JPS5953179A - Method and device for controlling grasping power in manipulator - 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 The present invention relates to a method and apparatus for controlling the gripping force of a so-called manipulator that has the function of gripping an object.

In recent years, so-called industrial robots have become widely used, and their functions have also been improved.

Among these devices, devices called manipulators are used to perform the functions of human hands in environments where humans cannot enter for safety and health reasons, and are in practical use in various forms.

One of the functions required of such a manipulator is to grasp objects.

This function of grasping an object involves, for example, maintaining a constant grip force applied to the manipulator to grasp the object if the object has a certain shape, a certain size, and a certain hardness. By keeping the displacement of the gripping action part of the manipulator constant, it is possible to determine in a simulated manner that the grip is being gripped when these values reach a certain value.

However, if the size and shape of the object vary to some extent, and if the object is easily deformed when gripped by a manipulator, such as a paper cup, the above-mentioned discrimination method cannot be used. Therefore, in order to meet this requirement, manipulators equipped with tactile functions have been proposed in the past, but in this case, discrimination is simply based on information about the hardness of the object and the grip force of the manipulator; Since it does not detect any deformation of the object caused by being touched, it has the disadvantage that it tends to cause unnecessary deformation, especially to soft objects, and there is also variation in detection operation depending on the placement position of the tactile sensor, and the complexity of the device itself. It is difficult to say that it is in accordance with the actual situation as it is easily subject to change.

The present invention has been made in consideration of the current situation, and aims to provide a manipulator that is not greatly influenced by the shape and size of an object and can reliably grip even soft objects. This is what was done about the device. In order to solve this problem, the present invention optically detects the deformation of an object caused by the object being gripped, and controls the gripping force of a manipulator based on the deformation detection signal. Furthermore, in order to ensure sufficient detection accuracy when performing optical detection, a grating image is projected onto the surface of the object, and optical detection is performed using this projected grating image.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing the principle of an embodiment of the present invention. In FIG. 1, 1 indicates a manipulator, and O indicates an object to be gripped by the manipulator 1.

The manipulator 1 includes two arms 11 that are pivoted at a fulcrum P and are swingable relative to each other, and an action piece 12 that is fixed to one end of these arms 11 and comes into contact with an object when gripping the object.
It further includes, for example, a hydraulic bag [13] that drives the arm 11.

Therefore, by controlling the drive of the hydraulic device 13, the two arms 11 can be swung around the fulcrum P to apply gripping force to the object O, and also to release the gripping force. 2
is a projection optical system, which includes a light source lamp 21 and a condenser lens 2.
2, a reference grating 23, and a projection lens 24. With this configuration, the grid pattern of the reference grid 23 is
The projected image will be formed on the outer surface of. 3 is a detection control unit which includes an image sensor 32 such as a CCD and an interface outside the imaging lens 31, and sends signals obtained by the image sensor 32 or appropriately input external signals to a microcomputer to be described later. In response to control signals from the input control section 33 and the input/1 control section 33,
a storage unit 34 that stores signals from the image sensor 32;
Performs arithmetic processing based on data from the storage unit 34 or the image sensor 32, and drives the hydraulic device 13 of the manipulator 1 by the output from the microcomputer 35, for example, to obtain a pattern discrimination output according to these processings. Control unit 3 for controlling
6. In FIG. 1, the optical axis A2 of the projection optical system 2 is at an angle with respect to the optical axis A of the control unit 3 in the direction of the paper, that is, in a plane parallel to the plane on which the manipulator 1 applies grip force to the object 0. Although this is fine in principle, if the direction in which the grip force is applied is one direction, the inclination of the optical axis A1+At is the direction in which the object is deformed when the manipulator grip force is applied. It is preferable to align it in a direction out of reach of the

Further, in such a case, in order to improve the detection accuracy, it is desirable that the direction of the line of the projected grating image of the reference grating is such that the inclination of both optical axes A1°A is perpendicular to the arrangement direction.

According to the above configuration, when the object 0 is gripped by the manipulator 1, the outer surface of the object is deformed depending on the grip force applied by the action piece 12, but the manner of this deformation is determined by the projection optical system 2. By monitoring the image of the reference grid projected onto the surface of the object, it can be captured as a pattern.

(7) For example, FIGS. 2(A) and 2(B) show a projected grid when the object to be gripped by the manipulator 1 is a roughly cylindrical paper cup, and the direction of the manipulator's grip force is perpendicular to the plane of the paper. The images are schematically shown before and after the deformation. FIG. 2 (4) is a projected grating pattern before the grip force of the manibulator is applied, and as shown, it has a substantially uniform pattern distribution. This pattern is the image forming lens 31
The image is formed on the image sensor 32 via the image sensor 32, and the image sensor 32 captures this as a brightness distribution, and this signal output is stored as pre-transformation data in the storage unit 34 in response to a command input from the input control unit.

Thereafter, the manipulator 1 is actuated by the hydraulic device 13, and grip force is applied to the object 0 by the operating piece 12, and at the same time, the object 0 begins to deform. At the same time, the pattern of the projected image projected onto the surface of the object 0 and observed by the optical system of the detection control unit 3 changes.

The state of the deformation is observed every moment by an image sensor (8) as an image, that is, a brightness distribution pattern, and the information is input to the microcomputer 35. At the same time, the data before transformation is read from the storage section 34 to the microcomputer 35 via the input control section, and compared with the pattern information that is being transformed in real time.

FIG. 2(B) shows an example of such a deformation pattern, in which the soft object 0 is deformed around the action piece 12 due to the force applied by the action piece 12 and directed from the front side to the back side of the page.

As a result, the pattern observed by the image sensor 32 has a partially non-uniform pattern distribution as shown in the figure. This pattern deformation is quantitatively compared with the pre-deformation pattern described above to detect the difference, and when a certain set value is reached, the microcomputer 35 sends a control signal to the control section 36 to drive the drive section of the manipulator 1, that is, the hydraulic device 13. A stop signal is given, so that the drive of the hydraulic device 13 is stopped. Note that the set value used as a reference when the microcomputer 35 (9) generates the stop signal is as follows:
It is set in advance by the input control unit according to the hardness, weight, etc. of object 0.

In such a detection method, the detection standard is data on how much the deformed grid pattern has displaced with respect to the undeformed grid pattern, but the detection accuracy is
Moiré fringes are used to enhance the image quality. That is, if signal processing is performed so that the lattice pattern that is being deformed is superimposed on the pre-deformation pattern at every moment, only the deformation information can be extracted as a pattern. For this purpose (d
It is sufficient to use only the data obtained as the intersection point when the pre-transformation data stored in the 1 storage unit 34 and the moment-by-moment data after the transformation are superimposed. FIG. 3 shows the moire knitting pattern obtained in this way, and in this pattern, the degree of deformation is simply determined by the number of the stitches. In the illustrated example,
The number of moiré manuscripts can be identified as four. This identification can be performed automatically by observing the monitor image or based on the number of intersections with the reference line indicated by X (10) or Y in FIG.

Figure 4 shows a Moiré draft when a paper cup is used as an object, and the grip force is in one direction, that is, instead of holding it from both sides, one action piece is fixed and pressing force is applied from one side of the other action piece. This is a correlation between the number of lines and the modification I, and the correspondence relationship is clear.

FIG. 5 schematically shows how moire fringes are generated when grip force is applied to the paper cylinder 40 from the action pieces 41 and 42 on both sides, and three moire fringes are generated. Further, FIG. 6 is a correlation diagram between the amount of deformation and the number of moiré fringes generated in this case.

In this way, it is possible to monitor the amount of deformation of an object based on the number of moiré fringes that occur, but the number of moiré fringes that must be generated before a signal to stop the operation of the manipulator is generated can be selected in various ways depending on the situation. Furthermore, the detection accuracy can be easily improved by making the pitch of the reference grating used finer (11).

As described above, according to the present invention, when an object that is easily deformed is gripped by a manipulator, the object deformation is identified as a pattern, the object is prevented from being excessively deformed, and the object is It is possible to detect the corresponding grip force, and by using this to control the manipulator, safe and reliable operation of the manipulator can be guaranteed.

Moreover, another advantage of the present invention is that the detection does not involve contact with the object and is not easily affected by the shape or type of the target object.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle configuration of an embodiment of the present invention. FIGS. 2(4) and 2(B) are schematic diagrams showing projected lattice patterns before and after deformation, respectively. FIG. 3 is a schematic diagram showing an example of moiré fringes obtained by object deformation. FIG. 4 is a graph showing the correlation between the number of moire drafts shown in FIG. 3 and the amount of object deformation. (12) FIG. 5 is a schematic diagram showing the occurrence of moiré fringes in another embodiment of the present invention. FIG. 6 is a graph showing the correlation between the number of moiré manuscripts and the amount of object deformation in the example of FIG. 1... Manipulator 12... Action piece 13...
Hydraulic device 2... Projection optical system 23... Reference grating 3... Detection control unit 32... Image sensor
33...Input control unit 34...Storage unit 35...Microcomputer 36...Control unit O...Object applicant Fuji Photo Co., Ltd. (13) Engraving of drawing (no change in content) (, A) (ffi) Procedural amendment (method) 1. Indication of the case 1982 Patent Application No. 164410 2. Name of the invention Grip force control method and device in a manipulator 3. Person making the correction February 2, 1988 (shipped) (Japanese) February 22, 1982

Claims (4)

[Claims] (1) When grasping an object with a manipulator,
In a method for controlling grip force applied to an object, a reference grid projection image is projected onto the object surface, changes in the reference grid projection image are monitored before and after grip force is applied to the object, and changes are made according to the amount of change. A grip force control method for a manipulator that obtains a photoelectric detection signal and controls the grip force applied to an object based on this detection signal. (2) Moiré fringes are obtained by superimposing the projected images of the reference gratings before and after gripping force is applied to an object, and the gripping force applied to the object is controlled by a photoelectric detection signal according to this moiré fringe information. The method described in scope item (1). (3) A gripping force supply unit that supplies gripping force to a gripping unit that grips an object, a grating projection unit that forms a reference grid projection image on the object surface, and an imaging unit that identifies the grid projection image as a pattern image. and a control unit that controls the operation of the grip force supply unit based on a signal from the imaging unit. (4) A storage unit is provided to store the signal from the imaging unit as a pattern image, the grid projection image pattern before grip force is applied is stored in this storage unit, and this memory information and the object are imaged after grip force is applied. A control input signal of the control unit is defined by a signal from an analysis unit that synthesizes the pattern image information of the lattice projection image obtained from the unit to obtain moire fringes, and analyzes the moire fringes. ) A grip force control device for the manipulator described in item 1.