WO2019012736A1 - Slippage detection system - Google Patents

Abstract

The present invention calculates approximately the minimum grip force necessary to prevent an object from slipping, and to do so with high accuracy and a simple configuration. This slippage detection system is provided with a plurality of projections, a deformation detection sensor 204, and a slippage detection means 112. The deformation detection sensor 204 is disposed in at least one of the plurality of projections. Slippage between the object and a projection 202 provided with the deformation detection sensor 204 occurs more easily as compared to a projection 201 that is not provided with the deformation detection sensor 204. The slippage detection means 112 uses a value from the deformation detection sensor 204 to calculate a first grip force for when slippage occurs between the object and the projection 202 with the deformation detection sensor 204 disposed thereon.

Description

Slip detection system

The present invention relates to a slip detection system.
This application claims the priority based on Japanese Patent Application No. 2017-135868 filed on Jul. 12, 2017 in Japan, the entire contents of the basic Japanese application are incorporated in the present application, and the contents of the present application. It is

A gripping mechanism (also referred to as a robot hand) is used by automated robots in production lines and inspection lines, and autonomous mobile robots to carry gripping objects. The grasping object of the grasping mechanism is various grasping objects which differ in hardness, weight, shape, size, etc. A sensing system for detecting the grasping object in order to grasp it without slipping or breaking it Is required.

In the conventional sensing system for detecting the slip of the grasped object, an example of an optical sensor that does not require the contact between the grasped object and the sensor that detects the contact between the grasped object and the grasping mechanism (gripping force, shear force) It can be mentioned.

For example, in Patent Document 1, a plurality of sensor units are arranged in a matrix, and the barycentric position of an object is calculated by a plurality of strain sensors incorporated in each sensor unit, whereby the appropriate force is obtained by Techniques for adjusting grip are presented. Further, in Patent Document 2, a plurality of contact sensors and an optical slip sensor module are disposed in the hand unit, and the position of the operation object is detected using the contact sensor, and the position of the operation object and the optical slip sensor Techniques have been presented to control slip detection points detected by the modules to coincide.

JP, 2008-281403, A JP 2012-228764 A

In order to properly grip various objects, it is necessary to detect a gripping force close to the minimum at which the objects do not slip and a tolerance for slipping. In the case of using a plurality of identical sensor units as in Patent Document 1, the slip can not be detected unless a large slip occurs such that the position of the center of gravity of the object changes, so the object does not slip. It is difficult to detect close gripping forces.

In the case of using an optical slip sensor together with a plurality of contact sensors as in Patent Document 2, the slip detection accuracy of the object depends on the performance of the image sensor, and therefore, when the slip detection is performed with high accuracy, A large element requires a high performance image sensor, resulting in high cost.

An object of the present invention is to calculate a gripping force close to the minimum at which an object does not slip with high accuracy and a simple configuration.

In order to solve the above-mentioned subject, the present invention has the following features, for example.

A deformation detection sensor comprising a plurality of projections, a deformation detection sensor, and a slip detection means, wherein the deformation detection sensor is disposed on at least one of the plurality of projections, and the deformation detection sensor is not disposed. When the protrusion on which the object is placed slips easily with the object, the slip detection means causes a slip between the object on which the deformation detection sensor is placed and the object depending on the value of the deformation detection sensor. Calculate one grip force.

According to the present invention, by detecting the slippage of a protrusion having a slippery structure among a plurality of protrusions, it is possible to calculate a gripping force close to the minimum with which the object does not slip with high accuracy and a simple structure. Problems, configurations, and effects other than those described above will be apparent from the description of the embodiments below.

It is a schematic diagram of the holding mechanism of 1st Embodiment. It is a schematic diagram of a sensor part. It is an expansion mimetic diagram of a slip detection projection of a sensor part. It is a schematic diagram of a sensor part which arranged a projection 5x5. It is a schematic diagram of the detection process of the gripping force near minimum. It is a sequence diagram of the detection process of the gripping force near minimum. It is a signal figure of the holding force (Fz) which the processus | protrusion for detection detected, and a Y direction shear force (Fy). It is a sequence diagram of detection and tolerance calculation process of gripping force near minimum. It is a schematic diagram of the robot leg of 2nd Embodiment. It is a schematic diagram of the slip detection process of the tire of 2nd Embodiment. It is a schematic diagram of the tire of 3rd Embodiment. It is a schematic diagram of the slip detection process of the tire of 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description shows specific examples of the content of the present invention, and the present invention is not limited to these descriptions, and various modifications by those skilled in the art can be made within the scope of the technical idea disclosed herein. Changes and modifications are possible. Further, in all the drawings for explaining the present invention, components having similar functions are denoted by the same reference numerals, and the same description may not be repeated.

A first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a view showing an example of the configuration of a gripping mechanism according to a first embodiment of the present invention.

As shown in FIG. 1, the gripping mechanism includes a hand 101 for performing gripping, and an arm 102 for causing the hand 101 to approach the object 104. The hand 101 includes a drive unit 105 that enables the opening and closing operation of the hand, a grip unit 100 that grips an object, and a sensor unit 103 that is disposed in the grip unit 100 and that detects slippage of the object. ing. The arm 102 is provided with an arm drive unit 106 which enables three-dimensional movement of the arm 102. The drive unit 105 and the arm drive unit 106 are controlled by the controller 108 via the amplifier 107. In the controller 108, a CPU 109, a memory 110, a slip detection means 112, and a margin calculation means 113 are mounted, and in the memory 110, a database 111 is provided.

FIG. 1 is a view schematically showing a gripping mechanism that grips the target object 104, and a slip detection system to which the present invention can be applied is not limited to such a gripping mechanism. In particular, the hand 101 may have a plurality of fingers like human hands, and the sensor unit 103 may be provided on each finger. In that case, if the small object 104 is gripped by the two fingers of the hand, the object 104 is grasped by the two fingers of the hand 101 if the object is large 104, etc. You may Furthermore, in the case of a large object 104, gripping may be performed using a plurality of gripping mechanisms. Further, it is not necessary to provide the sensor unit 103 on all the fingers, and the sensor unit 103 may be provided on the finger necessary to detect slippage. Conversely, the simplest configuration is the hand 101 as shown in FIG. 1, and the sensor unit 103 may be provided on at least one of the gripping surfaces.

FIG. 2 is a diagram showing the configuration of the sensor unit 103 according to the present embodiment. FIG. 2 is a diagram showing the sensor unit 103 such that the contact surface with the object 104 is on the top. The contact surface is a surface when the object and the sensor unit 103 contact, and more specifically, the holding projection 201 and the slip detection projection 202 installed in the sensor unit 103, and the object 104 It is the surface when it contacts. In the case of the hand 101, it is also referred to as a gripping surface.

The sensor unit 103 includes a fixed base 203 attached to the surface where the hand contacts the object, a plurality of protrusions 201 to 202 arranged in a matrix (in the vertical and horizontal directions) on the fixed base 203, and a plurality of protrusions 201 to A deformation detection sensor 204 that detects deformation of 202 is provided. The plurality of protrusions 201 to 202 form a contact surface with the object 104.

In the present invention, as shown in FIG. 2, at least one protrusion is different from the other protrusions and can slide faster than the other protrusions when being sheared. In addition, since a plurality of deformation detection sensors 204 are arranged, it has a structure capable of detecting the slip of the object. A slippery protrusion with the object 104 is referred to as a slip detection protrusion 202, and the other protrusion, that is, a protrusion less slippery than the slip detection protrusion 202 is referred to as a grip protrusion 201. In the present invention, the deformation detection sensor 204 needs to be disposed at least on the slip detection projection 202. However, by disposing the deformation detection sensor 204 also on the holding projection 201, the holding force and the shearing force can be calculated with higher accuracy.

In FIG. 2, each projection is shown as a substantially rectangular shape, but the present invention is not limited to this, as long as it is a member that protrudes from the fixed base and is deformed by receiving a gripping force or a shearing force Example: circular, triangular) is not limited. Further, although an example in which the projections are arranged in 3 × 3 is shown in FIG. 2, it is also possible to arrange fewer (at least 2 × 2) or more projections. The protrusions may be arranged by other arrangement such as concentric or spiral. It is desirable that each projection be disposed at a predetermined gap, and be configured not to be affected by the deformation of the other projections. The sensor unit 103 is not limited to being on a plane, and may be disposed on a curved surface. Further, the grip portion 100 may be used as the fixed base 203.

FIG. 3 is a view showing the configuration of the periphery of the slip detection protrusion 202 shown in FIG. The slip detection projection 202 receives a shear force along the grip surface from the object to be deformed, and the deformation detection sensor 204 receives the deformation to be strained, thereby detecting the shear force. In order to detect the deformation of each axis, in FIG. 3, four deformation detection sensors (two 204a and two 204b) are arranged horizontally on each side of the substantially rectangular projection. A sensor that detects a shear force in the Y direction is a deformation detection sensor 204a, and a sensor that detects a shear force in the X direction is a deformation detection sensor 204b. The gripping force (Z direction) can be calculated from all the sensors. The deformation detection sensors 204a and 204b are not limited to the arrangement of FIG. 3, and may be an arrangement capable of detecting a gripping force and a shearing force.

For example, strain gauges can be used as the deformation detection sensors 204a and 204b. However, various other configurations can be adopted. For example, it is possible to further miniaturize the slip detection projection 202 together with the sensor unit 103 by using silicon piezoresistor or the like instead of the strain gauge by the Micro-Electro Mechanical Systems (MEMS) technology.

FIG. 4 shows an example of the sensor unit 103 in which the protrusions are arranged in 5 × 5. When a plurality of slip detection projections 202 are provided as illustrated in FIG. 4, one slip detection projection 202 is generated because the surface of the target object 104 has unevenness when gripping the target object 104. Slip detection is possible from the average of the signals of the other slip detection projections 202 in contact with the object 104 without contact with them.

FIG. 5 shows an example of a process for slip detection. FIG. 6 is a flowchart of this process.

First, the position, shape, hardness, and weight of the object 104 are estimated by an optical sensor (not shown) to estimate an initial gripping force. Then, the arm 102 moves the hand 101 to the vicinity of the target object 104, and the hand 101 grips the target object 104 with the estimated gripping force (FIG. 5a, 601 to 603). Then, the arm 102 lifts the object 104 from the ground 507 by the movement of the Y axis (FIG. 5b, 604 to 605). After lifting the object 104, the gripping force of the hand 101 is gradually decreased (FIG. 5c, 606), and when the slip of the slip detection protrusion 202 is detected by the deformation detection sensor 204 (FIG. 5d, 607) Stop reducing power. The gripping force at this time is a gripping force immediately before the gripping projection 201 slips, and is a gripping force close to the minimum necessary for gripping the object 104. Thereby, the object can be gripped with a gripping force close to the minimum, and the gripped object can be gripped without slipping or breaking.

Then, by storing this information in the database 111, it is recorded as a gripping force that can handle the object 104 (608, 609). 606 to 609 are the processes of the slip detection means 112 shown in FIG.

FIG. 7 shows an example of the signal of the slip detection projection 202 when the process shown in FIGS. 5 and 6 is performed. During gripping, the force Fz in the Z direction gradually increases until the movement of the hand 101 is stopped after the slip detection projection 202 contacts the object 104. Thereafter, the force Fy in the Y direction increases until the object 104 is completely lifted. Thereafter, Fz gradually decreases as the distance between the hands gradually increases. As Fz gradually decreases, the frictional force between the slip detection projection 202 and the object 104 also gradually decreases, and when the frictional force becomes lower than the shear force, Fy decreases rapidly. The timing at which the Fy signal changes is when the slip detection projection 202 slips. Since the hand operation is stopped when a sharp drop in Fy is detected, the signals of Fz and Fy become constant thereafter. The Fz signal at this time corresponds to a gripping force close to the minimum for grasping the object 104.

By adding the deformation detection sensor 204 also to the gripping projection 201 around the slip detecting projection 202, the gripping force close to the minimum can be detected more accurately.

In order to make the slip detection protrusion 202 more slippery than the grip protrusion 201, the surface friction lower than the grip protrusion 201, that is, the slip detection protrusion 202 having a low coefficient of friction, or shear rigidity higher than the grip protrusion 201 It may be a slip detection projection 202 having

The following two methods may be mentioned in order to make the slip detection projection 202 having lower surface friction.

The first method is to change the surface finish (roughness) of the protrusions while using the same shape and material. A smooth surface (lower coefficient of friction) slip detection protrusion 202 can slide faster than the gripping protrusion 201 when subjected to the same amount of shear stress.

The second method is to use a material with a lower coefficient of friction for the slip detection protrusions 202. This method has the same effect as the first method, but since the coefficient of friction depends on the interaction between the projection and the object, it should be taken into account that the coefficient differs depending on the object to be handled . Therefore, the friction coefficient of the slip detection projection 202 may be smaller in one target object than in the grip projection 201, and may be larger in another target object. Examples of materials that can be used for producing the protrusion include silicone for the slip detection protrusion 202 and Teflon (registered trademark) for the gripping protrusion 201.

The following two methods may be mentioned in order to produce a gripping projection 201 having higher shear rigidity.

The first method is to make the length L of the entire protrusion from the fixed base the same, and to make the contact area A of the slip detection protrusion 202 with the object larger. Shear stiffness is
K = GA / cL
If the shear rigidity G of the entire projection (depending on the material), the shape factor c (depending on the shape) and the length L from the fixed base are the same, the contact area A of the projection for slip detection 202 is By increasing the size, the shear rigidity K of the slip detection projection 202 is increased. The shear force is
F = KΔY
In the case of handling an object, the slip detection projection 202 having higher shear rigidity is considered, considering that all the projections are deformed in the same manner (.DELTA.Y displacement of the coordinate axis Y shown in FIG. 5 is the same). Since the friction force is more quickly overcome than the gripping projection 201 by generating a larger shear force, it slides faster. Therefore, it is desirable that the slip detection projection 202 be shaped such that the contact area A with the object becomes large.

The second method is to use a more rigid material for the slip detection projection 202. Materials that are more rigid generate higher shear than other materials and slide faster than other materials when subjected to the same amount of shear stress. As mentioned above, different materials have different coefficients of friction, so they should be taken into consideration when selecting materials for both types of protrusions. Examples of materials that can be used for producing the protrusions include silicone with low polymerization agent for the slip detection projections 202 and silicone with high polymerization agent for the gripping projections 201.

When the rigidity of the slip detection projection 202 is changed so as to slide earlier than the other projections, the object is the hand by setting the ratio of the rigidity of the slip detection projection 202 and the grip projection 201. You can know your degree until you slip completely. As a result, it is possible to handle the target more appropriately and safely because it is possible to know how much the object slips from the hand when the grip amount of the hand is reduced by a percentage. For example, when the ratio of the rigidity k1 of the slip detection projection 202 to the rigidity k2 of the grip projection 201 is k1: k2 = 1: 0.8, the grip projection 201 slips when the slip detection projection 202 slips. The margin to reach is 20%. Therefore, even if the gripping force is reduced by 20%, the object does not slip.
FIG. 8 is a flowchart in the case where the ratio of the rigidity of the slip detection protrusion 202 and the grip protrusion 201 is set. In the flowchart, 801 to 808 are equal to 601 to 608 in FIG. 6, and 809 and 810 are processes of the tolerance calculation means 113. Hereinafter, a method of calculating the degree of freedom will be described.

First, as in FIG. 6, the slip of the slip detection projection 202 is detected, and the gripping force close to the minimum is detected. Then, using the data on the rigidity of each projection in the database 111, based on the gripping force close to the minimum calculated by the slip detecting means 112, until the object slips from the gripping projection 201, that is, the sliding of the contact surface Calculate the margin until occurrence (809 to 810). Furthermore, although not shown, a minimum gripping force which is a gripping force just before the occurrence of the slip of the contact surface is calculated based on the gripping force close to the minimum and the calculated latitude. Then, the calculated tolerance or minimum gripping force is stored in the database 111 of the controller 108 (811).

In addition, when the deformation detection sensor 204 is added to the grip projections 201 around the slip detection projection 202, that is, when the deformation detection sensor 204 is disposed with respect to the projections having different slipperiness, Based on the value of the arranged deformation detection sensor 204, the tolerance calculation means 113 calculates the tolerance to slip of the contact surface.

As described above, according to the slip detection system of the present invention, it is possible to obtain a gripping force close to the minimum that the object does not slip with high accuracy, simplicity and low cost. In addition, the minimum gripping force can be calculated and fed back to the gripping mechanism or to a device that requires slip detection.

The locations of the slip detection means 112 and the tolerance calculation means 113 are not limited to this, and the CPU 109 may play the roles of the slip detection means 112 and the tolerance calculation means 113.

A second embodiment of the present invention will be described with reference to FIGS.

The slip detection system of the present invention does not necessarily have to be used by the gripping mechanism and the robotic hand, but can be used with any device that requires slip detection. In this example, a method of using the slip detection system with the robot leg 901 of a walking robot (not shown) is shown.

The robot leg 901 detects slippage between the ground 507 and the robot leg rather than the object. If sliding can not be detected properly, the walking robot may lose its balance and fall. Since recent walking robots need to walk on various ground conditions, it is important to detect the slip of the robot legs 901.

In order to detect the slip of the robot leg 901, the sensor unit 103 is disposed at a portion of the robot leg 901 that is in contact with the ground as shown in FIG.

FIG. 10 shows the slip detection process in robot leg 901. After the walking robot starts to move one step, shear force detection is started between the robot leg 901 and the ground 507 (1001 to 1002). After that, shear force detection is performed until a sharp drop occurs in the shear force signal of the slip detection projection 202 (1002 to 1003), and if the shear force signal suddenly drops, the information is fed back to the control system of the walking robot (1003 to 1004). Then, the control system uses the information on the slip to take balance stabilization measures so as not to lose the balance of the traveling robot (1005). One example of a balance stabilization measure is a method of detecting the direction in which the slip detection projection 202 slips, and moving another robot leg 901 in the opposite direction.

In the present invention, not only the configuration of the robot leg 901 shown in FIG. 9 but also other robot legs can be used. Further, without being limited to the shape and size of the ground 507 shown in FIG. 9, any shape and size may be used as long as slippage can be detected by the method described in the first embodiment. However, the smaller the entire protrusion of the sensor unit 103, the smaller the measurement error regarding the shape of the robot. Therefore, the sensor unit 103 having a smaller protrusion is preferable.

As described above, when the slip detection system is used for the robot leg 901, it is possible to prevent the damage due to the walking robot falling by feeding back the slide information of the robot leg 901 to the control system.

A third embodiment of the present invention will be described with reference to FIGS. This example shows how to use a slip detection system on a tire.

When a tire of a vehicle slips, it loses control of the vehicle, which may lead to an accident that puts a person's life at risk. An antilock brake system (ABS) is used to prevent tire slippage. ABS detects that one wheel is rotating slower than the other wheels, interprets it as a lock on the wheel, and adjusts the braking force of that wheel multiple times per second to prevent slippage. is there. This rotation detection is performed by means of the wheel speed sensor and the threshold of the difference in the rotational speed of each wheel in order to avoid a malfunction of the system.

ABS is often used as a vehicle safety mechanism, but it relies on the actual occurrence of wheel slippage and experimentally defined thresholds. The system may malfunction because the system is not equipped with a sensor that actually detects tire slip. Therefore, the present invention is useful for tire slip detection.

By attaching the sensor unit 103 to the surface of the tire 1101 as shown in FIG. 11, the slip of the tire 1101 can be detected, and this information can be fed back to the vehicle brake control system. Then, the ABS can be used instead of the used threshold to prevent the malfunction of the ABS.

The slip detection process of the tire 1101 will be described with reference to FIG. After the movement of the vehicle is started, detection of the shear force of the tire 1101 is started (1201 to 1202). Thereafter, shear force detection is performed until the shear force signal of the slip detection projection 202 is sharply dropped (1202 to 1203), and if the shear force signal is sharply dropped, the information is fed back to the vehicle brake control system ( 1203-1204). The control system then uses the information on the slip to reduce the braking force of the tire 1101 that has been slip detected such that the tire 1101 is not locked (1205).

In this example, the slip detection system is used for a vehicle tire, but is not limited to the vehicle. Slip detection systems are used in all systems where it is necessary to prevent wheel slip. When the slip detection system is used in a device with less wear on wheels, such as a humanoid robot with wheels, wear on the protrusions is also reduced, so that the ability to detect slip can be maintained.

Reference Signs List 100 grip unit 101 hand 102 arm 103 sensor unit 104 object 105 drive unit 106 arm drive unit 107 amplifier 108 controller 109 CPU
110 memory 111 database 112 slip detection means 113 tolerance calculation means 201 grip projection 202 slip detection projection 203 fixed base 204 deformation detection sensor 204a Y direction deformation detection sensor 204b X direction deformation detection sensor 507 ground 601 to 609 Near grip force detection sequence 801 to 809 Sequence for detection and margin calculation of grip force close to minimum 901 Robot leg 1001 to 1004 Robot leg slip detection sequence 1101 Tire 1201 to 1205 Tire slip detection sequence

Claims (9)

A plurality of projections, a deformation detection sensor, and a slip detection means;
The deformation detection sensor is disposed on at least one of the plurality of protrusions.
The protrusion on which the deformation detection sensor is disposed is slippery between the object and the target in comparison with the protrusion on which the deformation detection sensor is not disposed.
The slip detection means is characterized by calculating a first gripping force when a slip occurs between the projection on which the deformation detection sensor is disposed and the object according to the value of the deformation detection sensor. Slip detection system. In the slip detection system according to claim 1,
Equipped with a margin calculation means,
The slip detection system, wherein the tolerance calculation means calculates a tolerance to occurrence of slip of the contact surface based on the first grip force. In the slip detection system according to claim 2,
The slip detection system according to claim 1, wherein the tolerance calculation means calculates a second gripping force based on the first gripping force and the tolerance. In the slip detection system according to claim 1,
A slip detection system characterized in that a protrusion in which the deformation detection sensor is disposed has higher shear rigidity than a protrusion in which the deformation detection sensor is not disposed. In the slip detection system according to claim 1,
A slip detection system characterized in that a protrusion on which the deformation detection sensor is disposed has a lower coefficient of friction than a protrusion on which the deformation detection sensor is not disposed. In the slip detection system according to claim 1,
Equipped with a margin calculation means,
The deformation detection sensor is provided for a first protrusion and a second protrusion having different slipperiness among the plurality of protrusions.
The slip detection system, wherein the tolerance calculation means calculates the tolerance to occurrence of slip of the contact surface based on the output of the deformation detection sensor with respect to the first protrusion and the second protrusion. . In the slip detection system according to claim 1,
A slip detection system characterized in that a silicon piezoresistor is used for the deformation detection sensor. In the slip detection system according to claim 1,
A slip detection system characterized in that a protrusion on which the deformation detection sensor is disposed has a shape in which a contact area with the object is larger than a protrusion on which the deformation detection sensor is not disposed. In the slip detection system according to claim 1,
The slip detection system, wherein the plurality of protrusions are arranged in a matrix.

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