ROBOT APPARATUS, SENSOR APPARATUS, AND CONTROL DEVICE

A robot apparatus according to an embodiment of the present technology includes a hand portion, an elastically deformable sensor portion, and a control device. The hand portion includes at least two finger portions each having a holding surface capable of holding a workpiece. The sensor portion is disposed on the holding surface of at least one finger portion of the two finger portions and includes a plurality of detection elements that detects a pressure acting on the holding surface. The control device includes a signal generation section capable of generating a hold command to cause the hand portion to hold the workpiece with a predetermined holding force and capable of correcting the holding force on the basis of an output of the sensor portion and a duration of an operation of holding the workpiece.

TECHNICAL FIELD

The present technology relates to a robot apparatus that includes a hand portion capable of detecting a pressure acting on a holding surface.

BACKGROUND ART

In recent years, automation of work using a robot has been discussed in various scenes as working population is reduced. There is a need to detect what extent of force is acting on a surface of a robot hand in order to highly accurately control the behavior of the robot hand. For example, Patent Literature 1 below discloses a robot hand that includes a haptic sensor capable of detecting not only a pressing force but also a shear stress or a slide friction.

CITATION LIST

Patent Literature

DISCLOSURE OF INVENTION

Technical Problem

In a robot hand that holds an object (workpiece) in a factory, a shop, or the like, there is a problem that when an indefinite-shaped object, a soft object, a small object, a slippy object, or the like is held, the object will be dropped if the robot hand does not hold the object with an appropriate force. In particular, many stretchy and flexible materials are used in a sensor for detecting a holding force, and due to their viscoelastic behavior, it may be difficult to stably continue to hold the workpiece with a constant holding force.

In view of the circumstances as described above, it is an object of the present technology to provide a robot apparatus, a sensor apparatus, and a control device that are capable of holding a workpiece with a stable holding force.

SOLUTION TO PROBLEM

A robot apparatus according to an embodiment of the present technology includes a hand portion, an elastically deformable sensor portion, and a control device.

The hand portion includes at least two finger portions each having a holding surface capable of holding a workpiece.

The sensor portion is disposed on the holding surface of at least one finger portion of the two finger portions and includes a plurality of detection elements that detects a pressure acting on the holding surface.

The control device includes a signal generation section capable of generating a hold command to cause the hand portion to hold the workpiece with a predetermined holding force and capable of correcting the holding force on the basis of an output of the sensor portion and a duration of an operation of holding the workpiece.

According to the sensor apparatus described above, it is possible to stably hold a workpiece with a constant holding force while suppressing a decrease in the holding force along with a stress relaxation phenomenon.

The signal generation section may be configured to calculate a correction coefficient for correcting the holding force on the basis of drift characteristics of the output of the sensor portion with respect to a constant load acquired in advance.

The signal generation section may be configured to generate the hold command on the basis of an addition value of a pressure value, which is calculated on the basis of a sum of outputs of the plurality of detection elements, and a correction value, which is obtained by multiplying the pressure value by the correction coefficient.

The control device may further include a computing section that calculates a load vertical to the holding surface and a shear force parallel to the holding surface on the basis of the output of the sensor portion.

The hand portion may further include an actuator capable of driving the finger portions at a minimum feed rate of less than 100 μm, and the control device may be configured to control the actuator in a position control cycle of 20 Hz or more.

The sensor portion may include a first pressure sensor located on the workpiece side, a second pressure sensor located on the holding surface side, and a separation layer that is disposed between the first pressure sensor and the second pressure sensor and is made of a viscoelastic material that is deformed by a load applied to the first pressure sensor.

Each of the first pressure sensor and the second pressure sensor may include a sensor electrode layer including a plurality of capacitive elements two-dimensionally disposed in a plane parallel to the holding surface, a reference electrode layer, and a deformation layer disposed between the sensor electrode layer and the reference electrode layer.

The sensor apparatus may further include a viscoelastic body layer. The viscoelastic body layer is configured to be disposed on a surface of the first pressure sensor and made of a viscoelastic material that is deformable on the first pressure sensor in an in-plane direction parallel to the holding surface.

A sensor apparatus according to an embodiment of the present technology includes an elastically deformable sensor portion and a control device.

The sensor portion is disposed on a holding surface of a hand portion of a robot apparatus and detects a pressure acting on the holding surface.

The control device includes a signal generation section capable of generating a hold command to cause the hand portion to hold a workpiece with a constant holding force and capable of correcting the holding force on the basis of an output of the sensor portion and a duration of an operation of holding the workpiece.

A control device according to an embodiment of the present technology includes a signal generation section.

The signal generation section is configured to be capable of generating a hold command to cause a hand portion of a robot apparatus to hold a workpiece with a constant holding force and capable of correcting the holding force on the basis of an output of an elastically deformable sensor portion that detects a pressure acting on a holding surface of the hand portion, and a duration of an operation of holding the workpiece.

MODE(S) FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments according to the present technology will be described with reference to the drawings.

First Embodiment

FIG.1is a perspective view of a main part of a robot apparatus10including a sensor apparatus20according to an embodiment of the present technology. In this embodiment, the robot apparatus10constitutes a robot hand. Hereinafter, a configuration of the robot apparatus10will be schematically described.

As shown inFIG.1, the robot apparatus10includes an arm portion1, a wrist portion2, and a hand portion3.

The arm portion1includes a plurality of joint portions1a, and the hand portion3can be moved to any position by the joint portions1abeing driven. The wrist portion2is rotatably connected to the arm portion1, and the hand portion3can be rotated by the rotation of the wrist portion2.

The hand portion3includes two finger portions3athat face each other, and a target object (workpiece) can be held between the two finger portions3aby the two finger portions3abeing driven. Note that the hand portion3is configured as a two-finger configuration in the example shown inFIG.1, but the number of finger portions3acan be changed appropriately to three, four or more, or the like.

Sensor apparatuses20are provided to the surfaces facing each other of the two finger portions3a. The sensor apparatus20has a pressure detection surface, and is capable of detecting a force that is applied to the pressure detection surface in a vertical direction (Z-axis direction) and is also capable of detecting a force that is applied in an in-plane direction (X-axis direction and Y-axis direction) of the pressure detection surface. In other words, the sensor apparatus20is a three-axis sensor capable of detecting forces corresponding to the directions of the three axes. Note that the configuration of the sensor apparatus20will be described later with reference toFIG.2and the like.

The robot apparatus10is driven by the control of a controller11. The controller11includes a control section, a storage section, and the like. The control section is, for example, a central processing unit (CPU) and controls driving of each portion of the robot apparatus10on the basis of a program stored in the storage section. The controller11may be a dedicated device in the robot apparatus10or may be a general-purpose apparatus. The controller11may be, for example, a personal computer (PC) connected to the robot apparatus10through a wired or wireless connection, a server apparatus on a network, or the like.

FIG.2is a cross-sectional view of the sensor apparatus20as viewed laterally.FIG.3is a plan view of an electrode layer30in the sensor apparatus20.

In each figure of the sensor apparatus20, the X-axis direction and the Y-axis direction are directions parallel to a sensing surface that is a pressure detection surface of the sensor apparatus20(hereinafter, also referred to as in-plane direction), and the Z-axis direction is a direction vertical to the sensing surface (hereinafter, also referred to as vertical direction). Note that, inFIG.2, the upper side corresponds to the front side to which an external force is applied, and the lower side corresponds to the back side opposite to the front side.

As shown inFIGS.2and3, the sensor apparatus20has a shape of a rectangular flat plate as a whole in plan view. Note that, typically, the shape of the sensor apparatus20in plan view only needs to be appropriately set according to the shape of a portion in which the sensor apparatus20is disposed, and the shape of the sensor apparatus20in plan view is not particularly limited. For example, the shape of the sensor apparatus20in plan view may be a polygon other than a rectangle, a circle, or an ellipse.

The sensor apparatus20includes a sensor portion21including a first pressure sensor22a

located on the front side (workpiece side) and a second pressure sensor22blocated on the back side (holding surface side), and a separation layer23disposed between the first pressure sensor22aand the second pressure sensor22b. In other words, the sensor apparatus20has a structure in which the second pressure sensor22b, the separation layer23, and the first pressure sensor22aare stacked in this order from the lower layer side in the vertical direction. Note that, in the following description, the two pressure sensors22aand22bwill be each simply referred to as a pressure sensor22if they are not particularly distinguished from each other.

The sensor apparatus20further includes a viscoelastic body layer81disposed on the upper side (front surface side) of the first pressure sensor22a. As will be described later, the viscoelastic body layer81transmits an external force to the sensor portion21while being deformed according to the external force.

The viscoelastic body layer81is covered with a surface layer24. The surface layer24is made of any flexible material such as a plastic film, a woven fabric, a nonwoven fabric, rubber, or leather. When the robot apparatus10holds a target object using the finger portions3a, the surface layer24becomes a contact surface that comes into contact with the target object and also functions as a pressure detection surface that receives a load (reaction force of holding force) applied by the target object during the holding operation. Therefore, in order to stably hold the target object, the surface layer24favorably has surface properties by which a frictional force equal to or larger than a predetermined value is obtained between the target object and the surface layer24.

Subsequently, the sensor portion21will be described in detail.

The sensor portion21detects a force (shear force Fs) applied to the sensor apparatus20in the in-plane direction on the basis of a pressure center position (pressure detection position) in the in-plane direction detected by the first pressure sensor22aand a pressure center position (pressure detection position) in the in-plane direction detected by the second pressure sensor22b. Further, the sensor portion21detects a force (load Fz) applied to the sensor apparatus20from the upper side in the vertical direction on the basis of a value of the pressure detected by the first pressure sensor22a.

Note that the sensor portion21may detect a force applied to the sensor apparatus20from the upper side in the vertical direction on the basis of two values, the value of the pressure detected by the first pressure sensor22aand the value of the pressure detected by the second pressure sensor22b. In other words, typically, the sensor portion21only needs to be configured to detect a force applied from the upper side in the vertical direction on the basis of the value of the pressure detected by at least the first pressure sensor22ain the first pressure sensor22aand the second pressure sensor22b.

The first pressure sensor22aand the second pressure sensor22bare disposed to face each other in the vertical direction. The first pressure sensor22ahas a structure in which a sensor electrode layer30a, a deformation layer27a, and a reference electrode layer25aare stacked in this order from the lower layer side in the vertical direction via adhesive layers (not shown) therebetween.

Further, the second pressure sensor22bhas a structure in which a reference electrode layer25b, a deformation layer27b, and a sensor electrode layer30bare stacked in this order from the lower layer side in the vertical direction via adhesive layers (not shown) therebetween.

As can be seen from the description herein, the first pressure sensor22aand the second pressure sensor22bare disposed such that their layer arrangements are upside down in the vertical direction. Thus, both the first pressure sensor22aand the second pressure sensor22bhave a configuration in which the sensor electrode layer30is disposed on the separation layer23side. Note that the first pressure sensor22aand the second pressure sensor22bbasically have a similar configuration except that their layer arrangements are upside down in the vertical direction. Note that the first pressure sensor22aand the second pressure sensor22bmay be disposed such that their layer arrangements are the same in the vertical direction.

Note that, in the following description, the two sensor electrode layers30aand30bwill be each simply referred to as a sensor electrode layer30if they are not particularly distinguished from each other, and the two deformation layers27aand27bwill be each simply referred to as a deformation layer27if they are not particularly distinguished from each other. Further, the two reference electrode layers25aand25bwill be each simply referred to as a reference electrode layer25if they are not particularly distinguished from each other.

The sensor electrode layer30includes a flexible printed circuit board or the like. As shown inFIG.3, the sensor electrode layer30includes a main body36that is rectangular in plan view, and an extended portion37that extends outward from the main body36. Note that the shape of the sensor electrode layer30in plan view is not limited to a rectangular shape and can be appropriately changed.

The extended portion37is equipped with a control unit70as a control device that calculates a force in the in-plane direction on the basis of information of the pressure detected by the pressure sensor22. The control unit70is typically a computer including a central processing unit (CPU) and includes an integrated circuit such as an IC chip. The control unit70is mounted on the sensor electrode layer30(extended portion37) of one of the first pressure sensor22aand the second pressure sensor22band is configured to input output signals from the pressure sensors22aand22b. Note that the control unit70is not limited to the example in which the control unit70is mounted on the sensor electrode layer30.

The sensor electrode layer30includes a base material29having flexibility, and a plurality of sensing portions28provided on a front surface of the base material29or provided inside the base material29.

For example, a polymer resin such as polyethylene terephthalate, polyimide, polycarbonate, or an acrylic resin is used as the material of the base material29.

The sensing portions28are regularly arranged in a matrix at predetermined intervals in directions of length and width (length: the Y-axis direction, width: the X-axis direction). In the example shown inFIG.3, the number of sensing portions28is25in total with five×five (length×width). Note that the number of sensing portions28can be appropriately changed. Further, the number of sensing portions28may be the same in the sensor electrode layers30aand30bor may be different from each other.

The sensing portion28includes a capacitive element (detection element) capable of detecting a change in distance from the reference electrode layer25as a change in capacitance. For example, as shown inFIG.4, the sensing portion28includes a comb-teeth-shaped pulse electrode281and a comb-teeth-shaped sense electrode282. The comb-teeth-shaped pulse electrode281and the comb-teeth-shaped sense electrode282are disposed such that their comb teeth face each other. Each sensing portion28includes a region (node area) in which the comb teeth of one of the comb-teeth-shaped pulse electrode281and the comb-teeth-shaped sense electrode282are disposed to enter spaces formed between the comb teeth of the other one of the comb-teeth-shaped pulse electrode281and the comb-teeth-shaped sense electrode282. Each pulse electrode281is connected to a wiring portion281aextending in the Y-axis direction, and each sense electrode281is connected to a wiring portion282aextending in the X-axis direction.

The wiring portions281aare arranged in the X-axis direction on the front surface of the base material29, and the wiring portions282aare arranged in the Y-axis direction on the back surface of the base material29. Each sense electrode282is electrically connected to the wiring portion282avia a through-hole283provided in the base material29. The sensor electrode layer30may include a ground line. The ground line is provided to, for example, an outer peripheral portion of the sensor electrode layer30or a portion in which the wiring portions281aand282aare arranged side by side.

Note that the type of the sensing portion28is not limited to the example described above,

and any type may be used. For example, the sensor electrode layer30may be formed of a laminate of a first electrode sheet having a lattice-shaped first electrode pattern extending in the

X-axis direction and a second electrode sheet having a lattice-shaped second electrode pattern extending in the Y-axis direction. In this case, the sensing portion28is formed at an intersection of the first electrode pattern and the second electrode pattern.

The reference electrode layer25is a so-called grounding electrode and is connected to a ground potential. The reference electrode layer25has flexibility and has a thickness of, for example, approximately 0.05 μm to 0.5 μm. For example, an inorganic conductive material, an organic conductive material, or a conductive material including both the inorganic conductive material and the organic conductive material is used as the material of the reference electrode layer25.

Examples of the inorganic conductive material include metals such as aluminum, copper, and silver, alloys such as stainless steel, and metal oxides such as zinc oxide and indium oxide. Further, examples of the organic conductive material include carbon materials such as carbon black and carbon fibers, and conductive polymers such as substituted or unsubstituted polyaniline and polypyrrole. The reference electrode layer25may be formed of a thin metal plate made of stainless steel, aluminum, or the like, a conductive fiber, a conductive nonwoven fabric, or the like. The reference electrode layer25may be formed on a plastic film by, for example, a method such as vapor deposition, sputtering, bonding, or coating.

The reference electrode layer25constituting the second pressure sensor22bis attached to a surface of the finger portion3aof the robot apparatus10via a support40. The support40is typically an adhesive layer such as a double-sided tape.

The deformation layer27is disposed between the sensor electrode layer30and the reference electrode layer25. The deformation layer27has a thickness of, for example, approximately 100 μm to 1000 μm.

The deformation layer27is configured to be elastically deformable in response to an external force. When an external force is applied to the sensor apparatus20in the vertical direction, the deformation layer27elastically deforms in response to the external force, and the reference electrode layer25approaches the sensor electrode layer30. At that time, a capacitance between the pulse electrode281and the sense electrode282changes in the sensing portion28, and thus the sensing portion28is capable of detecting such a change in capacitance as a pressure value.

The thickness of the deformation layer27is set to be, for example, larger than 100 μm and equal to or less than 1000 μm, and the basis weight of the deformation layer27is set to be, for example, 50 mg/cm2or less. Setting the thickness and the basis weight of the deformation layer27within the above ranges makes it possible to improve the detection sensitivity of the pressure sensor22in the vertical direction.

A lower limit of the thickness of the deformation layer27is not particularly limited unless the lower limit is larger than 100 μm, and the lower limit may be, for example, 150 μm or more, 200 μm or more, 250 μm or more, or 300 μm or more.

Further, an upper limit of the thickness of the deformation layer27is not particularly limited unless the upper limit is 1000 μm or less, and the upper limit may be, for example, 950 μm or more, 900 μm or less, 850 μm or less, or 800 or less.

The deformation layer27may be formed of, for example, a patterning structure including a column structure. Various structures such as a matrix structure, a stripe structure, a mesh structure, a radial structure, a geometric structure, and a spiral structure may be adopted as the patterning structure.

The separation layer23is fixed between the first pressure sensor22aand the second pressure sensor22bvia adhesive layers (not shown). The separation layer23is made of a viscoelastic material that is deformed by a load applied to the first pressure sensor22athrough the surface layer24and the viscoelastic body layer81. Examples of this type of viscoelastic material include a silicon gel, a urethane gel, synthetic rubber, and foam. A thickness of the separation layer23is not particularly limited, and is, for example, 1000 μm or more and 5000 μm or less and set according to a thickness of the viscoelastic body layer81, or the like. A planar shape of the separation layer23is not particularly limited, and is typically rectangular or circular.

The viscoelastic body layer81is disposed between the surface layer24and the first pressure sensor22a(surface of first pressure sensor22a) via adhesive layers (not shown). The viscoelastic body layer81is made of a viscoelastic material that is deformable on the first pressure sensor22ain the in-plane direction. Examples of this type of viscoelastic material include a silicon gel, a urethane gel, synthetic rubber, and foam. The thickness of the viscoelastic body layer81is not particularly limited, and is, for example, 1000 μm or more and 5000 μm or less and set according to the thickness of the separation layer23, or the like.

As will be described later, the viscoelastic body layer81is provided to divide, in the in-plane direction, a multiple-axis force applied to the surface layer24and to detect a shear force distribution (also referred to as shear distribution or multi-point shear) in the surface of the surface layer24. Therefore, the viscoelastic body layer81is favorably made of a viscoelastic material that is more easily deformed in the in-plane direction than the deformation layer27a constituting the first pressure sensor22a.

The sensor apparatus20further includes the control unit70. The control unit70includes a control section, a storage section, and the like. The control section is, for example, a central processing unit (CPU), and executes a program stored in the storage section on the basis of a control command from the controller11, to control driving of each portion in the hand portion3. Typically, the control unit70acquires information of forces in directions of three axes, which are detected by the sensor apparatus20, and controls the driving of the hand portion3so as to stably hold a target object with a suitable holding force on the basis of the information of the forces.

The storage section includes a nonvolatile memory in which various programs and data necessary for processing of the control section are stored, and a volatile memory used as a work area of the control section. Various programs may be read from a portable recording medium such as a semiconductor memory, or may be downloaded from a server apparatus on a network.FIG.5is a block diagram showing a configuration of the control unit70.

The control unit70is electrically connected to the first pressure sensor22aand the second pressure sensor22b, and calculates a vertical load and a shear force distribution on the basis of the pressure detection positions in the in-plane direction, which are detected by the first pressure sensor22aand the second pressure sensor22b.

The control unit70is further electrically connected to the controller11and outputs, on the basis of a control command from the controller11, a hold command to a drive unit12athat drives the finger portions3aof the hand portion3on the basis of the calculated vertical load and shear force distribution.

As shown inFIG.5, the control unit70includes an acquisition section71, a computing section72, a signal generation section73, and a storage section74.

The acquisition section71receives a pressure detection position and a pressure value thereof that are output from the first pressure sensor22a, a pressure detection position and a pressure value thereof that are output from the second pressure sensor22b, and a control command output from the controller11.

Pressure information including the pressure detection positions and the pressure values thereof that are output from the first pressure sensor22aand the second pressure sensor22bis information regarding stress acting on the sensor apparatus20when the hand portion3(finger portions3a) is holding a workpiece. The pressure information typically includes a reaction force of holding, which acts on the sensor apparatus20, a self-weight of the workpiece, a frictional force between the sensor apparatus20and the workpiece, and the like.

The computing section72calculates the forces in the directions of the three axes, which act on the pressure detection surface of the sensor apparatus20, that is, a load vertical to the pressure detection surface and a shear force distribution in the in-plane direction, on the basis of the pressure detection positions in the in-plane direction and the pressure values thereof, which are output from the first pressure sensor22aand the second pressure sensor22b.

The load vertical to the pressure detection surface is calculated by, for example, the sum of the vertical loads acquired by the respective sensing portions28of the first pressure sensor22aand the second pressure sensor22b.

On the other hand, the shear force distribution in the in-plane direction of the pressure detection surface is calculated on the basis of a difference between the pressure center position of the first pressure sensor22aand the pressure center position of the second pressure sensor22b, as will be described later.

The signal generation section73generates a hold command for causing the hand portion3to hold a workpiece on the basis of a control command from the controller11. The hold command includes information regarding the holding force of the hand portion3with respect to the workpiece. The signal generation section73outputs the generated hold command to the drive unit12aof the hand portion3.

The drive unit12ais an actuator that causes the finger portions3aof the hand portion to move between a holding position and a non-holding position. In this embodiment, the drive unit12ais, for example, a pulse motor capable of fine feed control.

The storage section74is typically a semiconductor memory. The storage section74stores a program and various parameters for performing a processing procedure of calculating the shear force distribution in the in-plane direction, on the basis of the pressure detection positions in the in-plane direction, which are output by the first pressure sensor22aand the second pressure sensor22b.

[Principle of Detection of Shear Force in Sensor Portion]

Hereinafter, the principle of detection of a shear force Fs in the sensor portion21will be described.

FIG.6is a diagram showing, as a model, a state in which a load Fz is applied to the sensor portion21downwardly in the vertical direction.FIG.7is a diagram showing, as a model, a state in which a shear force Fs is applied to the sensor portion21in the in-plane direction while a vertical load Fz is being applied to the sensor portion21. Note thatFIGS.6and7show contour lines of detected pressures by circles of broken lines.

As shown inFIG.6, when a load Fz is applied to the sensor portion21downwardly in the vertical direction, a pressure center position P in the in-plane direction, which is detected by the first pressure sensor22a, coincides with a pressure center position Q in the in-plane direction, which is detected by the second pressure sensor22b. Note that the pressure center position refers to a position in the in-plane direction that corresponds to a highest pressure in a detected pressure distribution.

On the other hand, as shown inFIG.7, when a shear force Fs is applied to the sensor portion21in the in-plane direction while a load Fz is being applied to the sensor portion21downwardly in the vertical direction, the pressure center position P in the in-plane direction, which is detected by the first pressure sensor22a, does not coincide with the pressure center position Q in the in-plane direction, which is detected by the second pressure sensor22b.

The separation layer23is distorted in accordance with the shear force Fs applied in the in-plane direction. At that time, the separation layer23generates a shear stress θ corresponding to the shear force Fs. Here, a shear modulus of the separation layer23is represented by G, and the thickness of the separation layer23is represented by t. Further, a difference between the pressure center position P of the first pressure sensor22aand the pressure center position Q of the second pressure sensor22b(hereinafter, also referred to as coordinate displacement) is represented by d (=t×tan θ). In this case, the shear stress o (shear force Fs) is represented by the following equation (1).

Here, the shear modulus G of the separation layer23on the right side of the equation is

known. Therefore, if the coordinate displacement d, which is the difference between the pressure center position P in the in-plane direction of the first pressure sensor22aand the pressure center position Q in the in-plane direction of the second pressure sensor22b, is calculated on the basis of the pressure center position P and the pressure center position Q, the shear stress Fs, that is, a force in the in-plane direction can be detected.

FIG.8is a flowchart for describing a processing procedure (F10) of calculating a shear force. This processing can be performed by, for example, the computing section72of the control unit70.

When a load is applied to the sensor portion21, it is determined whether or not there is a sensing portion28that exhibits an amount of change in capacitance that is equal to or larger than a threshold, among the plurality of sensing portions28(nodes) of the second pressure sensor22b. If there is at least one sensing portion28that exhibits an amount of change in capacitance that is equal to or larger than a threshold (Yes in Step101), an upper limit of a pressure center position (for example, position P) and a lower limit of the pressure center position (for example, position Q) are calculated on the basis of the outputs of the first pressure sensor22aand the second pressure sensor22b(Step102). A shear force is then calculated on the basis of the coordinate displacement calculated from those pressure center positions by using the equation (1) describes above (Step103).

Incidentally, the force acting on the sensing surface of the sensor apparatus20is not limited to a load Fz alone or a shear force Fs alone. The load Fz and the shear force Fs may act at the same time. If the load Fz and the shear force Fs are detected using the sensor portion21alone, the load Fz and the shear force will not be separated from each other. This may make it difficult to detect a shear force distribution in the in-plane direction.

As shown inFIG.9as an example, it is assumed that two pushers Wa and Wb act on the sensor apparatus20at the same time. A load Fz is applied to each of the pushers Wa to be vertically applied to the sensor portion21, and a shear force Fs is applied to only one pusher Wa in any direction (direction approaching the pusher Wb in the illustrated example). The separation layer23is deformed in the in-plane direction in response to the shear force Fs applied to the pusher Wa.

Here, if the pushers Wa and Wb directly act on the sensor portion21without the viscoelastic body layer81, in response to the shear force Fs acting on the pusher Wa, the first pressure sensor22aon the front side easily moves integrally with the separation layer23as shown inFIG.10. In other words, the first pressure sensor22amoves in the in-plane direction relative to the second pressure sensor22bby a predetermined amount (X1in the illustrated example) in response to the deformation of the separation layer23.

As a result, a coordinate displacement X2a(corresponding to d described above) of a shear region (located directly under the pusher Wa) and a coordinate displacement X2b(corresponding to d described above) of a non-shear region (located directly under the pusher Wb) are equal to each other. In other words, despite the fact that only the vertical load Fs acts on the pusher Wb, there is a possibility that an action of the shear force Fs on the pusher Wb is erroneously detected (see Step103inFIG.7). As described above, it is difficult to divide the pressing forces respectively applied by the pushers Wa and Wb only using the sensor portion21. This results in being very difficult to detect a shear force distribution in the in-plane direction.

On the other hand, the sensor apparatus20of this embodiment includes the viscoelastic body layer81on the first pressure sensor22a, and thus the movement of the first pressure sensor22adue to the shear force Fs acting on the pusher Wa can be made smaller.FIGS.11and12are schematic diagrams each showing the relationship between the sensor apparatus20and the pushers Wa and Wb.FIG.11shows a state before the shear force Fs is applied to the pusher Wa, andFIG.12shows a state after the shear force Fs is applied to the pusher Wa.

As shown inFIG.11, the pushers Wa and Wb face the first pressure sensor22avia the viscoelastic body layer81. When the shear force Fs is applied to the pusher Wa in this state as shown inFIG.12, the viscoelastic body layer81and the separation layer23are each deformed in the in-plane direction. At that time, the first pressure sensor22ais deformed by an amount corresponding to the amount of deformation of the viscoelastic body layer81. The first pressure sensor22ais locally deformed, and the deformation of the viscoelastic body81in a region immediately below the pusher Wb is suppressed. Further, since the first pressure sensor22ais deformed along with the deformation of the viscoelastic body layer81, the displacement X1in the in-plane direction is smaller than that in the case where the viscoelastic body layer81is not provided (FIG.9).

As a result, the deformation of the separation layer23in the in-plane direction is also large in a detection region for the pusher Wa and is also small in a detection region for the pusher Wb, so that the coordinate displacement X2bof the non-shear region is made smaller than the coordinate displacement X2aof the shear region. This makes it possible to separate the pressing forces applied by the pushers Wa and Wb from each other, and thus detect an in-plane distribution of the shear force acting on the sensor portion21.

FIG.13is a flowchart showing an example of a processing procedure (F20) performed by the computing section72of the control unit70in the sensor apparatus20of this embodiment.

When a load is applied to the sensor apparatus20, the computing section72determines whether or not there is a sensing portion28that exhibits an amount of change in capacitance that is equal to or larger than a threshold, among the plurality of sensing portions28(nodes) of the second pressure sensor22bon the lower layer side. If there is at least one sensing portion28that exhibits an amount of change in capacitance that is equal to or larger than a threshold (Yes in Step201), the computing section72calculates an upper limit of a pressure center position (for example, position P) and a lower limit of the pressure center position (for example, position Q) on the basis of the outputs of the first pressure sensor22aand the second pressure sensor22b (Step202). The processing so far is similar to the processing procedure described with reference toFIG.8.

Subsequently, the computing section72determines whether or not the coordinate displacement of the pressing force is equal to or larger than a predetermined value (Step203). As described above, the coordinate displacement corresponds to the difference d between the pressure center position P of the first pressure sensor22aand the pressure center position Q of the second pressure sensor22b. When the coordinate displacement is equal to or larger than a predetermined value (Yes in Step203), the computing section72determines that a significant shear force (or slip) is caused on the sensing surface, and calculates a shear force from the equation (1) described above (Step204).

On the other hand, when the coordinate displacement is less than the predetermined value (No in Step203), the computing section72determines that no significant shear force is caused on the sensing surface (Step205). In this case, the computing section72stores an initial value of the pressure center position P of the first pressure sensor22aon the upper layer side (Step206). By the above procedure repeatedly performed in a predetermined cycle, a temporal change in the pressing force applied to the sensor apparatus20is detected.

The predetermined value in Step203can be discretionally set according to thicknesses or areas of the separation layer23and the viscoelastic body layer81, a value of physical properties such as viscoelasticity, ease of deformation of the first pressure sensor22a, an arrangement pitch of the sensing portions28in each of the pressure sensors22aand22b, or the like. The predetermined value described above is favorably set to a value with which it can be determined that a shear force is not substantially caused at a detection point of the pusher Wb due to a shear force applied by the pusher Wa, for example.

The computing section72calculates a suitable holding force with respect to the workpiece on the basis of the calculated value of the shear force calculated in Step204, or the initial value of the pressure center position P stored in Step206. The signal generation section73generates a hold command for controlling the drive unit12aof the hand portion3on the basis of the calculation result of the computing section72.

FIG.14is a block diagram showing an example of a control system of the robot apparatus10. The robot apparatus10includes the controller11and a drive section12that drives the arm portion1, the hand portion3, and the like. The drive section12includes the drive unit12athat drives the finger portions3a. The controller11is configured to be capable of executing a control program for operating the robot apparatus10on the basis of input signals from various sensors.

The sensor apparatus20constitutes one of the various sensors described above, and is attached to a holding surface for a target object in the hand portion3. On the basis of a control command from the controller11, the sensor apparatus20outputs a hold command for holding a workpiece to the drive unit12a, which drives the finger portions3aof the hand portion3. The sensor apparatus20detects a pressing force (pressure distribution, holding force (vertical load), or shear force) acting on the sensing surface in the sensor portion21, calculates a value of the above-mentioned pressing force in the control unit70, and inputs the calculated value to the controller11. The controller11generates a drive signal for controlling the positions of the arm portion1and the hand portion3(finger portions3a), and outputs the drive signal to the drive section12. The drive section12is typically an actuator such as an electric motor or a fluid pressure cylinder, and drives the arm portion1, the hand portion3, and the like on the basis of the drive signal from the controller11.

As described above, in this embodiment, the hold control of the hand portion3is configured to be performed in the control unit70of the sensor apparatus20. The present technology is not limited to the above, and the controller11may directly output a hold command to the drive unit12ato perform the hold control of the hand portion3. In this case, the control unit70of the sensor apparatus20performs only the functions of calculating a pressure acting on the sensor portion21and of outputting the calculated pressure to the controller11.

As shown inFIG.15, an operation example of transporting a workpiece T, which is a target object placed on a placing surface S, to another location, and a processing procedure performed in the controller11and the control unit70will be described as an example.

[Operation of Holding Workpiece]

After setting an initial position, which is a position to hold a workpiece T, the controller11outputs a control command for narrowing a hand position (facing distance between finger portions3a) to the control unit70(Steps301and302).

When the finger portions3acome into contact with the workpiece T and when a target value for detecting a holding force (typically, pressing force acting on the sensor apparatus20when the finger portions3acome into contact with workpiece T) is obtained, the control unit70performs control such that the workpiece T is held by the hand portion3(Steps303and304).

At that time, the control unit70adjusts the position of the hand portion3(a posture of the hand portion3or the facing distance between the finger portions3a) to control the holding force with respect to the workpiece T or a shear force acting on the sensor apparatus20(Step305).

The controller11then controls the holding force or the like of the hand portion3so as to lift the workpiece T and stably hold the target object (Steps306and307).

Note that the holding force is controlled using the distance between the finger portions3aof the hand portion3such that a reaction force (stress) caused by the holding operation takes a target value. The control method is not particularly limited, and typically, PID control is employed. A reaction force of the holding operation is calculated on the basis of the sum of the outputs (pressure values) of the sensing portions28constituting the pressure sensor22of the sensor apparatus20. The target value is discretionally set according to the type, size, shape, and the like of the workpiece T.

The feed accuracy of the drive unit12ais not particularly limited, but for example, it is favorable that the drive unit12abe configured by an actuator capable of driving the finger portions3aat a minimum feed rate of less than 100 μm. Further, in order to highly accurately control the drive unit12awith such fine feed accuracy, it is favorable that the control unit70be configured to be capable of generating a hold command for the drive unit12ain a position control cycle of 20 Hz or more, for example.

[Operation of Moving Workpiece]

Subsequently, the control unit70holds the hand portion3and further adjusts the holding force as will be described later (Step308). After that, the controller11performs control such that the arm portion1is moved to a destination (Step309). At that time, a shear force or the like acting on the hand portion3may change due to the influence of inertia or the like caused by the movement of the arm portion1. The controller11or the control unit70adjusts the posture or the holding force of the hand portion3to perform control such that the stable holding of the workpiece T is maintained (Step310).

[Operation of Letting Go of Workpiece]

When the workpiece T reaches a target position, the controller11performs control such that the movement of the arm portion1is stopped. In this case as well, when the shear force or the like acting on the hand portion3changes due to the influence of inertia or the like, the hand portion3is controlled such that the stable holding of the workpiece T is maintained, and then an operation of lowering the arm is performed (Steps311and312). When the workpiece T is placed on the placing surface S, the controller11stops the operation of lowering the arm portion1. The control unit70outputs a hold release command for releasing the holding operation by the hand portion3to the drive unit12aon the basis of the control command from the controller11, and performs control such that the holding force to the workpiece T is released (Step313).

The pressing force applied to the sensor apparatus20and the holding force of the hand portion3have a linear correlation as shown inFIG.16, and the pressing force increases in proportion to the holding force. An adjustment range of the holding force for the workpiece T is different between the operation of holding the workpiece T, the operation of moving the workpiece T, and the operation of letting go of the workpiece T. Typically, the holding force is adjusted in the range of the arrow Cl during the holding operation, in the range of the arrow C2during the moving operation, and in the range of the arrow C3during the operation of letting go.

FIG.17is a flowchart showing the details of the processing procedure of the holding operation performed in the control unit70.

Step305includes Step305aof controlling the hand position and Step305bof detecting the holding force. For example, the holding force is determined on the basis of the vertical load Fz and the in-plane distribution of the shear force Fs, which are output from the sensor apparatus20, and the hand portion3is controlled such that the holding force takes a target value.

Further, Step306includes Step306aof detecting the shear force Fs and Steps306band306cof resetting a target value of a position and posture of the hand portion or a target value of the holding force so as to stabilize the holding operation on the basis of the shear force Fs.FIG.18is a flowchart showing the details of the processing procedure of the operation of moving the workpiece T.

The step of checking whether or not the workpiece T is stably held is included as Step307a. Step308includes Step308aof controlling the hand position and Step308bof detecting the holding force.

Further, Step309includes Step309aof detecting the shear force Fs and Steps309band309cof resetting a target value of a position and posture of the hand portion or a target value of the holding force so as to stabilize the holding operation on the basis of the shear force Fs.

FIG.19is a flowchart showing the details of the processing procedure of the operation of letting go of the workpiece T.

The step of checking whether or not the workpiece T is stably held is included as Step310a. Step311includes Step311aof controlling the hand position and Step311bof detecting the holding force.

Further, Step312includes Step312aof detecting the shear force Fs and Steps312band312cof resetting a target value of a position and posture of the hand portion or a target value of the holding force so as to stabilize the holding operation on the basis of the shear force Fs.

FIG.20shows a side view of a main part, showing various configuration examples of the hand portion3. In the figure, a region indicated by hatching represents the sensor apparatus20.

FIG.20shows, on the upper left, a two-finger parallel plate gripper, in which the sensor apparatus20is disposed on the inner surface of each finger portion3a.

FIG.20also shows, on the upper right, a two-finger parallel plate gripper, which differs in that a distal end3a1of each finger portion3ahas a curved shape. The sensor apparatus20disposed on the inner surface of each finger portion3ais disposed so as to cover the distal end3a1of the finger portion3a, so that not only the holding force but also a contact force with the distal end3a1can be detected.

FIG.20also shows, on the left in the middle part, a two-finger parallel plate gripper, which is an example in which the sensor apparatus20is disposed only on one finger portion3a.

FIG.20shows, on the right in the middle part, a three-finger gripper, in which the sensor apparatus20is disposed on the inner surface of each finger portion3a.

FIG.20shows, on the lower left, a two-finger gripper, which is an example in which a fingertip3bis connected to the distal end of each finger portion3avia a pivotable portion P. In this case, the sensor apparatus20is disposed on the inner surface of each of the finger portion3aand the fingertip3b.

FIG.20shows, on the lower right, a two-finger rotary gripper that is rotatable at a pivotable portion P, which is an example in which the sensor apparatus20is disposed on the inner surface of each finger portion3a.

FIG.21shows an example of the in-plane distribution of the shear force Fs, which is detected by the sensor apparatus20disposed on the inner surface of each finger portion3a, in a two-finger parallel plate gripper. Here, it is assumed that a sensor apparatus disposed on a finger portion3aon one side (for example, left side) is a sensor apparatus20L, and a sensor apparatus disposed on a finger portion3aon another side (for example, right side) is a sensor apparatus20R. When a slip occurs to rotate a target object held between the finger portions3aabout an axis parallel to the holding direction, each of the sensor apparatuses20L and20R detects the in-plane distribution of the shear force Fs as shown in the figure. In this case, the in-plane distribution of the shear force Fs is detected symmetrically in each of the sensor apparatuses20L and20R. Therefore, the in-plane distribution of the shear force Fs acting on the finger portion3acan be detected with high accuracy.

[Regarding Control of Holding Force]

In a robot hand that holds an object (workpiece) in a factory, a shop, or the like, there is a problem that when an indefinite-shaped object, a soft object, a small object, a slippy object, or the like is held, the object will be dropped if the robot hand does not hold the object with an appropriate force.

In order to solve such a problem, there has been conventionally known a method of controlling the holding force by monitoring a state of a current of a motor constituting a holding mechanism. However, a motor capable of controlling a precise holding force is a dedicated product equipped with PWM control or a torque sensor, which is very expensive.

Further, there is known a method in which a sensor capable of detecting a pressure is mounted on a holding surface or a fingertip of the hand, and an optimal holding force is provided by feeding back the sensor output thereof. However, in the conventional pressure sensor of this type, detection of a pressure at a point is main stream, and a detection region does not extend in the two-dimensional planar direction. This leads to a problem that a dead-zone region is generated during holding.

On the other hand, according to the robot apparatus10of this embodiment, the sensor apparatus20capable of detecting a pressure distribution is disposed on the finger portion3aof the hand portion3, and a holding force is controlled on the basis of a detection result, which makes it possible to reduce the dead-zone region as much as possible and to hold the workpiece

T with a suitable holding force. This holding force can be achieved by adjusting the distance between the finger portions3a.

Further, according to this embodiment, the sensor apparatus20is configured to be capable of detecting not only the pressure distribution but also a shear force distribution. Thus, even if a slip occurs between the hand portion3and the workpiece held by the hand portion3due to a self-weight of the workpiece or an inertial force acting on the workpiece, the slip can be reliably detected, and thus the holding force can be increased until the slip stops, thereby preventing the workpiece from falling.

On the other hand, in order to detect the pressure distribution and the shear force distribution, the sensor apparatus20of this embodiment has a structure using a large number of elastic layers that are elastically deformable, such as the separation layer23, the viscoelastic layer81, and the deformation layer27. If a constituent material exhibits a viscoelastic behavior, the sensor apparatus20including the elastic layers in its structure may have a reduced stress when it is retained under a constant strain. In other words, a stress relaxation phenomenon may occur, in which an actual holding force decreases even if pressure information detected by the sensor is constant. This phenomenon is thought to be due to the physical behavior in which a material does not immediately reach equilibrium and deformation proceeds over time due to viscoelasticity. The inventors of the present technology have also confirmed that the decrease in pressing force gradually becomes larger as the duration of the holding operation becomes longer. Therefore, even if a workpiece is held with a target holding force, it may be difficult to stably keep holding the workpiece with a constant holding force, depending on the holding force and the duration of the holding operation.

In order to suppress the drift of the sensor output that causes the decrease in actual holding force due to the stress relaxation phenomenon as described above, the control device70of this embodiment is configured to be capable of correcting the holding force on the basis of the output of the sensor portion21and the duration of the operation of holding the workpiece.

FIG.22is a block diagram showing a configuration of the signal generation section73in the control device70. The signal generation section73generates a hold command supplied to the drive unit12athat drives the finger portions3aof the hand portion3. As shown in the figure, the signal control section72includes a pressure signal generation section731, a correction signal generation section732, a correction coefficient generation section736, a multiplier733, an adder734, a PID controller735, and a correction coefficient generation section736.

The pressure signal generation section731calculates a pressure signal including information regarding a pressure acting on the sensor apparatus20from the total value of the outputs (pressure values) of the plurality of sensing portions28two-dimensionally arranged and constituting the sensor portion21. In this example, the number of sensing portions28is144in total with 12×12. The sensing portions28may be the sensing portions28of the first pressure sensor22a, the sensing portions28of the second pressure sensor22b, or the sensing portions28of both the first pressure sensor22aand the second pressure sensor22b.

The correction signal generation section732generates a correction signal on the basis of the output of a plurality of any sensing portions28(hereinafter, also referred to as sampling sensors) among the12×12sensing portions28, and a correction coefficient generated by the correction coefficient generation section736to be described later. The output of the sampling sensors is a representative value of a sampling sensor group of each block, for example, when all of the sensing portions two-dimensionally arranged is divided into 3×3 blocks each including 16 (4×4) regions. The representative value is, for example, an average value of the outputs of the sampling sensor group of each block, but the present technology is not limited thereto. The sum of the outputs of the sampling sensor groups, a maximum value of the outputs of the sampling sensor groups, the output of a sensing portion located at the center of each block, and the like may be adopted.

The correction signal generated by the correction signal generation section732is multiplied by the pressure signal in the multiplier733, and then added to the pressure signal in the adder734, so that a feedback signal to be input to one input terminal of the PID controller735is generated.

The PID controller735compares the feedback signal with a target value signal to be input to the other input terminal, and generates a hold command such that the feedback signal takes the target value. The generated hold command is output to the drive unit12a, and thus the holding force of the hand portion3is controlled.

The correction coefficient generation section736samples a drift curve737regarding a temporal change of the sensor output as shown inFIG.22at regular time intervals. Each sampling value is a representative value of the sensor output at each time. In this case, the sampling value is, for example, an instantaneous value at the start of sampling. The correction coefficient generation section736acquires a difference from the target value of the sensor output at each sampling time and generates, as a correction coefficient, a value obtained by multiplying the output of the sampling sensor by a conversion parameter whose value gradually decreases at each sampling time.

Here, the drift curve737indicates drift characteristics of the output of the sensor portion21with respect to a constant load acquired in advance, and is stored in the storage section74(seeFIG.5). The drift curve737is a temporal change of a value obtained by converting, as a sensor output, the actual holding force that is reduced by the above-mentioned stress relaxation phenomenon of the elastic layers. At the start of holding, a sensor output corresponding to the target value is obtained, but the output gradually decreases with the lapse of the holding time.

A value corresponding to the reduced output is multiplied by a conversion parameter assigned to each sampling time, and the correction coefficient is sequentially updated in synchronization with the sampling time. The conversion parameter is appropriately set in accordance with, for example, creep characteristics peculiar to the material of the elastic layers constituting the sensor apparatus. Typically, the conversion parameter is any number equal to or larger than 0 and less than 1, and in this example, set within 0 to 5% of the target sensor output. Further, the conversion parameter may be set in accordance with the layer structure of the sensor apparatus, the form of the elastic layer, and the like as in the embodiments to be described later.

As described above, the signal generation section73generates the hold command on the basis of the addition value of the pressure value, which is calculated on the basis of the sum of the outputs of the plurality of sensing portions28, and the correction value, which is obtained by multiplying the pressure value by the correction coefficient. Since the correction coefficient thus generated is sequentially updated at the sampling intervals as described above, the pressure value as a feedback signal to be input to the PID controller735is also gradually decreased. As a result, since a difference from the target value increases, a hold command that increases the holding force so as to cancel the difference is output from the PID controller735. Note that at the start of the holding operation, the drift characteristics reach the target value of the sensor output, and thus the correction coefficient is zero.

FIG.23is a diagram showing an example of the temporal change of the hold command output from the signal generation section73. As shown in the figure, the signal generation section73is configured to correct the holding force on the basis of the output of the sensor portion21and the duration of the holding operation. Thus, the actual holding force can be increased as indicated by the arrows in the figure so as to cancel the stress relaxation phenomenon of each elastic layer constituting the sensor apparatus20. This makes it possible to stably hold the workpiece with a constant holding force regardless of the duration of the holding operation.

The correction coefficient generation section736may be configured by software or may be configured by any digital circuit. As the digital circuit, for example, digital filters such as finite impulse response (FIR) can be employed. If the conversion parameter is appropriately set in advance, this makes it possible to appropriately correct the stress relaxation phenomenon in which the holding force as shown inFIG.23decreases in a curvilinear manner from the start of holding and asymptotically approaches to a specific value.

Second Embodiment

FIG.24is a cross-sectional side view showing a configuration of a sensor apparatus50according to a second embodiment of the present technology. Hereinafter, configurations different from those in the first embodiment will be mainly described, and configurations similar to those in the first embodiment will be denoted by similar reference symbols, and description thereof will be omitted or simplified.

In the sensor apparatus50of this embodiment, the configuration of a separation layer230is different from that of the first embodiment.FIG.25is a view of the separation layer230of the sensor apparatus50as viewed from the rear side. Hereinafter, details of the separation layer230will be mainly described below.

The separation layer230includes gap portions33and includes a plurality of pillar portions34formed by the gap portions33and extending in the vertical direction. The gap portion33is provided in a groove shape that does not vertically penetrate the separation layer230on the back surface side (the second pressure sensor22bside) of the separation layer230.

The separation layer230includes an infilling layer31(first layer) having an infilling structure without the gap portions33, on the front side (the first pressure sensor22aside).

Further, the separation layer23includes a pillar layer32(second layer) including the gap portions33and the plurality of pillar portions34formed by the gap portions33on the back side (on the second pressure sensor22bside).

Each of the plurality of pillar portions34has a shape that is not constant in thickness in the vertical direction, and has a shape having a different thickness. In the example shown inFIGS.24and257, the plurality of pillar portions34is formed so as to have a thickness gradually reduced from the front side (the first pressure sensor22aside) to the back side (the second pressure sensor22bside) in the vertical direction. Specifically, each of the plurality of pillar portions34has a shape of an inverted frustum of a quadrangular pyramid. Note that the pillar portions34may have a shape of, for example, an inverted frustum of a cone, an inverted frustum of a triangular pyramid, an inverted frustum of a pentagonal pyramid, or an inverted frustum of a hexagonal pyramid.

The pillar portions34are regularly arranged lengthwise and widthwise. Each of the pillar portions34is provided at a position corresponding to the sensing portion28in the vertical direction. Thus, the gap portions33used to form the pillar portions34are provided at positions not corresponding to the sensing portions28in the vertical direction. The number of pillar portions34is the same as the number of sensing portions28bin the second pressure sensor22b, that is,25in total with five x five (length x width). Note that the number of pillar portions34can be appropriately changed.

The separation layer230has a thickness of, for example, approximately 1000 μm to 5000 μm. The height of the pillar portion34in the vertical direction (that is, the depth of the groove-shaped gap portion33) is, for example, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, or 45% or more of the thickness of the separation layer23. Note that it is not a problem if the pillar portion34has a large height (for example, 100% of the thickness of the separation layer230). However, there is a possibility that the pillar portion34will not work effectively if the height of the pillar portion34is too small (for example, a height less than 20% of the thickness of the separation layer230).

The area (in-plane direction) of a lower surface of the pillar portion34(a portion being in contact with the second pressure sensor22b) is set in accordance with the area of the sensing portion28bof the second pressure sensor22b, and is, for example, an area equal to the area of the sensing portion28b.

The separation layer230is typically made of a viscoelastic material having viscoelastic characteristics. Examples of the material used for the separation layer230include a silicon gel, a urethane gel, synthetic rubber, and foam.

The sensor apparatus50of this embodiment configured as described above includes the separation layer230having the configuration as described above. This makes it possible to improve the detection sensitivity to the shear force.

In other words, since the separation layer230includes the gap portions33in this embodiment, when a shear force Fs is applied, the separation layer230is locally distorted in the in-plane direction in which the shear force Fs is caused, and the distortion is less transmitted to portions other than the locally distorted portion. The state of being easily locally distorted (shearing stress σ) is uniformly provided regardless of a point in the in-plane direction. Thus, in this embodiment, the detection sensitivity to the shear force Fs is uniformly provided in the in-plane direction.

Further, the separation layer230includes the gap portions33in this embodiment. Thus, the separation layer230is easily distorted (the shear stress o is reduced) in response to the shear force Fs at each point in the in-plane direction, so that the detection sensitivity to the shear force Fs is improved.

Further, in this embodiment, the pillar portions34formed by the gap portions33are provided at positions corresponding to the sensing portions28of the second pressure sensor22b. Therefore, when a vertical load Fz is applied to the sensor apparatus20, the pillar portions34locally press the portions corresponding to the sensing portions28in the second pressure sensor22b, so that such a force can be efficiently transmitted in the second pressure sensor22b. Therefore, even if the load Fz in the vertical direction is small, the pressure center position Q can be precisely detected in the second pressure sensor22b, and the shear force Fs can be precisely measured.

Further, the configuration of the separation layer230described above may be similarly applied to the viscoelastic body layer81as will be described later. Also in this case, the viscoelastic body layer81is easily distorted in response to the shear force Fs at each point of the viscoelastic body layer81in the in-plane direction, so that the detection sensitivity to the shear force Fs can be improved. The above-mentioned configuration of the separation layer230is applicable to at least one of the separation layer23or the viscoelastic body layer81inFIG.2.

Third Embodiment

FIG.26is a cross-sectional side view showing a configuration of a sensor apparatus60according to a third embodiment of the present technology. Hereinafter, configurations different from those in the first embodiment will be mainly described, and configurations similar to those in the first embodiment will be denoted by similar reference symbols, and description thereof will be omitted or simplified.

In the sensor apparatus60of this embodiment, the configuration of a viscoelastic body layer810is different from that of the first embodiment. The viscoelastic body layer810is configured to be similar to the separation layer230described in the second embodiment, and the back surface of the viscoelastic body layer810is formed in a concavo-convex shape as shown inFIG.25.

In other words, the viscoelastic body layer810includes gap portions33and includes a plurality of pillar portions34formed by the gap portions33and extending in the vertical direction. The gap portion33is provided in a groove shape that does not vertically penetrate the viscoelastic body layer810on the back surface side (the second pressure sensor22bside) of the viscoelastic body layer810. Each of the plurality of pillar portions34has a shape that is not constant in thickness in the vertical direction, and has a shape having a different thickness.

In the example shown inFIG.26, the plurality of pillar portions34is formed so as to have a thickness gradually reduced from the front side (the surface layer24side) to the back side (the first pressure sensor22aside) in the vertical direction. Specifically, each of the plurality of pillar portions34has a shape of an inverted frustum of a quadrangular pyramid. Note that the pillar portions34may have a shape of, for example, an inverted frustum of a cone, an inverted frustum of a triangular pyramid, an inverted frustum of a pentagonal pyramid, or an inverted frustum of a hexagonal pyramid.

The pillar portions34are regularly arranged lengthwise and widthwise. Each of the pillar portions34is provided at a position corresponding to the sensing portion28in the vertical direction. Thus, the gap portions33used to form the pillar portions34are provided at positions not corresponding to the sensing portions28in the vertical direction. The number of pillar portions34is the same as the number of sensing portions28bin the second pressure sensor22b, that is,25in total with five×five (length×width). Note that the number of pillar portions34can be appropriately changed.

The viscoelastic body layer810has a thickness of, for example, approximately 1000 μm to 5000 μm. The height of the pillar portion34in the vertical direction (that is, the depth of the groove-shaped gap portion33) is, for example, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, or 45% or more of the thickness of the viscoelastic body layer810. Note that it is not a problem if the pillar portion34has a large height (for example, 100% of the thickness of the viscoelastic body layer810). However, there is a possibility that the pillar portion34will not work effectively if the height of the pillar portion34is too small (for example, a height less than 20% of the thickness of the viscoelastic body layer810).

The area (in-plane direction) of a lower surface of the pillar portion34(a portion being in contact with the first pressure sensor22a) is set in accordance with the area of the sensing portion28aof the first pressure sensor22a, and is, for example, an area equal to the area of the sensing portion28a.

The viscoelastic body layer810is typically made of a viscoelastic material having viscoelastic characteristics. Examples of the material used for the separation layer810include a silicon gel, a urethane gel, synthetic rubber, and foam. For the shape of the viscoelastic body layer810, various shapes can be employed similarly to the separation layer230in the second embodiment described above.

Also in the sensor apparatus60of this embodiment configured as described above, similarly to the second embodiment described above, it is possible to improve the detection sensitivity to the shear force. In other words, since the viscoelastic body layer810includes the gap portions33in this embodiment, when a shear force Fs is applied, the viscoelastic body layer810is locally distorted in the in-plane direction in which the shear force Fs is caused, and the distortion is less transmitted to portions other than the locally distorted portion. The state of being easily locally distorted (shearing stress σ) is uniformly provided regardless of a point in the in-plane direction. Thus, in this embodiment, the detection sensitivity to the shear force Fs is uniformly provided in the in-plane direction.

Fourth Embodiment

FIG.27is a perspective view schematically showing a sensor apparatus90according to a fourth embodiment of the present technology. As in the first embodiment, a sensor apparatus90of this embodiment includes a first pressure sensor220aon the upper layer side that is the sensing surface side, a second pressure sensor220bon the lower layer side, and a separation layer23disposed between the first pressure sensor220aand the second pressure sensor220b. Note that the illustration of a viscoelastic body layer81disposed on the upper layer side of the first pressure sensor220ais omitted.

Here, a state is shown, in which through four pushers W1to W4, a vertical load Fz in the Z-axis direction and a shear force Fs in the X-axis direction simultaneously act on the sensor apparatus90. Four points P1to P4on the first pressure sensor220aand four points Q1to Q4on the second pressure sensor220brespectively represent center positions at which the pressures acting through the pushers W1to W4are detected (pressure center positions).

This embodiment is different from the first embodiment described above in that each of the first pressure sensor220aand the second pressure sensor220bis divided into a plurality of detection regions.FIG.28is a schematic plan view parallel to the XY-plane, showing division examples of the detection regions of the first pressure sensor220aand the second pressure sensor220b.

As shown inFIG.28, the first pressure sensor220ais divided into four detection regions A1to A4, and the second pressure sensor220bis also divided into four detection regions B1to

B4. A vertical load Fz and a shear force Fs that act on the detection region A1of the first pressure sensor220athrough the pusher W1are detected in the detection region B1of the second pressure sensor220b. Similarly, vertical loads Fz and shear forces Fs that act on the detection regions A2to A4of the first pressure sensor220athrough the pushers W2to W4are respectively detected in the detection regions B2to B4of the second pressure sensor220b.

The first pressure sensor220aand the second pressure sensor220bare divided into the plurality of detection regions A1to A4and the plurality of detection regions B1to B4, respectively, which makes it possible to accurately detect the loads and shear forces that act on the detection regions without each detection region being affected by another detection region.

For example,FIG.29schematically shows the distributions of pressures in the respective detection regions A1to A4of the first pressure sensor220athrough the pushers W1to W4. On the right in the figure, a plurality of square regions in each of the detection regions A1to A4corresponds to the sensing portions28(seeFIG.3) that are nodes, and pressure detection values thereof are represented by grayscale (darker represents a higher pressure detection value, and lighter represents a lower pressure detection value).

When the pushers W1to W4are rotated about the same rotational axis in this state while being pressed with the hand as indicated by the arrow C on the left inFIG.30, the distribution of pressure in each of the detection regions A1to A4changes, for example, as shown on the right in

FIG.30. In other words, this case indicates that a region that exhibits a high pressure expands in each of the detection regions A1to A4, and the pressure center positions of the respective detection regions A1to A4move along the moving directions of the pushers W1to W4.

Further,FIG.31shows in-plane distributions of shear forces in the four detection regions (regions1to4), which are determined in consideration of temporal changes in the respective pressure center positions in the detection regions B1to B4of the second pressure sensor220b.

In this embodiment, the detection regions A1to A4of the first pressure sensor220aare

set such that a portion of a certain region overlaps with a portion of another region. When a detection surface of the first pressure sensor220ais equally divided into four with two in length and two in width, portions of detection region A1are set so as to overlap with portions of the other detection regions A2and A3adjacent thereto in a width direction and a length direction, as indicated by hatching, for example, on the left inFIG.28. Thus, the number of sensors (the number of sensing portions28) in each detection region is increased. This makes it possible to, for example, prevent pressure detection data on a peripheral edge of the detection region from missing and improve the detection accuracy at the pressure center positions P1to P4.

Note that the present technology is not limited to the above, and each of the detection regions A1to A4may be provided without overlapping with each other, as in the case of the divided regions B1to B4of the second pressure sensor220b.

The first pressure sensor220aand the second pressure sensor220bare divided into the four detection regions A1to A4and B1to B4, respectively, but the present technology is not limited thereto and may be divided into two, three, or five or more regions.

The number of divisions and the size (extent) of the detection regions A1to A4and B1to B4may be set in advance, or may be variably set in accordance with the number, position, and the like of loads acting on the first pressure sensor220a. In this case, it is possible to optimize the setting of the detection regions in a case where the load acting on the sensor apparatus90changes from moment to moment. Thus, it is possible to detect a pressure or shear force distribution with high accuracy.

Note that the sensing portions28constituting the first pressure sensor220aand the second pressure sensor220bdo not necessarily exhibit a linear change in capacitance with respect to the pressing force in some cases. Thus, a correction algorithm that linearly approximates a change in capacitance that is exhibited by each sensing portion28with respect to a pressing force may be employed.

FIGS.32and33are flowcharts each showing a processing procedure of calculating a shear force detected in each of the detection regions A1to A4and B1to B4, the processing procedure being performed in the control unit70(seeFIG.3).

A processing procedure F10ashown inFIG.32is a processing procedure similar to the processing procedure F10shown inFIG.8, and a processing procedure F20ashown inFIG.33is a processing procedure similar to the processing procedure F20shown inFIG.13.

In both the cases, if any of the sensing sections28(nodes) of the second pressure sensor220bexhibits an amount of change in capacitance that is equal to or larger than a threshold (Yes in Steps101and201), the first pressure sensor220aand the second pressure sensor220bare respectively divided into a plurality of detection regions A1to A4and B1to B4(Steps102aand202a). After that, pressure center positions P1to P4and Q1to Q4are calculated for the respective divided detection regions to calculate shear forces Fs acting on the respective detection regions (Steps102b,202b,103, and204).

Note that the sensor apparatus90of this embodiment is applicable not only to the sensor apparatus described in the first embodiment but also to the sensor apparatuses in the second to third embodiments.

Modified Examples

In the embodiments described above, the sensor apparatus in which the viscoelastic body layer81or810is disposed on the front surface side of the first pressure sensor22ahas been exemplified, but the installation of the viscoelastic body layer81or810may be omitted. Further, the sensor portion21includes the two pressure sensors (first pressure sensor22aand second pressure sensor22b), but the sensor apparatus may include any one of the pressure sensors. In this case, the installation of the separation layer23or230can be omitted.

Further, in the embodiments described above, a hold command supplied to the drive unit12athat drives the finger portions3aof the hand portion3is generated by the control unit70of the sensor apparatus, but instead of this, it may be performed by the controller11that controls the entire operation of the robot apparatus10. In this case, the controller11corresponds to a control device that includes a signal generation section that generates a correction signal for correcting a holding force on the basis of a pressure value calculated by the control unit70and a duration of a holding operation.

Note that the present technology can also take the following configurations.

(1) A robot apparatus, including:a hand portion including at least two finger portions each having a holding surface capable of holding a workpiece;an elastically deformable sensor portion that is disposed on the holding surface of at least one finger portion of the two finger portions and includes a plurality of detection elements that detects a pressure acting on the holding surface; anda control device including a signal generation section capable of generating a hold command to cause the hand portion to hold the workpiece with a predetermined holding force and capable of correcting the holding force on the basis of an output of the sensor portion and a duration of an operation of holding the workpiece.
(2) The robot apparatus according to (1), in whichthe signal generation section calculates a correction coefficient for correcting the holding force on the basis of drift characteristics of the output of the sensor portion with respect to a constant load acquired in advance.
(3) The robot apparatus according to (2), in whichthe signal generation section generates the hold command on the basis of an addition value of a pressure value, which is calculated on the basis of a sum of outputs of the plurality of detection elements, and a correction value, which is obtained by multiplying the pressure value by the correction coefficient.
(4) The robot apparatus according to any one of 81) to (3), in whichthe control device further includesa computing section that calculates a load vertical to the holding surface and a shear force parallel to the holding surface on the basis of the output of the sensor portion.
(5) The robot apparatus according to any one of (1) to (4), in whichthe hand portion further includesan actuator capable of driving the finger portions at a minimum feed rate of less than 100 μm, andthe control device controls the actuator in a position control cycle of 20 Hz or more.
(6) The robot apparatus according to any one of (1) to (5), in whichthe sensor portion includesa first pressure sensor located on the workpiece side,a second pressure sensor located on the holding surface side, anda separation layer that is disposed between the first pressure sensor and the second pressure sensor and is made of a viscoelastic material that is deformed by a load applied to the first pressure sensor.
(7) The robot apparatus according to (6), in whicheach of the first pressure sensor and the second pressure sensor includesa sensor electrode layer including a plurality of capacitive elements two-dimensionally disposed in a plane parallel to the holding surface,a reference electrode layer, anda deformation layer disposed between the sensor electrode layer and the reference electrode layer.
(8) The robot apparatus according to (6) or (7), in whichthe sensor portion further includesa viscoelastic body layer that is disposed on a surface of the first pressure sensor and made of a viscoelastic material that is deformable on the first pressure sensor in an in-plane direction parallel to the holding surface.
(9) A sensor apparatus, including:an elastically deformable sensor portion that is disposed on a holding surface of a hand portion of a robot apparatus and detects a pressure acting on the holding surface; anda control device includinga signal generation section capable of generating a hold command to cause the hand portion to hold a workpiece with a constant holding force and capable of correcting the holding force on the basis of an output of the sensor portion and a duration of an operation of holding the workpiece.
(10) A control device, includinga signal generation section capable of generating a hold command to cause a hand portion of a robot apparatus to hold a workpiece with a constant holding force and capable of correcting the holding force on the basis of an output of an elastically deformable sensor portion that detects a pressure acting on a holding surface of the hand portion, and a duration of an operation of holding the workpiece.

REFERENCE SIGNS LIST