Sensing system for determining an articulation angle between two elements

• US 6,218,828 B1
• Filed: 12/21/1998
• Issued: 04/17/2001
• Est. Priority Date: 12/21/1998
• Status: Expired due to Fees

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Bates, Kent C., Strashny, Igor
• Primary Examiner(s): Oda, Christine
• Assistant Examiner(s): ZAVERI, SUBHASH
• Application Number:
  US09/217,369
• Time in Patent Office: 848 Days
• Field of Search: 324/207.2, 324/207.21, 324/207.22, 324/207.24, 324/207.25, 324/207.26, 324/207.14, 324/207.11, 324/225, 324/235, 338/32.H, 338/32.R
• US Class Current: 324/207.2
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

The present invention provides an apparatus and a method for determining the position of a first element relative to a second element. The apparatus includes a magnet being attached to the first element. First and second sensing devices are adapted to detect a magnetic flux density produced by the magnet and responsively generating first and second signals. The apparatus also includes a controller for receiving the first and second signals and responsively determining the position of the first element relative to the second. The present invention enables continuous calibration during the normal operation of the machine.

Claims

1. An apparatus for determining the position of a first and a second element relative to each other comprising:

a magnet being attached to the first element, said magnet having a magnetic flux density;

a first sensing device being adapted to detect said magnetic flux density and responsively generate a first signal, said first device being attached to said second element;

a second sensing device being adapted to detect said magnetic flux density and responsively generate a second signal, said second device being attached to said second element; and

a controller adapted to receive said first and said second signals and responsively determine a position of said first element relative to said second element.

2. An apparatus, as set forth in claim 1, wherein said first and said second sensing device are attached in a manner such that a first slope of a first transfer function represented by said first signal is an inverse of a second slope of a second transfer function represented by said second signal.

3. An apparatus, as set forth in claim 1, wherein said first and said second sensing device are attached in a manner such that a first slope of a first transfer function representing said magnetic flux density detected by said first sensing device is an inverse of a second slope of a second transfer function representing said magnetic flux density detected by said second sensing device.

4. An apparatus, as set forth in claim 2, wherein said controller determines said first and second sensing devices are located equadistance from a north and a south pole of said magnet when a magnitude of said first signal is within a threshold of a magnitude of said second signal.

5. An apparatus, as set forth in claim 4, wherein said controller determines an angular position of said first element relative to said second element in response to said first signal magnitude and said second signal magnitude.

14. An apparatus, as set forth in claim 1, wherein said controller is further configured to determine a zero point of said magnet in response to the magnitude of the first signal being within a threshold of the magnitude of the second signal.

15. An apparatus, as set forth in claim 14, wherein said controller is further configured to determine said articulation angle in response to the zero point, and one of said first and said second signals.

6. A method for determining a position of a first element having a magnet and a second element having a plurality of sensing devices, relative to each other, said magnet having a magnetic flux density, the method comprising the steps of:

sensing said magnetic flux density with said first sensing device and responsively generating a first signal;

sensing said magnetic flux density with said second sensing device and responsively generating a second signal; and

determining a position of said first element relative to said second element in response to said first and said second signals.

7. A method, as set forth in claim 6, wherein said first sensing device is located adjacent to said second sensing device in a manner such that a first slope of a first transfer function represented by said first signal is an inverse of a second slope of a second transfer function represented by said second signal.

8. A method, as set forth in claim 6, wherein said first and said second sensing device are attached in a manner such that a first slope of a first transfer function representing said magnetic flux density detected by said first sensing device is an inverse of a second slope of a second transfer function representing said magnetic flux density detected by said second sensing device.

9. A method, as set forth in claim 6, wherein the step of determining said position further comprises the steps of:

comparing said magnitude of said first and said second signals; and

determining said position in response to said comparison.

10. A method, as set forth in claim 9, wherein the step of determining said position in response to said comparison further comprises the step of determining said first and second sensing devices are located equadistance from a north and a south pole of said magnet when a magnitude of said first signal is within a threshold of a magnitude of said second signal.

11. A method, as set forth in claim 6, further including the step of determining a zero point of the magnet in response to the magnitude of the first signal being within a threshold of the magnitude of the second signal.

12. A method, as set forth in claim 11, further including the step of determining said articulation angle in response to the zero point, and one of said first and said second signals.

13. A method, as set forth in claim 11, further including the step of determining said articulation angle in response to the zero point, and at least one of said first and said second signals.