INDUCTIVE NON-CONTACT MEASUREMENT OF A RELATIVE MOVEMENT OR RELATIVE POSITIONING OF A FIRST OBJECT RELATIVE TO A SECOND OBJECT

• US 20090140729A1
• Filed: 07/05/2006
• Published: 06/04/2009
• Est. Priority Date: 07/07/2005
• Status: Active Grant

• Current Assignee: Fogale Sensors
• Original Assignee: Nanotec Corporation
• Inventors: Roziere, Didier
• Granted Patent: US 8,159,213 B2
• Time in Patent Office: Days
• US Class Current: 324/207.170
• CPC Class Codes: G01D 5/2086 by movement of two or more coils with respect to two or more other coils
• CPC Class Codes: G01D 5/2291 Linear or rotary variable differential transformers (LVDTs/RVDTs) having a single primary coil and two secondary coils

Abstract

A non-contact measurement method for a relative displacement or relative positioning of a first object relative to a second object, in which: at least one transmitting coil, placed on the first object, is excited by an alternating excitation signal, at least one alternating electronic output signal, generated by mutual inductance in at least one receiving coil, is detected; the at least one receiving coil being placed on the second object and in a magnetic field created by the at least one transmitting coil, and the relative displacement of the first object is determined relative to the second object using the at least one alternating electric output signal generated on the at least one receiving coil.

Claims

1. A non-contact measurement method for a relative displacement or relative positioning of a first object relative to a second object, in which:

at least one transmitting coil, placed on the first object, is excited by an alternating excitation signal,

at least one alternating electronic output signal, generated by mutual inductance in at least one receiving coil, is detected;

said at least one receiving coil being placed on said second object and in a magnetic field created by said at least one transmitting coil, and

the relative displacement of the first object is determined relative to the second object using said at least one alternating electric output signal generated on said at least one receiving coil.

2. The method according to claim 1 characterized in that said at least one transmitting coil and said at least one receiving coil constitute a transformer.

3. The method according to claim 1, characterized in that an axial displacement is determined by measuring a continuous axial voltage Va that is proportional to a monotone function of mutual inductance M between a transmitting coil and a receiving coil.

4. The method according to claim 1, characterized in that at least two receiving coils are used which generate, respectively, an alternating voltage va that is proportional to mutual inductance Ma between a first receiving coil and said at least one transmitting coil, and an alternating voltage vb that is proportional to the mutual inductance Mb between a second receiving coil and said at least one transmitting coil.

5. The method according to claim 4, characterized in that a radial displacement is determined by measuring a continuous radial voltage Vr proportional to the relation (Ma−

Mb)·

f(Ma+Mb);

where (Ma−

Mb) is the difference between mutual inductances Ma and Mb, where f(Ma+Mb) is a monotone function of the sum (Ma+Mb) of mutual inductances Ma and Mb;

where Ma is the mutual inductance between said at least one transmitting coil and a first receiving coil, where Mb is the mutual inductance between said at least one transmitting coil and a second receiving coil.

6. The method according to claim 4, characterized in that an axial displacement is determined by measuring a continuous axial voltage Va which is proportional to a monotone function of the sum of mutual inductances Ma and Mb, where Ma is the mutual inductance between said at least one transmitting coil and a first receiving coil, where Mb is the mutual inductance between the transmitting coil and a second receiving coil.

7. The method according to claim 3, characterized in that said monotone function consists of an inverse function.

8. The method according to claim 3, characterized in that the amplitude of the excitation signal of said at least one transmitting coil is triggered by continuous axial voltage Va.

9. The method according to claim 1, characterized in that the amplitude of the excitation signal is held constant;

and to measure the relative displacement, means of calculating continuous voltage Va is triggered by this continuous axial voltage Va.

10. The method according to claim 1, characterized in that two transmitting coils and at least one receiving coil are used;

for a given coil position, an inductance equilibrium voltage is determined at the output of the receiving coil, and the radial position of the two objects is triggered by said equilibrium voltage.

11. The method according to claim 10, characterized in that the equilibrium voltage is null.

12. The method according to claim 10, characterized in that the two coils are excited by two opposite excitation signals.

13. The method according to claim 1, characterized in that said at least one transmitting coil is arranged facing the receiving coils.

14. The method according to claim 1, characterized in that differential coils are used.

15. The method according to claim 1, characterized in that the coils are rectangular, square or circular in shape.

16. The method according to claim 1, characterized in that the coils are called flat or planar.

17. The method according to claim 1, characterized in that the coils are made in the shape of loops arranged directly on said objects.

18. The method according to claim 1, characterized in that the coils are made in the shape of loops arranged on flexible circuits, where these flexible circuits are arranged on said objects.

19. The method according to claim 1, characterized in that the coils are arranged on a material with a very low thermal expansion coefficient in order to greatly reduce the deformation of these arranged coils.

20. The method according to claim 1, characterized in that said alternating excitation signal is an alternating voltage.

21. The method according to claim 1, characterized in that said alternating excitation signal is an alternating current.

22. The method according to claim 1, characterized in that said alternating electric output signal is an alternating voltage.

23. The method according to claim 1, characterized in that said alternating electric output signal is an alternating current.

24. The method according to claim 1, characterized in that the transmitting and receiving coils are, respectively, arranged on two adjacent lateral sides of two mirrors of a telescope.

25. A system for measuring relative displacement or relative positioning of a first object relative to a second object, which implements a method according to any of the preceding claims, this system comprising:

at least one transmitting coil placed on said first object,

at least one receiving coil placed on the second object,

means of excitation for said at least one transmitting coil into an alternating excitation signal, and

means of processing for recovering at least one alternating electric output signal, generated by mutual inductance in said at least one receiving coil, and for determining the relative displacement of the first object in relation to the second object using said alternating electric output signal generated on the receiving coil.

26. The system according to claim 25, characterized in that it comprises a transmitting coil and a receiving coil for measuring an axial displacement of objects by determining an axial voltage Va that is proportional to a monotone function of the mutual inductance between the two coils.

27. The system according to claim 25, characterized in that it comprises two transmitting coils powered by two opposite excitation signals to control radial positioning.

28. The system according to claim 25, characterized in that it comprises two transmitting coils powered in series by the same alternating current.

29. The system according to claim 25, characterized in that it comprises two receiving coils mounted in series so that they determine the sum of two mutual inductances between each receiving coil and said at least one transmitting coil.

30. The system according to claim 25, characterized in that it comprises two receiving coils mounted differentially to determine the difference of two mutual inductances between each receiving coil and said at least one transmitting coil.

31. The system according to claim 25, characterized in that the processing means comprises means of calculation for determining a continuous voltage Vr which represents a radial displacement and which is proportional to the relation (Ma−

Mb)·

f(Ma+Mb);

where (Ma−

Mb) is the difference of mutual inductances Ma and Mb, f(Ma+Mb) is a monotone function of the sum (Ma+Mb) of mutual inductances Ma and Mb;

where Ma is the mutual inductance between the transmitting coil and a first receiving coil, where Mb is the mutual inductance between the transmitting coil and a second receiving coil.

32. The system according to claim 31, characterized in that means of calculation comprises:

an adder for adding the difference in alternating voltages va−

vb of two receiving coils with a feedback signal,

a demodulator for demodulating the signal emitted from said adder,

an integrator for generating the continuous radial voltage Vr using the signal generated by the demodulator, and

a multiplier powered by continuous radial voltage Vr and a reference voltage Vref for generating said feedback signal;

where the relative displacement is a function of the value of the continuous radial voltage Vr for which the output of said multiplier is null.

33. The system according to claim 31, characterized in that the calculation means comprises:

a multiplier-adder for adding the difference va−

vb in the voltages generated by the receiving coils with a feedback signal, multiplied by sum va+vb of the voltages generated by the receiving coils,

a demodulator for demodulating the signal emitted by said multiplier, and

an integrator for generating the continuous radial voltage Vr using the signal emitted by the demodulator, where said feedback signal is the continuous radial voltage Vr;

where the relative displacement is the function of the value of the continuous radial voltage Vr for which the output of said multiplier is null.

34. The system according to claim 25, characterized in that the processing means comprises means of calculation for determining a continuous axial voltage Va which represents an axial displacement and which is proportional to a monotone function of the sum of the mutual inductances Ma and Mb, where Ma is the mutual inductance between the transmitting coil and a first receiving coil, and where Mb is the mutual inductance between the transmitting coil and a second receiving coil.

35. The system according to claim 26, characterized in that said monotone function comprises an inverse function.

36. The system according to claim 34, characterized in that means of calculation comprises:

an adder for adding the sum of alternating voltages va+vb of two receiving coils with a reference voltage Vref,

a demodulator for demodulating the signal emitted by said adder

an integrator for generating continuous axial voltage Va using the signal emitted by the demodulator, and

a multiplier that is powered by the continuous axial voltage Va and the reference voltage Vref so that said excitation signal is generated;

where the relative motion is a function of the value of Va for which the output of said adder is null.

37. The system according to claim 34, characterized in that means of calculation comprises:

a multiplier adder for adding a reference voltage Vref to a feedback signal multiplied by the sum va+vb of voltages generated by receiving coils,

a demodulator for demodulating the signal emitted by said multiplier, and

an integrator for generating the continuous axial voltage Va using the signal emitted by the demodulator, where the feedback signal is the continuous axial voltage Va; and

where the relative displacement is a function of the value of the continuous axial voltage Va for which the output of said multiplier is null.

38. The system according to claim 32, characterized in that, for all calculations, the reference voltage Vref is multiplied by a coefficient.

39. The system according to claim 25, characterized in that the processing method comprises an adding amplifier designed to produce the sum va+vb of the voltages generated by the receiving coils.

40. The system according to claim 25, characterized in that the processing method comprise a differential amplifier designed to produce the difference va−

vb of voltages generated by the receiving coils.

41. Application of the method according to claim 1 for controlling the position of the segmented telescope mirrors.

42. Application of the method according to claim 1 for controlling the alignment of the segmented telescope mirrors.

43. Application of the non-contact measuring system according to claim 25, for measuring the relative position between two adjacent mirror segments.

44. The application according to claim 43, in which plates that are respectively transmitter and receiver are attached to lateral walls facing two adjacent mirror segments, in close proximity to the active surfaces of said mirror segments.

45. The application according to claim 44, in which a non-contact measurement system for measuring relative displacement or relative positioning of a first object relative to a second object, which implements a method according to any of the preceding claims, this system comprising:

at least one transmitting coil placed on said first object,

at least one receiving coil placed on the second object

means of excitation for said at least one transmitting coil into an alternating excitation signal, and

means of processing for recovering at least one alternating electric output signal, generated by mutual inductance in said at least one receiving coil, and for determining the relative displacement of the first object in relation to the second object using said alternating electric output signal generated on the receiving coil is implemented for controlling the position (Tilt, Tip, piston and global radius of curvature (GROC) of the mirror) of the mirror'"'"'s segments.

46. The application according to claim 43, in the sector of large-size, segmented-mirror telescopes.

47. The application of the non-contact measurement system according to claim 25, for non-contact measurement of position and displacement in one or two axes.