JPH0663759B2 - Force detection probe device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a force detection probe device, and in particular to a work robot or work machine adopting a teaching playback system,
The present invention relates to a force detection probe device suitable for use in a three-dimensional shape measuring machine.

[Conventional technology]

The force detection probe device detects a reaction force from a work surface in a work robot, a work machine, or a three-dimensional shape measuring machine that employs a teaching playback method, and performs control and calculation of each from the force information. Is used for.

As shown in FIG. 9, the conventional force detection probe device is a solid probe having a tip that contacts the surface of the work 20.
21 and the probe when the probe 21 is pressed against the work surface.
It consisted of a multi-axis force sensor 22 that detects the reaction force FN applied to 21.

[Problems to be Solved by the Invention]

However, in the conventional force detection probe device, when the probe 21 is pressed against the work surface, since the reaction force is originally the force FN perpendicular to the work surface, the multi-axis force sensor
22 detects the force FN, but since the sliding friction force FS occurs at the contact point between the probe and the work surface, the multi-axis force sensor 22 must detect the resultant force FR affected by the friction force FS. become. Therefore, when the inclination angle of the work surface is calculated from the force information detected by the force detection probe device and the shape of the work is measured or the posture of the robot is controlled, the measurement or control result is affected by friction. There was a problem of causing an error. In addition, when controlling the movement direction based on the detected force information of the reaction force while copying the work surface in the work surface copying control, the force information is affected by the sliding friction generated between the probe and the work surface. However, there is a problem in that an error occurs in the control command value, it is difficult to move smoothly, and the work surface may be scratched by the probe.

An object of the present invention is to provide a force detection probe device that can obtain force information that is not affected by sliding friction at a contact point between a probe and a work surface.

[Means for Solving the Problems]

The above-mentioned object is a force detection probe device comprising a probe that comes into contact with a work surface and a multi-axis force sensor that detects a force applied to the probe, the probe main body having a spherical bearing at the tip, and the probe main body. 2. A force detection probe characterized in that the ball is mounted on the spherical bearing with a minute gap left and a means for supplying a pressurized gas to the minute gap, and the ball is supported by the pressurized gas. Achieved by the device.

[Action]

In the present invention thus configured, when the ball is pressed against the work surface, the gas pressure in the minute gap between the spherical bearing and the ball tends to push out the ball with a force corresponding to the pressing force. And the ball is supported by the pressurized gas. The ball supported by this pressurized gas rolls freely by gas lubrication applying the principle of the static pressure gas bearing, and when the probe contacts the work, the ball is received from the work surface without causing sliding friction at the contact point. The reaction force is transmitted through the gas film, and the multiaxial force sensor detects the reaction force that is not affected by this frictional force.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1, the force detection probe device of the present embodiment has a ball probe 1 that contacts the work surface and a multi-axis force sensor 2 that detects the force applied to the ball probe 1.
The ball probe 1 is composed of a probe main body 4 having a spherical bearing 3 at its tip and a ball 6 attached to the spherical bearing 3 of the probe main body 4 with a minute gap 5 left therebetween. As means for supplying pressurized gas to 5, an introduction hole 7 for pressurized air and an air supply hole 8 having an orifice throttle are formed. The pressurized air introduction hole 7 is connected to an external pressure source 9 as shown in FIG. 2, and the pressurized gas sent from the pressure source 9 passes from the introduction hole 6 through the orifice restrictor of the air supply hole 8 to a spherical surface. It is sent into the minute gap 5 between the bearing 3 and the ball 6 and discharged from there through to the outside.

FIG. 2 shows a usage example in which the force detection probe device of this embodiment is used for controlling the copying of a work surface. The force detection probe device is attached to the hand of the robot 10 and is a work object having an arbitrary curved surface shape. It is pressed so that it contacts a certain work 11. At this time, the ball probe 1 transmits the force (reaction force from the work surface) applied to the ball probe 1 to the multi-axis force sensor 2 while being in contact with the work surface, and the multi-axis force sensor 2 detects the force and the controller 12 to transmit force information. The controller 12 calculates teaching data based on information obtained from the multi-axis force sensor 2, the teaching box 13 for controlling the robot 10, and the robot 10, and stores the teaching data in the storage device 14. .

Next, the operation of the force detection probe device of this embodiment configured as described above will be described.

FIG. 3 shows a conventional solid probe 21. Probe 21
When is pressed against the work surface with force F in a stationary state, a lateral force is generated due to the deflection of the probe 21, the backlash of the machine, and the like, and a sliding frictional force FS is generated at the contact point. Therefore, the multi-axis force sensor detects the resultant force FR of the sliding friction force FS and the reaction force of the pressing force F.

On the other hand, in the present embodiment, when the ball probe 1 is similarly pressed, as shown in FIG.
As shown in the figure, a symmetrical pressure distribution is generated in the pressurized gas sent into the minute gap 5 between the ball 6 and the ball 6, and the force exerted on the ball 6 by the pressure of the pressurized gas and the force pressing the ball probe 4 against the work. , The balls 6 roll freely by gas lubrication applying the principle of the static pressure gas bearing. Therefore, sliding friction due to contact does not occur.
At this time, the reaction force FR from the work that the ball 6 receives is transmitted to the probe main body 4 via the gas film in the minute gap 5.

The above is the description when the ball probe 1 is in a stationary state, but when the ball probe 1 moves at an arbitrary speed v, it becomes as shown in FIG. That is, in this case, the ball 6
Causes rolling friction FS at the contact point, and this rolling friction F causes the center of the ball 6 to decenter from the center of the spherical bearing 3. At this time, the gap on the side where the balls 6 are biased becomes small, the fluid resistance increases, and the pressure accordingly increases.
On the other hand, on the side where the ball 6 is distant, the gap becomes large, the fluid resistance decreases, and the pressure also decreases. That is, the gap 5
In the pressurized gas, a pressure distribution is generated that is biased toward the side with a smaller gap. Therefore, due to the pressure difference between the balls
Trying to return to the center of. Here, the other axial force sensor 2 detects the pressure difference generated in the spherical bearing 3 of the probe as a change in the direction of force. Therefore, the amount of change in the force detected by the multi-axis force sensor 2 is due to the force of the ball 6 returning to the center of the spherical bearing 3, that is, the effect of the rolling friction force FS that the ball 6 receives at the contact point with the work. However, the effect of the rolling friction force is extremely small compared to the effect of the sliding friction force.

As described above, by using the ball probe of the present embodiment in both the stationary state and the moving state, the conventional probe does not affect the sliding friction that is always generated at the contact point with the workpiece, and the surface of the workpiece is not affected. The reaction force of can be detected.

FIG. 6 shows the results of measuring the frictional resistance by using the ball probe of the present example and a probe having the same shape as that of the ball fixed by caulking and moving the probe vertically at a constant speed. The reaction force acting perpendicular to the work surface is defined as the normal force N, and the force generated in the direction opposite to the moving direction is frictional resistance.
It was FS. In the figure, a circle indicates a ball fixed probe when the work surface has an inclination angle α of 0 °, and a circle indicates a friction resistance when the ball probe of the present embodiment is used under the same conditions. Show. Further, the mark Δ indicates the frictional resistance when the ball probe of the present embodiment is used to move along the work surface having the inclination angle α = 20 °. The balls used were steel balls with surface chrome plating, and the workpieces used were S35C steel plates.

As can be seen from FIG. 6, the frictional resistance FS is proportional to the increase in the normal force N in both the ball probe and the ball fixed probe of this embodiment, but the rate of increase is higher in the ball probe of this embodiment. Much smaller. When the friction coefficient is μ and μ is expressed by μ = FS / N, a calculation result of μ = 0.02 for the ball probe of this embodiment and μ = 0.18 for the ball-fixed probe is obtained when the inclination angle α = 0 °. It was in this way,
It was confirmed that the ball probe of the present embodiment can significantly reduce the frictional resistance when copying the work surface as compared with the conventional probe.

Further, when calculating the inclination angle of the work surface from the force information detected by the force detection probe device, the inclination angle detection error α'due to the frictional resistance μ is tan α '= μ in the case of the ball probe of this embodiment. α '= 1.14 °, and for a ball fixed probe α' = 10.2 °. Therefore, in the ball probe of the present embodiment, the error of the tilt angle can be made about 1/10 of that of the conventional probe, and the tilt angle of the work surface can be accurately calculated.

In FIG. 6, when the inclination angle of the work surface is α = 20 °, the coefficient of friction of the ball probe of this embodiment is μ = 0.05, which is larger than that when α = 0 °. Is
Due to the inclination of the work surface, a lateral force acts on the ball at the tip of the probe, the balance between the pressure due to the pressurized gas and the reaction force against the pressing is lost, and the spherical bearing surface and the ball come into contact, increasing the frictional resistance. It is supposed to do. However, even in this case, although the frictional resistance increases,
Less susceptible to friction than traditional probes. Further, in this case, an increase in frictional resistance can be significantly reduced by using a probe as shown in FIGS. 7 and 8 described later.

Therefore, according to the force detection probe device of the present embodiment, when the ball probe is pressed against the work, it is possible to detect the reaction force that is not affected by the sliding friction at the contact point, and the direction of the normal to the work surface is detected. The force can be detected. Therefore, the inclination angle of the work surface can be accurately calculated, and the shape can be measured by the force information. Further, even in the copying teaching work, since the inclination angle of the work surface can be accurately calculated, the movement target can be accurately determined while copying, and the work surface is not damaged. Further, since the force in the normal direction of the work surface can be detected, when controlling the posture of the robot or the like with respect to the work surface, it is possible to accurately control the force information from the force information.

Another embodiment of the present invention will be described with reference to FIGS. 7 and 8. 7 and 8 both show another structural example of the means for supplying the pressurized gas to the minute gap between the spherical bearing and the bolt.

That is, in FIG. 7, an orifice throttle is not provided in the air supply hole 15, but instead, an extremely shallow groove 17 connected to the air supply hole 15 is radially provided in the spherical bearing 16, and the throttle is configured by the resistance of the groove 17.

According to this embodiment, the gap 5 between the spherical bearing 16 and the ball 6 can be made very small, so that the supporting rigidity of the hydrostatic bearing is increased and the load capacity can be increased.

Further, in FIG. 8, a porous material is used for the member forming the spherical bearing 18, and the throttling effect is obtained by the fluid resistance thereof. The lower part of the introduction hole 7 for the pressurized gas is the porous material of the spherical bearing 18. The upper end surface of the probe is widened so that air can be supplied, and the spherical bearing 18 and the outside of the probe body 4 are covered with a shield 19 to be integrated.

Also in this embodiment, since the air supply holes of the porous material are distributed over the entire spherical bearing, the gap 5 between the spherical bearing 18 and the ball 6 can be made small and the load capacity can be increased.

〔The invention's effect〕

According to the present invention, the effects listed below can be obtained.

(1) When the ball probe is pressed against the work surface, the reaction force that is not affected by the sliding friction at the contact point can be detected, and therefore the force in the normal direction of the work surface can be detected.

(2) Due to the effect of (1) above, the inclination angle of the work surface can be accurately calculated, and the shape can be measured based on the force information.

(3) Due to the effect of (1) above, when controlling the attitude of the robot with respect to the work surface, the force information can be used for accurate control.

(4) With the effect of (1) above, in the copying teaching, the moving target can be accurately determined while copying, and the work surface is not damaged.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing the structure of a force detection probe device according to an embodiment of the present invention, FIG. 2 is a view showing a usage state of the force detection probe device, and FIG. 3 is a conventional force. It is a figure which shows the force detection state of a detection probe apparatus, FIG. 4 is a figure which shows the force detection state in the stationary state of the force detection probe apparatus of this Example, and FIG. 5 is a force detection probe of this Example. FIG. 6 is a diagram showing a force detection state when the apparatus is moving. FIG. 6 shows a normal force N and a frictional resistance FS for each of the force detection probe apparatus of this embodiment and the conventional force detection probe apparatus.
It is a figure showing the result of an experiment performed about the relation with
FIG. 8 is a sectional view showing a force detecting probe device according to another embodiment of the present invention, FIG. 8 is a sectional view showing a force detecting probe device according to still another embodiment of the present invention, and FIG. It is a figure which shows the force detection probe apparatus of FIG. Explanation of symbols 1 ... Ball probe, 2 ... Multi-axis force sensor 3 ... Spherical bearing, 4 ... Probe body 5 ... Gap, 6 ... Ball 7 ... Pressurized gas introduction hole 8 ... Air supply hole

Claims (1)

[Claims] 1. A force detection probe device comprising a probe that contacts a work surface and a multi-axis force sensor that detects the force applied to the probe, the probe main body having a spherical bearing at the tip, and the probe main body. Force detection comprising a ball mounted on the spherical bearing of the main body with a minute gap left and a means for supplying a pressurized gas to the minute gap, and the ball is supported by the pressurized gas. Probe device.