Capacitance type sensor and robot system

Abstract

To provide a capacitance type sensor capable of correcting object detection in response to changes in an air state and simplifying a configuration related to the correction.SOLUTION: A sensor 6 as a capacitance type sensor includes: a detection sensor 11 having a detection electrode 25 and outputting a sensor value according to an electrostatic capacitance generated between the detection electrode 25 and an object such as a person H; a reference electrode 12 provided facing the detection electrode 25 and connected to a reference potential via a switch 30b; and a processing device 13 controlling the opening and closing of the switch 30b to switch between a first state in which the reference electrode 12 is open and a second state in which the reference electrode 12 is connected to the reference potential.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a capacitive sensor and a robot system. [Background technology]

[0002] There are cases where humans and robots work together to perform tasks on a workpiece. Robots used in such cases are called collaborative robots. Collaborative robots share the same work environment with humans, so safety for humans is required. For this reason, collaborative robots are sometimes equipped with capacitance sensors that can detect nearby objects.

[0003] Capacitive sensors can experience drift due to changes in ambient temperature and humidity. This can lead to a decrease in detection accuracy. The effect of drift is particularly pronounced when the detectable distance of a capacitive sensor is set long.

[0004] For example, Patent Document 1 describes a capacitance sensor that uses a detection electrode and a reference electrode, and compensates for fluctuations in the signal of the detection electrode due to changes in air conditions such as temperature and humidity using the signal of the reference electrode. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-145413 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in Patent Document 1, it is necessary to prevent an object from being detected by the correction reference electrode, which may require a surrounding environment in which a sufficient space is secured around the reference electrode and a shield or the like is installed.

[0007] In view of the above problems, the present invention aims to provide a capacitance sensor and a robot system that are capable of correcting object detection in response to changes in air conditions and that can simplify the configuration related to the correction. [Means for solving the problem]

[0008] In order to solve the above problem, the capacitance-type sensor of the present invention comprises a detection sensor having a detection electrode and outputting a sensor value corresponding to the capacitance generated between the detection electrode and an object, a reference electrode arranged opposite the detection electrode and connected to a reference potential via a switch, and a processing device that controls the opening and closing of the switch to switch between a first state in which the reference electrode is open and a second state in which the reference electrode is connected to the reference potential.

[0009] In addition, in the capacitance type sensor, the processing device corrects the sensor value in the first state using the sensor value in the second state.

[0010] In addition, in a capacitance-type sensor, the sensor value in the first state is a value corresponding to the capacitance formed between the detection electrode and an object via the open reference electrode, and the sensor value in the second state is a value corresponding to the capacitance formed between the detection electrode and the reference electrode connected to a reference potential.

[0011] The capacitance sensor also includes a detection sensor having a detection electrode and outputting a sensor value corresponding to the capacitance generated between the detection electrode and an object, a reference sensor provided at a different position from the detection electrode and having an electrode paired with the detection electrode via the surrounding air, and a processing device that calculates the dielectric constant corresponding to the surrounding air based on the reference sensor and corrects the sensor value using the dielectric constant.

[0012] In the capacitance type sensor, the detection electrode of the detection sensor and the reference sensor are provided on different members.

[0013] In addition, in the capacitance type sensor, a plurality of the detection sensors are provided, and one reference sensor is provided for each of the plurality of detection sensors, and the processing device corrects the sensor value of each of the detection sensors using the dielectric constant calculated by the reference sensor.

[0014] The robot system also includes a base, a plurality of arms attached to the base, and the above-described capacitance sensor, and the detection electrode and the reference electrode are attached to the arms.

[0015] The robot system also includes a base, a plurality of arms attached to the base, and the above-mentioned capacitance sensor, wherein the detection electrodes of the detection sensors are attached to the arms, and the reference sensor is attached to the base. [Effects of the Invention]

[0016] According to the capacitance type sensor and robot of the present invention, the present invention makes it possible to correct object detection in response to changes in air conditions, and also simplifies the configuration related to the correction. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram illustrating an example of the overall configuration of a robot system including a capacitance-type sensor according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing an example of a specific configuration of the capacitance type sensor of FIG. [Figure 3] 2 is a diagram showing a first state of the capacitance type sensor of FIG. 1. FIG. [Figure 4] 1. FIG. 4 is a diagram illustrating a second state of the capacitance type sensor of FIG. [Figure 5] 2 is a flowchart showing an example of a processing flow in the processing device of FIG. 1. [Figure 6]FIG. 10 is a diagram illustrating an example of the overall configuration of a robot system including a capacitance-type sensor according to a second embodiment. [Figure 7] FIG. 7 is a diagram showing an example of a specific configuration of the capacitance type sensor of FIG. 6. [Figure 8] 7 is a flowchart showing an example of a processing flow in the processing device of FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same components in the drawings will be denoted by the same reference numerals as much as possible, and duplicate descriptions will be omitted where appropriate.

[0019] ===First Embodiment=== First, the first embodiment will be described.

[0020] <Overall structure> FIG. 1 is a diagram schematically illustrating an example of the overall configuration of a robot system 2 equipped with a sensor 6 serving as a capacitance-type sensor according to a first embodiment of the present invention. The sensor 6 serving as a capacitance-type sensor includes a proximity sensor and a displacement sensor. That is, the sensor 6 may be a sensor that detects proximity or a sensor that detects displacement. In this embodiment, a case where the sensor 6 is a proximity sensor will be described as an example. In the sensor 6, a signal that changes depending on the distance to a nearby object is referred to as a "sensor value."

[0021] The robot system 2 is an industrial robot that performs processes such as machining and transporting a workpiece, and is also a collaborative robot that works in the same space as a person, for example.

[0022] As shown in FIG. 1, the robot system 2 mainly includes a robot 4, a control device 5, and a sensor 6.

[0023] The robot 4 is an articulated robot and has multiple arms and multiple joints. Specifically, the robot 4 includes a base 7, a first arm A1, a second arm A2, a third arm A3, and a fourth arm A4. The number of arms provided is not limited. The base 7 is the base of the robot 4 and is provided on an installation surface on which the robot 4 is placed. The base 7 is fixed to the floor and supports the entire robot 4. The first arm A1, the second arm A2, the third arm A3, and the fourth arm A4 constitute multiple arms provided on the base 7. The first arm A1 is connected to the base 7 via a rotation shaft. The first arm A1 rotates around the rotation shaft relative to the base 7 by a motor (not shown). The second arm A2 is connected to the first arm A1 via a rotation shaft and rotates around the rotation shaft by a motor (not shown). The third arm A3 is connected to the second arm A2 via a rotation shaft and rotates around the rotation shaft by a motor (not shown). The fourth arm A4 is connected to the third arm A3 via a rotation shaft and rotates around the rotation shaft by a motor (not shown). A tool 9 is attached to the tip of the fourth arm A4. By moving each joint, the robot 4 performs a predetermined operation and performs a predetermined process on a workpiece using the tool 9.

[0024] The control device 5 is an information processing device that controls the operation of the robot 4. The control device 5 is configured with, for example, a CPU, memory, a communication device, and a storage device, and performs various functions by executing predetermined programs. The control device 5 controls the operation of each arm of the robot 4 and the tool 9, causing the robot 4 to perform predetermined operations. For example, the control device 5 causes the robot 4 to perform predetermined operations such as gripping a workpiece with the tool 9 and transporting the workpiece from one position to another.

[0025] The control device 5 also stops the operation of the robot 4 using a sensor value output from the sensor 6, which will be described later. Specifically, if the sensor 6 is a proximity sensor, the control device 5 compares the sensor value with a threshold value to determine whether an object, such as a person, is approaching the robot 4. If the sensor value indicates that an object is approaching the robot 4, the control device 5 stops the operation of the robot 4. For example, if the sensor value increases in response to the approach of an object, the control device 5 determines that an object is approaching when the sensor value is equal to or greater than the threshold value. For example, if the sensor value decreases in response to the approach of an object, the control device 5 determines that an object is approaching when the sensor value is equal to or less than the threshold value. For example, if a collaborating person approaches the robot 4, the operation of the robot 4 is stopped even if the robot 4 is in the middle of a predetermined operation. Note that if the sensor 6 is a displacement sensor, the control device 5 acquires and processes the displacement detection result from the sensor 6.

[0026] The sensor 6 is a capacitance sensor that detects an object such as a person, etc. The sensor 6 mainly includes a detection sensor 11, a reference electrode 12, and a processing device 13.

[0027] The detection sensor 11 is a capacitance sensor that detects an object. The detection sensor 11 is provided on the robot 4. For example, the detection sensor 11 is provided on an arm of the robot 4. In this embodiment, a case where the detection sensor 11 is provided on the fourth arm A4 will be described as an example. The detection sensor 11 may be provided on another part of the robot 4 or on multiple arms, and the installation position is not limited.

[0028] In the above example, the detection sensor 11 is provided on the arm. However, as long as at least the detection electrode 25 of the detection sensor 11, which will be described later, is provided on the arm, other components of the detection sensor 11 may not be provided on the arm.

[0029] The detection sensor 11 has an area in a predetermined direction as a detection area, and detects an object approaching the detection sensor 11 in the detection area.

[0030] 2 is a diagram showing an example of a specific configuration of the sensor 6. The detection sensor 11 includes an arbitrary waveform generator 21, a resistor 22, a capacitor 23a, a capacitor 23b, a resistor 24, a detection electrode 25, an instrumentation amplifier 26, a lock-in amplifier 27, and an A / D converter 28. The resistor 22, the capacitor 23a, the capacitor 23b, the resistor 24, and the detection electrode 25 form an RC bridge circuit 29.

[0031] The arbitrary waveform generator 21 uses the ground potential (GND potential) as a reference potential and generates a sine wave voltage or square wave voltage of a predetermined frequency, which is input to the RC bridge circuit 29. One end of the resistor 22 is electrically connected to the arbitrary waveform generator 21, and the other end is electrically connected to a capacitor 23a. One end of the capacitor 23a is electrically connected to the resistor 22, and the other end is electrically connected to the reference potential of the arbitrary waveform generator 21. The capacitor 23b is electrically connected in parallel to the capacitor 23a via a switch 30a. The resistor 24 is electrically connected to the arbitrary waveform generator 21 at one end, and to the detection electrode 25 at the other end. The values ​​of the resistor 22, the capacitor 23a, the capacitor 23b, and the resistor 24 are set in advance. For example, the resistors 22 and 24 have the same resistance value.

[0032] The detection electrode 25 is electrically connected to the resistor 24. The detection electrode 25 has, for example, a flat plate shape. The detection electrode 25 generates an electric field. The region of the generated electric field becomes the detection area, and an object that enters the detection area is detected. Note that a shield electrode connected to a reference potential or an active shield electrode with the same potential as the detection electrode 25 may be provided on the opposite side of the detection area of ​​the detection electrode 25.

[0033] Specifically, the detection electrode 25 forms a capacitance with the object. Fig. 2 shows a person H as an example of the object. It is assumed that the potential of the person H is equal to the reference potential. The detection electrode 25 forms a capacitance with the person H, and forms part of an RC bridge circuit 29.

[0034] The instrumentation amplifier 26 has a negative input terminal electrically connected between the resistor 22 and the capacitor 23a, and a positive input terminal electrically connected between the resistor 24 and the detection electrode 25. The output terminal is electrically connected to the lock-in amplifier 27. The lock-in amplifier 27 uses the signal from the arbitrary waveform generator 21 as a reference signal for synchronous detection. The instrumentation amplifier 26 differentially amplifies the inputs to the negative and positive input terminals. The differentially amplified signal is then synchronously detected by the lock-in amplifier 27 and converted from an analog signal to a digital signal by the A / D converter 28. The digital signal is output as a sensor value to the processing device 13, which will be described later. In this way, the sensor value output from the detection sensor 11 corresponds to the capacitance generated depending on the state (distance) between the detection electrode 25 and the object. The sensor value is not limited to the output of the A / D converter 28, and may be, for example, the sensor value of the lock-in amplifier 27.

[0035] Note that the specific circuit configuration of the detection sensor 11 is not limited to that shown in FIG. 2, as long as a sensor value corresponding to the capacitance formed in the detection electrode 25 is output.

[0036] The reference electrode 12 is provided opposite the detection electrode 25. The reference electrode 12 is arranged at a predetermined distance from the detection electrode 25 in the direction of the detection area. Therefore, the reference electrode 12 is provided at approximately the same position as the detection electrode 25. The reference electrode 12 is provided on an arm, similar to the detection electrode 25. The reference electrode 12 has, for example, a flat plate shape.

[0037] The reference electrode 12 is connected to a reference potential via a switch 30b. The opening and closing of the switch 30b is controlled by a processing device 13, which will be described later. When the switch 30b is open, the reference electrode 12 is in an open state, and when the switch 30b is closed, the reference electrode 12 is in a state connected to the reference potential (grounded state). The state in which the reference electrode 12 is in an open state is referred to as a "first state," and the state in which the reference electrode 12 is connected to the reference potential is referred to as a "second state."

[0038] The reference electrode 12 can be switched between a first state and a second state. FIG. 3 is a diagram showing the first state, and FIG. 4 is a diagram showing the second state. As shown in FIG. 3, in the first state, the electric field generated by the detection electrode 25 passes through the reference electrode 12. Then, a capacitance corresponding to the distance is formed between the detection electrode 25 and person H. Note that the reference electrode 12 is in an open state because the switch 30b is in an open state. Therefore, the influence of the reference electrode 12 on the electric field generated by the detection electrode 25 is negligible. Therefore, in the first state, the sensor value output from the detection sensor 11 is a value corresponding to the capacitance formed between the detection electrode 25 and an object such as person H via the open reference electrode 12.

[0039] 4, in the second state, the reference electrode 12 is connected to the reference potential because the switch 30b is closed. Therefore, the electric field generated by the detection electrode 25 does not pass through the reference electrode 12, and a capacitance is formed between the detection electrode 25 and the reference electrode 12. Therefore, in the second state, the sensor value output from the detection sensor 11 is a value corresponding to the capacitance generated between the detection electrode 25 and the reference electrode 12 connected to the reference potential. Note that the reference electrode 12 preferably has a size (area) equal to or larger than that of the detection electrode 25. This makes it difficult for the electric field generated by the detection electrode 25 to leak from the reference electrode 12, thereby suppressing the influence of objects such as a person H.

[0040] In both the first and second states, capacitance is formed via air. Therefore, capacitance is formed in the first and second states under the same air conditions. In a parallel plate capacitor, the air condition affects the dielectric constant ε, changing the value of the capacitance. Specifically, the dielectric constant ε changes depending on the temperature and humidity (relative humidity and absolute humidity). In particular, the dielectric constant ε tends to be affected by absolute humidity. This change in the dielectric constant ε causes the drift of the sensor value. However, by using the second state, it is possible to obtain a sensor value with air conditions equivalent to the first state, while suppressing the influence of objects such as a person H. In other words, the sensor value in the second state indicates the drift component of the sensor value that depends on the air condition.

[0041] 2, the processing device 13 is an information processing device that controls the first state and the second state. The processing device 13 is configured to include, for example, a CPU, a memory, a communication device, and a storage device, and performs various functions by executing predetermined programs.

[0042] The processing device 13 includes a switching unit 35 and a correction unit 36. The switching unit 35 and the correction unit 36 ​​shown in FIG.

[0043] The switching unit 35 controls switching between a first state and a second state of the reference electrode 12. The switching unit 35 performs switching by controlling the opening and closing of the switch 30b. Specifically, the switching unit 35 sets the switch 30b to the first state by opening it. The switching unit 35 also sets the switch 30b to the second state by closing it.

[0044] The switching unit 35 also controls the opening and closing of the switch 30a in accordance with the switching control. Specifically, the switching unit 35 opens the switch 30a in the first state, and closes the switch 30a in the second state. That is, in the second state, the capacitors 23a and 23b are electrically connected in parallel to form a composite capacitance. This is because the capacitance value formed at the detection electrode 25 is larger in the second state than in the first state.

[0045] The switching unit 35 repeatedly switches between the first state and the second state, for example, at a predetermined control cycle. It is preferable that the period of the first state is set longer than the period of the second state. Note that the timing of switching by the switching unit 35 is not limited to the above. For example, the switching unit 35 may be set to the first state when the robot 4 is operating, and to the second state when the robot 4 is stopped.

[0046] The correction unit 36 ​​corrects the sensor value in the first state using the sensor value in the second state. The correction unit 36 ​​calculates the difference between the sensor value in the first state and the sensor value in the second state.

[0047] Specifically, the correction unit 36 ​​subtracts the sensor value in the second state from the sensor value in the first state. That is, the correction unit 36 ​​suppresses a drift component that changes depending on the air condition from the sensor value in the first state. For example, the correction unit 36 ​​suppresses the drift component by subtracting the most recently acquired sensor value in the second state from the sensor value in the first state. Note that the sensor value in the second state to be subtracted may be a single sensor value in the second state or an average value of multiple sensor values ​​in the second state.

[0048] By performing this correction, it is possible to obtain a sensor value in which the influence of air conditions such as temperature and humidity (drift components) is suppressed. Furthermore, since the sensor values ​​in the first and second states are output using the same circuit as shown in FIG. 2, it is also possible to suppress the influence of temperature drift that occurs in the circuit itself. Furthermore, since the detection electrode 25 is used in both the first and second states, it is also possible to suppress the influence of changes in the electrode condition. The electrode condition includes, for example, dirt and condensation on the electrode surface.

[0049] The correction unit 36 ​​corrects the sensor value in the first state and outputs it to the control device 5.

[0050] In the above example, correction is performed by calculating the difference between the sensor value in the first state and the sensor value in the second state. However, the correction method is not limited to the above, as long as the sensor value in the first state is corrected so that the drift component due to the air condition is suppressed by the sensor value in the second state. For example, the sensor value in the second state may be multiplied by a certain magnification and then subtracted from the sensor value in the first state.

[0051] <Processing flow> 5 is a flowchart showing an example of the flow of the correction process according to this embodiment. The processes in the following steps are executed, for example, when the operation of the robot 4 is started. Note that the order and content of the following steps can be changed as appropriate.

[0052] (Step SP10) The switching unit 35 closes the switch 30b to the second state, and the process then proceeds to step SP11.

[0053] (Step SP11) The correction unit 36 ​​acquires the sensor value in the second state, and the process then proceeds to step SP12.

[0054] (Step SP12) The switching unit 35 determines whether a predetermined period of time has elapsed since the switch 30b was closed. If the predetermined period of time has not elapsed, the process returns to step SP11 and is executed again. If the predetermined period of time has elapsed, the process proceeds to step SP13.

[0055] (Step SP13) The switching unit 35 opens the switch 30b, setting it to the first state, and the process then proceeds to step SP14.

[0056] (Step SP14) The correction unit 36 ​​acquires the sensor value in the first state, and the process then proceeds to step SP15.

[0057] (Step SP15) The correction unit 36 ​​corrects the sensor value in the first state using the sensor value in the second state and outputs the corrected value to the control device 5. Specifically, the correction unit 36 ​​subtracts the sensor value in the second state from the sensor value in the first state. For example, the correction unit 36 ​​subtracts the sensor value in the second state, which was acquired in step SP11 executed immediately before executing step SP15, from the sensor value in the first state.

[0058] (Step SP16) The switching unit 35 determines whether a predetermined period of time has elapsed since the switch 30b was opened. If the predetermined period of time has not elapsed, the process returns to step SP14 and is executed again. If the predetermined period of time has elapsed, the process returns to step SP10 and is executed again.

[0059] In this way, the sensor values ​​relating to object detection are corrected. The control device 5 receives the sensor values, determines the proximity state of an object, for example, and applies the determined value to the control of the robot 4.

[0060] <Action and effect> As described above, in this embodiment, the reference electrode 12 is provided opposite the detection electrode 25, and is switched between a first state in which the reference electrode 12 is open and a second state in which the reference electrode 12 is connected to a reference potential. This makes it possible to obtain a sensor value corresponding to the object and a sensor value indicating a drift component that changes depending on the air condition. This makes it possible to correct the sensor value according to the object. Furthermore, because the reference electrode 12 for performing the correction is provided opposite the detection electrode 25, there is no need to prepare an environment, such as installing a shield to prevent the object from being detected, and the configuration related to the correction is simplified. In other words, object detection can be corrected in response to changes in the air condition, and the configuration related to the correction can be simplified.

[0061] Furthermore, by correcting the sensor value in the first state using the sensor value in the second state, it is possible to perform correction so as to suppress drift components in the sensor value in the first state.

[0062] Furthermore, even if the reference electrode 12 is provided opposite the detection electrode 25, in the first state, a sensor value corresponding to an object near the detection electrode 25 can be obtained via the open reference electrode 12. In addition, in the second state, a sensor value indicating a drift component can be obtained.

[0063] Furthermore, by providing the detection electrode 25 on the arm of the robot 4, it becomes possible to detect an object relative to the arm.

[0064] === Second Embodiment === Next, a second embodiment will be described.

[0065] In the second embodiment, a case where the sensor value is corrected using a reference sensor 62 will be described. Note that a description of the same points as in the first embodiment will be omitted. Also, the second embodiment can be combined with the first embodiment.

[0066] <Overall structure> FIG. 6 is a diagram schematically illustrating an example of the overall configuration of a robot system 40 equipped with a sensor 60 serving as a capacitance sensor according to this embodiment. The capacitance sensor 60 includes a proximity sensor and a displacement sensor. That is, the sensor 6 may be a sensor that detects proximity or a sensor that detects displacement. In this embodiment, a case where the sensor 6 is a proximity sensor will be described as an example.

[0067] Like the robot system 2, the robot system 40 is an industrial robot, for example, a collaborative robot.

[0068] As shown in FIG. 6, the robot system 40 mainly includes a robot 4, a control device 5, and a sensor 60.

[0069] The sensor 60 is a capacitance sensor that detects an object such as a person relative to the robot 4. The sensor 60 mainly includes a detection sensor 61, a reference sensor 62, and a processing device 63.

[0070] Similar to the detection sensor 11, the detection sensor 61 is a capacitance sensor that detects an object in a detection area in a predetermined direction. The detection sensor 61 is provided on an arm (for example, the fourth arm A4) of the robot 4. The detection sensor 61 may be provided on another part of the robot 4 or on multiple arms. Similar to the detection sensor 11, the detection sensor 61 only needs to have at least a detection electrode 25 (described later) of the detection sensor 61 provided on the arm.

[0071] 7 is a diagram showing an example of a specific configuration of a sensor 60. Similar to the detection sensor 11, the detection sensor 61 includes an arbitrary waveform generator 21, a resistor 22, a capacitor 23a, a resistor 24, a detection electrode 25, an instrumentation amplifier 26, a lock-in amplifier 27, and an A / D converter 28. The detection electrode 25 forms part of an RC bridge circuit 29. Note that the specific circuit configuration of the detection sensor 61 is not limited to that shown in FIG. 7, as long as a sensor value corresponding to the capacitance formed in the detection electrode 25 is output.

[0072] The detection electrode 25 forms a capacitance between itself and an object such as a person H. The sensor value output from the detection sensor 61 corresponds to the value of the capacitance generated between the detection electrode 25 and the object. The sensor value is output to the processing device 63.

[0073] Returning to FIG. 6, the reference sensor 62 is provided at a different position from the detection sensor 61. Specifically, the detection sensor 61 (particularly the detection electrode 25) and the reference sensor 62 are provided on different members. In this embodiment, the detection sensor 61 is provided on the fourth arm A4, and the reference sensor 62 is provided on the base 7. For example, the detection sensor 61 is provided on a movable member, and the reference sensor 62 is provided on a fixed (non-movable) member. The installation position of the reference sensor 62 is not limited.

[0074] The reference sensor 62 is preferably provided at a position where it does not interfere with the detection sensor 61. That is, the reference sensor 62 is provided at a position spaced apart from the detection sensor 61 by a predetermined distance or more. Specifically, when the robot 4 performs a predetermined operation, the detection sensor 61 (particularly the detection electrode 25) and the reference sensor 62 may come close to each other. Even when the detection sensor 61 and the reference sensor 62 are closest to each other, the reference sensor 62 is provided at a distance of a predetermined distance or more from the detection sensor 61. In this way, even when the robot 4 performs an operation, the distance (e.g., linear distance) between the detection sensor 61 and the reference sensor 62 is maintained at a predetermined distance. The predetermined distance is set to a distance or more that allows the influence of an electric field generated by either the detection sensor 61 or the reference sensor 62 on the other sensor to fall within an acceptable range. Furthermore, by providing the detection sensor 61 and the reference sensor 62 at a distance of a predetermined distance or more, contact between the detection sensor 61 and the reference sensor 62 is suppressed. The detection sensor 61 and the reference sensor 62 may be provided at positions where they interfere with each other due to placement restrictions or the like.

[0075] As shown in FIG. 7, the reference sensor 62 includes a pair of electrodes 71 and a measuring unit 72.

[0076] Two electrodes 71 are provided to form a pair, forming a parallel plate capacitor 73. Air (the air around the robot 4) flows between the electrodes 71. It is more preferable that the air between the electrodes 71 be the same as (or close to) the air around the detection sensor 61. The electrode area S and inter-electrode distance d of the electrodes 71 are set in advance and are fixed values ​​(design values).

[0077] For example, the electrode 71 may be configured to have the same specifications (e.g., electrode area) as the detection electrode 25 of the detection sensor 61, or may be configured to be smaller than the detection electrode 25 of the detection sensor 61. For example, by making the electrode 71 of the reference sensor 62 smaller in electrode area than the detection electrode 25 of the detection sensor 61, the entire sensor 60 can be made compact.

[0078] The measurement unit 72 measures the capacitance Cs of the capacitor 73 formed by the electrodes 71. For example, the measurement unit 72 passes a known current Is through the electrodes 71 and measures the time Tc until the voltage between the electrodes 71 reaches a reference voltage Vc. The measurement unit 72 then calculates the charge Qc accumulated based on the current Is and the time Tc, and calculates the capacitance Cs by dividing the charge Qc by the reference voltage Vc. That is, the measurement unit 72 calculates the capacitance Cs using the relationship Cs = (Is × Tc) / Vc. Note that the calculation method is not limited to the above as long as the capacitance Cs of the electrodes 71 can be calculated. Information related to the calculated capacitance Cs is output to the processing device 63, which will be described later.

[0079] The processing device 63 is an information processing device that corrects the detection information of the detection sensor 61 using reference information of the reference sensor 62. The detection information is a sensor value, and the reference information is a dielectric constant ε. The processing device 63 is configured with, for example, a CPU, memory, a communication device, and a storage device, and performs various functions by executing predetermined programs.

[0080] The processing device 63 includes a calculation unit 75 and a correction unit 76. The calculation unit 75 and the correction unit 76 shown in FIG.

[0081] The calculation unit 75 calculates the dielectric constant ε from the capacitance Cs of the reference sensor 62. Specifically, the calculation unit 75 acquires the capacitance Cs calculated by the measurement unit 72. Then, the calculation unit 75 calculates the dielectric constant ε based on the capacitance Cs and preset specification information of the reference sensor 62. The specification information of the reference sensor 62 is the electrode area S and inter-electrode distance d of the electrodes 71. The calculation unit 75 calculates the dielectric constant ε by multiplying the ratio (d / S) of the inter-electrode distance d to the electrode area S by the capacitance Cs. That is, the calculation unit 75 calculates the dielectric constant ε by ε = Cs × (d / S). Note that the method of calculating the dielectric constant ε is not limited to the above.

[0082] The permittivity ε varies depending on air conditions such as temperature and humidity. Therefore, by calculating the permittivity ε based on the reference sensor 62, which has a known configuration, the permittivity ε corresponding to the air surrounding the robot 4 can be obtained. The calculation unit 75 outputs the calculated permittivity ε to the correction unit 76.

[0083] The correction unit 76 corrects the sensor value of the detection sensor 61 based on the permittivity ε calculated by the calculation unit 75. Specifically, the correction unit 76 corrects the sensor value according to the difference between the permittivity ε and the reference permittivity ε, where the permittivity ε corresponding to the reference air state is set as a reference permittivity ε. For example, the difference between the permittivity ε and the reference permittivity ε and the correction value for the sensor value are associated in advance as correction data in the form of table data or a relational expression. Then, the correction unit 76 adds or subtracts the correction value corresponding to the actual difference from the sensor value. Alternatively, a conversion formula for converting the sensor value into a corrected sensor value according to the difference between the permittivity ε and the reference permittivity ε may be set in advance, and the correction unit 76 may perform the correction using the conversion formula.

[0084] By performing such correction, it is possible to obtain a sensor value in which the influence of air conditions such as temperature and humidity is suppressed. The sensor value is output to the control device 5.

[0085] 6 shows the case where the detection sensor 61 is provided on the fourth arm A4, but the detection sensor 61 may be provided at multiple positions, such as the fourth arm A4 and the third arm A3. That is, one reference sensor 62 may be provided for multiple detection sensors 61. In this case, the processing device 63 corrects the sensor value of each detection sensor 61 using the dielectric constant ε calculated by the reference sensor 62. Furthermore, multiple reference sensors 62 may be provided for one detection sensor 61.

[0086] <Processing flow> 8 is a flowchart showing an example of the flow of the correction process according to this embodiment. The processes of the following steps are repeatedly executed, for example, at a predetermined control cycle. Note that the order and content of the following steps can be changed as appropriate.

[0087] (Step SP20) The measurement unit 72 measures the capacitance Cs of the reference sensor 62. Then, the process proceeds to step SP21.

[0088] (Step SP21) The calculation unit 75 calculates the permittivity ε corresponding to the air surrounding the robot 4 based on the capacitance Cs. Specifically, the calculation unit 75 calculates the permittivity ε by ε = Cs × (d / S) using the capacitance Cs and the electrode area S and inter-electrode distance d, which are known information. Then, the processing proceeds to step SP22.

[0089] (Step SP22) The correction unit 76 acquires the sensor value of the detection sensor 61. Then, the process proceeds to step SP23.

[0090] (Step SP23) The correction unit 76 determines whether the difference between the dielectric constant ε and the reference dielectric constant ε0 is equal to or less than the allowable value. If the difference between the dielectric constant ε and the reference dielectric constant ε0 is equal to or less than the allowable value, the process proceeds to step SP25. If the difference between the dielectric constant ε and the reference dielectric constant ε0 is not equal to or less than the allowable value, the process proceeds to step SP24.

[0091] (Step SP24) The correction unit 76 corrects the sensor value based on the dielectric constant ε, and the process then proceeds to step SP25.

[0092] (Step SP25) The correction unit 76 outputs the sensor value to the control device 5. If the difference between the dielectric constant ε and the reference dielectric constant ε0 is equal to or less than the allowable value, the uncorrected sensor value is output, and if the difference between the dielectric constant ε and the reference dielectric constant ε0 is not equal to or less than the allowable value, the corrected sensor value is output.

[0093] In this way, the sensor values ​​relating to object detection are corrected. The control device 5 receives the sensor values, determines the proximity state of an object, for example, and applies the determined value to the control of the robot 4.

[0094] <Action and effect> As described above, in this embodiment, the sensor 60, which is a capacitance-type sensor, corrects the sensor value of the detection sensor 61 using the reference sensor 62 having a pair of electrodes 71 connected via the ambient air. Therefore, although the sensor value may drift due to air characteristics, the sensor value can be corrected taking into account the air characteristics of the ambient air. Object detection can be performed based on the sensor value, thereby improving the accuracy of object detection. Furthermore, because the reference sensor 62 is a capacitor 73 formed by the pair of electrodes 71, environmental preparations such as installing a shield to prevent object detection are unnecessary, simplifying the correction configuration. In other words, object detection can be corrected in response to changes in air conditions, while simplifying the correction configuration. While temperature and humidity, which are air characteristics, can be directly measured, the measurement accuracy tends to be low. However, the above correction method allows for highly accurate correction of temperature and humidity without directly measuring them.

[0095] By providing the detection electrode 25 of the detection sensor 61 and the reference sensor 62 on different members (components), interference between the detection sensor 61 and the reference sensor 62 is suppressed.

[0096] Furthermore, it is possible to correct the sensor values ​​of multiple detection sensors 61 using one reference sensor 62. This eliminates the need to provide a reference sensor 62 corresponding to each detection sensor 61, making it possible to make the device more compact.

[0097] Furthermore, the detection sensor 61 is provided on the arm, and the reference sensor 62 is provided on the base 7. This prevents interference between the detection sensor 61 and the reference sensor 62. Furthermore, providing the reference sensor 62 on the arm may result in an area where an object cannot be detected, but this situation can be avoided.

[0098] === Variations === The present invention is not limited to the above-described embodiments. In other words, designs that are produced by those skilled in the art with appropriate design modifications to the above-described specific examples are also included within the scope of the present invention as long as they include the features of the present invention. Furthermore, the elements of the above-described embodiments and the following modifications can be combined to the extent technically possible, and such combinations are also included within the scope of the present invention as long as they include the features of the present invention.

[0099] For example, in the first and second embodiments, the case where the sensor 6 or the sensor 60 as a capacitance type sensor is provided on the robot 4 has been described as an example, but the capacitance type sensor may also be provided on a device other than the robot 4.

[0100] In the first and second embodiments, the cases where the functions are separated between the control device 5 and the processing device 13 or 63 have been described. However, some or all of the functions of the processing device 13 or 63 may be provided in the control device 5, or some of the functions of the control device 5 may be provided in the processing device 13 or 63. For example, the cases where the control device 5 has the function of determining whether or not an object is near the robot 4 based on sensor values ​​have been described, but this function may be provided in the processing device 13 or 63.

[0101] Furthermore, in the first and second embodiments, specific configuration examples of the detection sensor 11 and the detection sensor 61 have been described. However, the specific configuration of the detection sensor 11 and the detection sensor 61 is not limited as long as they have a detection electrode 25 and output a value corresponding to the capacitance between the detection electrode 25 and an object as a sensor value. For example, the detection sensor 11 and the detection sensor 61 may be configured in such a way that the transmission frequency changes depending on the capacitance generated between the detection electrode 25 and an object. Even in such a case, the sensor value can be corrected.

[0102] In the first embodiment, the correction unit 36 ​​subtracts the sensor value in the second state acquired in step SP11, which was executed immediately before executing step SP15, from the sensor value in the first state. However, the method for correcting the sensor value in the first state is not limited to the above. For example, the correction unit 36 ​​may subtract the average value of multiple sensor values ​​in the second state acquired within the predetermined period of step SP12 from the sensor value in the first state.

[0103] Furthermore, in the second embodiment, the case where the reference sensor 62 is provided on the base 7 of the robot 4 has been described as an example, but the installation position of the reference sensor 62 is not limited. For example, the reference sensor 62 may be provided in the surrounding space away from the robot 4. Furthermore, the number of reference sensors 62 to be installed is not limited. For example, a plurality of reference sensors 62 may be provided corresponding to a plurality of detection sensors 11.

[0104] Furthermore, in the second embodiment, the case where the permittivity ε is calculated using one reference sensor 62 and the sensor value is corrected has been described as an example, but the permittivity ε may be calculated based on a plurality of reference sensors 62. For example, a plurality of reference sensors 62 may be provided around the robot 4, and the permittivity ε may be calculated using the reference sensor 62 located closest to the robot 4, and the sensor value may be corrected. That is, the reference sensor 62 that calculates the permittivity ε may be selected in accordance with the movement of the robot 4. Also, a plurality of reference sensors 62 may be provided, and the sensor value may be corrected using the average value of the permittivity ε calculated from the plurality of reference sensors 62. That is, the correction is performed using a plurality of permittivity ε obtained from the plurality of reference sensors 62.

[0105] In the second embodiment, the case where the permittivity ε is calculated and the sensor value is corrected has been described as an example, but the timing of calculating the permittivity ε and the timing of the correction do not have to be the same. For example, when performing the correction, a previously calculated (most recently calculated) permittivity ε may be used. In the second embodiment, the output of the reference sensor 62 may be used as in the first embodiment, and correction may be performed based on the difference with the detection sensor 11, etc.

[0106] Furthermore, in the second embodiment, a case where the reference sensor 62 is fixed to a fixed portion such as a base has been described as an example, but a moving device may be provided that moves the position of the reference sensor 62. That is, the moving device may move the position of the reference sensor 62 in accordance with the movement of the robot 4 so as not to interfere with the detection sensor 11 mounted on the arm.

[0107] Furthermore, in the second embodiment, the processing device 63 may control the ON / OFF of the reference sensor 62. Specifically, the reference sensor 62 may be turned OFF in accordance with the movement of the robot 4. For example, when the detection sensor 11 approaches the reference sensor 62 in accordance with the movement of the robot 4, the operation of the reference sensor 62 is stopped. This prevents the electric field of the detection sensor 11 from affecting the reference sensor 62 and prevents the dielectric constant ε from being calculated including this effect.

[0108] Furthermore, in the first and second embodiments, the sensor 6 and the sensor 60 are described as being of a self-capacitance detection type as an example, but the sensor 6 and the sensor 60 may be of a mutual capacitance type. For example, in the first embodiment, the detection electrode 25 of the detection sensor 11 is configured with two electrodes (paired electrodes), and a reference electrode 12 is provided opposite the paired electrodes. For example, in the second embodiment, the detection electrode 25 of the detection sensor 61 is configured with two electrodes (paired electrodes). In either case, an object is detected by the mutual capacitance type using the paired electrodes provided as the detection electrode 25.

[0109] In the first and second embodiments, the processing device 13 and the processing device 63 are described as information processing devices using a CPU or the like, but at least a part (or all) of the functions may be configured using a logic circuit. In this way, the specific configuration of the processing device 13 and the processing device 63 is not limited. [Explanation of symbols]

[0110] 2, 40: Robot Systems 6, 60: Sensor (capacitive sensor) 7: Base 11, 61: Detection sensor 12:Reference electrode 13, 63: Processing equipment 25: Detection electrode 30b: Switch 62: Reference sensor A1: First arm (arm) A2: Second arm (arm) A3: Third arm (arm) A4: 4th arm (arm) H: Person (object) ε: Dielectric constant

Claims

1. a detection sensor having a detection electrode and outputting a sensor value corresponding to a capacitance generated between the detection electrode and an object; a reference electrode provided opposite the detection electrode and connected to a reference potential via a switch; a processing device that controls the opening and closing of the switch to switch between a first state in which the reference electrode is open and a second state in which the reference electrode is connected to a reference potential; A capacitance type sensor comprising:

2. 2. The capacitance type sensor according to claim 1, wherein the processing device corrects the sensor value in the first state using the sensor value in the second state.

3. the sensor value in the first state is a value corresponding to a capacitance formed between the detection electrode and the object via the reference electrode that is open, 3. The capacitance-type sensor according to claim 1, wherein the sensor value in the second state is a value corresponding to a capacitance formed between the detection electrode and the reference electrode connected to a reference potential.

4. a detection sensor having a detection electrode and outputting a sensor value corresponding to a capacitance generated between the detection electrode and an object; a reference sensor provided at a position different from the detection electrode and having an electrode paired with the detection electrode via ambient air; a processing device that calculates a dielectric constant corresponding to the ambient air based on the reference sensor and corrects the sensor value by the dielectric constant; A capacitance type sensor comprising:

5. 5. The capacitance type sensor according to claim 4, wherein the detection electrode of the detection sensor and the reference sensor are provided on different members.

6. A plurality of the detection sensors are provided, one reference sensor is provided for each of the plurality of detection sensors, 6. The capacitance type sensor according to claim 4, wherein the processing device corrects the sensor value of each of the detection sensors using the dielectric constant calculated by the reference sensor.

7. The base and a plurality of arms provided on the base; The capacitance type sensor according to claim 1 or 2; Equipped with The robot system is characterized in that the detection electrode and the reference electrode are provided on the arm.

8. The base and a plurality of arms provided on the base; The capacitance type sensor according to claim 4 or 5, Equipped with the detection electrode of the detection sensor is provided on the arm, The robot system is characterized in that the reference sensor is provided on the base.

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