JPH04183590A - Holding device - Google Patents

Abstract

PURPOSE:To perform the adjustment of a holding force electrically wholely, and to simplify the structure of a servohand part, by providing a changeover means which can connect a torque control means only with a position control means and speed control means being cut-off from a servomotor. CONSTITUTION:In the case of holding an object by a holding mechanism, a position control means 6, speed control means 5 and torque control means 4 are first connected to a servomotor 2 altogether, and the object is held by a holding mechanism while performing the controls by the respective control means 4, 5, 6. Thereafter, the holding force for the object is kept in the specified value with the torque control only by the torque control means 4 being executed by changing over a switching means 8. Consequently, the adjustment of the holding force can be executed electrically altogether.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gripping device, and particularly to a mechanism for adjusting the gripping force on an object.

[Prior Art] As a conventional gripping device of this type, a servo hand for a robot shown in FIG. 3 can be mentioned.

FIG. 3 is a conceptual diagram of a conventional robot robot.

In the figure, (11) is a pair of opening/closing members whose position is controlled by a servo motor (not shown), (12) is a gripping member supported by both opening/closing members (11) via compression springs (13), and (W ) is the work.

Next, the operation of the conventional robot servo hand configured as described above will be explained.

When the gripping members (12) are positioned on both sides of the workpiece (W) and the opening/closing members (11) are brought close to each other by the servo motor, the gripping members (12) are held in a state where the compression spring (13) is bent. A workpiece (W) is gripped. The gripping force at this time is generated by the elastic force of the compression spring (13), and the narrower the interval between the opening and closing members (11), the more the compression spring (
13) becomes larger, and the gripping force on the workpiece (W) also becomes larger. Therefore, the teaching points of both opening/closing members (11) are changed to adjust the gripping force on the workpiece (W) to an arbitrary value. Therefore, workpieces of different sizes (
When gripping the workpiece (W), both opening and closing members (11) are aimed at the teaching point corresponding to the size of the workpiece (W).
to control the position.

grips the workpiece (W).

This type of servo hand for robots was developed in
It is publicly known from Publication No. 956 and the like.

[Problems to be Solved by the Invention] Conventional robot servo hands are configured to generate gripping force using the elastic force of the compression spring (13) as described above. ) is indispensable, and the structure of this servo hand portion is mechanically complex and expensive, and its reliability is insufficient.

Therefore, an object of the present invention is to provide a gripping device that has a simple mechanical structure, can be manufactured at low cost, and can significantly improve reliability.

[Means for Solving the Problems] A gripping device according to the present invention is one in which a servo motor that drives a gripping mechanism is controlled by a position control means, a speed control means, and a torque control means, in which the servo motor is controlled by a switching means. Only the torque control means can be connected to the motor.

[Operation] In the present invention, when gripping an object with the gripping mechanism, first, the position control means, the speed control means, and the torque control means are all connected to a servo motor, and the control is performed by each control means. The gripping mechanism grips the object, and then the switching means is switched to perform only torque control by the torque control means to maintain the gripping force on the object at a predetermined value, so all adjustment of the gripping force is performed electrically.

[Example code] The present invention will be explained in detail below.

FIG. 2 is a conceptual diagram of a servo hand for a robot according to an embodiment of the present invention.

In the figure, (1) is a pair of opening/closing members as a gripping mechanism whose position is controlled by a servo motor (2), (3) is a gripping member supported by both opening/closing members (1), and (W)
is the work.

FIG. 1 is a block diagram showing the electrical configuration of a servo hand for a robot.

In the figure, (4) is current control as a torque control means that controls the rotational torque of the servo motor (2), that is, the opening/closing torque of the opening/closing member (1) based on a position command signal from a main control circuit (not shown). The circuit (5) is a speed control circuit (6) as a speed control means for controlling the rotational speed of the servo motor (2), that is, the opening/closing speed of the opening/closing member (1) based on the position command signal from the main control circuit. ) is a position control circuit as a position control means that controls the rotation angle of the servo motor (2), that is, the opening/closing position of the opening/closing member (1) based on a position command signal from the main control circuit. These control circuits (4) to (6) perform feedback control based on pulse signals from encoders and current sensors.

The above configuration is exactly the same as that of a general known servo hand, and next, particularly, the characteristic parts of the servo hand of this embodiment will be explained.

(7) is a torque/current conversion circuit that converts a torque command signal from the main control circuit into a corresponding current value; (8) is a switching control circuit that is controlled by the main control circuit;
on the speed control circuit (5) side or the torque/current conversion circuit (
7) is a changeover switch serving as a changeover means for selectively connecting to either of the above.

Next, the operation of the robot servo hand of this embodiment configured as described above will be explained.

The robot executes work based on a work program manually entered in advance using a teaching device, and in the process of grasping the workpiece (W) being worked on, the changeover switch (8) in the main control circuit is set to the speed control circuit (5) side. can be switched to Then, based on the position command signal from the main control circuit, the position control circuit (6
), the rotation angle of the servo motor (2) is determined by the speed control circuit (
In step 5), the rotational speed and the rotational torque are respectively feedback-controlled by the current control circuit (4), and the opening/closing members (1) are moved in the approach direction while controlling the position to grip the workpiece (W).

Furthermore, after gripping the workpiece, a changeover switch (8
) is switched to the torque/current conversion circuit (7) side at a predetermined timing. Therefore, the torque value based on the torque command signal from the main control circuit is
The current control circuit (4) only controls the rotational torque of the servo motor (2), and the workpiece (W) is gripped by both opening/closing members (1) with a predetermined gripping force.

As described above, the switching timing of the changeover switch (8) when transitioning from normal position control to torque control and the torque value in torque control can be arbitrarily set in advance by the teaching device. Therefore, workpieces of different sizes (W
), the switching timing corresponding to the size of the work (W) and the torque value corresponding to the weight of the work, etc. are inputted in advance by the teaching device.

In this way, the robot servo hand of the above embodiment is
A servo motor (2) that drives an opening/closing member (1) for gripping a workpiece (W), a position control circuit (6) that controls the position of the servo motor (2), and a position control circuit (6) that controls the position of the servo motor (2). A speed control circuit (5) that performs speed control, a current control circuit (4) that performs torque control of the servo motor (2), and a position control circuit (6) and a speed control circuit for the servo motor (2). (5) can be disconnected and only the current control circuit (4) can be connected to the changeover switch (7).
).

Therefore, while controlling the servo motor (2) by all the control circuits (4) to (6), the opening/closing member (1) is used to control the workpiece (W).
), and then, by switching the changeover switch (7) and performing only torque control by the current control circuit (4), the gripping force for the workpiece (W) can be maintained at a predetermined value.

Since the gripping force is all adjusted electrically in this way, there is no need to provide a mechanical structure for adjusting the gripping force, such as a compression spring, and the structure of the servo hand part is is simplified and can be manufactured at low cost, and its reliability can be greatly improved.

By the way, although the above embodiment is configured as a servo hand of an industrial robot for grasping a workpiece (W), when implementing the present invention, the present invention is not limited to this, and it is possible to It may be anything as long as it is something for gripping.

Further, although the torque/current conversion circuit (7) in the above embodiment is configured to input a torque command signal manually from the main control circuit, any parameter can be used as long as it is a parameter for controlling the torque of the servo motor (2). good.

[Effects of the Invention] As described above, the gripping device of the present invention includes a servo motor that drives a gripping mechanism for gripping an object, a position control means, a speed control means, and a torque control means that respectively control the servo motor. and a switching means that can disconnect the position control means and the speed control means from the servo motor and connect only the torque control means, so that the gripping mechanism can control the object while controlling each control means. After gripping an object, by switching the switching means, only the torque control by the torque control means is performed, and the gripping force on the object is maintained at a predetermined value.Since all gripping force adjustments are made electrically, the gripping force can be reduced. There is no need to provide a mechanical structure for adjusting the servo hand, and the structure of this servo hand part can be simplified and manufactured at low cost, and reliability can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the electrical configuration of a robot servo hand according to an embodiment of the present invention, FIG. 2 is a conceptual diagram of a robot servo hand according to an embodiment, and FIG. 3 is a conceptual diagram of a conventional robot servo hand. It is a diagram. In the figure, opening/closing member 2: Servo motor 4: Current control circuit (torque control means) 5: Speed control circuit (speed control means) 6: Position control circuit (position control means) 8: Changeover switch (switching means) W: It is a work (object). In the drawings, the same reference numerals and the same symbols indicate the same or equivalent parts. Agent: Patent attorney Masuo Oono and 2 others

Claims (1)

[Scope of Claims] A servo motor that drives a gripping mechanism for gripping an object; a position control means that controls the position of the servo motor; a speed control means that controls the speed of the servo motor; A gripping device comprising: a torque control means for controlling the torque of a motor; and a switching means capable of separating the position control means and speed control means from the servo motor and connecting only the torque control means.