elements are positioned adjacent a second surface of the mover element opposite the first surface.

10. The method of claim 9 , wherein the drive unit clamp element comprises a clamp piezo element and a shear piezo element.

11. A method, comprising:
applying a clamp element drive signal to a clamp element to engage a mover element, the clamp element and a shear element together comprising a drive unit wherein a contact surface of the drive unit contacts a surface of the mover element at a non-perpendicular contact angle causing the mover element to move by a first displacement;
determining the first displacement of the mover element;
determining a first compensation signal to be applied the shear element based at least in part on the first displacement;
applying an initial shear element drive signal to the shear element and the clamp element drive signal to the clamp element to move the mover element a second distance;
determining a second displacement of the mover element in response to the first compensation signal and the clamp element drive signal, the second displacement due at least in part to the non-perpendicular contact angle; and
comparing the second displacement to a preselected threshold;
for a second displacement less than the preselected threshold, combining the first compensation signal with the initial shear element drive signal to produce a modified shear element drive signal; and
for a second displacement greater than the preselected threshold, determining a second compensation signal to be applied to the one or more drive unit shear elements.

12. The method of claim 11 , wherein the preselected threshold is between 10 nm to 100 nm.

13. The method of claim 11 , further comprising repeating the steps of determining the second displacement of the mover element in response to the first compensation signal and the clamp element drive signal, the second displacement due at least in part to the non-perpendicular contact angle, and comparing the second displacement to a preselected threshold until the second displacement is below than the preselected threshold.

14. The method of claim 11 , wherein the compensation signal is generated using an iterative learning control (ILC) scheme.

15. The method of claim 11 , wherein the drive unit is a first drive unit and wherein the method further comprises applying the clamp element drive signal to a second drive unit positioned adjacent to an opposing surface of the mover element.

16. The method of claim 11 , wherein the modified shear element drive signal compensates at least in part for the second displacement by causing movement of the drive unit shear element and the mover element in a direction opposite the direction of movement of the mover element caused by contact with the drive unit.

17. The method of claim 11 , wherein the clamp elements are longitudinal piezo elements.

18. The method of claim 11 , wherein the shear elements are shear piezo elements.

19. The method of claim 11 , wherein the drive unit is a walking piezo drive unit comprising first, second, and third actuators, the first actuator being positioned adjacent a first surface of the mover element and the second and third actuators being positioned adjacent a second surface of the mover element opposite the first surface.

20. The method of claim 19 , wherein the first actuator comprises a clamp piezo element and a shear piezo element, and wherein the second and third actuators each comprise a shear piezo element.

Assignees

• Fei Co

Inventors

• Verschueren Edwin
• Tacx Paul

Classifications

• H01J2237/2802

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• H01J2237/20264

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• H01J2237/20221

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• H01J37/28

  with scanning beams {(H01J37/268, H01J37/292, H01J37/2955 take precedence)} · CPC title