Brake control device, brake control method, and brake control program

Abstract

The present invention provides a brake control device capable of reliably checking for switch faults, even in the case of de-excitation. This brake control device is for a brake that is released by applying a current to a brake coil, the brake control device comprising: a voltage control unit capable of selecting between, and outputting, a first voltage of a first potential for driving the brake coil and a second voltage of a second potential lower than the first potential; and a plurality of switches which are connected in series to the brake coil and which control the energization of the brake coil. In the case of de-excitation, a continuity fault detection unit controls the voltage control unit to switch the output voltage from the second voltage to the first voltage immediately before outputting a test pulse.

Description

Brake control device, brake control method, and brake control program

[0001] The present disclosure relates to a brake control device, a brake control method, and a brake control program.

[0002] Conventionally, for example, servo motors (motors) that control each axis of a machine tool or robot are provided with electromagnetic brakes (brakes). These brakes are used, for example, to shorten the fall distance of the motor in an emergency stop, or to maintain the posture of the machine tool or robot by preventing the axis from moving due to gravity during an emergency stop of the motor or when the power is off.

[0003] The brake is released by passing current through the brake coil, and safety is generally ensured by cutting off the current to the brake coil using two or more switches connected in series to the brake coil.

[0004] Here, semiconductor elements (semiconductor circuits) such as bipolar transistors, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), IGBTs (Insulated Gate Bipolar Transistors), and SiC (Silicon Carbide)-MOSFETs are used as switches in the brake control devices that control the brakes in order to provide durability and to control the brakes with high precision.

[0005] In recent years, in brake control devices that use semiconductor circuits, a test pulse that interrupts conduction to a switch for a short period of time has been input to check whether a short circuit (failure) has occurred in the switch when the brake is released.

[0006] Furthermore, a technique called de-excitation is also known, which reduces current consumption (power consumption) and heat generation while maintaining the brake release state by passing current through the brake coil to release the brake and then reducing the voltage applied to the brake coil.

[0007] Conventionally, various proposals have been made as brake control techniques for controlling the brake of a motor using a semiconductor circuit.

[0008] JP 2015-211609 A JP 2008-131759 A

[0009] In a brake control device using a semiconductor circuit as described above, it is conceivable to test for a fault by inputting a test pulse to the switch in a de-excited state (de-excited state) that reduces current consumption and heat generation.

[0010] However, during de-excitation, the voltage applied to the brake coil decreases, so if a test pulse that interrupts conduction for a short period of time is input to the switch, the brake may change from a released state to a locked state, which could affect the operation of the machine.

[0011] Therefore, there is a demand for a brake control device, a brake control method, and a brake control program that can reliably check for switch failure even when the switch is de-excited.

[0012] According to one embodiment of the present disclosure, there is provided a brake control device for a brake that is released by passing a current through a brake coil, the brake control device including: a voltage control unit that can select and output a first voltage of a first potential that drives the brake coil and a second voltage of a second potential that is lower than the first potential; and a plurality of switches connected in series to the brake coil and controlling energization of the brake coil. A conduction fault detection unit controls the voltage control unit to switch the output voltage from the second voltage to the first voltage immediately before outputting a test pulse during de-excitation.

[0013] FIG. 1 is a diagram schematically illustrating an example of a robot system to which the brake control device according to the present embodiment is applied. FIG. 2 is a circuit block diagram illustrating an example of the brake control device according to the present embodiment. FIG. 3 is a waveform diagram illustrating the operation of an example of a conventional brake control device. FIG. 4 is a waveform diagram illustrating de-excitation performed in conventional brake control. FIG. 5 is a waveform diagram illustrating a problem with de-excitation in a conventional brake control device. FIG. 6 is a waveform diagram illustrating an example of the operation of an example of the brake control device according to the present embodiment. FIG. 7 is a waveform diagram illustrating another example of the operation of an example of the brake control device according to the present embodiment. FIG. 8 is a circuit block diagram illustrating an application example of the brake control device according to the present embodiment. FIG. 9 is a diagram illustrating the relationship between a motor, a brake, and a drive shaft to which the brake control device according to the present embodiment is applied.

[0014] Hereinafter, examples of a brake control device, a brake control method, and a brake control program according to the present embodiment will be described in detail with reference to the accompanying drawings. In each drawing, the same or similar components are assigned the same or similar reference numerals. Furthermore, the embodiments described below do not limit the technical scope and meaning of the terms of the invention described in the claims.

[0015] 1 is a diagram schematically illustrating an example of a robot system to which a brake control device according to this embodiment is applied, and shows an example of an industrial robot system. As shown in FIG. 1, the industrial robot system, to which a brake control device 3 according to this embodiment is applied, includes an industrial robot (robot) 1 and a robot control device 2.

[0016] The robot 1 is placed on a base 15, and a hand unit (end effector) 11A is provided at the tip of its arm 11. A robot control device 2 controls the robot 1, for example, based on a pre-installed program (software program) or the outputs of various sensors. That is, the robot control device 2 outputs commands to the robot 1 to control the hand unit 11A provided at the tip of the arm 11, and causes the robot 1 to perform a predetermined process on a workpiece (object) 5 placed on a workbench 4, for example.

[0017] 1, the brake control device 3 is built into the robot control device 2, but it can also be arranged outside the robot control device 2 as a separate unit, or can be attached to the robot control device 2 via a connector or the like. For example, it is also possible to add the brake control device 3 according to this embodiment to a conventional robot control device 2 as an optional function.

[0018] The robot 1 is not limited to an industrial robot, but may be various robots such as a collaborative robot, or may be various machines such as a computerized numerical control (CNC) device. In other words, the brake control device 3 according to this embodiment can be widely applied to various machines having, for example, a motor (electric motor) with an electromagnetic brake.

[0019] 2 is a circuit block diagram showing an example of a brake control device according to this embodiment. As shown in FIG. 2, the brake control device 3 controls an electromagnetic brake (brake coil BC) provided on a motor (M), and releases the brake by passing a current through the brake coil BC. Here, the motor may be, for example, a motor that drives each axis of an industrial robot 1 or a CNC device, or a motor that drives an end effector 11A or various tools.

[0020] The brake control device 3 includes a first switch element Q1 and a second switch element Q2 arranged in series with the brake coil BC, a conduction fault detection unit 31, a voltage control unit 32, a first processing circuit MC1 and a second processing circuit MC2, and a diode D0 arranged in parallel with the brake coil BC.

[0021] 2, the first and second switch elements Q1 and Q2 are each an NPN bipolar transistor, but various other semiconductor elements such as a MOSFET, an IGBT, or a SiC-MOSFET can also be used. Furthermore, the polarity of the semiconductor elements used can be changed depending on the levels of control signals SW1 and SW2 input to the bases (gates, control terminals) of the switch elements Q1 and Q2. In other words, the brakes can be released when both switch elements Q1 and Q2 are turned on and the output voltage Vb of the voltage control unit 32 is applied across the brake coil BC.

[0022] The voltage control unit 32 is capable of selecting and outputting a normal brake voltage (a voltage of a first potential (first voltage): for example, 90 V or 24 V) or a low brake voltage (a voltage of a second potential (second voltage) lower than the first potential: for example, 35 V or 12 V, which is half the normal brake voltage) as the brake voltage Vb that drives the brake coil BC. Note that the second voltage being approximately half the value of the first voltage is merely an example, and can be changed in various ways depending on the motor, system, etc. to which it is applied. Here, the voltage control unit 32 can be configured, for example, as a power supply having a tap for the normal brake voltage and a tap for the low brake voltage, and selects and outputs one of the voltages (first voltage or second voltage) based on the output of the conduction fault detection unit 31.

[0023] Furthermore, when a switching power supply is used as the voltage control unit 32, the first voltage or the second voltage is selected and output by controlling the pulse width of PWM (pulse width modulation) or the pulse frequency of PFM (pulse frequency modulation) based on the output of the conduction fault detection unit 31. Furthermore, the voltage control unit 32 may be configured to receive the first voltage and the second voltage generated externally, and select and output the first voltage or the second voltage based on the output of the conduction fault detection unit 31.

[0024] The conduction fault detection unit 31 outputs first and second control signals SW1 and SW2 to the first and second switch elements Q1 and Q2 to control the switching of the respective switch elements Q1 and Q2. In the brake control device according to this embodiment, the conduction fault detection unit 31 inputs (inserts) test pulses into the first and second control signals SW1 and SW2 in a de-excitation state (de-excitation) described below, and compares the test pulses with the first and second feedback signals FB1 and FB2 to correctly test for faults in the first and second switch elements Q1 and Q2. The test pulses have a pulse width corresponding to the very short time during which the brake release state is maintained even if the first and second switch elements Q1 and Q2 are turned off when the voltage driving the brake coil BC is the normal brake voltage (first voltage).

[0025] In the brake control device of this embodiment, the conduction fault detection unit 31 controls the output voltage (brake voltage Vb) of the voltage control unit 32 to switch from the second voltage (low brake voltage) for de-excitation to the first voltage (normal brake voltage) immediately before outputting a test pulse (inputting a test pulse to the control signals SW1 and SW2) during de-excitation. This enables reliable detection of switch failures during de-excitation without causing erroneous brake application. Note that the diode D0 may be a bidirectional TVS (Transient Voltage Suppressor) diode, which is used to absorb surge voltages that occur, for example, when a test pulse is input to temporarily shut off the first and second switch elements Q1 and Q2. In addition, while two switches (first and second switch elements Q1 and Q2) are connected in series with the brake coil BC in FIG. 2 , this is for safety reasons; however, more switches (three or more) may be connected in series.

[0026] Before describing in detail the operation of one example of the brake control device according to this embodiment, a problem with de-excitation in a conventional brake control device will be described with reference to Figures 3 to 5. Figure 3 is a waveform diagram for explaining the operation of one example of a conventional brake control device, showing waveforms when there is no fault in the first and second switch elements Q1, Q2. Note that the brake control device described with reference to Figure 2 is substantially the same as a conventional brake control device, except for the functions of, for example, the conduction fault detection unit 31 and the voltage control unit 32.

[0027] 3, when the brake is released to operate the motor, the first and second control signals SW1 and SW2 are raised to high level "H" at brake release timing Pbr, turning on both the first and second switch elements Q1 and Q2. This causes the output voltage Vb of the voltage control unit 32 to be applied across the brake coil BC, releasing the brake and allowing the motor (M) to operate. With the motor in this operating state, test pulses can be input to the first and second control signals SW1 and SW2 and compared with the first and second feedback signals FB1 and FB2 to check for faults in the first and second switch elements Q1 and Q2.

[0028] That is, the conventional conduction fault detection unit 31 inputs a test pulse that interrupts (low level "L") the first and second control signals SW1 and SW2 for a very short time, receives the first and second feedback signals FB1 and FB2 via the first and second processing circuits MC1 and MC2, and compares them with the test pulse, thereby detecting a conduction fault in the first and second switch elements Q1 and Q2 (for example, a state in which the first and second switch elements Q1 and Q2 are always on regardless of the levels of the control signals SW1 and SW2). Needless to say, it is also possible to detect a state in which the first and second switch elements Q1 and Q2 are always off regardless of the levels of the control signals SW1 and SW2.

[0029] The test pulse of the first control signal SW1 and the test pulse of the second control signal SW2 are alternately timed so that the test pulses of the first and second control signals SW1, SW2 can be compared with the first and second feedback signals FB1, FB2. Note that the test pulse has a pulse width corresponding to the very short time during which the brake release state is maintained even if the first and second switch elements Q1, Q2 are turned off when the voltage driving the brake coil BC is the normal brake voltage.

[0030] Specifically, while the first and second control signals SW1 and SW2 are both at a high level "H," a test pulse that goes to a low level "L" for a short period of time is input and compared with the first and second feedback signals FB1 and FB2. As shown in FIG. 3 , if there is no conduction fault in the first switch element Q1, the first feedback signal FB1 rises at the timing when the test pulse of the first control signal SW1 falls. Similarly, if there is no conduction fault in the second switch element Q2, the second feedback signal FB2 falls at the timing when the test pulse of the second control signal SW2 falls. This makes it possible to detect conduction faults in the first and second switch elements Q1 and Q2 while maintaining the brake release state.

[0031] 4 is a waveform diagram illustrating de-excitation performed in conventional brake control. A known technique, called de-excitation, reduces current consumption and heat generation while maintaining the brake release state by lowering the voltage applied to the brake coil after current has flowed through the brake coil to release the brake. Specifically, as shown in FIG. 4 , the first and second switch elements Q1 and Q2 are turned on at brake release timing Pbr to apply a normal brake voltage (first voltage: e.g., 90 V or 24 V) across the brake coil BC to release the brake. Then, a low brake voltage (second voltage: e.g., 35 V or 12 V) is applied from de-excitation start timing Pdxs to maintain the brake release state in order to reduce current consumption and heat generation.

[0032] However, in the de-excitation described with reference to FIG. 4, if a fault check is performed on the first and second switch elements Q1, Q2 in the brake release state described with reference to FIG. 3, the brake release state may not be maintained, and a problem (mis-engagement) may occur.

[0033] 5 is a waveform diagram illustrating the problem of de-excitation in a conventional brake control device. In FIG. 5, the horizontal axis represents the brake release timing Pbr and the de-excitation start timing Pdxs, and the vertical axis represents the change over time in the brake voltage Vb applied to the brake coil BC and the brake current Ib flowing through the brake coil BC.

[0034] As shown in Fig. 5, during the period from the brake release timing Pbr to the de-excitation start timing Pdxs, the brake voltage Vb applied to the brake coil BC is the normal brake voltage (first voltage), so the brake current Ib does not decrease significantly and the brake release state is maintained. That is, as described with reference to Fig. 3, in the brake release state, it is possible to perform a fault check on the first and second switch elements Q1, Q2.

[0035] In contrast, during the period after the de-excitation start timing Pdxs, the brake voltage Vb applied to the brake coil BC drops to, for example, a voltage (second voltage) that is about half the normal brake voltage, so when a test pulse is input, the brake current Ib flowing through the brake coil BC drops and the brake release state cannot be maintained. In other words, during de-excitation, the brake voltage Vb applied to the brake coil BC drops, so when a test pulse that interrupts conduction for a very short time is input to the switch, the brake current Ib flowing through the brake coil BC falls below the value that maintains the brake release state (see dashed line area ER), causing a brake lock state and potentially affecting the operation of the machine (machine tool or robot).

[0036] Next, the operation of one example of the brake control device according to this embodiment will be described with reference to Figures 6 and 7. Figure 6 is a waveform diagram for explaining one example of the operation of the brake control device according to this embodiment. Note that the brake control device according to this embodiment can be the brake control device 3 described with reference to Figure 2, but is not limited to this.

[0037] 2 , in one example of the brake control device according to this embodiment, the conduction fault detection unit 31 controls the output voltage (brake voltage Vb) of the voltage control unit 32 to switch from a second voltage (low brake voltage) for deexcitation to a first voltage (normal brake voltage) immediately before outputting a test pulse during deexcitation. Here, the timing at which the brake voltage Vb is switched (returned) from the low brake voltage (second voltage) to the normal voltage (first voltage) immediately before the test pulse can vary depending on the specifications of the applied motor M and the machine tool or robot in which the motor is used, but, for example, it is preferably set a time longer than the width of the test pulse (a very short time) before the timing at which the test pulse is output, and for example, it is preferably set a time several times (for example, about 3 to 4 times) longer than the very short time.

[0038] 6 with the above-mentioned FIG. 5, during de-excitation, the brake voltage Vb applied to the brake coil BC is switched from the second voltage to the first voltage immediately before the test pulse is input, so that the brake current Ib flowing through the brake coil BC due to the test pulse does not fall below the value for maintaining the brake released state, and the brake released state is maintained. In this way, according to the brake control device of the first embodiment, it is possible to reliably check for switch failure even during de-excitation.

[0039] Fig. 7 is a waveform diagram illustrating another example of operation of an embodiment of the brake control device according to the present embodiment. As is apparent from a comparison of Fig. 7 with the above-described Fig. 6, in this other example of operation of the embodiment of the brake control device shown in Fig. 7, the conduction fault detection unit 31 controls the voltage control unit 32 by setting the timing at which the output voltage (brake voltage Vb) of the voltage control unit 32 is returned from the first voltage to the second voltage after outputting the test pulse during de-excitation to a time that is shorter than the time from when the output voltage is switched from the second voltage to the first voltage until the test pulse is output.

[0040] Here, it is preferable that the conduction fault detection unit 31 controls the voltage control unit 32 by setting the timing at which the output voltage Vb is returned from the first voltage to the second voltage after the test pulse is output, to a very short time after the test pulse is output. It goes without saying that the timing at which the output voltage Vb is returned from the first voltage to the second voltage after the test pulse is output can be changed and modified in various ways depending on the characteristics of the semiconductor elements of the switches Q1 and Q2 used, the configuration of the voltage control unit 32, or the characteristics and parasitic capacitance of the brake (brake coil MC) of the motor M used.

[0041] Fig. 8 is a circuit block diagram for explaining an application example of the brake control device according to this embodiment, and shows how eight brakes (brake coils BC1 to BC8) are controlled by the brake control device 3 shown in Fig. 2. Here, the eight brake coils BC1 to BC8 are, for example, six brakes provided on the motors that drive the axes of the six-axis industrial robot 1, and two brakes provided on the motor that drives the hand unit 11A.

[0042] The number of brake coils (brakes) controlled by the brake control device 3 is not limited to eight, and various changes and modifications are possible for the configurations of the switching elements Q1, Q2, the processing circuits MC1, MC2, etc. Furthermore, the brake control device 3 according to this embodiment can be implemented as a brake control method that, for example, controls the output voltage of the voltage control unit 32 to switch from a second voltage (low brake voltage) for de-excitation to a first voltage (normal brake voltage) immediately before outputting a test pulse during de-excitation, or controls the output voltage of the voltage control unit 32 to return from the first voltage to the second voltage after (immediately after) outputting a test pulse.

[0043] That is, one example of a brake control method according to this embodiment is a brake control method for a brake that is released by passing a current through the brake coil BC, and provides a first voltage having a first potential for driving the brake coil BC and a second voltage having a second potential lower than the first potential. Furthermore, in this example of a brake control method according to this embodiment, when de-excitation is performed using the second voltage for driving the brake coil BC, a test pulse is output that briefly interrupts each of multiple switches Q1, Q2 that are connected in series with the brake coil BC and control the conduction of the brake coil BC, and a conduction fault in each of the switches Q1, Q2 is detected. Furthermore, in this example of a brake control method according to this embodiment, the voltage for driving the brake coil BC is switched from the second voltage to the first voltage immediately before the test pulse is output.

[0044] Here, the test pulse has a pulse width corresponding to the minute time during which the brake is released even if the switches Q1 and Q2 are turned off when the voltage driving the brake coil BC is the first voltage. Furthermore, it is preferable to detect a conduction fault in the switches Q1 and Q2 by setting the timing at which the output voltage is switched from the second voltage to the first voltage immediately before the test pulse is output during de-excitation to be longer than the minute time before the test pulse is output.

[0045] Furthermore, the brake control method according to this embodiment can also be implemented as a brake control program executed by, for example, a microprocessor (MPU) that functions as the arithmetic processing unit of the conduction fault detection unit 31 or the robot control device 2. For example, by installing the brake control method according to this embodiment in a conventional brake control device having the functions described above with reference to Figures 3 and 4, i.e., a conventional brake control device having the problem described above with reference to Figure 5, and having the arithmetic processing unit execute the method, it becomes possible to reliably check for switch failure even during de-excitation. Here, the brake control program may be provided by being recorded on a computer-readable non-transitory recording medium or non-volatile semiconductor memory, or may be provided via a wired or wireless communication line.

[0046] Note that examples of computer-readable non-transitory recording media include optical disks such as CD-ROMs (Compact Disc Read Only Memory) and DVD-ROMs, and hard disk drives. Non-volatile semiconductor memories include PROMs (Programmable Read Only Memory) and flash memories. Furthermore, distribution from a server device can be via a wired or wireless LAN (Local Area Network) or a WAN (Wide Area Network) such as the Internet.

[0047] 9A and 9B are diagrams illustrating the relationship between a motor, a brake (brake coil), and a drive shaft to which the brake control device according to this embodiment is applied. Fig. 9A shows an example in which one shaft DS0 is driven by one motor M0 having two brakes (two brake coils BC1 and BC2), and Fig. 9B shows an example in which one shaft DS0 is driven by two motors M1 and M2, each having one brake BC1 and BC2.

[0048] As shown in FIG. 9(a), motor M0 is provided with two brake coils BC1 and BC2, and both of these brake coils BC1 and BC2 are controlled by brake control device 3. As a result, axis DS0 is driven by one motor torque from one motor M0, but stopping control is performed by two brake coils BC1 and BC2 (dual brake). As shown in FIG. 9(b), motor M1 is provided with one brake coil BC1, and motor M2 is provided with one brake coil BC2, and axis DS0 is driven by axes ds1 and ds2 of these two motors M1 and M2. As a result, axis DS0 is driven by two motor torques, and stopping control is performed by two brake coils BC1 and BC2 (dual brake) provided on motors M1 and M2.

[0049] 9(a) and 9(b) are merely examples, and the brake control device 3 according to this embodiment can be widely applied to machines such as machine tools and robots having various configurations of motors, brakes, and drive shafts. Furthermore, the brake control device, brake control method, and brake control program according to this embodiment make it possible to reliably inspect switch failures in machines having various configurations even during de-excitation.

[0050] Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments.

[0051] The following supplementary notes are further disclosed regarding the above embodiment and modified examples. [Supplementary Note 1] A brake control device (3) for a brake that is released by passing a current through brake coils (BC, BC1 to BC8), comprising: a voltage control unit (32) capable of selectively outputting a first voltage of a first potential for driving the brake coils (BC, BC1 to BC8) and a second voltage of a second potential lower than the first potential, a plurality of switches (Q1, Q2) connected in series to the brake coils (BC, BC1 to BC8) and controlling the energization of the brake coils (BC, BC1 to BC8), and a conduction fault detection unit (31) that outputs a test pulse for interrupting each of the plurality of switches (Q1, Q2) for a very short time when de-excitation is performed using the output voltage from the voltage control unit (32) as the second voltage, and detects a conduction fault in each of the switches (Q1, Q2). The brake control device according to claim 1, wherein the conduction fault detection unit (31) controls the voltage control unit (32) to switch the output voltage from the second voltage to the first voltage immediately before outputting the test pulse during the de-excitation. [Supplementary Note 2] The brake control device according to Supplementary Note 1, wherein the test pulse has a pulse width corresponding to the very short time during which the brake is maintained in a released state even when the switches (Q1, Q2) are cut off when the voltage driving the brake coils (BC, BC1 to BC8) is the first voltage. [Supplementary Note 3] The brake control device according to Supplementary Note 1 or Supplementary Note 2, wherein the plurality of switches include a first switch element (Q1) provided between one end of the brake coils (BC, BC1 to BC8) and one end of an output of the voltage control unit (32), and a second switch element (Q2) provided between the other end of the brake coils (BC, BC1 to BC8) and the other end of the output of the voltage control unit (32), and the conduction fault detection unit (31) alternately outputs the test pulse to the first switch element (Q1) and the test pulse to the second switch element (Q2).[Supplementary Note 4] The brake control device according to any one of Supplementary Notes 1 to 3, wherein the conduction fault detection unit (31) controls the voltage control unit (32) by setting, in the deexcitation, a timing at which the output voltage is switched from the second voltage to the first voltage immediately before outputting the test pulse to a time earlier than the minute time period from the time at which the test pulse is output. [Supplementary Note 5] The brake control device according to any one of Supplementary Notes 1 to 4, wherein the conduction fault detection unit (31) controls the voltage control unit (32) by setting, in the deexcitation, a timing at which the output voltage is returned from the first voltage to the second voltage after outputting the test pulse to a time later than a time period from the time at which the output voltage is switched from the second voltage to the first voltage to the time at which the test pulse is output. [Supplementary Note 6] The brake control device according to Supplementary Note 5, wherein the conduction fault detection unit (31) controls the voltage control unit (32) by setting the timing at which the output voltage is returned from the first voltage to the second voltage after outputting the test pulse, to the very short time after outputting the test pulse, in the de-excitation. [Supplementary Note 7] A brake control method for a brake that is released by passing a current through a brake coil (BC, BC1 to BC8), comprising: preparing a first voltage of a first potential that drives the brake coil (BC, BC1 to BC8), and a second voltage of a second potential that is lower than the first potential; when de-excitation is performed using the voltage that drives the brake coil (BC, BC1 to BC8) as the second voltage, outputting a test pulse that interrupts, for a very short time, each of a plurality of switches (Q1, Q2) that are connected in series to the brake coils (BC, BC1 to BC8) and control the current flow through the brake coils (BC, BC1 to BC8); detecting a conduction fault in each of the switches (Q1, Q2); and switching the voltage that drives the brake coils (BC, BC1 to BC8) from the second voltage to the first voltage immediately before outputting the test pulse.[Supplementary Note 8] A brake control program for brakes that are released by passing a current through brake coils (BC, BC1 to BC8), the brake control program causing a calculation processing device to execute the following steps: preparing a first voltage of a first potential that drives the brake coils (BC, BC1 to BC8) and a second voltage of a second potential that is lower than the first potential; when de-excitation is performed using the voltage that drives the brake coils (BC, BC1 to BC8) as the second voltage, outputting a test pulse that interrupts, for a very short time, each of a plurality of switches (Q1, Q2) that are connected in series to the brake coils (BC, BC1 to BC8) and control current flow through the brake coils (BC, BC1 to BC8), thereby detecting a conduction fault in each of the switches (Q1, Q2); and switching the voltage that drives the brake coils (BC, BC1 to BC8) from the second voltage to the first voltage immediately before outputting the test pulse.

[0052] 1 Industrial robot (robot) 2 Robot control device 3 Brake control device 4 Work table 5 Work (object) 11 Arm 11A Hand unit (end effector) 15 Base 31 Conduction fault detection unit 32 Voltage control unit BC, BC1 to BC8 Brake coil D0 Diode (bidirectional TVS diode) FB1, FB2 Feedback signal M0, M1, M2 Motor MC1, MC2 Processing circuit Q1, Q2 Switch (switch element) SW1, SW2 Control signal

Claims

1. A brake control device for a brake that is released by passing a current through a brake coil, comprising: a voltage control unit that can select and output a first voltage of a first potential that drives the brake coil, and a second voltage of a second potential that is lower than the first potential; a plurality of switches that are connected in series to the brake coil and control the flow of current to the brake coil; and a conduction fault detection unit that outputs a test pulse that shuts off each of the plurality of switches for a very short time when de-excitation is performed, with the output voltage from the voltage control unit being the second voltage, and detects a conduction fault in each of the switches, wherein the conduction fault detection unit controls the voltage control unit to switch the output voltage from the second voltage to the first voltage when de-excitation is performed, just before outputting the test pulse.

2. A brake control device according to claim 1, wherein the test pulse has a pulse width corresponding to the very short time during which the brake is maintained in a released state even when the switch is turned off when the voltage driving the brake coil is the first voltage.

3. A brake control device as claimed in claim 1 or claim 2, wherein the plurality of switches include a first switch element provided between one end of the brake coil and one end of the output of the voltage control unit, and a second switch element provided between the other end of the brake coil and the other end of the output of the voltage control unit, and the conduction fault detection unit alternately outputs the test pulse to the first switch element and the test pulse to the second switch element.

4. A brake control device according to any one of claims 1 to 3, wherein the conduction fault detection unit controls the voltage control unit by setting the timing for switching the output voltage from the second voltage to the first voltage immediately before outputting the test pulse during the de-excitation to a time longer than the minute time before the timing for outputting the test pulse.

5. A brake control device according to any one of claims 1 to 4, wherein the conduction fault detection unit controls the voltage control unit by setting the timing at which the output voltage is returned from the first voltage to the second voltage after the test pulse is output during the de-excitation to a time that is shorter than the time from when the output voltage is switched from the second voltage to the first voltage to when the test pulse is output.

6. The brake control device according to claim 5, wherein the conduction fault detection unit controls the voltage control unit by setting the timing at which the output voltage is returned from the first voltage to the second voltage after the test pulse is output, to the very short time after the test pulse is output.

7. A brake control method for a brake that is released by passing a current through a brake coil, comprising: preparing a first voltage of a first potential that drives the brake coil; and a second voltage of a second potential that is lower than the first potential; when de-excitation is performed using the second voltage that drives the brake coil, outputting a test pulse that briefly interrupts each of a plurality of switches that are connected in series to the brake coil and control the flow of current to the brake coil; detecting a conduction fault in each of the switches; and switching the voltage that drives the brake coil from the second voltage to the first voltage immediately before outputting the test pulse.

8. A brake control program for a brake that is released by passing a current through a brake coil, the program causing a processing device to execute the following steps: preparing a first voltage of a first potential that drives the brake coil, and a second voltage of a second potential that is lower than the first potential; when de-excitation is performed using the second voltage that drives the brake coil, outputting a test pulse that interrupts, for a very short time, each of a plurality of switches that are connected in series to the brake coil and control the flow of current to the brake coil, and detecting a conduction fault in each of the switches; and switching the voltage that drives the brake coil from the second voltage to the first voltage immediately before outputting the test pulse.

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