JPH079371B2 - Probe attitude control device - Google Patents

Description

The present invention relates to a device for controlling the posture of a probe of a three-dimensional shape measuring machine, an ultrasonic probe of an ultrasonic flaw detection scanner device, or the like.

B. Conventional Technique The conventional technique shown in FIGS. 11 and 12 showing the three-dimensional shape measuring machine will be described.

The probe 1 is held so as to be movable in the x-axis, y-axis, and z-axis directions, and the probe 1 can be manually or automatically kept in the same posture.
The tip of the is contacted with the surface 2 to be measured, and the respective x, y, z positions at that time are read. In general, the probe 1 has a shaft portion 1a and a spherical portion 1b at its tip as shown in FIG. 12, and when the probe 1 is brought into contact with the surface 2 to be measured, the position of the tip P of the spherical portion 1b is used as a measurement value to measure the The main body reads it. The above operation is repeated at a plurality of positions to measure the shape of the measured surface 2. The position of the center O of the spherical portion 1b may be read.

C. Problems to be Solved by the Invention However, when the surface 2 to be measured is inclined α degrees with respect to the horizontal plane HP as shown in FIG. 12, the spherical portion 1b of the probe 1 is contacted at the contact point Q. Contact the measurement surface 2. For this reason, an error occurs between the position of the contact point Q and the measurement position P by δx, δz.

Conventionally, several points are measured in the vicinity of the inclined surface, these points are interpolated to obtain an inclination angle α, deviations δx and δz are obtained based on the angle α, and the measured values are corrected. In this case, correction calculation is necessary, and even if it is performed by a computer, it does not result in real-time measurement, which is an obstacle to automation of shape measurement. It should be noted that the above description has been made in two dimensions, but essentially the same correction is necessary even in three dimensions, since the deviation δy is included.

Even if this type of probe 1 can move in the x-axis, y-axis, and z-axis, its posture is constant. Therefore, the inclination angle α of the measured surface 2 is
When the angle is 90 degrees or more, the tip spherical portion 1b of the probe 1 is placed on the surface 2
Cannot be contacted. In this case, it is necessary to change the posture of the object to be measured manually, which is an obstacle to automation.

The problems as described above are not limited to the three-dimensional shape measuring machine, and are similarly applied to various apparatuses for performing measurement by bringing the probe into contact with the surface to be measured, such as an ultrasonic flaw detection automatic scanner device having an ultrasonic probe. This is true.

An object of the present invention is to provide a probe attitude control device that controls the attitude of the probe and solves the above-mentioned problems.

D. Means for Solving the Problems The present invention will be described based on the claim correspondence diagram shown in FIG. 1. The probe attitude control device according to the present invention has a support means 101 having multiple degrees of freedom, such as an arm. A driving means 102 such as a DC motor for driving the supporting means 101, a probe 103 provided on the supporting means 101, and the probe 103 interposed between the supporting means 101 and the probe 103. Force detecting means 104 for detecting the force acting on the probe 103 when brought into contact with the probe 103, attitude detecting means 105 for detecting the attitude of the probe 103, and the detected probe 103.
Of the force detected by the force detection means 104, including the force component due to the own weight of the probe 103, the force detected by this force component is corrected, and the probe 103 is corrected based on the correction result. And a drive control means 106 for driving the drive means 102 so that the probe 103 abuts the measured surface perpendicularly to the measured surface.

E. Action When the probe 103 comes into contact with the surface to be measured, the force detection means 104 detects the drag force received by the probe 103. This drag force includes a force component due to the weight of the probe 103, and is corrected as follows. Attitude detection means 105 probe 1
The posture of 03 is detected. Based on this, the drive control means 106
Calculates the force component in each axial direction from the known weight of the probe and corrects the detected force, and calculates the tilt of the probe 103 with respect to the measured surface based on the correction result. Then, based on this inclination, the drive control means 106 controls the drive means 102 so that the probe 103 becomes perpendicular to the surface to be measured. As a result, the supporting means 101 is driven and the probe 103 becomes perpendicular to the surface to be measured.

F. Embodiment One embodiment of the present invention will be described with reference to FIGS.

FIG. 2 shows a schematic overall configuration of the probe attitude control device,
The probe 1 similar to the conventional one is provided at the tip of a robot 50 having 5 degrees of freedom via an axial force sensor 3, and each joint of the robot 50 is shown by a symbol defined by JIS. The robot 50 includes a rotation mechanism 52 (including the motor M1).
It is possible to turn with respect to the base 51. A rotating shaft 53 is connected to the rotating mechanism 52, and the rotating mechanism is connected to the tip of the rotating shaft 53.
The first arm 55 is rotatable by 54 (including the motor M2), and the second arm 57 is rotated by the second arm rotation mechanism 56 (including the motor M3) connected to the tip of the first arm 55.
Is rotatable, and a third arm rotation mechanism 58 (including the motor M4) connected to the tip of the second arm 57 makes it
The arm 59 of the can be rotated. A wrist 61 is rotatably provided at the tip of the third arm 59 via a wrist rotation mechanism 60 (including a motor M5). A multi-axis force sensor 3 shown in FIG. 3 is provided at the tip of the wrist 61, and the probe 1 is attached to the multi-axis force sensor 3. Multi-axis force sensor 3
Is for detecting each axial force of the x-axis, y-axis, and z-axis that acts on the probe 1 when the probe 1 is brought into contact with the surface to be measured.

That is, in FIG. 3, the multi-axis force sensor 3 includes a first ring 4, a second ring 5 facing the first ring 4, three flexible beams 6 connecting both rings 4 and 5, and a flexible beam. The tension / compression force detection gauge 7 is provided on the inner surface of the flexible beam 6, and the shear force detection gauge 8 is provided on the outer surface of the flexible beam 6. Then, the first ring 4 is connected to the wrist 61, the second ring 5 is connected to the probe 1, and when the flexible beam 6 bends in accordance with the force acting on the probe 1, a signal corresponding to the amount of strain from each gauge is generated. And the axial forces F _X , F _Y , and F _Z are known. Here, the axial forces F _X , F _Y and F _Z are component forces of the x-axis, y-axis and z-axis (the coordinate system is shown in FIG. 3) of the axial force F acting on the multi-axis force sensor 3. .

Referring again to FIG. 2, the rotation mechanism of each joint has a rotation angle sensor for detecting the rotation angle, for example, a rotary encoder R1.
~ R5 are provided, and the detected rotation angles θ _{1 to} θ ₅ are input to the control device 9. Further, the axial forces F _X , F _Y and F _Z detected by the axial force sensor 3 are also input to the drive control device 9. Control device 9
Drive signals i ₁ to motors M1 to M5 of the rotating mechanisms so that the probe 1 becomes vertical to the surface to be measured based on the calculation described later.
Supply i ₅ . In FIG. 2, only the signal lines D ₁ and D ₂ relating to the third arm rotation mechanism 58 and the signal line D ₃ of the axial force sensor 3 are shown connected to the control device 9, and many connections are omitted. ing.

As shown in FIG. 4, the control device 9 receives an analog signal from the axial force sensor 3 as a signal input section from the axial force sensor 3 and inputs an analog signal from the axial force sensor 3 to adjust its voltage level and a zero point, and an input analog signal. It has a multiplexer 9b that selectively outputs, and an A / D converter 9c that converts an analog signal from the multiplexer 9b into a digital signal and inputs the digital signal to the CPU 9d. Further, as a signal input unit from the rotary encoders R1 to R5, a counter circuit 9e that counts the serial pulse signals from the rotary encoders R1 to R5 and converts them into a parallel angle signal, and a signal from this counter circuit 9e is input to the CPU 9d. And an input interface 9f for outputting to. Further, as a signal control unit, a ROM 9g in which a processing procedure is stored in advance, a RAM 9h in which various numerical values, data, etc. are temporarily stored, each device is controlled in accordance with the processing procedure, and various signals are input based on an input signal. CPU9 that calculates and outputs the joint speed command signal comparing with the joint angle at that time
have d and. Furthermore, as an output unit, a D / A converter 9i that converts the digital joint speed command signal output from the CPU 9d into an analog signal, the joint speed command signal, and the joint calculated from the rotation angle signals from the rotary encoders R1 to R5. It has a servo driver 9j that controls the motors M1 to M5 so that their speeds match.

In the configuration of the above embodiment, the base 51, the arm 5
3, 55, 57, 59 and wrist 61 serve as support means, motors M1 to M5 serve as drive means, axial force sensor 3 serves as force detection means, and rotary encoders R1 to R5 and drive control device 9 serve as posture detection means. The drive control device 9 constitutes drive control means.

Next, the attitude control of the probe will be described with reference to FIG.

Now, it is assumed that the probe 1 is in contact with the surface to be measured. In step S1, the angles θ _{1 to} θ ₅ of each joint are detected by the output of the counter circuit 9e that counts the pulse signals from the rotary encoders R1 to R5. In step S2, the position and posture of the center point O of the spherical portion 1b of the probe 1 are determined based on these angles θ _{1 to} θ ₅ and the lengths l ₁ to l ₅ of each part of the robot 50 shown in FIG. Calculate In FIG. 2, l ₁ is the attachment point of the base 51, that is, the robot coordinate origin.
The distance from O ₁ to the first arm rotation mechanism 54, l ₂ is the first
And the distance between the second arm rotation mechanism 54 and 56, l
₃ is the distance between the second and third arm rotation mechanisms 56 and 58, and l ₄ is the third arm rotation mechanism 58 to the third arm.
The distance to reach the probe z axis along 59, l ₅ is
It is the distance from the center O of the probe ball portion 1b to the axis center of the third arm 59 along the wrist 61.

Here, the position of the probe 1 is a position vector from the origin O _{1 of the} robot coordinates to the center O of the probe sphere 1b: = (Ox, Oy, Oz) = f ₁ (θ ₁ ~ θ ₅ , l ₁ ~ l ₅ ) is required. The posture of the probe 1 is obtained by calculating the direction cosine vector (,,) as the inclination of the coordinate system of the axial force sensor 3 with respect to the robot coordinate system.

Direction cosine vector, And the angle formed by the probe x-axis with the x-axis of the robot coordinate system is θxx, the angle formed with the y-axis is θxy, and the angle formed with the z-axis is θxz, the direction cosine vector is Can be expressed as Similarly, the angles formed by the probe y-axis and z-axis with the x-axis, y-axis, and z-axis of the robot coordinate system are θy and θy, respectively.
Given x, θyy, θyz and θzx, θzy, θzz, the direction cosine vector, respectively, Can be expressed as For example, the direction cosine vector is
As shown in FIG. 6, when each axis of the coordinate system of the axial force sensor 3 is located at x ', y', z'with respect to the x-axis, y-axis, and z-axis of the robot coordinate system, z'-axis The projection of the direction cosine vector, which is the unit vector of the direction, on the x-axis, y-axis, and z-axis is hx, hy, and
It becomes hz.

When the position and orientation of the probe 1 are calculated in this way, the process proceeds to step S3, where the three axial force components F _X , F _Y , and F _Z (x, y, and z are the probe force components). Load the coordinate system).

FIG. 7 shows the drag force R acting on the probe 1 when the probe ball 1b is brought into contact with the surface 2 to be measured and the component forces R _X and R _Y (R
_Z is omitted), the force component W due to the probe's own weight and its respective components W _X , W _Z (W _Y is omitted), and the axial force components F _X , F _Y (F _Z is omitted) and the resultant force. A certain axial force F is shown. Axial force F
Is the reaction force of the force applied by the robot 50 to press the probe 1 against the surface to be measured 2 via the axial force sensor 3, and is the force measured by the axial force sensor 3. This axial force F
Is divided into a force component W due to the weight of the probe 1 and a drag force R that the probe 1 receives from the measured surface 2 as shown in FIG. Therefore, as can be seen from FIG. 7,
The axial force sensor 3 detects the component force F _X , F _Y , F _Z of the axial force, that is, F _X = R _X + W _X F _Y = R _Y + W _Y F _Z = R _Z + W _Z . Therefore, each component R _X , R _Y , R _Z of the drag force R is calculated by R _X = F _X −W _X R _Y = F _Y −W _Y (1) R _Z = F _Z −W _Z Is used as the axial force corrected for the probe's own weight for tilt calculation.

That is, in step S4, the axial force sensor x ′, y ′, z ′ axial direction component W _X , is calculated from the direction cosine vector (,,) obtained in step 2 and the known force component W due to the probe weight. W _Y , W _Z is calculated as W _X = f _X · W W _Y = g _Y · W W _Z = h _Z · W, and the corrected axial force (that is, drag force) R _X , R by the above formula (1). _{Find Y} and R _Z. Here, f _X , g _X , and h _X are the X-axis direction components of each direction cosine vector (,,).

Then, in step S5, the tilt (posture angle ξ, ψ) of the probe 1 with respect to the surface to be measured is calculated from the corrected axial forces R _X , R _Y , R _Z thus obtained.

8 (a) and 8 (b) show the probe ball portion 1b on the surface to be measured 2
FIG. 6 is a diagram illustrating axial forces R _X , R _Y , and R _Z when they are brought into contact with each other.

As indicated by the solid line J, when the z axis of the probe 1 is tilted with respect to the measured surface 2, the direction of the drag force R acting on the probe 1 does not match the probe z axis, and the component force R of the drag force R _X , R _Y ,
R _Z is detected. When the probe z-axis is perpendicular to the surface to be measured 2 as indicated by the alternate long and short dash line I, the direction of the drag force R acting on the probe 1 and the probe z-axis coincide. From this, the posture angles ξ and ψ of the probe 1 indicated by the alternate long and short dash line I with respect to the posture of the probe 1 indicated by the solid line J.
Is Required by.

Next, in step S6, it is determined whether the inclination angle ξ between the normal to the surface to be measured 2 and the probe z-axis is zero (whether the probe z-axis is perpendicular to the surface to be measured). If ξ = 0, the process ends, and if ξ ≠ 0, the process proceeds to step S7.

In step S7, using the posture angles ξ and ψ obtained in step S5, a target posture such that the probe z axis is perpendicular to the surface 2 to be measured is set as a target direction cosine (s, s, s), and s, s, s) = f ₃ (ξ, ψ (,,)).

Next, in step S8, the target direction cosine (s, s,
s) and the position vector of the center O of the probe sphere 1b obtained in step S2, the target angles θs _{1 to} θs ₅ of the joints in which the probe z axis is perpendicular to the measured surface 2 are (Θs _{1 to} θs ₅ ) = f ₄ ((s, s, s),). Then, in step S9, each joint has θs ₁
～Shitaesu ₅ and so as to motor driving command i ₁ ~i ₅ D / A converter 9i
Supply to the servo drive 9j from each motor M1
~ M5 is driven to control the attitude of the lobe z axis perpendicular to the surface 2 to be measured. At this time, the center point O of the probe ball portion 1b is set as the movement center of the robot, and as shown in FIG. 9, the probe 1 is kept in contact with the measured surface 2 at the contact point Q on the measured surface 2, The attitude of the probe 1 is controlled from the attitude I indicated by the alternate long and short dash line to the attitude indicated by the solid line J.

Using such a probe attitude control device in a three-dimensional shape measuring machine, the attitude of the probe sphere 1b is controlled so that the z axis is perpendicular to the surface 2 to be measured, and the point P of the sphere 1b is in contact with the surface 2 to be measured. In the state
By measuring each position of the x, y, z axis of the sphere 1b, it is possible to measure the shape and dimension without error in real time without performing the interpolation calculation as in the past, and continuous dimension measurement can be performed. Contributes to automation of measurement. In addition, the inclination angle α of the measured surface 2
Even if the angle is 90 degrees or more, the probe 1 can be brought into vertical contact with the surface 2 to be measured, and it is not necessary to manually shift the position of the object to be measured, which contributes to automation of measurement.

Further, when the present invention is applied to the ultrasonic flaw detection scanner device, the ultrasonic probe can be always held perpendicular to the surface to be inspected, and the inspection accuracy is improved, and the surface to be inspected has a complicated shape. However, automatic driving is possible.

The robot 50 described above has five degrees of freedom, but if the shape of the surface to be measured is limited and is known in advance, there is no particular need for five degrees of freedom. For example, as shown in FIG.
The present invention can be configured with a robot having three degrees of freedom as long as the solid has the same xz cross section along the y axis. Further, the driving means is not limited to the motor, and the axial force sensor may be of another type, and the shape of the probe is not limited to the embodiment.

G. Effect of the Invention According to the present invention, since the posture of the probe can be controlled to be perpendicular to the surface to be measured, automation of a three-dimensional shape measuring machine or an ultrasonic flaw detection scanner device equipped with this type of probe is possible. Is possible. Further, according to the present invention, since the attitude of the probe with respect to the surface to be measured is obtained in consideration of the weight of the probe in particular, there is an advantage that the probe can be controlled to be perpendicular to the surface to be measured with higher accuracy. If the present invention is applied to a three-dimensional shape measuring machine, it is possible to perform measurement without error.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram. 2 to 9 show an embodiment of the present invention.
The figure shows the overall schematic configuration, FIG. 3 is a perspective view showing an axial force sensor, FIG. 4 is a block diagram showing a control device, FIG. 5 is a flowchart showing a procedure of probe attitude control, and FIG. 6 is a direction cosine. FIG. 7 is a diagram for explaining the force component, drag force, and axial force due to the weight of the probe, and FIGS. 8A and 8B are explanatory diagrams of axial force detected by the axial force sensor.
FIG. 9 is a diagram for explaining the attitude control of the probe. FIG. 10 is a perspective view showing an example of a shape that can be measured with three degrees of freedom. 11 and 12 show a conventional example. FIG. 11 is a perspective view showing an example of a conventional three-dimensional shape measuring machine, and FIG. 12 is a detailed enlarged view of a probe. 1: Probe, 2: Surface to be measured 3: Axial force sensor, 9: Controller R1 to R5: Rotary encoder M1 to M5: Motor

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G01S 7/521

Claims (1)

[Claims] 1. A support means having multiple degrees of freedom, a drive means for driving the support means, a probe provided on the support means, and a probe interposed between the support means and the probe. Force detection means for detecting a force acting on the probe when brought into contact with the surface to be measured, attitude detection means for detecting the attitude of the probe, and the force detection based on the detected attitude of the probe. The force component due to the self-weight of the probe contained in the force detected by the means is obtained, the detected force is corrected by this force component, and the inclination of the probe with respect to the measured surface is corrected based on the correction result. And a drive control unit that drives the drive unit so that the probe comes into vertical contact with the surface to be measured.