JPH11333776A - Assembly hand - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the limit on the outer dimension of a small-sized work to be handled. SOLUTION: This assembly hand comprises a plurality of rotary shafts 13 arranged on the same circumference, a drive part to transmit the rotation to the rotary shafts 13, an arm 15 fixed to each rotary shift 13, and a chucking member 16 provided on a tip of each arm 15 and projected in the axial direction of the rotary shifts 13. The chucking member 16 can be moved not only to the inner circumferential side of the circumference where the rotary shafts 13 are arranged, but also to its outer circumferential side, and the limit of the outer dimension of a work to be held is small. Each chucking member may be driven only by rotating each rotary shaft.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembly hand for gripping a workpiece in an assembly robot or the like.

[0002]

2. Description of the Related Art Various types of assembling hands, which are called manipulators for holding a work in an assembling robot or the like, are provided in various types. In many cases, a workpiece is gripped by contacting a plurality of (usually three) chuck members with the outer surface.
Japanese Patent Publication No. 25881 discloses an arrangement in which a plurality of chuck members that perform linear movement are arranged such that their movement paths are radial.

[0003]

In this case, there are many restrictions on the external dimensions of the work that can be gripped, and if the restrictions are reduced, the size of the assembly hand becomes considerably large.

[0004] In addition, a conventional assembly hand which is of an air type cannot cope with a flexible work having a constant gripping force, and an electric type hand which cannot control the gripping force only by positioning control. Therefore, an assembly hand that performs appropriate gripping force control is desired. Of course, there are also provided those capable of controlling the gripping force, but these use a force sensor such as a strain gauge to detect the force, and have a problem that calibration is complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an assembling hand which has a small size and can be adapted to a small work size. Another object of the present invention is to provide an assembling hand capable of performing suction and appropriately controlling gripping force.

[0006]

According to the present invention, there is provided an assembling hand comprising a plurality of rotating shafts arranged on the same circumference, a drive unit for transmitting rotation to these rotating shafts, It is characterized by comprising a fixed arm and a chuck member provided at the tip of each arm and protruding in the axial direction of the rotating shaft.

Since the chuck member can be moved not only to the inner circumferential side of the circumference on which the rotating shaft is arranged but also to the outer circumferential side, the outer dimensions of the work that can be gripped are limited only slightly. In addition, the driving of each chuck member only needs to rotate each rotating shaft.

If the chuck member here has a suction pad at its tip, the work can be held by suction. In addition, the chuck member has a hollow structure and the inside serves as an air flow path to the suction pad,
If the rotary shaft is a hollow shaft and the inside is an air flow path leading to the suction pad, the labor for piping can be reduced.

It is preferable that the control unit includes a control unit for performing NC control on the drive unit. The control unit controls the speed of the drive unit until the chuck member comes into contact with the work. A device that controls the torque of the drive unit after the contact can be suitably used.

Switching between speed control and torque control is performed based on the motor current in the drive unit, and switching between speed control and torque control is performed based on the integral value of the deviation speed calculated from the encoder of the drive unit and a preset threshold value. The control can be switched by detecting the contact of the chuck member with the work without using a force sensor. In addition, when the control unit performs the speed control up to the contact of the work with a target value calculated from the target torque at the time of gripping the work by the chuck member, the control unit can suppress overshoot when the chuck member comes into contact with the work. it can.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an example of an embodiment. FIG. 4 shows an assembly hand 1 according to the present invention.
1 shows an NC-controlled four-degree-of-freedom type assembly robot R provided with a robot. The assembly hand 1 provided on the robot R cooperates with an assembly table 2 having two degrees of freedom to form a six-degree-of-freedom assembly robot. The assembly work is done.

The assembling hand 1 grips a workpiece by using a forward / reverse rotatable motor (pulse motor) 10 disposed at the center thereof as a power. The output shaft of the motor 10 supported by a frame 11 has A gear 12 is attached. The frame 11 supports three rotating shafts 13 at equal intervals on a circumference centered on the motor 10, and a gear 14 and an arm 15 meshing with the gear 12 are fixed to each rotating shaft 13. I have. A chuck member 16 is attached to the tip of each arm 15 so as to protrude in the axial direction of the rotating shaft 13.

If the motor 10 is rotated in one direction, the rotating shafts 13 rotate in the same direction as shown in FIG. 3 by the engagement of the gears 12 and 14, and the motor 10 is rotated in the opposite direction. In this case, each rotation shaft 13 also rotates in the opposite direction. Here, the arm 15 on a certain rotating shaft 13 is
When heading toward the center which is the axis of the other two rotation shafts 13
Are also set so as to face the center side, the distance between the three chuck members 16 and the center changes simultaneously and simultaneously by the rotation of the motor 10, so that the chuck members The work 16 can be gripped by the work. In addition, since the chuck member 16 is capable of gripping the work even at a position located on the outer peripheral side of the circumference where the rotary shafts 13 are located, the outer dimensions of the work that can be gripped while being small are described. The restrictions are small.

Further, the chuck member 16 in the illustrated example has a suction pad 4 whose end face is urged by a spring 40 in a protruding direction.
The work can be held even by suction by the suction pad 4 of each chuck member 16. It should be noted that the air flow path 41 reaching the suction pad 4
Passes through the center of the chuck member 16 having a hollow structure and the inside of the rotary shaft 13 which is a cylindrical shaft, and a flow path to the suction pad 4 is secured regardless of the rotation of the rotary shaft 13 and the arm 15. It has become so.

FIG. 5 is a block diagram showing the drive control of the assembling hand 1. In the figure, 5 is an arithmetic unit, 6 is a motor 1
0 is a driver, and 19 is an encoder attached to the motor 10.
The motor 10 is driven on the basis of a speed command or a torque command sent to the driver 6 through the D / A converter through the D / A converter. And the motor drive current value is A /
It is sent to the control program 50 through the D converter. Here, those corresponding to the case of holding the work by suction are not shown.

Here, both the speed command and the torque command are provided because the operation control until the chuck member 16 contacts the work and the operation control after the contact with the work are different. Because it is. That is, FIG.
As shown in FIG. 5, the motor 10 is driven by the speed control until it is determined that the chuck member 16 has come into contact with the work, and the motor 10 is driven by the torque control after it is determined that the chuck member 16 has come into contact with the work. The chuck member 16 is quickly moved until the workpiece comes into contact with the workpiece, but after contacting the workpiece, the gripping force is controlled so that the workpiece can be handled even if the workpiece is a flexible object.
When the workpiece is held by suction, position control is performed as shown in FIG.

The determination as to whether or not the chuck member 16 has come into contact with the work is performed using the motor current i as shown in FIG. That is, if the motor current i exceeds the predetermined current value imax, the chuck member 1
6 is determined to be in contact. That is, contact information can be obtained without using a force sensor such as a strain sensor.

Instead of the contact detection based on the motor current i, as shown in FIGS. 8 and 9, the integral value of the deviation speed EV calculated from the encoder 19 is set to a predetermined threshold value Sde.
Switching from speed control to torque control may be performed depending on whether or not the speed exceeds st. Also in this case, contact information can be obtained without using a force sensor.

Further, as shown in FIG. 9, if the speed calculated from the input target torque at the time of gripping is set to the target value Sdest, as shown in FIG. Since an appropriate approach speed can be obtained, overshoot when the chuck member 16 contacts the work can be reduced.

The speed target value according to the target torque is:
For example, the former is 4 m / s if 4N, 3.6 m / s if 6N, 3.0 m / s if 10N, 2.4 m / s if 15N, 1.8 m / s if 20N. This may be incorporated in the control program 50 as a data table in advance. Responsiveness can be improved as compared with the case where it is obtained by calculation.

[0021]

As described above, the assembling hand according to the present invention has a plurality of rotating shafts arranged on the same circumference, a drive unit for transmitting rotation to these rotating shafts, and fixed to each of the rotating shafts. Since the arm and the chuck member provided at the tip of each arm and protruding in the axial direction of the rotating shaft, the chuck member extends not only to the inner circumferential side of the circumference where the rotating shaft is arranged but also to the outer circumferential side. Since it can be moved, the external dimensions of the work that can be gripped are small, and it is possible to cope with a variety of works. Only need to be rotated, and it is structurally simple and inexpensive.

If a suction pad is provided at the tip of the chuck member, the work can be held not only by gripping but also by suction, so that a variety of works can be handled. Also, if the chuck member has a hollow structure and the inside is an air flow path to the suction pad, or if the rotation shaft is a hollow shaft and the inside is an air flow path to the suction pad, the piping can be simplified, Piping does not hinder assembly work.

It is preferable that the control unit is provided with a control unit for performing NC control on the drive unit. The control unit controls the speed of the drive unit until the chuck member comes into contact with the work, and the chuck member is connected to the work. A device that controls the torque of the drive unit after the contact can be suitably used. By using such a control unit, it is possible to respond quickly to a workpiece made of a flexible material.

Switching between speed control and torque control is performed based on the motor current in the drive unit, and switching between speed control and torque control is performed based on the integral value of the deviation speed calculated from the encoder of the drive unit and a preset threshold value. If the comparison is made without using a force sensor, the control can be switched by detecting the contact of the chuck member with the work, and the reliable operation can be obtained because the calibration is simple. .

Further, the control unit performs speed control up to the contact of the work with a target speed calculated from a target torque at the time of holding the work by the chuck member as a target value. Thus, it is possible to prevent the work from being damaged or the chuck member from being damaged.

[Brief description of the drawings]

FIG. 1 is a perspective view of an example of an embodiment of the present invention.

FIG. 2 is a schematic sectional view of the same.

FIG. 3 is a front view of the same.

FIG. 4 is a perspective view of an assembly robot provided with the above assembly hand.

FIG. 5 is a block circuit diagram of a control unit according to the first embodiment;

FIG. 6 is an operation explanatory view of the above.

FIG. 7 is an operation explanatory diagram of another example of the above.

FIG. 8 is an operation explanatory diagram of still another example of the above.

FIG. 9 is a time chart for the operation of the above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Assembly hand 10 Motor 13 Rotation axis 15 Arm 16 Chuck member

Claims (9)

[Claims] 1. A plurality of rotating shafts arranged on the same circumference, a drive unit for transmitting rotation to the rotating shafts, arms fixed to the rotating shafts, and a plurality of rotating shafts provided at the tip of each arm. An assembly hand, comprising: a chuck member protruding in the axial direction of the shaft. 2. The assembly hand according to claim 1, wherein the chuck member has a suction pad at a tip thereof. 3. The assembling hand according to claim 2, wherein the chuck member has a hollow structure and the inside thereof serves as an air flow path leading to the suction pad. 4. The assembly hand according to claim 2, wherein the rotating shaft is a hollow shaft and the inside is an air flow path leading to the suction pad. 5. The assembly hand according to claim 1, further comprising a control unit for performing NC control on the driving unit. 6. The control unit controls the speed of the drive unit until the chuck member contacts the work, and controls the torque of the drive unit after the chuck member contacts the work. 5. The assembly hand according to 5. 7. The assembly hand according to claim 6, wherein the control unit switches between speed control and torque control based on a motor current in the drive unit. 8. The control unit switches between speed control and torque control by comparing an integral value of a deviation speed calculated from an encoder of the drive unit with a preset threshold value. 6. The assembly hand according to 6. 9. The control unit controls the speed until the workpiece contacts.
The assembly hand according to any one of claims 6 to 8, wherein a speed calculated from a target torque when the workpiece is gripped by the chuck member is used as a target value.