Method and system for assessing racket stroke heaviness

Abstract

A method and system for assessing heaviness of a stroke in a racket sport, such as a groundstroke in tennis, is disclosed. The system may display the calculated heaviness of the stroke in real-time. As the player hits strokes, the system will measure linear and rotational speed of the ball and calculate a heaviness value for the stroke based on the physics of translational and rotational kinetic energy of the ball.

1 . A system for assessing a stroke of a racket hitting a ball, the system comprising:
 a sensor device containing one or more sensors capable of detecting parameters of movement of the ball;   a processor; and   a memory containing programming instructions that are configured to, when executed, cause the processor to:
 receive, from the one or more sensors, the detected parameters of movement of the ball as the ball travels through over a court after being hit by the stroke of the racket, 
 use the detected parameters to measure linear speed and rotational speed of the ball, 
 use the measurements of linear speed and rotational speed to generate a heaviness value for the stroke, and 
 output the heaviness value via a display or speaker. 
   
     
     
         2 . The system of  claim 1 , wherein the instructions to generate the heaviness value comprise instructions to:
 identify an interval between a time when the ball contacts a side of an area of the court where the opponent is positioned and a time when the ball contacts a racket of an opponent; and   assess the heaviness value as that associated with the measurements of linear speed and rotational speed that are received for the interval.   
     
     
         3 . The system of  claim 1 , wherein the instructions to generate the heaviness value comprise instructions to determine, based on the detected parameters, a multiple axis rotational amplitude change of the ball as it travels over the court. 
     
     
         4 . The system of  claim 1 , wherein the instructions to use the measurements of linear speed and rotational speed to generate the heaviness value comprise instructions to use a function of a translational kinetic energy value and a rotational kinetic energy value of the ball. 
     
     
         5 . The system of  claim 1 , further comprising instructions to:
 when generating the heaviness value, also using translational kinetic energy of the ball in the function by:
 adjusting a translational kinetic energy value by a first weighting coefficient, 
 adjusting the rotational kinetic energy value by a second weighting coefficient, and 
 summing the adjusted translational kinetic energy value and the adjusted rotational kinetic energy value. 
   
     
     
         6 . The system of  claim 1 , wherein the instructions to generate the heaviness value comprise instructions to, in response to also receiving one or more characteristics of a court from which the sensor device collects data, include the one or more characteristics in the function. 
     
     
         7 . The system of  claim 1 , wherein the instructions to measure linear speed of the ball comprise instructions to, when the one or more sensors comprise a camera:
 measure a distance that the ball has moved in a plurality of subsequent frames captured by the camera; and   use the measured distance and a frame rate of the camera to determine the linear speed of the ball.   
     
     
         8 . The system of  claim 1 , wherein:
 the one or more sensors comprise a camera, a radar system, a lidar system or an audio sensor; and   the one or more sensors are positioned to detect an area of the court that begins on or before a baseline of the court and extends through and beyond a service line of the court.   
     
     
         9 . The system of  claim 1 , wherein the one or more sensors comprise a receiver configured to receive signals transmitted by a sensor that is located in the ball. 
     
     
         10 . The system of  claim 1  further comprising instructions to:
 use detected parameters of movement of an additional ball to generate an additional heaviness value for an additional stroke associated with the additional ball; 
 associate each stroke's heaviness value with a time stamp indicating a time at which the parameters for that stroke were captured; and 
 
       when outputting the heaviness values, use the time stamps of the heaviness values and time stamps of a video showing the strokes to synchronize the heaviness values with the strokes shown in the video. 
     
     
         11 . A method of assessing a stroke of a racket hitting a ball, the method comprising:
 by a sensor device, detecting parameters of movement of a ball on a court;   by a processor:
 receiving, from the one or more sensors, the parameters of movement of the ball, 
 using the detected parameters to measure linear speed and rotational speed of the ball, 
 using the measurements of linear speed and rotational speed to generate a heaviness value for a stroke associated with the movement of the ball, and 
 outputting the heaviness value via a display or speaker. 
   
     
     
         12 . The method of  claim 11 , wherein generating the heaviness value comprises:
 identifying an interval between a time when the ball contacts a side of an area of the court where the opponent is positioned and a time when the ball contacts a racket of an opponent; and   assessing the heaviness value as that associated with the measurements of linear speed and rotational speed that are received for the interval.   
     
     
         13 . The method of  claim 11 , wherein generating the heaviness value comprises determining, based on the detected parameters, a multiple axis rotational amplitude change of the ball as it travels over the court. 
     
     
         14 . The method of  claim 11 , wherein using the measurements of linear speed and rotational speed to generate the heaviness value comprise using a function of a translational kinetic energy value and a rotational kinetic energy value of the ball. 
     
     
         15 . The method of  claim 11 , wherein using the function of translational kinetic energy and rotational kinetic energy of the ball comprises:
 adjusting the translational kinetic energy value by a first weighting coefficient;   adjusting the rotational kinetic energy value by a second weighting coefficient; and   summing the adjusted translational kinetic energy value and the adjusted rotational kinetic energy value.   
     
     
         16 . The method of  claim 11 , wherein generating the heaviness value comprises, in response to also receiving one or more characteristics of a court from which the sensor device collects data, including the one or more characteristics in the function. 
     
     
         17 . The method of  claim 11 , wherein measuring the linear speed of the ball comprises, when the one or more sensors comprise a camera:
 measuring a distance that the ball has moved in a plurality of subsequent frames captured by the camera; and   using the measured distance and a frame rate of the camera to determine the linear speed of the ball.   
     
     
         18 . The method of  claim 11 , wherein:
 the one or more sensors are located in the ball; and   receiving, from the one or more sensors, the parameters of movement of the ball comprises receiving signals transmitted from the ball.   
     
     
         19 . The method of  claim 11  further comprising:
 using detected parameters of movement of an additional ball to generate an additional heaviness value for an additional stroke associated with the movement of the additional ball; 
 associating each stroke's heaviness value with a time stamp indicating a time at which the parameters for that stroke were captured; and 
 when outputting the heaviness values, using the time stamps of the heaviness values and time stamps of a video showing the strokes to synchronize the heaviness values with the strokes shown in the video. 
 
     
     
         20 . A computer program product comprising a computer readable medium containing programming instructions that are configured to cause a processor to:
 receive, from the one or more sensors, parameters of movement of a ball over a court;   use the detected parameters to measure linear speed and rotational speed of the ball;   use the measurements of linear speed and rotational speed to generate a heaviness value for a stroke associated with the movement of the ball; and   output the heaviness value via a display or speaker.