JP2560832B2 - How to determine the hardness of an object - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for determining the hardness of an object, and more specifically,
With the distributed pressure sensor attached to the robot hand,
The present invention preferably relates to a method for determining the hardness of a target object.

[Prior Art] In recent years, as robots have become more intelligent, it is required to be adaptable to many functions and multiple environments, and articulated robots and robots equipped with various sensors are being developed. In the past, one robot was in charge of only one process for one component or tool in the manufacturing process or the assembly process, and the manufacturing process or the assembly process was established by a plurality of robots. In recent years, it has become necessary for a single robot to perform a plurality of processes using a plurality of parts and tools.

Therefore, in such a robot, it is an important point to be able to detect information (for example, hardness and shape of an object) regarding many characteristics with respect to an object held by a hand, which is an end effector, and an external environment with which the hand is in contact.

Hereinafter, a method that has been conventionally implemented for detecting information regarding hardness particularly with respect to the gripping target and the external environment will be described.

FIG. 5 shows a configuration of an apparatus applied to hardness discrimination as a first conventional example. Here, the fingers 12 forming a pair are driven by the finger driving mechanism 13 in directions opposite to each other, and the target object 14 can be gripped therebetween. Fifteen
Is a load detector attached to each finger 12, 16 is a hand that movably supports each finger 12, 17 is a displacement measuring device that measures the amount of displacement of the fingers 12, and in this example,
The hardness of the grasped object 14 is determined using the ratio of the load of the finger 12 to the displacement of the finger 12 when the object 14 is grasped between the two fingers 12 as a parameter (see FIG. 6). In FIG. 6, 29 indicates the load-displacement characteristic of a hard object, and 30 indicates the same characteristic of a soft object.

FIG. 7 shows the structure of a device according to a second conventional example, in which 18 is a support having a pressure receiving portion 19 for receiving the load of an object and a load detector 20 for detecting the load transmitted to the pressure receiving portion 19. A member, 21 is a bellows interposed between the support member 18 and the fixed plate 22, 23 is a hole provided in the fixed plate 22, and is an air supply port for supplying air into the bellows 21. Is provided with an air pressure measuring device (not shown). Therefore, in this example, when the target object comes into contact with the pressure receiving portion 19 and the load is transmitted, the hardness of the target object is determined using the ratio of the detected load to the air pressure after the contact as a parameter (first (See Figure 8). In FIG. 8, 31 indicates the load-pressure characteristic of a hard object, and 32 indicates the same characteristic of a soft object.

Further, FIG. 9 shows the configuration of the apparatus according to the third conventional example. The supporting member 18 of this example includes a light emitting element 25 in addition to the pressure receiving portion 19 and the load detector 20, and the holding table 26 for driving the supporting member 18 via the supporting member leg portion 18A. A voice coil magnet 27 is provided. Reference numeral 28 denotes a light receiving element provided on the holding table 26 so as to face the light emitting element 25, and the displacement of the support member 18 is caused by displacement of light between the light emitting element 25 and the light receiving element 28 via a displacement measuring means (not shown). Is detected. Therefore, when the object contacts the pressure receiving portion 19, the subsequent displacement is detected, and the hardness of the target object is determined from the characteristics shown in FIG. 6 with the ratio of the detected load to the displacement as a parameter.

[Problems to be Solved by the Invention]

However, according to the first conventional example, it is necessary to calibrate the sensors of both the load detector and the displacement detector and collate the sensor outputs, which not only requires the procedure and labor, but also occurs in the drive mechanism. Accurate detection of hardness is difficult due to play and friction that affect the detection accuracy of the detector.

In addition, the second conventional example requires a load detector and an air pressure measuring device, which complicates the device and requires a downsizing to mount such a mechanism on a robot hand. In order to ensure the contact point between the hand and the object, it will be equipped with a plurality of the above-mentioned mechanism,
A device with a more complicated structure is required.

Furthermore, the third conventional example requires a displacement measuring device including a light emitting element and a light receiving element together with a load detector, and has the same problem as in the second conventional example.

An object of the present invention is to focus on the above-mentioned conventional problems, and in order to solve the problems, the hardness of an object can be easily determined by using a distributed pressure sensor having a single structure without relying on displacement measuring means. The purpose is to propose a method for determining the hardness of an object.

[Means for solving the problem]

In order to achieve such an object, the object hardness determination method of the present invention is configured such that a distributed pressure sensor in which a plurality of load detection elements are arranged is attached to a robot hand, and the robot hand grips the object or the robot hand. The hand is brought into pressure contact with the object to individually detect the load from the plurality of load detection elements, the load deviation value of each of the load values is calculated based on the plurality of detected load values, and the load deviation value The hardness of the object is determined based on the distribution characteristics.

[Work]

When the target object comes into contact with the distributed pressure sensor attached to the robot hand, the object deforms according to its hardness, but the harder it is, the less deformation occurs. The load applied to each of the load detecting elements that is in contact with and keeps in contact with the load detecting element is small compared to the case where the load is soft. Therefore, the harder it is, the larger the deviation of the output from each load detection element becomes. On the other hand, when the object is soft, many load detecting elements keep contact with the object, and the contact force is dispersed. Therefore, the load applied to these many detecting elements is smaller than that when it is hard. Therefore, the deviation of the output from each detection element becomes small.
Therefore, according to the present invention, the hardness of the object can be determined with reference to the above-mentioned deviation.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail and specifically with reference to the drawings.

FIG. 1 shows an outline of an apparatus for carrying out the present invention,
Reference numeral 1 denotes a distributed pressure sensor attached to the hand 3 of the robot 2. As the distributed pressure sensor 1, for example, although not shown here, a single crystal silicon plate provided with a plurality of semiconductor strain gauges and a load applied to the single crystal silicon plate protruding from the single crystal silicon plate A load detecting element having a pressure receiving portion for receiving the pressure is arranged in a matrix and a load applied to the single crystal silicon plate through the pressure receiving portion can be detected from a change in the electrical resistance of the semiconductor strain gauge. The one disclosed in JP-A-63-155674 can be used.

Reference numeral 4 denotes an interface for processing a load detection signal from the distributed pressure sensor 1, and reference numeral 5 denotes a computer for performing a calculation process, which will be described later, on the load detection signal input along with the operation of the robot hand 2.

Now, FIG. 2 and FIG. 3 show a state in which an object of interest is gripped by such a robot hand 3. FIG. 2 shows a state in which a hard object 6 is gripped between the hands 3. In the case of the hard object 6, the object 6 is not much deformed as shown in this figure, and therefore a small number of load detecting elements 1A are used for the object 6. By maintaining contact with the surface of the sensor, a sensor output having a size as shown by an arrow 7 is obtained from these load detecting elements 1A.
On the other hand, FIG. 3 shows a state in which a soft object 8 is gripped between the hands 3, and in such a case, the object 8 is easily deformed, and therefore more load is detected than in FIG. Since the element 1A keeps in contact with the surface of the object 8, the load detecting elements 1A obtain widely dispersed sensor outputs as shown by the arrow 9, and each sensor output is relatively small.

Therefore, in the present invention, the load deviation σ _n-1 is calculated in the computer 5 from the sensor outputs obtained as described above based on these sensor outputs. ).

Where F: total sensor output, f _m : average sensor output, i, j: sensor distribution position designation, f (i, j): each sensor output, σ _n-1 : load deviation value An example of the result of the experiment performed according to the procedure is shown. In addition, in this experiment, a shear type A hardness tester [ASTM D
2204], HS values of 18, 29, 35, and 45 having four types of hardness were used as target gripping objects, and the respective load deviation values were obtained. That is, FIG. 4A shows an object with an HS value of 18,
(B) is an object with an HS value of 29, (C) is an object with an HS value of 35,
(D) is the total load F when an object with an HS value of 45 is targeted.
The load deviation value σ _n-1 is shown.

As is clear from these experimental results, the load deviation values of the sample objects having four types of hardness are distributed within the range indicated by the broken line, and the respective distribution areas are almost collectively dispersed. I understand. Therefore, from the recognition of such characteristics, the hardness of the object can be determined by referring to the load deviation value as a parameter.

〔The invention's effect〕

As described above, according to the present invention, an object is gripped by the robot hand, or the robot hand is pressed against the object, and the load at that time is detected by the plurality of load detection elements of the distributed pressure sensor provided in the hand. Individually detected,
The load deviation is calculated individually based on the detected load values, and the hardness of the object is determined based on the distribution characteristics of these load deviation values. It is possible to determine the hardness of an object without doing this, and since it is possible to calculate the load deviation value for determining the hardness according to a simple calculation formula, it is necessary to make the determination after the hand touches the object. The time is short.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing an outline of an apparatus for carrying out the present invention, and FIGS. 2 and 3 show sensor outputs when gripping a hard object and a soft object in the course of carrying out the present invention. FIG. 4 is a graph showing the distribution characteristics of load deviation values as experimental results when a hardness discrimination experiment is performed by the method of the present invention, FIG. 5, FIG.
FIG. 9 and FIG. 9 are configuration diagrams showing examples of various conventional devices for determining hardness, and FIG. 6 is a reference when hardness is determined by the devices of FIG. 5 and FIG. FIG. 8 is a graph showing a load-displacement relationship, and FIG. 8 is a graph showing a reference load-pressure relationship when hardness is discriminated by the apparatus of FIG. 1 …… Distributed pressure sensor, 1A …… Load detection element, 2 ……
Robot, 3 ... Hand, 4 ... Interface, 5
…… Computer, 6,8 …… Object, 7,9 …… Sensor output.

Claims (1)

(57) [Claims] 1. A distributed pressure sensor in which a plurality of load detecting elements are arranged is mounted on a robot hand, and an object is gripped by the robot hand, or the robot hand is pressed against the object to detect the plurality of load detecting elements. To individually detect the load, calculate the load deviation value of each of the load values based on the detected plurality of load values, and determine the hardness of the object based on the distribution characteristic of the load deviation value. A method for determining the hardness of an object characterized by