Absolute incremental hybrid shaft position encoder

• US 4,041,483 A
• Filed: 04/18/1975
• Issued: 08/09/1977
• Est. Priority Date: 04/18/1975
• Status: Expired due to Term

• Current Assignee: Rockwell International Corporation
• Original Assignee: Rockwell International Corporation
• Inventors: Groff, Alvin H.
• Primary Examiner(s): Sloyan, Thomas J.
• Application Number:
  US05/569,414
• Time in Patent Office: 844 Days
• Field of Search: 340/347 P, 340/347 M, 250/231 SE
• US Class Current: 341/9
• CPC Class Codes: G01D 2205/28 The target being driven in rotation by additional gears
• CPC Class Codes: H03M 1/305 for detecting the direction of movement

Abstract

An incremental type shaft position encoder which provides a distinguishable signal at each of a plurality of predetermined shaft rotational positions, and which further provides a unique electrical signature associated with each of predetermined ones of the signals.

Claims

1. Shaft position encoder means comprising:

a. first means including a first coded track and an associated first sensor means between which relative movement is caused by rotation of said shaft, said first sensor means being arranged so as to be sensitive only to said first track, and said first sensor means generating, in response to said relative movement within said first means, a first signal at each of substantially regular angular intervals α

of rotation of said shaft,

b. second means including a second coded track and an associated second sensor means between which relative movement is also caused by rotation of said shaft, said second sensor means being arranged so as to be sensitive only to said second track, and said second sensor means generating, in response to said relative movement within said second means, a second signal at each of substantially regular angular intervals β

of rotation of said shaft, where β

=M/N×

α

, and M and N are positive intergers >

1 which contain no prime factor, other than the prime number one, which is common to both, and

c. third means including a third coded track and an associated third sensor means between which relative movement is also caused by rotation of said shaft, said third sensor means being arranged so as to be sensitive only to said third track, and said third sensor means generating, in response to said relative movement within said third means, a voltage or current transition at each of substantially regular angular intervals β

/M/k of rotation of said shaft where k is a positive integer,

whereby for a predetermined direction and amount of shaft rotation each positionally different first signal has associated therewith a corresponding and identifying electrical signature comprising a predetermined number of said transitions occurring between the associated first signal and the second signal last occurring prior to the associated first signal, each said electrical signature being different from all the other electrical signatures within said predetermined amount of shaft rotation in that each said electrical signature comprises a different number of said transitions.

2. Apparatus as defined in claim 1 wherein said first and second sensor means comprise first and second sensors respectively, and said third sensor means comprises third and fourth sensors arranged relative to one another along said third track such that said third and fourth sensors alternate in generating said transitions.

3. Apparatus as defined in claim 2 wherein κ

=1.

4. Apparatus as defined in claim 3 wherein M×

α

=N×

β

=360°

of shaft rotation.

5. Apparatus as defined in claim 4 wherein M×

N/360 is a positive integer.

6. Apparatus as defined in claim 5 wherein M=32 and N=45.

7. Apparatus as defined in claim 2 including a fourth means comprising a fourth coded track and associated fifth and sixth sensors arranged so as to be sensitive only to said fourth track, relative movement between said fourth track and its associated sensors also being caused by rotation of said shaft, said fourth means generating, in response to said relative movement within said fourth means, a voltage or current transition at each of substantially regular angular intervals α

/P of rotation of said shaft where P=2γ and

γ

is a positive even integer, said fifth and sixth sensors being arranged relative to one another and relative to said fourth track such that said fifth and sixth sensors alternate in generating said transitions occurring at said α

/P intervals.

8. Apparatus as defined in claim 7 wherein P=2^S where S is a positive integer >

1.

9. Apparatus as defined in claim 8 wherein P is equal to any one of the following values:

16, 32, or 64.

10. Apparatus as defined in claim 9 wherein κ

=1.

11. Apparatus as defined in claim 10 wherein M×

α

=N×

β

=360°

of shaft rotation.