JP2009125215A - Roller type pitching machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a robust roller-type pitching machine hardly affected by the variation in the posture of the seam of balls fed into the machine and the position of the posture. <P>SOLUTION: The pitching machine includes three rollers around in the shooting direction of the ball. Three rollers have rotational drive units for controlling their rotation, and a holding interval control unit which controls a distance between the ball center to be held and shot by the three rollers and the roller surface. The surface of the roller is formed in a convex shape. The radius of curvature of the surface of the convex roller is preferably in the range of R=40-120 mm. Preferably, the circumference part of the roller is made of elastic rubber material, and Young's modulus of the elastic rubber material is in the range of E=30-80 MPa. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a roller-type pitching machine that launches a ball, and particularly relates to a roller structure that is effective in improving pitching accuracy.

Currently, arm type and roller type are commercially available as pitching machines for baseball.
The arm type can change the speed, but it is difficult to throw a changing ball such as a curve. The two-roller type with two rotating rollers can also throw a changing ball, but it is difficult to change it instantly. .
In addition, it is extremely difficult for any type to throw any ball into the desired course.
Therefore, the inventors have devised a three-roller pitching machine using three rollers, and the batter wants a ball with an arbitrary speed or changing ball by using a neural network (NN) as a control method for each roller. Researching and developing pitching machines that can be thrown on courses.
However, there are several problems, including cost, in order to put the developed machine into practical use.
It is particularly important to have a high pitching accuracy that never throws a dead ball to the batter.
On the other hand, hardballs used in professional baseball have special seams.
In a roller-type pitching machine that uses the friction force between the ball and the roller, the rotation and projection angle of the ball slightly change depending on the position and orientation of the seam that contacts the roller even under the same throwing conditions. It is generally said that it gets worse.
Even in the preliminary experiment of the present inventor, it has been experimentally found that the rotation and the projection angle of the ball slightly change depending on the manner in which the seam of the hard ball contacts the roller, and as a result, the pitching accuracy is lowered. .
Therefore, a throwing simulation analysis of a three-roller pitching machine was performed using the finite element method (FEM), and the dynamic behavior of the ball such as the speed of the ball and the rotation speed (spin) during the pitching was clarified and put into the machine. We investigated how the pitching accuracy changes depending on the ball posture.
In addition, as a result of examining the optimum roller shape and material from the analysis results, the present invention has been achieved.

Japanese Patent No. 3936539 JP 2006-61231 A

  An object of the present invention is to provide a robust pitching machine that is not easily affected by a change in the position of a seam posture of a ball thrown into the roller-type pitching machine.

The pitching machine according to the present invention is a pitching machine in which three rollers are arranged around the ball firing direction, and the three rollers are sandwiched and fired by the rotation driving device that controls the respective rotations and the three rollers. It has a clamping interval control device for controlling the distance between the center of the ball and the roller surface, and the surface of the roller is formed in a convex curve shape.
Here, the curvature radius of the convex curved surface shape of the surface of the roller is preferably in the range of 40 to 120 mm, and the roller has an outer peripheral portion made of a rubber elastic material, and the rubber elastic material has a Young's modulus of 30 to 30 mm. The range is preferably 80 MPa.

In the present invention, the surface of the roller of the three-roller pitching machine has a convex curved surface, so that the pitching accuracy is improved regardless of whether the ball is thrown in two or four seams.
In particular, when the Young's modulus of the rubber material on the outer periphery of the roller is set to be slightly soft by setting it to 30 to 80 MPa and the radius of curvature of the roller surface is set to a range of R = 40 to 120 mm, the pitching accuracy is further improved.
This is presumed to be caused by firing with the rotational friction force while holding the ball so that the convex surface of the soft roller is recessed.

Next, the analysis process leading to the present invention will be described.
The inventors conducted FEM simulation analysis using the three-roller pitching that has been developed so far.
First, an outline of the machine used for analysis will be described with reference to FIG.
The balls are fired using frictional force with rubber rollers (1, 2, 3) installed at intervals of 120 ° around the firing position.
A motor (M1, M2, M3) is installed on each roller, and a mechanism (M4, M5) that changes the elevation angle θ and declination φ of the entire machine is added to the lower part of the machine. It can be controlled.
In addition, NN (neural network) is used for the control method of each roller, and various parameters such as the number of rotations of the roller are determined.
Here, the specific contents of NN can incorporate the contents of Patent Documents 1 and 2.
As a result, this machine can accurately throw a ball of any ball speed and changing ball (ball type) on a wide range of courses.
Also, from the results of a pitching experiment conducted in a room, what is generally thrown in a state where the seam appears twice during one rotation of the ball, called a 2 seam, is randomly called 4 seams (a state where the seam appears 4 times). It is also known that the pitch accuracy is high with less variation in the distance between the target point and the destination point compared to (states other than 2 seams and 4 seams).

For the purpose of confirming the result obtained from the experiment and examining the improvement of pitching accuracy, the dynamic behavior simulation of the ball thrown by the three-roller pitching machine was performed using the general-purpose dynamic finite element analysis software ANSYS / LS-DYNA. went.
FIG. 2 shows a finite element model of a roller portion and a ball of a three-roller pitching machine.
In this analysis, the aluminum flange portion (outer diameter φ280 mm) is a rigid body because the rigidity and deformation are minute compared to other materials, and the ball is a viscoelastic body considering its dynamic characteristics.
The analysis conditions are as follows: the ball posture is 2 seam and 4 seam as shown in FIG. 3, and the contact friction coefficient μ of the ball and urethane rubber roller (outer diameter φ320 mm, thickness 20 mm, roller width 55 mm) is 0.5. The time was 0.1 seconds, and the ball was given an initial translation velocity V ₀ of 1 m / s and an initial angular velocity ω ₀ of 28.56 rad / s.
This initial speed was calculated based on the state of the ball actually put into the pitching machine.
For comparison, a seamless ball (true sphere model) was also analyzed.
The definition of the ball projection angle at that time is shown in FIG. 4, and the analysis conditions of the rotational speed N1, the rotational speed N2 of the roller 2, and the rotational speed N3 of the roller 3 are shown in FIG.

As indices for grasping the behavior of the pitched ball, the average ball speed V, the number of rotations ω, the launch elevation angle θ, and the launch deflection angle φ were calculated from the analysis values.
From the analysis results, it was confirmed that the effect of the seam is smaller in the two seams than in the four seams at the elevation angle θ and the deflection angle φ.
Next, in order to stabilize the pitching accuracy regardless of the initial posture of the ball, the surface shape of the roller was examined.
As shown in FIG. 6, the created roller model has two patterns: a convex roller having a raised surface and a concave roller having a concave shape.
The curvature radii R are both 100 mm, and the distance from the ball center to the roller surface width center is constant.
The roller used so far is called a flat roller.
As a result of comparing the firing angles, it was found that the effect of the difference in the initial posture of the ball (the presence or absence of seams) was great.
As shown in FIG. 7, the elevation angle θ has the smallest difference between the two seams of the flat roller and the true spherical model (seamless), and the deflection angle φ is the difference between the two seams of the convex roller and the true spherical model as shown in FIG. The difference is the smallest.
A small difference from the value of the true ball model is considered to have a small pitch effect and a good pitch accuracy.
FIG. 9 shows the difference (Δθ, Δφ) between 2 seams and 4 seams for each ball type. In both straight and curved cases, the convex roller shape is higher in the elevation angle θ and the declination angle φ than the concave roller shape. In both cases, the difference (Δθ, Δφ) is small.
In particular, the value of the declination is an important factor in terms of pitching accuracy because it directly affects the dead ball, so it can be said that the convex roller tends to be better than the other rollers.

From the simulation results, the convex roller can be expected to stabilize the firing angle, so we decided to optimize the convex roller.
Design conditions were such that the distance (center distance) r from the ball center to the roller surface width center and the radius of curvature R of the roller surface shown in FIG. 6 were variable dimensions, and the Young's modulus E of the rubber part of the roller was also changed.
The dimensions used so far are r = 25.1 mm, R = 100 mm, and the Young's modulus is E = 100 MPa.
In order to perform the optimum design, we decided to use the launch angle difference for each initial posture as an evaluation of the roller optimum for the design variable.
First, this estimation formula is derived by the response surface method.
The target formulas were devised as two formulas: Formula (1) for declination difference considered to be the most important in pitching accuracy and Formula (2) considering the effects of both elevation angle and declination differences.
The smaller these values, the smaller the firing angle difference between the initial postures, indicating that the effect of the seam is small.
Here, the subscripts 2 and 4 of θ and φ represent the initial posture of the ball (2 corresponds to 2 seams and 4 corresponds to 4 seams).
η is a term for removing from the optimal solution the case where the ball's rotation number (spin) is extremely small and it is considered that the ball is not thrown with the expected ball type, and was determined as follows.
ω ₂ ≧ 400 min ⁻¹ and ω ₄ ≧ 400 min ⁻¹ → η = 0,
ω ₂ <400 min ⁻¹ or ω ₄ <400 min ⁻¹ → η = 1
Further, α in the equation (2) is a weighting coefficient for equalizing the influence of the deviation angle difference term and the elevation angle difference term, and is determined by the ratio of the average values of the selected design points.
Pitch type is curve ^{_{(N 1 = 1325min -1, N}} 2 = 1750 min -1, N 3 = 1425min -1) was.
This time, the design variables are discretized into three levels as shown in FIG. 10, and an experimental design called all factor design is used to obtain a response surface by executing all the cases.
The response surface was constructed using a response surface creation tool RSMaker for Excel and approximated by a cubic polynomial.
FIG. 11 shows an R-r curved surface diagram when Young's modulus E = 50 MPa.
From this result, it was estimated that the radius of curvature of the roller surface is between R = 60 and 120 mm, and the Young's modulus has an optimum value near E = 50 MPa.
Thus, R = 100 mm, and r and E were analyzed under the analysis conditions shown in FIG.
The result is shown in FIG.
FIG. 14 shows the relationship between the roller center distance r and the pitching accuracy at Young's modulus E = 50, 60, 100 MPa.
From the above results, the Young's modulus of the roller is set to E = 40 to 60 MPa, the curvature of the roller surface is set to a level of R = 80 to 120 mm, and the distance r between the center of the ball and the center of the roller is suitable for the clamping interval control device. It has been clarified that if the ball posture is changed by 2 seams, 4 seams, or randomly, the pitching accuracy will be improved by adjusting it.
In the case of the ball diameter of 70 mm this time, r = 25.4 mm was the optimum point.
FIG. 15 shows a pitching analysis continuous image viewed from the launch port, and FIG. 16 shows a pitching analysis continuous image viewed from the side surface direction.

The schematic diagram of the structure of the pitching machine which concerns on this invention is shown. An analysis model is shown. An example of 2 seams and 4 seams in the posture to be thrown into the ball slot is shown. The definition of the ball projection angle in this analysis is shown. Indicates the ball throwing conditions. An analysis model of the roller surface shape is shown. The elevation angle θ comparison with the true sphere model is shown. A declination φ comparison with the true sphere model is shown. The difference by the ball type is shown. The primary analysis conditions are shown. An Rr curved surface view is shown. The analysis conditions near the optimal point are shown. An Er curved view is shown. The relationship between the roller center distance and pitching accuracy is shown. The analysis continuous image seen from the launch port is shown. The analysis continuous image seen from the side is shown.

Claims (3)

A pitching machine in which three rollers are arranged around the ball firing direction,
The three rollers have a rotation driving device that controls the rotation of each roller, and a pinching interval control device that controls the distance between the center of the ball that is pinched and fired by the three rollers and the roller surface,
A pitching machine characterized in that the surface of the roller is formed in a convex curved surface shape.   2. The pitching machine according to claim 1, wherein a radius of curvature of the convex curved surface shape of the roller surface is in a range of R = 40 to 120 mm.   3. The pitching machine according to claim 1, wherein the roller has an outer peripheral portion made of a rubber elastic material, and a Young's modulus of the rubber elastic material is in a range of E = 30 to 80 MPa.