Accelerometer based angular position sensor

• US 6,873,931 B1
• Filed: 10/10/2000
• Issued: 03/29/2005
• Est. Priority Date: 10/10/2000
• Status: Expired due to Term

• Current Assignee: Computational Systems Incorporated (Emerson Electric Company)
• Original Assignee: CSI Technology Incorporated (Emerson Electric Company)
• Inventors: Nower, Daniel L., Abnett, Albert C., Hinkle, David A.
• Primary Examiner(s): Bui, Bryan
• Assistant Examiner(s): Lau, Tung S
• Application Number:
  US09/685,317
• Time in Patent Office: 1,631 Days
• Field of Search: 702/151, 702/195, 702/141, 473/316, 473/219, 473/289, 738/54, 735/79, 735/10, 297/20, 294/07, 356/477, 356/141, 356/35, 318/651, 318/571, 324/202, 324/207, 700/264, 700/183, 404/84, 304/18, 188/378, 340/686.3, 414/699, 600/109, 785/10
• US Class Current: 702/151
• CPC Class Codes: G01B 11/272 using photoelectric detection means
• CPC Class Codes: G01C 9/06 Electric or photoelectric indication or reading means
• CPC Class Codes: G01C 9/08 Means for compensating acceleration forces due to movement of instrument

Abstract

An alignment system having an angular position sensing device using an accelerometer to determine the angular position of the device. Preferably, the angular position sensing device incorporates two dual-axis accelerometers oriented in a spaced apart relation for determining the angular position of a rotating body in space. The angular position sensing device is operable to account for centrifugal and angular acceleration errors due to the rotation of the rotating body in space, thereby providing an accurate angular position of the rotating body. The angular position sensor also determines the angular position of the rotating body based on a sensing axis having the greatest range of sensitivity according to the angular position of the rotating body.

Claims

1. An alignment system for aligning a centerline of a first shaft with a centerline of a second shaft comprising:

an analyzer having memory,

a mounting bracket having engagement surfaces for engaging the first shaft and securing the bracket to the first shaft,

a sensor head having a facing surface and a rear surface in opposing relation disposed on the mounting bracket and extending in a substantially perpendicular orientation with respect to the centerline of the first shaft,

a collimated light source mounted on the sensor head for transmitting a beam of energy in a direction that is substantially parallel to the first shaft,

a photosensitive sensor mounted on the sensor head for sensing light and generating a position signal corresponding to a position of a light beam impinging upon the photosensitive sensor,

at least one accelerometer mounted on the sensor head for generating a signal corresponding to the angular orientation of the sensor head with respect to the first shaft, and

a microprocessor for processing the signal generated by the at least one accelerometer, operable to provide an output corresponding to the angular position of the sensor head relative to the first shaft.

2. An alignment system for aligning a centerline of a first shaft with a centerline of a second shaft comprising:

an analyzer having memory,

a mounting bracket having engagement surfaces for engaging the first shaft and securing the bracket to the first shaft,

a sensor head having a facing surface and a rear surface in opposing relation disposed on the mounting bracket and extending in a substantially perpendicular orientation with respect to the centerline of the first shaft,

a collimated light source mounted on the sensor head for transmitting a beam of energy in a direction that is substantially parallel to the first shaft,

a photosensitive sensor mounted on the sensor head for sensing light and generating a position signal corresponding to a position of a light beam impinging upon the photosensitive sensor,

at least one accelerometer for generating a signal corresponding to the angular orientation of the sensor head with respect to the first shaft, and

a microprocessor for processing the signal generated by the at least one accelerometer, wherein the microprocessor further comprises an angle processing module for determining a current head quadrant location and determining the angular position of the sensor head based in part on the quadrant location, the microprocessor providing an output corresponding to the angular position of the sensor head relative to the first shaft.

3. The angular position sensing apparatus of claim 2, wherein the at least one accelerometer is a single-axis accelerometer for generating a signal proportional to the angular orientation of the sensor head.

4. The angular position sensing apparatus of claim 2, wherein the at least one accelerometer is a dual-axis accelerometer having a radial and a tangential axis, for generating radial and tangential signals proportional to the angular orientation of the sensor head.

5. An alignment system for aligning a centerline of a first shaft with a centerline of a second shaft comprising:

an analyzer having memory,

a mounting bracket having engagement surfaces for engaging, the first shaft and securing the bracket to the first shy

a sensor head having a facing surface and a rear surface in opposing relation disposed on the mounting bracket and extending in a substantial perpendicular orientation with respect to the centerline of the first shaft,

a collimated light source mounted on the sensor head for transmitting a beam of energy in a direction that is substantially parallel to the first shaft,

a photosensitive sensor mounted on the sensor head for sensing light and generating a position signal corresponding to a position of a light beam impinging upon the photosensitive sensor,

a first dual-axis accelerometer having a first sensing axis for sensing a first acceleration component and a second sensing axis for sensing a second acceleration component, wherein the first and second sensing axes are in substantially perpendicular relation, the first dual-axis accelerometer operable to output a first signal proportional to the sensed first acceleration component and to output a second signal proportional to the sensed second acceleration component,

a second dual-axis accelerometer having a third sensing axis for sensing a third acceleration component and a fourth sensing axis for sensing a fourth acceleration component, wherein the third and fourth sensing axes are in substantially perpendicular relation, the second dual-axis accelerometer operable to output a third signal proportional to the sensed third acceleration component and to output a fourth signal proportional to the sensed fourth acceleration component, the first and second dual-axis accelerometers mounted in spaced apart relation defining a plane of reference, and

a microprocessor for processing the signals generated by the first and second dual-axis accelerometers, operable to provide an output corresponding to the angular position of the sensor head relative to the first shaft.

6. The apparatus of claim 5, wherein the microprocessor is operable to determine the angular position of the sensor head as the sensor head rotates through a plurality of angular positions about the first shaft by selecting a fifth signal dependent on the first and third signals or a sixth signal dependent on the second and fourth signals and determining the angular position of the rotatable body therefrom.

7. The angular position sensing apparatus of claim 6 wherein the fifth signal corresponds to a first sine wave function and the sixth signal corresponds to a second sine wave function ninety degrees out of phase with respect to the first sine wave function, wherein the microprocessor determines the angular position of the body based on a most linear region of the first or second sine waves.

8. The angular position sensing apparatus of claim 5 further comprising processing features for processing the signals from the first and second dual-axis accelerometers to correct for centrifugal and angular acceleration effects.

9. A alignment system for aligning a first shaft comprising:

a sensor head coupled to the first shaft,

a collimated light source disposed on the sensor head for transmitting an energy beam,

a photosensitive sensor disposed on the sensor head for sensing light and generating a position signal therefrom,

a first dual-axis accelerometer having a first sensing axis for sensing a first acceleration component and a second sensing axis for sensing a second acceleration component, wherein the first and second sensing axes are in substantially perpendicular relation, the first dual-axis accelerometer operable to output a first signal proportional to the sensed first acceleration component and to output a second signal proportional to the sensed second acceleration component, and

a second dual-axis accelerometer having a third sensing axis for sensing a third acceleration component and a fourth sensing axis for sensing a fourth acceleration component, wherein the third and fourth sensing axes are in substantially perpendicular relation, the second dual-axis accelerometer operable to output a third signal proportional to the sensed third acceleration component and to output a fourth signal proportional to the sensed fourth acceleration component, and

a processor for processing the signals generated by the fist and second dual-axis accelerometers, operable to provide an output corresponding to the angular position of the sensor head relative to the first shaft.