JPH0651824A - Tool posture control method - Google Patents

Abstract

PURPOSE:To hold a posture teaching a tool posture to a work by detecting the change of a distance from the work corresponding to the output value of a sensor, changing a profiling vector corresponding to this detected value, changing a tool posture vector and keeping the relative angle of the work and a tool in a fixed state. CONSTITUTION:When an interpolation moving distance at interpolation positions T3 and T4 in the case of teaching the start and end points of a work 1 is defined as lt and a change amount due to the distance sensor is defined as (h), an angle theta34 from the position T4 to the position T3 is the rotation of theta34=tan<-1> h/lt. Namely, the relative posture of the tool to the work 1 can be maintained by correcting the tool posture at a position T5 just for the rotation amount obtained at the positions T3 and T4. Next, the work is moved just for the lt in the direction of the corrected simulation vector, an angle theta45 is calculated from the change amount of the distance sensor and the lt at positions T4 and T5, and the posture of the tool at a position T6 can be calculated by further rotating the tool posture at the position T5 corresponding to the theta45.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a posture control method for a tool attached to the hand of an industrial robot.

[0002]

2. Description of the Related Art In an industrial robot, a distance sensor is attached near the tool attached to the hand of the robot, and the distance sensor detects the distance between the sensor and the work (in other words, the distance between the sensor and the tool). There is a so-called copying operation in which two points on a work are taught and a distance between the two points is moved while keeping this distance constant.

In this case, the tool posture is obtained by interpolating the starting point teaching posture and the ending point teaching posture of the tool, which is the teaching posture between two points, and the starting point and the ending point of the work 1 are shown in FIG. 4 (a). Are the same tool posture, the interpolation posture is also the same posture. In addition, as shown in FIG. 4B, when the starting point attitude and the ending point attitude change, the interpolation attitude gradually changes from the starting point attitude to the ending point attitude.

[0004]

In the method of determining the trajectory interpolation point posture by the above-described interpolation of the starting point teaching posture and the ending point teaching posture, it is said that the shape between the starting point and the ending point is constant. Not limited to this, the angle between the tool and the work may differ for each interpolation posture. Therefore, it cannot be said that the attitude of the tool with respect to the work is always constant.For example, in robot grinding with a grinder attached to the hand, there is a problem that the grinding accuracy is not constant and deteriorates due to different working angles of the grinder. Further, when the robot uses the plasma torch for the fusing, there is a problem in that the work cannot be stably fused due to a change in the thickness of the work.

In view of the above-mentioned problems, the present invention changes the tool attitude during the copying operation according to the correction amount in the copying direction so that the tool attitude at the trajectory interpolation point with respect to the workpiece matches the attitude at the teaching point. The purpose is to provide a posture control method.

[0006]

According to the present invention for achieving the above-mentioned object, when the industrial robot performs a copying control of a work by a sensor, the output value of the sensor is used to change the distance from the work. It is characterized in that the detection is performed, and the scanning vector is changed based on the detected value, and the tool posture vector is changed to maintain the relative angle between the work and the tool in a constant state.

[0007]

By changing the tool posture vector based on the change of the scanning vector due to the change of the shape of the work, the tool posture corresponding to the scanning direction can be obtained, and as a result, the tool posture based on the shape of the work can be obtained. It is possible to make the tool posture constant with respect to the work.

[0008]

EXAMPLES Examples of the present invention will now be described with reference to FIGS. FIG. 1 is an explanatory diagram of a copying vector and a tool posture vector with respect to the work 1, and the interpolation position T of FIG.
₃ and T ₄ are expanded. Also, FIG. 2 shows the interpolation position when teaching the starting point P ₁ and the end point P ₂ In the workpiece 1 so on _{T 1 T 2 T 3 T 4} ···.

In FIG. 1, it is assumed that the interpolation movement distance at the interpolation positions T ₃ and T ₄ is l _t . On the other hand, when the amount of change by the distance sensor is h, the position T ₄ is calculated by the following equation θ with respect to the position T ₃ .
₃₄ turns.

[0010]

[Equation 1]

That is, the tool relative attitude with respect to the work 1 can be maintained by correcting the rotation amount θ ₃₄ obtained at the positions T ₃ and T ₄ at the position T ₅ by rotating the tool attitude by θ ₃₄ . At this time, the scanning vector which is the moving direction vector during scanning control is also rotated by θ ₃₄ , and the position advanced by l _{t in} this vector direction is set as the next interpolation position T ₅ .

Next, by moving by l _t in the corrected scanning vector direction, the angle θ ₄₅ is calculated from the change amount of the distance sensor at the positions T ₄ and T ₅ and l _t, and at the position T ₅ . The tool posture is further rotated to match θ ₄₅ to obtain the tool posture at the position T ₆ and the scanning vector is obtained in the rotation angle θ ₄₅ direction.

Thus, the operations at the positions T _n and T _{n + 1} are sequentially repeated to determine the tool posture and the scanning vector.

By performing the copying control on the same work as the work 1 having the shape shown in FIG. 4 in this embodiment, a tool posture having a constant angle with respect to the surface of the work 1 can be taken as shown in FIG. it can. As an example, in the case of profiling a slope, once the profiling is performed on the sloping surface, the profiling vector direction coincides with the sloping surface, and there is no change in the distance sensor. You can move.

In the above embodiment, an example using a distance sensor is described. For example, a force sensor is attached to the 6-axis flange surface of the robot, a tool is attached to the tip of the force sensor, position control is performed in the advancing direction, and force is applied in the vertical direction. By converting the output value of the force sensor into a distance by hybrid control that performs control,
A force sensor may be applied to the copying control.

[0016]

As described above, according to the present invention, the work can be traced so as to hold the posture in which the tool posture with respect to the work is taught. For example, in grinding by a grinder, the contact angle between the grinder and the work is constant. Therefore, the tool action point of the grinder can be defined as one, and accurate grinding can be performed. Further, when a plasma torch is used as a tool to perform the fusing of the work, the change in the fusing thickness is small and stable fusing is possible.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the present embodiment at positions T ₃ and T ₄ .

FIG. 2 is an explanatory diagram of interpolation from a start point to an end point.

FIG. 3 is an explanatory view of a tool posture.

FIG. 4 is an explanatory view of a conventional tool posture.

[Explanation of symbols]

 1 work 2 tool

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B25J 9/22 G05B 19/403 C 9064-3H

Claims (1)

[Claims] 1. When performing a copying control of a work by a sensor in an industrial robot, a change in the distance to the work is detected by the output value of the sensor, and the copying vector is changed by the detected value. A tool posture control method for changing a tool posture vector to maintain the relative angle between the work and the tool in a constant state.