Method and apparatus for the evaluation of an angle over an extended range

• US 4,852,026 A
• Filed: 06/25/1986
• Issued: 07/25/1989
• Est. Priority Date: 07/09/1985
• Status: Expired due to Fees

• Current Assignee: Enertec SA (Vitec Group PLC)
• Original Assignee: Enertec SA (Vitec Group PLC)
• Inventors: Berard, Michel
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): Ramirez, Ellis B.
• Application Number:
  US06/879,196
• Time in Patent Office: 1,126 Days
• Field of Search: 356/72, 356/368, 200/225, 200/231 SE, 364/556, 324/83 Y, 324/83 D, 324/96, 350/374, 350/375
• US Class Current: 702/198
• CPC Class Codes: G01R 15/247 Details of the circuitry or construction of devices covered by G01R15/241 - G01R15/246
• CPC Class Codes: G06F 7/548 Trigonometric functions; Co-ordinate transformations
• CPC Class Codes: G06F 7/62 Performing operations exclusively by counting total number of pulses ; Multiplication, division or derived operations using combined denominational and incremental processing by counters, i.e. without column shift G06F7/68 takes precedence
• CPC Class Codes: G06J 1/00 Hybrid computing arrangements digitally-programmed analogue computers G06G7/06

Abstract

A method and device for evaluating an angle A known by at least two trigonometric functions and capable of varying over a range greater than 360°.

Two counter integers N₀, N₁ are stored and up-dated, each with respect to the other, as a function of even and odd indicator signals FC₂, FS₂.

The value of the angle A, expressed in quarter turns, is given by the first or the second counter number as a function of the value of the even indicator signal FC₂.

Claims

1. A method for evaluating the variation, from an initial instant, of an angle A capable of varying over a range greater than 90°

, by using instantaneous values of at least an even indicator signal FC₂ and an odd indicator FS₂, respectively related to the signs of the cosine and the sine of a double angle 2A, comprising the steps of;

(a) putting and storing in memory, at an initial instant, two counter numbers, N₀, N₁ ;

(b) defining a localization parameter X by assigning to it, as a function of the instantaneous value of the even indicator signal, the value of one of the counter numbers N₀, N₁ ;

(c) reading out the other of the counter numbers N₀, N₁, by assigning it as a new value that of the localization parameter X increased or decreased by one in dependence upon the instantaneous value of the product of the two indicator signals;

(d) selectively repeating the previous steps (b) and (c) in the course of time; and

(e) producing at least a first output signal related to the localization parameter X, variation of which, expressed in multiples of quarter turns, represents the variation of the angle A since the initial instant in corresponding multiples of 90°

.

2. A method according to claim 1, wherein:

the even and the odd indicator signals are respective direct representations of the signs of the cosine and the sine of the double angle 2A.

3. A method according to claim 1, wherein:

the counter number reset during step (c) takes the value of the localization parameter X increased by one if the product of the indicator signals is positive and decreased by one if said product is negative.

4. A method according to claim 1, further comprising the steps of:

receiving a cosine tracking signal C proportional to the cosine of the angle A and a sine tracking signal S proportional to the sine of the angle A;

choosing a measurement signal M respectively proportional to the cosine and sine tracking signals when the even indicator signal is respectively negative and positive; and

improving the evaluation of the angle A by assigning to this angle the value represented by the algebraic sum of the first output signal and a second output signal equal to an inverse trigonometrical function of the measurement signal M.

5. A method according to claim 4, wherein:

the angle A is evaluated from the expression

space="preserve" listing-type="equation">X·

90°

+(FC.sub.2)·

(FS.sub.2) Arc sin M,

wherein X is the localization parameter, (FC₂) and (FS₂) are respectively the even and odd indicator signals taking the values +1 or -1 following the positive or negative sign of the cosine and the sine of the double angle 2A respectively, and where M designates the absolute value of the measurement signal.

6. A method according to claim 4, wherein:

the angle A is evaluated from the expression

space="preserve" listing-type="equation">X=90°

+FD·

Arc sin M,

where X is the localization parameter, FD is an out-of-phase indicator signal, taking the values +1 or -1 according to the sign of the difference C-S of the cosine and sine tracking signals, and where M is the measurement signal.

7. Apparatus for evaluating the variation, from an initial instant, of an angle A that can vary over a range greater than 90°

, by using at least an even indicator signal FC₂ and an odd indicator signal FS₂ respectively related to the cosine and sine of the double angle 2A, comprising;

two read/write memories;

memory reading address means responsive to the even indicator signal and adapted to deliver as a first output of the apparatus a duplication signal X representative of the contents of one of the two memories, selected according to the value of the even indicator signal (FC₂);

an operator circuit adapted, according to the value of the product of the indicator signals, to increment or decrement the value of the duplication signal X; and

memory writing address means adapted to write in that one of the two memories which was not selected the value of the duplication signal X as modified by the operator circuit.

8. A device according to claim 7, further comprising:

an inverse trigonometric function conversion circuit receiving a measurement signal M related, as a function of the value of the even indicator signal, either to the cosine of the angle A or the sine of the angle A, and supplying at a second output of the apparatus a signal representative of an inverse trigonometrical function of the measurement signal M.