JPH0464561B2 - - Google Patents

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, y-axis, and z-axis directions, and the tip of the probe 1 is brought into contact with the surface to be measured 2 manually or automatically while maintaining the same posture.
Read the x, y, and z positions at that time. Generally, the probe 1 has a shaft portion 1a as shown in FIG.
and a spherical portion 1b at the tip thereof, and when brought into contact with the surface to be measured 2, the measuring instrument body reads the position of the tip P of the spherical portion 1b as a measurement value. 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 O of the spherical portion 1b may be read.

C Problems to be Solved by the Invention However, when the surface to be measured 2 is inclined by α degrees with respect to the horizontal plane HP as shown in FIG. Contact with surface 2. Therefore, a deviation occurs between the position of the contact point Q and the measurement position P by δx and δz, resulting in an error.

Conventionally, several points are measured in the vicinity of the inclined surface, the points are interpolated to obtain the inclination angle α, and based on this angle α, the deviations δx and δz are calculated to correct the measured values. 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 hinder automation of 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, if the inclination angle α of the surface to be measured 2 becomes 90 degrees or more, the probe 1
The tip ball portion 1b cannot be brought 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-mentioned problems are not limited to three-dimensional shape measuring machines, but also apply to various types of equipment that perform measurements by bringing the probe into contact with the surface to be measured, such as an automatic ultrasonic flaw detection scanner equipped with an ultrasonic probe. 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.

D. Means for Solving the Problems The present invention will be described based on FIG. 61, driving means M1 to M5 such as DC motors for driving these supporting means, a probe 1 provided on the supporting means 61, and a probe 1 when the probe 1 is brought into contact with the surface to be measured.
A multi-axis force sensor 3 detects forces in the direction of at least two coordinate axes and moments around one other coordinate axis acting on the surface, and an inclination ξ of the probe 1 with respect to the surface to be measured based on the detection results of the multi-axis force sensor 3.
(FIG. 6) and drives the driving means M1 to M5 so that the probe 1 comes into contact with the surface to be measured perpendicularly.

E Effect The force acting on the probe 1 is detected by the multi-axial force sensor 3 where the probe 1 comes into contact with the surface to be measured. Since the force detected differs depending on the inclination of the probe 1 and the surface to be measured, the detected value of the multi-axis force sensor 3 is input to the drive control means 9, and the inclination ξ of the probe 1 and the surface to be measured (Fig. 6) is inputted to the drive control means 9. ). Then, the driving means M1 to M5 are driven so that this slope ξ becomes zero.

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

FIG. 1 shows a schematic overall configuration of a probe attitude control device, in which 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 is JIS
It is indicated by the symbol specified in . The robot 50 can rotate relative to the base 51 by a rotation mechanism 52 (including a motor M1). A rotation shaft 53 is connected to the rotation mechanism 52, and a first arm 55 can be rotated by a rotation mechanism 54 (including a motor M2) connected to the tip of the rotation shaft 53. The second arm 57 can be rotated by a second arm rotation mechanism 56 (including a motor M3), and by a third arm rotation mechanism 58 (including a motor M4) connected to the tip of the second arm 57. A third arm 59 is pivotable. A wrist 61 is rotatably provided at the tip of the third arm 59 via a wrist rotation mechanism 60 (including a motor M5). For example, a multi-axial force sensor 3 shown in FIG. 2 is provided at the tip of the wrist 61.
This 6-axis force sensor (hereinafter referred to as a multi-axis force sensor)
Probe 1 is attached to 3. The multi-axial force sensor 3 detects the axial forces of the x-axis, y-axis, and z-axis that act on the probe 1 when the probe 1 is brought into contact with the surface to be measured.

That is, in FIG. 2, the multiaxial force sensor 3
consists of a first ring 4, a second ring 5 opposing this, three flexible beams 6 connecting both rings 4 and 5, and a tension/compression ring provided on the inner surface of the flexible beam 6. It consists of a force detection gauge 7 and a shear force detection gauge 8 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,
When the flexible beam 6 deflects in response to the force acting on the probe 1, a signal corresponding to the amount of strain is obtained from each gauge,
Each axial force Fx, Fy, Fz and moment around each axis
You can know Mx, My, and Mz.

Referring again to FIG. 1, the rotation mechanism of each joint is provided with rotation angle sensors such as rotary encoders R1 to R5 that detect the rotation angle thereof, and the detected rotation angles θ ₁ to _{θ 5} are input to the control device 9. ,Also,
The axial forces Fx, Fy, and Fz detected by the axial force sensor 3 are also input to the control device 9. The control device 9 supplies drive signals θ _S1 to θ _S5 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. In addition, in Figure 1,
Signal line D ₁ related to the third arm rotation mechanism 58,
D ₂ and the signal line D ₃ of the axial force sensor 3 are connected to the control device 9.
, and other connections are omitted.

As shown in FIG. 3, the control device 9 includes, as a signal input section from the axial force sensor 3, an interface 9a that inputs an analog signal from the axial force sensor 3 and adjusts its voltage level and zero point, and an input analog input section. a multiplexer 9b that selectively outputs signals;
It has an A/D converter 9c that converts the analog signal from the multiplexer 9b into a digital signal and inputs the digital signal 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 CPU 9d to which signals from the counter circuit 9e are input. It has an input interface 9f for outputting to. Further, as a signal control unit, a ROM 9g in which processing means is stored in advance, and a RAM 9 in which various numerical values, data, etc. are temporarily stored.
h, and a CPU 9d that controls each device according to a processing procedure, performs various calculations based on input signals, compares the joint angles at that time, and outputs a joint speed command signal. Furthermore, as an output unit, a D/A converts the digital joint speed command signal output from the CPU 9d into an analog signal.
The converter 9i controls the motors M1 to M5 so that the joint speed command signal and the joint speed calculated from the rotation angle signals from the rotary encoders R1 to R5 match.
and a servo driver 9j for controlling the servo driver 9j.

In addition, in the configuration of the above embodiment, the base 5
1. Arms 53, 55, 57, 59 and wrist 6
1 constitutes a support means, motors M1 to M5 constitute a drive means, and axial force sensor 3 constitutes a force sensor.

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

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 pulse signals from the rotary encoders R1 to R5. In step S2, these angles θ ₁ to _{θ 5} and the length _l 1 of each part of the robot 50 shown in FIG.
The center point O of the spherical part 1b of the probe 1 based on ~l ₅
Calculate the position and orientation of. In FIG. 1, l ₁ is the distance from the attachment point of the base 51, that is, the robot coordinate origin O ₁ to the first arm rotation mechanism 54, and l ₂ is the distance between the first and second arm rotation mechanisms 54 and 56. , _l3 is the distance between the second and third arm rotation mechanisms 56 and 58, l4
is the distance from the third arm rotation mechanism 58 to the probe z-axis along the third arm 59, and _l5 is the distance from the center O of the probe sphere 1b to the wrist 6.
1 to reach the axis of the third arm 59.

Here, the position of the probe 1 is expressed as a position vector from the origin O ₁ of the robot coordinates to the center O of the probe sphere 1b as follows: = (Ox, Oy, Oz) = f ₁ (θ ₁ ~ θ ₅ , l ₁ ~ l ₅ ). Also, the attitude of probe 1 is
It 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.

If the direction cosine vector is =fx fy fz, and the angle the probe x-axis makes with the x-axis of the robot coordinate system is θxx, the angle with the y-axis is θxy, and the angle with the z-axis is θxz, then this direction cosine vector is , = cosθxx cosθxy cosθxz. 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 respectively θyx, θyy, θyz and θzx, θzy,
If θzz, then the direction cosine vectors can be expressed as: =gx gy gz=cosθyx cosθyy cosθyz =hx hy hz=cosθzx cosθzy cosθzz For example, the direction cosine vector h can be expressed as coordinate system x
When the respective axes of the coordinate system of the axial force sensor 3 are located at x', y', and z' with respect to the axis, y-axis, and z-axis, y
The projections to the axis and z axis are hx, hy, and hz, respectively.

When the position and orientation of the probe 1 are calculated in this way, the process proceeds to step S3, where the axial force sensor 3
Read the three axial forces Fx, Fy, and Fz from. Then, in step S4, these three axial forces Fx,
The inclination (posture angle ξ, φ) of the probe 1 with respect to the surface to be measured is calculated from Fy and Fz.

FIG. 6 is a diagram illustrating each axial force Fx, Fy, and Fz when the probe ball portion 1b is brought into contact with the surface to be measured 2. FIG.

As shown by the solid line J, when the z-axis of the probe 1 is 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 probe z-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 I, the direction of the drag force F acting on the probe 1 and the probe z-axis coincide. From this, the attitude angles ξ and φ of the probe 1 shown by the dashed-dotted line I with respect to the attitude of the probe 1 shown by the solid line J are as follows: ξ=tan ^-1 (√F _X ² +F _Y ² /F _Z ) ψ=tan ^-1 It is found by (F _Y /F _X ).

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, end; if ξ≠0, step
Proceed to S6.

In step S6, using the attitude angles ξ and ψ obtained in step S4, the target attitude in which the probe z-axis is perpendicular to the surface to be measured 2 is set as the target direction cosine (s, , ). s, s)=f ₃ (ξ, ψ(,,)
Find it with

Next, proceeding to step S7, the probe x-axis is set relative to the surface to be measured 2 based on 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 θ _S1 to θ _S5 of each joint that are perpendicular to each other are determined by (θ _S1 to θ _S5 ) f ₄ (s, s, s,). Then, in step S8, motor drive commands i ₁ to i ₅ are supplied from the D/A converter 9i to the servo drive 9j so that each joint becomes θ _S1 to _{θ S5} , thereby driving each motor M1 to M5. to control the orientation of the probe z-axis perpendicular to the surface to be measured 2. At this time, the center point O 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 attitude of the probe 1 is controlled from the attitude I shown by the dashed-dotted line to the attitude 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 probe sphere 1b so that the z-axis is perpendicular to the surface to be measured 2 so that point P of the sphere 1b is in contact with the surface to be measured 2. In the state, x, y, z of the sphere 1b
By measuring each axis position, shape and dimensions can be measured in real time without error without performing interpolation calculations as in the past, and continuous dimension measurements can be performed, contributing 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, since a 6-axis force sensor is used as a means for detecting the force acting on the probe 1, it is also possible to detect the moments Mx, My, and Mz around the x, y, and z axes. It becomes possible to accurately bring the probe 1 into contact perpendicularly to the surface to be measured 2 regardless of the size of the surface. In addition, the 8th
If the surface to be measured has a two-dimensional shape in the x, y, and z directions as shown in the figure, instead of the 6-axis force sensor, Fx, Fz,
A three-axis force sensor capable of detecting only My may be used.

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, five degrees of freedom are not particularly necessary if the shape of the surface to be measured is limited and known in advance. For example, as shown in FIG. 8, if the three-dimensional robot has the same x-z cross section along the y-axis, the present invention can be constructed using a robot with three degrees of freedom. In addition, the driving means is not limited to a motor, and furthermore, the multi-axis force sensor is
Other types may be used, and furthermore, the shape of the probe is not limited to the embodiment.

G. 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, automation of three-dimensional shape measuring machines, ultrasonic flaw detection scanners, etc. equipped with this type of probe is possible. becomes possible. Also,
If used in a three-dimensional shape measuring machine, error-free measurement becomes possible.

Furthermore, by using a multi-axis force sensor,
Since each moment around the x, y, and z axes can also be detected, the probe can be accurately brought into contact perpendicularly to the surface to be measured, regardless of the magnitude of the frictional force on the surface to be measured.

[Brief explanation of the drawing]

1 to 7 show an embodiment of the present invention, in which FIG. 1 is a general schematic diagram, FIG. 2 is a perspective view of an axial force sensor, and FIG. 3 is a block diagram of a control device. , FIG. 4 is a flowchart showing the procedure of probe attitude control, and FIG. 5 is a diagram explaining direction cosine.
FIGS. 6a and 6b are diagrams for explaining the axial force detected by the axial force sensor, and FIG. 7 is a diagram for explaining the attitude control of the probe. FIG. 8 is a perspective view showing 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: Probe, 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] 1. A support means having multiple degrees of freedom; a drive means for driving the support means; a probe provided on the support means; a multi-axis force sensor that detects forces in the directions of at least two coordinate axes and moments around one other coordinate axis acting on the probe; . A probe attitude control device comprising: drive control means for driving the drive means so that the probe comes into contact with the surface to be measured perpendicularly.