JPH0352809B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method and apparatus for measuring the normal line of the surface of an object to be measured.

[Prior Art] Conventionally, there has been a three-dimensional measuring device that includes, for example, a touch probe that detects contact with an object to be measured and a positioning device that moves the touch probe. In this three-dimensional measuring device, a touch probe is brought into contact with an object to be measured using a positioning device, and the coordinates of a contact point in a predetermined coordinate system are detected from the moving distance of the positioning device at the time of contact. Therefore, in order to measure the normal direction at any measurement point of the object to be measured, it is necessary to measure and calculate the coordinates of at least three points near the measurement point to specify the surface of the object. However, errors during coordinate measurement and calculation errors are accumulated, making it impossible to perform highly accurate measurements.

[Summary of the invention]

The present invention has been made in order to solve the above-mentioned drawbacks, and it is possible to detect the relationship between the 3-component force detection probe and the measured object from the direction of the reaction force generated when the 3-component force detection probe is pressed against the measured object. The present invention provides a method and apparatus for measuring the normal direction of an object surface, which can measure the normal line at a contact point with high precision.

Figure 1 shows the state of the force generated when the 3-component force detection probe 1 contacts the object 2 to be measured, using an orthogonal three-dimensional coordinate system x, y, z with the 3-component force detection probe 1 as a reference.
It is an explanatory diagram shown above. 3 component force detection probe 1
While detecting the force acting on the three-component force detection probe 1, move the three-component force detection probe 1 in the z-axis direction and bring it into contact with the object to be measured 2.
When any of the axial forces x ₁ , y ₁ , or z ₁ reaches a predetermined value (e.g., a predetermined value at the center of the span that can be measured with high accuracy using a force detector such as a strain gauge), the force in the z-axis direction is If the normal direction of the surface at the contact point is not the z-axis direction, the resultant force F ₁ of the normal direction resistance N and the frictional force Fa acts on the 3-component force detection probe 1. 3 The force F ₁ acting on the component force detection probe 1 is such that the angle θ ₂ between the normal direction vector of the surface at the contact point and the x, y plane is 90° - θ ₂ > θ _f , 90° - θ ₂ ≦ θ _f varies depending on the case. Here, θ _f is a friction angle, and if the friction coefficient between the three-component force detection probe 1 and the object to be measured 2 is μ, tanθ _f =μ.
90° - θ ₂ > θ _f That is, when the angle between the surface of the object to be measured 2 and the x-y plane is larger than the friction angle θ _f , the component x ₁ in the direction of the force F ₁ acting on the 3-component force detection probe 1 ，
y ₁ and z ₁ are given by the following formula.

x ₁ =｜N→｜cosθ ₂・cosθ ₁ −μ｜N→
｜sinθ ₂・sosθ ₁ x ₁ =｜N→｜cosθ ₂・cosθ ₁ −μ｜N→
｜sinθ ₂・sosθ ₁ y ₁ =｜N→｜cosθ ₂・sinθ ₁ −μ｜N→｜sinθ ₂・sin
θ ₁ z ₁ = |N → | sin θ ₂ + μ | N → | sos θ ₂ On the other hand, 90° − θ ₂ ≦θ _f In other words, the angle between the surface of the object to be measured 2 and the x-y plane is the friction angle θ _f If equal or smaller, F ₁ acting on the 3-component force detection probe 1
The components x ₁ , y ₁ , z ₁ in each direction are given by the following equations.

x ₁ = 0 y ₁ = 0 z ₁ = |N→|sinθ ₂ −|N→| sosθ ₂ /tanθ ₂ Therefore, from the x and y direction components of the force F ₁ acting on the three-component force detection probe 1, , 90°−θ ₂ >θ _f , 90°−
The state of θ ₂ ≦θ _f can be clearly determined.

In the case of 90° - θ ₂ > θ _f , the 3-component force detection probe 1 is moved in the direction of θ ₁ given by tan θ ₁ = y ₁ /x ₁ , following the contact operation from the z-axis direction. , after stopping at a place where no force acts on the 3-component force detection probe 1, it moves in the opposite direction of θ ₁ , and the force N in the normal direction, the frictional force F, which acts on _{the 3} -component force detection probe 1, and the resultant force F → Any of the forces x _{2 ,} y ₂ , z ₂ in the x, y, and z axis directions of ), the movement will stop when it reaches this point. at this point
The components x ₂ , y ₂ , z ₂ in each direction of the force F→ ₂ acting on the three-component force detection probe 1 are given by the following equations.

x ₂ =｜N｜cosθ・cosθ ₁ +μ｜N｜sin
θ ₂・cosθ ₁ y ₂ = |N|cosθ ₂・cosθ ₁ +μ|N|sinθ ₂・sinθ ₁ z ₂ = |N|sinθ ₂ −μ|N|cosθ ₂ Obtained by the above two contact operations Force x ₁ , y ₁ ,
From z ₁ , x ₂ , y ₂ , z ₂ , the normal vector of the surface at the contact point l→=cosθ ₂・cosθ ₁ i→+cosθ ₂・sinθ ₁ j→+sin
The components of θ ₂ k→ in the x, y, and z directions are given by the following equations. Here, i→, j→, k→ indicate unit vectors in the x, y, and z directions, respectively.

cosθ ₂・cosθ ₁ = (x ₁ + y ₁ )/√(x ₁ + x ₂
) ² + (y ₁ + y ₂ ) ² + (z ₁ + z ₂ ) ² cosθ ₂・cosθ ₁ = (x ₁ + y ₁ )/√(x ₁ + x ₂
) ² + (y ₁ + y ₂ ) ² + (z ₁ + z ₂ ) ² cosθ ₂・sinθ ₁ = (y ₁ + y ₂ )/√(x ₁ + x ₂ ) ² + (y ₁ + y
₂ ) ² + (z ₁ + z ₂ ) ² cosθ ₂・cosθ ₁ = (x ₁ + y ₁ )/√(x ₁ + x ₂
) ² + (y ₁ + y ₂ ) ² + (z ₁ + z ₂ ) ² cosθ ₂・sinθ ₁ = (y ₁ + y ₂ )/√(x ₁ + x ₂ ) ² + (y ₁ + y
₂ ) ² + (z ₁ + z ₂ ) ² sinθ ₂ = (z ₁ + z ₂ )/√(x ₁ + x ₂ ) ² + (y ₁ + y ₂ ) ² + (
z ₁ + z ₂ ) ^2On the other hand, if 90°-θ ₂ ≦θ _f , move the 3-component force detection probe 1 around the contact point at a friction angle θ _f with respect to the z-axis.
Tilt at an angle θ ₀ greater than twice that of . If the orthogonal coordinate system based on the 3-component force detection probe 1 is x' ₁ , y', z' when the 3-component force detection probe 1 is tilted, then
After retracting the 3-component force detection probe 1 in the z'-axis direction, by performing two contact operations in the x', y', z' coordinate system in the same way as in the case of 90° - θ ₂ > θ _f . ,
The normal vector in the x', y', z' coordinate system is obtained, and by converting this normal vector to the x, y, z coordinate system, the normal vector in the x, y, z coordinate system is obtained. It will be done. For example, as shown in Figure 2, when the three-component force detection probe 1 is rotated by an angle θ ₀ around the y-axis direction, the coordinate system x', y', z is based on the three-component force detection probe 1. If the components of the normal direction vector obtained at ' are lx', ly', lz', the normal vector in the x, y, z coordinate system is transformed by the following equation.

l→=(cosθ ₀・lx′+sinθ ₀・lz′)i→
+ly′j→+(cosθ ₀ l′ _z −sinθ ₀・l′ _x ) k→ In this way, when the three-component force detection probe 1 is brought into contact with the object to be measured 2, the The normal direction of the surface of the object to be measured can be obtained from the force.

FIG. 3 is a perspective view showing the overall structure of the mechanism of the device for measuring the normal direction of the surface of an object according to the present invention. 2 is the object to be measured, 1 is a 3-component force detection probe that can detect forces in the x, y, and z directions, and 3 is the position of the 3-component force detection probe 1 attached to the tip in the x, y, and z directions and the y axis. It is a positioning device with 4 degrees of freedom that changes the posture of its surroundings.

FIG. 4 is a perspective view showing an embodiment of the three-component force detection probe 1. 4 is a base, 5 is a leaf spring whose both ends are fixed to the base 4, 6 is an elastic body fixed to the center of the leaf spring 4 and has two thin parts in each of the x and y directions, and 7 is a spherical tip. This is a stylus with a rear end fixed to an elastic body 6. 8,9,1
0 is a strain gauge, and two strain gauges 8 are attached to the leaf spring 5 symmetrically about the center. Further, two strain gauges 9 are attached to the elastic body 6 at a portion where it becomes thinner in the x direction, and two strain gauges 10 are attached at a portion where it becomes thinner in the y direction. A strain gauge 8 is attached to the leaf spring 5 and the elastic body 6 as described above.
~10, and strain gauge 8~1 as described below.
0 to the bridge circuit, the z-direction component of the force acting on the stylus 7 is transmitted to the strain gauge 8, the x-direction component to the strain gauge 9, and the y-direction component to the strain gauge 10.
Each can be detected independently.

FIG. 5 is a block diagram showing an example of a control device.
The control device 11 includes a three-component force detection circuit 12 that processes the output from the three-component force detection probe 1, a positioning device control circuit 13 that controls the positioning device 3, and a microcomputer 14. The three-component force effect circuit 12 includes strain gauge output signal processing circuits 15 to 17 for each of the strain gauges 8 to 10, respectively. For example, in the processing circuit 15, a bridge circuit composed of two strain gauges 8 and two fixed resistors 18 is applied by a strain amplifier 19,
The output signal of this pritzge is the strain amplifier 19
is amplified and output as a DC signal. The other strain gauge output signal processing circuits 16 and 17 similarly output DC signals. However, the bridge circuit in the strain gauge output signal processing circuit 15 is configured such that two strain gauges 8 face each other in order to extract only the force in the z direction acting on the leaf spring 5 to which the strain gauges 8 are attached. and strain gauge output signal processing circuit 1
The pritzge circuits 6 and 17 are constructed such that two strain gauges 9 and 10 are adjacent to each other in order to take out the forces in the x and y directions that act on the elastic body 6. The DC signals from the gauge output processing circuits 15 and 17 are input to a sample hold circuit 20, converted into digital signals by an A/D conversion circuit 22 via a multiplexer 21, and then taken into the microcomputer 14. The microcomputer 14 has a built-in CPU (central processor unit), ROM (read-only memory), RAM (read/write memory), I/O (input/output) interface, etc., and is used to determine the normal direction measuring device.・It constitutes a command/calculation means, and includes the following control command generation means, 3-component force value discrimination means, and normal direction calculation means.

The control command generating means executes a plurality of procedures for pressing and releasing the three-component force detection probe 1 against the surface of the object to be measured (pressing in the z-axis direction explained in the measurement method, pressing in the opposite direction of θ ₁ and in the opposite direction of θ ₁₎ . A control program containing commands for multiple procedures (such as moving in the forward direction) is built into the ROM, and a command control program for a procedure selected in consideration of the second determination result signal inputted below is stored in the ROM. The control commands for controlling the position and orientation of the three-component force detection probe 1 in multiple degrees of freedom (for example, four degrees of freedom) are read out and sequentially outputted to the positioning device control circuit 13, and the following first determination result is input. It has means for stopping the output of the control command in response to a signal.

The 3-component force value determining means is configured to: when the control command generating means is outputting a control command (for example, when pressing the 3-component force detection probe 1 in the z-axis direction);
Either one of the output values of the 3-component force detection circuit 12 has reached a predetermined value, or all of the output values have become zero (for example, if the 3-component force detection probe 1 is moved in the opposite direction of θ ₁ ) A first determination signal for determining whether this state has been reached during operation and stopping the output of the control command based on the determination result; In this case, the force components in the x-axis and y-axis directions output by the 3-component force detection circuit 12 are both zero (for example, when the 3-component force detection probe 1 explained in the measurement method is
Force in the x-axis direction after stopping movement pushing in the axial direction
x ₁ and the force y ₁ in the y-axis direction are both zero), and select a control command program based on the determination result (for example, tilt the 3-component force detection probe 1 and measure in a different coordinate system). ), and a means for outputting a second discrimination result signal for each of the above-mentioned control commands to the control command generating means.

The normal direction calculation means is a program that calculates the normal direction of the surface of the object to be measured that the 3-component force detection probe 1 comes into contact with (for example, a program containing calculation equations such as equations (1) to (5) above). is built into the ROM, and based on the program, the control command generation means calculates the force components in the x, y, and z axis directions output by the three-component force detection circuit 12 before and after starting and stopping the output of the control command. It has means for calculating the normal direction of the surface of the object to be measured.

The positioning device control circuit 13 controls the positioning devices 3 and 4 for changing the position and attitude of the 3-component force detection probe 1.
The microcomputer 14 includes actuator drive circuits 23 to 26, each of which drives actuators 27 to 30 in accordance with commands output from the microcomputer 14.

The operation of the device for measuring the normal direction of the object surface according to the present invention configured as described above is shown in FIGS. 6 and 7 a to f.
I will explain. Figure 6 shows the motion of the tip of the 3-component force detection probe 1, including the normal vector, when the angle formed between the surface in contact with the 3-component force detection probe 1 and the x-y plane is larger than the friction angle. - It is shown on a plane perpendicular to the y plane. Figure 7 shows the operation of the 3-component force detection probe 1 on the x-z plane when the angle formed between the surface in contact with the 3-component force detection probe 1 and the x-y plane is smaller than the friction angle. .

The three-component force detection probe 1 is moved in the z-axis direction by the positioning device 3, and the output from the three-component force detection probe 1 is sequentially input to the control device 11.
The 3-component force detection probe 1 comes into contact with the object to be measured 2, and the 3-component force detection probe 1
When any of the x, y, and z axis directions acting on the component force detection probe 1 exceeds a predetermined value, the z
Stop axial movement. Forces in the x, y, and z axis directions acting on the 3-component force detection probe 1 at this point
x ₁ , y ₁ , and z ₁ are stored in the microcomputer 14.

Next, if either x ₁ or y ₁ is not zero, the microcomputer 14 calculates θ ₁ given by tanθ ₁ = y ₁ /x ₁ , and the positioning device 3 moves the 3-component force detection probe 1 to θ _1. The probe is moved backward in the direction of directional force
Movement is stopped when any one of x ₂ , y ₂ , and z ₂ reaches a predetermined value or more. x ₁ , y ₁ , z ₁ , x ₂ , y ₂ ,
By calculating the normal direction from z ₂ using the microcomputer 14, the normal direction of the object surface can be obtained.

On the other hand, if x ₁ and y ₁ are both zero, the positioning device 3 rotates the three-component force detection probe 1 around the center of the sphere at the tip by an angle that is more than twice the friction angle.
The coordinate system based on the 3-component force detection probe 1 when the 3-component force detection probe 1 is rotated is x', y',
z', then the positioning device 3 moves the 3-component force detection probe 1 backward in the z' direction, stops when no force acts on the 3-component force detection probe 1, and then moves in the z' direction. Movement is stopped when any of the forces x ₃ , y ₃ , z ₃ acting on the component force detection probe exceeds a predetermined value, and x ₃ , y ₃ , z ₃ are stored in the microcomputer 14 . Next, the microcomputer 14 calculates θ ₁ given by tan θ ₁ = y ₃ /x ₃ , and the positioning device 3 moves the 3-component force detection probe 1 backward in the direction of θ ₁ to act on the 3-component force detection probe 1. After stopping the retreat when the applied force becomes zero, the probe is moved in the opposite direction again, and the forces in the x, y, and z axes directions acting on the three-component force detection probe 1 are x ₄ , y ₄ , z ₄
The movement is stopped when any one of the values exceeds a predetermined value. After calculating the normal direction in the x _' , y', z' coordinate system using the microcomputer 14 from x ₃ , y ₃ , z ₃ , x 4 , y ₄ , z ₄ , the three-component force detection probe 1 is tilted. By correcting the angle, the normal direction of the object surface can be obtained.

In the above explanation, the normal direction of the object surface is measured from the direction of the force generated when the 3-component force detection probe comes into contact with the object to be measured, but the normal direction measuring device of the object surface of the present invention It can also be used as a highly accurate three-dimensional object shape measuring device. In a typical three-dimensional object shape measuring device, the touch probe attached to the tip of the positioning device makes contact with the object to be measured, and the touch probe's x, y, and z coordinates are determined at multiple points. Since the shape was being measured, errors in interpolation between measurement points and errors in the position between the actual contact point and the measured contact point due to the size of the tip of the touch probe are unavoidable. However, if the normal direction at the contact point is known as in the present invention, the amount of information when interpolating between measurement points increases.
Interpolation accuracy can be increased. In addition, as shown in Figure 8, which shows a two-dimensional diagram of a slope forming an angle θ with the x-axis and a three-component force detection probe whose tip is a sphere with radius r, the contact position of the sphere can be determined from the normal direction. Therefore, the position of the contact point on the object to be measured can be accurately measured. Therefore, according to the present invention, it is possible to measure the shape of a three-dimensional object with high precision.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, the normal direction at the measurement point on the surface of the object to be measured can be directly obtained, and remarkable effects such as high precision measurement can be achieved. .

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the state of force when the 3-component force detection probe contacts the object surface, Figure 2 is an explanatory diagram showing the state of force when the 3-component force detection probe is tilted, and Figure 3 is FIG. 4 is a perspective view showing a mechanism for measuring the normal direction of an object surface; FIG. 4 is a perspective view showing a three-component force detection probe; FIG. 5 is a block diagram showing an example of a control circuit configuration; FIGS. Figures a, b, c, d,
e and f are operation explanatory diagrams of the 3-component force detection probe, No. 8
The figure is an explanatory diagram showing another embodiment of the present invention. 1... 3-component force detection probe, 2... object to be measured,
3...Positioning device, 11...Control device. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. x, which forms an orthogonal three-dimensional coordinate system of the acting force;
In the method of pressing a three-component force detection probe that can independently detect component forces in the y and z-axis directions against the surface of the object to be measured and measuring the normal direction of the surface of the object to be measured, the force acting on the three-component force detection probe is The three-component force detection probe is moved in the z-axis direction while measuring, and the three-component force detection probe contacts the object to be measured, and the x, which acts on the three-component force detection probe,
Movement is stopped when any of the forces x ₁ , y ₁ , z ₁ in the y and z axis directions reaches a predetermined value. If both x ₁ and y ₁ are not zero, tanθ ₁ =
It moves in the angle θ ₁ direction given by y ₁ /x ₁ until the force acting on the three-component force detection probe becomes zero, and then stops. Then move in the opposite direction of the angle θ ₁ ,
When the 3-component force detection probe comes into contact with the object to be measured and any of the forces x ₂ , y 2 , z ₂ in the x, y, and z axis directions acting on the 3-component force detection probe reaches the predetermined value, _the probe stops moving. Stop. x ₁ obtained by this operation,
From y ₁ , z ₁ and x ₂ , y ₂ , z ₂ , if the unit vectors in the x, y, and z axis directions are i, j, k, then the normal vector to the surface of the object to be measured is l=l _x i+l _y j+l _z k
As ^the _components in _the x, y, and _{z axes of}
( ₁ + ₂ ) ² + ( ₁ + ₂ ) ² , l _y = (y ₁ + y ₂ ) / √ ( ₁ + ₂ ) ² +
( ₁ + ₂ ) ² + ( ₁ + ₂ ) ² , l _z = (z ₁ + z ₂ ) / √ ( ₁ + ₂ ) ² +
( ₁ + ₂ ) ² + ( ₁ + ₂ ) ² , we get. If x ₁ and y ₁ are both zero, tilt the 3-component force detection probe at an angle that is more than twice the friction angle between the object to be measured and the 3-component force detection probe, and then adjust the normal line using the same operation as above. A method for measuring the normal direction of the surface of an object, characterized in that the normal direction of the surface of the object to be measured is obtained by obtaining the direction and correcting the tilt angle. 2 x, which forms the orthogonal three-dimensional coordinate system of the acting force,
A three-component force detection probe to which a strain gauge is attached so that the components in the y and z axis directions can be detected independently, and the x, y, and z components of the force acting by the output signals from the three component force detection probe. a three-component force detection circuit that calculates an axial component; a discrimination/command/calculation means; and a control command output from the discrimination/command/calculation means, which allows the position and orientation of the three-component force detection probe to be freely adjusted. and a positioning device that performs drive control at the same time. After the force detection probe is moved in the Z-axis direction and the three-component force detection probe comes into contact with the object to be measured, one of the three-component force values x ₁ , y ₁ , and z ₁ acting on the three-component force detection probe is set to a predetermined value. a first three-component force value discriminating means and a control command generating means for determining that the value has reached the value of , and outputting a control command to the positioning device to stop the movement in the z-axis direction based on the determination result; If the 3-component force values x ₁ and y ₁ are both negative, first detect the 3-component force while measuring the 3-component force values acting on the 3-component force detection probe using the output signals of the 3-component force detection circuit. probe
The probe is moved in the direction of the angle θ ₁ given by tanθ ₁ = y ₁ /x ₁ , and it is determined that all three component force values acting on the three component force detection probe have become zero. Stop movement in _one direction,
Next, the 3-component force detection probe is moved in the opposite direction of the angle θ ₁ , and the 3-component force detection probe is applied to the 3-component force detection probe.
It is determined whether any of the component force values x ₂ , y ₂ , or z ₂ has reached a predetermined value, and based on the determination result, a control command is issued to the positioning device to stop movement in the opposite direction of the angle θ ₁ . A second 3-component force value determining means and a control command generating means to output the 3-component force value output from the 3-component force detection circuit based on the positioning control of the 3-component force detection probe.
From x ₁ , y ₁ , z ₁ and x ₂ , y ₂ , z ₂ , the above x, y, z
If the unit vectors in the axial direction are i, j, k, then
The normal vector l = l _x i + l _y j + l _z k to the surface of the object to be measured, and the components in the x, y, and z axis directions are l _x = (x ₁ + x ₂ ) / √ ( ₁ + ₂ ) ² +
( ₁ + ₂ ) ² + ( ₁ + ₂ ) ² , l _y = (y ₁ + y ₂ ) / √ ( ₁ + ₂ ) ² +
( ₁ + ₂ ) ² + ( ₁ + ₂ ) ² , l _z = (z ₁ + z ₂ ) / √ ( ₁ + ₂ ) ² +
( ₁ + ₂ ) ² + ( ₁ + ₂ ) ² , a first normal direction calculating means for calculating the normal direction of the surface of the object to be measured; and the three component force values _x1 , y1 _. If both are zero, then
control command generating means for outputting a posture control command to a positioning device to tilt the three-component force detection probe at an angle of at least twice the friction angle between the object to be measured and the three-component force detection probe; later,
The normal direction is calculated using the normal direction calculation formula based on the positioning control of the three-component force detection probe similar to the above, and the normal direction of the surface of the object to be measured is calculated by correcting the tilted angle by the attitude control. The second to calculate
A device for measuring the normal direction of an object surface, comprising normal direction calculating means.