System and method for determining an instantaneous speed of a projectile

Abstract

A method of determining, with a processing device, an instantaneous speed of an arrow shot from a bow having a bow string is provided, the arrow shot at a target having a target-face. The method includes recording a signal that includes a first peak occurring substantially at a start of a free flight of the arrow and a second peak occurring substantially at a moment of impact of the arrow with the target, the start of the free-flight occurring when a proximate end of the arrow reaches substantially a neutral position of the bow string; processing the signal to determine a duration of the free flight of the arrow; determining a distance between a location from which the arrow is loosed and a location of the target-face; and determining the instantaneous speed of the arrow, at least in part, by employing each of the duration of the free flight and the distance.

What is claimed is: 
     
         1 . (canceled) 
     
     
         2 . A method of determining, with a processing device, an instantaneous speed of an arrow shot from a bow having a bow string, the arrow shot at a target having a target-face, the arrow having a length, the method comprising acts of:
 recording, with the processing device, a signal that includes a first peak occurring substantially at a start of a free flight of the arrow and a second peak occurring substantially at a moment of impact of the arrow with the target, the start of the free-flight occurring when a proximate end of the arrow reaches substantially a neutral position of the bow string;   processing the signal, with the processing device, to determine a duration of the free flight of the arrow;   determining a distance of the free flight as a distance substantially from the neutral position of the bow string to the target face less the length of the arrow; and   determining the instantaneous speed of the arrow with the processing device, at least in part, by employing each of the duration of the free flight and the distance of the free flight.   
     
     
         3 . The method of  claim 2 , further comprising employing a drag constant for the arrow in combination with the duration of the free flight and the distance to determine the instantaneous speed of the arrow. 
     
     
         4 . The method of  claim 3 , further comprising determining the drag constant based on an average value of acceleration for the arrow for a shot covering the distance. 
     
     
         5 . The method of  claim 4 , further comprising determining the drag constant based on an estimate of the average value of acceleration for the arrow for the shot covering the distance. 
     
     
         6 . The method of  claim 4 , wherein the arrow includes an on-board data acquisition system, and wherein the method further comprises determining the average value by processing acceleration data measured using the on-board data acquisition system for the arrow for the shot covering the distance. 
     
     
         7 . The method of  claim 3 , further comprising employing a plurality of drag constants based on a non-constant, linear acceleration for the arrow for a shot covering the distance. 
     
     
         8 . The method of  claim 3 , further comprising adjusting a value of the drag constant based on at least one of an ambient temperature at a time of the shot and an altitude at which the shot is taken. 
     
     
         9 . The method of  claim 3 , further comprising adjusting a value of the drag constant based on a diameter of a shaft of the arrow. 
     
     
         10 . The method of  claim 3 , further comprising providing a value of the drag constant based on a model arrow. 
     
     
         11 . A non-transitory computer readable medium encoded with a program for execution on a processor, the program when executed on the processor performing a method of determining an instantaneous speed of an arrow shot from a bow having a bow string, the arrow shot at a target having a target-face, the arrow having a length, the method comprising acts of:
 recording a signal that includes a first peak occurring substantially at a start of a free flight of the arrow and a second peak occurring substantially at a moment of impact of the arrow with the target, the start of the free-flight occurring when a proximate end of the arrow reaches substantially a neutral position of the bow string;   processing the signal to determine a duration of the free flight of the arrow;   determining a distance of the free flight as a distance substantially from the neutral position of the bow string to the target face less the length of the arrow; and   determining the instantaneous speed of the arrow, at least in part, by employing each of the duration of the free flight and the distance of the free flight.   
     
     
         12 . The computer readable medium of  claim 11 , the method further comprising employing a drag constant for the arrow in combination with the duration of the free flight and the distance to determine the instantaneous speed of the arrow. 
     
     
         13 . The computer readable medium of  claim 12 , the method further comprising determining the drag constant based on an average value of acceleration for the arrow for a shot covering the distance. 
     
     
         14 . The computer readable medium of  claim 13 , the method further comprising determining the drag constant based on an estimate of the average value of acceleration for the arrow for the shot covering the distance. 
     
     
         15 . The computer readable medium of  claim 13 , wherein the arrow includes an on-board data acquisition system, and wherein the method further comprises determining the average value by processing acceleration data measured using the on-board data acquisition system for the arrow for the shot covering the distance. 
     
     
         16 . The computer readable medium of  claim 12 , the method further comprising employing a plurality of drag constants based on a non-constant, linear acceleration for the arrow for a shot covering the distance. 
     
     
         17 . The computer readable medium of  claim 12 , the method further comprising adjusting a value of the drag constant based on at least one of an ambient temperature at a time of the shot and an altitude at which the shot is taken. 
     
     
         18 . The computer readable medium of  claim 12 , the method further comprising adjusting a value of the drag constant based on a diameter of a shaft of the arrow. 
     
     
         19 . The computer readable medium of  claim 12 , the method further comprising providing a value of the drag constant based on a model arrow.