US20130305806A1 - Golf swing measurement system, measurement apparatus, and measurement method - Google Patents
Golf swing measurement system, measurement apparatus, and measurement method Download PDFInfo
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- US20130305806A1 US20130305806A1 US13/839,950 US201313839950A US2013305806A1 US 20130305806 A1 US20130305806 A1 US 20130305806A1 US 201313839950 A US201313839950 A US 201313839950A US 2013305806 A1 US2013305806 A1 US 2013305806A1
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- head
- golf club
- swing
- force
- position information
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- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B60/00—Details or accessories of golf clubs, bats, rackets or the like
- A63B60/46—Measurement devices associated with golf clubs, bats, rackets or the like for measuring physical parameters relating to sporting activity, e.g. baseball bats with impact indicators or bracelets for measuring the golf swing
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/20—Analysis of motion
- G06T7/246—Analysis of motion using feature-based methods, e.g. the tracking of corners or segments
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- A—HUMAN NECESSITIES
- A63—SPORTS; GAMES; AMUSEMENTS
- A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
- A63B53/00—Golf clubs
- A63B53/08—Golf clubs with special arrangements for obtaining a variable impact
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/10—Image acquisition modality
- G06T2207/10016—Video; Image sequence
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/30—Subject of image; Context of image processing
- G06T2207/30204—Marker
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/30—Subject of image; Context of image processing
- G06T2207/30221—Sports video; Sports image
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/30—Subject of image; Context of image processing
- G06T2207/30241—Trajectory
Definitions
- the present invention relates to a golf swing measurement system, measurement apparatus, and measurement method.
- the shaft of the golf club experiences deformations such as flex and torsion, and the head rotates. Deformation of the golf club shaft and rotation of the head are considered to exert an extremely large influence over whether a golfer can execute an ideal golf swing.
- the forces acting on the golf club that lead to deformation of the golf club shaft and rotation of the head are mainly caused by forces exerted by the subject, such as a golfer, acting on the golf club.
- the exertion of such forces acts on the head through the shaft, generating an inertial force, a centrifugal force, and the like at the head and possibly causing the head to rotate.
- the inertial force and the centrifugal force may end up deforming the shaft.
- the torsion may affect the rotation behavior of the head. In this way, the inertial force and the centrifugal force acting on the head during the golf swing cause the shaft to deform and also affect the rotation behavior of the head.
- Patent Literature 1 When analyzing a golfer's swing, it is therefore crucial to calculate the centrifugal force and inertial force acting on the head of the golf club during the swing.
- an apparatus has thus been proposed to detect at least one of velocity, acceleration, inertial force, and centrifugal force with a detection unit attached to the golfer or to the golf club (for example, see Patent Literature 1).
- a detection unit attached to the golfer or to the golf club
- Patent Literature 1 According to the apparatus in Patent Literature 1, it is possible to detect and measure changes in the velocity during the golf swing as well as acceleration, inertial force, centrifugal force, and the like obtained as a function of velocity by using, for example, a velocity sensor, a force resistive sensor, a pressure sensor, a gravimetric sensor, or the like.
- a method has also conventionally been proposed for attaching a body having an inertial sensor, constituted by at least one of a gyroscope and an accelerometer, to a measurement subject and calculating the swing velocity of the measurement subject based on a signal from the inertial sensor (for example, see Patent Literature 2).
- the swing velocity can be measured to a high degree of accuracy, thereby improving reliability.
- non-contact measurement methods such as image measurement
- a behavior measurement apparatus for measuring the behavior of a golf club head has been proposed.
- This behavior measurement apparatus measures the behavior of the head based on an image pickup apparatus that captures images of a plurality of markers attached to the golf club, position information on the captured markers, and a 3D geometric model of the head (for example, see Patent Literature 3).
- Such a behavior measurement apparatus can perform highly accurate measurement of the behavior of the head.
- the behavior measurement apparatus can reportedly make accurate measurements of the position and orientation of the striking face immediately before the golf ball is hit.
- a golf swing measurement system has also been proposed for measuring golf swing behavior by attaching a shaft axis mark and shaft rotation mark to the golf club, attaching wrist marks, elbow marks and shoulder marks to the golfer, and using a computer to recognize the position coordinates of each mark based on captured images (for example, see Patent Literature 4).
- this sort of golf swing measurement system it is reportedly possible to perform an accurate and detailed analysis of behavior of the wrist joints and elbow joints, which have two rotational degrees of freedom, during a swing.
- the present invention has been conceived in light of the above-described circumstances, and it is an object thereof to provide a golf swing measurement system, measurement apparatus, and measurement method that can measure the forces acting on the head during a swing as usual by a golfer.
- a golf swing measurement system for achieving the above object is a system for measuring force acting on a head of a golf club during a swing, comprising: at least two image pickup apparatuses each configured to capture an image of the golf club, the golf club including at least one head identifier attached to the head for specification of a position on the head; and a measurement apparatus configured to measure the force acting on the head of the golf club based on position information of the at least one head identifier, the position information being acquired from the images of the golf club captured by the image pickup apparatuses during the swing.
- the system according to an aspect of the present invention can measure the force acting on the head during a swing as usual by a golfer.
- the measurement apparatus preferably comprises an image acquisition unit configured to acquire the images of the golf club during the swing from the image pickup apparatuses; a position information acquisition unit configured to recognize the at least one head identifier in the acquired images and to acquire position information of the recognized at least one head identifier; and a measurement unit configured to measure, as the force acting on the head of the golf club, a centrifugal force and an inertial force acting on the head of the golf club based on the acquired position information.
- the centrifugal force is an apparent force that acts outwards, from the center of rotation, on the head of the golf club during the swing
- the inertial force is an apparent force corresponding to the acceleration acting on the head of the golf club during the swing.
- the measurement unit preferably measures the centrifugal force and the inertial force as the force acting on the head of the golf club by resolving the centrifugal force and the inertial force into components in a striking direction of the swing and a toe down direction.
- the direction perpendicular to the face surface is referred to as the striking direction.
- Toe down typically refers to the change in position of the head in the shaft axis direction occurring during a swing.
- the toe down direction refers to a direction along the line of intersection of the face surface and a surface that passes through the center of gravity of the head and is orthogonal to the shaft axis.
- the at least one head identifier is positioned for specification of an orientation and a center of gravity of the head
- the image pickup apparatuses capture the images of the golf club, the golf club including the at least one head identifier and at least one shaft axis identifier positioned for specification of a shaft axis of the golf club
- the position information acquisition unit acquires position information of the at least one head identifier and the at least one shaft axis identifier from the images
- the measurement unit measures the centrifugal force and the inertial force as the force acting on the head of the golf club by resolving the centrifugal force and the inertial force into the components in the striking direction of the swing and the toe down direction based on the position information of the at least one head identifier and the at least one shaft axis identifier.
- the measurement unit preferably further measures, as the force acting on the golf club, torque acting on a shaft of the golf club based on the centrifugal force and the inertial force.
- torque refers to the force applied in the torsion direction.
- a measurement apparatus for achieving the above object is an apparatus for measuring force acting on a head of a golf club during a swing, wherein the apparatus measures the force acting on the head of the golf club based on position information of at least one head identifier attached to the head for specification of a position on the head, the position information being acquired from an image of the golf club captured during the swing.
- the apparatus according to an aspect of the present invention can measure the force acting on the head during a swing as usual by a golfer.
- a golf swing measurement method for achieving the above object is a method for measuring force acting on a head of a golf club during a swing, comprising the steps of: attaching at least one head identifier to the head for specification of a position on the head; capturing an image of the golf club including the at least one head identifier; acquiring position information of the at least one head identifier from the image of the golf club captured during the swing; and determining the force acting on the head of the golf club based on the position information.
- the method according to an aspect of the present invention can measure the force acting on the head during a swing as usual by a golfer.
- FIG. 1 is a schematic view of a golf swing measurement system according to an embodiment of the present invention
- FIG. 2 is a functional block diagram schematically illustrating the structure of a golf swing measurement apparatus according to the embodiment of the present invention
- FIG. 3 is a flowchart illustrating an example of the golf swing measurement method according to the embodiment of the present invention.
- FIG. 4 illustrates an example of a golf club used in the golf swing measurement system according to the embodiment of the present invention
- FIG. 5 is a diagram illustrating an example of a centrifugal force decomposition method when measuring a swing using the golf club illustrated in FIG. 4 ;
- FIG. 6 is another diagram illustrating an example of the centrifugal force decomposition method when measuring a swing using the golf club illustrated in FIG. 4 ;
- FIG. 7 is a diagram illustrating an example of an inertial force decomposition method when measuring a swing using the golf club illustrated in FIG. 4 ;
- FIG. 8 is another diagram illustrating an example of the inertial force decomposition method when measuring a swing using the golf club illustrated in FIG. 4 ;
- FIG. 9A is a diagram illustrating an example of inertial force decomposition immediately after the start of a downswing when measuring a swing using the golf club illustrated in FIG. 4 ;
- FIG. 9B is a diagram illustrating an example of inertial force decomposition in the middle of the downswing when measuring a swing using the golf club illustrated in FIG. 4 ;
- FIG. 9C is a diagram illustrating an example of inertial force decomposition immediately before impact when measuring a swing using the golf club illustrated in FIG. 4 ;
- FIG. 10 is a diagram illustrating an example of a decomposition method for resolving a centrifugal force into a component in a torsion direction when measuring a swing using the golf club illustrated in FIG. 4 ;
- FIG. 11 is another diagram illustrating an example of a decomposition method for resolving a centrifugal force into a component in the torsion direction when measuring a swing using the golf club illustrated in FIG. 4 ;
- FIG. 12 is a diagram illustrating an example of a method of calculating torque derived from an inertial force when measuring a swing using the golf club illustrated in FIG. 4 ;
- FIG. 13A illustrates the results of measuring forces derived from an inertial force and a centrifugal force in a striking direction when a robot executes a swing
- FIG. 13B illustrates the results of measuring forces derived from an inertial force and a centrifugal force in a toe down direction when a robot executes a swing
- FIG. 14A illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the striking direction illustrated in FIG. 13A and a flex amount of the shaft;
- FIG. 14B illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the toe down direction illustrated in FIG. 13B and the flex amount of the shaft;
- FIG. 15A illustrates the results of measuring forces derived from an inertial force and a centrifugal force in the striking direction when a human executes a swing
- FIG. 15B illustrates the results of measuring forces derived from an inertial force and a centrifugal force in the toe down direction when a human executes a swing
- FIG. 16A illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the striking direction illustrated in FIG. 15A and the flex amount of the shaft;
- FIG. 16B illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the toe down direction illustrated in FIG. 15B and the flex amount of the shaft;
- FIG. 17A illustrates the results of measuring torque derived from an inertial force and a centrifugal force on the shaft when a robot executes a swing
- FIG. 17B illustrates the results of measuring torque derived from an inertial force and a centrifugal force on the shaft when a human executes a swing
- FIG. 18A illustrates the relationship between the sum of torque derived from the inertial force and from the centrifugal force illustrated in FIG. 17A and a torsion angle of the shaft calculated based on markers;
- FIG. 18B illustrates the relationship between the sum of torque derived from the inertial force and from the centrifugal force illustrated in FIG. 17B and the torsion angle of the shaft calculated based on markers;
- FIG. 19 illustrates an example of a golf club used for measurement of torsion acting on the golf club during a swing.
- FIG. 1 is a schematic view of the golf swing measurement system according to the embodiment of the present invention.
- a golf swing measurement system 1 illustrated in FIG. 1 is a measurement system for measuring forces acting on the head on a golf club 5 when a golfer 4 swings the golf club 5 .
- the measurement system 1 is provided with a first camera 2 A and a second camera 2 B, constituting at least two image pickup apparatuses, and a measurement apparatus 3 that measures forces acting on the head based on images of the golf club captured during the swing.
- the first camera 2 A and the second camera 2 B capture images of a marker 6 (head identifier), which constitutes at least one identifier attached to the head for specification of a position on the head.
- the marker 6 is made from a material that can be distinguished from its surroundings in a captured image of the golf club 5 .
- the marker 6 is reflective tape or paint.
- the marker 6 is, for example, preferably positioned on the head near the base of the shaft. This makes it possible to acquire position information on the head during a swing with little effect from the flex and torsion of the golf club.
- the first camera 2 A and the second camera 2 B are, for example, high-speed video cameras capable of highly-sensitive filming of video with abundant movement.
- the frame rate when the first camera 2 A and the second camera 2 B film the swing is, for example, 160 Hz.
- the measurement apparatus 3 measures the forces acting on the head of the golf club 5 based on the position information of the marker 6 acquired from the images of the golf club 5 captured by the first camera 2 A and the second camera 2 B during the swing by the golfer 4 .
- the measurement apparatus 3 is constituted by a computer provided, for example, with a Central Processing Unit (CPU) or a Digital Signal Processor (DSP).
- CPU Central Processing Unit
- DSP Digital Signal Processor
- FIG. 2 is a functional block diagram schematically illustrating the structure of the measurement apparatus 3 .
- the measurement apparatus 3 is provided with image acquisition units 7 A and 7 B that acquire images, a calculation unit 10 constituted by, for example, a CPU or a DSP, a control unit 11 that controls each functional unit provided in the measurement apparatus 3 , a display unit 12 that displays measurement results, and a database 13 that stores data such as measurement results and golf club specifications.
- the image acquisition units 7 A and 7 B are, for example, each constituted by an interface (I/F).
- the calculation unit 10 is provided with a position information acquisition unit 8 that acquires position information and a measurement unit 9 that measures forces acting on the head of the golf club 5 .
- An overview of operations by each functional unit will be provided below with reference to the flowchart for the golf swing measurement method according to the embodiment of the present invention shown in FIG. 3 .
- FIG. 3 is a flowchart illustrating an example of the golf swing measurement method according to the embodiment of the present invention.
- the golfer 4 in FIG. 1 executes a swing with the golf club 5 .
- the first camera 2 A and the second camera 2 B constituting at least two image pickup apparatuses capture images, during a swing, of the marker 6 attached to the head (step S 01 ).
- the measurement apparatus 3 acquires image data for the marker 6 during the swing from the first camera 2 A and the second camera 2 B (step S 02 ).
- the image data for the marker 6 may be video data of any format captured by the first camera 2 A and the second camera 2 B.
- the measurement apparatus 3 Via the position information acquisition unit 8 , the measurement apparatus 3 extracts any image data from the image data captured by the first camera 2 A and the second camera 2 B in step S 02 , recognizes the marker in the extracted image data, and acquires position information on the recognized marker (step S 03 ).
- the position information acquisition unit 8 recognizes the marker attached to the golf club 5 by, for example, a circle fitting method applied, for example, to any number of frames extracted from the video data acquired from the first camera 2 A and the second camera 2 B.
- a circle fitting method is a method to extract the outline of a circular marker (a sphere in 3D space), establish a circle approximating the extracted outline, and calculate the virtual center point of the marker.
- the position information acquisition unit 8 acquires 3D coordinates with a general method, such as a triangulation method.
- the position information acquisition unit 8 can store information on the acquired 3D coordinates in association with the golfer who executed the swing in the database 13 .
- the measurement apparatus 3 determines forces acting on the head of the golf club 5 based on the position information acquired in step S 03 (step S 04 ).
- the measurement apparatus 3 can then display measurement results, as in the examples in FIGS. 14A through 18B , on the display unit 12 .
- the measurement unit 9 preferably measures the centrifugal force acting on the head based on the position information of the marker 6 .
- the measurement unit 9 can approximate a virtual rotation center and virtual circle for the head during a swing based on the position information of the marker 6 at any time t n and times before and after t n , i.e. t n ⁇ 1 and t n+1 .
- the virtual circle can be calculated as, for example, the trajectory traversed by the position of the center of gravity of the head.
- the centrifugal force F c acting on the head can be calculated based on the following equation, using the radius r of the virtual circle, as well as the mass m and velocity v, calculated from the position information at times t n , t n ⁇ 1 and t n+1 , of the head of the golf club 5 .
- the centrifugal force F c is an apparent force that acts outwards, from the center of rotation, on the head of the golf club during the swing.
- the measurement unit 9 preferably calculates the inertial force F i corresponding to acceleration obtained by differentiating the absolute value of the above velocity v. Letting the derivative of the absolute value of the velocity of the head of the golf club 5 be a and the mass of the head be m, the inertial force F i is calculated with the following equation.
- the inertial force F i referred to in the present description is an apparent force corresponding to the acceleration acting on the head at each point in time.
- the golf swing measurement system 1 can measure the forces acting on the head during a golf swing as usual by a golfer. Furthermore, as the forces acting on the head of the golf club, the golf swing measurement system according to the present embodiment can measure the centrifugal force and the inertial force acting on the head. Moreover, performing measurements without use of an acceleration sensor eliminates the effect of the mass of the acceleration sensor on the measurement value, thereby offering the advantage of not requiring calculation to adjust for the effect of the mass of the acceleration sensor.
- the forces acting in the striking direction of the swing and the toe down direction greatly affect the direction and distance traveled by the golf ball, the travel velocity, and the like. Therefore, as indices for assessing the swing, it is also extremely important to assess forces acting in the striking direction of the swing and the toe down direction. Furthermore, toe down of the head when the golf club is swung has been considered to be caused by centrifugal force generated during the swing, but the causal relationship has not been made clear.
- the striking direction of the swing refers to the direction in which the ball is struck by the swing and is determined by the orientation of the face surface of the head at the time of impact. Therefore, in the present description, the direction perpendicular to the face surface is referred to as the striking direction.
- Toe down typically refers to the change in position of the head in the shaft axis direction occurring during a swing.
- the toe down direction refers to a direction along the line of intersection of the face surface and a surface that passes through the center of gravity of the head and is orthogonal to the shaft axis.
- the golf swing measurement system 1 preferably measures the centrifugal force F c and the inertial force F i as the forces acting on the head of the golf club by resolving these forces into components in the striking direction of the swing and the toe down direction.
- the method for resolving the forces acting on the head of the golf club into the components in the striking direction of the swing and the toe down direction will be described with reference to FIGS. 4 through 8 .
- FIG. 4 illustrates an example of a golf club used in the golf swing measurement system according to the present embodiment.
- a golf club 18 has a grip 14 , a shaft 15 , and a head 16 .
- the golf club 18 preferably has shaft axis markers M 1 and M 2 (shaft axis identifiers) positioned to allow for specification of the axis of the shaft 15 and head markers M 3 and M 4 (head identifiers) positioned to allow for specification of the orientation and the center of gravity of the head.
- the shaft axis markers M 1 and M 2 are positioned to allow for specification of the axis of the shaft 15 .
- the shaft axis markers M 1 and M 2 are positioned with their center along the shaft axis.
- the shaft 15 flexes during a swing, but since the shaft axis markers M 1 and M 2 are positioned near the grip 14 , which flexes relatively less, the shaft axis calculated based on the shaft axis markers M 1 and M 2 corresponds to the axis of the shaft 15 when the shaft 15 does not flex at all during a swing.
- the head markers M 3 and M 4 are preferably positioned on the head 16 in a configuration such that information on the orientation of the face surface of the head 16 and on the position of the center of gravity of the head 16 can be obtained. Accordingly, the configuration of the head markers is not limited to the configuration shown in the drawings. For example, it is of course possible to use only one head marker in the shape of a line parallel to the face surface.
- the measurement system 1 obtains information on the position of the center of gravity during a swing by acquiring information on the position of the center of gravity of the head 16 from the golf club specifications and determining the distance to the head markers M 3 and M 4 and the axis of the shaft 15 as well as the relative positions thereof with respect to the center of gravity.
- trajectory traversed by the position of the center of gravity has been assumed to be a virtual circle, it is of course possible to adopt a simpler method that calculates the forces acting on the head 16 by calculating the trajectory traversed by the head marker as the virtual circle.
- FIG. 5 is a diagram illustrating an example of a centrifugal force decomposition method when measuring a swing using the golf club illustrated in FIG. 4 , the swing being viewed from the front.
- the centrifugal force F c is an apparent force that acts outwards, from the above-described virtual rotation center RC, on the center of gravity G of the head 16 .
- the measurement unit 9 In order to resolve the centrifugal force F c in the striking direction of the swing and the toe down direction, the measurement unit 9 first resolves the centrifugal force F c into a force F 1 in a direction perpendicular to the shaft axis 15 A. This decomposition is performed, for example, with the following equation.
- the angle ⁇ 1 is the angle between the shaft axis 15 A and a line connecting the virtual rotation center RC with the center of gravity G of the head 16 .
- FIG. 6 is a top view illustrating an example of a centrifugal force decomposition method when measuring a swing using the golf club illustrated in FIG. 4 .
- a line parallel to the face surface of the head 16 connecting the head markers M 3 and M 4 is labeled FL
- a line parallel to the line FL and traversing the center of gravity G is labeled FL p .
- the head markers M 3 and M 4 and the shaft 15 are illustrated with their respective centers aligned with the face surface of the head 16 .
- the force F 1 calculated as described above is a force in the normal direction from the center of gravity G towards the shaft axis 15 A, as illustrated in FIG. 6 .
- the force F 1 is resolved by the following equation into a striking direction centrifugal force F cf and a toe down direction centrifugal force F ct centered on the center of gravity G.
- the center of gravity angle ⁇ G is the angle between the face surface of the head and a line connecting the position of the center of gravity with the center of the position of attachment of the shaft 15 .
- the center of gravity angle ⁇ G may also be acquired from the specifications for the golf club 18 or the like.
- the center of gravity angle ⁇ G can be derived from calculating the angle between a line parallel to the face surface of the head acquired from the head markers M 3 and M 4 and the line connecting the position of the center of gravity with the center of the position of attachment of the shaft 15 . In this way, the golf swing measurement system 1 according to the present embodiment can calculate the striking direction centrifugal force and the toe down direction centrifugal force acting on the golf club 18 during a swing.
- FIGS. 7 and 8 are diagrams illustrating an example of a decomposition method for an inertial force F i when measuring a swing using the golf club illustrated in FIG. 4 .
- the angle ⁇ 2 is the angle between a line 15 P parallel to the shaft axis 15 A and a tangent a to the virtual circle 19 , which approximates the trajectory of the center of gravity G during the swing.
- the measurement unit 9 in FIG. 2 differentiates the absolute value of the velocity during the swing to calculate the magnitude of the acceleration a in a direction matching the tangent to the virtual circle 19 .
- FIG. 7 illustrates the inertial force F i , which is an apparent force that acts in the opposite direction of the acceleration a.
- the measurement unit 9 measures a force F 2 that traverses the center of gravity G in a direction perpendicular to the shaft axis 15 A.
- the measurement unit 9 resolves the force F 2 into a toe down direction inertial force F it and a striking direction inertial force F if centered on the center of gravity G using the equations below.
- the angle ⁇ is the angle between the face surface of the head and the inertial force vector.
- FL a line parallel to the face surface of the head 16 connecting the head markers M 3 and M 4
- FL p a line parallel to the line FL and traversing the center of gravity G
- the golf swing measurement system can resolve, in the striking direction and in the toe down direction, the inertial force acting on the head 16 of the golf club 5 during a swing.
- the measurement system 1 can provide indices for a more detailed analysis of the swing.
- An example of resolving the inertial force at three points in time during a golf swing will now be described with reference to FIGS. 9A through 9C .
- the three points in time during the golf swing are (1) immediately after the start of the downswing, in which the golfer 4 swings the golf club 5 down; (2) the middle of the downswing; and (3) immediately before impact of the head 16 with the golf ball.
- the face of the head 16 is open and is facing ahead of the golfer 4 .
- the face is closed and is slanted with respect to the front of the golfer 4 .
- the face is closed and is facing sideways with respect to the front of the golfer 4 .
- FIG. 9A is a top view illustrating an example of inertial force decomposition immediately after the start of a downswing. Immediately after the start of the downswing, the face surface of the head 16 is open towards the front of the golfer 4 . Since the golfer 4 swings the golf club 5 down with the head 16 in this state, the head 16 moves in the direction of the shaft axis 15 A.
- the acceleration ah acts from the center of gravity G towards the left in the figure, and the inertial force F i is a force in the opposite direction.
- the measurement unit 9 resolves the force F 2 into a toe down direction inertial force F it and a striking direction inertial force F if centered on the center of gravity G.
- FIG. 9B is a diagram illustrating an example of inertial force decomposition in the middle of the downswing.
- the face surface of the head 16 gradually closes in the middle of the downswing so as to be slanted with respect to the front of the golfer 4 . Therefore, the acceleration ah acts in the direction shown in the figure, and the inertial force F i is a force in the opposite direction.
- the measurement unit 9 resolves the force F 2 into a toe down direction inertial force F it and a striking direction inertial force F if centered on the center of gravity G.
- FIG. 9C is a diagram illustrating an example of inertial force decomposition immediately before impact.
- the face surface of the head 16 is closed immediately before impact and faces sideways with respect to the front of the golfer 4 . Therefore, the acceleration ah acts in the direction shown in the figure, and the inertial force F i is a force in the opposite direction.
- the measurement unit 9 resolves the force F 2 into a toe down direction inertial force F it and a striking direction inertial force F if centered on the center of gravity G.
- the golf swing measurement system 1 can resolve, in the striking direction and the toe down direction, the centrifugal force and the inertial force acting on the golf club during a swing. In this way, among the forces acting on the head of the golf club, the force contributing in the striking direction and the force contributing in the toe down direction are calculated, thus permitting a more detailed analysis of the swing.
- the golf swing measurement system 1 preferably also measures the torque contributing to torsion of the shaft as a force acting on the golf club by measuring the torque from each of the centrifugal force and the inertial force acting on the golf club during the swing. This measurement will be described with reference to FIGS. 10 through 12 .
- FIG. 10 is a diagram illustrating an example of a decomposition method for resolving a centrifugal force into a component in a torsion direction when measuring a swing using the golf club illustrated in FIG. 4 .
- the torsion direction refers to the direction in which the head rotates around the shaft axis of the golf club and is a rotational direction either forwards or backwards with respect to the direction of travel.
- the force applied in the torsion direction is referred to as torque.
- FIG. 10 is a front view of the golf club 5 .
- a line parallel to the shaft axis 15 A and traversing the center of gravity G of the head 16 is labeled 15 P.
- the centrifugal force F c acting on the head 16 during the swing acts on the center of gravity G of the head 16 in a direction away from the above-described virtual rotation center RC. Therefore, in order first to calculate the centrifugal force in the torsion direction, the measurement unit 9 needs to calculate a component F cg of the centrifugal force F c along the line 15 P by the following equation, using the angle ⁇ 1 between the shaft axis 15 A of the shaft 15 of the golf club 18 and a line connecting the virtual rotation center RC with the center of gravity G of the head 16 .
- the measurement unit 9 uses the component F cg of the centrifugal force F c along the line 15 P as well as an angle ⁇ SG , which is the angle between the shaft axis 15 A and a line connecting the position at which the shaft axis 15 A meets the head 16 (referred to below as the “contact point”) with the center of gravity G of the head 16 , to calculate a force F cgf using the following equation.
- the force F cgf is a force acting on the center of gravity G with the contact point as a point of support and is a decomposition, from the component F cg of the centrifugal force F c , of a force in a direction approximately perpendicular to the face of the head 16 .
- sin ⁇ SG and cos ⁇ SG can be derived from the value of tan ⁇ SG .
- the value of tan ⁇ SG can be calculated by the following equation based on the face height ⁇ , the center of gravity height ⁇ , and the center of gravity depth ⁇ .
- the face height ⁇ refers to the height from the bottom of the golf club to the upper edge of the face.
- the center of gravity height ⁇ refers to the height from the bottom of the golf club to the center of gravity in the direction of the shaft axis 15 A.
- the center of gravity depth y refers to the distance from the center of gravity of the golf club to the face surface in a direction perpendicular to the shaft axis 15 A. Note that the face height ⁇ , center of gravity height ⁇ , and center of gravity depth ⁇ for a variety of golf club heads can be obtained from the specifications for the golf clubs.
- the measurement unit 9 calculates a torsion direction centrifugal force F ctr by the following equation, using the above-described force F cgf and the center of gravity angle ⁇ G between the face surface of the head and a line connecting the position of the center of gravity with the center of the position of attachment of the shaft 15 .
- the torsion direction centrifugal force F ctr is a centrifugal force in the torsion direction derived from the centrifugal force acting on the center of gravity G during the swing.
- the measurement unit 9 calculates the torque T c around the shaft axis 15 A derived from the centrifugal force by multiplying the torsion direction centrifugal force F ctr by the center of gravity distance L.
- center of gravity distance L refers to the distance from the center of gravity G of the head 16 to the shaft axis 15 A and can be obtained from the specifications for the golf club.
- FIG. 12 is a diagram illustrating an example of a method of calculating the torque T i derived from an inertial force.
- the measurement unit 9 uses the center of gravity angle ⁇ G and an angle ⁇ FL between a tangent to the trajectory of the head 16 and the line FL parallel to the face surface to calculate a torsion direction inertial force F itc, around the shaft axis 15 A, that forms a 90° angle with respect to a line connecting the center of gravity G and the shaft axis 15 A and that acts backward with respect to the direction of travel of the head 16 .
- the measurement unit 9 calculates the torque T i around the shaft axis 15 A derived from the inertial force by multiplying the torsion direction inertial force F itr by the center of gravity distance L.
- center of gravity distance L refers to the distance from the center of gravity G of the head 16 to the shaft axis 15 A and can be obtained from the specifications for the golf club.
- the golf swing measurement system 1 can calculate the torque derived from the centrifugal force F c and from the inertial force F i . It is considered that the torque T c derived from the centrifugal force causes torsion in the direction of travel, whereas the torque T i derived from the inertial force causes torsion in the direction opposite the direction of travel. Accordingly, taking sign into consideration, it is thought that if the sum of the torque (T c +T i ) is a positive value, the shaft 15 of the golf club 18 is twisted in the direction of travel. Conversely, if the sum of the torque (T c +T i ) is a negative value, torsion occurs in the direction opposite the direction of travel. Accordingly, by summing the calculated values of torque, the golf swing measurement system 1 can analyze the torsion acting on the shaft 15 of the golf club 18 in greater detail.
- FIGS. 13A through 16B Measurement results by the golf swing measurement system 1 according to the present embodiment will now be described with reference to FIGS. 13A through 16B .
- measurement was performed for a swing using a golf club having an additional marker on the head 16 near the base of the shaft 15 of the golf club 18 illustrated in FIG. 4 .
- FIG. 13A illustrates the results of measuring forces derived from an inertial force and a centrifugal force in the striking direction when a robot executes a swing.
- FIG. 13B illustrates the results of measuring forces derived from an inertial force and a centrifugal force in the toe down direction when a robot executes a swing.
- the vertical axis represents the magnitude of the force (N), and the horizontal axis represents time (s). Time 0 is the time of impact.
- FIG. 14A illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the striking direction illustrated in FIG. 13A and the flex amount of the shaft 15 .
- FIG. 14B illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the toe down direction illustrated in FIG. 13B and the flex amount of the shaft 15 .
- the flex amount of the shaft 15 can be calculated as the distance between the above-described additional marker near the base of the shaft 15 and the shaft axis determined by the shaft axis markers M 1 and M 2 illustrated in FIG. 4 . As clearly shown in FIGS.
- the golf swing measurement system 1 can quantitatively measure the change over time in the magnitude of the applied force with respect to the flex of the shaft during a swing.
- FIG. 15A illustrates the results of measuring forces derived from an inertial force and a centrifugal force in the striking direction when a human executes a swing.
- FIG. 15B illustrates the results of measuring forces derived from an inertial force and a centrifugal force in the toe down direction when a human executes a swing.
- FIG. 16A illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the striking direction illustrated in FIG. 15A and the flex amount of the shaft.
- FIG. 16B illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the toe down direction illustrated in FIG. 15B and the flex amount of the shaft.
- the flex amount of the shaft and the sum of the centrifugal force and the inertial force exhibit a similar tendency of change over time.
- FIGS. 17A through 18B Another example of measurement results by the golf swing measurement system 1 according to the present embodiment will now be described with reference to FIGS. 17A through 18B .
- measurement was performed for a swing using a golf club 18 A illustrated in FIG. 19 .
- the golf club 18 A is the golf club 18 illustrated in FIG. 4 with a marker M 5 on a mounting 20 at the upper portion of the shaft 15 .
- the torsion acting on the golf club during a swing was calculated based on the relative positions of the head markers M 3 and M 4 on the head 16 and the marker M 5 .
- FIG. 17A illustrates the results of measuring torque derived from an inertial force and a centrifugal force on the shaft 15 when a robot executes a swing.
- FIG. 17B illustrates the results of measuring torque derived from an inertial force and a centrifugal force on the shaft 15 when a human executes a swing.
- the torque derived from each of the centrifugal force and the inertial force on the shaft 15 was measured, and the sum of the values of the torque was calculated.
- FIGS. 18A and 18B illustrate the relationship between the sum of torque derived from the inertial force and from the centrifugal force illustrated in FIGS. 17A and 17B and the torsion angle of the shaft calculated based on the above-described markers. As shown by FIGS. 18A and 18B , the sum of the calculated torque values and the torsion angle of the golf club exhibit a similar tendency of change.
Abstract
The system (1) for measuring a golf swing according to the present invention is provided with at least two image pickup apparatuses that each capture an image of a golf club (5) that includes at least one head identifier attached to the head and with a measurement apparatus that measures the force acting on the head of the golf club (5) based on position information of the at least one head identifier, the position information being acquired from the images of the golf club (5) captured during a swing.
Description
- This application is based on an application No. 2012-115796 filed in Japan on May 21, 2012, the entire contents of which are hereby incorporated by reference.
- The present invention relates to a golf swing measurement system, measurement apparatus, and measurement method.
- During development of golf clubs, golf swings by different types of golfers have been measured and collected as data. Measuring golf swings by different types of golfers supports the development of golf clubs suitable for different types of golfers as well as the selection of a suitable golf club for each type of golfer.
- In accordance with the forces acting on the golf club during a golfer's swing, the shaft of the golf club experiences deformations such as flex and torsion, and the head rotates. Deformation of the golf club shaft and rotation of the head are considered to exert an extremely large influence over whether a golfer can execute an ideal golf swing.
- The forces acting on the golf club that lead to deformation of the golf club shaft and rotation of the head are mainly caused by forces exerted by the subject, such as a golfer, acting on the golf club. During the golf swing, the exertion of such forces acts on the head through the shaft, generating an inertial force, a centrifugal force, and the like at the head and possibly causing the head to rotate. Furthermore, the inertial force and the centrifugal force may end up deforming the shaft. When the shaft deforms due to torsion, the torsion may affect the rotation behavior of the head. In this way, the inertial force and the centrifugal force acting on the head during the golf swing cause the shaft to deform and also affect the rotation behavior of the head.
- When analyzing a golfer's swing, it is therefore crucial to calculate the centrifugal force and inertial force acting on the head of the golf club during the swing. Conventionally, an apparatus has thus been proposed to detect at least one of velocity, acceleration, inertial force, and centrifugal force with a detection unit attached to the golfer or to the golf club (for example, see Patent Literature 1). According to the apparatus in
Patent Literature 1, it is possible to detect and measure changes in the velocity during the golf swing as well as acceleration, inertial force, centrifugal force, and the like obtained as a function of velocity by using, for example, a velocity sensor, a force resistive sensor, a pressure sensor, a gravimetric sensor, or the like. - A method has also conventionally been proposed for attaching a body having an inertial sensor, constituted by at least one of a gyroscope and an accelerometer, to a measurement subject and calculating the swing velocity of the measurement subject based on a signal from the inertial sensor (for example, see Patent Literature 2). According to this method, the swing velocity can be measured to a high degree of accuracy, thereby improving reliability.
- On the other hand, in recent years, non-contact measurement methods, such as image measurement, have been proposed as methods for measuring and analyzing a golf swing. For example, a behavior measurement apparatus for measuring the behavior of a golf club head has been proposed. This behavior measurement apparatus measures the behavior of the head based on an image pickup apparatus that captures images of a plurality of markers attached to the golf club, position information on the captured markers, and a 3D geometric model of the head (for example, see Patent Literature 3). Such a behavior measurement apparatus can perform highly accurate measurement of the behavior of the head. Specifically, the behavior measurement apparatus can reportedly make accurate measurements of the position and orientation of the striking face immediately before the golf ball is hit.
- A golf swing measurement system has also been proposed for measuring golf swing behavior by attaching a shaft axis mark and shaft rotation mark to the golf club, attaching wrist marks, elbow marks and shoulder marks to the golfer, and using a computer to recognize the position coordinates of each mark based on captured images (for example, see Patent Literature 4). According to this sort of golf swing measurement system, it is reportedly possible to perform an accurate and detailed analysis of behavior of the wrist joints and elbow joints, which have two rotational degrees of freedom, during a swing.
- PTL 1: JP7178210A
- PTL 2: JP2011072518A
- PTL 3: JP2009294048A
- PTL 4: JP2005218783A
- With the methods and techniques disclosed in
Patent Literature Patent Literature - The present invention has been conceived in light of the above-described circumstances, and it is an object thereof to provide a golf swing measurement system, measurement apparatus, and measurement method that can measure the forces acting on the head during a swing as usual by a golfer.
- A golf swing measurement system according to an aspect of the present invention for achieving the above object is a system for measuring force acting on a head of a golf club during a swing, comprising: at least two image pickup apparatuses each configured to capture an image of the golf club, the golf club including at least one head identifier attached to the head for specification of a position on the head; and a measurement apparatus configured to measure the force acting on the head of the golf club based on position information of the at least one head identifier, the position information being acquired from the images of the golf club captured by the image pickup apparatuses during the swing.
- The system according to an aspect of the present invention can measure the force acting on the head during a swing as usual by a golfer.
- In the system according to an aspect of the present invention, the measurement apparatus preferably comprises an image acquisition unit configured to acquire the images of the golf club during the swing from the image pickup apparatuses; a position information acquisition unit configured to recognize the at least one head identifier in the acquired images and to acquire position information of the recognized at least one head identifier; and a measurement unit configured to measure, as the force acting on the head of the golf club, a centrifugal force and an inertial force acting on the head of the golf club based on the acquired position information.
- According to this structure, it is possible easily to measure the centrifugal force and the inertial force acting on the head during a swing as usual by a golfer. In the present description, the centrifugal force is an apparent force that acts outwards, from the center of rotation, on the head of the golf club during the swing, and the inertial force is an apparent force corresponding to the acceleration acting on the head of the golf club during the swing.
- In the system according to an aspect of the present invention, the measurement unit preferably measures the centrifugal force and the inertial force as the force acting on the head of the golf club by resolving the centrifugal force and the inertial force into components in a striking direction of the swing and a toe down direction.
- According to this structure, it is possible to provide indices for a more detailed analysis of the swing by more accurately measuring the forces acting on the head during the swing in the striking direction and the toe down direction. In the present description, the direction perpendicular to the face surface is referred to as the striking direction. Toe down typically refers to the change in position of the head in the shaft axis direction occurring during a swing. In the present description, however, the toe down direction refers to a direction along the line of intersection of the face surface and a surface that passes through the center of gravity of the head and is orthogonal to the shaft axis.
- In the system according to an aspect of the present invention, preferably the at least one head identifier is positioned for specification of an orientation and a center of gravity of the head, the image pickup apparatuses capture the images of the golf club, the golf club including the at least one head identifier and at least one shaft axis identifier positioned for specification of a shaft axis of the golf club, the position information acquisition unit acquires position information of the at least one head identifier and the at least one shaft axis identifier from the images, and the measurement unit measures the centrifugal force and the inertial force as the force acting on the head of the golf club by resolving the centrifugal force and the inertial force into the components in the striking direction of the swing and the toe down direction based on the position information of the at least one head identifier and the at least one shaft axis identifier.
- According to this structure, it is possible to provide indices for a more detailed analysis of the swing by easily and more accurately measuring the force acting on the head during the swing in the striking direction and the toe down direction.
- In the system according to an aspect of the present invention, the measurement unit preferably further measures, as the force acting on the golf club, torque acting on a shaft of the golf club based on the centrifugal force and the inertial force.
- According to this structure, it is possible to provide indices for a more detailed analysis of torsion acting on the shaft of the golf club during the swing by measuring torque acting on the shaft during the swing. In the present description, torque refers to the force applied in the torsion direction.
- A measurement apparatus according to an aspect of the present invention for achieving the above object is an apparatus for measuring force acting on a head of a golf club during a swing, wherein the apparatus measures the force acting on the head of the golf club based on position information of at least one head identifier attached to the head for specification of a position on the head, the position information being acquired from an image of the golf club captured during the swing.
- The apparatus according to an aspect of the present invention can measure the force acting on the head during a swing as usual by a golfer.
- A golf swing measurement method according to an aspect of the present invention for achieving the above object is a method for measuring force acting on a head of a golf club during a swing, comprising the steps of: attaching at least one head identifier to the head for specification of a position on the head; capturing an image of the golf club including the at least one head identifier; acquiring position information of the at least one head identifier from the image of the golf club captured during the swing; and determining the force acting on the head of the golf club based on the position information.
- The method according to an aspect of the present invention can measure the force acting on the head during a swing as usual by a golfer.
- According to the present invention, it is possible to measure the force acting on the head during a swing as usual by a golfer.
- The present invention will be further described below with reference to the accompanying drawings, wherein:
-
FIG. 1 is a schematic view of a golf swing measurement system according to an embodiment of the present invention; -
FIG. 2 is a functional block diagram schematically illustrating the structure of a golf swing measurement apparatus according to the embodiment of the present invention; -
FIG. 3 is a flowchart illustrating an example of the golf swing measurement method according to the embodiment of the present invention; -
FIG. 4 illustrates an example of a golf club used in the golf swing measurement system according to the embodiment of the present invention; -
FIG. 5 is a diagram illustrating an example of a centrifugal force decomposition method when measuring a swing using the golf club illustrated inFIG. 4 ; -
FIG. 6 is another diagram illustrating an example of the centrifugal force decomposition method when measuring a swing using the golf club illustrated inFIG. 4 ; -
FIG. 7 is a diagram illustrating an example of an inertial force decomposition method when measuring a swing using the golf club illustrated inFIG. 4 ; -
FIG. 8 is another diagram illustrating an example of the inertial force decomposition method when measuring a swing using the golf club illustrated inFIG. 4 ; -
FIG. 9A is a diagram illustrating an example of inertial force decomposition immediately after the start of a downswing when measuring a swing using the golf club illustrated inFIG. 4 ; -
FIG. 9B is a diagram illustrating an example of inertial force decomposition in the middle of the downswing when measuring a swing using the golf club illustrated inFIG. 4 ; -
FIG. 9C is a diagram illustrating an example of inertial force decomposition immediately before impact when measuring a swing using the golf club illustrated inFIG. 4 ; -
FIG. 10 is a diagram illustrating an example of a decomposition method for resolving a centrifugal force into a component in a torsion direction when measuring a swing using the golf club illustrated inFIG. 4 ; -
FIG. 11 is another diagram illustrating an example of a decomposition method for resolving a centrifugal force into a component in the torsion direction when measuring a swing using the golf club illustrated inFIG. 4 ; -
FIG. 12 is a diagram illustrating an example of a method of calculating torque derived from an inertial force when measuring a swing using the golf club illustrated inFIG. 4 ; -
FIG. 13A illustrates the results of measuring forces derived from an inertial force and a centrifugal force in a striking direction when a robot executes a swing; -
FIG. 13B illustrates the results of measuring forces derived from an inertial force and a centrifugal force in a toe down direction when a robot executes a swing; -
FIG. 14A illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the striking direction illustrated inFIG. 13A and a flex amount of the shaft; -
FIG. 14B illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the toe down direction illustrated inFIG. 13B and the flex amount of the shaft; -
FIG. 15A illustrates the results of measuring forces derived from an inertial force and a centrifugal force in the striking direction when a human executes a swing; -
FIG. 15B illustrates the results of measuring forces derived from an inertial force and a centrifugal force in the toe down direction when a human executes a swing; -
FIG. 16A illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the striking direction illustrated inFIG. 15A and the flex amount of the shaft; -
FIG. 16B illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the toe down direction illustrated inFIG. 15B and the flex amount of the shaft; -
FIG. 17A illustrates the results of measuring torque derived from an inertial force and a centrifugal force on the shaft when a robot executes a swing; -
FIG. 17B illustrates the results of measuring torque derived from an inertial force and a centrifugal force on the shaft when a human executes a swing; -
FIG. 18A illustrates the relationship between the sum of torque derived from the inertial force and from the centrifugal force illustrated inFIG. 17A and a torsion angle of the shaft calculated based on markers; -
FIG. 18B illustrates the relationship between the sum of torque derived from the inertial force and from the centrifugal force illustrated inFIG. 17B and the torsion angle of the shaft calculated based on markers; and -
FIG. 19 illustrates an example of a golf club used for measurement of torsion acting on the golf club during a swing. - The following will describe a golf swing measurement system, measurement apparatus, and measurement method according to an embodiment of the present invention in detail with reference to the drawings.
-
FIG. 1 is a schematic view of the golf swing measurement system according to the embodiment of the present invention. A golfswing measurement system 1 illustrated inFIG. 1 is a measurement system for measuring forces acting on the head on agolf club 5 when agolfer 4 swings thegolf club 5. Themeasurement system 1 is provided with afirst camera 2A and asecond camera 2B, constituting at least two image pickup apparatuses, and ameasurement apparatus 3 that measures forces acting on the head based on images of the golf club captured during the swing. - The
first camera 2A and thesecond camera 2B capture images of a marker 6 (head identifier), which constitutes at least one identifier attached to the head for specification of a position on the head. Themarker 6 is made from a material that can be distinguished from its surroundings in a captured image of thegolf club 5. For example, themarker 6 is reflective tape or paint. Themarker 6 is, for example, preferably positioned on the head near the base of the shaft. This makes it possible to acquire position information on the head during a swing with little effect from the flex and torsion of the golf club. - The
first camera 2A and thesecond camera 2B are, for example, high-speed video cameras capable of highly-sensitive filming of video with abundant movement. The frame rate when thefirst camera 2A and thesecond camera 2B film the swing is, for example, 160 Hz. - The
measurement apparatus 3 measures the forces acting on the head of thegolf club 5 based on the position information of themarker 6 acquired from the images of thegolf club 5 captured by thefirst camera 2A and thesecond camera 2B during the swing by thegolfer 4. Themeasurement apparatus 3 is constituted by a computer provided, for example, with a Central Processing Unit (CPU) or a Digital Signal Processor (DSP). -
FIG. 2 is a functional block diagram schematically illustrating the structure of themeasurement apparatus 3. Themeasurement apparatus 3 is provided withimage acquisition units calculation unit 10 constituted by, for example, a CPU or a DSP, acontrol unit 11 that controls each functional unit provided in themeasurement apparatus 3, adisplay unit 12 that displays measurement results, and adatabase 13 that stores data such as measurement results and golf club specifications. Theimage acquisition units calculation unit 10 is provided with a positioninformation acquisition unit 8 that acquires position information and ameasurement unit 9 that measures forces acting on the head of thegolf club 5. An overview of operations by each functional unit will be provided below with reference to the flowchart for the golf swing measurement method according to the embodiment of the present invention shown inFIG. 3 . -
FIG. 3 is a flowchart illustrating an example of the golf swing measurement method according to the embodiment of the present invention. In this explanation, thegolfer 4 inFIG. 1 executes a swing with thegolf club 5. First, thefirst camera 2A and thesecond camera 2B constituting at least two image pickup apparatuses capture images, during a swing, of themarker 6 attached to the head (step S01). Subsequently, via theimage acquisition units measurement apparatus 3 acquires image data for themarker 6 during the swing from thefirst camera 2A and thesecond camera 2B (step S02). The image data for themarker 6 may be video data of any format captured by thefirst camera 2A and thesecond camera 2B. - Via the position
information acquisition unit 8, themeasurement apparatus 3 extracts any image data from the image data captured by thefirst camera 2A and thesecond camera 2B in step S02, recognizes the marker in the extracted image data, and acquires position information on the recognized marker (step S03). - The position
information acquisition unit 8 recognizes the marker attached to thegolf club 5 by, for example, a circle fitting method applied, for example, to any number of frames extracted from the video data acquired from thefirst camera 2A and thesecond camera 2B. A circle fitting method is a method to extract the outline of a circular marker (a sphere in 3D space), establish a circle approximating the extracted outline, and calculate the virtual center point of the marker. Furthermore, as the position information of themarker 6, the positioninformation acquisition unit 8 acquires 3D coordinates with a general method, such as a triangulation method. The positioninformation acquisition unit 8 can store information on the acquired 3D coordinates in association with the golfer who executed the swing in thedatabase 13. - Via the
measurement unit 9, themeasurement apparatus 3 determines forces acting on the head of thegolf club 5 based on the position information acquired in step S03 (step S04). Themeasurement apparatus 3 can then display measurement results, as in the examples inFIGS. 14A through 18B , on thedisplay unit 12. - The
measurement unit 9 preferably measures the centrifugal force acting on the head based on the position information of themarker 6. - Specifically, the
measurement unit 9 can approximate a virtual rotation center and virtual circle for the head during a swing based on the position information of themarker 6 at any time tn and times before and after tn, i.e. tn−1 and tn+1. Note that the virtual circle can be calculated as, for example, the trajectory traversed by the position of the center of gravity of the head. The centrifugal force Fc acting on the head can be calculated based on the following equation, using the radius r of the virtual circle, as well as the mass m and velocity v, calculated from the position information at times tn, tn−1 and tn+1, of the head of thegolf club 5. The centrifugal force Fc is an apparent force that acts outwards, from the center of rotation, on the head of the golf club during the swing. -
F c =mv 2 /r - Furthermore, the
measurement unit 9 preferably calculates the inertial force Fi corresponding to acceleration obtained by differentiating the absolute value of the above velocity v. Letting the derivative of the absolute value of the velocity of the head of thegolf club 5 be a and the mass of the head be m, the inertial force Fi is calculated with the following equation. -
F i =−ma - The inertial force Fi referred to in the present description is an apparent force corresponding to the acceleration acting on the head at each point in time.
- By thus performing non-contact measurement of a golf swing, the golf
swing measurement system 1 according to the present embodiment can measure the forces acting on the head during a golf swing as usual by a golfer. Furthermore, as the forces acting on the head of the golf club, the golf swing measurement system according to the present embodiment can measure the centrifugal force and the inertial force acting on the head. Moreover, performing measurements without use of an acceleration sensor eliminates the effect of the mass of the acceleration sensor on the measurement value, thereby offering the advantage of not requiring calculation to adjust for the effect of the mass of the acceleration sensor. - The forces acting in the striking direction of the swing and the toe down direction greatly affect the direction and distance traveled by the golf ball, the travel velocity, and the like. Therefore, as indices for assessing the swing, it is also extremely important to assess forces acting in the striking direction of the swing and the toe down direction. Furthermore, toe down of the head when the golf club is swung has been considered to be caused by centrifugal force generated during the swing, but the causal relationship has not been made clear. The striking direction of the swing refers to the direction in which the ball is struck by the swing and is determined by the orientation of the face surface of the head at the time of impact. Therefore, in the present description, the direction perpendicular to the face surface is referred to as the striking direction. Toe down typically refers to the change in position of the head in the shaft axis direction occurring during a swing. In the present description, however, the toe down direction refers to a direction along the line of intersection of the face surface and a surface that passes through the center of gravity of the head and is orthogonal to the shaft axis.
- Furthermore, via the
measurement unit 9, the golfswing measurement system 1 according to the present embodiment preferably measures the centrifugal force Fc and the inertial force Fi as the forces acting on the head of the golf club by resolving these forces into components in the striking direction of the swing and the toe down direction. The method for resolving the forces acting on the head of the golf club into the components in the striking direction of the swing and the toe down direction will be described with reference toFIGS. 4 through 8 . -
FIG. 4 illustrates an example of a golf club used in the golf swing measurement system according to the present embodiment. Agolf club 18 has agrip 14, ashaft 15, and ahead 16. Thegolf club 18 preferably has shaft axis markers M1 and M2 (shaft axis identifiers) positioned to allow for specification of the axis of theshaft 15 and head markers M3 and M4 (head identifiers) positioned to allow for specification of the orientation and the center of gravity of the head. The shaft axis markers M1 and M2 are positioned to allow for specification of the axis of theshaft 15. For example, the shaft axis markers M1 and M2 are positioned with their center along the shaft axis. Theshaft 15 flexes during a swing, but since the shaft axis markers M1 and M2 are positioned near thegrip 14, which flexes relatively less, the shaft axis calculated based on the shaft axis markers M1 and M2 corresponds to the axis of theshaft 15 when theshaft 15 does not flex at all during a swing. - The head markers M3 and M4 are preferably positioned on the
head 16 in a configuration such that information on the orientation of the face surface of thehead 16 and on the position of the center of gravity of thehead 16 can be obtained. Accordingly, the configuration of the head markers is not limited to the configuration shown in the drawings. For example, it is of course possible to use only one head marker in the shape of a line parallel to the face surface. Themeasurement system 1 obtains information on the position of the center of gravity during a swing by acquiring information on the position of the center of gravity of thehead 16 from the golf club specifications and determining the distance to the head markers M3 and M4 and the axis of theshaft 15 as well as the relative positions thereof with respect to the center of gravity. Note that while the trajectory traversed by the position of the center of gravity has been assumed to be a virtual circle, it is of course possible to adopt a simpler method that calculates the forces acting on thehead 16 by calculating the trajectory traversed by the head marker as the virtual circle. -
FIG. 5 is a diagram illustrating an example of a centrifugal force decomposition method when measuring a swing using the golf club illustrated inFIG. 4 , the swing being viewed from the front. For clarity, theshaft 15 and thegrip 14 are not illustrated but rather are represented by ashaft axis 15A. The centrifugal force Fc is an apparent force that acts outwards, from the above-described virtual rotation center RC, on the center of gravity G of thehead 16. The magnitude of the centrifugal force Fc can be represented as Fc=mv2/r (where m is the mass of the head, v is the velocity of the head, and r is the radius of the virtual circle). In order to resolve the centrifugal force Fc in the striking direction of the swing and the toe down direction, themeasurement unit 9 first resolves the centrifugal force Fc into a force F1 in a direction perpendicular to theshaft axis 15A. This decomposition is performed, for example, with the following equation. -
F 1 =F c sinθ1 - Here, the angle θ1 is the angle between the
shaft axis 15A and a line connecting the virtual rotation center RC with the center of gravity G of thehead 16. -
FIG. 6 is a top view illustrating an example of a centrifugal force decomposition method when measuring a swing using the golf club illustrated inFIG. 4 . InFIG. 6 , a line parallel to the face surface of thehead 16 connecting the head markers M3 and M4 is labeled FL, and a line parallel to the line FL and traversing the center of gravity G is labeled FLp. For clarity, the head markers M3 and M4 and theshaft 15 are illustrated with their respective centers aligned with the face surface of thehead 16. The force F1 calculated as described above is a force in the normal direction from the center of gravity G towards theshaft axis 15A, as illustrated inFIG. 6 . Based on the center of gravity angle θG, the force F1 is resolved by the following equation into a striking direction centrifugal force Fcf and a toe down direction centrifugal force Fct centered on the center of gravity G. -
F cf =F 1 sinθG -
F ct =F 1 cosθG - Note that the center of gravity angle θG is the angle between the face surface of the head and a line connecting the position of the center of gravity with the center of the position of attachment of the
shaft 15. The center of gravity angle θG may also be acquired from the specifications for thegolf club 18 or the like. Furthermore, the center of gravity angle θG can be derived from calculating the angle between a line parallel to the face surface of the head acquired from the head markers M3 and M4 and the line connecting the position of the center of gravity with the center of the position of attachment of theshaft 15. In this way, the golfswing measurement system 1 according to the present embodiment can calculate the striking direction centrifugal force and the toe down direction centrifugal force acting on thegolf club 18 during a swing. -
FIGS. 7 and 8 are diagrams illustrating an example of a decomposition method for an inertial force Fi when measuring a swing using the golf club illustrated inFIG. 4 . In these figures, the angle θ2 is the angle between aline 15P parallel to theshaft axis 15A and a tangent a to thevirtual circle 19, which approximates the trajectory of the center of gravity G during the swing. Themeasurement unit 9 inFIG. 2 differentiates the absolute value of the velocity during the swing to calculate the magnitude of the acceleration a in a direction matching the tangent to thevirtual circle 19.FIG. 7 illustrates the inertial force Fi, which is an apparent force that acts in the opposite direction of the acceleration a. Furthermore, by the following equation, themeasurement unit 9 measures a force F2 that traverses the center of gravity G in a direction perpendicular to theshaft axis 15A. -
F 2 =F i sinθ2 - As illustrated in
FIG. 8 , themeasurement unit 9 resolves the force F2 into a toe down direction inertial force Fit and a striking direction inertial force Fif centered on the center of gravity G using the equations below. Here, the angle θ is the angle between the face surface of the head and the inertial force vector. InFIG. 8 , as inFIG. 6 , a line parallel to the face surface of thehead 16 connecting the head markers M3 and M4 is labeled FL, and a line parallel to the line FL and traversing the center of gravity G is labeled FLp. -
F if =F 2 sinθ -
F it =F 2 cosθ - As described with reference to
FIGS. 7 and 8 , the golf swing measurement system according to the present embodiment can resolve, in the striking direction and in the toe down direction, the inertial force acting on thehead 16 of thegolf club 5 during a swing. As a result, themeasurement system 1 can provide indices for a more detailed analysis of the swing. An example of resolving the inertial force at three points in time during a golf swing will now be described with reference toFIGS. 9A through 9C . The three points in time during the golf swing are (1) immediately after the start of the downswing, in which thegolfer 4 swings thegolf club 5 down; (2) the middle of the downswing; and (3) immediately before impact of thehead 16 with the golf ball. At the point in time (1) immediately after the start of the downswing, the face of thehead 16 is open and is facing ahead of thegolfer 4. At the point in time (2) at the middle of the downswing, the face is closed and is slanted with respect to the front of thegolfer 4. At the point in time (3) immediately before impact, the face is closed and is facing sideways with respect to the front of thegolfer 4. -
FIG. 9A is a top view illustrating an example of inertial force decomposition immediately after the start of a downswing. Immediately after the start of the downswing, the face surface of thehead 16 is open towards the front of thegolfer 4. Since thegolfer 4 swings thegolf club 5 down with thehead 16 in this state, thehead 16 moves in the direction of theshaft axis 15A. - Therefore, the acceleration ah acts from the center of gravity G towards the left in the figure, and the inertial force Fi is a force in the opposite direction. Using the same equations as described with reference to
FIG. 8 , themeasurement unit 9 resolves the force F2 into a toe down direction inertial force Fit and a striking direction inertial force Fif centered on the center of gravity G. -
FIG. 9B is a diagram illustrating an example of inertial force decomposition in the middle of the downswing. The face surface of thehead 16 gradually closes in the middle of the downswing so as to be slanted with respect to the front of thegolfer 4. Therefore, the acceleration ah acts in the direction shown in the figure, and the inertial force Fi is a force in the opposite direction. Using the same equations as described with reference toFIG. 8 , themeasurement unit 9 resolves the force F2 into a toe down direction inertial force Fit and a striking direction inertial force Fif centered on the center of gravity G. -
FIG. 9C is a diagram illustrating an example of inertial force decomposition immediately before impact. The face surface of thehead 16 is closed immediately before impact and faces sideways with respect to the front of thegolfer 4. Therefore, the acceleration ah acts in the direction shown in the figure, and the inertial force Fi is a force in the opposite direction. Using the same equations as described with reference toFIG. 8 , themeasurement unit 9 resolves the force F2 into a toe down direction inertial force Fit and a striking direction inertial force Fif centered on the center of gravity G. - As described with reference to
FIGS. 4 through 9 , the golfswing measurement system 1 according to the present embodiment can resolve, in the striking direction and the toe down direction, the centrifugal force and the inertial force acting on the golf club during a swing. In this way, among the forces acting on the head of the golf club, the force contributing in the striking direction and the force contributing in the toe down direction are calculated, thus permitting a more detailed analysis of the swing. - Furthermore, the golf
swing measurement system 1 according to the present embodiment preferably also measures the torque contributing to torsion of the shaft as a force acting on the golf club by measuring the torque from each of the centrifugal force and the inertial force acting on the golf club during the swing. This measurement will be described with reference toFIGS. 10 through 12 . -
FIG. 10 is a diagram illustrating an example of a decomposition method for resolving a centrifugal force into a component in a torsion direction when measuring a swing using the golf club illustrated inFIG. 4 . The torsion direction refers to the direction in which the head rotates around the shaft axis of the golf club and is a rotational direction either forwards or backwards with respect to the direction of travel. In the present description, the force applied in the torsion direction is referred to as torque.FIG. 10 is a front view of thegolf club 5. A line parallel to theshaft axis 15A and traversing the center of gravity G of thehead 16 is labeled 15P. The centrifugal force Fc acting on thehead 16 during the swing acts on the center of gravity G of thehead 16 in a direction away from the above-described virtual rotation center RC. Therefore, in order first to calculate the centrifugal force in the torsion direction, themeasurement unit 9 needs to calculate a component Fcg of the centrifugal force Fc along theline 15P by the following equation, using the angle θ1 between theshaft axis 15A of theshaft 15 of thegolf club 18 and a line connecting the virtual rotation center RC with the center of gravity G of thehead 16. -
F cg =F c cosθ1 - The
measurement unit 9 then uses the component Fcg of the centrifugal force Fc along theline 15P as well as an angle θSG, which is the angle between theshaft axis 15A and a line connecting the position at which theshaft axis 15A meets the head 16 (referred to below as the “contact point”) with the center of gravity G of thehead 16, to calculate a force Fcgf using the following equation. The force Fcgf is a force acting on the center of gravity G with the contact point as a point of support and is a decomposition, from the component Fcg of the centrifugal force Fc, of a force in a direction approximately perpendicular to the face of thehead 16. -
F cgf =F cg*sinθSG*cosθSG - Here, sinθSG and cosθSG can be derived from the value of tanθSG. The value of tanθSG can be calculated by the following equation based on the face height α, the center of gravity height β, and the center of gravity depth γ.
-
tanθSG=center of gravity depth γ/(face height α−center of gravity height β) - The face height α refers to the height from the bottom of the golf club to the upper edge of the face. The center of gravity height β refers to the height from the bottom of the golf club to the center of gravity in the direction of the
shaft axis 15A. The center of gravity depth y refers to the distance from the center of gravity of the golf club to the face surface in a direction perpendicular to theshaft axis 15A. Note that the face height α, center of gravity height β, and center of gravity depth γ for a variety of golf club heads can be obtained from the specifications for the golf clubs. - As illustrated in
FIG. 11 , themeasurement unit 9 calculates a torsion direction centrifugal force Fctr by the following equation, using the above-described force Fcgf and the center of gravity angle θG between the face surface of the head and a line connecting the position of the center of gravity with the center of the position of attachment of theshaft 15. The torsion direction centrifugal force Fctr is a centrifugal force in the torsion direction derived from the centrifugal force acting on the center of gravity G during the swing. -
F ctr =F cgf*cosθG - Finally, with the following equation, the
measurement unit 9 calculates the torque Tc around theshaft axis 15A derived from the centrifugal force by multiplying the torsion direction centrifugal force Fctr by the center of gravity distance L. -
T c =F ctr *L - Note that the center of gravity distance L refers to the distance from the center of gravity G of the
head 16 to theshaft axis 15A and can be obtained from the specifications for the golf club. -
FIG. 12 is a diagram illustrating an example of a method of calculating the torque Ti derived from an inertial force. Themeasurement unit 9 inFIG. 2 calculates the inertial force Fi as Fi=−ma, where a is the derivative of the absolute value of the velocity v of thehead 16 and m is the mass of thehead 16. Themeasurement unit 9 then uses the center of gravity angle θG and an angle θFL between a tangent to the trajectory of thehead 16 and the line FL parallel to the face surface to calculate a torsion direction inertial force Fitc, around theshaft axis 15A, that forms a 90° angle with respect to a line connecting the center of gravity G and theshaft axis 15A and that acts backward with respect to the direction of travel of thehead 16. -
F itc =F i*cos(90°−θFL+θG) - With the following equation, the
measurement unit 9 then calculates the torque Ti around theshaft axis 15A derived from the inertial force by multiplying the torsion direction inertial force Fitr by the center of gravity distance L. -
T i =F itr *L - Note that the center of gravity distance L refers to the distance from the center of gravity G of the
head 16 to theshaft axis 15A and can be obtained from the specifications for the golf club. - In this way, the golf
swing measurement system 1 according to the present embodiment can calculate the torque derived from the centrifugal force Fc and from the inertial force Fi. It is considered that the torque Tc derived from the centrifugal force causes torsion in the direction of travel, whereas the torque Ti derived from the inertial force causes torsion in the direction opposite the direction of travel. Accordingly, taking sign into consideration, it is thought that if the sum of the torque (Tc+Ti) is a positive value, theshaft 15 of thegolf club 18 is twisted in the direction of travel. Conversely, if the sum of the torque (Tc+Ti) is a negative value, torsion occurs in the direction opposite the direction of travel. Accordingly, by summing the calculated values of torque, the golfswing measurement system 1 can analyze the torsion acting on theshaft 15 of thegolf club 18 in greater detail. - Measurement results by the golf
swing measurement system 1 according to the present embodiment will now be described with reference toFIGS. 13A through 16B . Here, measurement was performed for a swing using a golf club having an additional marker on thehead 16 near the base of theshaft 15 of thegolf club 18 illustrated inFIG. 4 .FIG. 13A illustrates the results of measuring forces derived from an inertial force and a centrifugal force in the striking direction when a robot executes a swing.FIG. 13B illustrates the results of measuring forces derived from an inertial force and a centrifugal force in the toe down direction when a robot executes a swing. The vertical axis represents the magnitude of the force (N), and the horizontal axis represents time (s).Time 0 is the time of impact. -
FIG. 14A illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the striking direction illustrated inFIG. 13A and the flex amount of theshaft 15.FIG. 14B illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the toe down direction illustrated inFIG. 13B and the flex amount of theshaft 15. The flex amount of theshaft 15 can be calculated as the distance between the above-described additional marker near the base of theshaft 15 and the shaft axis determined by the shaft axis markers M1 and M2 illustrated inFIG. 4 . As clearly shown inFIGS. 14A and 14B , the flex amount of the shaft as measured with the additional marker and the sum of the centrifugal force and the inertial force exhibit a similar tendency of change over time. Based on this relationship, the golfswing measurement system 1 according to the present embodiment can quantitatively measure the change over time in the magnitude of the applied force with respect to the flex of the shaft during a swing. -
FIG. 15A illustrates the results of measuring forces derived from an inertial force and a centrifugal force in the striking direction when a human executes a swing.FIG. 15B illustrates the results of measuring forces derived from an inertial force and a centrifugal force in the toe down direction when a human executes a swing. Furthermore,FIG. 16A illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the striking direction illustrated inFIG. 15A and the flex amount of the shaft.FIG. 16B illustrates the relationship between the sum of forces derived from the inertial force and the centrifugal force in the toe down direction illustrated inFIG. 15B and the flex amount of the shaft. For a human as well, it is clear that the flex amount of the shaft and the sum of the centrifugal force and the inertial force exhibit a similar tendency of change over time. - Another example of measurement results by the golf
swing measurement system 1 according to the present embodiment will now be described with reference toFIGS. 17A through 18B . Here, measurement was performed for a swing using agolf club 18A illustrated inFIG. 19 . Thegolf club 18A is thegolf club 18 illustrated inFIG. 4 with a marker M5 on a mounting 20 at the upper portion of theshaft 15. In order to verify the torque acting on the golf club during a swing measured by themeasurement system 1 according to the present embodiment, the torsion acting on the golf club during a swing was calculated based on the relative positions of the head markers M3 and M4 on thehead 16 and the marker M5. -
FIG. 17A illustrates the results of measuring torque derived from an inertial force and a centrifugal force on theshaft 15 when a robot executes a swing.FIG. 17B illustrates the results of measuring torque derived from an inertial force and a centrifugal force on theshaft 15 when a human executes a swing. With the above-described method, the torque derived from each of the centrifugal force and the inertial force on theshaft 15 was measured, and the sum of the values of the torque was calculated.FIGS. 18A and 18B illustrate the relationship between the sum of torque derived from the inertial force and from the centrifugal force illustrated inFIGS. 17A and 17B and the torsion angle of the shaft calculated based on the above-described markers. As shown byFIGS. 18A and 18B , the sum of the calculated torque values and the torsion angle of the golf club exhibit a similar tendency of change. - It is to be noted that many modifications and substitutions within the scope and spirit of the present invention will be apparent to a person of ordinary skill in the art. Accordingly, the present invention is not limited to the above embodiment but rather may be modified or altered in a variety of ways without deviating from the scope of the present invention.
- 1: Measurement system
- 2A, 2B: Camera (image pickup apparatus)
- 3: Measurement apparatus
- 4: Golfer
- 5, 18: Golf club
- 6: Marker (head identifier)
- 7A, 7B: Image acquisition unit
- 8: Position information acquisition unit
- 9: Measurement unit
- 10: Calculation unit
- 11: Control unit
Claims (7)
1. A system for measuring force acting on a head of a golf club during a swing, comprising:
at least two image pickup apparatuses each configured to capture an image of the golf club, the golf club including at least one head identifier attached to the head for specification of a position on the head; and
a measurement apparatus configured to measure the force acting on the head of the golf club based on position information of the at least one head identifier, the position information being acquired from the images of the golf club captured by the image pickup apparatuses during the swing.
2. The system according to claim 1 , wherein the measurement apparatus comprises:
an image acquisition unit configured to acquire the images of the golf club during the swing from the image pickup apparatuses;
a position information acquisition unit configured to recognize the at least one head identifier in the acquired images and to acquire position information of the recognized at least one head identifier; and
a measurement unit configured to measure, as the force acting on the head of the golf club, a centrifugal force and an inertial force acting on the head of the golf club based on the acquired position information.
3. The system according to claim 2 , wherein the measurement unit measures the centrifugal force and the inertial force as the force acting on the head of the golf club by resolving the centrifugal force and the inertial force into components in a striking direction of the swing and a toe down direction.
4. The system according to claim 3 , wherein the at least one head identifier is positioned for specification of an orientation and a center of gravity of the head,
the image pickup apparatuses capture the images of the golf club, the golf club including the at least one head identifier and at least one shaft axis identifier positioned for specification of a shaft axis of the golf club,
the position information acquisition unit acquires position information of the at least one head identifier and the at least one shaft axis identifier from the images, and
the measurement unit measures the centrifugal force and the inertial force as the force acting on the head of the golf club by resolving the centrifugal force and the inertial force into the components in the striking direction of the swing and the toe down direction based on the position information of the at least one head identifier and the at least one shaft axis identifier.
5. The system according to claim 4 , wherein the measurement unit further measures, as the force acting on the golf club, torque acting on a shaft of the golf club based on the centrifugal force and the inertial force.
6. An apparatus for measuring force acting on a head of a golf club during a swing, wherein the apparatus measures the force acting on the head of the golf club based on position information of at least one head identifier attached to the head for specification of a position on the head, the position information being acquired from an image of the golf club captured during the swing.
7. A method for measuring force acting on a head of a golf club during a swing, comprising the steps of:
attaching at least one head identifier to the head for specification of a position on the head;
capturing an image of the golf club including the at least one head identifier;
acquiring position information of the at least one head identifier from the image of the golf club captured during the swing; and
determining the force acting on the head of the golf club based on the position information.
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JP2012-115796 | 2012-05-21 | ||
JP2012115796A JP6112780B2 (en) | 2012-05-21 | 2012-05-21 | Golf swing measurement system, measurement device, and measurement method |
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US20130305806A1 true US20130305806A1 (en) | 2013-11-21 |
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ID=49580173
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US13/839,950 Abandoned US20130305806A1 (en) | 2012-05-21 | 2013-03-15 | Golf swing measurement system, measurement apparatus, and measurement method |
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US20140135139A1 (en) * | 2012-11-13 | 2014-05-15 | Keio University | Golf swing analysis device and golf swing analysis method |
US20160335911A1 (en) * | 2014-03-27 | 2016-11-17 | Seiko Epson Corporation | Golf club determination method, golf club determination device, and golf club determination program |
US10565888B2 (en) | 2013-02-17 | 2020-02-18 | Ronald Charles Krosky | Instruction production |
US20210223032A1 (en) * | 2020-01-16 | 2021-07-22 | Creatz Inc. | Method, system, and non-transitory computer-readable recording medium for measuring physical quantities associated with a golf club |
US11945278B2 (en) | 2021-06-24 | 2024-04-02 | Ford Global Technologies, Llc | Enhanced vehicle suspension |
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JP6247339B2 (en) * | 2016-06-08 | 2017-12-13 | 良隆 伊藤 | Ball hitting tool manufacturing method and measuring ball hitting tool used in the method |
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KR102439549B1 (en) * | 2020-09-14 | 2022-09-02 | 주식회사 골프존 | Device for sensing golf swing and method for sensing impact position on club head using the same |
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US20210223032A1 (en) * | 2020-01-16 | 2021-07-22 | Creatz Inc. | Method, system, and non-transitory computer-readable recording medium for measuring physical quantities associated with a golf club |
US11946734B2 (en) * | 2020-01-16 | 2024-04-02 | Creatz Inc. | Method, system, and non-transitory computer-readable recording medium for measuring physical quantities associated with a golf club |
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JP2013240486A (en) | 2013-12-05 |
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