Determination device

Abstract

A determination device (30) for determining the number (N) of magnetic bodies (W) attracted to a magnet gripper (10) comprises: a coil (30c); a decision unit (74) that, on the basis of a first voltage (V1), which is the value of the coil voltage (Vc) at a time point (Tbe) at which a prescribed time (Tb) has elapsed since the start of excitation of the coil, decides on a second voltage (V2) lower than the first voltage; and a determination unit (78) that determines whether the number of the magnetic bodies is one on the basis of the time required (Td) for the value of the coil voltage to reach the second voltage after the coil has been excited, degaussed, and then excited again.

Description

Determination device

[0001] The present disclosure relates to a determination device.

[0002] Japanese Patent Application Laid-Open No. 8-219707 discloses a two-piece adsorption detection device for a workpiece adsorbed and lifted by an electromagnetic chuck. The adsorption of one workpiece is determined using the output of a coil.

[0003] There is room for improvement in the determination accuracy regarding whether the number of magnetic bodies adsorbed by a magnet gripper is one or not.

[0004] An object of the present disclosure is to solve the above-described problems.

[0005] An aspect of the present disclosure is a determination device that determines the number of magnetic bodies adsorbed by a magnet gripper, including a coil, a voltage application circuit capable of applying a DC voltage and an alternating voltage to the coil using the power supply voltage of a DC power supply, a control unit that controls the voltage application circuit to apply the DC voltage to the coil to excite the coil and controls the voltage application circuit to apply the alternating voltage to the coil to demagnetize the coil, a detection circuit for detecting the coil voltage generated between both ends of the coil, a determination unit that determines a second voltage smaller than the first voltage based on the value of the first voltage, which is the value of the coil voltage at a time when a predetermined time has elapsed after the excitation of the coil is started by the application of the DC voltage to the coil, a timing unit that measures the required time from when the coil is re-excited after being excited and demagnetized by the control unit until the value of the coil voltage reaches the second voltage, and a determination unit that determines whether the number of the magnetic bodies is one or not based on the required time.

[0006] According to the present disclosure, it is possible to improve the determination accuracy regarding whether the number of magnetic bodies adsorbed by a magnet gripper is one or not.

[0007] Figure 1A shows the state where the number of magnetic objects attached to the magnetic gripper is 0. Figure 1B shows the state where the number of magnetic objects attached to the magnetic gripper is 1. Figure 1C shows the state where the number of magnetic objects attached to the magnetic gripper is 2. Figure 2 is an example of a determination device for determining the number of magnetic objects attached to the magnetic gripper. Figure 3 is an example of the temporal change in the voltage applied to the coil of the magnetic gripper, the temporal change in the current flowing through the coil, and the temporal change in the detected coil voltage. Figure 4A is an example of the change in coil voltage detected when the number of magnetic objects attached to the magnetic gripper is 0. Figure 4B is an example of the change in coil voltage detected when the number of magnetic objects attached to the magnetic gripper is 1. Figure 4C is an example of the change in coil voltage detected when the number of magnetic objects attached to the magnetic gripper is 2. Figure 5 shows an example of determining the number of magnetic objects attached to the magnetic gripper. Figure 6 is a flowchart illustrating the procedure for determining the number of magnetic objects attached to the magnetic gripper.

[0008] Robots sometimes supply workpieces to industrial equipment. For example, a robot might supply a steel plate to a press machine. If the supplied workpiece is a magnetic material such as a steel plate, a magnetic gripper may be used as the robot's end effector. A magnetic gripper has a magnet, such as a permanent magnet or an electromagnet. The magnetic force of the magnet in the magnetic gripper causes the magnetic material, which is the workpiece, to be attracted to the magnetic gripper.

[0009] Figure 1A shows the state where the number of magnetic materials W attracted to the magnetic gripper 10 is zero. The magnetic gripper 10 is attached to the robot 20. The magnetic gripper 10 has a magnet. The robot 20 brings the magnetic gripper 10 close to the top magnetic material W of a stack of multiple magnetic materials W. When one magnetic material W is attracted to the magnetic gripper 10 by the magnetic force of the magnet on the magnetic gripper 10, the robot 20 can supply the magnetic material W to industrial equipment.

[0010] In the example shown in Figure 1A, even though the magnetic gripper 10, which generates magnetic force, is brought close to the magnetic material W, the magnetic material W is not attracted to the magnetic gripper 10. In this case, the robot 20 cannot supply the magnetic material W to the industrial equipment. Therefore, the state in which the number of magnetic materials W attracted to the magnetic gripper 10 is zero is undesirable.

[0011] Figure 1B shows a state where one magnetic material W is attracted to the magnetic gripper 10. In the example shown in Figure 1B, as a result of bringing the magnetic gripper 10, which is generating magnetic force, closer to the magnetic material W, one magnetic material W is attracted to the magnetic gripper 10. In this case, the robot 20 can supply the magnetic material W to industrial equipment.

[0012] Here, we will explain the problems that may occur in the example where the industrial equipment is the press machine described above. When steel plates are pressed by a press machine, the steel plates are pressed one at a time. If, for example, two steel plates are supplied to the press machine's die at once by the robot 20, the press processing will be attempted on both steel plates. This can lead to problems such as defective press processing or die failure.

[0013] Therefore, in such cases, the steel plates must be supplied one at a time. That is, if the magnetic material W is processed one at a time by the industrial equipment, the robot 20 must supply one magnetic material W to the industrial equipment at a time, and the robot 20 cannot supply two or more magnetic materials W to the industrial equipment at one time.

[0014] Figure 1C shows a state in which two magnetic materials W are attracted to the magnetic gripper 10. In the example shown in Figure 1C, two magnetic materials W are attracted to the magnetic gripper 10 as a result of the magnetic gripper 10, which is generating a magnetic force, being brought close to the magnetic materials W. As described above, if the magnetic materials W are processed one by one by industrial equipment, the robot 20 cannot supply two magnetic materials W to the industrial equipment at once. Therefore, the state in which two magnetic materials W are attracted to the magnetic gripper 10 is undesirable. Similarly, the state in which three or more magnetic materials W are attracted to the magnetic gripper 10 is also undesirable.

[0015] As explained using Figures 1A, 1B, and 1C, it is expected that one magnetic material W will be attracted to the magnetic gripper 10. Therefore, it is desirable that the robot 20 determine whether one magnetic material W is attracted to the magnetic gripper 10 after the magnetic material W attraction operation and before moving on to the magnetic material W supply operation or before the magnetic material W is supplied to the industrial equipment.

[0016] Figure 2 illustrates a determination device 30 for determining the number of magnetic materials W attracted to a magnetic gripper 10. The determination device 30 is attached to the magnetic gripper 10. The determination device 30 includes a coil 30c, a voltage application circuit 32, a detection circuit 34, a control device 40, and a notification device 42.

[0017] When the magnetic gripper 10 approaches the magnetic material W and attracts the magnetic material W, the coil 30c approaches or comes into contact with the magnetic material W. The voltage application circuit 32 is connected to a DC power supply Ps. The power supply voltage Vs of the DC power supply Ps is a voltage that is capable of attracting the magnetic material W when the coil 30c is excited, and is, for example, 24 [V].

[0018] Even if there is an air gap between the coil 30c and the magnetic material W when the excitation of the coil 30c is started, the air gap disappears as the excited coil 30c attracts the magnetic material W. Since this state of no air gap occurs stably each time the coil 30c is excited, the accuracy of determining the number of magnetic materials W attracted to the magnetic gripper 10 is maintained.

[0019] The voltage application circuit 32 is a circuit capable of applying a voltage Vd to the coil 30c using the power supply voltage Vs of the DC power supply Ps. When the voltage application circuit 32 applies a DC voltage Vdd to the coil 30c, the coil 30c is energized and functions as an electromagnet. When the voltage application circuit 32 applies an alternating voltage Vda to the coil 30c, the coil 30c is demagnetized as the application time of the alternating voltage Vda gradually decreases.

[0020] In the determination device 30 according to this embodiment, the voltage application circuit 32 is composed of an H-bridge including a plurality of switches. The plurality of switches included in the H-bridge are switches SW1, SW2, SW3, and SW4 as shown in Figure 2. Switches SW1 and SW2 are connected in series from the DC power supply Ps toward ground. Switches SW3 and SW4 are connected in series from the DC power supply Ps toward ground.

[0021] One end Ea of coil 30c is electrically connected between switch SW1 and switch SW2. The other end Eb of coil 30c is electrically connected between switch SW3 and switch SW4. The control device 40 controls the voltage application circuit 32 by opening and closing switches SW1, SW2, SW3, and SW4. In this way, the control device 40 controls the voltage Vd applied to coil 30c. As a result, coil 30c is energized or demagnetized.

[0022] Assume that switches SW1 and SW4 are turned ON, and switches SW2 and SW3 are turned OFF. In this case, a voltage Vd is applied to coil 30c, and a current Id flows from one end Ea to the other end Eb of coil 30c. Assume that switches SW2 and SW3 are turned ON, and switches SW1 and SW4 are turned OFF. In this case, a current Id flows from the other end Eb to one end Ea of coil 30c.

[0023] The detection circuit 34 is an electrical circuit for detecting the coil voltage Vc generated between the ends of the coil 30c. The ends of the coil 30c are one end Ea and the other end Eb as shown in Figure 2. The coil voltage Vc is generated between the ends of the coil 30c when a voltage Vd is applied to the coil 30c. The detection circuit 34 includes a current sensing resistor 34r, an amplifier 34a, a filter 34f, and an A / D converter 34c.

[0024] The current sensing resistor 34r is placed between the voltage application circuit 32 and ground. This allows the current flowing through the coil 30c and the current sensing resistor 34r to be detected. Based on the current detected using the current sensing resistor 34r, a voltage Vr corresponding to the coil voltage Vc can be detected. The amplifier 34a amplifies the detected voltage Vr, making the coil voltage Vc easier to detect. The filter 34f smooths the amplified voltage Vr. In accordance with the smoothed voltage Vr, the A / D converter 34c outputs a digital signal Ds to the control device 40. Alternatively, the digital signal Ds may be output according to the current detected using the current sensing resistor 34r.

[0025] The control device 40 includes an arithmetic unit 60 and a storage unit 62. The arithmetic unit 60 includes a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). In other words, the arithmetic unit 60 includes processing circuitry.

[0026] The memory unit 62 includes volatile memory such as RAM (Random Access Memory) and non-volatile memory such as ROM (Read Only Memory) or flash memory. The volatile memory is used as the processor's working memory. The non-volatile memory stores programs executed by the processor, predetermined percentages described later, multiple time thresholds described later, and so on.

[0027] The calculation unit 60 includes a control unit 70, a detection unit 72, a determination unit 74, a timing unit 76, a judgment unit 78, and an output unit 80. The calculation unit 60 executes a program stored in the storage unit 62 to realize the control unit 70, the detection unit 72, the determination unit 74, the timing unit 76, the judgment unit 78, and the output unit 80. At least a portion of the control unit 70, the detection unit 72, the determination unit 74, the timing unit 76, the judgment unit 78, and the output unit 80 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array), or by an electronic circuit including discrete devices.

[0028] The control unit 70 energizes the coil 30c by controlling the voltage application circuit 32 to apply a DC voltage Vdd to the coil 30c. The control unit 70 demagnetizes the coil 30c by controlling the voltage application circuit 32 to apply an alternating voltage Vda to the coil 30c. The control unit 70 controls the voltage application circuit 32 by switching a plurality of switches included in the H bridge that constitutes the voltage application circuit 32. Specifically, the control unit 70 controls the direction of the DC voltage Vdd and the alternating voltage Vda applied to the coil 30c by switching a plurality of switches.

[0029] The multiple switches are switch SW1, switch SW2, switch SW3, and switch SW4. The control unit 70 turns on switch SW1 and switch SW4, and turns off switch SW2 and switch SW3. As a result, a DC voltage Vdd is applied to coil 30c, so that the control unit 70 can excite coil 30c.

[0030] After the coil 30c is energized in this way, the control unit 70 turns on switches SW2 and SW3, and turns off switches SW1 and SW4. Then, the control unit 70 turns on switches SW1 and SW4 again, and turns off switches SW2 and SW3. The control unit 70 repeatedly performs this on / off switching control for multiple switches, shortening the on / off switching time each time. As a result, an alternating voltage Vda is applied to the coil 30c, and the control unit 70 can demagnetize the coil 30c.

[0031] Once coil 30c is almost demagnetized, the control unit 70 turns off all switches SW1, SW2, SW3, and SW4. This stops the application of voltage Vd to coil 30c and maintains the demagnetized state of coil 30c.

[0032] Furthermore, in order to stop the application of voltage Vd to coil 30c, the control unit 70 does not need to turn off all of switches SW1, SW2, SW3, and SW4. The control unit 70 may, for example, turn off switches SW1 and SW3 and turn on switches SW2 and SW4. Alternatively, the control unit 70 may, for example, turn off switches SW2 and SW4 and turn on switches SW1 and SW3. Since the voltage application circuit 32 is composed of an H-bridge including multiple switches, excitation and demagnetization of coil 30c can be achieved inexpensively.

[0033] The detection unit 72 uses the detection circuit 34 to detect the coil voltage Vc generated between the ends of the coil 30c. Specifically, the detection unit 72 detects the coil voltage Vc based on the digital signal Ds output from the A / D converter 34c.

[0034] As described above, when the magnetic gripper 10 approaches the magnetic material W and attracts it, the coil 30c approaches or comes into contact with the magnetic material W. When the determination device 30 receives a trigger input signal from an external device indicating that the magnetic gripper 10 has approached the magnetic material W and attracted it, the excitation of the coil 30c is started by applying a DC voltage Vdd to the coil 30c, as will be described later using Figure 3. The external device that is the source of the trigger input signal is, for example, the magnetic gripper 10, the robot 20, or a control device that controls the magnetic gripper 10 or the robot 20.

[0035] At a predetermined time Tb elapsed since the excitation of coil 30c began, the value of the coil voltage Vc has reached the first voltage V1, or has already reached the first voltage V1. The detection unit 72 detects that the value of the coil voltage Vc is the first voltage V1.

[0036] The determination unit 74 determines a second voltage V2 that is smaller than the first voltage V1 based on the first voltage V1. The second voltage V2 is obtained, for example, by multiplying the first voltage V1 by a predetermined ratio r (0 < r < 1). The value of the predetermined ratio r is determined in advance, as will be described later, and stored in the storage unit 62. The value of the predetermined ratio r is, for example, 0.9.

[0037] As will be described later using Figure 3, the excitation of coil 30c is started, and after the coil voltage Vc reaches the first voltage V1, coil 30c is demagnetized. After being excited and demagnetized in this way, coil 30c is excited again. The timing unit 76 measures the time Td required from when coil 30c is re-excited until the coil voltage Vc reaches the second voltage V2. The detection unit 72 detects that the coil voltage Vc is the second voltage V2.

[0038] The determination unit 78 determines whether or not there is one magnetic material W attached to the magnetic gripper 10, based on the required time Td measured by the timing unit 76. Specifically, the determination unit 78 determines whether or not there is one magnetic material W by comparing the required time Td with a time threshold previously stored by the storage unit 62. The time threshold is used to determine the number of magnetic materials W. This makes it possible to easily determine whether or not there is one magnetic material W attached to the magnetic gripper 10.

[0039] If multiple time thresholds are stored in advance, the determination unit 78 can determine whether the number of magnetic materials W is one, zero, or two or more by comparing the required time Td with the multiple time thresholds. If even more time thresholds are stored as multiple time thresholds, the determination unit 78 can determine how many magnetic materials W are in total by comparing the required time Td with the multiple time thresholds. This makes it possible to easily determine the number of magnetic materials W attracted to the magnet gripper 10.

[0040] The output unit 80 outputs the determination result of the determination unit 78's determination of the number of magnetic materials W to the notification device 42. If it is determined whether or not there is one magnetic material W, the determination result is output. If it is determined whether there is one magnetic material W, zero magnetic materials, or two or more magnetic materials W, the determination result is output. If it is determined how many magnetic materials W there are, the determination result is output.

[0041] The notification device 42 notifies the determination result of the determination unit 78, which outputs from the output unit 80, regarding the number of magnetic materials W. The notification device 42 has, for example, an indicator. In this embodiment, if the determination result indicates that there is one magnetic material W, the indicator lights up, for example, green. If the determination result indicates that there is more than one magnetic material W, the indicator lights up, for example, red. This allows the operator to visually determine whether or not there is one magnetic material W attached to the magnet gripper 10.

[0042] In addition, when the determination result indicates that the number of magnetic bodies W is 0 and when the determination result indicates that the number of magnetic bodies W is 2, the lighting color of the indicator may be made different. For example, when the determination result indicates that the number of magnetic bodies W is 0, the indicator lights up orange, and when the determination result indicates that the number of magnetic bodies W is 2, the indicator lights up red. The notification device 42 may have a display unit and / or an audio output unit other than the indicator.

[0043] FIG. 3 is a diagram illustrating the temporal change in the voltage Vd applied to the coil 30c, the temporal change in the current Id flowing through the coil 30c, and the temporal change in the detected coil voltage Vc. In the example shown in FIG. 3, when a DC voltage Vdd is applied to the coil 30c as the voltage Vd, the coil 30c is excited. In that case, the value of the voltage Vd indicates a positive value Va.

[0044] At time Tbs, when the control unit 70 acquires the above-described trigger input signal from an external device such as the robot 20, the control unit 70 controls the voltage application circuit 32 to apply the DC voltage Vdd to the coil 30c, thereby exciting the coil 30c. When the excitation of the coil 30c is started, a current Id starts to flow through the coil 30c. When the current Id flows through the coil 30c, a magnetic flux is generated in the coil 30c due to the excitation of the coil 30c.

[0045] Since an inductance L of the coil 30c is generated due to the change in the magnetic flux, the value of the current Id gradually increases. At time Tbe when a predetermined time Tb has elapsed since the excitation of the coil 30c was started at time Tbs, the value of the current Id reaches a steady value Ia or has already reached the steady value Ia.

[0046] When the excitation of the coil 30c starts at the time Tbs, a current Id flows through the coil 30c, thereby generating a coil voltage Vc in the coil 30c. As the current Id in the coil 30c gradually increases, the value of the coil voltage Vc also gradually increases. At the time Tbe when a predetermined time Tb has elapsed since the excitation of the coil 30c started at the time Tbs, the value of the coil voltage Vc reaches the first voltage V1 or has already reached the first voltage V1. The first voltage V1 is detected by the detection unit 72. As described above, the determination unit 74 determines the second voltage V2 based on the first voltage V1.

[0047] After the time Tbe, the coil 30c is demagnetized by applying an alternating voltage Vda as the voltage Vd to the coil 30c. In that case, the value of the voltage Vd alternately repeats a positive value Va and a negative value -Va. However, the time during which the voltage Vd having the positive value Va is applied and the time during which the voltage Vd having the negative value -Va is applied are repeated while decreasing.

[0048] In the example shown in FIG. 3, when the demagnetization of the coil 30c starts at the time Tbe and the value of the voltage Vd becomes the negative value -Va, the value of the current Id changes from the steady value Ia to zero and then gradually decreases. This means that the reverse current Id is increasing.

[0049] When the value of the current Id reaches -Ia / 2, the value of the voltage Vd becomes the positive value Va again. In that case, the value of the current Id changes from -Ia / 2 to zero and then gradually increases. When the value of the current Id reaches Ia / 4, the value of the voltage Vd becomes the negative value -Va again. In that case, the value of the current Id changes from Ia / 4 to zero and then gradually decreases. As described above, this means that the reverse current Id is increasing.

[0050] When the value of the current Id reaches -Ia / 8, the value of the voltage Vd becomes the positive value Va again. In that case, the value of the current Id changes from -Ia / 8 to zero and then gradually increases. When the value of the current Id reaches Ia / 16, the value of the voltage Vd becomes the negative value -Va again. In that case, the value of the current Id changes from Ia / 16 to zero and then gradually decreases. As described above, this means that the reverse current Id is increasing.

[0051] When the value of current Id reaches -Ia / 32, the value of voltage Vd becomes zero. That is, the application of the alternating voltage Vda to coil 30c ends. In this case, the value of current Id changes from -Ia / 32 to zero and then remains zero. Thus, the magnitude of current Id at the timing when it switches between rising and falling is 1 / 2 ｋ The value decreases as it is multiplied by two each time. The exponent k is a natural number. Since powers of two are suitable for calculations performed by the arithmetic unit 60, the control of the alternating voltage Vda by the control unit 70 can be accelerated.

[0052] The exponent k corresponds to the number of alternating voltages Vda applied to the coil 30c to demagnetize it. In this embodiment, as described above, k = 5. The exponent k is determined experimentally based on the inductance L of the coil 30c as described above. The larger the inductance L of the coil 30c, the more alternating voltages Vda need to be applied to demagnetize the coil 30c, so the exponent k is large. The smaller the inductance L of the coil 30c, the fewer alternating voltages Vda are needed to demagnetize the coil 30c, so the exponent k is small.

[0053] When demagnetization of coil 30c begins after time Tbe, the coil voltage Vc repeatedly rises from zero in accordance with the change in the magnitude of the current Id each time the current Id switches between rising and falling. After the value of the current Id changes from the steady value Ia to zero, and then gradually changes from zero to -Ia / 2, the coil voltage Vc gradually changes from zero to V1 / 2.

[0054] When the value of current Id changes from -Ia / 2 to zero, and then gradually from zero to Ia / 4, the coil voltage Vc gradually changes from zero to V1 / 4. When the value of current Id changes from Ia / 4 to zero, and then gradually from zero to -Ia / 8, the coil voltage Vc gradually changes from zero to V1 / 8.

[0055] When the value of current Id changes from -Ia / 8 to zero, and then gradually changes from zero to Ia / 16, the coil voltage Vc gradually changes from zero to V1 / 16. When the value of current Id changes from Ia / 16 to zero, and then gradually changes from zero to -Ia / 32, the coil voltage Vc gradually changes from zero to V1 / 32. When the value of current Id changes from -Ia / 32 to zero and then remains zero, the coil voltage Vc also remains zero. By applying an alternating voltage Vda as voltage Vd to coil 30c, coil 30c is quickly demagnetized.

[0056] After coil 30c is demagnetized, it is re-energized at time Tds. When the excitation of coil 30c is restarted at time Tds, a current Id flows through coil 30c, generating a coil voltage Vc. As the current Id in coil 30c gradually increases due to the re-energization of coil 30c, the value of the coil voltage Vc also gradually increases. The detection unit 72 detects that the value of the coil voltage Vc has reached the second voltage V2 at time Tde. The timing unit 76 measures the time Td required from the restart of excitation of coil 30c at time Tds until the value of the coil voltage Vc reaches the second voltage V2.

[0057] A first voltage V1 is detected when the coil 30c is energized for the first time. Therefore, by multiplying the first voltage V1 by the predetermined ratio r described above, the second voltage V2 to be used when the coil 30c is energized for the second time can be determined.

[0058] Furthermore, the coil 30c is demagnetized after the first excitation, and then the coil 30c is excited a second time. Therefore, the magnitude of the residual magnetic flux density remaining in the coil 30c after it has been demagnetized and before it is excited a second time is kept constant. Consequently, the accuracy of the coil voltage Vc when it is excited a second time can be improved, and the variation in the measured value of the required time Td can be suppressed.

[0059] By obtaining highly accurate coil voltage Vc and stable measurement values ​​of the required time Td, the accuracy of determining whether or not there is one magnetic material W attached to the magnetic gripper 10 can be improved.

[0060] When the coil voltage Vc reaches the second voltage V2, the control unit 70 controls the voltage application circuit 32 to apply an alternating voltage Vda to the coil 30c, thereby demagnetizing the coil 30c again. In the example shown in Figure 3, the control unit 70 starts demagnetizing the coil 30c at time Tde when the coil voltage Vc reaches the second voltage V2. That is, the coil voltage Vc never exceeds the second voltage V2 and reaches the first voltage V1. Therefore, there is no need to energize the coil 30c so that the coil voltage Vc exceeds the second voltage V2, and the power consumption of the coil 30c can be reduced.

[0061] The second demagnetization, performed after time Tde, is the same as the first demagnetization performed between time Tbe and time Tds described above, so its explanation is omitted. No voltage is applied to the coil 30c from the time the control unit 70 demagnetizes the coil 30c again until it receives a trigger input signal from the external device again. That is, neither the DC voltage Vdd nor the alternating voltage Vda is applied to the coil 30c. This reduces the energizing time of the coil 30c.

[0062] Therefore, power consumption by coil 30c and heat generation by coil 30c can be suppressed. As will be described later using equations (1) and (2), the first voltage V1, etc., also changes due to the heat generated by coil 30c. Consequently, by suppressing power consumption by coil 30c and heat generation by coil 30c, the judgment accuracy of the judgment unit 78 can be maintained with low power consumption.

[0063] As described above, when the magnetic flux through coil 30c changes due to the excitation of coil 30c, an inductance L is generated in coil 30c. Since magnetic materials W are attracted to the magnet gripper 10, the inductance L of coil 30c changes according to the number of magnetic materials W. Therefore, the rate of increase in the coil voltage Vc after the excitation of coil 30c is started changes according to the number of magnetic materials W. In other words, the required time Td measured by the timing unit 76 changes according to the number of magnetic materials W.

[0064] Figure 4A illustrates the change in coil voltage Vc detected when the number of magnetic materials W attached to the magnetic gripper 10 is 0. Figure 4B illustrates the change in coil voltage Vc detected when the number of magnetic materials W attached to the magnetic gripper 10 is 1. Figure 4C illustrates the change in coil voltage Vc detected when the number of magnetic materials W attached to the magnetic gripper 10 is 2.

[0065] In Figures 4A, 4B, and 4C, unlike in Figure 3, coil 30c is not demagnetized at time Tbe, which is after a predetermined time Tb has elapsed since the excitation of coil 30c began at time Tbs. Coil 30c is demagnetized some time after time Tbe. Also, in Figures 4A, 4B, and 4C, the number of times the coil voltage Vc rises from zero while coil 30c is demagnetized is different from that in Figure 3. However, these differences do not affect the following explanation regarding how the required time Td changes depending on the number of magnetic materials W.

[0066] In Figures 4A, 4B, and 4C, at time Tbe, after a predetermined time Tb has elapsed since the first excitation of coil 30c began at time Tbs, the value of the coil voltage Vc reaches the first voltage V1. As shown in Figure 4A, when the number of magnetic materials W attracted to the magnet gripper 10 is 0, the value of the predetermined time Tb is Tb0. As shown in Figure 4B, when the number of magnetic materials W attracted to the magnet gripper 10 is 1, the value of the predetermined time Tb is Tb1. As shown in Figure 4C, when the number of magnetic materials W attracted to the magnet gripper 10 is 2, the value of the predetermined time Tb is Tb2.

[0067] As described above, the inductance L of the coil 30c changes according to the number of magnetic materials W attracted to the magnetic gripper 10. Therefore, as the number of magnetic materials W increases, the rate of increase of the coil voltage Vc decreases, and the value of the predetermined time Tb increases. That is, the inequality Tb0 < Tb1 < Tb2 holds.

[0068] Similar to the first excitation of coil 30c, in the second excitation of coil 30c, which begins at time Tds, the rate of increase in the coil voltage Vc decreases as the number of magnetic materials W increases. Therefore, the time Td required from time Tds, when the second excitation begins, to time Tde, when the coil voltage Vc reaches the second voltage V2, also increases as the number of magnetic materials W increases.

[0069] As shown in Figure 4A, when the number of magnetic materials W attached to the magnetic gripper 10 is 0, the required time Td is Td0. As shown in Figure 4B, when the number of magnetic materials W attached to the magnetic gripper 10 is 1, the required time Td is Td1. As shown in Figure 4C, when the number of magnetic materials W attached to the magnetic gripper 10 is 2, the required time Td is Td2. As the number of magnetic materials W increases, the rate of increase of the coil voltage Vc decreases, and the required time Td increases. That is, the inequality Td0 < Td1 < Td2 holds.

[0070] Therefore, by determining the range of the required time Td when there is one magnetic material W through multiple experiments, the above-mentioned time threshold used to determine the number of magnetic materials W can be predetermined. For example, the lower limit threshold T1 and the upper limit threshold T2 of the time threshold are determined and stored in the storage unit 62. The time threshold may also be determined in advance using the magnetic material W to be supplied in each operation that requires the robot 20 to supply magnetic materials W to industrial equipment, and stored in the storage unit 62. Figure 5 shows an example of determining the number N of magnetic materials W attracted to the magnet gripper 10.

[0071] If the required time Td is less than the lower limit T1 of the time threshold, the number of magnetic materials W N is determined to be 0. The indicator on the notification device 42 lights up red. If the required time Td is greater than or equal to the lower limit T1 of the time threshold and less than the upper limit T2 of the time threshold, the number of magnetic materials W N is determined to be 1. The indicator on the notification device 42 lights up green. If the required time Td is greater than or equal to the upper limit T2 of the time threshold, the number of magnetic materials W N is determined to be 2 or more. The indicator on the notification device 42 lights up red.

[0072] Furthermore, by experimentally determining the range of the required time Td for each value of N = 2, 3, ..., three or more time thresholds may be determined and pre-stored in the storage unit 62. This makes it possible to determine the number of magnetic materials N even when the number of magnetic materials W is two or more. Also, if it is not necessary to consider the case where the number of magnetic materials N is zero, only the upper limit threshold T2 may be determined as the sole time threshold and pre-stored in the storage unit 62.

[0073] Furthermore, the time threshold may be the midpoint of the required time Td for each case where the number of magnetic materials W N differs by one. That is, the value obtained by multiplying the sum of the required time Td(n) when the number of magnetic materials W N is n and the required time Td(n+1) when the number of magnetic materials W N is n+1 by 1 / 2 is used as the time threshold for determining whether the number of magnetic materials W N is n or less, or n+1 or more. However, n is a non-negative integer.

[0074] By assuming an internal DC resistance Rc of coil 30c, the first voltage V1 described above can be expressed by equation (1), using the resistance Rs of the current sensing resistor 34r and the DC voltage Vdd applied to coil 30c. The time constant τ can be expressed by equation (2), using the internal DC resistance Rc of coil 30c, the resistance Rs of the current sensing resistor 34r, and the inductance L of coil 30c. V1 = Vdd・Rs / (Rs + Rc) ... (1) τ = L / (Rs + Rc) ... (2)

[0075] According to equations (1) and (2), when the internal DC resistance Rc of coil 30c changes due to temperature changes in the external environment or heat generation from coil 30c, the first voltage V1 and the time constant τ also change. In many cases, the amount of change in response to temperature changes is particularly large for the first voltage V1 than for the time constant τ. Therefore, in order to suppress the effect of temperature changes on the first voltage V1 when determining the above-mentioned time threshold, there is a first reason why it is preferable to make the second voltage V2 small.

[0076] On the other hand, as can be seen from Figures 4A, 4B, and 4C, there is a second circumstance that it is preferable to increase the second voltage V2 so that the difference in the required time Td depending on the number N of magnetic materials W becomes larger. Therefore, considering the first and second circumstances, it is necessary to determine an appropriate value for the predetermined ratio r by experiment. As described above, in this embodiment, r = 0.9 is used.

[0077] Figure 6 is a flowchart illustrating the procedure for determining the number N of magnetic materials W attracted to the magnetic gripper 10. This procedure is performed by executing a program stored in the storage unit 62 of the control device 40 after the control device 40 receives an instruction to start the determination process.

[0078] When this processing procedure is started, in step S1, the control unit 70 determines whether or not it has received a trigger input signal from an external device indicating that the magnetic gripper 10 has approached the magnetic material W and attracted the magnetic material W. If the answer in step S1 is YES, the processing procedure proceeds to step S2. If the answer in step S1 is NO, the processing procedure proceeds to step S17.

[0079] In step S2, the control unit 70 controls the voltage application circuit 32 to apply a DC voltage Vdd to the coil 30c, thereby exciting the coil 30c. In step S3, the detection unit 72 determines whether a predetermined time Tb has elapsed since the excitation of the coil 30c began. If the result in step S3 is YES, the process proceeds to step S4. If the result in step S3 is NO, the process returns to step S3.

[0080] In step S4, the detection unit 72 detects that the value of the coil voltage Vc is the first voltage V1. In step S5, the determination unit 74 determines the second voltage V2 based on the first voltage V1. In step S6, the control unit 70 demagnetizes the coil 30c by controlling the voltage application circuit 32 to apply an alternating voltage Vda to the coil 30c.

[0081] In step S7, the control unit 70 controls the voltage application circuit 32 to stop the application of voltage Vd to the coil 30c. As part of the control of the voltage application circuit 32 by the control unit 70, for example, all of the switches, namely switch SW1, switch SW2, switch SW3, and switch SW4, are turned off by the control unit 70.

[0082] In step S8, the control unit 70 energizes the coil 30c by controlling the voltage application circuit 32 to apply a DC voltage Vdd to the coil 30c. In step S9, the timing unit 76 starts measuring the required time Td. In step S10, the detection unit 72 detects the coil voltage Vc. In step S11, the detection unit 72 determines whether it has detected that the value of the coil voltage Vc detected in step S10 is the second voltage V2. If the answer in step S11 is YES, the process proceeds to step S12. If the answer in step S11 is NO, the process returns to step S10.

[0083] In step S12, the timing unit 76 finishes measuring the required time Td. In step S13, the determination unit 78 determines the number N of magnetic materials W attached to the magnetic gripper 10. For example, it determines whether or not there is one magnetic material W attached to the magnetic gripper 10. In step S14, the output unit 80 outputs the determination result of the number N of magnetic materials W to the notification device 42.

[0084] In step S15, the control unit 70 demagnetizes the coil 30c by controlling the voltage application circuit 32 to apply an alternating voltage Vda to the coil 30c. In step S16, the control unit 70 stops applying voltage Vd to the coil 30c by controlling the voltage application circuit 32. For example, all of the above-mentioned switches are turned off. In step S17, the control unit 70 determines whether or not there has been an instruction to the control device 40 to end the determination process. If the answer in step S17 is YES, this process procedure ends. If the answer in step S17 is NO, this process procedure returns to step S1.

[0085] With regard to the embodiments described above, the following additional information is disclosed.

[0086] (Note 1) The determination device (30) of the present disclosure is a determination device for determining the number (N) of magnetic materials (W) attracted to a magnetic gripper (10), and comprises a coil (30c), a voltage application circuit (32) capable of applying DC voltages (Vd, Vdd) and alternating voltages (Vd, Vda) to the coil using the power supply voltage (Vs) of a DC power supply (Ps), a control unit (70) that controls the voltage application circuit to apply the DC voltage to the coil to energize the coil and controls the voltage application circuit to apply the alternating voltage to the coil to demagnetize the coil, and a coil voltage (Vc) generated between the ends of the coil The system includes a detection circuit (34) for detection, a determination unit (74) that determines a second voltage (V2) smaller than the first voltage based on a first voltage (V1) which is the value of the coil voltage at a predetermined time (Tbe) after a predetermined time (Tb) has elapsed since the coil was energized by the application of the DC voltage to the coil, a timing unit (76) that measures the required time (Td) from when the coil is energized again after the coil has been energized and demagnetized by the control unit until the value of the coil voltage reaches the second voltage, and a determination unit (78) that determines whether or not the number of magnetic materials is one based on the required time. With this configuration, the accuracy of determining whether or not the number of magnetic materials attracted to the magnet gripper is one can be improved.

[0087] (Note 2) In the determination device described in Note 1, when the control unit acquires a trigger input signal, it controls the voltage application circuit to apply the DC voltage to the coil, thereby starting the excitation of the coil. The control unit demagnetizes the coil after the predetermined time has elapsed since the excitation of the coil was started. After the control unit demagnetizes the coil, when the coil voltage reaches the second voltage due to the coil being re-energized, the control unit controls the voltage application circuit to apply the alternating voltage to the coil, thereby demagnetizing the coil again. No voltage is applied to the coil between the time the control unit demagnetizes the coil again and the time the trigger input signal is acquired again. With this configuration, the energizing time to the coil can be reduced. Therefore, the determination accuracy of the determination unit can be maintained with low power consumption.

[0088] (Note 3) In the determination device described in Note 1, the voltage application circuit may be composed of an H-bridge including a plurality of switches (SW1, SW2, SW3, SW4), and the control unit may control the voltage application circuit by switching the plurality of switches. With such a configuration, the excitation and demagnetization of the coil can be realized at low cost.

[0089] (Note 4) The determination device described in any of Notes 1 to 3 further comprises a storage unit (62) that stores in advance time thresholds (T1, T2) used to determine the number of magnetic materials, and the determination unit determines whether or not the number of magnetic materials is one by comparing the required time with the time thresholds. With such a configuration, it is possible to easily determine whether or not the number of magnetic materials attracted to the magnet gripper is one.

[0090] (Note 5) The determination device described in Note 4 may be configured such that the storage unit stores a plurality of time thresholds in advance, and the determination unit compares the required time with the plurality of time thresholds to determine whether the number of magnetic materials is one, zero, or two or more. With such a configuration, the number of magnetic materials attached to the magnet gripper can be easily determined.

[0091] (Note 6) In the determination device described in Note 4, the storage unit may store a plurality of time thresholds in advance, and the determination unit may determine the number of magnetic materials by comparing the required time with the plurality of time thresholds. With such a configuration, the number of magnetic materials attracted to the magnet gripper can be easily determined.

[0092] (Note 7) The determination device described in any of Notes 1 to 3 may further include a notification device (42) that notifies the determination result of the determination unit regarding whether or not the number of magnetic materials is one. With such a configuration, the operator can visually determine whether or not the number of magnetic materials attracted to the magnet gripper is one.

[0093] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above.

[0094] 10...Magnetic gripper 20...Robot 30...Determination device 32...Voltage application circuit 34...Detection circuit 40...Control device 42...Notification device 60...Calculation unit 62...Storage unit 70...Control unit 72...Detection unit 74...Decision unit 76...Timekeeping unit 78...Determination unit 80...Output unit

Claims

1. A determination device (30) for determining the number (N) of magnetic materials (W) attracted to a magnetic gripper (10), comprising: a coil (30c); a voltage application circuit (32) capable of applying a DC voltage (Vd, Vdd) and an alternating voltage (Vd, Vda) to the coil using the power supply voltage (Vs) of a DC power supply (Ps); a control unit (70) that controls the voltage application circuit to energize the coil by applying the DC voltage to the coil and demagnetizes the coil by controlling the voltage application circuit to apply the alternating voltage to the coil; a detection circuit (34) for detecting a coil voltage (Vc) generated between both ends of the coil; and a determination unit (74) that determines a second voltage (V2) smaller than the first voltage based on a first voltage (V1) which is the value of the coil voltage at a time (Tbe) after a predetermined time (Tb) has elapsed since the excitation of the coil began by applying the DC voltage to the coil. A determination device comprising: a timing unit (76) that measures the time required (Td) from when the coil is energized and then demagnetized by the control unit until the coil voltage reaches the second voltage; and a determination unit (78) that determines whether the number of magnetic materials is one based on the required time.

2. A determination device according to claim 1, wherein the control unit, upon acquiring a trigger input signal, controls the voltage application circuit to apply the DC voltage to the coil, thereby starting the excitation of the coil; the control unit demagnetizes the coil after the predetermined time has elapsed since the excitation of the coil was started; after the control unit demagnetizes the coil, when the coil voltage reaches the second voltage due to the coil re-energizing the coil, the control unit controls the voltage application circuit to apply the alternating voltage to the coil, thereby demagnetizing the coil again; and no voltage is applied to the coil from the time the control unit demagnetizes the coil again until the trigger input signal is acquired again.

3. A determination device according to claim 1, wherein the voltage application circuit is composed of an H-bridge including a plurality of switches (SW1, SW2, SW3, SW4), and the control unit controls the voltage application circuit by switching the plurality of switches.

4. A determination device according to any one of claims 1 to 3, further comprising a storage unit (62) that stores in advance time thresholds (T1, T2) used to determine the number of magnetic materials, wherein the determination unit determines whether or not the number of magnetic materials is one by comparing the required time and the time thresholds.

5. A determination device according to claim 4, wherein the storage unit stores a plurality of time thresholds in advance, and the determination unit determines whether the number of magnetic materials is one, zero, or two or more by comparing the required time with the plurality of time thresholds.

6. A determination device according to claim 4, wherein the storage unit stores a plurality of time thresholds in advance, and the determination unit determines the number of magnetic materials by comparing the required time with the plurality of time thresholds.

7. A determination device according to any one of claims 1 to 3, further comprising a notification device (42) for notifying the determination result of the determination unit regarding whether or not the number of magnetic materials is one.

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