Gripping apparatus and method for determining gripping state

Abstract

Provided is a gripping apparatus that is capable of gripping an article by means of a bag body by utilizing the jamming transition, and that makes it possible to determine the gripping state of an article with a simple configuration. A gripping apparatus 10 capable of gripping an article MO comprises: a drive unit 12; a support member 13 that can be operated by the drive unit 12; a detection unit 14 that detects a voltage; a bag body 40 that is provided to the support member 13, is formed of an elastomer, is elastically deformable according to the shape of the article MO, and is capable of outputting a voltage toward the detection unit 14 upon sensing contact pressure associated with contact with the article MO; a mixture CM that is housed in the bag body 40 and is composed of granules CP and a fluid CA; and a pressure regulating unit 20 that regulates the pressure of the fluid CA housed in the bag body 40 in a state in which the shape of the bag body 40 is maintained.

Description

Gripping device and method for determining gripping state

[0001] The present invention relates to a gripping device and a method for determining a gripping state.

[0002] A known grasping device having a gripper that utilizes jamming transition is described in JP 2013-523478 A (hereinafter referred to as Patent Document 1). The device described in Patent Document 1 is a passive gripping and releasing device that includes a deformable membrane having an opening fluidically connected to a source of inlet and outlet fluid in a releasable sealing relationship, at least one port that provides the source of inlet and outlet fluid and is disposed in fluid connection with the opening of the membrane, and a granular material disposed within the membrane.

[0003] A gripper utilizing jamming transition presses an object to be gripped against the surface of a bag (corresponding to the membrane in Patent Document 1) containing a fluid-like mixture (corresponding to the granular material in Patent Document 1), causing the object to be elastically deformed to match the outer shape of the object. With the object in a state of elastic deformation due to the object being gripped, the mixture in the bag transitions from a fluid-like state to a solid-like state, allowing the gripper to grip the object and move it for handling or other purposes. Such a gripper utilizing jamming transition can deform into a shape that allows it to grip various objects having various outer shapes with a single bag, as long as it can grip the object and elastically deform it.

[0004] In a gripping device having a manipulator capable of gripping an object using multiple actuators, a method using a mechanical device such as a push button is known as one method for determining the gripping state of the manipulator. The mechanical device is provided on the manipulator. The mechanical device outputs a voltage upon contact with an object. The gripping device having the manipulator determines the gripping state of the manipulator based on the detection result of the voltage output from the mechanical device upon contact with the object. However, if a mechanical device is provided on a bag body of a gripper that uses jamming transition, there is a risk that the rigidity of the mechanical device will prevent the bag body from deforming into a shape that can grip an object. On the other hand, if an optical device such as a camera is used as a method for determining the gripping state of a gripper that uses jamming transition, the configuration of the determination system using that method will be more complex than when a mechanical device is used.

[0005] The present disclosure aims to provide a gripping device capable of gripping an object with a bag body utilizing jamming transition, which is capable of determining the gripping state of the object with a simple configuration. The present disclosure also aims to provide a method for determining the gripping state with a simple configuration when an object is gripped with a bag body utilizing jamming transition.

[0006] An aspect of the present disclosure is a gripping device capable of gripping an object, comprising: a drive unit; a support member operable by the drive unit; a detection unit that detects voltage; a bag body provided on the support member, formed from an elastomer, and elastically deformable to match the outer shape of the object, the bag body being capable of sensing contact pressure associated with contact with the object and outputting a voltage to the detection unit; a mixture of particles and a fluid contained in the bag body; and a pressure adjustment unit that adjusts the pressure of the fluid contained in the bag body while maintaining the shape of the bag body.

[0007] Another aspect of the present disclosure is a method for determining a gripping state, which comprises: bringing a bag containing a mixture of particles and a fluid, the bag containing a predetermined amount of the fluid into contact with the article, thereby elastically deforming the bag in a tight fit to match the outer shape of the article, and outputting a voltage from the bag; reducing the pressure on the mixture while maintaining the tight fit of the bag, thereby causing a jamming transition, thereby transitioning the bag from a softened state to a hardened state and gripping the article; storing the value of the voltage output from the bag when the bag transitions from the softened state to the hardened state as a reference value; and determining the gripping state of the bag by checking whether the difference between the value of the voltage output from the bag in the hardened state and the reference value exceeds a predetermined threshold.

[0008] According to the gripping device of the present disclosure, a gripping device capable of gripping an item with a bag body utilizing jamming transition can be provided that is capable of determining the gripping state of an item with a simple configuration.

[0009] According to the method for determining the gripping state of the present disclosure, when an article is gripped by a bag body that utilizes jamming transition, a method for determining the gripping state can be provided with a simple configuration.

[0010] Fig. 1 is a schematic diagram of a gripping device according to an embodiment. Fig. 2 is a block diagram of a gripping device according to an embodiment. Fig. 3 is a schematic diagram of a gripping device according to a modified example. Fig. 4 is a schematic diagram of a gripping device according to a modified example. Fig. 5 is a schematic diagram showing a state before a gripping device according to an embodiment grips an article. Fig. 6 is a schematic diagram showing a state after a gripping device according to an embodiment grips an article. Fig. 7 is a schematic diagram showing a state after a gripping device according to an embodiment grips an article and is separated from a platform. Fig. 8 is a schematic diagram showing a state after an article gripped by a gripping device according to an embodiment has fallen off. Fig. 9 is a flowchart showing the flow of a method for determining a gripping state according to an embodiment.

[0011] Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings. The drawings are not necessarily drawn to scale, and some features may be exaggerated or omitted. In the following description, the vertical direction (up-down direction) is referred to as the X direction. The vertically upward direction is referred to as the +X direction. The vertically downward direction is referred to as the -X direction.

[0012] As shown in FIG. 1 , the gripping device 10 according to the present disclosure is an articulated robot capable of handling an object MO placed on a platform TA and moving it to a destination platform (not shown). As shown in FIG. 1 , the gripping device 10 includes a drive unit 12, a support member 13, a gripper 30, a detection unit 14, and a control unit 11. As shown in FIG. 2 , the gripping device 10 further includes a notification unit 15. The drive unit 12 of the embodiment includes a motor and a gearbox (not shown). The drive unit according to the present disclosure may include a linear actuator. The operation of the motor of the drive unit 12 is controlled by the control unit 11. The support member 13 is columnar and extends in one direction. The support member 13 includes a first end 13 a and a second end 13 b. The first end 13 a is connected to the drive unit 12. The second end 13 b is opposite the first end 13 a. The support member 13 can be operated by the drive unit 12. In the gripping device 10 of the embodiment, the drive unit 12 is further connected to other support members and other drive units (not shown).

[0013] As shown in FIG. 1 , the gripper 30 is connected to the second end 13b. The gripper 30 is capable of gripping an object MO. Details of the gripper 30 will be described later. The detection unit 14 detects a voltage output from the gripper 30. The detection unit 14 can transmit the detected voltage value to the control unit 11. The notification unit 15 notifies the state of the gripping device 10. The notification unit 15 is, for example, a display monitor. The notification unit 15 may be a patrol lamp. The notification unit 15 may have an audio output function. The control unit 11 controls each part of the gripping device 10. Specifically, as shown in FIG. 2 , the control unit 11 controls the operation of the drive unit group, the notification unit 15, and the gripper 30. The drive unit group is composed of multiple drive units including the drive unit 12. The gripping device 10 is operable to move the gripper 30 closer to the object MO by controlling the operation of the drive unit group with the control unit 11. Details of the control unit 11 will be described later.

[0014] <Gripper 30> As shown in FIG. 1, the gripper 30 has a base 32, a cover 34, a bag body 40, a mixture CM, a stopper part 36, and a fluid control part 20.

[0015] The base 32 is box-shaped. The base 32 is connected to the second end 13b of the support member 13. In the embodiment, one surface of the base 32 facing the second end 13b is connected to the second end 13b. The base 32 supports each part of the gripper 30. The base 32 can accommodate each part of the gripper 30 inside. The base 32 in the embodiment can accommodate a terminal portion 50a, a port portion 36a, and a piping 25, which will be described later.

[0016] The cover 34 is provided on one side of the base 32 facing in a direction different from the support member 13 side. The cover 34 in this embodiment is provided on one side of the base 32 facing away from the second end 13b of the support member 13. The cover 34 is bowl-shaped and opens toward the side opposite the base 32 side. The cover 34 has a hole 35. The hole 35 penetrates the cover 34 along the central axis of the cover 34. The hole 35 can support the outer surface of a mouth 44 of the bag body 40, which will be described later. The cover 34 exposes the storage section 46 of the bag body 40 from the opening of the bowl-shaped cover 34. As a result, the outer shape of the bag body 40 supported by the cover 34 forms a round-bottom container shape that is narrowed at the mouth 44. The cover 34 protects the area around the mouth 44 of the bag body 40.

[0017] The stopper portion 36 is cylindrical. The stopper portion 36 is arranged so as to contact the inner surface of the mouth portion 44 of the bag body 40. The cylindrical side surface of the stopper portion 36 seals the inner surface of the mouth portion 44 supported by the hole portion 35. In this embodiment, the stopper portion 36 is arranged inside the mouth portion 44 and is fixed to the cover 34 or the base portion 32 using connecting members (not shown) including bolts.

[0018] The stopper portion 36 has a port portion 36a. The port portion 36a is tubular and allows the fluid CA to pass between the inside of the bag body 40 sealed by the stopper portion 36 (the side of the storage portion 46 described later) and the outside of the bag body 40. The port portion 36a has a filter portion 36b and a connection end 36c. The filter portion 36b is provided at the end of the port portion 36a facing the storage portion 46 side of the bag body 40. The filter portion 36b allows the fluid CA to pass through. The filter portion 36b prevents the passage of particles CP. The connection end 36c is the end of the port portion 36a opposite the filter portion 36b. The connection end 36c is connected to the piping 25 of the fluid control unit 20 described later.

[0019] The fluid control unit 20 controls the amount of fluid CA contained in the bag body 40 through the port portion 36a. The fluid control unit 20 adjusts the pressure of the fluid CA contained in the bag body 40. That is, the fluid control unit 20 adjusts the pressure inside the bag body 40. The fluid control unit 20 is an example of a pressure adjustment unit. The fluid control unit 20 can create a vacuum inside the bag body 40.

[0020] The fluid control unit 20 has a pump unit 24, a pipe 25, a tank unit 26, and a pipe 27. The pump unit 24 flows the fluid CA into or out of the pipe connected to the pump unit 24. The operation of the pump unit 24 is controlled by the control unit 11. That is, the operation of the fluid control unit 20 is controlled by the control unit 11. The pipe 25 connects the port unit 36a and the pump unit 24 so that the fluid CA can flow therethrough. The tank unit 26 is a pressure vessel that stores the fluid CA. The pipe 27 connects the tank unit 26 and the pump unit 24 so that the fluid CA can flow therethrough. Note that if the fluid CA is air, the fluid control unit 20 does not need to include the tank unit 26 and the pipe 27. In this case, the pump unit 24 can discharge air from within the bag body 40 to the outside of the gripper 30. In this case, the pump unit 24 can introduce air from outside the gripper 30 into the bag body 40.

[0021] <Bag 40> As described above, the bag 40 is supported by the cover 34 provided on the support member 13, and thus has a narrow, round-bottomed container shape. The bag 40 has a main body 42 and a pressure-sensing unit 50.

[0022] As shown in FIG. 1 , the main body 42 is a hollow bag-like structure supported by the cover 34 and configured as a narrowed, round-bottomed container. The cross-sectional shape of the main body 42 is generally U-shaped, narrowed at the opening. In the following description, the axial direction of the main body 42, which is configured as a narrowed, round-bottomed container, is referred to as the longitudinal direction of the bag body 40. The main body 42 is formed from an elastomer molded into a thin membrane. The elastomer preferably includes, for example, ethylene propylene diene rubber (EPDM), acrylic rubber (ACM), nitrile rubber (NBR), fluororubber (FKM), chloroprene rubber, silicone rubber, or urethane rubber. The elastomer may be piezoelectric rubber. Piezoelectric rubber will be described in detail below. The main body 42 has a mouth 44, a storage portion 46, and a tip portion 47.

[0023] The mouth 44 is the open end of the bag-shaped main body 42, which has a narrowed round-bottom container shape. The mouth 44 includes the narrowed portion of the main body 42, which has a narrowed round-bottom container shape. The storage section 46 is located on the bottom side of the main body 42, which has a narrowed round-bottom container shape, relative to the mouth 44. The storage section 46 is connected to the mouth 44. The storage section 46 is approximately spherical. The storage section 46 is capable of storing a mixture CM, which will be described later, inside. The tip 47 is the end of the storage section 46 on the opposite side from the mouth 44 side. When the gripper 30 of the embodiment grips an item MO, the tip 47 is closest to the item MO than other parts of the main body 42.

[0024] When the mixture CM is fluid-like, the main body 42 (particularly the storage portion 46) can elastically deform its surface shape to match the outer shape (surface shape) of the object MO upon contact with the object MO (see FIG. 6). At this time, the bag 40 is in a state of tight contact with the object MO. Here, "fluid-like" means that the mixture CM behaves like a fluid within the bag 40, conforming to the shape of the bag 40 that stores the mixture CM. On the other hand, "solid-like" means that the mixture CM does not behave like a fluid within the bag 40.

[0025] The pressure-sensitive unit 50 senses the contact pressure caused by contact between the main body 42 and the object MO and outputs a voltage to the detection unit 14. In other words, the pressure-sensitive unit 50 exhibits a piezoelectric effect. By having the pressure-sensitive unit 50, the bag body 40 can sense the contact pressure caused by contact with the object MO and output a voltage to the detection unit 14. The pressure-sensitive unit 50 does not inhibit the elastic deformation of the main body 42.

[0026] The pressure-sensing unit 50 is, for example, a main body 42 formed of piezoelectric rubber. Piezoelectric rubber is an elastomer that exhibits a piezoelectric effect. Piezoelectric rubber includes a piezoelectric material and a rubber matrix. The piezoelectric material is in the form of particles that exhibit a piezoelectric effect. The piezoelectric material preferably includes, for example, lead zirconate titanate, barium titanate, lithium niobate, lead titanate, lead metaniobate, polyvinylidene fluoride, or quartz. The rubber matrix is ​​an elastomer that holds the piezoelectric material. The rubber matrix preferably includes, for example, nitrile rubber, fluororubber, chloroprene rubber, silicone rubber, or urethane rubber. Piezoelectric rubber can be formed, for example, by a method described in Japanese Patent No. 5046367, Japanese Patent Laid-Open No. 60-120579, or Japanese Patent Laid-Open No. 54-157297.

[0027] When the pressure-sensing unit 50 is a main body 42 made of piezoelectric rubber, the main body 42 has a terminal 50a, as shown in FIG. 1. The terminal 50a outputs a voltage generated by the piezoelectric effect of the main body 42 made of piezoelectric rubber. The terminal 50a is connected to the detection unit 14, as shown in FIG. 1. In this case, the bag 40 is connected to the detection unit 14 through the terminal 50a, as shown in FIG. 2. The terminal 50a of the embodiment is housed in the box-shaped base 32, as shown in FIG. 1. The terminal 50a according to the present disclosure may be located on the outer surface of a portion of the main body 42 that does not come into contact with the item MO.

[0028] The pressure-sensitive unit 50 may be a piezoelectric film 52. The piezoelectric film 52 is a film that exhibits a piezoelectric effect. The piezoelectric film 52 is flexible. The piezoelectric film 52 preferably contains, for example, vinylidene fluoride, tetrafluoroethylene, trifluoroethylene, a polyamino acid material, or a cellulose derivative.

[0029] The piezoelectric film 52 may be sandwiched between flexible sheets and formed into a layer. The piezoelectric film 52 sandwiched between the sheets can be formed by, for example, the methods described in JP 2011-222679 A, ​​JP 2020-119995 A, or WO 2022 / 091829 A.

[0030] As shown in FIG. 3 , the piezoelectric film 52 is disposed so as to cover the outer surface of the main body portion 42. The piezoelectric film 52 is fixed to the main body portion 42 with, for example, an adhesive or a tape member. In FIG. 3 , the piezoelectric film 52 is illustrated spaced apart from the main body portion 42 to clearly show the piezoelectric film 52. The piezoelectric film 52 is elastically deformable to conform to the surface shape of the main body portion 42. When the bag 40 comes into contact with the item MO, the main body portion 42 comes into contact with the item MO via the piezoelectric film 52 and elastically deforms. At this time, the piezoelectric film 52 elastically deforms together with the main body portion 42.

[0031] The piezoelectric film 52 has a terminal portion 52a. The terminal portion 52a outputs a voltage generated by the piezoelectric effect of the piezoelectric film 52. The terminal portion 52a is connected to the detection unit 14 as shown in FIG. 3. In this case, the bag 40 is connected to the detection unit 14 through the terminal portion 52a as shown in FIG. 2. The terminal portion 52a in this embodiment is housed in the box-shaped base 32 as shown in FIG. 3. The terminal portion 52a may be located on the outer surface of a portion of the bag 40 that does not come into contact with the item MO.

[0032] The pressure-sensitive unit 50 may be a pressure-sensitive sensor 53. The pressure-sensitive sensor 53 is strip-shaped and exhibits a piezoelectric effect. The pressure-sensitive sensor 53 is flexible. As shown in FIG. 4, the pressure-sensitive sensor 53 is disposed along the outer surface of the main body 42. The pressure-sensitive sensor 53 has a strip portion 53c, an element portion 53b, and a terminal portion 53a.

[0033] The belt portion 53c is arranged along the main body portion 42, spanning from the tip portion 47 to the mouth portion 44. The belt portion 53c is flexible. The belt portion 53c has a conductor portion and a covering portion (not shown). The conductor portion extends along the longitudinal direction of the belt portion 53c. The conductor portion allows electricity to flow between both ends of the belt portion 53c. The covering portion covers and protects the surface of the conductor portion. The belt portion 53c may be layered, with the conductor portion sandwiched between the covering portions.

[0034] The element portion 53b is a piezoelectric element that exhibits a piezoelectric effect. The element portion 53b is positioned so as to contact at least the object MO when the gripper 30 grips the object MO. In the embodiment, the element portion 53b is provided at the end of the band portion 53c on the tip portion 47 side. The element portion 53b is preferably protected by a covering portion 53e. The pressure sensor 53 according to the present disclosure may have a plurality of element portions 53b provided at predetermined intervals on each portion of the conductor portion 53d in the longitudinal direction of the band portion 53c. As shown in FIG. 4, the element portion 53b may be positioned so as to overlap the tip portion 47 of the main body portion 42. The element portion 53b may be positioned away from the tip portion 47.

[0035] The terminal portion 53a outputs a voltage generated by the piezoelectric effect of the element portion 53b. In this embodiment, the element portion 53b is provided at the end of the band portion 53c on the mouth portion 44 side. The terminal portion 53a is connected to the detection unit 14 as shown in FIG. 4. In this case, the bag body 40 is connected to the detection unit 14 through the terminal portion 53a as shown in FIG. 2. In this embodiment, the terminal portion 53a is housed in the box-shaped base 32 as shown in FIG. 4. The terminal portion 53a may be located on the outer surface of a part of the bag body 40 that does not come into contact with the item MO.

[0036] The bag 40 shown in Fig. 4 has one pressure sensor 53. When the pressure-sensing unit 50 is a pressure sensor 53, the bag 40 may have multiple pressure sensors 53. In this case, the multiple pressure sensors 53 are arranged radially in each direction along the radial direction, centered on the tip end 47 of the main body 42, and extend along the outer surface of the main body 42 toward the mouth 44.

[0037] The mixture CM is contained in the container 46 of the bag 40, as shown in each of Figures 1, 3, and 4. The mixture CM includes at least granules CP. The mixture CM may also include a fluid CA. The granules CP preferably have a particle size of 0.1 mm to 4 mm. The granules CP are, for example, coffee powder obtained by grinding coffee beans. The granules CP may be rice grains, glass beads, sawdust, or diatomaceous earth. The fluid CA is, for example, a gas such as air. The fluid CA may also be a liquid such as water.

[0038] The mixture CM contained in the bag 40 can undergo a pseudo-phase transition (jamming transition) between a fluid-like state and a solid-like state by controlling the amount of the fluid CA by the fluid control unit 20. That is, the mixture CM contained in the bag 40 can undergo a pseudo-phase transition (jamming transition) between a fluid-like state and a solid-like state by controlling the pressure of the fluid CA inside the bag 40 by the fluid control unit 20.

[0039] Specifically, the fluid-like mixture CM is contained in the bag 40 in a state where it contains granules CP and a fluid CA. At this time, the granules CP form gaps between the granules CP. At this time, the fluid CA fills the gaps formed by the granules CP. If an external force is applied to the bag 40 at this time, the mixture CM flows in accordance with the deformation of the bag 40 that accompanies the application of the external force. In other words, when the mixture CM is fluid-like, the bag 40 is in a state where it can flexibly deform in response to the applied external force. The state of the bag 40 at this time is called a softened state.

[0040] The fluid control unit 20 is operated to discharge the fluid CA from the bag 40 containing the mixture CM including particles CP and fluid CA. The particles CP then come into close contact with each other. At this time, the gaps that formed when the mixture was in a fluid-like state disappear. At this time, the mixture CM is composed solely of particles CP. At this time, the mixture CM transitions from a fluid-like to a solid-like state. In this disclosure, "transition" refers to a "pseudo-phase transition." That is, when the pressure inside the bag 40 containing the mixture CM including particles CP and fluid CA is reduced by the fluid control unit 20, the mixture CM transitions from a fluid-like to a solid-like state. If an external force is applied to the bag 40 at this time, the solid-like mixture CM acts to make the bag 40 less likely to deform. That is, when the mixture CM contained therein is solid-like, the bag 40 enters a state in which it appears to have been hardened by the mixture CM. The state of the bag 40 at this time is referred to as a hardened state. When the pressure inside the bag 40, which contains the mixture CM containing the particles CP and the fluid CA, is reduced by the fluid control unit 20, the bag 40 transitions from the softened state to the hardened state.

[0041] When the fluid control unit 20 is operated to flow fluid CA into the bag 40 containing the solid-like mixture CM, the mixture CM becomes in a state containing the fluid CA and transitions from a solid-like to a fluid-like state. That is, when the pressure inside the bag 40 containing the mixture CM composed only of particles CP is increased by the fluid control unit 20, the mixture CM transitions from a solid-like to a fluid-like state. When the pressure inside the bag 40 containing the mixture CM composed only of particles CP is increased by the fluid control unit 20, the bag 40 transitions from a hardened state to a softened state.

[0042] As shown in FIG. 2 , the control unit 11 is electrically connected to a group of drive units including the drive unit 12, the detection unit 14, the notification unit 15, and the gripper 30. As described above, the control unit 11 controls each unit of the gripping device 10. The control unit 11 has a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an interface. The ROM stores programs executed by the CPU. The RAM stores parameters and the like used in the programs executed by the CPU. The interface communicates with devices electrically connected to the control unit 11.

[0043] The control unit 11 has a memory unit 11a. The memory unit 11a is a storage device such as an HDD or SSD. The memory unit 11a is capable of storing information related to the determination unit 11b. The information related to the determination unit 11b includes a reference value VB and a predetermined threshold value VC. The threshold value VC is set in advance by an operator (not shown) before the gripping device 10 operates. The information related to the determination unit 11b includes information sent to the notification unit 15 based on the determination result of a determination unit 54b (described later).

[0044] The control unit 11 functions as a determination unit 11b by a program executed by the CPU. The determination unit 11b determines the gripping state of the bag body 40. The determination unit 11b transmits the determination result of the gripping state of the bag body 40 to the notification unit 15. Details of the operation of the control unit 11 will be described below together with the operation of the gripping device 10 and the method of determining the gripping state.

[0045] <Method of Determining the Grip State> Here, the operation of the gripping device 10 and a method of determining the grip state when an object MO placed on a table TA is gripped by the gripper 30 and then moved from the table TA to another table and placed thereon will be described with reference to Figures 5 to 9. The other table is placed at a predetermined position.

[0046] First, as shown in Figure 5, the gripper 30 is positioned vertically above the object MO on the platform TA. At this time, the bag 40 contains a mixture CM containing particles CP and a fluid CA. At this time, the mixture CM is fluid-like. At this time, the value of the pressure P inside the bag 40 is PB.

[0047] Next, the control unit 11 controls the drive unit group to move the gripper 30 vertically downward as shown in FIG. 6, so that the object MO is brought into contact with the bag body 40 so as to sink into it. At this time, the bag body 40 elastically deforms in a tight fit to match the outer shape of the object MO (step S30 in FIG. 9). At this time, the pressure-sensing unit 50 is not in contact with the table TA. In other words, it is preferable that the bag body 40 is not in contact with the table TA. At this time, as the bag body 40 comes into contact with the object MO, the pressure-sensing unit 50 outputs a voltage V to the detection unit 14. The value of the voltage V detected by the detection unit 14 is transmitted to the control unit 11.

[0048] Next, the control unit 11 controls the fluid control unit 20 to discharge the fluid CA from the bag 40 in the sealed state. That is, as shown in FIG. 9 , the control unit 11 controls the fluid control unit 20 to reduce the pressure of the mixture CM in the bag 40 while maintaining the sealed state of the bag 40 (step S40). At this time, the value of the pressure P in the bag 40 is PV. At this time, the mixture CM in the bag 40 transitions from a fluid-like state to a solid-like state. At this time, the bag 40 grasps the item MO and enters a gripping state in which it can be moved, such as for handling. At this time, the value of the voltage V output from the bag 40 to the detection unit 14 is V1. The control unit 11 stores the value of the voltage V1 transmitted from the detection unit 14 in step S40 in the memory unit 11a as a reference value VB (step S42).

[0049] Next, the control unit 11 controls the group of drives to move the gripper 30 gripping the item MO vertically upward, lifting the item MO from the table TA, as shown in Figure 7. The control unit 11 then further controls the group of drives to move the gripper 30 gripping the item MO to a preset position. That is, the control unit 11 moves the bag body 40 gripping the item MO from the table TA to a preset position (step S50).

[0050] During the movement period in which the bag 40 gripping the item MO moves from the platform TA to a preset position, the determination unit 11b determines the gripping state of the bag 40 based on the value of the voltage V output from the bag 40 and a reference value VB stored in the memory unit 11a. Specifically, the determination unit 11b checks whether the difference between the value of the voltage V output from the bag 40 and the reference value VB exceeds the threshold value VC stored in the memory unit 11a (step S52).

[0051] 7, during the period when the gripper 30 is gripping the item MO by the gripping device 10, the bag 40 outputs a voltage V that is substantially the same as the voltage V1 in step S40. At this time, the value of the voltage V output from the bag 40 becomes a value V2 (≈V1) that has a difference from the voltage V1 due to vibrations and the like that accompany the operation of the drive unit group for moving the item MO. The difference between the value of the voltage V2 output from the bag 40 and a reference value VB is smaller than the threshold value VC (|V2-VB|≦VC). At this time, the determination unit 11b determines in step S52 that the gripper 30 is maintaining the gripped state and gripping the item MO.

[0052] Thereafter, the control unit 11 determines whether the bag body 40 has moved to a preset position based on the state of the drive unit group (step S54). If the bag body 40 has not moved to the preset position, the process returns to step S52. Steps S52 and S54 are repeated at preset time intervals until the bag body 40 has moved to the preset position.

[0053] When the bag 40 has moved to a predetermined position, the control unit 11 further controls the drive unit group to move the gripper 30 closer to another platform located at a predetermined position so as to place the gripped object MO on the other platform. The control unit 11 then controls the fluid control unit 20 to flow the fluid CA into the bag 40. That is, the control unit 11 controls the fluid control unit 20 to pressurize the mixture CM in the bag 40 (step S70). At this time, the mixture CM in the bag 40 transitions from a solid-like state to a fluid-like state. At this time, the gripped state of the item MO by the bag 40 is released. The item MO is then released from the gripper 30. The control unit 11 then controls the drive unit group to move the bag 40 away from the item MO (step S72).

[0054] Now, let us consider a case where a problem such as the item MO falling from the bag 40 occurs during the movement of the item MO by the gripping device 10 in step S50. As shown in FIG. 8 , when the gripper 30 is not gripping the item MO, the bag 40 outputs a voltage V3. At this time, the pressure-sensing unit 50 of the bag 40 is not in contact with the item MO, so the voltage V3 output from the bag 40 is a different value from the voltage V1 output when the gripper 30 is in a gripped state. At this time, the difference between the value of the voltage V3 output from the bag 40 and the reference value VB is greater than the threshold value VC (|V3 - VB| > VC). In this case, the determination unit 11b determines in step S52 that the gripper 30 is not gripping the item MO (step S60). In this way, the control unit 11 determines the gripping state of the bag 40 by checking whether the value of the voltage V output from the hardened bag 40 and the reference value VB exceed the predetermined threshold value VC.

[0055] Thereafter, the control unit 11 controls the operation of each unit of the gripping device 10 in response to the occurrence of the trouble (step S62). Specifically, the control unit 11 controls the notification unit 15 to issue an alert indicating the occurrence of the trouble. The control unit 11 also controls the drive units to stop the movement of the gripper 30 toward another table.

[0056] During the movement of the item MO by the gripping device 10 in step S50, if some kind of trouble causes the bag body 40 gripping the item MO to collide with another component, the bag body 40 outputs a voltage V4. At this time, the voltage V4 output from the bag body 40 is a different value from the voltage V1 output when the bag body 40 is in a gripping state in which it is in contact with only the item MO. At this time, the difference between the value of the voltage V4 output from the bag body 40 and the reference value VB is greater than the threshold value VC (|V4-VB|>VC). At this time, the determination unit 11b determines in step S52 that a problem has occurred with the gripper 30 in the gripping state. Thereafter, the control unit 11 controls the operation of each component of the gripping device 10 in response to the occurrence of the problem, as in step S62.

[0057] (Operations and Effects) Next, operations and effects of the gripping device 10 will be described.

[0058] The bag body 40 of the gripping device 10 has a pressure-sensing unit 50, which allows it to elastically deform to fit the outer shape of the object MO and to sense contact pressure associated with contact with the object MO and output a voltage to the detection unit 14. Unlike mechanical devices such as push buttons, the pressure-sensing unit 50 does not hinder the elastic deformation of the main body 42. Therefore, the gripping device 10, which grips the object MO using jamming transition, can determine the gripping state of the object MO with a simple configuration.

[0059] The method of determining the gripping state by the control unit 11 determines the gripping state of the bag body 40 by checking whether the value of the voltage V output from the bag body 40 in a hardened state and the value of the reference value VB exceed a predetermined threshold value VC. Therefore, according to the method of determining the gripping state by the gripping device 10, it is possible to determine the gripping state of the item MO by the bag body 40 that utilizes jamming transition, based on the voltage V output from the bag body 40.

[0060] One method for determining the gripping state of the object MO by the gripper 30 is to detect a change in the weight of the gripper 30 as the gripper 30 grips the object MO using a load cell provided on the base 32 or the support member 13. When the posture of the gripper 30 gripping the object MO changes three-dimensionally, the relative load direction of the weight of the object MO on the gripper 30 and the support member 13 changes depending on the posture of the gripper 30. Therefore, when using a load cell to determine the gripping state of the gripper 30 in an operation in which the posture of the gripper 30 gripping the object MO changes three-dimensionally, it is necessary to provide multiple load cells on the gripper 30 or the support member 13. On the other hand, the gripping state determination method of the embodiment determines the gripping state of the object MO by the gripper 30 based on the voltage V output from the pressure-sensing unit 50 of the bag body 40. Therefore, in a determination system using the determination method of the embodiment, it is not necessary to arrange multiple pressure-sensing units 50 to correspond to three-dimensional changes in the posture of the gripper 30. Furthermore, one method for determining the gripping state of the item MO by the gripper 30 is to optically or visually determine the state of the gripper 30 using optical equipment such as a camera or an optical sensor. However, the configuration of a determination system using a method for determining the state of the gripper 30 using optical equipment becomes complicated. On the other hand, the gripping state determination method of the embodiment determines the gripping state of the item MO by the gripper 30 based on the voltage V output from the bag body 40. Therefore, the configuration of a determination system using the determination method of the embodiment is simple. Therefore, according to the determination system using the gripping state determination method of the embodiment, the configuration of the system for determining the gripping state of the item MO by the gripper 30 can be simplified.

[0061] As described above, an embodiment of the present invention has been described as an example, but the present invention is not limited to the above embodiment, and various modifications, changes, and improvements are possible within the scope of the technical concept of the present invention.

[0062] The piezoelectric film 52 and the pressure sensor 53 are arranged along the outer surface of the main body 42. However, the piezoelectric film 52 and the pressure sensor 53 according to the present disclosure may be provided inside the film of the film-shaped main body 42. In this case, the main body 42 may be formed integrally with the piezoelectric film 52 or the pressure sensor 53, using the piezoelectric film 52 or the pressure sensor 53 as a base material.

[0063] REFERENCE SIGNS LIST 10 Grip device 11 Control unit 11a Memory unit 11b Determination unit 12 Drive unit 13 Support member 14 Detection unit 20 Fluid control unit (an example of a pressure adjustment unit) 30 Gripper 40 Bag body 42 Main body unit 50 Pressure-sensing unit 52 Piezoelectric film 53 Pressure-sensing sensor CM Mixture CP Granules CA Fluid MO Article

Claims

1. A gripping device capable of gripping an object, comprising: a drive unit; a support member operable by said drive unit; a detection unit that detects voltage; a bag body provided on said support member, formed from an elastomer, and elastically deformable to match the outer shape of said object, said bag body being capable of sensing contact pressure associated with contact with said object and outputting a voltage to said detection unit; a mixture of particles and a fluid contained in said bag body; and a pressure adjustment unit that adjusts the pressure of said fluid contained in said bag body while maintaining the shape of said bag body.

2. A gripping device as described in claim 1, further comprising a control unit, a memory unit, and a judgment unit, wherein the control unit controls the drive unit to bring the bag body into contact with the item, thereby elastically deforming the bag body in a tight fit to the outer shape of the item and outputting a voltage from the bag body, the control unit controls the pressure adjustment unit to reduce the pressure of the mixture while maintaining the tight fit of the bag body, causing a jamming transition, thereby transitioning the bag body from a softened state to a hardened state and gripping the item, the memory unit stores the value of the voltage output from the bag body when the bag body transitions from the softened state to the hardened state as a reference value, and the judgment unit judges the gripping state of the bag body by checking whether the difference between the value of the voltage output from the bag body in a hardened state and the reference value exceeds a predetermined threshold.

3. The gripping device according to claim 1 or 2, wherein the bag body is made of piezoelectric rubber.

4. The gripping device according to claim 1 or 2, wherein the bag body has a main body portion formed from an elastomer and a piezoelectric film disposed on the outer surface of the main body portion.

5. A gripping device as described in claim 1 or 2, wherein the bag body has: a main body portion formed from an elastomer; and a pressure sensor arranged along the outer surface of the main body portion, the pressure sensor being a band-shaped pressure sensor that is elastically deformable to conform to the surface shape of the main body portion.

6. A method for determining a gripping state, comprising: bringing a bag containing a mixture of granules and fluid into contact with the item, elastically deforming the bag in a tight fit to match the outer shape of the item and outputting a voltage from the bag; reducing the pressure on the mixture while maintaining the tight fit of the bag, causing a jamming transition, thereby transitioning the bag from a softened state to a hardened state and gripping the item; storing the value of the voltage output from the bag when the bag transitions from the softened state to the hardened state as a reference value; and determining the gripping state of the bag by checking whether the difference between the value of the voltage output from the bag in the hardened state and the reference value exceeds a predetermined threshold.

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