CN106989706B - A method and device for measuring and calculating the center of a high-precision circular suit - Google Patents

Abstract

The object of the present invention is to provide one kind in, the high-precision center of circle measuring method and device that large-scale circular workpiece is needed to operate the heart on large-size numerical control machine, measuring device includes pedestal mobile platform (1), limit switch (2), Y-axis mobile platform (3), X-axis mobile platform (4), mechanical handwheel (5), rotary shaft (6), servo motor (7), it measures axis (8), contact type measurement pops one's head in (9), controller 10, there are two freedom degrees for pedestal mobile platform (1), the X-axis mobile platform (4) of the X-direction of i.e. parallel mechanical pedestal, with the Y-axis mobile platform (3) of the Y direction of vertical mechanical pedestal, workpiece effectively can be moved to any position, measuring axis (8), there are two freedom degrees, direction is as pedestal mobile platform, to carry out the measurement of measuring point coordinate；Rotary shaft can move up and down, so that measuring probe can be deep to down on the inside of round piece；Controller (10) is used to control the motion profile of measuring probe, is mounted on upright post base surface, the intersection in pedestal mobile platform (1) and column, bus is connected to servo motor (7) along column.

Description

A method and device for measuring and calculating the center of a high-precision circular suit

technical field

The invention relates to a method and device for measuring and calculating the center of a high-precision circular suit, in particular to medium and large numerically controlled machine tools for assembling high-precision circular workpieces.

Background technique

In the field of numerical control, the centering method for two large circular workpieces is as follows: use an edge finder to touch any three points on the interior of one of the hollow circular workpieces, and store the mechanical coordinates of these three points. Into the numerical control system variables, since three points can determine a circle, the coordinates of the center of the circle are calculated through the functions integrated in the numerical control system. Although the above method can determine the coordinates of the center of the circle, in actual application, the error between the calculated coordinates of the center of the circle and the real coordinates is large. Large error; secondly, the massive data inside the system leads to a large memory occupation, which is difficult to meet the real-time calculation of the center of the circle; finally, there are few applications of using the edge finder to locate the center of the circle when assembling medium and large CNC machine tools. The positioning of the center of the circle by the device is more limited to the machining center.

Contents of the invention

In view of the above problems, the object of the present invention is to provide a method and device for measuring and calculating the center of a large circular workpiece with high precision that requires centering operations on medium and large CNC machine tools.

In order to achieve the above object, the present invention discloses the following technical solutions: a method for measuring and calculating the center of a large circular workpiece for centering operations of medium and large CNC machine tools, the inner diameter of the circular workpiece is r, and the coordinates of the center of the circular workpiece are measured The O(x,y) steps include:

1) Use the measuring probe to measure any two points P ₁ and P ₂ on the circular workpiece. The coordinates are (x ₁ , y ₁ ), (x ₂ , y ₂ );

2) Choose P ₁ as the starting point of the three-point method measurement, and ∠P1OP2 is θ ₁ . According to the three-point method, the three-point distribution follows an equilateral triangle distribution, that is, the angle between every two points and the center of the circle is 120°, then The angle between the first effective measuring point D ₁ and OP ₂ is θ2, then Establish a circle O ₁ that moves to the first measuring point D ₁ , OP ₂ is the tangent of circle O ₁ at P2, and the radius of circle O ₁ According to the coordinates of point P ₂ and the radius r _O1 of the orbiting circle, determine the orbiting track of the measuring probe is an arc within the circle O with O ₁ as the center and radius r _O1 Measuring probe along the arc Move until the measuring probe touches the edge of the circular workpiece and stops. The stopped position is point D1. At this time, the coordinates ( _{x D1} , y _D1 ) _of point D1 can be measured;

3) Establish a circumnavigation track circle O ₂ moving from D ₁ to the second effective measuring point D ₂ , the radius O _D1 of circle O is the tangent line of circle O ₂ at point D ₁ , and the three-point coordinates are distributed according to an equilateral triangle, Radius of circle _O2 According to the coordinates _of point D1 and the radius r _O2 of the orbiting circle _O2 , the orbiting track of the measuring probe can be determined is the arc trajectory in the circle O with O ₂ as the center and radius r _O2 Measuring probe along arc trajectory Move until the measuring probe touches the edge of the circular workpiece and stops. _The stopped position is point D2. At this time, the coordinates of point D2 (x _D2 , y _D2 ) can be measured _;

3) Establish a circumnavigation track circle O ₃ moving from D ₂ to the third effective measuring point D ₃ , the radius O _D2 of circle O is the tangent line of circle O ₃ at point D ₂ , and the three-point coordinates are distributed according to an equilateral triangle, Find the radius of the circle O ₃ According to the coordinates of point _D2 and the radius r _O3 of the orbiting circle _O3 , the orbiting track of the measuring probe can be determined is the arc trajectory in the circle O with O ₃ as the center and radius r _O3 Measuring probe along arc trajectory Move until the measuring probe touches the edge of the circular workpiece and stops. The stopped position is point _D3 . At this time, the coordinates of point _{D3 (x D3 ,} y _D3 ) can be measured;

4) Establish 6 parameter variables a, b, c, d, e, f: a=2×(x _D2 -x _D1 ), b=2×(y _D2 -y _D1 ), c=x _D2 ² +y _D2 ² -x _D1 ² -y _D1 ² , d=2×(x _D3 -x _D2 ), e=2×(y _D3 -y _D2 ), f=x _D3 ² +y _D3 ² -x _D2 ² -y _D2 ² , the coordinates O(x, y) of point O in the center of the circle are:

According to the calculation method mentioned above, the measurement probe may have three displacement directions of positive, negative and 0 in the X-axis direction of point P2, where " ₀ " means that neither the left nor the right can travel, and the detour direction of the measurement probe is determined by the displacement direction and θ ₂ positive and negative values to determine: the first case: when θ ₂ is a positive number or 0, and the displacement direction is positive or 0, the measuring probe rotates counterclockwise around O ₁ ; the second case: when θ ₂ is a positive number or 0, and the displacement direction is negative, the measuring probe rotates clockwise around O ₁ ; the third case: when θ ₂ is negative, and the displacement direction is positive or 0, the measuring probe rotates clockwise around O ₁ ; the fourth Situation: When θ ₂ is a negative number and the displacement direction is negative: the measuring probe rotates counterclockwise around O ₁ .

According to the calculation method mentioned above, the orbiting direction of the measuring probe at point D1: the _first case: when θ2 is a positive number or ₀ , the orbiting direction of the measuring probe is the same as the first orbiting direction; the second case: When θ ₂ is a negative number, the direction of the measuring probe's detour is opposite to that of the first detour.

A circle center measuring device for a circular set, including a base moving platform 1, a limit switch 2, a Y-axis moving platform 3, an X-axis moving platform 4, a mechanical hand wheel 5, a rotating shaft 6, a servo motor 7, a measuring shaft 8, and a contact Type measuring probe 9, controller 10, base mobile platform 1 has two degrees of freedom, namely the X-axis mobile platform 4 parallel to the X-axis direction of the mechanical base, and the Y-axis mobile platform 3 perpendicular to the Y-axis direction of the mechanical base, which can Effectively move the workpiece to any position, the measuring axis 8 has two degrees of freedom, and the direction is the same as that of the base moving platform to measure the coordinates of the measuring point; the rotating axis can move up and down, so that the measuring probe can go down to the inside of the circular workpiece ; The controller 10 is used to control the movement track of the measuring probe, installed on the surface of the column base, at the intersection of the base mobile platform 1 and the column, its bus is connected to the servo motor 7 along the column.

It is characterized in that: the measuring device uses the calculation method as claimed in claim 1 to measure the center of the circular suit.

The base mobile platform 1 is responsible for loading the circular hollow workpiece to be measured. When the measurement starts, the base mobile platform stops any movement. After the measurement is completed, it can be moved to the position of the set device for centering operation. The limit switch 2 is on the base, the column and the beam to control the stroke and limit protection of the motion mechanism. The column and the base are fixed, and the column is equipped with a rotating shaft 6. When taking out a large circular workpiece from the base mobile platform 1 or transporting it to the base mobile platform 1, the rotating shaft rotates to other positions to avoid friction. When measuring , the rotation axis must maintain a parallel relationship with the base, and the rotation axis itself can also move up and down on the column, so that the measuring probe can go down to the inside of the circular workpiece. The measuring axis 8 can move left and right on the beam to measure the coordinates of the circular workpiece in the X-axis direction. The contact measuring probe 9 is equipped with a module inside the measuring axis 8 and can move forward and backward to measure the Y-axis of the circular workpiece. direction coordinates. The servo motor 7 is installed in various motion mechanisms, such as base moving platform, rotating shaft and measuring shaft. The mechanical hand wheel 5 is installed on the measuring shaft 8 to tighten the measuring probe to prevent errors caused by contact vibration during the measurement process. Vibration occurs during the process.

The controller 10 includes an acquisition module, a logic control module, a motion control module, a coordinate registration module, a data calculation module, an alarm module, and an early warning module.

The signal acquisition module is responsible for collecting the signal of the measuring probe, filtering and amplifying the signal and transmitting it to the logic control module. The logic control module stores a large number of logic control algorithms and controls other modules in real time according to the functionality. The motion control module controls the measurement axis to move according to the coordinate information and motion execution program, and feeds back the current coordinate information in real time. The data calculation module will process and calculate the original data obtained after the measurement probe signal is collected, such as the angle θ ₂ between the first effective measuring point D ₁ and OP ₂ , the outer circle radius r _o1 , r _o2 , r _o3 , through the background After the calculation of the algorithm, the result data is passed to the coordinate register module. The coordinate storage module is used to store the result data calculated by the data calculation module and receive the coordinate information fed back by the motion control module, and transmit the coordinate information to the logic control module in real time. The alarm driving module drives the buzzer and LED indicator light immediately after receiving the signal from the hardware and software early warning module, and feeds back the alarm information to the logic control module.

When the measurement process starts, the logic control module first sends a signal to the motion control module, and the motion control module calls the measurement program after receiving the signal, so that the measurement axis descends to a random position inside the large circular workpiece, that is, the position of point P, and then the base moves The platform starts to move in the Y direction. When the measuring probe touches the inner wall, it immediately sends the signal to the signal acquisition module. The converted data information is sent to the numerical control calculation module and then stored in the coordinate storage module, and then fed back to the logic control module and motion control module, so that the coordinate data of point P ₁ can be obtained, and then the base platform moves in the -Y direction, when measuring After the probe touches the inner wall, the coordinate data of point P ₂ can be obtained in the same way. At this time, the data calculation module uses the corresponding algorithm in the background to calculate the angle θ ₂ between the first effective measuring point D ₁ and OP ₂ and the outer circle radius r _o1 , and store the data in the coordinate storage module; when planning the measurement trajectory of D ₁ point, D ₂ point, and D ₃ point, the logic control module calls the condition judgment signal and transmits it to the motion control module, and the motion control module sends a signal to make The mobile platform of the base makes a slight displacement in each of the _four directions of point P2. At this time, the measurement probe transmits the signal to the signal acquisition module, and then to the logic control module. The logic control module sends a signal after determining the measurement trajectory in the internal processor. , so that the motion control module invokes the motion program of the arc path, so that the base mobile platform performs a circle movement in the X and Y axis directions inside the circular workpiece. When the measuring probe touches the inner wall, the coordinate data _of point D can be obtained. At this time, the data calculation module calculates the outer circle radius r _o2 using a corresponding algorithm in the background, and stores the data in the coordinate storage module. Afterwards, the base mobile platform continues the above measurement process, and similarly, the coordinate data of D ₂ and D ₃ can be obtained sequentially. Finally, the data calculation module calculates the origin coordinate O(x,y) of the circular workpiece according to the coordinate data of D ₁ , D ₂ , and D ₃ points, and stores it in the coordinate storage module. After the measurement process is over, the logic control module sends an assembly signal to the motion control module, and the motion control module reads the coordinate data of the origin coordinate O(x,y) of the circular workpiece and performs differential compensation calculations in the X-axis and Y-axis directions, so that the base The mobile platform carries the circular workpiece and moves to the assembly position, and makes the center coordinate data of the two circular workpieces equal.

Due to the adoption of the above technical scheme, the present invention has the following advantages: the calculation method comprehensively considers the three-point method to obtain the optimal three-point distribution of the center of the circle and the minimum radius tangential positioning error, and can determine the travel direction and measurement deflection angle by using the measuring device , the measuring device adopts the method of contact measurement, and uses the numerical control system platform to plan the most efficient travel path and accurately locate the coordinates of the three points on the inner wall. Accurate and strict, the calculated coordinates of the center of the circle are compared and analyzed with the simulation results, and then applied to medium and large industrial circular equipment. High-precision circle center positioning kit requirements in various actual production and processing.

Description of drawings

Fig. 1 is the measurement part of the high-precision circular suit mechanical device;

In Fig. ₂ ; (a) is _a schematic diagram of point P1 and point P2 positioning; (b) is a schematic diagram of the positioning of the _first effective measuring point D1; (c) is to determine the different situations of the _first measuring point D1 detour trajectory Schematic diagram; (d) is a schematic diagram of the positioning of the _second effective measuring point D2; (e) is a schematic diagram of determining the different situations of the orbiting trajectory of the _second measuring point D2; (f) is a schematic diagram of the positioning of the _third effective measuring point D3 ; (g) is the ideal and actual diagram of the _third measuring point D3

In the figure: 1. Mechanical base, 2. Limit switch, 3. Y-axis moving platform, 4. X-axis moving platform, 5. Mechanical handwheel, 6. Rotating axis, 7. Servo motor, 8. Measuring axis, 9. Contact measuring probe, 10. Controller.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

The present invention includes a method for measuring and calculating the center of a high-precision circular suit and its mechanical measuring device. As shown in Figure 1, the mechanical measuring device mainly includes a base moving platform and a measuring shaft. The X-axis direction and the Y-axis direction perpendicular to the mechanical base can effectively move the workpiece to any position; the measurement axis has two degrees of freedom, and the direction is the same as that of the base moving platform to measure the center of the circle; the measuring probe can move up and down so that Make the measuring probe go down to the inside of the circular workpiece.

When the measuring probe enters the inside of the circular workpiece, it is recorded as point P, and the moving track of the measuring probe is observed from the perspective of looking down. The cutting motion controls the movement of the measuring probe (skip function means that the next program is executed immediately after the measuring axis touches the object, and the current coordinates are stored), and the coordinates of point P ₁ (x ₁ , y ₁ ) are obtained by moving downward first, and P ₁ is used as the The starting point (not the first point) measured by the three-point method, and then move up to obtain the coordinates of point P ₂ (x ₂ , y ₂ ), and get ∠P ₁ OP ₂ as θ ₁ , as shown in Figure a.

In the case that the inner diameter r of the circular workpiece is known, according to the three-point method, the three-point distribution of the coordinates of the center of the circle is distributed according to an equilateral triangle (that is, the angle between each two points and the center of the circle is 120°), and the center of the circle obtained is accurate. According to the principle of higher degree, according to the following formula, obtain θ ₂ (the angle between the line segment OD ₁ and OP ₂ between the first point D ₁ and the center point O of the three-point method).

After the measuring probe arrives at P2, it is necessary to establish _a detour circle O1 to move to the _first effective measuring point D1. _The reason why the measuring probe adopts a circular arc path instead of a straight line path for three-point measurement is that the sensor measuring head has an accurate measurement of the measuring point. If the measurement angle is different, there may be a slip error in the tangential direction, which will affect the measurement results. The establishment method of circle O ₁ is shown in figure b;

The radius OP ₂ of circle O is the tangent line of circle O ₁ at point P _2. Given the known θ ₂ and the radius r of circle O, calculate the radius r _O1 of circle O ₁ according to the following formula.

Given the coordinates of point P ₂ and the radius r _O1 of the orbiting circle, the orbiting track of the measuring probe can be determined The measurement track moves along the radial direction of the circle O (that is, the tangent direction of the outer circle O ₁ ), and the movement of the measurement probe is controlled by an arc cutting path with a skip function, so that the error of the coordinate value obtained in this measurement is the smallest. Next, determine the direction of travel of the measuring probe.

The measuring probe makes a small amount of displacement in the positive and negative directions of the X-axis at point P ₂ (the contact offset of the measuring probe). It is impossible to move left and right. Then judge the detour direction after the measuring probe according to the positive and negative values of θ ₂ (as shown in Figure c):

The first case: when θ ₂ is a positive number or 0, and the travelable direction is a positive number or 0: the measuring probe rotates counterclockwise around O ₁ .

The second case: when θ ₂ is a positive number or 0, and the travelable direction is a negative number: the measuring probe rotates clockwise around O ₁ .

The third case: when θ ₂ is a negative number, and the travelable direction is a positive number or 0: the measuring probe rotates clockwise around O ₁ .

The fourth case: when θ ₂ is a negative number and the travelable direction is a negative number: the measuring probe rotates counterclockwise around O ₁ .

When the measuring probe reaches the first effective measuring point D1, the coordinates (x _D1 , y _D1 ) of D ₁ are obtained, and then _a circle O ₂ is established to move from D ₁ to the second effective measuring point D ₂ , the circle The way _O2 is established is shown in Figure d.

The radius OD ₁ of the circle O is the tangent of the circle O ₂ at the point D _1. In order to ensure the minimum measurement error, the three-point coordinates are distributed according to the equilateral triangle, and the following needs to be satisfied:

Calculate the radius r _O2 of the circle O ₂ according to the following formula.

Knowing the coordinates _of point D1 and the radius r _O2 of the orbiting circle _O2 , the orbiting track of the measuring probe can be determined The movement of the measuring probe is controlled by the arc cutting path with skip function, and the following is to determine the direction of the measuring probe’s detour at point D1 ₍ as shown in Figure e):

The first case: when θ ₂ is a positive number or 0, the measuring probe's orbiting direction is the same as the first orbiting direction.

The second case: when θ ₂ is a negative number, the direction of the measuring probe's detour is opposite to that of the first detour.

When the measuring probe reaches the _second effective measuring point D2, the coordinates of point D2 ₍ x _D2 , y _D2 ) are obtained, and then a circle O ₃ is established to move from D2 to the _third effective measuring point _D3 , the circle The way O ₃ is established is shown in Figure f.

The orbiting trajectory circle O ₃ is established in the same way as the circle O ₂ , the radius OD ₂ of the circle O is the tangent of the circle O ₃ at the point D ₂ , and satisfies:

Find the radius r _O3 of the circle O ₃ according to the following formula.

Knowing the coordinates of point D ₂ and the radius r _O3 of the orbiting circle O ₃ , the orbiting track D ₂ D ₃ of the measuring probe can be determined, and the movement of the measuring probe is controlled by the arc cutting path with skip function, and the orbiting direction is the same as The second rounding direction is the same. When the measuring probe reaches the third effective measuring point _D3 , the coordinates of point _{D3 (x D3 , y D3} ) are obtained. Point _D3 coincides with point P1 in theory, but it is possible in practice There is a deviation, as shown in figure g, if there is a deviation, find the deviation value of point P ₁ and point D ₃ .

Δx _P ＝|x _P1 -x _D3 |

Δy _P ＝|y _P1 -y _D3 |

If both Δx _P and Δy _P meet the deviation accuracy requirements, even if point D ₃ does not coincide with point P ₁ , it is still the third valid measuring point. According to the above mathematical model, the coordinates of the three points D ₁ (x _D1 , y _D1 ), D ₂ (x _D2 , y _D2 ), D ₃ (x _D3 , y _D3 ) are obtained, and then the coordinates of point O in the center of the circle are calculated:

First establish six parameter variables a, b, c, d, e, f:

a=2×(x _D2 -x _D1 )

b=2×(y _D2 -y _D1 )

c＝x _D2 ² +y _D2 ² -x _D1 ² -y _D1 ²

d=2×(x _D3 -x _D2 )

e=2×(y _D3 -y _D2 )

f＝x _D3 ² +y _D3 ² -x _D2 ² -y _D2 ²

Then calculate the coordinates O(x, y) of the center O point:

The circle center calculation method has the function of self-adaptive path-seeking control, which can automatically optimize the processing process, so as to achieve the purpose of improving production efficiency and improving the quality of the processed surface. The machine tool operator only needs to provide the basic parameter information of the raw material, and the device system can intelligently select Using the optimal positioning path to measure and calculate the coordinates of the origin, it is widely used in the packaging of circular workpieces of different specifications.

Claims (4)

1. a kind of center of circle measuring method of round suit, step include:

1) coordinate of any two points P1, P2 loaded onto using measuring probe measuring unit is respectively (x₁, y₁), (x₂, y₂), calculate set The center of circle of dress is point O (x, y), it is known that suit internal diameter is r；2) selection is with P₁As the starting point of line-of-sight course measurement, ∠ P₁OP₂For θ₁, according to line-of-sight course, 3 points of distributions are distributed according to equilateral triangle, i.e., every two point and the angle in the center of circle are 120 °, first Effective measuring point D₁With OP₂Between angle be θ₂, then Foundation is moved to first measuring point D₁Detour locus circle O₁, OP₂It is Circle O₁In P₂Tangent line, circle O₁RadiusAccording to P₂The radius r of point coordinate and the circle that detours_O1, can determine survey Measure the detour track of probeThis track is moved along circle O radial direction, i.e. outer circle O₁Tangential direction, when measuring probe arrives Up to first effective measuring point D₁After can measure D₁Coordinate (the x of point_D1, y_D1)；

2) it establishes from D₁It is moved to second effective measuring point D₂Detour locus circle O₂, the radius OD of circle O₁It is round O₂In D₁Point is cut Line is distributed 3 coordinates according to equilateral triangle,Circle O₂RadiusAccording to D₁Point coordinate and the circle O that detours₂Radius r_O2, can determine the detour track of measuring probeThis Track is moved along circle O radial direction, i.e. outer circle O₂Tangential direction, when measuring probe reach second effective measuring point D₂After can Measure D₂Coordinate (the x of point_D2, y_D2)；

3) it establishes from D₂It is moved to third effectively measuring point D₃Detour locus circle O₃, the radius OD of circle O₂It is round O₃In D₂Point is cut Line is distributed 3 coordinates according to equilateral triangle,Find out the radius of round O3According to D₂Point coordinate and the circle O that detours₃Radius r_O3, can determine the detour track of measuring probeThis Track is moved along circle O radial direction, i.e. outer circle O₃Tangential direction, when measuring probe reaches third effectively measuring point D₃After can Measure D₃Coordinate (the x of point_D3, y_D3)；

4) 6 parametric variable a, b, c, d, e, f:a=2 × (x are established_D2-x_D1), b=2 × (y_D2-y_D1), c=x_D2 ²+y_D2 ²-x_D1 ²- y_D1 ², d=2 × (x_D3-x_D2), e=2 × (y_D3-y_D2), f=x_D3 ²+y_D3 ²-x_D2 ²-y_D2 ², the coordinate O (x, y) of center of circle O point:

2. measuring method as described in claim 1, measuring probe is in P₂Point does positive and negative two direction of X-axis and does micro displacement (survey Measure the contact offset of probe), the direction that can be advanced is demarcated by X-axis, has positive and negative and 0 three kinds of situations, wherein " 0 " is that left and right is equal It cannot advance.Further according to θ₂Positive and negative values judge the direction of circling after measuring probe: the first situation: work as θ₂For positive number or 0, And can direction of travel be positive number or 0: measuring probe is around O₁Rotation counterclockwise；Second situation: work as θ₂For positive number or 0, and can advance Direction is negative: measuring probe is around O₁It rotates clockwise；The third situation: work as θ₂For negative, and can direction of travel be positive number or 0: Measuring probe is around O₁It rotates clockwise；4th kind of situation: work as θ₂For negative, and can direction of travel be negative: measuring probe is around O₁It is inverse Hour hands rotation.

3. measuring method as claimed in claim 1 or 2, measuring probe is in D₁The direction of circling of point: the first situation: work as θ₂For Positive number or 0, measuring probe direction of circling are identical as first time direction of circling；Second situation: work as θ₂For negative, measuring probe around Line direction is opposite with first time direction of circling.

4. a kind of center of circle measuring device of round suit, includes pedestal mobile platform (1), limit switch (2), Y-axis mobile platform (3), X-axis mobile platform (4), mechanical handwheel (5), rotary shaft (6), servo motor (7) measure axis (8), contact type measurement probe (9), there are two freedom degree, i.e., the X-axis mobile platforms (4) of the X-direction of parallel mechanical pedestal for pedestal mobile platform (1), and hang down Workpiece effectively can be moved to any position, measured axis (8) by the Y-axis mobile platform (3) of the Y direction of straight mechanical pedestal There are two freedom degrees, and direction is as pedestal mobile platform, to carry out center of circle measurement；Measuring probe can move up and down, so as to So that being deep under measuring probe on the inside of round piece, it is characterised in that: the measuring device uses measuring and calculating as described in claim 1 Method measures the center of circle of round suit.