JPS63135813A - Apparatus for controlling posture of probe - Google Patents

Abstract

PURPOSE:To perform the error-free measurement with a three-dimensional shape measuring device, by providing a driving control means for driving a device means so that a probe vertically contacts a surface to be measured. CONSTITUTION:Support means 51-61 each composed, for example, of an arm having a multiple degree of freedom, drive means M1-M5 composed, for example, of DC motors driving said support means, the probe 1 provided to the means 61, an axial tension sensor 3 for detecting the force acting on the probe 1 when the probe 1 contacts a surface to be measured and a driving control means 9 operating the inclination of the probe 1 to the surface to be measured on the basis of the force detected by the sensor 3 to drive the means M1-M5 so as to vertically contact the probe 1 with the surface to be measured are provided. In this case, since the force detected is different according to the inclination of the probe 1 to the surface to be measured, the detection value of the sensor 3 is inputted to the means 9 to calculate the inclination of the probe 1 to the surface to be measured. Then, the means M1-M5 are driven so that said inclination becomes zero.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application 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, and the like.

B. Prior Art The prior art will be explained with reference to FIGS. 9 and 10 showing a three-dimensional shape measuring machine.

The probe 1 is held movably in the X-axis,
Read each position of lZ. Generally, as shown in FIG. 10, the probe 1 has a shaft portion 1a and a spherical portion 1b at its tip, and when the probe 1 is brought into contact with the surface to be measured 2, the position of the tip P of the spherical portion 1b is taken as a measurement value by a measuring device. The main body can read it. The above operation is repeated at a plurality of positions to measure the shape of the surface to be measured 2. Note that the position of the center 0 of the spherical portion 1b may be read.

Problems to be solved by the C0 invention However, the surface to be measured 2 is a horizontal plane HP as shown in FIG.
If the spherical part 1b of the probe 1 is tilted by α degrees with respect to
comes into contact with the surface to be measured 2 at a contact point Q. Therefore, a deviation occurs between the position of the contact point Q and the measurement position P by δX and δ2, resulting in an error.

Conventionally, the number of points in the vicinity of the inclined surface is measured, those points are interpolated to obtain the inclination angle α, and based on this angle α, the deviations δX and δ2 are calculated and the measured values are corrected. in this case,
A correction calculation is required, and even if this is performed by a computer, real-time measurement will not be possible, which will be an obstacle to automating shape measurement. Note that although the above description has been made in two dimensions, essentially the same correction is required in three dimensions as well, except that the deviation δy is included.

Although this type of probe 1 can move in the X-axis, y-axis, and Z-axis, its posture remains constant. Therefore, when the inclination angle α of the surface to be measured 2 becomes 90 degrees or more, the tip spherical portion 1b of the probe 1 cannot come into contact with the surface to be measured 2.

In this case, it is necessary to perform measurements by manually changing the posture of the object to be measured, which poses an obstacle to automation.

The above problems are not limited to three-dimensional shape measuring machines, but also apply to various devices that perform measurements by bringing the probe into contact with the surface to be measured, such as automatic ultrasonic flaw detection scanners equipped with ultrasonic probes. That applies.

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

The present invention will be explained based on FIG. 1 showing an embodiment of means for solving problem D6.
A probe attitude control device according to the present invention is:

Supporting means 51 consisting of, for example, an arm or the like having multiple degrees of freedom
~61, driving means M1 to M5 such as DC motors for driving these supporting means, the probe 1 provided on the supporting means 61, and the probe 1 when brought into contact with the surface to be measured. A force sensor 3 detects the acting force, and the inclination ξ (Fig. 6) of the probe 1 with respect to the surface to be measured is calculated based on the force detected by the force sensor 3, and the probe 1 is perpendicular to the surface to be measured. The driving means M1 to M are in contact with each other.
and a drive control means 9 for driving the motor 5.

When the E0 effect probe 1 comes into contact with the surface to be measured, the force sensor 3 detects the force acting on the probe 1. Since the force detected differs depending on the inclination of the probe 1 and the surface to be measured, the force sensor 3
The detected value is input to the drive control means 9, and the probe 1 is
Find the inclination ξ (Fig. 6) between the surface and the surface to be measured. and,
The driving means M1 to M5 are driven so that this slope ξ becomes zero.

F. Example An embodiment of the present invention will be described with reference to FIGS. 1 to 7.

Figure 1 shows the general configuration of the probe attitude control device.
A probe 1 similar to the conventional one is provided at the tip of a robot 50 having five degrees of freedom via an axial force sensor 3, and each joint of the robot 50 is indicated by a symbol defined by JIS.

The robot 50 can rotate with respect to the base 51 by a one-rotation mechanism 52 (including a motor M1).

A rotating shaft 53 is connected to the rotating mechanism 52, and a rotating mechanism 54 (including a motor M2) connected to the tip of the rotating shaft 53 rotates the first
The second arm rotation mechanism 56 (motor M3) is connected to the tip of the first arm 55.
), the second arm 57 is rotatable, and the third arm 59 is rotatable by a third arm rotation mechanism 58 (including motor M4) connected to the tip of the second arm 57. . A wrist 61 is rotatably provided at the tip of the third arm 59 via a wrist rotation mechanism 60 (including a motor M5). At the tip of the wrist 61, for example, a second
A multi-axial force sensor 3 shown in the figure is provided, and a probe 1 is attached to this multi-axial force sensor 3. The multi-axial force sensor 3 has a probe 1 when the probe 1 is brought into contact with the surface to be measured.
It detects the axial forces acting on the X-axis, Y-axis, and Z-axis.

That is, in FIG. 2, the multiaxial force sensor 3 includes a first ring 4, a second ring 5 opposite thereto, three flexible beams 6 connecting both rings 4 and 5, and a flexible beam. 6 and a shearing force detection gauge 8 provided on the outer surface of the flexible beam 6.

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 response to the force acting on the probe 1, the bending beam 6 bends according to the amount of strain from each gauge. A signal is obtained and each axial force Fx*FYsFZ is known.

Referring again to FIG. 1, the rotation mechanism of each joint is equipped with a rotation angle sensor, for example, a rotary encoder R, for detecting the rotation angle of the rotation mechanism.
1 to R5 are provided, and the detected rotation angles θ□ to θ5 are input to the control device 9. Also.

The axial force FXt FYs FZ detected by the axial force sensor 3 is also input to the control device 9 . The control device 9 supplies drive signals θS to θSs to the motors M1 to M5 of each rotating mechanism so that the probe 1 is perpendicular to the surface to be measured based on calculations to be described later. Note that in FIG. 1, signal lines D1. Only D and the signal line of the axial force sensor 3 are shown connected to the control device 9, and other connections are omitted.

As shown in FIG. 3, the control device 9 is an axial force sensor.

As a signal input section from the axial force sensor 3, there is an interface 9a that inputs the analog signal from the axial force sensor 3 and adjusts its voltage level and zero point, a multiplexer 9b that selectively outputs the input analog signal, and an analog signal from the multiplexer 9b. It has an A/D converter 9c that converts the signal into a digital signal and inputs it to the CPU 9d. Further, as a signal input section from the rotary encoders R1 to R5, there is a counter circuit 9e that counts serial pulse signals from the rotary encoders R1 to R5 and converts them into parallel angle signals, and a signal from this counter circuit 9e is inputted to the CPU 9.
It has an input interface 9f that outputs to d. Furthermore, as a signal control unit, a ROM in which processing procedures are stored in advance
9g and R where various numerical values, data, etc. are temporarily stored.
AM9h and a CPU that controls each device according to processing procedures, performs various calculations based on input signals, compares the joint angle at that time, and outputs a joint speed command signal.
9d. Furthermore, as an output section.

The D/A converter 91 converts the digital joint speed command signal outputted from the CPU 9d into an analog signal, and the joint speed calculated from the joint speed command signal and the rotation angle signals from the rotary encoders R1 to R5 match. and a servo driver 9j that controls the motors M1 to M5.

In the configuration of the above embodiment, the base 51, arms 53, 55, 57, 59 and wrist 61 constitute support means, the motors M1 to M5 constitute drive means, and the axial force sensor 3 constitutes a force sensor.

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

In step S1, rotary encoders R1 to R
The angles θ, ˜θ, of each joint are detected by the output of a counter circuit 9e that counts pulse signals from 5. Step S
In step 2, the position and orientation of the center point 0 of the spherical portion 1b of the probe 1 are calculated based on these angles θ1 and θ5 and the lengths Q1 to Qs of each part of the robot 50 shown in FIG.

In FIG. 1, Ql is the distance from the attachment point of the base 51, that is, the robot coordinate origin Oi, to the first arm rotation mechanism 54, and ft2 is the distance between the first and second arm rotation mechanisms 54 and 56. The distance, Q, is the distance between the second and third arm rotation mechanisms 56 and 58, and Q4 is,
The distance Q from the third arm rotation mechanism 58 to the probe Z axis along the third arm 59 is the distance Q from the center O of the probe sphere 1b to the axis of the third arm 59 along the wrist 61. It's the distance it takes to reach your heart.

Here, the position of the probe 1 is defined as the position vector P from the origin 01 of the robot coordinates to the center 0 of the probe sphere 1b, P= (Ox, Oy, Oz) = f, (θ□~θ
s-Qx~Us>. Also, probe 1
The posture of is determined by calculating the direction cosine vector (ft gt h) as the inclination of the coordinate system of the axial force sensor 3 with respect to the robot coordinate system.

If the direction cosine vector f is, and the angle between the probe X-axis and the X-axis of the robot coordinate system is θxx, the angle between the probe

It can be expressed as Similarly, the angles that the probe y-axis and Z-axis make with the X-axis, y-axis, and Z-axis of the robot coordinate system are θyx, θYVt, θyz, and θzx, respectively.

When θZ/y θzz, the direction cosine vector geh can be expressed as 6 For example, the direction cosine vector h is
As shown in Figure 5, the X-axis, y-axis, and Z-axis of the robot coordinate system
Each axis of the coordinate system of the axial force sensor 3 is x', y'
, z'', the projections of the direction cosine vector h, which becomes a unit vector in the 2'' axis direction, onto the X, y, and Z axes are hx, hy, respectively.

hz.

Once the position and orientation of the probe 1 have been calculated in this way, the process advances to step S3, where three axial forces FX*FYvFZ are read from the axial force sensor 3. And step S
4, the inclination of the probe 1 with respect to the surface to be measured (posture angle ξ, ψ) is calculated from these three axial forces Fx and Fyt Fz.
Calculate.

FIG. 6 is a diagram illustrating each axial force FX*FY#FZ when the probe sphere 1b is brought into contact with the surface to be measured 2.

As shown by the solid line J, when the two axes of the probe 1 are inclined with respect to the surface to be measured 2, the direction of the drag force F acting on the probe 1 does not match the direction of the probe 2 axis, and the component force of the drag force F is Each axial force FX, ·FY+FZ is detected. Further, when the probe Z-axis is perpendicular to the surface to be measured 2 as shown by the dashed line, the direction of the drag force F acting on the probe 1 and the probe Z-axis coincide. From this, the probe 1 shown by the dashed line I with respect to the attitude of the probe 1 shown by the solid line J.
The attitude angles ξ and ψ of are found as follows.

Next, the process proceeds to step S5, where 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 or not the probe Z-axis is perpendicular to the surface to be measured). If ξ=0, the process ends, and if ξ≠0, the process advances to step S6.

In step S6, the posture angle ξ obtained in step S4,
Using ψ, the target orientation cosine (fsy gst
hs) as.

(fse gst hs) = f3 (ξ, ψ(ft
ge h) ).

Next, the process advances to step S7, and this target direction cosine (fst
gsy hs) and the position vector P of the center O of the probe sphere 1b obtained in step S2, calculate the target angles θs1 to θS of each joint where the probe Z-axis is perpendicular to the surface to be measured 2. , (θB1~θss) = L ((f
st g8e hs) e P). Then, in step S8, motor drive commands 11 to i are supplied from the D/A converter 91 to the servo drive 9j so that each joint becomes θS□ to θS, and thereby each motor M1 to
The posture of the two axes of the probe is controlled perpendicularly to the surface to be measured 2 by driving the MS. At this time, the center point 0 of the probe sphere 1b is set as the center of motion of the robot, and as shown in FIG. 7, while the probe 1 is in contact with the surface to be measured 2 at the contact point Q on the surface to be measured 2, The posture of the probe 1 is controlled from the posture shown by the dashed-dotted line to the posture shown by the solid line J.

Such a probe attitude control device is used in a three-dimensional shape measuring machine to control the attitude of the two axes of the probe sphere 1b perpendicular to the surface to be measured 2 so that the point P of the sphere 1b is in contact with the surface to be measured 2. By measuring each position on the X, Y, W, and Z axes of the sphere 1b in this state, it is possible to measure the shape and dimensions without errors in real time without performing interpolation calculations as in the conventional case, and continuous dimension measurements can be performed. Contributes to measurement automation. In addition, the surface to be measured 2
Even if the inclination angle α is 90 degrees or more, the probe 1 can be brought into contact with the surface to be measured 2 perpendicularly, and there is no need to manually shift the position of the object to be measured, contributing to automation of measurement.

Furthermore, if this invention is applied to an ultrasonic flaw detection scanner device, the ultrasonic probe can be held perpendicularly to the surface to be inspected at all times, improving inspection accuracy. Autonomous driving will become possible.

Although the robot 50 described above has five degrees of freedom, if the shape of the surface to be measured is limited and known in advance,
There is no particular need for 5 degrees of freedom. For example, as shown in FIG. 8, if the robot is a three-dimensional object whose x-z cross section is the same along the y-axis, the present invention can be implemented using a robot with three degrees of freedom. Further, the driving means is not limited to the motor, the axial force sensor may be of another type, and the shape of the probe is not limited to the embodiment.

G0 Effects of the Invention According to the present invention, since the attitude of the probe can be controlled so that it is perpendicular to the surface to be measured, it is possible to automate three-dimensional shape measuring machines, ultrasonic flaw detection scanners, etc. equipped with this type of probe. becomes possible. Furthermore, if used in a three-dimensional shape measuring machine, error-free measurement becomes possible.

[Brief explanation of the drawing]

Figures 1 to 7 show one embodiment of the present invention.
Figure 2 is a schematic diagram of the overall configuration, Figure 2 is a perspective view of the axial force sensor, Figure 3 is a block diagram of the control device, Figure 4 is a flowchart of the probe attitude control procedure, and Figure 5 shows the direction cosine. FIGS. 6(a) and 6(b) are diagrams for explaining the axial force detected by the axial force sensor, and FIG. 7 is a diagram for explaining the posture control of the probe. FIG. 8 is a perspective view showing an example of a shape that can be measured with three degrees of freedom. 9 and 10 show a conventional example, in which FIG. 9 is a perspective view showing an example of a conventional three-dimensional shape measuring machine, and FIG. 10 is a detailed enlarged view of the probe. 1 Nib lobe 2: Surface to be measured 3: Axial force sensor 9: Control device R1 to R5: Rotary encoder M1 to M5: Motor

Claims (1)

[Scope of Claims] Supporting means having multiple degrees of freedom; driving means for driving the supporting means; a probe provided on the supporting means; A force sensor detects the acting force, and the driving means is driven so that the probe comes into contact with the surface to be measured perpendicularly by calculating the inclination of the probe with respect to the surface to be measured based on the force detected by the force sensor. A probe attitude control device comprising: drive control means.