JP7668145B2 - Pressure Sensor System - Google Patents

Description

The present invention relates to a planar pressure sensor capable of detecting the one-dimensional distribution of force applied to a pressure-receiving surface. The present invention also relates to a pressure sensor system and a robot hand that have such a pressure sensor.

When a workpiece is grasped by a robot hand, a planar pressure sensor capable of acquiring distributed pressure information is used to detect the position and orientation of the workpiece on the grasping surface. For example, Patent Documents 1 and 2 describe a pressure sensor that can measure two-dimensional pressure distribution by sandwiching a pressure-sensitive conductive sheet between two sets of electrode rows arranged in a grid pattern. Patent Document 2 describes the use of this pressure sensor by attaching it to the grasping surface of the robot hand.

Depending on the work performed by the robot hand, it may not be necessary to detect the two-dimensional pressure distribution, and it may be sufficient to detect the one-dimensional pressure distribution on the pressure-receiving surface. For example, Patent Document 3 describes a work in which a robot hand is used to insert a connector attached to the tip of a wire into an insertion hole, in which a pair of gripping surfaces that hold the wire are made parallel to each other and slid along the length of the gripping surfaces, thereby changing the direction of rotation of the connector by rolling the wire. In such a rolling operation of a linear object, it is sufficient to detect the position of the linear object in the length direction of the gripping surfaces. The robot hand described in Patent Document 3 is provided with a pressure sensor on at least one of the gripping surfaces that can detect the pressure distribution along the length of the gripping surface, thereby obtaining the position of the wire on the gripping surface before and after rolling. Patent Document 3 describes, as an example of a pressure sensor, a conductive rubber sandwiched between two linear electrodes parallel to the length direction of the gripping surface and a group of linear electrodes that intersect with the two linear electrodes.

JP 2013-108754 A JP 2019-109213 A JP 2020-192666 A

The pressure sensor described in Patent Document 3, like the pressure sensors described in Patent Documents 1 and 2, has electrodes on both sides of a pressure-sensitive conductive sheet. However, when a robot hand holds the wire and performs a rolling operation, shear stress concentrates at the joint between the pressure-sensitive conductive sheet and the electrode, where different materials are joined. Therefore, when the pressure sensor is used repeatedly over a long period of time, the joint between the pressure-sensitive conductive sheet and the electrode can be damaged, causing the pressure-sensitive conductive sheet to sag, which can cause measurement errors.

The present invention has been made in consideration of the above, and aims to provide a planar pressure sensor capable of detecting pressure distribution in one dimension on the pressure-receiving surface, and capable of suppressing sagging of pressure-sensitive conductive sheets, etc.

The pressure sensor of the present invention is a pressure sensor capable of detecting the one-dimensional distribution of force applied to a pressure-receiving surface, and is characterized in that it has a pressure-sensitive conductive layer whose electrical resistance changes according to the applied pressure, and a plurality of electrodes arranged in parallel in the one-dimensional direction, the plurality of electrodes being provided only on one surface of the pressure-sensitive conductive layer.

Here, detecting the one-dimensional distribution of the force applied to the pressure-receiving surface includes not only determining the distribution of the absolute value of the force, but also determining the distribution of indices that correspond one-to-one to the force, such as the rate of change in resistance of the pressure-sensitive conductive layer, the dielectric constant, the piezoelectric voltage, and the piezoelectric resistance.

This configuration reduces the number of contact surfaces with the electrodes that can cause the pressure-sensitive conductive layer to sag.

Preferably, the pressure-sensitive conductive layer is made of a pressure-sensitive conductive rubber sheet. This allows the pressure sensor to be manufactured at low cost, even when manufacturing a wide variety of products in small quantities to suit different applications, since it is only necessary to cut the sheet material into the desired shape and size.

Preferably, the multiple electrodes are formed on a resin film substrate. This makes it easier to manufacture the pressure sensor.

The pressure sensor system of the present invention has any one of the pressure sensors described above and a control unit, and the multiple electrodes are connected to the control unit. The control unit selects a drive electrode to which a predetermined voltage is applied from the multiple electrodes, selects a ground electrode that is an electrode other than the drive electrode and is connected to ground, and measures the potential of the drive electrode relative to ground. Here, ground is a potential that serves as a reference for circuit operation.

Another pressure sensor system of the present invention has any of the pressure sensors described above and a control unit, and among the multiple electrodes, some of the electrodes are connected to the control unit and the other electrodes are connected to ground, and the control unit selects a drive electrode to which a predetermined voltage is applied from the electrodes connected to the control unit and measures the potential of the drive electrode relative to ground.

The robot hand of the present invention is a robot hand capable of holding an object between a pair of gripping surfaces, and at least one of the gripping surfaces is equipped with any one of the pressure sensors described above.

In the pressure sensor of the present invention, electrodes are provided on only one side of the pressure-sensitive conductive layer. This reduces the number of contact surfaces with the electrodes that can cause the pressure-sensitive conductive layer to sag, compared to conventional pressure sensors in which the pressure-sensitive conductive layer is sandwiched between two sets of electrodes, improving durability and quality stability.

FIG. 1 is a diagram showing a cross-sectional structure of a pressure sensor according to an embodiment. 1 is a diagram illustrating a configuration of a pressure sensor system according to a first embodiment. FIG. 2 is a side view illustrating a structure of a robot hand according to an embodiment. FIG. 4 is a process flow diagram when the pressure sensor system of the first embodiment is used. 1A and 1B are diagrams for explaining a method for measuring the potential of even-numbered electrodes of the pressure sensor relative to ground in the first embodiment, where A is measurement of the second electrode and B is measurement of the fourth electrode. 1A and 1B are diagrams for explaining a method for measuring the potential of odd-numbered electrodes of a pressure sensor relative to ground in the first embodiment, A: measurement of the third electrode, and B: measurement of the fifth electrode. 11 is a diagram for explaining a method for determining the maximum position of the force applied to the pressure-receiving surface from the measured resistance value. FIG. 13A to 13C are diagrams for explaining a method of measuring a potential of a third electrode of the pressure sensor relative to ground in the modified example of the first embodiment. FIG. 13 is a diagram illustrating a configuration of a pressure sensor system according to a second embodiment. FIG. 13 is a diagram illustrating a configuration of a pressure sensor system according to a third embodiment.

The first embodiment of the present invention will be described in the order of a pressure sensor, a pressure sensor system, and a robot hand, with reference to Figures 1 to 8.

Referring to FIG. 1, the pressure sensor 10 of this embodiment has a pressure-sensitive conductive layer made of a pressure-sensitive conductive rubber sheet 11, and a plurality of linear electrodes 14 arranged in parallel on the pressure-sensitive conductive rubber sheet. The electrodes 14 are provided only on one side of the pressure-sensitive conductive rubber sheet, and are electrically connected to the pressure-sensitive conductive rubber sheet via a joint surface 17. The surface of the pressure-sensitive conductive rubber sheet opposite the electrodes serves as a pressure-receiving surface 18.

The pressure-sensitive conductive rubber sheet 11 is made of insulating rubber such as silicone rubber to which conductive particles such as carbon have been added. When compressed, the conductive particles come into contact with each other, lowering the electrical resistance. By utilizing this property and measuring the change in electrical resistance at various points on the pressure-sensitive conductive rubber sheet, the applied pressure and its distribution can be calculated. Various commercially available pressure-sensitive conductive rubber sheets can be used.

The thickness of the pressure-sensitive conductive rubber sheet 11 is preferably 0.1 mm or more, and more preferably 0.3 mm or more. If the pressure-sensitive conductive rubber sheet is too thin, there is a high possibility that it will break during use. On the other hand, the thickness of the pressure-sensitive conductive rubber sheet is preferably 2 mm or less, and more preferably 1 mm or less. If the pressure-sensitive conductive rubber sheet is too thick, the ratio of resistance change to the amount of compression becomes small, and the sensitivity of the sensor becomes low.

By using a pressure-sensitive conductive rubber sheet as the pressure-sensitive conductive layer, pressure sensors 10 can be manufactured at low cost, even when manufacturing a wide variety of products in small quantities to suit different applications, because all that is required is to cut the sheet material into the desired shape and size according to the application.

The electrodes 14 are linear and arranged in parallel to each other in the width direction of the electrodes (left and right direction in FIG. 1). Each electrode is electrically connected to the pressure-sensitive conductive rubber sheet 11. The electrodes are preferably formed on a resin film substrate 13 and are integrated with the resin film substrate to form the electrode sheet 12. If an electrode sheet is used, the electrode sheet and the pressure-sensitive conductive rubber sheet can be laminated with the electrodes facing the pressure-sensitive conductive rubber sheet 11, making it easier to manufacture the pressure sensor 10.

A known method can be used to form the electrodes 14 on the resin film substrate 13. For example, the electrode pattern can be formed by printing a conductive paste on an insulating resin film such as polyimide by screen printing or the like, or the electrode pattern can be formed by etching the copper foil portion of a laminated film in which copper foil is attached to a resin film.

The pressure-sensitive conductive rubber sheet 11 and the electrode 14 are laminated via the joint surface 17. When using the electrode sheet 12, the electrode 14 may simply be placed over the pressure-sensitive conductive rubber sheet, but it is preferable to use an anisotropic conductive adhesive to attach them together. This makes it difficult for the pressure-sensitive conductive rubber sheet to sag when shear stress acts on the joint surface, making it easier to maintain the electrical connection between the pressure-sensitive conductive rubber sheet and the electrode.

Note that FIG. 1 is not drawn to scale. The resin film substrate 13 is typically 10 to 150 μm thick. The electrodes 14 are typically 10 to 150 μm thick. The width and pitch of the electrodes can be designed according to the required resolution, but in applications where a robot hand is used to grip wires such as electric wires, the electrode width is often set to about 0.05 to 3 mm and the pitch to about 0.1 to 6 mm.

Referring to FIG. 2, lead wires 16 are drawn from each electrode 14. The direction in which the lead wires are drawn is not particularly limited, but in FIG. 2, the lead wires are drawn alternately on both sides of the pressure sensor 10, with the odd-numbered electrodes 14A drawing lead wires 16A to the right side of the pressure sensor, and the even-numbered electrodes 14B drawing lead wires 16B to the left side of the pressure sensor. In the following, the odd-numbered electrodes 14A are referred to as "odd electrodes" and the even-numbered electrodes 14B as "even electrodes."

When forming the electrodes 14 on the resin film substrate 13, the electrodes 14 and the lead wires 16 can be formed simultaneously on one resin film substrate 13. In this case, it is preferable to cover the area where the lead wire 16 pattern is formed with an insulating coat.

The pressure sensor system 20 of this embodiment has a pressure sensor 10 and a control unit 21. The control unit 21 has a control unit main body 22 and an electrode selection circuit 23. The electrode selection circuit 23 is composed of a first selection unit 24 and a second selection unit 26.

The odd-numbered electrodes 14A are connected to the first selection unit 24 via lead wires 16A. In response to an instruction from the control unit body 22, the first selection unit selects one of the odd-numbered electrodes and applies a predetermined voltage V _D , for example, 5V, to it via a fixed resistor R _D to make it a drive electrode, or selects one or all of the odd-numbered electrodes collectively and connects them to ground to make them a ground electrode. In this specification, an electrode to which a predetermined voltage is applied is referred to as a drive electrode, and an electrode connected to ground is referred to as a ground electrode. The first selection unit can be configured by appropriately combining commercially available parts such as a selector that selects one output from multiple inputs and an analog switch that switches connections.

The even-numbered electrodes 14B are connected to the second selection unit 26 via lead wire 16B. In response to an instruction from the control unit main body 22, the second selection unit selects one of the even-numbered electrodes and applies a predetermined voltage V _D , for example, 5 V, via a fixed resistor R _D to set it as a drive electrode, or selects one or all of the even-numbered electrodes collectively and connects them to ground to set them as ground electrodes. The second selection unit can be configured in the same way as the first selection unit 24.

The control unit main body 22 instructs the first selection unit 24 and the second selection unit 26 to select the drive electrodes and ground electrodes, and by scanning the drive electrodes and measuring the electrical characteristics corresponding to the force applied to the pressure-receiving surface 18, determines the distribution of the force applied to the pressure-receiving surface in the direction in which the electrodes are arranged. Specifically, the control unit main body measures the potential of the selected drive electrodes relative to ground. The control unit main body also performs various calculations. The control unit main body may be a microcomputer for controlling the connection of peripheral devices. The functions of the control unit 21 will be described in detail later.

Referring to FIG. 3, the robot hand 30 of this embodiment has a base 31, a first finger portion 32, and a second finger portion 34. The robot hand 30 is often used with the base portion 31 attached to the tip of the arm of an articulated robot. The first finger portion has a first gripping surface 33 on the surface facing the second finger portion, and the second finger portion has a second gripping surface 35 on the surface facing the first finger portion. By narrowing the gap between the first finger portion and the second finger portion, the workpiece can be clamped between the first gripping surface and the second gripping surface.

The first gripping surface 33 is equipped with a pressure sensor 10. The pressure sensor is fixed to the first gripping surface by gluing, taping, mounting with a holding jig, or the like so that the pressure receiving surface 18 faces the second gripping surface side, i.e., the side that contacts the workpiece, and the linear electrodes are aligned in the length direction of the first gripping surface (left and right direction in FIG. 3). Although not shown in FIG. 3, lead wires 16 are drawn from the pressure sensor to both sides of the first finger portion 32 (front and back in FIG. 3), and the lead wires extend along the side or bottom surface of the first finger portion toward the base portion 31 and are connected to the control unit 21. The pressure sensor 10 may be provided on both the first gripping surface 33 and the second gripping surface 35.

Next, we will explain how to use the pressure sensor 10, pressure sensor system 20, and robot hand 30 of this embodiment.

First, the robot hand 30 grasps the workpiece. The workpiece is, for example, a linear object. Examples of linear objects include metal wires, electric wires, glass fibers, optical fibers, dried noodles, plant roots and stems, and synthetic resin fibers and tubes. Next, the distribution of force applied to the pressure receiving surface 18 of the pressure sensor 10 is detected according to the flow in FIG. 4.

(S1) First, the even electrodes 14B are used as the driving electrodes and measurements are taken by sequentially scanning them.

2 and 5, the control unit 22 transmits a control signal S to the first selection unit 24, which selects the first odd-numbered electrode E1 and connects it to the ground, and connects it to the control unit as a ground electrode. The control unit transmits a control signal S to the second selection unit 26, which selects the first even-numbered electrode E2, applies a predetermined voltage _VD to it via a fixed resistor R _D , and connects it to the control unit as a drive electrode. The pressure sensor 10 is in the state shown in FIG. 5A. The odd-numbered electrode E1 is a ground electrode, and the even-numbered electrode E2 is a drive electrode. The control unit measures the potential difference between the electrodes E2 and E1 to measure the potential of the electrode E2 with respect to the electrode E1, that is, the potential of the electrode E2 with respect to ground. The potential of the electrode E2 (the potential at point Y in FIG. 2) varies in the range of 0 to _VD depending on the resistance R12 of the pressure-sensitive conductive rubber sheet between the electrodes E2 and E1, so that the resistance R12 in the pressure-sensitive conductive rubber sheet, which corresponds to the resistance with respect to ground, can be obtained from the potential of the electrode E2 with respect to ground.

Next, the control unit 22 sends a control signal S to the first selection unit 24, which selects the next odd-numbered electrode E3, connects it to ground, and connects it to the control unit as a ground electrode. The control unit 22 sends a control signal S to the second selection unit 26, which selects the next even-numbered electrode E4, applies a predetermined voltage _VD via a fixed resistor R _D , and connects it to the control unit as a drive electrode. The pressure sensor 10 is in the state shown in FIG. 5B. The odd-numbered electrode E3 is a ground electrode, and the even-numbered electrode E4 is a drive electrode. The control unit measures the potential of electrode E4 relative to ground in the same manner as above, and this potential corresponds to resistor R34 in the pressure-sensitive conductive rubber sheet.

Similarly, the first selection unit 24 sequentially selects the odd electrodes 14A as the ground electrodes, the second selection unit 26 sequentially selects the even electrodes 14B as the drive electrodes, and the control unit main body 22 measures the potential of the drive electrodes relative to ground.

(S2) In the next step, odd electrodes 14A are used as driving electrodes and measurements are taken by sequentially scanning.

2 and 6, the control unit 22 transmits a control signal S to the second selection unit 26, which selects the even-numbered electrode E2 and connects it to the ground, and connects it to the control unit as a ground electrode. The control unit transmits a control signal S to the first selection unit 24, which selects the odd-numbered electrode E3 and applies a predetermined voltage _VD to it via a fixed resistor R _D , and connects it to the control unit as a drive electrode. The pressure sensor 10 is in the state shown in FIG. 6A. The even-numbered electrode E2 is a ground electrode, and the odd-numbered electrode E3 is a drive electrode. The control unit measures the potential difference between the electrodes E3 and E2 to measure the potential of the electrode E3 relative to the electrode E2, i.e., the potential of the electrode E3 relative to the ground, and this potential corresponds to the resistor R23 in the pressure-sensitive conductive rubber sheet.

Next, the control unit 22 sends a control signal S to the second selection unit 26, which selects the next even-numbered electrode E4, connects it to ground, and connects it to the control unit as a ground electrode. The control unit 22 sends a control signal S to the first selection unit 24, which selects the next odd-numbered electrode E5, applies a predetermined voltage _VD via a fixed resistor R _D , and connects it to the control unit as a drive electrode. The pressure sensor 10 is in the state shown in FIG. 6B. The even-numbered electrode E4 is a ground electrode, and the odd-numbered electrode E5 is a drive electrode. The control unit measures the potential of electrode E5 relative to ground in the same manner as above, and this potential corresponds to resistor R45 in the pressure-sensitive conductive rubber sheet.

Similarly, the second selection unit 26 sequentially selects the even electrodes 14B as the ground electrodes, and the first selection unit 24 sequentially selects the odd electrodes 14A as the drive electrodes, and the control unit main body 22 measures the potential of the drive electrodes relative to ground.

By the above steps S1 and S2, the ground potential is obtained for all electrodes 14, and the resistance change of the pressure-sensitive conductive rubber sheet between adjacent electrodes can be obtained. In addition, since the compressive strain of the pressure-sensitive conductive rubber sheet 11 and the resistance change correspond one-to-one, the control unit main body 22 can convert the measured ground resistance into the force applied to the pressure-receiving surface 18 based on the characteristics of the pressure-sensitive conductive rubber sheet 11. This allows the one-dimensional distribution of the force applied to the pressure-receiving surface 18 in the direction in which the electrodes are aligned to be obtained. In addition, if the absolute value of the force applied to the pressure-receiving surface is not necessary, the control unit main body 22 may not perform the above conversion, and may only obtain the distribution of an index that corresponds one-to-one to the force applied to the pressure-receiving surface, such as the rate of change in the ground potential and ground resistance of each electrode. In the following, the distribution of the force applied to the pressure-receiving surface 18 and the distribution of the index that corresponds one-to-one to the force are collectively referred to as the "pressure distribution of the pressure-receiving surface".

(S3) Next, the peak position of the pressure distribution on the pressure-receiving surface 18 is found. In practical applications, there are cases where it is desired to know the position where the force applied to the pressure-receiving surface 18 is maximum. For example, in the wire rolling operation described in Patent Document 3, it is desired to find the position of the wire, so it is necessary to know the peak position of the pressure distribution on the pressure-receiving surface. Referring to Figure 7, the rate of decrease in the resistance to ground for each electrode is plotted, and the portion with the largest rate of decrease is interpolated using a quadratic curve or a parabola to find the peak position. In the example shown in Figure 7, it can be seen that the peak position is slightly closer to electrode 4 than electrode 5.

In addition, when the workpiece to be grasped by the robot hand 30 is thick, for example, and measurement values from all electrodes are not necessary, the peak position may be found by using only data from electrodes spaced at any interval, such as every other electrode or every two electrodes.

By repeating the above steps S1 to S3 at high speed, the position of the workpiece grasped by the robot hand 30 can be continuously monitored.

The pressure sensor 10 of this embodiment uses a structure in which electrodes are bonded to only one side of the pressure-sensitive conductive rubber sheet 11, making it possible to detect the distribution of the force applied to the pressure-receiving surface in the direction in which the electrodes are aligned. The inventors attached the above pressure sensor (electrode width 0.1 mm, electrode pitch 0.2 mm) to the gripping surface of a robot hand, gripped a metal rod with a diameter of 1 mm, and determined the gripping position of the metal rod using the above method. At the same time, the robot hand was photographed with a camera and the gripping position of the metal rod was determined from the image. Comparing the results of the two methods, the relative error of the gripping position of the metal rod had a standard deviation of 0.06 mm, and sufficient measurement accuracy was obtained with the pressure sensor 10 of this embodiment.

In addition, in the pressure sensor 10 of this embodiment, since there is only one joint surface between the pressure-sensitive conductive rubber sheet 11 and the electrode 14, sagging of the pressure-sensitive conductive rubber sheet is unlikely to occur even if the rolling operation by the robot hand is repeated. In a durability test in which the metal rod was grasped by a robot hand and the rolling operation was repeated, it was confirmed that the pressure sensor 10 of this embodiment is more durable than a conventional pressure sensor in which electrodes are provided on both sides of the pressure-sensitive conductive rubber sheet.

In addition, in the pressure sensor 10 of this embodiment, the ground potential of all electrodes can be measured by switching between the odd-numbered electrodes and the even-numbered electrodes that are set to ground potential. This makes it possible to obtain the pressure distribution on the pressure-receiving surface with the same resolution as the printing pitch of the electrodes, even if the electrodes are provided on only one side of the pressure-sensitive conductive rubber sheet. The pressure sensor system prototyped by the inventors above can measure 64 electrodes in 30 ms, and can essentially continuously monitor the gripping position of the wire while the wire is being rolled by the robot hand.

Below, we will explain some variations on how to use the pressure sensor system 20 of this embodiment.

In the above explanation, both the selected drive electrode and ground electrode were connected to the control unit main body 22, and the potential difference between the two was measured to measure the potential of the drive electrode relative to ground. However, only the selected drive electrode may be connected to the control unit main body, and the control unit main body may measure the potential of that drive electrode relative to ground. However, even in this case, the first selection unit 24 or the second selection unit 26 must select the ground electrode and form a circuit from the drive electrode through the pressure-sensitive conductive rubber sheet to ground.

In the above description, the first selection unit 24 and the second selection unit 26 sequentially select the ground electrodes one by one from the odd-numbered electrodes 14A or the even-numbered electrodes 14B, but the method of selecting the ground electrodes is not limited to this. Specifically, for example, when the first selection unit selects one driving electrode from the odd-numbered electrodes, the second selection unit may select all of the even-numbered electrodes collectively and connect them to ground, so that all of the even-numbered electrodes are used as ground electrodes. In this case, for example, when the electrode E3 is used as the driving electrode as in FIG. 6A, the pressure sensor 10 is in the state shown in FIG. 8. The resistance and potential to ground of the driving electrode to ground change depending on the path from the driving electrode to the ground, and in FIG. 8, the potential to ground of the electrode E3 to the electrode E3 corresponds to the resistance of the resistors R23, R34, R36, ... connected in parallel between the electrode E2, E4, E6, ... and the even-numbered electrodes E2, E4, E6, .... However, since the resistance value of the pressure-sensitive conductive rubber sheet 11 decreases rapidly at a certain compressive strain, the influence of the resistance value between the driving electrode E3 and the neighboring ground electrodes E6, E8, ... other than the ground electrodes E2 and E4 is small. Then, while the even electrodes are collectively set as ground electrodes, the first selection unit sequentially selects the driving electrodes from the odd electrodes, and the potential of the driving electrodes to ground can be measured. Note that when the odd electrodes are collectively selected as ground electrodes, the electrode located at the end, i.e., electrode E1, has a ground electrode only on one side, and the measurement conditions are different from when the other even electrodes are used as driving electrodes, so it may be excluded from the data when calculating the pressure distribution. The above is also true when the second selection unit selects one driving electrode from the even electrodes and the first selection unit selects ground electrodes from the odd electrodes collectively.

Furthermore, for example, the first selection unit 24 may select one drive electrode from the odd electrodes, and the second selection unit 26 may select all of the even electrodes as ground electrodes collectively, with the first selection unit 24 connecting the odd electrodes other than the selected drive electrode to ground. This is also the case when the second selection unit selects one drive electrode from the even electrodes, and the first selection unit selects ground electrodes collectively from the odd electrodes.

In the above explanation, step S1, in which a ground electrode is selected from the odd electrodes 14A and a drive electrode is selected from the even electrodes 14B and measured sequentially, and step S2, in which a ground electrode is selected from the even electrodes and a drive electrode is selected from the odd electrodes and measured sequentially, are alternately repeated. However, only one of steps S1 or S2 may be repeatedly performed. This reduces the resolution of the pressure distribution obtained, but the advantage of this is that the processing speed increases when the detection target is large compared to the spacing between the electrodes, for example, when the workpiece held by the robot hand is thick and a reduction in detection resolution is acceptable.

Next, a second embodiment of the pressure sensor system of the present invention will be described with reference to FIG. 9. This embodiment differs from the first embodiment in that the electrode selection circuit is made up of a single selection unit.

Referring to FIG. 9, the pressure sensor system 40 of this embodiment has a pressure sensor 10 and a control unit 41. The pressure sensor 10 is the same as that of the first embodiment. The control unit 41 has a control unit body 22 and an electrode selection circuit 43. The electrode selection circuit 43 consists of one selection unit 44.

All the electrodes 14 of the pressure sensor 10 are connected to the selection unit 44 via lead wires 16. The selection unit 44 selects one electrode in response to an instruction from the control unit main body 22, and applies a predetermined voltage V _D , for example, 5 V, to the electrode via a fixed resistor R _D to set the electrode as the drive electrode. At the same time, the selection unit 44 selects one electrode from among the electrodes other than the drive electrode and connects it to ground to set the electrode as the ground electrode.

The control unit main body 22 sends a control signal S to the selection unit 44, which selects one drive electrode and one ground electrode to connect to the control unit main body. The drive electrode and ground electrode are preferably adjacent electrodes. If the electrode next to the drive electrode is selected as the ground electrode, the pressure sensor 10 will be in the same state as in Figures 5 and 6. The control unit main body measures the potential difference between the drive electrode and the ground electrode to measure the potential of the drive electrode relative to ground.

Then, the measurement of the driving electrodes is repeated while sequentially changing the selected driving electrodes and ground electrodes. The driving electrodes may be selected in sequence for all electrodes 14, or in the case where the workpiece to be held by the robot hand 30 is thicker than the electrode spacing, every few electrodes may be selected in sequence. For example, every other driving electrode may be selected, or every third electrode, or a greater number of electrodes may be selected at intervals.

As with the first embodiment, various modifications are possible with respect to the method of using the pressure sensor system 40 of this embodiment. For example, only the drive electrode may be connected to the control unit main body 22, and the control unit main body may measure the potential of the drive electrode relative to ground. Also, for example, the selection unit 44 may collectively select electrodes other than the drive electrode as ground electrodes.

Next, a third embodiment of the pressure sensor system of the present invention will be described with reference to FIG. 10. This embodiment differs from the first embodiment in that either the odd-numbered electrodes or the even-numbered electrodes are collectively selected as drive electrodes, and the ground electrodes are sequentially selected from the other.

Referring to FIG. 10, the pressure sensor system 50 of this embodiment has a pressure sensor 10 and a control unit 51. The pressure sensor 10 is the same as that of the first embodiment. The control unit 51 has a control unit main body 22 and an electrode selection circuit 53. The electrode selection circuit 53 is made up of a first selection unit 54 and a second selection unit 56.

The odd-numbered electrodes 14A are connected to the first selection unit 54 via lead wire 16A. In response to an instruction from the control unit main body 22, the first selection unit 54 collectively selects the odd-numbered electrodes and applies a predetermined voltage _VD , for example, 5V, via a fixed resistor R _D to set the electrodes as drive electrodes, or selects one of the odd-numbered electrodes and connects it to ground to set it as a ground electrode.

The even-numbered electrodes 14B are connected to the second selection unit 56 via lead wire 16B. In response to an instruction from the control unit main body 22, the second selection unit 56 collectively selects the even-numbered electrodes and applies a predetermined voltage _VD , for example, 5V, via a fixed resistor R _D to set the electrodes as drive electrodes, or selects one of the even-numbered electrodes and connects it to ground to set it as a ground electrode.

The pressure sensor system 50 of this embodiment is used as follows:

A control signal S is sent from the control unit main body 22 to the first selection unit 54, which selects the odd-numbered electrodes collectively and applies a predetermined voltage _VD via a fixed resistor R _D to make them a drive electrode, and connects one of the drive electrodes to the control unit main body. A control signal S is sent from the control unit main body to the second selection unit 56, which selects the first even-numbered electrode and connects it to ground, which is then connected to the control unit main body as a ground electrode. The control unit main body measures the potential difference between the connected drive electrode and ground electrode, thereby measuring the potential of the drive electrode relative to ground.

A control signal S is sent from the control unit body 22 to the second selection unit 56, which selects the next even-numbered electrode and connects it to ground, and connects it to the control unit body as a ground electrode. At this time, the first selection unit 54 leaves all odd-numbered electrodes as drive electrodes. The drive electrodes that the first selection unit connects to the control unit body may or may not be changed, but if sequentially changing the drive electrodes connected to the control unit body simplifies the circuit configuration, it is preferable to change the drive electrodes connected to the control unit body. The control unit body measures the potential of the drive electrodes relative to ground by measuring the potential difference between the drive electrodes and the ground electrodes.

Similarly, the second selection unit 56 sequentially selects the even electrodes 14B as ground electrodes while the control unit body repeatedly measures the drive electrodes.

In the next step, the second selection unit 56 collectively selects the even electrodes 14B and applies a predetermined voltage _VD via a fixed resistor _RD to them as driving electrodes, and the first selection unit 54 sequentially selects the odd electrodes 14A as ground electrodes while the control unit body repeatedly measures the driving electrodes. This provides the potential of the driving electrodes relative to ground when all the electrodes 14 are set as ground electrodes one by one. By repeating the above steps at high speed, the position of the workpiece gripped by the robot hand 30 can be continuously monitored.

The method of using the pressure sensor system 50 of this embodiment can be modified in various ways, as in the first embodiment. For example, only the driving electrodes may be connected to the control unit main body 22, and the control unit main body may measure the potential of the driving electrodes relative to ground. In addition, for example, in the above description, the process of selecting the odd electrodes 14A as driving electrodes collectively and the even electrodes 14B as ground electrodes in sequence, and the process of selecting the even electrodes as driving electrodes collectively and the odd electrodes as ground electrodes in sequence are alternately repeated, but only one of the two processes may be repeated. This reduces the resolution of the pressure distribution obtained, but if the detection target is large compared to the spacing between the electrodes, for example, if the workpiece to be held by the robot hand is thick and the detection resolution can be reduced, the advantage of increased processing speed is obtained.

The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the technical concept.

For example, in the pressure sensor 10 of the above embodiment, a pressure-sensitive conductive rubber sheet 11 is used as the pressure-sensitive conductive layer, but the pressure-sensitive conductive layer may be formed by applying a pressure-sensitive conductive ink onto the parallel electrodes 14. In that case, however, a printing machine is required, and printing technology is required to obtain a smooth pressure-receiving surface. Therefore, in terms of cost when producing a wide variety of products in small quantities and ease of manufacturing the pressure sensor, it is better to use a pressure-sensitive conductive rubber sheet.

In addition, for example, in the above embodiment, an example was described in which the number of selectors connected to the multiple electrodes was one or two, but the number of selectors is not limited to this. By increasing the number of selectors, more resistance values can be detected with a single control signal sent from the control unit body to each selector, making it possible to detect the pressure distribution of the entire pressure sensor more quickly.

10 Pressure sensor 11 Pressure-sensitive conductive rubber sheet (pressure-sensitive conductive layer)
12 Electrode sheet 13 Resin film substrate 14 Electrode, 14A odd-numbered electrode, 14B even-numbered electrode 16 Lead wire, 16A odd-numbered lead wire, 16B even-numbered lead wire 17 Bonding surface 18 Pressure-receiving surface 20 Pressure sensor system 21 Control unit 22 Control unit main body 23 Electrode selection circuit 24 First selection unit 26 Second selection unit 30 Robot hand 31 Base unit 32 First finger portion 33 First gripping surface 34 Second finger portion 35 Second gripping surface 40 Pressure sensor system 41 Control unit 43 Electrode selection circuit 44 Selection unit 50 Pressure sensor system 51 Control unit 53 Electrode selection circuit 54 First selection unit 56 Second selection unit E1 to E6 Electrodes R12, R23, R34, R36, R45 Resistor R _D resistance S control signal V _D drive voltage

Claims (13)

A pressure sensor and a control unit are included.
The pressure sensor includes:
A pressure sensor capable of detecting a one-dimensional distribution of a force applied to a pressure receiving surface,
a pressure-sensitive conductive layer whose electrical resistance changes in response to applied pressure;
A plurality of electrodes arranged in parallel in the one-dimensional direction,
the plurality of electrodes are provided on only one surface of the pressure-sensitive conductive layer;
The plurality of electrodes are connected to the control unit,
The control unit is
selecting a drive electrode to which a predetermined voltage is applied from the plurality of electrodes;
selecting a ground electrode that is connected to ground and is an electrode other than the drive electrode;
measuring the potential of the driving electrode relative to ground;
Pressure sensor system. The control unit is
Sequentially selecting the drive electrodes to which a predetermined voltage is applied from the plurality of electrodes;
Selecting the ground electrodes, which are electrodes other than the drive electrodes and are connected to ground, either sequentially or all at once;
measuring the potential of the driving electrode relative to ground;
The pressure sensor system of claim 1 . the control unit measures a potential difference between the driving electrode and one of the ground electrodes to measure a potential of the driving electrode with respect to ground;
The pressure sensor system of claim 2 . the control unit has a first selection unit to which odd-numbered electrodes of the plurality of electrodes are connected and a second selection unit to which even-numbered electrodes are connected,
one of the first selection unit and the second selection unit sequentially selects the drive electrodes, and the other selects the ground electrodes sequentially or collectively;
The pressure sensor system according to claim 2 or 3 . The control unit alternately performs a step in which the first selection unit sequentially selects the drive electrodes and the second selection unit sequentially or collectively selects the ground electrodes, and a step in which the first selection unit sequentially or collectively selects the ground electrodes and the second selection unit sequentially selects the drive electrodes.
The pressure sensor system according to claim 4 . The control unit is
Sequentially selecting the ground electrode to be connected to ground from the plurality of electrodes;
selecting the drive electrodes, other than the ground electrodes, to which a predetermined voltage is applied, all at once;
measuring the potential of the driving electrode relative to ground;
The pressure sensor system of claim 1 . the control unit measures a potential difference between one of the driving electrodes and the ground electrode to measure a potential of the driving electrode with respect to ground;
The pressure sensor system of claim 6 . the control unit has a first selection unit to which odd-numbered electrodes of the plurality of electrodes are connected and a second selection unit to which even-numbered electrodes are connected,
one of the first selection unit and the second selection unit sequentially selects the ground electrodes, and the other selects the drive electrodes collectively;
The pressure sensor system according to claim 6 or 7 . the control unit alternately performs a step in which the first selection unit sequentially selects the ground electrodes and the second selection unit collectively selects the drive electrodes, and a step in which the first selection unit collectively selects the drive electrodes and the second selection unit sequentially selects the ground electrodes.
The pressure sensor system of claim 8 . A pressure sensor and a control unit are included.
The pressure sensor includes:
A pressure sensor capable of detecting a one-dimensional distribution of a force applied to a pressure receiving surface,
a pressure-sensitive conductive layer whose electrical resistance changes in response to applied pressure;
A plurality of electrodes arranged in parallel in the one-dimensional direction,
the plurality of electrodes are provided on only one surface of the pressure-sensitive conductive layer;
Among the plurality of electrodes, some of the electrodes are connected to the control unit, and the other electrodes are connected to ground;
The control unit is
selecting a drive electrode to which a predetermined voltage is to be applied from the electrodes connected to the control unit;
measuring the potential of the driving electrode relative to ground;
Pressure sensor system. The robot hand further includes a pair of gripping surfaces capable of gripping an object,
The robot hand includes the pressure sensor on at least one of the gripping surfaces.
The pressure sensor system according to any one of claims 1 to 10 . The pressure-sensitive conductive layer is made of a pressure-sensitive conductive rubber sheet.
The pressure sensor system according to any one of claims 1 to 11. The plurality of electrodes are formed on a resin film substrate.
A pressure sensor system according to any one of claims 1 to 12.

Images