JP4963263B2 - Tactile sensor element - Google Patents

Description

  The present invention relates to a sensor capable of quantitatively measuring tactile information instead of a human tactile sense. More specifically, the present invention relates to three different contact angles between a spherical surface, an aspherical surface, or a non-planar curved surface and an object. This is a new type of tactile sensor that provides high-precision tactile sensing capability that can be used to estimate the strain distribution or stress distribution generated on the curved surface by contact while adjusting using the strain or stress value of -It is related with the detection mechanism using the method of detecting the hardness softness which is a deformation resistance of an object in real time. The present invention includes, for example, human cooperative robots, prosthetic hands / prosthetic fingers / limbs, palpators for examination, hardness / softness testers for various industries, and further, minimally invasive surgery in the medical field and cell manipulation in the bio field. The present invention provides a novel tactile sensor that has a function of perceiving a material at the moment of contact with an object, which is disposed in a portion that contacts an object such as a manipulator, and has a simple structure.

  A human fingertip has a plurality of functions such as temperature detection, grasping ability and tactile ability. In particular, the touch sensation has an excellent ability. The ability to discern steps of several microns on the surface of an object that cannot be detected visually is a good example of understanding the high resolution of human fingertips. In addition, when a person recognizes what an object is made of, in addition to visual information, information obtained by directly touching with a hand, that is, weight, hardness softness, surface smoothness ( Feeling such as surface roughness plays an important role.

  In various manufacturing industries, the quality of processed products, molded products, manufactured products, etc. is judged by the high-precision touch sensing ability that humans essentially have. In order to replace such product inspection work with automated non-destructive inspection such as robots for efficiency, mechanical touch sensors are required in a wide range of industries such as the food industry and the manufacturing industry.

  On the other hand, various functional sensors have been developed to provide tactile functions to machines such as robots and artificial hands. The main thing that has been put to practical use so far is the function to feel what is being grasped as a pressure and the grip function to which this is further applied. The grip function is a function of gripping an object without breaking or crushing it or dropping it. This is the most important function in industrial robots that are intended to move and carry heavy objects made of known materials such as machine parts on behalf of humans.

  However, the grip function for gripping objects on the parts that come into contact with objects such as manipulators used for minimally invasive surgery in the medical field and cell operations in the bio field, and the fingertips of humanoid robots for nursing and crime prevention. In addition, it is necessary to have a sensing function capable of measuring tactile information in real time in the same manner as a human fingertip and capable of qualitative analysis of the material of an object. If the material can be identified instantly by contact with an object, not only can the grip function be complemented, but it will also have the effect of acquiring and forming intelligence close to that of a person.

  In order to detect and recognize the characteristics of an object, the following sensors have been developed as sensors using contact means. That is, as a simpler method, there is a method using an output signal of a strain gauge attached to a side surface of a robot finger. The principle is based on the relationship between the deflection of the beam and the force, and the information obtained only from the contact load is not a tactile sensor that is sufficiently effective for the formation and acquisition of intelligence.

  There is a method of detecting the hardness of the contact substance by utilizing the fact that the oscillation frequency of the vibrator changes according to the material of the object when the sensor incorporating the objective contact vibrator is brought into contact with the object ( Patent Documents 1 to 5). These are methods for detecting the hardness of a contact substance by contact. However, the principle is completely different from the principle of the present invention.

  As a method of combining contact and optical detection method, the deformation of the tactile sensor with flexibility in the push-in direction is recognized by the camera installed inside and the shape of the contact object is recognized (Patent Document 6), elastic deformation There is one that detects a shape using a whisker (Patent Document 7). However, these methods are tactile sensors that detect a three-dimensional feature of a contact object, and do not detect information on the hardness and softness of an object.

  Furthermore, as an acoustic detection method, the deformation of the cavity when the acoustic resonance tactile sensor sensor and the object by the ultrasonic element are contacted with the object is detected as a change in the resonance frequency, and the contact force is determined. There is a detection method (Patent Document 8, Non-Patent Document 1). According to this, although the friction coefficient of the target object regarding slip required for a grip function can be calculated | required, the information of the hardness softness of a target object is not obtained.

  Desirably, fingertips such as medical and nursing robots and humanoid robots also have a function (sensing function) that collects tactile information through contact with an object in the same manner as the skin of a human fingertip. It is. In addition, a small and simple structure is required for minimally invasive surgery in the medical field and cell manipulation in the bio field.

  A life support robot must be surrounded by objects made of various materials. Under such an activity environment, it is considered that the efficiency of the gripping operation is improved by having an analysis function for recognizing the material of the powder at the moment of contact and specifying the substance. Furthermore, the ability of the tactile sensor to recognize the material leads to the acquisition of the intelligence of the robot, and the importance of the sensor having the analysis function is expected to increase in the future.

  The characteristic parameters used by humans to characterize objects vary widely, such as mechanical properties such as elastic modulus and hardness, thermal conductivity such as thermal sensation, and surface properties in addition to specific gravity and density. Has been developing a tactile sensor for fingertips focusing on the mechanical characteristics (Non-Patent Document 2).

  Indenter mechanics is a new technology that enables simultaneous quantitative evaluation of non-time-dependent elastic, elasto-plastic, and time-dependent viscoelastic properties of various industrial materials by pushing a contact probe (indenter) into the solid surface. It is dynamics, and academic systematization is being promoted from both science and engineering (Non-Patent Documents 3 and 4). The spherical indenter used in this indenter mechanics has a shape and function similar to those of the “finger abdomen”, so by applying indenter mechanics techniques and analysis methods to tactile sensors, sensors with new functions can be developed. It is expected.

  Based on the above technical background, the applicant has a function (sensing function) that collects tactile information through contact with an object in the same manner as the skin of a human fingertip, and perceives the material at the moment of contact with the object. A new tactile sensor that can be used has been created (Patent Document 9).

  A tactile sensor that approximates the strain distribution or stress distribution generated on a curved surface by contact with an object with at least two detection elements has a sensing function that measures tactile information in real time in the same manner as a human fingertip. This enables qualitative analysis of the material of the object at the moment of contact. Since the above-mentioned tactile sensor is made in a curved surface shape imitating the shape of a human finger belly, it can be used as it is as a fingertip belly of a humanoid robot such as a humanoid. In a simple gripping operation, the tactile sensor incorporated in the finger pad always comes into contact with the object. However, there are still matters to be improved. That is, in practice, the center of the curved surface corresponding to the belly of the finger is not always the contact center. In order to be able to correctly analyze the detection signal of the tactile sensor, it is necessary to arrange the detection element of the tactile sensor at an optimal position. However, the conventional tactile sensor does not give such consideration.

No. 40-27236 Japanese Patent Laid-Open No. 1-189083 JP-A-5-322731 JP-A-6-58829 Japanese Patent Laid-Open No. 10-300594 JP 2000-288773 A JP 2002-116101 A JP 2001-21482 A JP 2007-17243 A Hiroyuki Shinoda, Journal of the Robotics Society of Japan Vol. 18, no. 6, pp. 767-771 (2000) Tatsuya Miyajima, Koji Sakai, Application of Indenter Mechanics to Tactile Sensors, Lectures on Robotics and Mechatronics '06 Proceedings, 2P2-B04, 2006 J. et al. Mater. Res. , vol. 14, pp. 3630-3639, 1999 J. et al. Non-Cryst. Solids, Vol.282, pp. 236-247, 2001

  Under such circumstances, the present inventor has conducted intensive research with the goal of developing a new tactile sensor capable of correctly analyzing the detection signal of the tactile sensor in view of the above-described conventional technology. As a result, the inventors succeeded in developing a tactile sensor element having a function of perceiving a material while adjusting the relative positional relationship between the detection element of the tactile sensor and the contact point, and completed the present invention. The present invention provides a new type of tactile sensor having a function of perceiving a material while adjusting the relative positional relationship between a detection element and a contact point at the moment of contact with an object, and having a simple structure. It is the purpose.

The present invention for solving the above-described problems comprises the following technical means.
(1) A tactile sensor that has a spherical shell structure in which the inner and outer surfaces are spherical surfaces, and measures deformation at three different points depending on strain gauges attached to the inner surface when the outer surface of the spherical shell comes into contact with an object. , Having at least three detection elements for detecting strain distribution or stress distribution generated on the curved surface by contact with the object, and using the spherical deformation signal that is a measurement signal of these detection elements, A tactile sensor characterized by having an axial center adjustment function for adjusting so that the center of contact is the contact center.
(2) The tactile sensor according to (1), wherein the tactile sensor according to (1) has an axial center adjustment function that detects a strain distribution or a stress distribution generated on a curved surface by contact with an object and adjusts a relative position between a contact center and a detection element. .
(3) The output signal ε ₁ of the detection element ₁ and the output signals ε ₂ and ε _{3 of} the detection element 2 and the detection element 3 satisfy the condition of ε ₃ / ε ₂ = 1, and ε ₂ / ε ₁ is minimal The tactile sensor according to (2), wherein the relative position between the contact center and the detection element is adjusted so as to be a value.
(4) The method according to (1), further including a detection element that detects a strain distribution generated on a spherical surface, an aspherical surface, or a non-planar curved surface by contact with an object, or a stress distribution from two different strains or stress values. The tactile sensor (5) detects the deformation resistance of the contacted substance from the rate of change of the difference between two different strains measured using electrical, optical, magnetic or acoustic means, and The tactile sensor according to (1), wherein characteristics relating to hardness and softness are determined.
(6) The tactile sensor according to (1), wherein a sensor made of a known substance is used and a function of recognizing the material of the contact material is provided by quantitatively measuring the deformation of the sensor.
(7) The tactile sensor according to (1), wherein a strain gauge is arranged inside a spherical shell structure having a curved elastic body.
(8) The tactile sensor according to (1), including signal processing means in which at least three strain gauges are arranged on the elastic body curved surface, and signal processing means for processing the signal and calculating a strain difference change rate.
(9) The tactile sensor according to (8), wherein the signal processing unit includes a distortion conversion amplifier, an analysis value storage unit, and an analysis value calculation unit.
(10) A strain gauge that detects strain at the center and non-center positions, a means for calculating the hardness of the object from the rate of change of the strain difference, and the material of the contact material is recognized by comparison with experimentally obtained numerical values The tactile sensor according to (1), including means for performing
(11) The above-described function (9) has a function of perceiving deformation resistance such as hardness and softness of an unknown substance by comparing the data calculated by the analysis value calculation means with existing data and converting it into perceptual data. ) Tactile sensor.

Next, the present invention will be described in more detail.
The present invention is a tactile sensor that has a spherical shell structure whose inner and outer surfaces are spherical surfaces, and measures deformation at three different points depending on strain gauges attached to the inner surface when the outer surface of the spherical shell comes into contact with an object. And having at least three detection elements for detecting the strain distribution or stress distribution generated on the curved surface by contact with the object, and using the spherical deformation signal which is a measurement signal of these detection elements. It has an axial center adjusting function for adjusting the center so as to be the center of contact. In the present invention, a strain distribution or a stress distribution generated on a curved surface by contact with an object is detected, and an axial center adjustment function for adjusting a relative position between the contact center and the detection element is provided, and an output signal of the detection element 1 Detection of the contact center so that ε ₁ and the output signals ε ₂ and ε _{3 of} the detection element 2 and the detection element 3 satisfy the condition of ε ₃ / ε ₂ = 1, and ε ₂ / ε ₁ is a minimum value. Adjusting the relative position to the element is a preferred embodiment.

  Next, in order to explain the principle and operation of the present invention, consider contact between two surfaces. One is a surface of an unknown substance and is a plane. The other is a sensor surface having a curved contact surface, and a function for measuring the amount of deformation of the surface is incorporated in the sensor surface. As the surface of the sensor and the surface of the unknown substance are brought into contact with each other and the distance between the two is further reduced, the contact load and the diameter of the contact surface increase, and at the same time, each other surface is deformed, and the curvature is different from the original surface. It becomes. The material of the unknown substance is specified based on the principle that the manner in which the curved surface shape is deformed and the size of the contact surface are determined by the contact load and the mutual material (elasto-plastic characteristics). That is, the material of the contact material is perceived by using a sensor made of a known material and quantitatively measuring the deformation of the sensor.

  To assist in understanding the tactile sensor of the present invention, two types of objects having different hardnesses are considered. FIG. 1 is a schematic diagram illustrating a state in which the curved surface of the tactile sensor is in contact with the surface of a target object that is a plane. FIG. 1A illustrates a case where the target object is relatively “soft”, and The relatively “hard” case is shown in FIG.

Here, assuming that the same load P is applied in both examples, the soft substance shown in FIG. 1A, that is, the easily deformable substance is deeply pushed in, so that a relatively wide contact surface is formed. , A contact circle having a radius a ₁ and a contact area Ac ₁ (= πa ₁ ² ). On the other hand, a relatively hard material that is not easily deformed, as shown in FIG. 1B, the push-in depth of the tactile sensor with respect to the object surface is shallow, and therefore the contact surface is narrow, that is, the radius of the contact surface. a ₂ and the contact area Ac ₂ (= πa ₂ ² ) are smaller than in the soft case (a ₂ <a ₁ , Ac ₂ <Ac ₁ ).

For contacts where contact deformation is performed within the elastic range, classical Hertz theory has been established, and it is widely and generally possible to accurately describe the deformation behavior using the above parameters and elastic modulus (Young's modulus). Are known. The radius of the contact surface has a relationship of a = (hR) ^1/2 using the indentation depth h and the curvature radius R of the curved surface. Further, considering the contact stress in the contact axis direction between the curved surface and the object, the maximum is taken at the center of contact, and in the example of FIG. 1A, the maximum value p ₀ is (3/2) (P / πa ₁ ² ).

On the other hand, in the case of FIG. 1B, which is a hard material that is relatively difficult to deform, the maximum value p ₀ of the contact stress is (3/2) (P / πa ₂ ² ), and the relationship of a ₂ <a ₁ Therefore, the maximum contact stress takes a higher value. That is, when contacting with the same load P, when the object is hard and difficult to deform, a higher stress is generated at the center of the contact circle than when the object is soft and easily deformed. In the description so far, only the vertical stress has been described, but the same applies to a vertical strain or a radial stress or a radial strain with the contact center as the origin.

In this state, when considering the normal stress distribution distributed in the contact portion of the sensor curved surface loaded with the same load, the soft substance has a low maximum value S ₁ of the contact stress S and a wide contact area (Ac = πa ₁ ² ). For this reason, the stress distribution becomes gentle. On the other hand, since the maximum value S ₂ of the contact stress S is high and the contact area (Ac = πa ₂ ² ) is narrow, a hard substance has a sharp gradient distribution. The contact stress distribution p in the contact circle can be written as p ₀ (1- (r / a) ² ) ^−1/2 , where r is the radial distance of the contact circle, according to the Hertz theory described above. These stress distributions are schematically shown in FIGS. 1 (a) and 1 (b), respectively. These mean that the stress distribution or strain distribution generated in the contact object is uniquely determined according to the hardness (resistance characteristic against deformation) of the object when contact is made under a predetermined condition.

  The present invention is based on the principle that when contact is made under a predetermined condition, the stress distribution or strain distribution generated in the contact object is uniquely determined according to the hardness of the object (resistance characteristic against deformation). The stress distribution or strain distribution is quantitatively measured to estimate the hardness of the object.

  Further, when the tip is not a curved surface, it is the same as the above-described curved surface. As an example, if the tactile sensor has a conical shape, the size of the contact surface between the tactile sensor and the object, that is, the contact radius a is small when the object is hard and large when the object is soft. . The normal stress distribution is expressed by the following formula 1 where α is the tip angle of the cone,

This means that the stress distribution or strain distribution generated in the contact object is uniquely determined according to the hardness of the object (resistance characteristics against deformation). Yes.

  However, the situation is different when the tip shape of the tactile sensor is not a curved surface but a plane, that is, a cylinder or a prism. In this case, the difference whether the object is relatively soft or hard appears in the difference that the indentation depth is deep or shallow, but the contact area is the same in any case. Therefore, no difference is seen in the maximum contact stress and the contact distribution in spite of the difference that the object is “soft” and “hard”. Thus, the shape of the contact surface is flat, that is, the shape of a cylinder or a prism does not show a function as a tactile sensor.

  FIG. 2 is a schematic diagram showing an example in which a plurality of stress detection elements or strain detection elements are arranged in a matrix at appropriate intervals on the tactile sensor. Thus, it is expected that the approximate accuracy of the estimated stress distribution or strain distribution is increased by using a plurality of signals obtained from each detection element. Further, it is preferable that the sensor and the object are pushed vertically. However, as shown in FIG. 3, even if the sensor and the object are displaced, a plurality of stress or strain elements are made symmetrical with respect to the sensor center. When arranged in a matrix, the sensor has a function of adjusting the contact angle of the sensor so that the maximum stress position is at the center of the sensor.

  First, a method for adjusting the contact point and the center detection element so as to be positioned on the coaxial straight line in the contact direction by the axial center adjustment using at least three detection elements, which is a feature of the present invention, will be described. FIG. 4 shows a state in which the misalignment state in which the contact point is not located directly above the detection element 1 arranged in the center is the relationship between the three detection elements of the tactile sensor and the contact center (Xc, Yc) is not adjusted. It is a schematic diagram which shows. It is a proposition to adjust the contact center portion (Xc, Yc) to be positioned immediately above the detection element 1 arranged in the center in a short time.

When the contact point is located immediately above the detection element 1 arranged at the center, that is, when the optimum state is reached, ε ₁ takes the maximum value. Therefore, the minimum value of ε ₂ / ε ₁ is a necessary and sufficient condition that the contact point is located directly above the detection element 1 arranged at the center.

Therefore, in principle, if the work of adjusting the axial center is performed so that “ε ₂ / ε ₁ becomes a minimum value”, the contact point is finally directly above the detection element 1 arranged in the center. It is possible to be located. However, with this policy, the time required for optimization is expected to be extremely long.

Therefore, as shown in FIG. 4, a method using a third detection element was established. However, the present invention is not limited to the method using three detection elements. If the sensor has at least three detection elements, that is, three or more detection elements, the tactile sensor of the present invention is similarly used. However, in order to make the explanation easy to understand, a case where three detection elements are used will be described as a typical example of the present invention. The output signal of the detection element 1 arranged at the center of the tactile sensor is called ε _1, and similarly, the output signals of the detection element 2 and the detection element 3 are called ε ₂ and ε ₃ . The detection element 2 and the detection element 3 are placed at the same distance from the detection element 1. That the signals from the detection element 2 and the detection element 3 are equal and ε ₂ = ε ₃ , in other words, that the condition that ε ₃ / ε ₂ = 1 is satisfied, indicates that the detection element 1 with the contact point arranged at the center It is a sufficient condition that it is located directly above.

The algorithm for quickly placing the optimal position is as follows. Axis center adjustment work so that the signals from the detection element 2 and the detection element 3 are equal, satisfy the condition of ε ₃ / ε ₂ = 1, and further satisfy ε ₂ / ε ₁ being a minimum value under this condition Is advanced. In FIG. 4, the condition where the output signals from the detection element 2 and the detection element 3 are equal, that is, the condition that ε ₃ / ε ₂ = 1 is drawn as a 45-degree straight line (dotted line, Y = X) passing through the origin. It is. In order to make the detection element 1 and the contact center coincide with each other, as a first step, the contact center portion (Xc, Yc) is placed on this straight line to satisfy the condition of ε ₃ / ε ₂ = 1, Proceed with the second stage of exploration along a straight line. In the second stage, the ratio ε ₂ / ε ₁ of the output signals from the detection element 1 and the detection element 2 is used as a criterion for condition determination. Here, when the coordinates (Xc, Yc) of the contact center are ((1/2) X1, (1/2) Y1), the distance from the contact center to the detection element 1 and the contact center to the detection element 2 Are equal, and the ratio ε ₂ / ε ₁ of the respective output signals is 1. Further, when the contact center coordinates (Xc, Yc) are farther than the point ((1/2) X1, (1/2) Y1), ε ₂ / ε ₁ > 1, and conversely, the contact center is If it is on the detection element 1 side (origin side) from this point, ε ₂ / ε ₁ <1. When the center of contact coincides with the detection element 1 and is positioned directly above, ε ₁ takes a maximum value, and ε ₂ / ε ₁ becomes a minimum value. Therefore, the optimum condition for adjusting the shaft center is reached when it is determined to be true by determining whether or not ε ₂ / ε ₁ takes a minimum value. If the above algorithm is followed, the labor or time spent for optimization can be saved significantly.

  Next, another method of the present invention will be described in which a stress distribution or strain distribution is approximately estimated by processing signals of only stress or strain at two different measurement positions.

  If a sensor with tactile intelligence can be configured with only data obtained from only two signal sources, not only the sensor components and wiring materials can be reduced, but also the labor and time required for signal processing can be reduced. The effect that leads to is born. These are consistent with the problem that a tactile sensor needs to be configured in the micro space at the tip of a robot or prosthetic fingertip or manipulator, and that signal processing results must be presented in real time. Yes.

  FIG. 5 is a schematic diagram of a scene in which a tactile sensor is brought into contact with two types of objects having different hardness, in the same manner as described above, in order to explain the operation of the present invention. Here, in two types of objects, a load condition is illustrated in which the maximum value of the vertical stress generated at the contact center is the same.

Although the load is not related to the essence of the present invention, a description will be added in order to emphasize the difference from the previous figure. The maximum contact stress generated at the contact center is (3/2) (P ₂ / πa ₂ ² ) for a hard object that is difficult to deform (left side), and (3/2) (P for the other soft object (right side). ₁ / πa ₁ ² ), there is a relationship P ₁ = (a ₁ / a ₂ ) ² P ₂ in the load under the condition where these stress values are equal. As described above, since there is a relationship of a ₁ > a _{2 under} the same load condition, (a ₁ / a ₂ ) ² > 1, that is, the load P ₁ of the soft object (right side) that is easily deformed is It must be higher than the load P ₂ of the hard object (left side).

  A soft object is drawn on the right side of FIG. 6 and a hard object is drawn on the left side. The stress or strain at the position (0) of the contact center and the stress or strain distribution at the position (1) that is the same distance away from the center. The stress or strain distribution is separated from the contact center by a certain distance. Approximation is performed at two positions. The following parameters are defined as indices indicating the resistance of deformation to contact.

Here, σ ₁ and ε ₁ are stress and strain at the contact center, and σ ₂ and ε ₂ are stress and strain at a position away from the contact center by a certain distance.

And hardness index H _Q calculated by the method of the present invention to known materials, hardness was measured by standard hardness testing method for the same material or elastic modulus, the deformation resistance, such as rigidity mechanical properties representing the deformation resistance is widely used from the hardness index H _Q unknowns by the mechanical physical properties if creating a calibration equation, such as the correspondence table or equation, by interpolation or exterior method representing the Conversion to a value is possible.

The following effects are exhibited by the present invention.
(1) To always optimize the relationship between the contact position of the tactile sensor and the detection element, that is, to adjust the position so that the contact point and the center detection element are positioned on the same axis in the driving direction for contact. It is possible to improve the accuracy and reliability of the numerical values calculated.
(2) The configuration of the tactile sensor is only at least three elements that detect the contact curved surface with the object and the deformation rate of the curved surface, and the tactile signal from the detection element is also used as a signal for adjusting the axis. Therefore, there is no need to newly install another mechanism for adjusting the center of the axis, so that the configuration is very simple. Therefore, it is easy to manufacture, is inexpensive, and can be downsized. .
(3) With the same sensor, it is possible to quantify the hardness and softness of a wide range of objects ranging from ultra-hard materials such as ceramics to extremely soft materials.
(4) Furthermore, the characteristics of a viscoelastic body exhibiting time-dependent deformation behavior can be quantified and displayed.
(5) The tactile sensor of the present invention uses the deformation of the tactile sensor itself when the tactile sensor having a curved surface similar to the shape of the palm of a person contacts the target substance. Therefore, it is possible to reproduce the sensory characteristics similar to those of humans.

  Next, examples of the present invention and measurement examples thereof will be specifically described. However, the following examples show preferred examples of the present invention, and the present invention is not limited to the following examples. It is not something.

  An embodiment relating to the tactile sensor of the present invention will be described. FIG. 6 is a schematic diagram showing a signal detecting means and a signal processing means in the tactile sensor system. The signal detection means is composed of an elastic body (tactile sensor) that is deformed by contact with an object and three elements (converters) that detect stress or distortion and convert them into electrical signals. As an elastic body having a curved surface, for example, a spherical shell made of Pyrex (registered trademark) glass with a radius of 30.0 mm or a spherical shell made of quartz glass with a radius of 35.0 mm is used, and its outer spherical surface is a contact surface with an object. It was.

  As a strain detector, for example, a strain gauge (KFG-02-120 or KFRS-02-120 manufactured by Kyowa Dengyo Co., Ltd.) was used. These strain gauges are fixed to the bottom of the contact sensor with a cyanoacrylate adhesive. The fixed position is the bottom of the spherical surface that is the contact center position as the strain gauge 1, and the strain gauge 2 and the strain gauge 3 are separated from the position of the contact center by 1.75 mm or 1.0 mm. Adhered and fixed at the position.

  According to the above-described principle, the sensor body 1 may be a flexible non-linear elastic body instead of a linear elastic body such as glass as an elastic body having a curved surface. Further, the shape is not necessarily a spherical shell structure, and a bulk spherical body can be formed by filling a suitable substance after fixing a detection element such as a strain in the inside thereof. A functional material such as a stress-stimulated luminescent material that self-emits according to the amount of mechanical deformation or a composite material in which coiled carbon short fibers are dispersed in a resin matrix can be used.

  Furthermore, in principle, there is no problem in placing a detector for measuring the deformation rate on the outer curved surface that is a contact surface with the object. However, the advantage of placing the strain gage inside the spherical shell structure is that the strain gage and the object do not come into direct contact with each other. It leads to life extension.

The signal processing means is configured by means for amplifying a signal such as a voltage detected by the signal detection means, and storing and calculating the signal. For example, by using a dynamic strain measuring instrument (manufactured by NEC Sanei Co., Ltd., AC dynamic strain measuring instrument AS1103) as a strain conversion amplifier, a resistance change of a strain gauge caused by deformation of an elastic body is output as a voltage change. Can do. This voltage change is sent to a storage circuit / arithmetic circuit of a computer through a general analog / digital converter. For example, when the distortion is measured, the arithmetic processing is based on the relationship between the difference obtained by subtracting the distortion signal at the position away from the distortion signal at the center position and the distortion at the center position according to the equation (1 ′). a process of calculating the index H _Q.

Hardness index H _Q calculated by the calculation processing will be calibrated using a correspondence table or equation created by well-known known materials were. Thus, the hardness index H _Q as defined in the present invention, universally various used hardness, or modulus of elasticity, mechanical properties values representing the deformation resistance, such as rigidity and can correspond with Become.

  FIG. 7 shows the flow from the signal detection means to the signal processing means, the drive angle optimization means, and the tactile information conversion processing means. Existing artificial intelligence can be used for computer processing, including arithmetic processing. It is possible to recognize the hardness and softness of unknown substances by incorporating data on some substances in advance into a knowledge-based artificial intelligence program.

FIG. 8 is a diagram showing a tactile flow chart showing an embodiment of the present invention. Strain division is calculated by detecting strain at three points, and after the shaft center adjustment is completed through two stages of judgment, it shifts to tactile calculation, calculates the strain difference, and calculates the hardness H _Q from the change rate of the strain difference. Then, H is calculated from the correspondence table of the obtained hardness _HQ and hardness H. FIG. 9 shows a state of determination in the first stage of the axis adjustment. The first stage is centered on a determination circuit that satisfies the condition that the output signals from the detection element 2 and the detection element 3 are equal, that is, the condition that ε ₃ / ε ₂ = 1. Here, the rotation angle around the X axis (α (= θx)) and the rotation angle around the Y axis (β (= θy)) are used as control parameters for the contact position, and the contact center coordinates are changed by changing the angle. The output signal ratio ε ₃ / ε ₂ from the detection element 2 and the detection element 3 is calculated, and a determination based on the value is performed. In order to accurately obtain an output signal from the detection element, the contact operation can be performed as follows, but this procedure shows a preferred example of the operation and is not limited thereto. . First, when setting the rotation angle around the X-axis and the rotation angle around the Y-axis for adjusting the contact position, the distance between the contact object and the general tactile sensor is sufficiently separated and not in contact. The output signal level of the detection element (strain gauge) at is set to zero. Next, the drive mechanism is operated to bring the object into contact with the tactile sensor, and simultaneously, output signals from the three detection elements are recorded (stored). Further, signal calculation is started from the moment of contact, and the determination circuit determines the contact position as to whether or not the condition of the output signal ratio ε ₃ / ε ₂ = 1 is satisfied. Here, the contact amount (depth) between the object and the tactile sensor may be within the range of the elastic limit depending on the mechanical properties of the object to be contacted, and it is not necessary to deepen the contact more than necessary. Furthermore, whether the driving for contact is performed by load control or displacement control does not affect the principle of the general tactile sensor. In this example, the load was applied to a maximum load of 2N at a constant speed (2 microns per second, ramp wave), then unloaded, and the object and the tactile sensor were completely separated. By repeatedly performing the above condition setting and determination operations, it is possible to reach a range that satisfies the condition of ε ₃ / ε ₂ = 1. The measurement points indicated by the circles in FIG. 9 are the contact position control parameters that are the rotation angle around the X axis (α (= θx)) and the rotation angle around the Y axis (β (= θy)). The result of changing the center coordinates is shown, and the points indicated by white symbols (◯) mean the conditions where ε ₃ / ε ₂ did not become 1. On the other hand, the points indicated by black circles (●) in the figure are angles that satisfy the condition that ε ₃ / ε ₂ = 1 because the output signals from the detection element 2 and the detection element 3 are equal. A point indicated by a black square (■) on a straight line connecting these black circles (●) and complementing them is based on the expectation that the condition of ε ₃ / ε ₂ = 1 is satisfied. Although the rotation angle around the axis (α (= θx)) and the rotation angle around the Y axis (β (= θy)) are set, in fact, the output signals from the detection element 2 and the detection element 3 are equal, The angle satisfies the condition of ε ₃ / ε ₂ = 1.

FIG. 10 is a load-distortion curve at a stage where the axis adjustment is not performed. Since the detection element 2 and the detection element 3 are located at the same distance from the detection element 1, the output signals from the detection element 2 and the detection element 3 must be equal and ε ₂ = ε ₃ , It can be seen that the contact point is not directly above the detection element 1. FIG. 11 is a load-distortion curve under the condition determined to be true in the determination at the first stage of the axial center adjustment. It can be seen that the output signals from the detection element 2 and the detection element 3 are equal and satisfy the condition of ε ₃ / ε ₂ = 1.

FIG. 12 shows the state of determination in the second stage. This second stage indicates that the contact center is directly above the detection element 1 under the condition determined to be true in the determination of the first stage, and that the ratio of output signals from the detection element 1 and the detection element 2 ε ₂ / epsilon ₁ is a determining circuit to find the condition for the minimum value. The operation procedure for taking out and recording the strain output signal from each detection element by contact is the same as that performed in the first stage, and can proceed in parallel with the calculation in the first stage. The procedure is as follows. Set the output signal level of the sensing element (strain gauge) in a non-contact state to zero. Next, the drive mechanism is operated to bring the object into contact with the tactile sensor, and simultaneously, output signals from the three detection elements are recorded (stored), and from the moment of contact, the detection elements 1 and 2 are detected. The calculation of the output signal ratio ε ₂ / ε ₁ is started. Further, only for those determined to be true by the determination circuit in the first stage, it is determined whether or not the condition that the ratio ε ₂ / ε ₁ of the output signals from the detection element 1 and the detection element 2 is the minimum value is satisfied. I do. FIG. 12 shows the output signals from the detection element 1 and the detection element 2 for the conditions determined by the first stage determination circuit, which are indicated by black circles (●) and black squares (■) in FIG. The ratio ε ₂ / ε ₁ is plotted against the rotation angle around the Y axis (β (= θy)). It can be seen from FIG. 12 that a minimum value of ε ₂ / ε ₁ appears at a point where the rotation angle (β (= θy)) about the Y axis is 0.5 degrees. As a result, the search for the optimum condition in which the contact point is located immediately above the detection element 1 arranged at the center is completed.

FIG. 13 shows silicon nitride ceramics (Si ₃ N ₄ ), silicon carbide ceramics (SiC), alumina ceramics (Al ₂ O ₃ ), zirconia ceramics (ZrO ₂ ), uniaxial carbon fiber reinforced carbon composite materials (measurement objects) 1D-C / C) and six types of inorganic substances of soda lime glass (SL Glass). The horizontal axis in the figure shows the distortion at the contact center position where the contact sensor and the object are in contact, and the vertical axis shows the value obtained by subtracting the distortion at a position 1.75 mm away from the contact center position from the distortion at the contact center position. Plotted. H _Q is the slope of each plot, the value of H _Q shown after the slope at the origin, that is, determined as the slope of the moment of contact.

FIG. 14 shows the results of measurement of four types of metal substances such as carbon steel (SK5), corrosion-resistant steel (stainless steel SUS304), oxygen-free copper (Cu), and aluminum alloy (Al) as measurement objects. The horizontal axis in the figure shows the distortion at the contact center position where the contact sensor and the object are in contact, and the vertical axis shows the value obtained by subtracting the distortion at a position 1.75 mm away from the contact center position from the distortion at the contact center position. Plotted. H _Q is the slope of each plot, the value of H _Q shown after the slope at the origin, that is, determined as the slope of the moment of contact.

Figure 15 is a longitudinal About 10 types of the aforementioned inorganic and metal-based materials, the horizontal axis a Young's modulus obtained by the alternative standard methods (ultrasonic pulse echo method), the H _Q obtained by the method of the present invention A calibration curve plotted as an axis.

FIG. 16 shows the hardness obtained by another standard method (Vickers hardness test method) for 10 types of the above-mentioned inorganic and metallic substances on the horizontal axis, and H _Q obtained by the method of the present invention on the vertical axis. Is a calibration curve plotted as.

FIG. 17 shows the measurement object as fluororesin (hard, PTFE), fluororesin (soft, PTFE), soap (hard), soap (soft), grained paper (thickness 1 mm), paper bundle (thickness 5 mm). , Eraser (for ink), plastic eraser (for pencil) 8 types of measurement results. The horizontal axis in the figure shows the distortion at the contact center position where the contact sensor and the object are in contact, and the vertical axis shows the value obtained by subtracting the distortion at a position 1.75 mm away from the contact center position from the distortion at the contact center position. Plotted. The value of H _Q is slope at the origin of the curve, that is, determined as the slope of the moment of contact.

FIG. 18 shows the results of measurement of six types of woody materials: bamboo (outside), bamboo (inside), cedar, pine, cork (coarse tissue), and cork (fine tissue) as measurement objects. The horizontal axis in the figure shows the distortion at the contact center position where the contact sensor and the object are in contact, and the vertical axis shows the value obtained by subtracting the distortion at a position 1.75 mm away from the contact center position from the distortion at the contact center position. Plotted. The value of H _Q is slope at the origin of the curve, that is, determined as the slope of the moment of contact.

FIG. 19 shows the measurement results obtained by changing the temperature of the measurement environment including the tactile sensor and the object from 35.0 ° C. to 40.0 ° C. by 1 ° C., using food candy as a measurement object. The indentation speed in contact was constant at 1.0 microns per second at all measured temperatures. The horizontal axis in the figure shows the distortion at the contact center position where the contact sensor and the object are in contact, and the vertical axis shows the value obtained by subtracting the distortion at a position 1.75 mm away from the contact center position from the distortion at the contact center position. Plotted. The value of H _Q is slope at the origin of the curve, that is, determined as the slope of the moment of contact.

Figure 20 is a plot for the measured environmental temperature value of H _Q obtained from the foregoing candy. Although the measurement temperature shows a certain hardness from 30.0 ° C. to 35.0 ° C., it can be seen that the hardness decreases as the temperature becomes higher than 35.0 ° C. This boundary temperature was considered to correspond to the glass transition point, and the glass transition temperature was determined to be 35 ° C.

In FIG. 21, the above-mentioned candy was used as the measurement object, the measurement environment temperature including the tactile sensor and the object was constant at 40 ° C., and the contact speed was changed from 1.0 μm / second to 2.5 μm / second. It is a result. The horizontal axis in the figure shows the distortion at the contact center position where the contact sensor and the object are in contact, and the vertical axis shows the value obtained by subtracting the distortion at a position 1.75 mm away from the contact center position from the distortion at the contact center position. Plotted. The value of H _Q is slope at the origin of the curve, that is, determined as the slope of the moment of contact.

Figure 22 is a plot against speed pushing the value of H _Q obtained from the foregoing candy. FIG. 23 shows the measurement results obtained by changing the temperature of the measurement environment including the tactile sensor and the target object from 2.0 ° C. to 10.0 ° C. every 1 ° C. with the food caramel as the measurement target. The indentation speed in contact was constant at 1 micron per second at all measured temperatures. The horizontal axis in the figure shows the distortion at the contact center position where the contact sensor and the object are in contact, and the vertical axis shows the value obtained by subtracting the distortion at a position 1.75 mm away from the contact center position from the distortion at the contact center position. Plotted. The value of H _Q is slope at the origin of the curve, that is, determined as the slope of the moment of contact.

Figure 24 is a plot for the measured environmental temperature value of H _Q obtained from the foregoing caramel. The measurement temperatures of 2.0 ° C. and 3.0 ° C. indicate a certain hardness, but it is understood that the hardness decreases as the temperature becomes higher than 3.0 ° C. This boundary temperature was considered to correspond to the glass transition point, and the glass transition temperature was determined to be 3 ° C.

In FIG. 25, the above-mentioned caramel was used as the measurement object, the measurement environment temperature including the tactile sensor and the object was kept constant at 5 ° C., and the contact speed was changed from 1.0 μm / sec to 3.0 μm / sec. It is a result. The horizontal axis in the figure shows the distortion at the contact center position where the contact sensor and the object are in contact, and the vertical axis shows the value obtained by subtracting the distortion at a position 1.75 mm away from the contact center position from the distortion at the contact center position. Plotted. The value of H _Q is slope at the origin of the curve, that is, determined as the slope of the moment of contact.

Figure 26 is a plot against speed pushing the value of H _Q obtained from the foregoing caramel. Figure 27 is a bar graph showing the order of those soft values obtained H _Q in total 53 conditions 29 items with hard from (caramel) (super-hard ceramics).

  As described above in detail, the present invention relates to a tactile sensor, and according to the present invention, it is possible to provide a tactile sensor that can substitute a human tactile sense and quantitatively measure tactile information. The configuration of the tactile sensor of the present invention has at least three elements for detecting a curved surface of contact with an object and a deformation rate of the curved surface, and uses a spherical deformation signal that is a measurement signal of these detection elements. Since it has an axial center adjustment function that adjusts the center of the curved surface to be the contact center, its configuration is extremely simple, easy to manufacture, inexpensive, and downsized Is possible. With the same sensor, it is possible to quantify the hardness and softness of a wide range of objects ranging from ultra-hard materials such as ceramics to extremely soft materials. The properties of viscoelastic materials can also be quantified. Can be displayed. The present invention provides a new type of high-precision tactile sensor capable of reproducing the sensory characteristics similar to those of a human because the hardness of a substance can be sensed by utilizing the deformation of the tactile sensor itself. It is useful for realizing this.

It is a schematic diagram which shows the contact state of two types of objects and the curved surface from which the ease of a deformation | transformation differs. It is explanatory drawing which approximates the stress distribution or distortion distribution which generate | occur | produces by contact with the stress and the distortion detection element arrange | positioned on the curved surface. It is a schematic diagram of stress distribution or strain distribution when the contact is not perpendicular to the surface of the object. It is a schematic diagram which shows the state where the relationship between the three detection elements of a touch sensor and a contact part (Xc, Yc) is not in agreement. It is explanatory drawing which approximates the stress distribution or distortion distribution which generate | occur | produces by contact with a curved surface (spherical surface) and two types of objects from which the ease of a deformation | transformation differs by the stress or distortion detection element of 2 points | pieces arrange | positioned on the curved surface. . It is a schematic diagram of a tactile sensor system showing an embodiment of the present invention. It is a block diagram of the signal processing circuit which shows the Example of this invention. It is an axial center adjustment and tactile measurement flowchart which shows the Example of this invention. It is a figure which shows the 1st step of the axial center adjustment by the apparatus of FIG. It is a load-distortion curve before performing an axial center adjustment. It is the load-distortion curve determined to be true by the first stage axis adjustment. It is a figure which shows the 2nd step of the axial center adjustment by the apparatus of FIG. It is a strain difference change rate curve of the inorganic type material (ceramics) by the apparatus of FIG. 7 is a strain difference change rate curve of a metal-based material by the apparatus of FIG. It is a figure which shows the relationship between the hardness computed from FIG. 13 and FIG. 14, and the Young's modulus evaluated by the standard test method. It is a figure which shows the relationship between the hardness computed from FIG. 13 and FIG. 14, and the Vickers hardness evaluated by the standard test method. It is a distortion difference change rate curve of the artifact by the apparatus of FIG. It is a strain difference change rate curve of the wood-type material by the apparatus of FIG. It is a strain difference change rate curve in 35 degreeC-40 degreeC of the candy (candy) by the apparatus of FIG. It is a figure which shows the temperature dependence of the hardness computed from FIG. It is a distortion difference change rate curve when the load speed | rate of the candy (candy) by the apparatus of FIG. 6 is 1.0-2.5 microns per second. It is a figure which shows the load speed dependence of the hardness computed from FIG. It is a strain difference change rate curve in 2 degreeC-10 degreeC of the confectionery (caramel) by the apparatus of FIG. It is a figure which shows the temperature dependence of the hardness computed from FIG. It is a distortion difference change rate curve when the load speed of the confectionery (caramel) by the apparatus of FIG. 6 is 1.0 to 3.0 microns per second. It is a figure which shows the load speed dependence of the hardness computed from FIG. It is a bar graph of hardness by the device of FIG.

Claims (11)

  A tactile sensor that has a spherical shell structure whose inner and outer surfaces are spherical, and measures deformations at three different points depending on the strain gauge attached to the inner surface of the spherical shell when the outer surface of the spherical shell comes into contact with the target object. Has at least three detection elements that detect the strain distribution or stress distribution generated on the curved surface by contacting the surface, and the center of the curved surface is the center of contact using the spherical deformation signal that is the measurement signal of these detection elements A tactile sensor characterized by having an axial center adjustment function for adjustment so that   The tactile sensor according to claim 1, wherein the tactile sensor has an axial center adjustment function that detects a strain distribution or a stress distribution generated on a curved surface by contact with an object and adjusts a relative position between a contact center and a detection element. The output signal ε ₁ of the detection element ₁ and the output signals ε ₂ and ε _{3 of} the detection element 2 and the detection element 3 satisfy the condition of ε ₃ / ε ₂ = 1, and ε ₂ / ε ₁ becomes the minimum value. The tactile sensor according to claim 2, wherein the relative position between the contact center and the detection element is adjusted.   The tactile sensor according to claim 1, further comprising a detection element that detects a strain distribution generated on a spherical surface, an aspherical surface, or a non-planar curved surface by contact with an object, or a stress distribution from two different strains or stress values.   The deformation resistance of the contacted material is detected from the change rate of the difference between two different strains measured using electrical, optical, magnetic, or acoustic means, and the hardness and softness of the contacted object are detected. The tactile sensor according to claim 1, wherein the feature is determined.   The tactile sensor according to claim 1, which is provided with a function of recognizing the material of the contact material by quantitatively measuring the deformation of the sensor using a sensor made of a known substance.   The tactile sensor according to claim 1, wherein a strain gauge is disposed inside a spherical shell structure having a curved elastic body.   The tactile sensor according to claim 1, further comprising: signal processing means in which at least three strain gauges are arranged on the elastic curved surface; and signal processing means for processing the signals and calculating a strain difference change rate.   The tactile sensor according to claim 8, wherein the signal processing means includes a distortion conversion amplifier, an analysis value storage means, and an analysis value calculation means.   A strain gauge that detects strain at the center position and non-center position, a means for calculating the hardness of the object from the rate of change of the strain difference, and a means for recognizing the material of the contact material by comparison with numerical values obtained experimentally The tactile sensor according to claim 1.   The data calculated by the analysis value calculation means is compared with existing data and converted into perceptual data, thereby having a function of perceiving deformation resistance such as hardness and softness of an unknown substance. Tactile sensor.