Position measuring apparatus and method

• US 4,885,725 A
• Filed: 11/12/1987
• Issued: 12/05/1989
• Est. Priority Date: 03/12/1986
• Status: Expired due to Term

• Current Assignee: MS Instruments PLC Electron House
• Original Assignee: MS Instruments Public Limited Company
• Inventors: McCarthy, Brian D., Regan, Bernard J.
• Primary Examiner(s): STEINBERGER, BRIAN
• Application Number:
  US07/124,935
• Time in Patent Office: 754 Days
• Field of Search: 367/89, 367/117, 367/118, 367/121, 367/124, 367/129, 367/906, 367/127, 273/372
• US Class Current: 367/129
• CPC Class Codes: F41J 5/06 Acoustic hit-indicating systems, i.e. detecting of shock waves F41J5/056 takes precedence
• CPC Class Codes: G01S 11/14 using ultrasonic, sonic, or infrasonic waves
• CPC Class Codes: G01S 5/20 Position of source determined by a plurality of spaced direction-finders
• CPC Class Codes: Y10S 367/906 Airborne shock-wave detection

Abstract

The position of a projectile travelling at a supersonic velocity is sensed by two triangular arrays of transducers 10,11 which are located below and close to the plane of a target area 14 through which the projectile passes. Signals from the transducers are processed to obtain data indicative of the direction of the trajectory from each array. This data can be processed to obtain the position of the trajectory in a cartesian coordinate system.

Claims

1. Apparatus for determining the position within a target area of the trajectory of a projectile travelling at a supersonic velocity to said target area, said apparatus comprising:

a plurality of transducers, said transducers being so arranged and disposed that they form two spaced-apart triangular groups which are associated with the plane of the target area through which the projectile passes,

each transducer being arranged to convert the mechanical impulse of a shock wave from the projectile into an electrical signal, and

processing means connected to receive said electrical signals and arranged to compute from said signals the direction of the projectile from each group of sensors, and to compute the position of the trajectory of said projectile within said target area in a coordinate system from said computed directions.

2. Apparatus according to claim 1 wherein said transducers comprise two spaced groups each comprising three transducers, the spacing of said groups being greater than the spacing of the transducers in each group.

3. Apparatus according to claim 2 wherein the triangular arrangement is a right-angled triangle.

4. Apparatus according to claim 2 wherein the triangular arrangement is an equilateral triangle.

5. Apparatus according to claim 2 including a fourth transducer arranged out of the plane of the other three so that the velocity of the projectile can be derived.

6. Apparatus according to claim 1 further including:

means for sensing a cross-wind component,

said processing means receiving electrical signals from said means for sensing and changing said computed direction on the basis of said received signals.

7. A method of determining the position within a target area of a projectile travelling at a supersonic velocity using a plurality of transducers which are so arranged and disposed that they form two spaced-apart triangular groups associated with a target area through which the projectile passes, the method comprising:

sensing the impulse of a shock wave from the projectile at the transducers,

processing the sensed impulses to derive the direction with respect to the moving projectile as it passes through the target area from each group of sensors, and

evaluating and locating the position of the moving projectile within said target area as it passes through the target area.

8. Apparatus for determining the position of a projectile within a target area as it travels at a supersonic velocity through the target area, said apparatus comprising:

a longitudinally extending member arranged in a generally horizontal plane below the target area,

a pair of transducers located on said member, said transducers being at a given distance apart along the length of the member and each transducer being capable of transducing mechanical vibration into electrical signals,

a triangular array of transducers which is associated with a plane containing the target area,

each of said transducers being capable of converting the mechanical impulse of a shock wave into an electrical signal, and

means for processing signals from said transducers to provide date indicative of the position of the projectile within the target area as it passes therethrough.

9. Apparatus according to claim 8 wherein signals from the triangular array are used to derive data indicative of the direction from the array to the projectile trajectory and signals from the longitudinal member transducers are used to derive data indicative of the x position of the trajectory in an x-y coordinate system.

10. A method of determining the position of a projectile travelling at a supersonic velocity through a target area which comprises:

using a triangular array of transducers to sense the impulse of a shock wave from the projectile to derive data indicative of the direction of the projectile trajectory from the array,

using a rod type sensor to derive data indicative of the position of the trajectory on an axis of a rectangular coordinate system, and

computing the position on another axis of said coordinate system from the derived data from the rod type sensor.

11. Apparatus for determining the hit location in a target area through which a projectile passes, said apparatus comprising:

a generally planar target area;

a first group of plural first transducers located at a first predetermined position in a plane substantially parallel with said target area to intercept a shock wave emanating from the projectile upon its passage through the target area with the shock wave striking different ones of the first transducers at different times;

a second group of plural second transducers also located at a second predetermined position in a plane substantially parallel with said target area to intercept a shock wave emanating from the projectile upon its passage through the said target area with the shock wave striking different ones of the second transducers at different times;

timing and computing circuits connected to receive differently timed electrical signals from said first and second transducers and to responsively compute the direction from each said group to said hit position and, from the intersection of such computed directions, to locate the hit position within the said target area through which the projectile has passed.