Robot

A robot includes a first power supply that outputs first voltage, a first circuit that operates with the first voltage, a second power supply that outputs second voltage, a second circuit that operates with the second voltage, and a first protection section that causes the first circuit to operate based on the second voltage when the first power supply stops outputting the first voltage.

BACKGROUND

1. Technical Field

The present invention relates to a robot.

2. Related Art

In a circuit of related art for driving a robot, there is a known technology for duplicating a variety of circuits for improvement in failure resistance and other purposes. For example, JP-A-2006-116679 discloses a power supply board including a plurality of auxiliary power supply circuits.

Employing the configuration in which a plurality of auxiliary power supply circuits are simply provided, as in the technology of related art described above, undesirably increases the size of the power supply board and complicates the circuit configuration.

SUMMARY

An advantage of some aspects of the invention is to improve the failure resistance of a power supply by using a simple configuration.

A robot according to an aspect of the invention includes a first power supply that outputs first voltage, a first circuit that operates with the first voltage, a second power supply that outputs second voltage, a second circuit that operates with the second voltage, and a first protection section that causes the first circuit to operate based on the second voltage when the first power supply stops outputting the first voltage.

That is, in the robot including two types of power supply that output two types of voltage, the first power supply and the second power supply, and using the two types of voltage to cause a circuit as a component to operate, when one of the two types of power supply stops outputting voltage, the circuit having operated with the terminated voltage is caused to operate based on the voltage from the other one of the two types of power supply. Therefore, provided that each of the first and second power supplies is provided with no auxiliary power supply circuit, even when at least one of the two types of power supply stops outputting voltage due, for example, to failure, the circuit having operated with the voltage from the one of the two types of power supply can be caused to operate with the other one of the two types of power supply. The second power supply, which is inevitably necessary to cause the second circuit to operate, can also be used to cause the first circuit to operate. Failure resistance of a power supply can thus be improved by using a simple configuration.

The first power supply only needs to output the first voltage, and the first circuit only needs to be a circuit that operates with the first voltage. That is, in a configuration in which at least part of the first circuit operates with the first voltage, the first power supply only needs to be a power supply that causes the first circuit to operate. For example, in a conceivable configuration, the first power supply receives electric power supplied, for example, from a commercial power supply provided at the location where the robot is installed and includes a voltage conversion circuit that converts the voltage outputted from the commercial power supply into the first voltage. Of course, the first power supply may be capable of outputting a plurality of types of voltage (voltages having different voltage values, standards, frequencies, and other parameters, AC voltage, and DC voltage) including the first voltage, and the plurality of types of voltage may be considered as the first voltage. Further, the first protection section may protect a circuit that operates with part or entirety of the plurality of types of voltage outputted from the first power supply.

The first circuit only needs to be a circuit that forms part of the robot, and any of a variety of circuits can be the first circuit. It is, however, noted that the first circuit includes a circuit to be protected by the first protection section. Therefore, the first circuit preferably includes a circuit having high necessity to keep operating even when the first power supply stops outputting the first voltage or a circuit in which instantaneous stoppage thereof possibly induces greater failure.

The second power supply only needs to output the second voltage, and the second circuit only needs to be a circuit that operates with the second voltage. That is, in a configuration in which at least part of the second circuit operates with the second voltage, the second power supply only needs to be a power supply that causes the second circuit to operate. For example, in a conceivable configuration, the second power supply receives electric power supplied, for example, from a commercial power supply provided at the location where the robot is installed and includes a voltage conversion circuit that converts the voltage outputted from the commercial power supply into the second voltage. The second power supply may, of course, be capable of outputting a plurality of types of voltage (voltages having different voltage values, standards, frequencies, and other parameters, AC voltage, and DC voltage) including the second voltage.

The second voltage may or may not be equal to the first voltage. That is, as long as the two types of power supply are configured to cause the first and second circuits to operate, respectively, the value of the voltage outputted from each of the two types of power supply is not particularly limited to a specific value. A second protection section that causes the second circuit to operate based on the first voltage when the second power supply stops outputting the second voltage may further be provided.

The second circuit only needs to be a circuit that forms part of the robot. The first and second circuits may be formed on the same substrate or may be formed on different substrates. In the latter case, for example, in a conceivable configuration, circuits for achieving different types of function are formed on different substrates or in different enclosures. As the different types of function, for example, in a conceivable configuration, the first circuit achieves a function of directly sending and receiving electric power and signals to and from motors and other components of the robot, and the second circuit achieves a function of providing the first circuit with an instruction for controlling the action of the robot.

The first protection section only needs to be capable of causing the first circuit to operate based on the second voltage when the first power supply stops outputting the first voltage. That is, when the first circuit encounters a state in which it cannot operate based on the first voltage from the first power supply, the first protection section only needs to cause the first circuit to operate by using the second voltage. To protect the first circuit by using the second voltage, the first circuit may be so configured that it operates with the received second voltage, or the first circuit may instead be so configured that it produces the first voltage from the second voltage and receives the produced first voltage for operation.

In the latter case, for example, in an employable configuration, the first protection section includes a conversion section that converts the second voltage into the first voltage, and when the first power supply stops outputting the first voltage, the first protection section causes the first circuit to operate by using the first voltage produced by the conversion performed by the conversion section. According to the configuration described above, providing a voltage conversion circuit that converts the second voltage into the first voltage allows formation of a circuit for protecting the first circuit based on the second voltage, whereby failure resistance of a power supply can be improved by using an extremely simple configuration. The voltage value of the first voltage produced by the conversion performed by the conversion section is not required to be exactly equal to the first voltage, and the voltage value may vary within a range that allows the first circuit to operate.

A variety of configurations can be employed as the configuration in which in normal operation, the first circuit is provided with the first voltage from the first power supply, and when the first power supply stops outputting the first voltage, the voltage source is switched from the first power supply to the second power supply. For example, the first circuit may be so formed that each of the first voltage from the first power supply and the first voltage produced from the second power supply is supplied to the first circuit via a diode and the former first voltage is set to be slightly greater than the latter first voltage. According to the configuration described above, when the first power supply can output the first voltage, the first power supply outputs the first voltage to the first circuit, whereas when the first power supply stops outputting the first voltage, the first voltage produced by the conversion of the second voltage (voltage slightly smaller than first voltage) is provided to the first circuit.

Further, the following configuration may be employed: Stoppage of the output of the first voltage from the first power supply is detectable, and when the stoppage is detected, the first circuit is caused to operate based on the second voltage from the second power supply. In a conceivable configuration as the configuration described above, for example, the voltage outputted from the first power supply is detected, and when the output voltage becomes a voltage that can be considered to differ from the first voltage, an IC switches a switch in the first protection circuit in such a way that the first circuit is caused to operate based on the second voltage outputted from the second power supply.

Further, the stoppage of the output of the first voltage from the first power supply may be a trigger for causing the first circuit to operate based on the second voltage, and a cause of the stoppage may be failure of the first power supply, such as failure of a circuit in the first power supply or a broken wire in the circuit, or may be stoppage of electric power supply to the first power supply, such as power cut, or may be stoppage of the first power supply because a protection circuit functions due, for example, to generated heat. To protect the first circuit even when the commercial power supply or any other power supply stops supplying the second power supply with electric power due to power cut, the second circuit may include a battery. That is, employing a configuration in which the second voltage is outputted based on electric power from the battery when external electric power supply to the second power supply is stopped due, for example, to power cut allows the first circuit to operate based on the second voltage.

The stoppage of the output of the first voltage from the first power supply is a situation in which the output from the first power supply is not normally supplied to the first circuit and includes, for example, a case where the output voltage value becomes smaller or greater than the first voltage by at least a predetermined value. A case where an element other than the voltage value, for example, the frequency becomes a value that does not fall within a predetermined range may, of course, be considered as the state in which the first power supply stops outputting the first voltage.

Further, since the first circuit is configured to reliably operate even when the output of the first voltage is stopped, the first circuit is preferably a circuit that should avoid instantaneous stoppage of operation thereof. As an example of a configuration in which the first circuit is such a circuit, the first circuit includes an error recording section that carries out processes of acquiring an error having occurred in a component of the robot and recording the error in a nonvolatile memory.

That is, in the course of driving operation of the robot, an error that makes it difficult to cause the robot to act could occur, for example, when a component of the robot performs action beyond a predetermined limit (for example, when a drive unit acts to a position beyond a predetermined limit) or when a component of the robot enters a state beyond a predetermined limit (for example, when overcurrent or overvoltage occurs or when heat beyond a predetermined limit is generated). In such a case, it is necessary, after an error occurs, to analysis a cause of the error for prevention of reoccurrence and other purposes. To this end, employing a configuration in which the first circuit acquires an error having occurred in a component of the robot and records the error in a nonvolatile memory and analyzing an error log recorded in the nonvolatile memory allow analysis of the cause of the error.

In the configuration described above, in a state in which the robot is forced to stop being driven due to occurrence of an error, when the first power supply stops supplying the first voltage to the first circuit before the error (information representing error) is recorded in the nonvolatile memory, the error is not recorded and hence a cause of the error cannot be analyzed. To avoid the situation, in a case where the configuration in which the first circuit acquires an error and records the error in the nonvolatile memory is employed, reconfiguring the configuration in such a way that the first circuit is caused to operate based on the second voltage when the output of the first voltage is stopped allows handling a case where the robot is forced to stop being driven due to occurrence of an error in such a way that at least a cause of the error can be analyzed.

An error can be defined in a variety of aspects. For example, in an employable configuration, an ID is given to each component of the robot, it is considered that an error has occurred when a component of the robot performs action beyond a predetermined limit or enters a state beyond a predetermined limit, and the ID representing the component in which the error has occurred is acquired as an error. Of course, in a case where a plurality of causes of errors are conceivable in a single component, an ID may be given for each cause of an error, and when an error occurs, the ID representing a cause of the error may be acquired as an error.

A variety of configurations can be employed as a configuration for detecting occurrence of an error. For example, in an employable configuration, it is detected that an error has occurred when a sensor that detects the position, acceleration, or any other parameter of a drive unit of the robot, a sensor that detects voltage, current, temperature, or any other parameter, or any other component outputs a value beyond a predetermined limit. It is, of course, considered that when any of a variety of protection circuits functions, an error has occurred in a component to be protected.

A variety of elements are conceivable as a component of the robot, and every element that forms the robot can be a component from which an error is acquired. Therefore, a circuit that is part of the first circuit (circuit other than circuit that acquires and records error) may be the component, a circuit that forms the first power supply may be the component, or the second power supply or the second circuit may be the component. When the first power supply as a circuit for supplying the first circuit with the first voltage is a component of the robot as an error monitored subject, and even when the first power supply stops outputting the first voltage due, for example, to an error, such as failure, the error recording section can keep operating based on the second voltage, whereby post-analysis of the occurrence of the error in the first power supply can be performed.

The nonvolatile memory may or may not be incorporated in the first circuit. In the latter case, for example, the nonvolatile memory may be connected to the second circuit, the first circuit may output information representing an acquired error to the second circuit, and the second circuit may acquire the information representing the error and records the information in the nonvolatile memory. In the configuration described above, when the output of the first voltage is stopped, the first circuit only needs to operate for a period required at least to acquire information representing an error and output the information to the second circuit. To this end, since the first circuit only needs to operate for a very short period, the first protection section can be simply configured.

Further, the approach of the aspect of the invention described above, in which when one of the two types of power supply stops outputting electric power, the other one of the two types of power supply supplies electric power, is applicable as a method. Further, the robot to which the invention is applied may be provided in the form of a robot system including a control unit or any other component that controls the robot and cooperates with a variety of apparatus, and such a robot system can employ a variety of other configurations.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

An embodiment of the invention will be described in the following order.

(1) Configuration of robot

(2) Configuration for improving failure resistance of first power supply

(2-1) Configuration of first protection section

(3) Other embodiments

(1) Configuration of Robot

FIG. 1Ais a block diagram showing the configuration of a robot10, which is an embodiment of the invention. The robot10according to the present embodiment includes a first power supply21, a second power supply22, a controller23, a control computer24, and a drive unit30. The drive unit30includes a plurality of movable sections driven with a plurality of motors. InFIG. 1A, the movable sections are formed of an end effector connected to the front end of an arm and joints (rotary supports) of the arm. In the present embodiment, the drive unit30includes a camera for capturing an image of a workpiece or any other object and an LED display, not shown, for displaying an alarm or any other message at the time of failure.

The first power supply21includes a circuit that produces electric power to be supplied to the controller23and the drive unit30by using electric power from a commercial power supply40having a predetermined standard (such as predetermined voltage and frequency). That is, the first power supply21includes a circuit that is connected to the commercial power supply40, acquires predetermined AC electric power from the commercial power supply, and produces electric power having three types of voltage (three-phase 280-V AC power, 24-V DC power, and 8-V DC power). The three-phase 280-V AC power produced by the first power supply21is provided via a power line to a motor that is not shown but is accommodated in the drive unit30. The 24-V DC power and the 8-V DC power produced by the first power supply21are provided to the controller23via power lines.

The controller23includes firmware (firmware23b, which will be described later) that controls the action of the drive unit30and a control section (display control section23a, which will be described later) circuit that controls the LED display provided in the drive unit30. That is, the controller23is connected to the control computer24via a communication line, and the firmware acquires an action instruction from the control computer24and identifies control signals for causing the joints, the end effector, and the camera to operate in accordance with the action instruction. The firmware then outputs the identified control signals to the components to be controlled.

For example, when the firmware has acquired an action instruction that causes a joint of the drive unit30to rotate, the firmware identifies a rotation angle and other parameters of a motor that are necessary for the rotation of the joint and identifies a control signal that causes the shaft of the motor to rotate by the rotation angle (signal that causes switching device to perform PWM control). The firmware then outputs the identified control signal to an inverter (power conversion section21d, which will be described later) in the first power supply21. As a result, the first power supply21outputs three-phase AC power for rotating the joint in accordance with the action instruction, and the motor in the shaft of the drive unit30is rotated to rotate the joint.

When the firmware has acquired an action instruction that instructs acquisition of an image captured with the camera in the drive unit30, the firmware outputs a control signal to the camera to cause it to output image information. As a result, the firmware acquires the image information and transmits the image information to the control computer24via a communication line.

Further, the controller23is connected to the LED display in the drive unit30via a 24-V power line and a communication line, and the display control section, which controls the LED display, outputs a control signal to the LED display to cause it to display an image (such as alarm image at the time of failure). As a result, the LED display displays the image.

The second power supply22includes a circuit that produces electric power to be supplied to the control computer24by using the electric power from the commercial power supply40. That is, the second power supply22includes a circuit that is connected to the commercial power supply40, acquires predetermined AC power from the commercial power supply, and produces electric power of a plurality of kinds of voltage by using an electric power conversion section including a converter and an inverter. The control computer24in the present embodiment is formed of general-purpose components, and a program execution circuit formed of a CPU, a RAM, a ROM, and other components is formed on a substrate (mother board) that complies with a predetermined standard. The second power supply22is therefore also a power supply configured to output DC voltages of 12 V, 5 V, and 3.3 V, which comply with the predetermined standard, that is, a power supply that complies with the ATX standard.

The control computer24, which includes the program execution circuit, can execute an arbitrary program created in advance and recorded in a nonvolatile memory. In the present embodiment, the program includes a drive control program for controlling the action of the drive unit30. That is, when the control computer24executes the drive control program, the control computer24issues an action instruction that instructs the firmware in the controller23to cause the drive unit30to act. For example, the control computer24issues an action instruction to the firmware to cause it to acquire information on an image captured with the camera. As a result, the firmware controls the camera to acquire the image information and transmits the image information to the control computer24.

The control computer24then analyzes the image information to identify an intended position and angle of each section (joints and end effector) of the drive unit30. The control computer24then outputs an action instruction for each section to the firmware. As a result, the firmware drives each section of the drive unit30based on the action instruction. As described above, in the present embodiment, the controller23and the control computer24cooperate with each other to cause the drive unit30to perform a predetermined task. The control computer24may include other components, for example, an input section that accepts a user's input and an output section that outputs image information, voice information, and other types of information to the user.

(2) Configuration for Improving Failure Resistance of First Power Supply

In the configuration described above, the firmware further functions as an error recording section that acquires an error having occurred in a component of the robot10and records the error in a nonvolatile memory. That is, in the present embodiment, when at least part of the components of the robot10performs action that does not fall within a predetermined range, it is determined that an error has occurred, and information representing that an error has occurred is recorded.

Specifically, monitored subjects under monitoring whether or not an error has occurred are determined in advance, and a sensor for detecting that an error has occurred is connected to each of the monitored subjects and outputs a result of detection that is acquired by the firmware.FIG. 1Bis a block diagram showing key portions of the first power supply21, the controller23, and the control computer24, the second power supply22, and the drive unit30. InFIG. 1B, the solid lines represent power lines, and the broken lines represent signal lines.

The first power supply21includes an electric power conversion section21d, in which a converter and an inverter produce the 280-V AC power based on the output from the commercial power supply40, an electric power conversion section21e, in which a converter produces the 24-V DC power based on the output from the commercial power supply40, and an electric power conversion section21f, in which a converter produces the 8-V DC power based on the output from the commercial power supply40. The 280-V AC power is electric power that causes the motors in the drive unit30to operate. The 24-V DC power is electric power that causes the display control section23ain the controller23to operate. The 8-V DC power is electric power that causes the firmware23bin the controller23to operate. To the electric power conversion sections21d,21e, and21fare connected protection circuits21a,21b, and21c, which monitor current, voltage, and heat in the circuits in the electric power conversion sections21d,21e, and21fand stop the functions of the circuits when overcurrent or overvoltage occurs or when heat beyond a predetermined limit is generated. Each of the protection circuits21a,21b, and21ccan be formed of a variety of known circuits.

Each of the protection circuits21a,21b, and21cis connected to the firmware23bvia a signal line. Each of the protection circuits21a,21b, and21cis provided with a register that changes a value thereof when the protection circuit performs the function of stopping the corresponding one of the electric power conversion sections21d,21e, and21f, and the resister is provided for each cause of the stoppage (such as overcurrent, overvoltage, and generation of heat beyond a predetermine limit). The firmware23bcan therefore detect that an error has occurred and identify a cause of the occurrence of the error based on the values of the registers in the protection circuits21a,21b, and21c. That is, when the firmware23bdetects that an error has occurred based on the values of the registers in the protection circuits21a,21b, and21c, the firmware23bdetermines that an error has occurred in the electric power conversion sections21d,21e, and21fconnected to the protection circuits21a,21b, and21cand identifies a cause of the occurrence of the error. That is, the electric power conversion sections21d,21e, and21fare monitored subjects to be monitored by the firmware23bvia the protection circuits21a,21b, and21cin terms of presence and absence of an error and a cause of the occurrence of the error.

In the present embodiment, other monitored subjects are also monitored by the same configuration in terms of presence and absence of an error and a cause of the occurrence of the error. For example, to each of the motors provided in the drive unit30is attached a sensor for determining whether or not the action of the motor is beyond a predetermined limit. The sensor is provided with a register that changes a value thereof when the action is beyond the predetermined limit, and the resister is provided for each cause of occurrence of an error. The firmware23bcan therefore detect presence and absence of an error and identify a cause of the occurrence of the error in each of the monitored subjects based on the value of the register for the monitored subject.

The firmware23bcommunicates with the control computer24on a regular basis. In the communication, the firmware23boutputs a flag representing whether or not an error has occurred for each of the monitored subjects and for each cause of the occurrence of the error to the control computer24. The control computer24includes a nonvolatile memory24aand records the flag representing whether or not an error has occurred for each of the monitored subjects and for each cause of the occurrence of the error in the nonvolatile memory24a. Therefore, in the present embodiment, when an error has occurred in a component of the robot10, referring to the information recorded in the nonvolatile memory24aallows identification of the location where the error has occurred and a cause of the occurrence of the error.

In the configuration described above, the firmware23bacquires information representing a monitored subject in which an error has occurred and a cause of the occurrence of the error. On the other hand, the 8-V DC power that causes the firmware23bto operate is produced by the electric power conversion section21f. Therefore, when failure has occurred in a portion associated with the electric power conversion section21f, and if no measure is taken against the failure, the firmware23bcould undesirably stop operating before information representing the error is acquired (or before the information is recorded in the nonvolatile memory24a). Further, when failure has occurred in a portion that is not associated with the electric power conversion section21fand failure has occurred in a portion that is associated with the electric power conversion section21f, the firmware23bcould undesirably stop operating before information representing the error having occurred in the portion that is not associated with the electric power conversion section21fis acquired (or before the information is recorded in the nonvolatile memory24a).

To avoid the situation described above, in the present embodiment, the controller23includes a first protection section23c, which allows, even when failure has occurred in a portion associated with the electric power conversion section21f, appropriate recording of information representing the error. The first protection section23cincludes a circuit that causes the firmware23bto operate based on the 12-V voltage outputted from the second power supply22when the electric power conversion section21fstops outputting the 8-V voltage. That is, in the present embodiment, the firmware23bforms the first circuit, the control computer24forms the second circuit, the first voltage is 8 V, and the second voltage is 12 V.

(2-1) Configuration of First Protection Section

FIG. 2Ais a block diagram showing the configuration of the first protection section23c. The first protection section23cincludes diodes D1and D2and a DC-DC converter23c1, as shown inFIG. 2A. The diode D1is located in a power line that connects the electric power conversion section21fto the firmware23band interposed between the electric power conversion section21fand the firmware23bwith the electric power conversion section21fconnected to the anode of the diode D1and the firmware23bconnected to the cathode thereof. The diode D1is therefore so connected to the power line that the direction from the electric power conversion section21fto the firmware23bcoincides with the forward direction of the diode D1.

The DC-DC converter23c1includes a circuit that converts the 12-V DC power into DC power having a voltage value slightly smaller than 8 V (7.5 V in the example shown inFIG. 2A). The DC-DC converter23c1is connected to the control computer24and the anode of the diode D2. In the present embodiment, the 12-V DC power is supplied from the second power supply22to the control computer24, and the DC power is supplied from the control computer24to the first protection section23c(seeFIG. 1B). The DC-DC converter23c1converts the 12-V DC power into 7.5-V DC power and supplies the diode D2with the converted DC power. The cathode of the diode D2is connected to the power line to which the cathode of the diode D1is connected. The diode D2is therefore so connected to the power line that the direction from the DC-DC converter23c1to the firmware23bcoincides with the forward direction of the diode D2.

In the thus configured first protection section23c, when the first power supply21and the second power supply22function normally, the 8V-DC power and the 7.5V-DC power that are forwardly biased are applied to the diodes D1and D2, respectively. As a result, when the first power supply21and the second power supply22function normally, the potential at the cathode of the diode D1is higher than the potential at the cathode of the diode D2, and the potential at the cathode of the diode D1forms the voltage outputted from the first protection section23c. Therefore, in this case, the 8-V DC power is supplied to the firmware23band causes the firmware23bto operate.

On the other hand, when failure occurs in the electric power conversion section21fin the first power supply and the electric power conversion section21fstops outputting electric power, the potential at the anode of the diode D1is not 8 V any more. In this case, when the second power supply22functions normally, the 12-V DC power is supplied to the DC-DC converter23c1via the control computer24, and 7.5 V is therefore applied to the anode of the diode D2. As a result, the diode D2is forwardly biased and the diode D1is reversely biased, and the potential at the cathode of the diode D2forms the voltage outputted from the first protection section23c. Therefore, in this case, the 7.5-V DC power is supplied to the firmware23b. Since 7.5 V is a voltage value slightly smaller than 8 V, the firmware23boperates also with the 7.5-V DC power.

The potential at the cathode of the diode D2is normally lower than the potential at the cathode of the diode D1, and when the electric power conversion section21fstops outputting electric power, the DC-DC converter23c1only needs to output voltage that allows the firmware23bto operate based on the potential at the cathode of the diode D2. The voltage slightly smaller than 8 V is therefore not limited to 7.5 V as long as the voltage falls within the range that allows the firmware to operate.

As described above, when failure has occurred in the electric power conversion section21f, the protection circuit21cfunctions to cause the electric power conversion section21fto stop outputting electric power, and in this state, the register in the protection circuit21cshows a value corresponding to a cause of the occurrence of the error, and the value shows that an error has occurred. Since the function of the first protection section23cdoes not cause the firmware23bto stop operating but allows the firmware23bto operate normally, the firmware23bcan detect that an error has occurred in the electric power conversion section21fand identify a cause of the occurrence of the error based on the register in the protection circuit21c. The firmware23bthen outputs information representing that the error has occurred and the cause of the occurrence of the error to the control computer24and records the information in the nonvolatile memory24a. Therefore, after the failure has occurred, a user can identify the location where the error has occurred and a cause of the occurrence of the error by referring to the information recorded in the nonvolatile memory24a, whereby the user can perform repair or otherwise handle the failure.

In the state in which there is a circuit that functions as a sensor for error detection (such as protection circuit21cdescribed above), a variety of configurations can be employed as the configuration for keeping electric power supply (for example, keeping supply of electric power to register) even when failure occurs. For example, a configuration in which the voltage outputted from the first protection section23callows the protection circuit21cto operate allows electric power supply to the protection circuit21cto be maintained even when failure occurs in the electric power conversion section21f. Instead, a circuit that functions as a sensor for error detection may be configured to receive electric power from a circuit that is not a subject detected by the sensor circuit. For example, an employable configuration is a configuration in which the protection circuit21cin the electric power conversion section21freceives electric power from the electric power conversion section21d, the electric power conversion section21e, or the second power supply22, any of which is a circuit other than the electric power conversion section21f. In this case, when the voltage outputted from a circuit other than the electric power conversion section21fdiffers from the voltage that causes the protection circuit21cto operate, the former voltage value may, of course, be converted, for example, with a converter.

The sensor may, of course, be so configured that it is provided with no special circuit for maintaining the electric power supply in order to acquire error information. For example, in the configuration described above, a register that holds information representing that the protection circuit21cor any other circuit has functioned (error has occurred) may be formed in the firmware23b. According to the configuration described above, which ensures that the first protection section23callows electric power supply to the firmware23bto be maintained, even when failure has occurred in the electric power conversion section21for any other component and the electric power conversion section21fhas stopped outputting electric power, information representing that the error has occurred can be held.

(3) Other Embodiments

The embodiment described above is an example for implementing the invention, and a variety of other embodiments can be employed as long as when one of two types of power supply stops outputting electric power, the other supplies electric power. For example, the robot10does not necessarily have the aspect shown inFIG. 1Aand may instead be a double-arm robot, a humanoid robot, a scalar robot, or any other robot.

Further, the firmware23bforms the first circuit in the embodiment described above, and any of the variety of other elements that form the robot10can be the first circuit. For example, when the voltage outputted from the electric power conversion section21eor21fis considered as the first voltage, the drive unit30or the display control section23acan be the first circuit. In this case, the first protection section produces the 280-V AC power or the 24-V DC power based on the voltage outputted from the second power supply22at the time of failure, and the produced power allows the first circuit to operate. The former configuration, in which the electric power required for the drive unit30is not interrupted even instantaneously at the time of failure, can prevent the drive unit30from being damaged. The latter configuration, in which the LED display can display an alarm at the time of failure, can quickly notify a user of occurrence of failure and the location where the failure has occurred. The alarm issuing device may, of course, be a buzzer or any other sound output device. Further, a plurality of circuits in the firmware23b, the display control section23a, and the drive unit30may instead be the first circuit. Moreover, assuming that the first power supply21and the second power supply22are swapped with each other, the control computer24may function as the first circuit.

Further, a configuration that suppresses an abrupt change in the output from the first power supply at the time of failure may be provided. For example, a capacitor that is charged in normal operation or a choke coil that suppresses an abrupt change in current may suppress an abrupt change in the output from the first power supply when the first power supply stops outputting electric power.

Further, when the first power supply stops outputting the first voltage, the first protection section may cause the first circuit to operate based on the second voltage, and a process of terminating the action of the robot10may be carried out at the same time. That is, the robot10is so configured that when some type of failure has occurred, the action of the robot10is automatically terminated because it is not appropriate to allow the robot10keep operating. Specifically, the control computer24or the controller23controls the drive unit30to cause it to gradually stop operating so that no breakage due to abrupt stoppage of action of the arm or any other portion occurs. For example, the firmware23boutputs a control signal to the electric power conversion section21dto cause it to control the three-phase AC power in such a way that the motors gradually stop the joints of the robot10(the joints stop without exerting excessive load on reduction gears). When failure has occurred in the electric power conversion section21d, the three-phase AC power cannot be outputted in some cases. In such cases, for example, a large-capacitance capacitor may be provided in the electric power conversion section21d, and the capacitor may supply electric power to rotate the shafts of the motors in such a way that the joints of the robot10gradually stop.

Further, the first protection section23cis not necessarily configured as shown inFIG. 2Adescribed above. For example, an IC that detects whether or not failure has occurred may be provided, and the IC may switch the source of the first voltage from one to the other.FIG. 2Bshows an example of the configuration of the first protection section. InFIG. 2B, a first protection section230cis employed in replace of the first protection section23cshown inFIG. 1B, and the components other than the first protection section230care the same as those shown inFIG. 1B. Further, inFIG. 2B, the same components as those inFIGS. 2A and 1Bhave the same reference characters (it is, however, noted that the DC-DC converter23c1outputs a voltage of 8 V).

The first protection section230cincludes transistors Tr1, Tr2, the DC-DC converter23c1, and a control IC23c2, as shown inFIG. 2B. The transistor Tr1is located in a power line that connects the electric power conversion section21fto the firmware23band interposed between the electric power conversion section21fand the firmware23b. The transistor Tr1is controlled by the control IC23c2. That is, the control IC23c2can switch a state in which conduction is established between the electric power conversion section21fand the firmware23bto a state in which no conduction is established therebetween and vice versa.

The transistor Tr2is located in a power line that connects the DC-DC converter23c1to the firmware23band interposed between the DC-DC converter23c1and the firmware23b. The transistor Tr2is also controlled by the control IC23c2. That is, the control IC23c2can switch a state in which conduction is established between the DC-DC converter23c1and the firmware23bto a state in which no conduction is established therebetween and vice versa.

In a normal state (no failure has occurred in electric power conversion section21f), the control IC23c2controls the transistors Tr1and Tr2to turn on the transistor Tr1and turn off the transistor Tr2. As a result, in the normal state, conduction between the electric power conversion section21fand the firmware23bis established, but no conduction between the DC-DC converter23c1and the firmware23bis established. That is, 8 V produced by the electric power conversion section21fis applied to the firmware23b.

Further, the control IC23c2is connected to the protection circuit21c, and when the register in the protection circuit21cshows that an error has occurred, the control IC23c2detects, based on the value of the register, that the electric power conversion section21fhas stopped outputting electric power. In this case, the control IC23c2further controls the transistors Tr1and Tr2to turn off the transistor Tr1and turn on the transistor Tr2. As a result, no conduction is established between the electric power conversion section21fand the firmware23b, but conduction is established between the DC-DC converter23c1and the firmware23b. That is, 8 V produced by the DC-DC converter23c1is applied to the firmware23b.

According to the configuration described above, when the first power supply21stops outputting the 8-V DC power, the firmware23bis allowed to operate based on the 12-V DC power outputted from the second power supply22.FIG. 2Bshows an example in which the control IC23c2operates with electric power supplied from the electric power conversion section21e, which is a power supply other than the electric power conversion section21f. Electric power from any other power supply, for example, the 5-V DC power from the second power supply22may, of course, be supplied to the control IC23c2.

Further, a configuration in which the control computer24is so protected that it does not stop operating when failure occurs in the second power supply22may be employed. Moreover, the first or second power supply may include an auxiliary power supply.FIG. 2Cshows a configuration in which a second protection section24c, which causes the second circuit to operate based on the first voltage when the second power supply stops outputting the second voltage as in the configuration shown inFIG. 1B, is provided and a battery as an auxiliary power supply is connected to the second power supply. InFIG. 2C, the same components as those inFIG. 1Bhave the same reference characters.

Specifically, a control computer240as the second circuit is provided with the second protection section24c. The second protection section24cincludes a circuit that converts the 24-V voltage outputted from the first power supply21into 12-V voltage when a second power supply220stops outputting 12-V voltage. As a specific configuration of the circuit, the circuit configuration shown inFIG. 2A or 2Bcan be employed. An employable configuration is, for example, as follows: The second protection section24csupplies the anode of the diode D1with the 12-V DC power derived from the second power supply220, converts the 24-V DC power derived from the first power supply21via the controller23into 12-V DC power, and supplies the anode of the diode D2with the 12-V DC power; and one of the voltages outputted from the cathodes of the diodes D1and D2is used in a circuit in the control computer24(circuit that operates with 12-V DC power). According to the configuration, even when the second power supply220stops supplying the 12-V DC power, the control computer24is allowed to keep operating.

Further, a battery25is connected to the second power supply220, and when external power supply to the second power supply220(power supply from commercial power supply40) is stopped, the second power supply220can receive electric power supply from the battery25and operate normally. Therefore, 12-V, 5-V, and 3.3-V DC-power, among which the 12-V DC power corresponds to the 12-V DC voltage as the second voltage, can be produced and supplied to the control computer240. Therefore, even when power cut or any other failure occurs and the external power supply is stopped, the control computer240operates normally. In this case, the control computer240may, of course, carry out a process of stopping the robot10while the electric power is left in the batter25.

When power cut or any other failure occurs and the external power supply is stopped, the first power supply21stops outputting electric power. In this case, the first protection section23creceives electric power of 12 V as the second voltage supplied from the second power supply220and causes the firmware23bto operate. As a result, the firmware23bcarries out processes of acquiring information representing a monitored subject where an error has occurred and a cause of the occurrence of the error and recording the information in the nonvolatile memory24a. A user can therefore analyze the monitored subject where the error has occurred and the cause of the occurrence of the error. The circuit caused to operate by the first protection section23cmay, of course, include a circuit other than the firmware23b, and employing a configuration in which the first protection section23ccauses the display control section23aand the drive unit30to operate allows the robot10to keep acting normally even when power cut or any other failure occurs and the external power supply is stopped. Therefore, before the external power supply is restored, the battery25is used to cause the robot10to act, and after the external power supply is restored, the electric power supply from the battery25is stopped and switched to the external power supply, whereby the robot10having high failure resistance can be provided.

Further, in the configuration described above, error information acquired at the time of failure contains information representing a cause of occurrence of the error, and the information may further contain other types of information, such as information representing the state of action of a component of the robot10(such as angle and position of joint).

Further, the portions where the first protection section23cand the second protection section24care formed are not limited to the controller23and the control computer24described above and may be other portions, for example, the first power supply21and the second power supply, or at least one of the first protection section23cand the second protection section24cmay be formed on an independent substrate and incorporated in the robot10.

The entire disclosure of Japanese Patent Application No. 2014-215124, filed Oct. 22, 2014 is expressly incorporated by reference herein.