JPH01210285A - Robot hand having grappling force detecting function - Google Patents

Abstract

PURPOSE:To grapple a work stably without any deformation thereof along the configuration of the work by means of adequate grappling force by attaching work grappling pressure receiving boards on the inner sides of fingers via angle- shaped leaf springs movably against the fingers and installing a pair of strain ganges on each leaf spring. CONSTITUTION:When fingers 6 move in their closing directions due to the rotation of a worm 20, pressure receiving boards 10 touch a work 8. As the fingers close farther, the leaf springs 12 are subjected to elastic deformation to grapple the work 8 with a small grappling force caused by the deformation. Simultaneously this grappling force is detected by each strain gange 14 installed on each leaf spring 12. When this grappling force is increased to a large grappling force beyond a load value necessary for having either one of screws 24 and the spacer 26 facing thereto brought in contact with each other, while said screw 24 and spacer 26 being used for linking the pressure receiving board 10 to the finger 6 movably through the leaf spring 12, the existent high grappling force is detected by means of each stain gange 4 located on the root of each finger.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to the structure of a finger of a robot hand that grasps and releases a grasped object (hereinafter abbreviated as "t work"). The present invention relates to a robot hand that has a function of gripping a workpiece by a pressure receiving plate movably attached via a plate spring having a pair of strain gauges (also referred to as strain gauges) inside the hand, and detecting the gripping force.

[Conventional technology]

A robot hand that grasps and releases an object by opening and closing a pair of fingers is, when grasping multiple types of workpieces of different sizes and shapes, handling by a robot hand made with a fixed finger opening and closing width. Excessive force may be applied to the workpiece, causing damage or deformation of the workpiece. To prevent this, a robot hand has been created that detects the gripping force and controls the gripping force so that it does not exceed the desired gripping force. 5 to 9 are diagrams showing conventional examples of this type of robot hand, in which FIG. 5 is a side view showing the structure, and FIGS. 6 to 9 are side views showing a state in which a workpiece 8 is gripped. It is.

In FIG. 5, a pair of fingers 7.7 are connected to shafts 16,
It can be freely rotated about the shaft 16 as the center of rotation.

A worm wheel 18.18 is fixed to the shaft 16.16, and a worm 20 is engaged with the worm wheel 18.18. A small thick part 22.22 is provided near the root of the finger 7.7, and each strain cage 4 is provided in this small thick part 22.22.
It is equipped with

In the above configuration, when the worm 20 is rotated by an actuator of a robot (not shown),
Worm car 18. Axis 16. The fingers 7 rotate as a body around the shaft 16, and the fingers 7.7 open and close. When the fingers 7.7 close and grip the workpiece 8, as shown in FIG. The gripping force is detected through the electric circuit device shown in FIG. Control.

[Problems to be Solved by the Invention] When the workpiece 8 is reliably gripped by the conventional example described above,
It is necessary to provide the fingers 7.7 with a certain degree of rigidity, and for this reason, the closing speed of the fingers 7.7 indicated by the arrows V and V in FIG.
．． In order to prevent the hinge 8 from being damaged or deformed by the impact when it contacts the workpiece 8, it is necessary to set a low closing speed v, v, which slows down the gripping operation.

In addition, when gripping a workpiece 8a with a rectangular cross section, as shown in FIG. 7, since the fingers 7.7 have high rigidity, there are only two contact points between the soak 8a and the fingers 7.7, making it extremely unstable. It becomes a grip.

Further, as shown in FIG. 8, from the strain gauge 4 to L,
The soak 8b at a distance of 1. and the workpiece 8 at a distance of I72 are grasped by which part of the fingers 7.7. It is not possible to accurately detect the position of L2 and L2, and positioning cannot be performed in this state, so it cannot be applied to insertion or assembly work. For this purpose, a grip position detection device and a positioning device are required.

Furthermore, as shown in FIG. 9, if the workpiece 8d is very soft relative to the finger 7.7, the conventional finger 7.7 may be used.
7C has a low sensitivity of the strain gauge 4 and deforms the workpiece 8d before grasping and detecting the workpiece 8d, so this type of finger 7.7 cannot be used.

The present invention is a Ropont Hunt that can quickly perform gripping operations, perform versatile and stable gripping regardless of the shape, size, and hardness of the workpiece, and can detect the gripping point. The challenge is to submit ′ to (.

[Failure to solve the problem]

In order to solve the above problems, according to the present invention, a pair of fingers are opened and closed to grasp and release an object to be grasped, and a pair of strain gauges are provided in a small thickness section provided near the base of the fingers. In a robot hunt equipped with Each leaf spring is equipped with a pair of strain gauges and has a gripping force detection function.

[Effect]

According to the present invention, a pressure receiving plate is attached to the inside of each of a pair of fingers to grip a workpiece via a dogleg-shaped leaf spring whose both ends are bent at an acute angle, so as to be movable relative to the fingers. Therefore, regardless of the shape, size, hardness, etc. of the work, it is possible to grip the work in a versatile and stable manner by opening and closing the fingers, and it is possible to quickly grip the work without applying an impact to the work. Furthermore, since the leaf spring is equipped with a pair of strain gauges, the gripping force when gripping a workpiece is detected via an electric circuit device, and the desired gripping force is adjusted according to the workpiece to be handled. can be controlled.

Furthermore, the gripping point of the workpiece can be calculated from the total amount of strain in the leaf spring to which the pressure receiving plate is attached.

(Embodiment) An embodiment of the present invention will be explained with reference to FIGS. 1 to 4. 1U; jI is a side view showing the structure, and FIG. □ shows a deformed state. The third section shows a circuit diagram of the electric circuit device of the strain gauge 4°14. The fourth section V shows the principle of detecting the gripping point C of the workpiece 8.

The robot hand 2 of the present invention has a structure in which a pressure receiving plate 10 is attached via a leaf spring 12 to the inside of a pair of fingers 6.6 of the conventional robot hand shown in FIG. In other words, in FIG. 1, a pair of fingers [j, 6 is a shaft 16.1
6, and can freely rotate around the shaft 16. A worm wheel 18.18 is fixed to the shaft 16.16, and a worm 20 is engaged with the worm wheels 18, 18. Near the root of the finger 6.6 there is a small thickness section 22.22, each of which is provided with the aforementioned strain gauge 4.4. When the worm 20 is rotated by an actuator of a robot (not shown), the worm wheel 181 . Axis 16. The fingers 6 rotate together about the shaft 16, and the fingers 6.6 open and close.

Pressure received to grip the workpiece 8 inside the fingers 6, 6 +1i
10.10 is movably moved relative to the finger 6.6 by a screw 24. It is attached with a spacer 26. The leaf spring 12 is also provided with a pair of strain gauges 14 on both sides of each spring piece as shown.

FIG. 3 shows a circuit diagram of the electric circuit device of the strain gauges 4, 14. A pair of four strain gauges 4, 14 each form a, b, c, and d in the figure. A Wheatstone bridge 28 shown by and surrounded by a broken line is constructed, and this Wheatstone bridge 28 consists of one set (28a) of 4 i+r+ strain gauges 4, and four strain gauges 14 for each leaf spring 12, each of which has one set (28a). Total of 4 groups (28b, 28
c, 28d, 28e) are configured, and are supplied with power from a power supply 30, and a signal is output according to the distortion of each part, amplified by amplifiers 32a to 32e, inputted to a multiplexer 34, and is The selected signal is input to the computer 38 via the A/D converter 36.

Handling work by the robot hand 2 of the present invention having the above-mentioned configuration will now be explained with reference to FIGS. 1 to 4.

(1) Drive the worm 20 in one direction and move the finger 6
．． 6 and move the robot hunt 2 to a position where it can grip the workpiece 8.

(2) Drive the worm 20 in the opposite direction to move the fingers 6.
6 will be closed.

(3) When the pressure plate 10.10 comes into contact with the workpiece 8 and the fingers 6.6 further close, the leaf spring 12 is elastically deformed, and the pressure plate 10 grips the workpiece 8 with the resulting low gripping force. At the same time, the strain gauge 14 provided for each leaf spring 12 detects the gripping force as explained in FIG. A command is issued from the computer 38 to detect the outputs of the Wheatstone bridges 28b to 28e of the strain gauges 14 provided in each part of the leaf spring 12.

(4) Next, as shown in FIG. 2, the leaf spring 12 is in a deformed state, and the maximum load detection value, which is the load value necessary for the screw 24 and the spacer 26 to come into contact, is preliminarily set. When gripping with a load value exceeding this value, the Wheatstone bridge of the strain gauge 4 at the base of the finger 6 is
The multiplexer 34 switches the signal to the signal output from the output terminal 28a and performs -ζ control. As described above, by controlling the gripping of the workpiece 8 using the robot hunt 2 of the present invention, highly accurate gripping control can be achieved from the low gripping force by the strain gauge 14 of the leaf spring 12 to the gripping force by the strain gauge of the finger 6. 4
The high gripping force allows for high gripping.

(5) The robot hand 2 grasps the workpiece 8 and generally feeds it to a desired position, drives the worm 20 in one direction to open the fingers 6.6, and releases the workpiece 8 to that position, The empty robot hand 2 is again moved to the position where it will grip the next workpiece 8, and the handling operations from (2) above are repeated.

FIG. 4 shows the principle of detecting the gripping point C of the workpiece 8, and only one side of the pair of fingers 6 is shown.
Actually, there are also fingers 6 on the side which is not shown, and they both grip the workpiece 8.

In FIG. 4, the pressure receiving plate 10 has a length AB-! and
The left end A is attached to the finger 6 via a leaf spring 12a, and the right end B is attached to the finger 6 via a leaf spring 12b. Left end A and gripping point C
Assuming that the distance to is 11, h can be calculated using the following equation.

ε^'' - ε8 Here, ε: Total strain amount of the leaf spring 12a εR: Total strain of the leaf spring 12b Wheatstone bridge 28b by the strain gauge 14 of the leaf spring 12a and Wheatstone bridge 28c by the strain gauge 14 of the leaf spring 12b are individually configured as explained above, so ε7. ε8, etc. can be detected independently, and h can be calculated by computer 3H.
is required.

According to the robot hand 2 of the present invention, the following problems can be solved.

(b) In the conventional example explained in FIG.
Since the workpiece 8 is gripped by the pressure receiving plates 10, 10 attached via 2, the workpiece 8 can be soft-touched by the pressure receiving plates 10, 10 even if the closing speed v, v is increased. can be done quickly.

(b) Regarding the extremely unstable grip in the conventional example as explained in FIG.
Since it deforms and maintains its balance, the workpiece can be stably gripped by surface contact.

(c) Regarding the fact that the gripping position of the workpiece 8 is unknown in the conventional example as explained in FIG. 8 above, the position of the gripping point C can be calculated as explained in FIG. The movement of 2 is controlled by this,
It can now be applied to the work of inserting and assembling work 8,
The scope of application can be expanded.

(d) As explained in FIG. 9 above, in the conventional example, a very soft workpiece is deformed and cannot be gripped. Therefore, it is possible to control the gripping force to a low level using the strain gauge 14 of the leaf spring 12. and does not deform the workpiece.

According to the present invention, the gripping operation of opening and closing of the fingers 6.6 can be performed quickly, and versatile and stable gripping can be performed regardless of the shape, size, hardness, etc. of the workpiece, and the gripping force can be controlled and the gripping operation of the workpiece can be controlled quickly. The position of a point can be calculated.

〔Effect of the invention〕

According to the present invention, a pressure receiving plate for gripping a workpiece is attached to the inside of a pair of fingers of a robot hand via a leaf spring,
The total strain of this temporary spring is detected by a pair of strain gauges provided on each leaf spring, and the d strain of the finger is detected by a pair of strain gauges provided at the base of the finger. A robot hand having a gripping force detection function for gripping a controlled workpiece can be provided.

The pressure-receiving plate is supported by a leaf spring, which allows for a soft touch to the workpiece, and its gripping force is controlled.
(b) The gripping action is fast, (b) It is possible to grip stably along the shape of the workpiece, (c) The gripping point can be calculated, and (d) Very soft workpieces can be gripped without deformation. is obtained. For this purpose, the shape and size of the workpiece.

It is possible to provide a robot hand that can perform versatile and stable gripping regardless of hardness and has an expanded range of applications.

[Brief explanation of the drawing]

1 to 4 are diagrams showing embodiments of the present invention.
The figure is a side view showing the structure, FIG. 2 is an enlarged view showing the deformed state of the leaf spring 12 at the P section in FIG. 1, FIG. 3 is a circuit diagram of the electric circuit device of the strain gauges 4 and 14, The figure shows the principle of detecting the gripping point C of the workpiece 8. Figures 5 to 9 show conventional examples. Figure 5 is a side view showing the structure, and Figures 6 to 9 show the workpiece. Fig. 6 is a diagram showing the closing speed of the fingers 7.7, Fig. 7 is a side view showing the state in which a workpiece with a rectangular cross section is grasped, and Fig. 8 is a diagram showing the state in which the fingers 7.7 are grasped. FIG. 9 is a diagram showing a state in which C is unknown, and FIG. 9 is a diagram showing a state in which a very soft workpiece is being gripped.

Claims (1)

[Claims] 1) A robot hand that opens and closes a pair of fingers to grasp and release an object, and that grips the object inside the fingers in a robot hand that is equipped with a pair of strain gauges in a small thick part provided near the base of the fingers. A gripping force detection function characterized in that a pressure receiving plate is movably attached to a finger via a dogleg-shaped leaf spring bent at an acute angle at both ends thereof, and each leaf spring is provided with a pair of strain gauges. A robot hand with