JPH066271B2 - Robot control method with visual sensor - Google Patents

Description

The present invention relates to a control method for a robot with a visual sensor that operates a robot based on image data that mainly handles two-dimensional information.

[Conventional technology]

Conventionally, when controlling a hand of this type of robot, for example, as shown in FIG. 3, a visual sensor (camera) 1 is used.
The moving target position P ₂ (x ₁ , y ₁ , z ₁ ) of the robot hand is visually detected. Since image data is originally two-dimensional information,
The preset height H ₀ of the camera 1 and the two-dimensional information (2
Calculate P ₂ using the angle of view information).

Also, when moving the robot, in order to avoid interference between the robot and the object during movement, the position P ₁ (x ₁ , y ₁ , z ₁ ) on the camera side should be sufficient (at a distance h) from point P ₂ above. _1- h) is calculated. When the robot is moved, the robot hand is first moved horizontally to the point P ₁ as indicated by the arrow A, and then moved to the point P ₂ in the optical axis direction as indicated by the arrow B.

[Problems to be solved by the invention]

Here, there is no problem when the distance H ₀ does not change, but in general, the work in the pallet often changes.

Two-dimensional information based on images is actually three-dimensional information.
The information amount is a two-dimensional view angle (α,
β) (only α in FIG. 3 is entered), so that one point (x ₁ , y ₁ ) on the screen has a meaning as a straight line l (x ₁ , y ₁ ) in space.

Therefore, if H ₀ has an error of ΔH, the robot positioning error is Becomes

Conventionally, α and β are not so large due to the layout, so this error is ignored, the movement from P ₁ point to P ₂ point is delayed, and it is checked whether or not the hand touches the work. I was trying to solve the problem.

However, when ΔH is large or when α and β are large (when the camera has a wide field of view), this error becomes large and it becomes difficult to allow the error in the design of the hand.

For example, considering a case where a robot performs bundling of a cylindrical bush B as a target work as shown in FIG. 5, the bushes B appropriately placed in the pallet 2 are at various heights. Even if the controller is given the data of the number of stages, a maximum height error of 100 mm occurs.

Therefore, as shown in the equation (1), the larger the peripheral portion of the pallet 2, that is, the larger the angle of view (α, β), the larger the error becomes, and as shown in FIG. 5, δ _x = 20 mm in the x direction.
May reach.

The robot hand can handle an error of ± 10 mm, but the conventional control method described above could handle only about 75%.

The present invention has been made in view of the above circumstances, and provides a control method for a robot with a visual sensor that can reliably move the robot to the target work even if the distance between the visual sensor and the target work changes. The purpose is to

[Means for solving problems]

According to the present invention, in a control method for a robot with a visual sensor, which comprises a sensor for detecting proximity of a target work, and controls movement of a robot hand to the target work whose distance from the visual sensor varies, the target work is imaged by the visual sensor. A first straight line path from the visual sensor to the target work is obtained based on the two-degree-of-freedom view angle information obtained from the captured image.
And a position on the straight line path at which the distance from the visual sensor is closer than the distance to the target work and the distance from the visual sensor is farther than the distance to the target work. In the second step of obtaining the position coordinates of the second point, and after the robot hand is moved from the standby point to the first point, the hand is moved from the first point along the obtained straight line path. And a third step of moving the hand at a low speed, and when the sensor detects the proximity of the target work during the low speed movement of the hand, the movement of the hand is stopped and the hand holds the target work at this position, and A fourth step of executing a predetermined error process when the target work is not detected by the sensor up to the second point, and a step of holding the target work and then moving upward from the gripping position. Distance to move the hand to the third point spaced further from the third point to comprise a fifth step of moving the hand to a predetermined workpiece moving position.

[Action]

By moving along the straight line, the target work is inevitably met, and the target work can be accurately moved regardless of the distance between the visual sensor and the target work.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing an example of handling a work by using the control method for a robot with a visual sensor according to the present invention.

In FIG. 1, first, the proximity switch 11 is arranged at an appropriate position of the robot hand 10. The proximity switch 11 detects the work 12, and when the proximity switch 11 detects the work 12, the movement of the robot is stopped, and the work 12 can be gripped by closing the hand 10.

This robot hand 10 has teaching points P ₀ → P ₁ → P ₃
→ P ₄ → P ₅
Carry from 3 to conveyor 14. The teaching point P ₂ is not necessarily the point where the hand 10 passes, but it is necessary to teach.

Of the teaching points P _{0 to} P ₅ , P ₁ , P ₂ , P ₃ , and P ₄ are not points that can be taught in advance, and are determined by the image data of the camera 15 or while the robot is moving. Now, let these points be tentative positions, P ₁ = (x ₁ ′, y ₁ ′, z ₁ ), P ₂ = (x ₂ ′, y ₂ ′, z ₂ ) P ₃ = (x ₃ ′, y _{3 ', z 3'),} P 4 = (x 3 ', y 3', z 3 '-50
Teaching with 0). As is clear from the above tentative position, the z-coordinates of P ₁ and P ₂ are known values as shown in FIG. 1, Z ₂ is the position of the bottom of the pallet 13, and Z ₁ is It is an arbitrary position above the position of at least the uppermost work on the camera 15 side with respect to Z ₂ and where interference between the hand 10 and the pallet 13 does not occur during movement of the hand 10. Also, P ₄ is a point 500 mm above P ₃ .

Now, when the camera 13 takes an image of the work 12 to be carried and the angle of view (α, β) of the work 12 is read, P ₁ , P ₂
The coordinates of α, β, z ₁ → P ₁ (x ₁ , y ₁ , z ₁ ) α, β, z ₂ → P ₂ (x ₂ , y ₂ , z ₂ ) are calculated. As a result, the correct positions of P ₁ and P ₂ are taught.

Next, the operation of the robot will be described with reference to the flowchart shown in FIG.

First, the angle of view (α, β) is read from the camera 15 (step 100), and P ₁ and P ₂ are calculated (step 101).
Next, the hand 10 is moved from P ₀ to P ₁ .

Subsequently, linear interpolation is performed from P ₁ to P ₂ to move at low speed (step 103), and the proximity sensor 11
Determines whether the workpiece 12 is detected (step 1
04). When the proximity switch 11 does not detect the work 12, it is judged whether or not the hand 10 has reached P ₂ (step 105), and when it has not reached, it moves toward P ₂ again.

When the work 12 is detected by the proximity switch 11 during the movement to P ₂ , the movement of the robot is stopped, teaching is performed at this point as P ₃ (step 106), and the hand 10 is closed and the work 12 is gripped. (Step 10
7).

Next, teach point P ₄ (This is the above teaching point.
P ₃ raises the hand 10 to 500mm above the point) than (step 108), followed by moving to P _5, opening the hand 10 reaches the P ₅ (step 109).

When the work 12 is placed on the conveyor 14 by the above operation, the work 12 is moved to P ₀ again (step 110), whereby the handling of one work 12 is completed.

On the other hand, the proximity switch 11 cannot detect the work 12
When reaching P ₂ , raise 500 mm above P ₂ (Step 1
11) While moving from this position directly to P ₀ (step 112), “error” is displayed on the display unit (not shown) of the controller, and the operation ends.

The sensor for detecting the work attached to the hand 10 is not limited to the proximity switch, and various sensors such as a sensor for detecting the time of contact with the work can be considered. The method of the present invention is not limited to the movement mode of the present embodiment, and may be any method including at least the step of moving along the straight line connecting the target work from the visual sensor.

〔The invention's effect〕

As described above, according to the present invention, even if the target work position changes with respect to the visual sensor, the robot hand is moved along a straight line toward the target work detected by the visual sensor. It is possible to meet the target work without fail and move the hand to the target work reliably.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of handling a work by using the method of the present invention, FIG. 2 is a flowchart showing the robot operation in FIG. 1, and FIG. 3 is a diagram showing a problem of a conventional control method for a robot with a visual sensor. FIG. 4 is a diagram used for explanation, FIG. 4 is a diagram showing the positional relationship between the camera and the target work and dimensions in FIG. 3, and FIG. 5 is a maximum error due to conventional visual detection of the target work in FIG. It is a figure. 10 ... Robot hand, 11 ... Proximity switch, 12 ... Work, 13 ... Pallet, 14 ... Conveyor, 15 ... Camera.

Claims (1)

[Claims] 1. A control method for a robot with a visual sensor, comprising a sensor for detecting the proximity of a target work, and controlling movement of a robot hand to the target work whose distance from the visual sensor fluctuates. Then, a first step of obtaining a straight line path from the visual sensor to the target work based on the two-degree-of-freedom view angle information obtained from the captured image; and a distance from the visual sensor on the straight line path to the target work to the target work. A second step of obtaining the position coordinates of a first point located closer than the distance and a second point located farther from the visual sensor than the distance to the target work; From the first point to the first point, and then moving the hand at a low speed from the first point along the determined straight line path; During the low speed movement of, when the proximity of the target work is detected by the sensor, the movement of the hand is stopped and the hand grips the target work at this position,
If a target work is not detected by the sensor up to the second point, a predetermined error process is executed.
After the target work is gripped, the hand is moved to a third point that is upwardly separated from the gripping position by a predetermined distance, and then the hand is moved from the third point to a predetermined work movement position. A fifth method, and a method for controlling a robot with a visual sensor, comprising: