JP2011130964A - Swing measuring system in tool of exercise such as golf - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for measuring movement in both of vertical and horizontal planes in a golf club or general exercise tools with a single camera and particularly making head movement, a blow angle and a trajectory of the golf club head in a golf swing to be easily measured. <P>SOLUTION: A velocity v in a primary movement direction and a head speed HS, separately measured, measure a position in a depth direction of the golf club head or another object to be measured, thereby acquiring image coordinate values of a calibration point with calculations to enable two-dimensional space coordinates of the objective point to be measured in a position apart from a calibration plane to be measured. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for measuring the behavior of a golf club or other exercise equipment during a swing.

  Conventionally, as a method of knowing the behavior of a golf club or exercise equipment during a swing, a still image taken from two or more directions is analyzed and its position is measured, and further, an angular orientation, displacement, speed, angular velocity, acceleration, angular acceleration. Is known (see, for example, Patent Document 1). In this method, a spatial three-dimensional coordinate of a measurement target point on a golf club is measured using an image measurement method called a three-dimensional DLT method, and a plurality of cameras must be synchronized and photographed.

  Further, there is also known a method of separately measuring a motion on a vertical plane and a motion on a horizontal plane without using the three-dimensional DLT method (see, for example, Patent Document 2). Although it is not always necessary to synchronize each camera with this method, it is the same as the above method that a plurality of cameras are required to grasp the behavior of the golf club on both vertical and horizontal surfaces. .

JP 2009-45495 A JP 9-215807 A

  In the swing behavior of golf clubs and exercise equipment, both vertical and horizontal movements are important. For example, one of the behaviors noted on the vertical plane is called a blow angle. This is the vertical angle of the movement of the golf club head at the moment of impact, and in the case of downward movement called down blow, the hit ball has low jumping and increases back spin, and in the case of upward movement called upper blow In many cases, the hit ball has a high pop-up and less backspin. One of the points of interest on the horizontal plane is called a head trajectory. This is the horizontal and horizontal angle of the movement of the golf club head at the moment of impact. When the golfer moves from near to far, the inside-out trajectory is called an inside-out trajectory, and the hit ball takes a so-called hook spin. It becomes easy to take.

  As described above, when measuring movements on both vertical and horizontal planes using conventional methods and devices, at least two cameras are required, which increases the size and cost of the device and restricts installation and use. As a result, it has been difficult to use in fields that are important in sports such as outdoor fields.

  Although the above has described the case of a golf club, the same applies to other sports in which a hitting tool is swung.

  In view of such circumstances, the present invention intends to provide a method and apparatus for measuring movements on both vertical and horizontal planes of a golf club or exercise equipment in general with a single camera. In particular, it facilitates measurement of the behavior, blow angle and head trajectory of a golf club head during a golf swing.

The present invention is an image measurement device for swing behavior of exercise equipment,
A speed measurement unit that measures the speed v (m per second) of the main motion direction of the exercise tool;
A shooting unit that shoots a still image of the exercise tool t (seconds) before hitting from the back in the main direction of movement;
For a point on a still image captured by the imaging unit, a coordinate calculation unit that calculates two-dimensional coordinates in real space excluding the imaging direction,
The coordinate calculation unit obtains the image coordinates of the calibration point on the plane whose normal is the main movement direction at the hitting position, and the image coordinates when the calibration point is translated in the main movement direction. Calculate in advance the coordinate function of the calibration point with the translation distance as a variable,
In the measurement, the distance L from the shot position of the taken exercise tool is obtained as a product v × t of the speed and time of the main movement direction of the exercise tool to be measured,
Substituting this into the coordinate function as a variable, calculating the virtual calibration point coordinate value on the plane containing the taken exercise tool,
Calculate the conversion function from image coordinates to spatial coordinates using the virtual calibration coordinate values,
The present invention relates to an image measuring device that uses this to obtain a two-dimensional coordinate value of an exercise tool.

Especially those used for measuring golf club heads are:
An image measuring device for golf swing behavior,
A speed measurement unit that measures the head speed HS (m / s) of the golf club;
A shooting unit that shoots a still image of the exercise equipment t (seconds) before impact from the rear in the flying ball horizontal direction;
For a point on a still image captured by the imaging unit, a coordinate calculation unit that calculates two-dimensional coordinates in real space excluding the imaging direction,
The coordinate calculation unit obtains the image coordinates of the calibration point on the plane normal to the flying ball horizontal direction at the impact position, and the image coordinates when the calibration point is translated in the flying ball horizontal direction. The coordinate function of the calibration point with this parallel movement distance as a variable is calculated in advance,
In the measurement, the distance L from the shot position of the photographed exercise equipment is obtained as the product HS × t of the head speed and time of the exercise equipment to be measured,
Substituting this into the coordinate function as a variable, calculating the virtual calibration point coordinate value on the plane containing the taken exercise tool,
Calculate the conversion function from image coordinates to spatial coordinates using the virtual calibration coordinate values,
The present invention relates to an image measuring device that uses this to obtain a two-dimensional coordinate value of a golf club.

In these,
Take a picture of the moment of impact or impact and measure the two-dimensional spatial coordinate value of the measurement target point,
Displacement in two directions excluding the main direction of movement or the horizontal direction of the flying ball due to the difference between this and the two-dimensional space coordinate value before t (seconds)
Furthermore, from the time t and the speed product t × v or t × HS, by calculating the displacement in the main movement direction or flying ball horizontal direction,
It is also possible to three-dimensionally calculate the displacement of the target point during t (seconds) immediately before hitting or impacting.

  A method of calculating a spatial coordinate value from one image is called a two-dimensional DLT, and the invention described in Patent Document 2 uses this. Therefore, in the present invention, two cameras are required to grasp both the movement in the vertical plane and the movement in the horizontal plane.

  In the two-dimensional DLT, calibration is usually performed on one plane in space, and two-dimensional space coordinates are obtained for measurement target points existing on the plane. Since the image is two-dimensional information and information in the depth direction cannot be obtained, in principle, it is impossible to measure points outside the plane. Approximately, the coordinates of a point outside the plane can also be obtained, but the error increases as the plane deviates because of the parallax of the camera.

  However, the present invention makes it possible to measure the two-dimensional spatial coordinates of the measurement target point at a position outside the calibrated plane by using the velocity v of the main movement direction and the head speed HS measured separately. It is a thing. This greatly expands the measurable range in the depth direction, so that it is possible to measure an object moving in the depth direction of the image, such as when shooting and measuring the golf club head from behind the flying ball.

  According to the present invention, since a single camera is possible, not only the price of the apparatus is reduced, but also the installation is easy, especially the measurement in the outdoor field which is important in sports measurement.

  Each component obtained by dividing by time t is the average velocity vector of the target point during this time t. Take time t sufficiently small and approximate the velocity vector at the moment of impact or impact. It is also possible to obtain.

  According to the present invention, swing measurement of exercise equipment and golf clubs, which conventionally required two or more cameras, can be performed with a single camera, and the measurement device can be reduced in size and price, installation and measurement can be facilitated, It can have an excellent effect of enabling use in places and scenes that are particularly important in sports measurement such as outdoor fields.

The figure which shows the structure and use condition of the apparatus which concern on Example 1. FIG. The figure which shows the installation direction and space coordinate system of the calibration board in Example 1. FIG. The figure which shows the calibration board in Example 1. The figure which shows the installation state of the calibration board in Example 1. The figure which shows the image which image | photographed the calibration board in Example 1.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  This example is a device that measures the direction of motion of a golf club head just before impact, and the blow angle, which is the ratio of the flying ball horizontal component to the vertical component of the velocity of the head, the flying ball horizontal component and The head trajectory angle composed of the ratio of the left and right direction components is measured with a single camera.

  FIG. 1 shows a configuration of the apparatus according to the present invention and an outline at the time of use. The camera 11 is placed behind the golf ball 51 in the flying ball horizontal direction 71 and the golf club head 53 is photographed as the subject swings the golf club 52. The image is captured by a computer 21 having an image capturing unit and displayed on the monitor 22. The golf club head 53 is provided with a marker 54 indicating that it is a measurement target point. By using the mouse 23 and clicking the pointer 24 with the marker 24, the image coordinate value of the measurement target point is calculated by a computer. 21.

  In photographing the golf club head 53, the trigger device 13 is used. Specifically, the camera 11 continues to capture images at predetermined time intervals, the computer 21 records a plurality of past images in a memory or the like, and when new image data is transmitted from the camera 11, The oldest image is deleted and a new image is recorded repeatedly. When a signal is sent from the trigger device, the computer stores a predetermined number of frames before and after the trigger signal is sent. Therefore, it is possible to take out images at favorite times before and after the image immediately before the impact.

  At the time of shooting, the head speed measuring device 12 simultaneously measures the speed of the golf club head 53 in the horizontal direction of the flying ball. This is known in various forms, and the type installed behind the flying ball as shown in FIG. 1 receives the reflected electromagnetic wave reflected back to the golf club head 53, Some measure the speed of the golf club head 53 using the Doppler effect. In some cases, two or more photoelectric switches, magnetic sensors, and the like are installed at predetermined intervals immediately before the golf ball 51, and the head speed is measured from the time difference that the golf club head 53 passes through. In the present invention, there is no limitation on the type and method of the head speed measuring device. Although not shown in the figure, a method in which the head speed measuring device 12 is connected to the computer 21 and the measured head speed is automatically captured is also suitable.

  Next, a calibration method will be described. Since the present invention is a method using two-dimensional DLT, it is basically the same as the calibration method for two-dimensional DLT. However, the present invention is different from the usual in that the calibration board is translated back and forth, images are taken at a plurality of locations, and a function that associates the front and rear positions with the coordinate values is obtained by regression. Thus, while using a two-dimensional DLT method that normally allows only measurement on a calibrated plane, the present invention also enables measurement on a plane that has not been calibrated.

  Hereinafter, a calibration method that is a preliminary preparation for measurement will be described in detail. As shown in FIG. 2, the calibration board 14 is a plane, and the calibration board 14 is installed in a posture in which the flying ball horizontal direction 71 is a normal line of the plane. The spatial coordinates are set in the flying ball horizontal direction 71 with the intersection of the flying ball horizontal direction 71 passing through the center of the ball 51 and the calibration board as the origin, with the calibration boat 14 installed immediately before the golf ball 51. Overlapping the camera direction, the z axis, the vertical direction of the calibration board 14 is the y axis, and the horizontal direction is the x axis. The definition of this coordinate may be changed as appropriate.

  As shown in FIG. 3, the calibration board 14 has a plurality of calibration points 15 and straight lines that should overlap with the x-axis and y-axis of the space at the time of installation. Note that calibration is possible if there is a set of calibration points with different x and y coordinate values in the space. Therefore, the minimum number of calibration points is 2, but in this example, 4 points are taken into account, taking into account errors and the like. It is said. In this embodiment, for easy work and calculation, the space x coordinates of points A and B, C and D, and the space y coordinates of points A and D, B and C are the same. did. Accordingly, the coordinate values are A point (-S, T), B point (-S, -T), C point (S, -T), and D point (S, T), respectively. The values of S and T are preferably about 50 mm.

Imaging of the calibration board, as in FIG. 4, just prior to the golf ball 51 state established a calibration boat 14 0, state 1 is moved in parallel from the golf ball 51 in the camera direction by a distance Z _1, only likewise a distance Z ₂ Three of the translated state 2 were performed. Since it is necessary to carry out in at least two states, and the later regression is performed, the larger the error, the smaller the error. However, since the labor is greatly increased, the third to fifth positions will be practical. Since the states 0 to 2 are parallel movements in the z direction of the space, the space x coordinate and the space y coordinate of each calibration point 15 are the same. The specific distance Z ₁ and distance Z ₂ are about 50 mm and 100 mm, respectively.

  The image coordinate values are input to the computer 21 by operating the mouse 23 and clicking the pointer 24 in accordance with the calibration points A to D. The spatial coordinate value is preferably input from a keyboard or the like.

カメラには視差があるので、各キャリブレーションポイントの空間のx、y座標値は不変だが、画像のx_c、y_c座標値は空間z座標値によって変化する。まずは、この関係を回帰により算出する。以下にその方法を具体的に説明する。 FIG. 5 is a photographed image of the calibration board 14. When x _c and y _c which are coordinates on the image are determined as shown in FIG. 5, the image coordinates in the states 0 to 2 and the respective spatial coordinate values of the calibration points A to D are as shown in Table 1. .

Since the camera has parallax, the x and y coordinate values of the space of each calibration point are unchanged, but the x _c and y _c coordinate values of the image change according to the space z coordinate value. First, this relationship is calculated by regression. The method will be specifically described below.

If a sufficient distance from the camera to the calibration board 14 is taken, the image _xc coordinate value of the calibration point A can be considered as a linear function with the space z coordinate value as a variable. In the case of the present invention, it is appropriate that the distance between the camera 11 and the calibration is about 2.5 to 3 m, and the range in which the calibration board 14 is moved is about 10 to 20 mm. The same applies to the image y _c coordinate of the point A, the image x _c coordinate of the points B to D, and the image y _c coordinate.

The point A will be specifically described. When the space z coordinate value Z is (0, Z ₁ , Z ₂ ), the image x _c coordinate P _A (Z) is (P _A0 , P _A1 , P _A2 ) and the image y _c coordinate Q _A (Z) (Q _A0 , Q _A1 , Q _A2 ) has already been found from the above-described shooting of the calibration board 14 and the input of the calibration point 15. Therefore, here, a function connecting these is assumed as in Equation 1, and the simultaneous equations in Equation 2 are solved. That is, the image coordinates (x _c , y _c ) of the point A are expressed as x _c = P _A (Z), y _c =, Q _A (Z) by a function having the space z coordinate value Z as a variable. In other words, this function is a coordinate function for calculating the coordinate value of the calibration point 15 on the image.

In order to solve Equation 2, the least square method is preferred as in Equation 3, but there is no problem with other methods, and it can be appropriately selected if necessary.

Since the same can be applied to the image x _c coordinates and the image y _c coordinates of the B to D points, the calibration points A to D when the calibration board is moved by an arbitrary distance Z in the space z direction. The image coordinate values could be expressed as coordinate functions (P _i (Z), Q _i (Z)) (where i = {A, B, C, D}).

  Now that advance preparations have been completed, actual measurement will be described. The high-speed camera is used for shooting, and the shooting is continued at a minute interval t (seconds). The image immediately before the impact detected by the trigger device (hereinafter referred to as “impact image”) and the image one frame before (hereinafter “near” "Image") is recorded in the computer 21. At the same time, the head speed HS (m per second), which is the horizontal speed of the golf club head 53 at the moment of impact, is input to the computer by the head speed measuring device.

Next, in order to execute the two-dimensional DLT on each of the impact image and the near image, a function for converting the image coordinate value into the spatial coordinate value is obtained. Specifically, a method called two-dimensional DLT is used. This is based on the assumption that a function expressing the relationship between image coordinates (x _c , y _c ) and space coordinates (x, y) is given by Equation 4 and obtaining image coordinates (x _c , y _c ) from the image. Coordinates (x, y) are calculated. As advance preparation, the image coordinates of the calibration point whose spatial coordinates are known are obtained, and the function of Formula 4 is determined thereby.

  In this example, DLT for the impact image and DLT for the near image are performed separately. This is because these are DLTs on different planes. That is, the impact image is a DLT in the space xy plane in which the golf club head 53 is photographed immediately before the golf ball 51 and the space z coordinate value Z = 0, and the near image is the space z on the near side. This is because the DLT is in the space xy plane with the coordinate value Z = HS × t.

Image coordinate values of calibration points A to D in the space xy plane where the impact image is Z = 0, calibration points A to D in the space xy plane where Z = HS × t in which the front image is reflected The image coordinate values of the points can be calculated from the previously obtained coordinate functions (P _i (Z), Q _i (Z)). Since these are not image coordinate values obtained by actually capturing the calibration points, they are virtual calibration point coordinate values. On the other hand, the spatial coordinates of the calibration points A to D are not changed regardless of Z. When these are arranged, the coordinate values related to the calibration points A to D are as shown in Table 2.

A spatial coordinate value (x ₀ , y ₀ ) immediately before the impact of the marker 54 shown in the impact image is obtained using the function of Formula 4 determined using 1 and 3 in Table 2. Also, using the function of Equation 4 determined using 2 and 3 in Table 2, the spatial coordinate value (x ₋₁ , y ₋₁ ) immediately before the impact of the marker 54 shown in the near image is obtained, and further from the trouble image. The displacement (x ₀ −x ₋₁ , y ₀ −y ₋₁ , −HS × t) of the marker 54 up to the impact image is obtained. By dividing this by time, the velocity vector of the golf club head 53 immediately before the impact can be obtained, and the blow angle by atan (y ₀ -y _-1 / HS × t), atan (x ₀ -x _-1 / HS × t ) To obtain the head trajectory angle.

  The swing measurement system for golf and other exercise equipment of the present invention can be easily used as behavior and swing measurement of exercise equipment such as golf.

11: Camera 12: Head speed measuring device 13: Trigger device 14: Calibration board 15: Calibration point 21: Computer 22: Monitor 23: Mouse 24: Pointer 51: Golf ball 52: Golf club 53: Golf club head 54: Marker 71: Flying ball horizontal direction 72: Vertical direction 73: Horizontal left and right rear

Claims (3)

An image measuring device for swing behavior of exercise equipment,
A speed measurement unit that measures the speed v (m per second) of the main motion direction of the exercise tool;
A shooting unit that shoots a still image of the exercise tool t (seconds) before hitting from the back in the main direction of movement;
For a point on a still image captured by the imaging unit, a coordinate calculation unit that calculates two-dimensional coordinates in real space excluding the imaging direction,
The coordinate calculation unit obtains the image coordinates of the calibration point on the plane whose normal is the main movement direction at the hitting position, and the image coordinates when the calibration point is translated in the main movement direction. Calculate in advance the coordinate function of the calibration point with the translation distance as a variable,
In the measurement, the distance L from the shot position of the taken exercise tool is obtained as a product v × t of the speed and time of the main movement direction of the exercise tool to be measured,
Substituting this into the coordinate function as a variable, calculating the virtual calibration point coordinate value on the plane containing the taken exercise tool,
Using the virtual calibration point coordinate value, calculate the conversion function from image coordinates to spatial coordinates,
An image measuring device that uses this to obtain a two-dimensional coordinate value of an exercise tool. An image measuring device for golf swing behavior,
A speed measurement unit that measures the head speed HS (m / s) of the golf club;
A shooting unit that shoots a still image of the exercise equipment t (seconds) before impact from the rear in the flying ball horizontal direction;
For a point on a still image captured by the imaging unit, a coordinate calculation unit that calculates two-dimensional coordinates in real space excluding the imaging direction,
The coordinate calculation unit obtains the image coordinates of the calibration point on the plane normal to the flying ball horizontal direction at the impact position, and the image coordinates when the calibration point is translated in the flying ball horizontal direction. The coordinate function of the calibration point with this parallel movement distance as a variable is calculated in advance,
In the measurement, the distance L from the shot position of the photographed exercise equipment is obtained as the product HS × t of the head speed and time of the exercise equipment to be measured,
Substituting this into the coordinate function as a variable, calculating the virtual calibration point coordinate value on the plane containing the taken exercise tool,
Using the virtual calibration point coordinate value, calculate the conversion function from image coordinates to spatial coordinates,
An image measuring device that uses this to obtain a two-dimensional coordinate value of a golf club. Take a picture of the moment of impact or impact and measure the two-dimensional spatial coordinate value of the measurement target point.
Displacement in two directions excluding the main direction of movement or the horizontal direction of the flying ball due to the difference between this and the two-dimensional space coordinate value before t (seconds)
Furthermore, from the time t and the speed product t × v or t × HS, by calculating the displacement in the main movement direction or flying ball horizontal direction,
The measuring apparatus according to claim 1, wherein the displacement of the target point in t (seconds) immediately before the impact or impact is calculated three-dimensionally.

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