JPS63156678A - Grasped object tilt correction method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Summary] The present invention is a robot that is used in assembly work to determine the relative position of objects to be assembled with high precision. The hand that grips the object is equipped with a force sensor that detects the falling of the object, and the actuator that moves slightly in the X and Y directions is corrected to minimize the output of the force sensor caused by the falling of the object. be.

[Industrial application field]

The present invention relates to industrial robots, and particularly to a method for correcting the inclination of an object gripped by a robot.

Robots are widely used in the industrial field.

The work performed by these robots continues to become more accurate and faster. Along with this, various methods have been adopted to improve the positioning accuracy of robots. However, in assembly work, it is often difficult to assemble with high precision simply by improving the positioning degree M. In particular, there is a need for a method for correcting the inclination of a grasped object that can efficiently correct the inclination of an object grasped by a robot.

[Conventional technology]

As a solution to high-precision relative positioning in robots, a wrist structure has been proposed in which the hand can be displaced with respect to the arm using a compliance mechanism to absorb relative positional deviations between objects to be assembled. However, this also has the problem that if the combination is increased in an attempt to increase the ability to absorb relative positional deviations, the force in the insertion direction during fitting work will also be weakened. A robot of No. 59-59389 has been proposed.

This robot is equipped with a compliance mechanism,
When conveying a fitted object, the compliance is made variable so that smooth position control can be achieved by increasing the compliance, and high precision positioning is possible.

[Problem that the invention seeks to solve]

As described above, conventional robots are capable of highly accurate positioning, but there is a problem in that highly accurate positioning becomes impossible if the gripped object falls down within the hand.

It is an object of the present invention to provide a method for correcting the inclination of a grasped object, which corrects the inclination of a grasped object from the above-mentioned conventional situation and also enables highly accurate positioning.

[Means for solving problems]

As shown in the principle diagram of FIG. 1, this invention consists of an arm 1 that is coarsely driven, an actuator 2 that makes fine movements connected to this arm 1, and a force sensor 5 attached to the actuator.
The robot consists of a hand 3 connected to the other end of the force sensor, and a control system 6 for controlling these.

[Effect]

The hand 3 is driven to slightly lower the gripped object 4, and the force sensor 5 detects the minute force generated by this fall, and the control system 6 controls the fine movement actuator 2 so that this detected value is reduced to a required value. , correct the tilt of the object.

〔Example〕

FIG. 2 is a schematic diagram of an embodiment for explaining a tilt correction method for a gripped object according to the present invention. The arm 1 that is finely driven is pivotally supported by the main shaft 1-1 via the arm 1-2, and the arms 1-2.1 rotate in the directions shown by the arrows. Therefore, the tip A of the arm 1 is driven onto a horizontal plane. A compliance mechanism (hereinafter referred to as VACOM) that serves as an actuator with a pillar 1-3 rotatably supported on this tip A and micro-driven by this pillar 1-3.
2 are connected. This VACOM 2 has a force sensor 5
It has a structure in which the hand 3 is connected via.

This VACOM 2 was used in Japanese Patent Application Laid-Open No. 59-59389, and to put it simply, in VACOM, the ease with which the movable part deforms in the X and Y directions relative to the fixed part can be changed in several stages. A mode that is difficult to deform, that is, a mode with high rigidity, means that it is difficult to deform from a certain displacement state. That is, to generate a predetermined displacement in this highly rigid mode, a voltage is applied to the planar DC motor built into the VACOM.

In other words, when a voltage is applied to the X and Y electrodes of the VACOM, there is a slight movement (X) with two degrees of freedom in the X and Y directions.

It operates as an actuator with a movable range of ±1.0 mm in the Y direction. For example, if a voltage of ±10V is input through an A/D converter divided by 12 bits, fine movement control of about 1 μm can be achieved.

The force sensor 5 connected to this VACOM 2 has a structure shown in FIG. 3, and has a thickness of 0.1 mm and a width of 10 mm.
.

Parallel spring plate made of stainless steel with a length of 14 mm 5-1.5-
It is composed of 2. These two pairs of parallel spring plates 5-1.
5-2 receives forces in two degrees of freedom without interference from forces applied in the X and Y directions due to deflection, making it possible to detect forces.

Two resistance foil strain gauges 5-3 and 5-4 are attached to the surfaces of the four parallel spring plates 5-1 and 5-2, respectively. Therefore, a four-terminal bridge circuit is constructed with the resistance foil strain gauges 5-3 and 5-4, and the force applied to the parallel springs in the Measure.

For example, if the object 4 to be raised is a raw egg, the hand 3
The detection resolution of the force applied was 100 mg force.

The control system 6 controls the above-described mechanical parts, and the control system 6 includes an amplifier 6-1.6 that amplifies the output of the four-terminal bridge circuit generated in the force sensor 5.
-2, a low pass filter (LPF) 6-3.6-4 that removes noise components from the output of the amplifier, and a
Converter 6-5, processing unit (CPU) 6-6, keyboard 6-7, display device (CRT) 6-8 and 12-bit digital value to analog value. and a D/A converter W6-9.

Note that the operation of the present invention will be explained using the flowchart shown in FIG. The explanation will be based on the assumption that the object is a raw egg. First, ■
In the process, the robot grasps a raw egg. Next, move the arm to the specified position ■.

When the movement of the raw egg is completed, in step (2), spread the hand less than 1.0 mm from the grasped state to free the raw egg. If the raw egg falls over, force will be applied to the fingers of the hand. This power ■
It is detected in the process of

Next, in step (2), the control system 6 detects whether the above-mentioned detected force is within the coarse movement range, that is, for example, ±4 g force or less. If it is not below, coarse movement control is performed to move the arm 1 in step (2).

Repeat ① force detection and ② force detection in coarse movement range.

If the result is that the force is below the coarse movement range, it is detected in step (2) whether the force is below the fine movement range, that is, 100n+g force. If it is not 100 mg m or less, the actuator 2 is driven in step (2) to perform fine movement control. This has a force of 100m
Repeat until the weight is below g. If the force becomes less than 100 mg m after repeated attempts, the correction of the fall has been completed.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the tilting of a grasped object can be corrected with a simple configuration of attaching a force sensor, which is extremely effective in controlling the position of a robot with high precision. demonstrate.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram showing the method for correcting the tilt of a gripped object according to the present invention. FIG. 2 is a schematic diagram of an embodiment for explaining the method for correcting the tilt of a gripped object according to the present invention. FIG. FIG. 4 is a perspective view showing the structure of the force sensor, and FIG. 4 shows a flowchart for explaining the present invention in detail. In the figure, 1 is the arm, 2 is the VACOM, 3 is the hand, 4 is the object, 5 is the force sensor, and 6 is the control system
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Claims (1)

[Claims] An arm (1) that is subject to coarse movement control, and an actuator (2) that is connected to the arm (1) and that is subject to fine movement control in the XY directions.
and a hand (3) that is connected to the actuator (2) and grips an object (4), in which the hand (3) is connected in the XY direction between the actuator (2) and the hand (3). A force sensor (5) that detects the force applied to
), the actuator (2) is controlled so as to widen the grasping width of the hand (3) and minimize the minute output of the force sensor (5) caused by the falling of the object, thereby preventing the object from falling. A method for correcting the inclination of a grasped object.