阅读说明：本技术 继电器故障检测电路以及机器人 (Relay fault detection circuit and robot ) 是由 伊藤基 于 2021-05-24 设计创作，主要内容包括：本申请公开了继电器故障检测电路以及机器人,可抑制继电器的闭合/断开的切换次数,判定继电器的短路故障。继电器故障检测电路的特征在于,具备：第一电压获取部,获取输入到电源电路的交流电压,并作为第一电压信号输出；第二电压获取部,获取设于所述电源电路的继电器的端子间电压,并作为第二电压信号输出；比较部,对所述第一电压信号的波形和所述第二电压信号的波形进行比较；以及判定部,根据所述比较的结果,判定所述继电器是否发生了故障。(The application discloses relay fault detection circuit and robot can restrain the switching frequency of closing/opening of relay, judges the short circuit fault of relay. The relay failure detection circuit is characterized by comprising: a first voltage acquisition unit that acquires an alternating voltage input to the power supply circuit and outputs the alternating voltage as a first voltage signal; a second voltage acquisition unit that acquires an inter-terminal voltage of a relay provided in the power supply circuit and outputs the inter-terminal voltage as a second voltage signal; a comparison unit that compares a waveform of the first voltage signal with a waveform of the second voltage signal; and a determination unit that determines whether or not the relay has failed, based on a result of the comparison.)

1. A relay failure detection circuit is characterized by comprising:

a first voltage acquisition unit that acquires an alternating voltage input to the power supply circuit and outputs the alternating voltage as a first voltage signal;

a second voltage acquisition unit that acquires an inter-terminal voltage of a relay provided in the power supply circuit and outputs the inter-terminal voltage as a second voltage signal;

a comparison unit that compares a waveform of the first voltage signal with a waveform of the second voltage signal; and

and a determination unit that determines whether or not the relay has failed, based on a result of the comparison.

2. The relay fault detection circuit of claim 1,

the determination unit determines that the relay has failed when a difference between a waveform of the first voltage signal and a waveform of the second voltage signal is equal to or greater than a predetermined threshold value.

3. The relay fault detection circuit according to claim 1 or 2,

the first voltage acquisition unit and the second voltage acquisition unit each have a digital conversion circuit using a photocoupler,

the first voltage signal is a digital signal indicating a change in the alternating voltage, and the second voltage signal is a digital signal indicating a change in the inter-terminal voltage of the relay.

4. The relay fault detection circuit according to claim 1 or 2,

the comparison unit performs the comparison when an excitation switch that supplies power to a coil of the relay is in an on state.

5. The relay fault detection circuit according to claim 1 or 2,

the first voltage signal is used in a power failure determination unit of the power supply circuit to determine whether or not input of the ac voltage is stopped.

6. The relay fault detection circuit according to claim 1 or 2,

when a predetermined time has elapsed, the comparison unit performs the comparison, and the determination unit determines whether or not the relay has failed.

7. The relay fault detection circuit of claim 6,

the second voltage acquisition unit includes a switch that switches whether or not to acquire the inter-terminal voltage, and outputs the second voltage signal when the switch is in a closed state when it is determined whether or not the relay has failed.

8. The relay fault detection circuit according to claim 1 or 2,

the relay is provided in a dual manner to the power circuit,

the relays that are duplicated are provided with the second voltage acquisition unit and the comparison unit, respectively,

the determination unit determines whether or not the relay has failed based on the result of the comparison,

when it is determined that a failure has occurred in one of the duplicated relays, the other of the duplicated relays is set to an on state.

9. A robot is characterized by comprising:

a motor as a power source;

a power supply circuit that supplies electric power for driving the motor; and

the relay fault detection circuit of any one of claims 1 to 8.

Technical Field

The invention relates to a relay fault detection circuit and a robot.

Background

Conventionally, an industrial robot is provided with an emergency stop circuit that immediately cuts off supply of electric power as an energy source to a motor as a power source at the time of an emergency stop. As means for cutting off power at the time of an emergency stop, there is, for example, means for turning on a relay provided on a supply line of ac power. A relay provided in a power supply line may fail to be in an open state due to welding of a contact. Therefore, it is desirable to detect a relay failure due to welding (hereinafter also referred to as "welding failure"). For example, patent document 1 discloses a technique for detecting a welding failure of a relay.

The detection of the welding failure described in patent document 1 is achieved by causing relays of a double emergency stop circuit to alternately perform on/off operations by on/off control signals of respective excitation switches, and comparing voltage signals of respective relay contacts to detect which relay contact is welded.

Patent document 1: japanese patent laid-open No. 2006-119995

Disclosure of Invention

However, in the welding detection disclosed in patent document 1, the closing/opening operation of at least one of the respective excitation switches is repeated twice. Since the relay is a mechanical contact, it is desirable to detect a failure of the relay with as few times of closing/opening as possible in consideration of the life of the relay.

According to one aspect of the present disclosure, a relay fault detection circuit is provided. The relay failure detection circuit is characterized by comprising: a first voltage acquisition unit that acquires an alternating voltage input to the power supply circuit and outputs the alternating voltage as a first voltage signal; a second voltage acquisition unit that acquires an inter-terminal voltage of a relay provided in the power supply circuit and outputs the inter-terminal voltage as a second voltage signal; a comparison unit that compares a waveform of the first voltage signal with a waveform of the second voltage signal; and a determination unit that determines whether or not the relay has failed, based on a result of the comparison of the waveforms.

Drawings

Fig. 1 is a schematic configuration diagram of a control device including a relay failure detection circuit according to a first embodiment.

Fig. 2 is an explanatory diagram showing an ac voltage signal, a relay terminal voltage signal, and a comparison signal.

Fig. 3 is a table showing an example of the determination mode of the determination unit.

Fig. 4 is a schematic configuration diagram of a control device including a relay failure detection circuit according to a second embodiment.

Fig. 5 is an explanatory diagram showing a digital ac voltage signal, a digital relay inter-terminal voltage signal, and a comparison signal.

Fig. 6 is an explanatory diagram showing a digital ac voltage signal, a relay terminal-to-terminal voltage signal, and a comparison signal when the first relay has a short-circuit fault.

Fig. 7 is an explanatory diagram showing a digital ac voltage signal, a relay terminal-to-terminal voltage signal, and a comparison signal when a short-circuit fault occurs in the second relay.

Fig. 8 is a configuration diagram of an ac voltage acquisition unit having a different connection configuration.

Fig. 9 is a schematic configuration diagram of a control device including a relay failure detection circuit according to a third embodiment.

Fig. 10 is an explanatory diagram showing a digital ac voltage signal, a digital relay inter-terminal voltage signal, and a comparison signal.

Fig. 11 is a schematic configuration diagram of a robot according to a fourth embodiment.

Description of the reference numerals

10. 10B, 10C, a control device; 100. a power supply circuit; 110. an AC input circuit; 120. an emergency stop circuit; 130. a rectifying circuit; 132. a bridge diode; 134. a smoothing capacitor; 136. a discharge resistor; 200. a drive circuit; 300. 300B, 300C, a relay fault detection circuit; 310. 310B, 310M, an ac voltage acquisition unit (first voltage acquisition unit); 320a, 320Ba, 320Ca, a relay voltage acquisition unit (second voltage acquisition unit); 320b, 320Bb, 320Cb, a relay voltage acquisition unit (second voltage acquisition unit); 330a, 330Ba, a comparison unit; 330b, 330Bb, comparison unit; 340. a determination unit; 400. a control unit; 500. a robot; 501. a robot main body; 502. a control device; 503. a computer; 611. a base; 612. an arm; 614. a hand portion; 621. a first arm section; 622. a second arm section; 623. a third arm portion; 624. a fourth arm section; 625. a fifth arm section; 626. a sixth arm section; 651. a first driving section; 652. a second driving section; 653. a third driving section; 654. a fourth driving section; 655. a fifth driving section; 656. a sixth driving section; t1, T2, input terminal; l1, L2, ac line; RLa, RLb, relays; vc1, Vc2, direct current voltage; GD1, GD 2; grounding; PCo, PCa, PCb, photocoupler; LDo, LDa, LDb, light emitting diode; PTo, PTA, PTb, phototransistor; dco, Dca, Dcb, diodes; rca, Rcb, input resistance; rcco, collector resistance; reo, Rea, Reb, emitter resistance; rso, Rsa, Rsb, shunt resistance; SDa, SDb, detection enable switch; SEa, SEb, emergency stop switch; SRa, SRb, power switch.

Detailed Description

A. The first embodiment:

fig. 1 is a schematic configuration diagram of a control device 10 including a relay failure detection circuit 300 according to a first embodiment. The control device 10 is shown as an example of a control device that controls driving of the motor 20. The control device 10 includes a power supply circuit 100, a drive circuit 200 of the motor 20, a relay failure detection circuit 300, and a control unit 400.

The power supply circuit 100 includes an ac input circuit 110, an emergency stop circuit 120, and a rectifier circuit 130. The AC input circuit 110 includes a pair of AC lines L1 and L2, and the pair of AC lines L1 and L2 supply the rectifier circuit 130 with an AC voltage AC input from an AC power supply connected to the pair of input terminals T1 and T2. Relays RLa and RLb that cut off the supply of the AC voltage AC to the rectifier circuit 130 are provided in the AC lines L1 and L2. The relays RLa and RLb are controlled to open and close by an emergency stop circuit 120 described later.

The rectifier circuit 130 includes a bridge diode 132, a smoothing capacitor 134, and a discharge resistor 136, rectifies the AC voltage AC by the bridge diode 132, smoothes the AC voltage AC by a smoothing circuit including the smoothing capacitor 134 and the discharge resistor 136, and converts the AC voltage AC into a DC voltage DC. The direct-current voltage DC is supplied to the drive circuit 200.

The drive circuit 200 converts the supplied direct-current voltage DC into a drive voltage for the motor 20 and supplies the drive voltage to the motor 20, based on a control signal MDC supplied from the control unit 400. Thereby, the motor 20 is driven by the supplied driving voltage.

The emergency stop circuit 120 includes a first emergency stop switch SEa and a first power supply switch SRa for the first relay RLa, and includes a second emergency stop switch SEb and a second power supply switch SRb for the second relay RLb. The coils of the first emergency stop switch SEa, the first power switch SRa, and the first relay RLa are connected in series between the ground GD1 of the emergency stop circuit 120 and the dc voltage Vc 1. Similarly, the coils of the second emergency stop switch SEb, the second power switch SRb, and the second relay RLb are connected in series between the ground GD1 and the dc voltage Vc 1. The dc voltage Vc1 and the ground GD1 are generated by a power supply circuit, not shown, using the AC voltage AC from the input terminals T1 and T2.

The emergency stop switches SEa and SEb are switches that are turned on by, for example, an operator pressing an emergency stop button (not shown) when an abnormality occurs, and normally maintain a closed state. The power switches SRa and SRb are normally kept in an on state, and are turned into an off state by, for example, pressing a power button to supply a control signal from the control unit 400. The power switches SRa and SRb correspond to excitation switches for supplying electric power to the coils of the relays RLa and RLb, and the coils of the relays RLa and RLb are excited by closing the power switches SRa and SRb, whereby the switches of the relays RLa and RLb are closed. The AC voltage AC is supplied to the rectifier circuit 130 and the DC voltage DC is supplied to the drive circuit 200 by closing the switches of the relays RLa and RLb. Thereby, the drive circuit 200 supplies electric power to the motor 20, and the motor 20 is driven.

The relay failure detection circuit 300 includes: an ac voltage acquisition unit 310 corresponding to a first voltage acquisition unit, a pair of relay voltage acquisition units 320a and 320b corresponding to a second voltage acquisition unit, a pair of comparison units 330a and 330b, and a determination unit 340.

The ac voltage obtaining unit 310 is connected in parallel to an ac power supply connected between the pair of input terminals T1 and T2. The ac voltage acquisition unit 310 acquires ac voltages input from a pair of input terminals T1 and T2 and outputs the ac voltages as an ac voltage signal Vac.

The first relay voltage obtaining part 320a is provided in parallel with the first relay RLa, and the second relay voltage obtaining part 320b is provided in parallel with the second relay RLb. The first relay voltage obtaining unit 320a obtains the inter-terminal voltage of the first relay RLa and outputs the inter-terminal voltage as a first relay inter-terminal voltage signal Va. The second relay voltage obtaining portion 320b obtains the inter-terminal voltage of the second relay RLb, and outputs the inter-terminal voltage as a second relay inter-terminal voltage signal Vb.

The first comparator 330a compares the waveform of the ac voltage signal Vac with the waveform of the first relay inter-terminal voltage signal Va, and outputs the comparison result as a first comparison signal DSa. The second comparison unit 330b compares the waveform of the ac voltage signal Vac with the waveform of the second relay inter-terminal voltage signal Vb, and outputs the comparison result as a second comparison signal DSb.

The ac voltage signal Vac corresponds to a first voltage signal, and the first relay inter-terminal voltage signal Va and the second relay inter-terminal voltage signal Vb correspond to a second voltage signal.

The determination unit 340 determines whether or not the first relay RLa has a failure based on the first comparison signal DSa and determines whether or not the second relay RLb has a failure based on the second comparison signal DSb during a determination permission period set based on the determination permission signal DE supplied from the control unit 400. The determination unit 340 is composed of a dedicated logic circuit for realizing these determination functions. The determination permission period may be set at predetermined constant intervals, for example. As described above, compared with the case where the determination is performed all the time, the load applied to the determination unit 340 can be reduced, power saving of the relay failure detection circuit can be achieved, and power saving of the device can be achieved. However, the present invention is not limited to this, and the determination may be performed all the time.

The control unit 400 controls the power switches SRa and SRb based on the determination signal FDS indicating the determination result supplied from the determination unit 340. Specifically, regardless of the pressed state of the power button performed by the operator, the control unit 400 controls the second power switch SRb to be in the on state when the first relay RLa is determined to be faulty, and controls the first power switch SRa to be in the on state when the second relay RLb is determined to be faulty. The control Unit 400 is configured by a computer including, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input/output interface, and the like.

The determination unit 340, which is formed of a dedicated logic circuit, may be formed of a computer in the same manner as the control unit 400. Determination unit 340 may be incorporated in control unit 400.

Fig. 2 is an explanatory diagram showing the ac voltage signal Vac, the relay terminal voltage signals Va and Vb, and the comparison signals DSa and DSb. The alternating-current voltage signal Vac obtained by the alternating-current voltage obtaining unit 310 changes in synchronization with the periodic change of the alternating-current voltage AC, regardless of whether the power switches SRa and SRb are in the closed state (ON) and the relays RLa and RLb are in the closed state (ON) or the power switches SRa and SRb are in the open state (OFF) and the relays RLa and RLb are in the open state (OFF). Vav represents a central value of the alternating voltage that changes periodically.

In contrast, the relay inter-terminal voltage signals Va and Vb obtained by the relay voltage obtaining units 320a and 320b are different depending on whether the relays RLa and RLb are in the open state or the closed state.

When the relays RLa and RLb are in the closed state, no potential difference occurs between the relay terminals, and therefore the relay terminal voltage signals Va and Vb have constant values, which are generally the same values Vav as the center value of the voltage at the time of the periodic variation, for example, the center value of the ac voltage signal Vac. When the relays RLa and RLb are in the on state, the relay inter-terminal voltage signals Va and Vb periodically change in the same manner as the ac voltage signal Vac. However, the voltage amplitude is about 1/2 compared to the ac voltage signal Vac. When one of the relays RLa and RLb is in the open state and the other of the relays RLb and RLa is in the closed state, the amplitudes of the relay inter-terminal voltage signals Va and Vb are approximately equal to the amplitude of the ac voltage signal Vac. That is, when the corresponding relay RLa, RLb is in the on state, the relay inter-terminal voltage signals Va, Vb are signals whose amplitude relative to the ac voltage signal Vac varies periodically with a magnitude of about 1/2 to 1.

Therefore, the relay inter-terminal voltage signals Va and Vb have different amplitudes when the relays RLa and RLb are in the on state, but change in accordance with the periodic change of the ac voltage signal Vac, and have a constant value Vav when the relays RLa and RLb are in the off state.

The first comparator 330a outputs a first comparison signal DSa corresponding to a comparison result between the ac voltage signal Vac and the first relay terminal voltage signal Va. As described above, when the first relay RLa is in the on state and the difference between the ac voltage signal Vac and the first relay inter-terminal voltage signal Va is ignored in terms of the difference in amplitude, the ac voltage signal Vac and the first relay inter-terminal voltage signal Va are periodically changed in accordance with each other. In this case, the first comparing unit 330a outputs a pulse signal that changes in synchronization with the periodic change of the ac voltage signal Vac as the first comparison signal DSa. In contrast, when the first relay RLa is in the closed state, the first relay inter-terminal voltage signal Va is a constant value Vav, and the difference between the ac voltage signal Vac and the first relay inter-terminal voltage signal Va is a difference larger than the above-described negligible difference. In this case, the first comparing unit 330a outputs a signal fixed to a constant level, in this example, a signal fixed to an L level, as the first comparison signal DSa. Further, by comparing a predetermined threshold value with the difference between the ac voltage signal Vac and the first relay terminal voltage signal Va, it is possible to detect a large difference in the closed state of the first relay RLa by ignoring the difference due to the difference in the amplitude of the open state of the first relay RLa.

The second comparator 330b also outputs, as the second comparison signal DSb, a pulse signal that changes in synchronization with the periodic change of the ac voltage signal Vac when the second relay RLb is in the open state, and a signal that is fixed at a constant level when the second relay RLb is in the closed state, as in the first comparator 330 a.

Here, it is understood that when the first power switch SRa is in the on state, the first relay inter-terminal voltage signal Va is a constant value and the first comparison signal DSa is a fixed signal, the switch of the first relay RLa that should be in the on state is in the off state. Similarly, when the second power switch SRb is in the on state, and the second relay inter-terminal voltage signal Vb is a constant value and the second comparison signal DSb is a fixed signal, it can be seen that the switch of the second relay RLb, which should be in the on state, is in the off state.

For this reason, the determination unit 340 can determine the short-circuit fault of the first relay RLa based on the state of the first comparison signal DSa when the first relay RLa is set to the on state. Similarly, the short-circuit fault of the second relay RLb can be determined from the state of the second comparison signal DSb when the second relay RLb is set to the on state. As short-circuit faults of the relays RLa and RLb, short-circuit faults due to contact welding, short-circuit faults due to foreign matter, and the like are conceivable.

Fig. 3 is a table showing an example of the determination mode of the determination unit 340. When the first comparison signal DSa and the second comparison signal DSb are pulse signals, the first relay RLa and the second relay RLb are determined to be normal. In the case where only the first comparison signal DSa is a fixed signal, the first relay RLa is determined as a short-circuit fault and the second relay RLb is determined as normal. In the case where only the second comparison signal is a fixed signal, the first relay RLa is determined to be normal and the second relay RLb is determined to be a short-circuit fault. When the first comparison signal DSa and the second comparison signal DSb are fixed signals, the first relay RLa and the second relay RLb are determined as a short-circuit fault. When the power switches SRa and SRb are in the on state and the determination is permitted by the determination permission signal DE, the determination unit 340 performs the determination.

The determination unit 340 outputs the result of the failure determination to the control unit 400 as a determination signal FDS. The control unit 400 controls the operation of the power supply circuit 100 based on the result of the failure determination provided by the determination signal FDS. For example, when both the relays RLa and RLb are normal, normal operation control is executed. When one of the relays RLa and RLb is determined to be short-circuited, switching of the power switch corresponding to the other relay is controlled so as to be fixed to an on state, and the other relay cannot be in an off state. This can cut off the supply of electric power from the power supply circuit 100 to the drive circuit 200.

As described above, in the relay failure detection circuit 300 according to the first embodiment, when the power switches SRa and SRb are in the on state and the relays RLa and RLb are in the on state, the short-circuit failure of the relays RLa and RLb can be determined by comparing the waveform of the ac voltage signal Vac with the waveforms of the relay inter-terminal voltage signals Va and Vb. Thus, when the relay is set to the on state, the short-circuit failure of the relay can be determined without switching the setting. In addition, when the relay is set to the closed state, the short-circuit failure of the relay can be determined by switching the setting of the relay from the closed state to the open state once. Therefore, it is possible to determine a short-circuit failure of the relay while suppressing a reduction in the life of the relay with a smaller number of times of switching of the relay than in the case described in the technical problem.

The relay fault detection circuit 300 can independently determine a short-circuit fault by independently acquiring the inter-terminal voltage of the relay for each of the pair of the double relays RLa and RLb. Thus, even when one of the pair of relays RLa and RLb that have been duplicated is determined to be short-circuited, the other relay is turned on, thereby cutting off the supply of electric power from power supply circuit 100 to motor 20.

B. Second embodiment:

fig. 4 is a schematic configuration diagram of a control device 10B including a relay failure detection circuit 300B according to a second embodiment. A control device 10B of the second embodiment is the same as the control device 10 of the first embodiment, except that the relay failure detection circuit 300 of the control device 10 (see fig. 1) is replaced with a relay failure detection circuit 300B. However, in fig. 4, the emergency stop circuit 120 and the control unit 400 among the components of the power supply circuit 100 are not shown. Further, other structures and functions are the same as those of the first embodiment, and therefore, the same description is omitted by assigning the same or similar reference numerals as those used in the first embodiment.

The relay failure detection circuit 300B includes an ac voltage acquisition unit 310B, relay voltage acquisition units 320Ba and 320Bb, and comparison units 330Ba and 330Bb, instead of the ac voltage acquisition unit 310, the relay voltage acquisition units 320a and 320B, and the comparison units 330a and 330B (see fig. 1).

The ac voltage acquisition unit 310B includes: a diode Dco, an input resistance Rco, and a light emitting diode LDo of the photocoupler PCo connected in series between the input terminals T1, T2; and a shunt resistor Rso connected in parallel with the light emitting diode LDo. The diode Dco and the light-emitting diode LDo are connected so that the first input terminal T1 side is an anode side and the second input terminal T2 side is a cathode side. The ac voltage acquisition unit 310B has a phototransistor PTo and an emitter resistor Reo of a photocoupler PCo connected in series between the ground GD2 and the dc voltage Vc2, and outputs the emitter output as an ac voltage signal Vac. An input side circuit including the light emitting diode LDo provided between the input terminals T1, T2 is insulated from an output side circuit including the phototransistor PTo provided between the ground GD2 and the dc voltage Vc 2.

The ac voltage acquisition unit 310B functions as an AD converter circuit that converts an analog voltage waveform (sinusoidal waveform) input between the input terminals T1 and T2 into a digital voltage waveform (rectangular waveform) and outputs the digital voltage waveform as a digital ac voltage signal Vac. When the potential of the first input terminal T1 is higher than the potential of the second input terminal T2, the input resistance Rco and the shunt resistance Rso are set in accordance with the characteristics of the light emitting diode LDo and the phototransistor PTo so that the light emitting diode LDo is turned on (emits light) and the phototransistor PTo is turned on. When the potential of the first input terminal T1 is lower than the potential of the second input terminal T2, the input resistance Rco and the shunt resistance Rso are set in accordance with the characteristics of the light-emitting diode LDo and the phototransistor PTo so that the light-emitting diode LDo is turned off (non-light-emission) and the phototransistor PTo is turned off.

Similarly to ac voltage acquisition unit 310B, first relay voltage acquisition unit 320Ba includes: a diode Dca, an input resistor Rca, and a light emitting diode LDa of the photocoupler PCa connected in series between terminals of the first relay RLa; and a shunt resistor Rsa connected in parallel with the light emitting diode LDa. The diode Dca and the light-emitting diode LDa are connected such that the first input terminal T1 side is an anode side and the bridge diode 132 side is a cathode side. Further, a detection permission switch SDa is provided on the cathode side of the diode Dca. Further, the first relay voltage acquisition unit 320Ba includes: the phototransistor PTa and the emitter resistor Rea of the photocoupler PCa connected in series between the ground GD2 and the dc voltage Vc2 output the emitter output as the first relay inter-terminal voltage signal Va. An input side circuit including the light emitting diode LDa provided between the terminals of the first relay RLa and an output side circuit including the phototransistor PTa provided between the ground GD2 and the dc voltage Vc2 are insulated.

The first relay voltage acquisition unit 320Ba functions as an AD converter circuit that converts an analog voltage waveform generated between the terminals of the first relay RLa into a digital voltage waveform (rectangular waveform) and outputs the converted voltage waveform as a digital first relay inter-terminal voltage signal Va when the detection permission switch SDa is in the closed state. The detection permission switch SDa is opened and closed under the control of the control unit 400 (see fig. 1). When the potential of the terminal of the first relay RLa on the first input terminal T1 side is higher than the potential of the terminal on the opposite side, the input resistance Rca and the shunt resistance Rsa are set in accordance with the characteristics of the light emitting diode LDa and the phototransistor PTa so that the light emitting diode LDa is turned on (light emitting) and the phototransistor PTa is turned on. When the potential of the terminal of the first relay RLa on the first input terminal T1 side is lower than the potential of the terminal on the opposite side, the input resistance Rca and the shunt resistance Rsa are set in accordance with the characteristics of the light emitting diode LDa and the phototransistor PTa so that the light emitting diode LDa is turned off (non-emitting) and the phototransistor PTa is turned off.

The second relay voltage acquisition unit 320Bb includes, in the same manner as the first relay voltage acquisition unit 320 a: a detection permission switch SDb, a diode Dcb, an input resistor Rcb, and a light emitting diode LDb of the photocoupler PCb, which are connected in series between terminals of the second relay RLb; and a shunt resistor Rsb connected in parallel with the light emitting diode LDb. The diode Dcb and the light-emitting diode LDb are connected such that the bridge diode 132 side is an anode side and the second input terminal T2 side is a cathode side. In addition, the second relay voltage acquisition unit 320Bb includes: the phototransistor PTb and the emitter resistor Reb of the photocoupler PCb, which are connected in series between the ground GD2 and the dc voltage Vc2, output the emitter output as the second relay inter-terminal voltage signal Vb. An input side circuit including the light emitting diode LDb provided between the terminals of the second relay RLb and an output side circuit including the phototransistor PTb provided between the ground GD2 and the dc voltage Vc2 are insulated.

Similarly to the first relay voltage acquisition unit 320Ba, the second relay voltage acquisition unit 320Bb also functions as an AD converter circuit that converts an analog voltage waveform generated between the terminals of the second relay RLb into a digital voltage waveform and outputs the digital voltage waveform as a digital second relay inter-terminal voltage signal Vb when the detection permission switch SDb is in the closed state. The detection permission switch SDb is also opened and closed by the control of the control unit 400 (see fig. 1). The input resistance Rcb and the shunt resistance Rsb of the input side circuit are set in accordance with the characteristics of the light emitting diode LDb and the phototransistor PTb in accordance with the change in the voltage between the terminals of the second relay RLb so that the phototransistor PTb is turned on and off.

Fig. 5 is an explanatory diagram showing a digital ac voltage signal Vac, digital relay inter-terminal voltage signals Va and Vb, and comparison signals DSa and DSb in the relay failure detection circuit 300B. The digital AC voltage signal Vac obtained by the AC voltage obtaining unit 310B is a pulse signal that periodically varies in synchronization with the periodic variation of the AC voltage AC.

The digital first relay inter-terminal voltage signal Va acquired by the first relay voltage acquisition unit 320Ba changes according to the state of the first relay RLa. That is, when the first relay RLa is in the closed state, as described in the first embodiment (see fig. 2), since no potential difference is generated between the terminals of the first relay RLa, the digital first relay inter-terminal voltage signal Va is a signal fixed to a constant level, in this example, a fixed signal fixed to an L (low) level, as shown in fig. 5. On the other hand, when the first relay RLa is in the on state, a potential difference (see fig. 2) that periodically changes in synchronization with the periodic change of the ac voltage signal Vac occurs between the terminals of the first relay RLa, and therefore, as shown in fig. 5, the digital first relay inter-terminal voltage signal Va is a pulse signal that periodically changes in synchronization with the periodic change of the digital ac voltage signal Vac.

Therefore, the ac voltage signal Vac and the first relay inter-terminal voltage signal Va are pulse signals that match each other when the first relay RLa is in the open state, regardless of variations in timing of the periodic variation of the first relay RLa, and are inconsistent signals when the first relay RLa is in the closed state.

As shown in fig. 5, the second relay inter-terminal voltage signal Vb is a signal that changes in accordance with the state of the second relay RLb, similarly to the change in the first relay inter-terminal voltage signal Va in accordance with the state of the first relay RLa.

Therefore, the first comparator 330Ba compares the digital ac voltage signal Vac with the digital first relay inter-terminal voltage signal Va, and outputs a first comparison signal DSa corresponding to a difference (difference) between comparison results due to a difference in the state of the first relay RLa. Specifically, as shown in fig. 5, when the first relay RLa is in the open state, a pulse signal that changes in accordance with changes in the digital ac voltage signal Vac and the digital first relay inter-terminal voltage signal Va is output as the first comparison signal DSa, and when the first relay RLa is in the closed state, a fixed signal at a fixed level, which in this example is at the L level, is output as the first comparison signal DSa.

As shown in fig. 5, the second comparator 330Bb outputs a second comparison signal DSb corresponding to a difference (difference) in comparison result due to a difference in state of the second relay RLb, as in the case of the first comparator 330 Ba.

The comparison units 330Ba and 330Bb operating as described above can be configured using, for example, a logic circuit called a matching circuit.

As described in the first embodiment, the determination unit 340 may determine the short-circuit fault of the first relay RLa and the second relay RLb based on the states of the first comparison signal DSa and the second comparison signal DSb when the first relay RLa and the second relay RLb are set to the on state.

Fig. 6 is an explanatory diagram showing digital ac voltage signals Vac, relay terminal-to-terminal voltage signals Va, Vb, and comparison signals DSa, DSb at the time of short-circuit failure of the first relay RLa, and fig. 7 is an explanatory diagram showing digital ac voltage signals Vac, relay terminal-to-terminal voltage signals Va, Vb, and comparison signals DSa, DSb at the time of short-circuit failure of the second relay RLb.

As described in the first embodiment, since the state in which the first relay RLa is short-circuited is the same as the case in which the first relay RLa is set to the closed state, the first comparison signal DSa is a fixed signal even when the first relay RLa is set to the open state as shown in fig. 6. The same applies to the case where the second relay RLb has a short-circuit fault, and as shown in fig. 7, the second comparison signal DSb is a fixed signal even when the second relay RLb is set to the on state.

Therefore, as described in the first embodiment, the determination unit 340 can determine the short-circuit fault of the first relay RLa and the second relay RLb based on the states of the first comparison signal DSa and the second comparison signal DSb when the first relay RLa and the second relay RLb are set to the on state (see fig. 3).

Therefore, in the relay failure detection circuit 300B according to the second embodiment as well, similarly to the first embodiment, when the power switches SRa and SRb are in the on state and the relays RLa and RLb are in the on state, the short-circuit failure of the relays RLa and RLb can be determined by comparing the waveform of the digital ac voltage signal Vac with the waveforms of the digital relay inter-terminal voltage signals Va and Vb. In the relay failure detection circuit 300B according to the second embodiment, even when one of the pair of double relays RLa and RLb is determined to be short-circuited, the other power switch cannot be closed, so that the other relay can be kept open, and the power supply from the power supply circuit 100 to the motor 20 can be cut off.

In the relay failure detection circuit 300B according to the second embodiment, only when the detection permission switches SDa and SDb are in the closed state, the relay voltage acquisition units 320Ba and 320Bb can be set from the non-operating state to the operating state, and the voltage between the terminals of the relays RLa and RLb can be detected to determine the short-circuit failure of the relays. For example, by making the relay voltage acquisition units 320Ba and 320Bb operable only during the determination permission period set by the determination permission signal DE, it is possible to reduce the load applied to the relay voltage acquisition units 320Ba and 320Bb and the comparison units 330Ba and 330Bb, to achieve power saving of the relay failure detection circuit, and to achieve power saving of the device.

In the relay failure detection circuit 300B according to the second embodiment, the AC voltage signal Vac indicating the AC voltage AC input between the input terminals T1 and T2 and the relay inter-terminal voltage signals Va and Vb indicating the inter-terminal voltages of the relays RLa and RLb are digital voltage waveforms rather than analog voltage waveforms. This makes it possible to suppress a decrease in the comparison accuracy due to fluctuations included in the simulated voltage waveform and a decrease in the comparison accuracy corresponding to a low resolution, which are caused when the simulated voltage waveforms as in the first embodiment are compared, and further, to perform highly accurate comparison and highly accurate failure detection.

Further, since the ac voltage acquisition unit 310B and the relay voltage acquisition units 320Ba and 320Bb use photocouplers to insulate the input-side circuit and the output-side circuit, the circuit configurations thereof can be reduced in size.

Fig. 8 is a configuration diagram of ac voltage acquisition unit 310M showing a connection configuration different from that of ac voltage acquisition unit 310B. The ac voltage acquisition unit 310B (see fig. 4) is connected such that the anodes of the diodes Dco and the light-emitting diodes LDo face the first input terminal T1 side and the cathodes thereof face the second input terminal T2 side. In contrast, as shown in fig. 8, the diodes Dco and the light-emitting diodes LDo may be connected such that the anodes thereof face the second input terminal T2 side and the cathodes thereof face the first input terminal T1 side. In this configuration, in order to function similarly to the ac voltage acquisition unit 310B, the collector resistor Rcco may be provided instead of the emitter resistor Reo of the ac voltage acquisition unit 310B, and the collector output may be output as the ac voltage signal Vac.

Although not shown and described, the connection direction of the diodes of the input-side circuits of the ac voltage acquisition unit 310B and the relay voltage acquisition units 320Ba and 320Bb may be set to be opposite to the direction shown in fig. 4. In this case, the phases of the pulse signals of the AC voltage signal Vac, the relay terminal voltage signals Va and Vb, and the comparison signals DSa and DSb shown in fig. 5 to 7 are the same except that the phases are shifted by half a cycle from the AC voltage AC.

C. The third embodiment:

fig. 9 is a schematic configuration diagram of a control device 10C including a relay failure detection circuit 300C according to a third embodiment. A control device 10C according to a third embodiment is the same as the control device 10B according to the second embodiment, except that the relay failure detection circuit 300B of the control device 10B (see fig. 4) according to the second embodiment is replaced with the relay failure detection circuit 300C. In the control device 10C of the third embodiment, the same reference numerals as those used in the first and second embodiments are assigned to the same or similar components, and the same description thereof is omitted.

The relay failure detection circuit 300C includes an ac voltage acquisition unit 310M (see fig. 8) and relay voltage acquisition units 320Ca and 320Cb in place of the ac voltage acquisition unit 310B and the relay voltage acquisition units 320Ba and 320Bb (see fig. 4), and omits the comparison units 330Ba and 330 Bb.

The relay voltage acquisition units 320Ca and 320Cb are different from the relay voltage acquisition units 320Ba and 320Bb only in that the collector sides of the phototransistors PTa and PTb on the output circuit side of the photocouplers PCa and PCb are connected to the ac voltage signal Vac output from the ac voltage acquisition unit 310M, not to the dc voltage Vc 2.

Fig. 10 is an explanatory diagram showing a digital ac voltage signal Vac, digital relay inter-terminal voltage signals Va and Vb, and comparison signals DSa and DSb in the relay failure detection circuit 300C.

As described above, in the relay voltage acquisition units 320Ca and 320Cb, the collector sides of the phototransistors PTa and PTb are connected to the ac voltage signal Vac output from the ac voltage acquisition unit 310M, not to the dc voltage Vc 2. Since the relay voltage acquisition units 320Ca and 320Cb can detect the voltage between the relay terminals when the ac voltage signal Vac is at the H (high) level, the relay terminal-to-terminal voltage signals Va and Vb are signals corresponding to the comparison signals DSa and DSb (see fig. 5 to 7) in the second embodiment. That is, the relay voltage acquisition units 320Ca and 320Cb have the functions of the relay voltage acquisition units 320Ba and 320Bb and the comparison units 330Ba and 330Bb (see fig. 4).

Therefore, in the relay failure detection circuit 300C according to the third embodiment as well, similarly to the first and second embodiments, when the power switches SRa and SRb are in the on state and the relays RLa and RLb are set to the on state, the short-circuit failure of the relays RLa and RLb can be determined by comparing the waveform of the digital ac voltage signal Vac with the waveforms of the digital relay inter-terminal voltage signals Va and Vb. In the relay failure detection circuit 300C according to the third embodiment, even when one of the pair of double relays RLa and RLb is determined to be short-circuited, the other power switch cannot be closed, so that the other relay can be kept open, and the supply of electric power from the power supply circuit 100 to the motor 20 can be cut off.

In the relay failure detection circuit 300C according to the third embodiment, as in the relay failure detection circuit 300B according to the second embodiment, only when the detection permission switches SDa and SDb are in the closed state, the relay voltage acquisition units 320Ca and 320Cb can be set from the non-operating state to the operating state, and the voltage between the terminals of the relays RLa and RLb can be detected to determine the short-circuit failure of the relays. For example, by making the relay voltage acquisition units 320Ca and 320Cb operable only during the determination permission period set by the determination permission signal DE, the load applied to the relay voltage acquisition units 320Ca and 320Cb can be reduced, and power saving of the relay failure detection circuit can be achieved.

In the relay failure detection circuit 300C according to the third embodiment as well, similarly to the relay failure detection circuit 300C according to the second embodiment, it is possible to suppress a decrease in the comparison accuracy due to fluctuations included in the simulated voltage waveform, which are generated when comparing the simulated voltage waveforms as in the first embodiment, and a decrease in the comparison accuracy according to a low value of the resolution, and to perform a highly accurate comparison, thereby enabling highly accurate failure detection.

Further, since the ac voltage acquisition unit 310M and the relay voltage acquisition units 320Ca and 320Cb insulate the input circuit side and the output circuit side using photocouplers, the circuit configurations thereof can be reduced in size.

D. Fourth embodiment:

fig. 11 is a schematic configuration diagram of a robot 500 according to a fourth embodiment. The robot 500 includes a robot main body 501 and a control device 502 that controls driving of the robot main body 501. A computer 503 capable of communicating with the control device 502 is connected to the control device 502. The control device 502 and the computer 503 can communicate by wire or wirelessly. The communication may be performed via a network such as the internet.

The robot 500 is a robot that performs operations such as feeding, removing, transporting, and assembling of precision equipment and elements constituting the precision equipment, for example. However, the use of the robot 500 is not particularly limited. The robot main body 501 of the present embodiment is a six-axis robot, and as shown in fig. 11, includes a base 611 fixed to a floor or a ceiling, and an arm 612 coupled to the base 611.

The arm 612 includes a first arm 621, a second arm 622, a third arm 623, a fourth arm 624, a fifth arm 625, and a sixth arm 626. The first arm 621 is rotatably connected to the base 611 about a first axis O1. The second arm portion 622 is rotatably connected to the first arm portion 621 about a second axis O2. The third arm portion 623 is rotatably connected to the second arm portion 622 about a third axis O3. The fourth arm portion 624 is rotatably coupled to the third arm portion 623 about a fourth axis O4. The fifth arm 625 is rotatably connected to the fourth arm 624 about a fifth axis O5. The sixth arm portion 626 is rotatably connected to the fifth arm portion 625 about a sixth axis O6. Further, the hand 614 corresponding to the work to be executed by the robot main body 501 is attached to the sixth arm 626.

The robot main body 501 includes a first drive unit 651, a second drive unit 652, a third drive unit 653, a fourth drive unit 654, a fifth drive unit 655, and a sixth drive unit 656. The first driving part 651 rotates the first arm 621 with respect to the base 611. The second driving portion 652 rotates the second arm portion 622 with respect to the first arm portion 621. The third driving portion 653 rotates the third arm portion 623 with respect to the second arm portion 622. The fourth driving portion 654 rotates the fourth arm portion 624 with respect to the third arm portion 623. The fifth driving part 655 rotates the fifth arm 625 with respect to the fourth arm 624. The sixth driving portion 656 rotates the sixth arm portion 626 with respect to the fifth arm portion 625. The first to sixth driving units 651 to 656 each have a motor as a power source. The first to sixth driving units 651 to 656 are independently controlled by the control device 502. The control device 502 is provided with a drive circuit for controlling the drive of the motors of the first to sixth drive units 651 to 656, and a control unit for controlling the drive circuit.

The robot main body 501 is not limited to the configuration of the present embodiment, and the number of arms included in the arm 612 may be 1 to 5, or 7 or more, for example. For example, the robot main body 501 may be a horizontal articulated robot or a two-arm robot having two arms 612.

The control device 502 receives a command from the computer 503, and independently controls the driving of the first to sixth driving units 651 to 656 so that the arm portions 621 to 626 and the hand 614 are positioned in accordance with the command. Any of the control devices 10 to 10C of the above embodiments is applied to the control device 502.

In the fourth embodiment, since the control device including the relay failure detection circuit according to the above-described embodiment is mounted, it is possible to determine a short-circuit failure of the relay and cut off the supply of electric power to the motor while suppressing a decrease in the life of the relay of the power supply circuit that supplies electric power to the motor that is a power source of the robot.

In the fourth embodiment, the description has been given taking the example in which the control device 502 is provided outside the robot main body 501, but the control device 502 may be provided inside the robot main body 501. Further, a power supply circuit, a motor drive circuit, a relay failure detection circuit, and a part of the control unit included in the control device 502 may be provided inside the robot main body 501.

E. Other embodiments are as follows:

(1) in the above-described embodiment, as the comparison signals DSa and DSb indicating the comparison result between the ac voltage signal Vac corresponding to the first voltage signal and the relay inter-terminal voltage signals Va and Vb corresponding to the second voltage signal, the pulse signal is output when the relay inter-terminal voltage signals Va and Vb match the ac voltage signal Vac, and the fixed signal is output when the relay inter-terminal voltage signals Va and Vb do not match the ac voltage signal Vac. However, conversely, the relay terminal-to-terminal voltage signals Va and Vb may be configured to output a fixed signal when they match the ac voltage signal Vac, or may be configured to output a pulse signal when they do not match.

(2) In the above embodiment, the description has been given of an example in which the ac voltage acquisition unit 310B and the relay voltage acquisition units 320Ba, 320Bb, 320Ca, and 320Cb respectively insulate the input-side circuit that acquires the target voltage and the output-side circuit that outputs the acquired voltage as a voltage signal by the photocoupler. However, the present invention is not limited to this, and may be configured without insulation. The non-insulated structure is not particularly limited as long as it can obtain a target voltage and output the obtained voltage as a voltage signal, and various circuits can be applied.

(3) In the control device of the above embodiment, when a power failure occurs while driving the motor as a power source, it is preferable to store various data applied for various controls by the control unit or the like in order to prevent the data from disappearing. Therefore, the power supply circuit preferably includes a power failure determination unit that monitors whether or not the AC voltage AC is input. The power failure determination unit may determine the occurrence of a power failure when the input of the ac voltage does not reach a predetermined time period, using the ac voltage signal Vac output from the ac voltage acquisition units 310, 310B, and 310M of the above-described embodiments. In this way, since a part of the power failure determination unit can be shared with the ac voltage acquisition unit, the size of the apparatus can be reduced.

(4) In the above embodiment, a pair of relays RLa and RLb are provided in a double configuration, and a short-circuit fault of each relay is determined. However, it may be configured to have one relay and determine a short-circuit failure of the relay.

(5) In the above-described embodiment, a description has been given of an example of a relay failure detection circuit that determines a short-circuit failure of a relay mounted on a power supply circuit of a control device that controls driving of a motor as a power source. However, the present invention is not limited to this, and can be applied to a relay failure detection circuit that determines a short-circuit failure of a relay of various power supply circuits to which ac power is input.

F. Other modes are as follows:

the present disclosure is not limited to the above-described embodiments, and can be implemented in various configurations without departing from the scope of the present disclosure. For example, technical features of embodiments corresponding to technical features of the respective embodiments described below may be appropriately replaced or combined in order to solve part or all of the above problems or to achieve part or all of the above effects. Note that, if this feature is not described as an essential feature in the present specification, it can be appropriately deleted.

(1) According to a first aspect of the present disclosure, a relay fault detection circuit is provided. The relay failure detection circuit is characterized by comprising: a first voltage acquisition unit that acquires an alternating voltage input to the power supply circuit and outputs the alternating voltage as a first voltage signal; a second voltage acquisition unit that acquires an inter-terminal voltage of a relay provided in the power supply circuit and outputs the inter-terminal voltage as a second voltage signal; a comparison unit that compares a waveform of the first voltage signal with a waveform of the second voltage signal; and a determination unit that determines whether or not the relay has failed, based on a result of the comparison of the waveforms.

According to the relay failure detection circuit of this aspect, the number of times of switching on/off of the relay can be suppressed, and a failure of a short circuit of the relay can be determined.

(2) In the above aspect, the determination unit may determine that the relay has failed when a difference between a waveform of the first voltage signal and a waveform of the second voltage signal is equal to or greater than a predetermined threshold value.

According to this aspect, it is possible to determine a failure of the relay in the state of the relay set to the on state.

(3) In the above aspect, the first voltage acquisition unit and the second voltage acquisition unit may each have a digital conversion circuit using a photocoupler, and the first voltage signal may be a digital signal indicating a change in the ac voltage and the second voltage signal may be a digital signal indicating a change in the voltage between the terminals of the relay.

According to this aspect, the first voltage signal and the second voltage signal can be compared with high accuracy, and thus, a fault can be detected with high accuracy. Further, since the input-side circuit for acquiring the voltage and the output-side circuit for outputting the voltage signal are insulated from each other by using the photocoupler, the first voltage acquisition unit and the second voltage acquisition unit can be downsized.

(4) In the above aspect, the comparison unit may compare the waveforms when an excitation switch that supplies power to a coil of the relay is in an on state.

According to this aspect, the failure of the relay can be determined without switching the relay.

(5) In the above aspect, the first voltage signal may be used in a power failure determination unit of the power supply circuit to determine occurrence of a stop of input of the ac voltage.

According to this aspect, since a part of the power failure determination unit can be shared with the ac voltage acquisition unit, the size of the apparatus can be reduced.

(6) In the above aspect, the comparison unit may compare the waveforms when a predetermined time has elapsed, and the determination unit may determine whether or not the relay has failed.

According to this aspect, power saving of the device including the relay failure detection circuit can be achieved as compared with the case where determination is always performed.

(7) In the above aspect, the second voltage acquisition unit may include a switch that switches whether or not to acquire the inter-terminal voltage, and the switch may be turned off to output the second voltage signal when it is determined whether or not the relay has failed.

According to this aspect, the load on the second voltage acquisition unit can be reduced, power saving of the relay failure detection circuit can be achieved, and power saving of the device can be achieved.

(8) In the above aspect, the relays may be provided in a double manner in the power supply circuit, the second voltage acquisition unit and the comparison unit may be provided for each of the double relays, the determination unit may determine whether or not each of the relays has failed based on a result of comparison of the waveforms, and when it is determined that one of the double relays has failed, the other of the double relays may be set to the on state.

According to this aspect, even when it is determined that a failure has occurred in one of the double-layered relays, the power output from the power supply circuit can be cut off by turning on the other relay.

(9) According to a second aspect of the present disclosure, a robot is provided. The robot is characterized by comprising: a motor as a power source; a power supply circuit that supplies electric power for driving the motor; and the relay failure detection circuit in the first aspect.

According to this aspect, it is possible to determine a failure of the relay and cut off the supply of electric power to the motor while suppressing a decrease in the life of the relay of the power supply circuit that supplies electric power to the motor that is the power source of the robot.