Robot

Abstract

To provide a robot that is able to properly consume regenerative power of a motor while improving back drivability.SOLUTION: A robot 1, which includes at least one joint 4, a motor 7 that operates the joint 4, and a power supply 5 that supplies electric power for driving the motor 7, has regenerative circuits 8, 9 that receive and consume regenerative electric power generated when the motor 7 is operated by the external force. The regenerative circuits 8, 9 are configured to be switched between at least two states that are a first regeneration state and a second regeneration state different from each other in an amount of power consumption. The robot further includes: detection means 11, 12 configured to detect a voltage of the power supply 5; and regeneration state switching means configured to set the regenerative circuits 8, 9 to the first regeneration state when the detected voltage of the power supply 5 is a first predetermined value, and to set the regenerative circuits to a second regeneration state when the detected voltage of the power supply 5 is a second predetermined value larger than the first predetermined value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a robot having a dynamic brake that can apply a braking force to a motor by consuming the power generated when the motor regenerates power. [Background technology]

[0002] Patent Document 1 discloses a bipedal humanoid robot with a regenerative resistor in a motor control circuit as such a dynamic brake. In the robot described in Patent Document 1, when a predetermined operating voltage is input during normal operation or an emergency stop operation, the regenerative resistor is electrically connected to the power supply wiring that supplies drive power to the motor. As a result, the power generated by the motor's regeneration is consumed as heat by the regenerative resistor, thereby applying a braking force to the motor. Furthermore, the robot in Patent Document 1 is configured to alternately connect and disconnect the regenerative resistor to the power supply wiring when an emergency stop operation is performed. This changes the resistance value generated in the motor via the power supply wiring, thereby adjusting the braking force generated by the dynamic brake. Patent Document 1 describes this configuration as being able to reduce the braking force generated by the dynamic brake in an emergency stop operation. Therefore, even if the resistance value of the regenerative resistor is high, the robot can be stopped relatively gently during an emergency stop, thereby preventing the robot from tipping over. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-94640 Summary of the Invention [Problem to be solved by the invention]

[0004] In the robot described in Patent Document 1, during normal operation, a regenerative resistor is connected to the power supply wiring when a predetermined operating voltage is input, but the magnitude of the braking force applied to the motor by the regenerative resistor is not taken into consideration. Therefore, in the robot described in Patent Document 1, during normal operation, a braking force corresponding to the resistance of the regenerative resistor acts on the motor, regardless of the magnitude of an external force input from the outside, such as an impact. As a result, backdrivability, which is the ease with which a drive system such as a motor can operate when an external force such as an impact is applied, may be reduced. Alternatively, the regenerative resistor may not fully consume the motor's regenerative power. In this case, the relatively large amount of regenerative power that is not consumed may increase the voltage of the power supply supplying power to the motor, potentially reducing the durability of the power supply.

[0005] Furthermore, in the robot of Patent Document 1, when an emergency stop operation is performed, the braking force acting on the motor is reduced by alternately connecting and disconnecting the regenerative resistor from the power supply wiring. Therefore, it is conceivable to reduce the braking force acting on the motor by performing such control even during normal operation. However, this could increase the load on the mechanism and software that switches between connection and disconnection. Thus, there is room for improvement in improving the backdrivability of the robot when it comes into contact with surrounding objects or people, and in consuming the motor's regenerative power.

[0006] The present invention has been made in light of the above-mentioned technical problems, and aims to provide a robot that can appropriately consume the regenerative power of a motor while improving backdrivability when an external force is applied. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the present invention provides a robot comprising at least one joint, a motor for operating the joint, and a power source for supplying power to drive the motor, the robot further comprising a regenerative circuit for receiving and consuming regenerative power generated when the motor is operated by an external force, the regenerative circuit being configured to switch between at least two states, a first regenerative state and a second regenerative state, which differ in the amount of power consumed, and further comprising: detection means for detecting the voltage of the power source; and regenerative state switching means for setting the regenerative circuit to the first regenerative state when the detected voltage of the power source is a first predetermined value, and for setting the regenerative circuit to the second regenerative state when the detected voltage of the power source is a second predetermined value greater than the first predetermined value. [Effects of the Invention]

[0008] The robot of this invention is equipped with a regeneration circuit that consumes regenerative power generated when the motor is operated by an external force. The regeneration circuit is configured to switch between at least two states, a first regeneration state and a second regeneration state, which differ in the amount of power consumed. The regeneration circuit is set to the first regeneration state when the voltage of the power supply supplying power to the motor is at a first predetermined value, and the second regeneration state is set when the voltage of the power supply is at a second predetermined value greater than the first predetermined value. Therefore, even if regenerative power is generated from the motor by an external force, the regenerative circuit can consume the motor's regenerative power as heat. This makes it possible to suppress an increase in the power supply voltage and to apply a braking force to the motor to quickly stop it.

[0009] The first and second regenerative states are configured to consume different amounts of power. That is, by selectively connecting or disconnecting the first and second regenerative circuits, it is possible to set multiple regenerative states with different amounts of regenerative power consumed by the motor. As a result, when an external force is input to the robot and the motor regenerates, the braking force applied to the motor can be changed in stages.

[0010] Therefore, for example, by setting the amount of regenerative power consumption to a relatively small value when the first regenerative state is set, the braking force acting on the motor can be made relatively small. In other words, the motor stops with a relatively small deceleration, allowing the robot to stop smoothly (flexibly). On the other hand, by setting the amount of regenerative power consumption to a relatively large value when the second connected state is set, the braking force acting on the motor can be made relatively large. In other words, the motor stops with a relatively large deceleration, allowing the robot to stop quickly.

[0011] Therefore, dynamic braking can be applied in response to external forces input to the robot, improving the so-called backdrivability of the robot. Furthermore, it is possible to prevent the control load from increasing and the electrical circuit from becoming complicated. In other words, high backdrivability can be achieved with a simple configuration. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram illustrating an example of a robot according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram schematically illustrating the configuration of the robot shown in FIG. [Figure 3] 10 is a flowchart for explaining the operation of a robot when a relatively small external force is input to an arm of the robot in an embodiment of the present invention and the motor regenerates. [Figure 4] 10 is a flowchart for explaining the operation of the robot when a relatively large external force is input to the arm of the robot in the embodiment of the present invention and the motor regenerates. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described based on the embodiments shown in the drawings. Note that the embodiments described below are merely examples of specific embodiments of the present invention, and are not intended to limit the present invention.

[0014] FIG. 1 shows an example of a robot 1 equipped with a control device according to an embodiment of the present invention. The robot 1 shown in FIG. 1 is configured to be able to grasp an object or part with a gripper 3 provided at the tip of an arm 2 and transport it to a desired location, or to grasp a door handle and turn or pull it. To enable such movements, the robot 1 is provided with a plurality of joints 4 connecting a plurality of links (not shown). The plurality of joints 4 enable the tip of the arm 2 to move and rotate.

[0015] The robot 1 configured in this manner includes a power supply 5, an inverter 6, a motor 7, a first regenerative circuit 8, a second regenerative circuit 9, and a controller 10 as components for operating the multiple joints 4. The robot 1 may be a vertically articulated 4 robot 1 in which multiple links are connected in series, or a horizontally articulated 4 robot in which multiple links are connected in parallel. In other words, the robot 1 in this embodiment of the present invention may be any robot that can transmit force via the links by supplying power from the power supply 5 to the motors 7 and having the motors 7 drive the joints 4.

[0016] The power supply 5 supplies direct current as driving power for driving the motor 7. The power supply 5 is, for example, a battery such as a lithium ion battery, a lithium polymer battery, or a nickel-metal hydride battery, or a household outlet.

[0017] The inverter 6 is a power converter that converts DC power supplied from the power source 5 into AC power, and conversely, converts AC power obtained by regeneration of the motor 7 into DC power. The inverter 6 may be configured according to the structure and characteristics of the motor 7. For example, if the motor 7 is a three-phase AC motor, the inverter 6 is configured as a three-phase bridge circuit. The inverter 6 has, for example, multiple switching elements such as diodes. Power is converted between DC power and AC power by controlling the switching elements of the inverter 6 to be ON or OFF. Note that the inverter 6 may be configured to change the frequency to change the rotation speed of the motor 7 when converting to AC power.

[0018] Furthermore, the inverter 6 is not limited to the switching elements described above, and may be configured with semiconductor switching elements. For example, if the inverter 6 is a PWM (Pulse Width Modulation) inverter 6, it is configured with a bridge circuit of semiconductor switching elements and freewheeling diodes connected in parallel to the semiconductor switching elements. In this case, IGBTs, FETs, thyristors, GTOs, SiC transistors, etc. may be used as the semiconductor switching elements.

[0019] The motor 7 is a servo motor formed by a three-phase AC motor, and is configured similarly to conventionally known servo motors. The motor 7 outputs torque according to the magnitude of AC power supplied from the power supply 5 via the inverter 6. This drives the joints 4 of the robot 1 to operate the arm section 2. The motor 7 also generates power when rotated by an external force being input to the arm section 2, i.e., when regenerating.

[0020] For example, if the arm unit 2 comes into contact with a surrounding member, an external force may act to rotate the motor 7 (rotor) in the opposite direction to when torque is being output. In such a case, a back electromotive force (back electromotive voltage) corresponding to the rotation speed of the rotor (not shown) is generated from the motor 7 to the power supply 5, generating regenerative power. This regenerative power is supplied to the power supply 5 via the inverter 6. The torque output by the motor 7 drives the joints 4 via a reducer (not shown) with a relatively small gear ratio. The number of motors 7 provided corresponds to the number of joints 4 of the robot 1, the direction of movement of the joints 4, etc.

[0021] The first regenerative circuit 8 is a circuit that can be electrically connected to the inverter 6. As described above, the first regenerative circuit 8 is configured to receive the power (electrical energy) generated when the motor 7 is rotated by an external force and consume the power as heat. In other words, a dynamic brake, which is a braking force generated when the regenerative power (regenerative energy) of the motor 7 is consumed, acts on the motor 7. When power is supplied from the power source 5 to the motor 7, the first regenerative circuit 8 is maintained in a state electrically disconnected from the inverter 6. Then, when certain conditions are met, such as the generation of a predetermined amount of regenerative power from the motor 7, the first regenerative circuit 8 is electrically connected to the inverter 6.

[0022] The first regenerative circuit 8 has a first resistor (not shown) having a predetermined first resistance value. When the first regenerative circuit 8 is turned on, the first resistor is electrically connected to the inverter 6. The selective connection between the inverter 6 and the first resistor is achieved by turning a switching element on and off. That is, the inverter 6 and the first resistor can be selectively connected by switching on and off using a diode, transistor, or the like as described above. Then, when the first regenerative circuit 8 is electrically connected to the power supply path C, the regenerative power supplied from the motor 7 to the power supply 5 is consumed or absorbed by a first consumption amount corresponding to the resistance of the first resistor. The first regenerative circuit 8 is also provided with a first detection circuit 11 that detects the voltage and current acting on the first regenerative circuit 8.

[0023] For example, the first detection circuit 11 detects the voltage value between the input terminals of the first regenerative circuit 8 or the inverter 6. When the current or voltage detected by the detection circuit becomes equal to or greater than a predetermined first threshold, the above-mentioned switching element is switched ON. As a result, the first regenerative circuit 8 is electrically connected to the power supply path (circuit) C of the robot 1, which is an electrical path for the power source 5, motor 7, etc.

[0024] The first detection circuit 11 may be configured to activate the first regeneration circuit 8 when the voltage or current of the first regeneration circuit 8 or the power supply path C becomes equal to or greater than the first threshold. Therefore, the first detection circuit 11 may include an operational amplifier or a comparator. The first detection circuit 11 corresponds to the detection means in the embodiments of the present invention, the switching element that switches the first regeneration circuit 8 between ON and OFF corresponds to the regeneration state switching means in the embodiments of the present invention, and the state in which the first regeneration circuit 8 is ON corresponds to the first regeneration state of the regeneration circuit in the embodiments of the present invention.

[0025] The second regenerative circuit 9 is a circuit electrically connectable to the inverter 6 and is configured similarly to the first regenerative circuit 8. That is, the second regenerative circuit 9 is configured to receive power (electrical energy) generated when the motor 7 is rotated by an external force and consume the power as heat. That is, like the first regenerative circuit 8, the second regenerative circuit 9 applies a dynamic brake to the motor 7, which is a braking force generated by the rapid consumption of the regenerative power (regenerative energy) of the motor 7. When power is supplied to the motor 7 from the power source 5, the second regenerative circuit 9 is maintained in a state electrically disconnected from the inverter 6. Then, when certain conditions are met, such as the generation of a predetermined amount of regenerative power from the motor 7, as described above, the second regenerative circuit 9 is electrically connected to the inverter 6.

[0026] The second regenerative circuit 9 has a second resistor (not shown) having a predetermined second resistance value different from the first resistance value of the first resistor. When the second regenerative circuit 9 is turned ON, the second resistor is electrically connected to the inverter 6. The electrical connection between the inverter 6 and the second resistor is selectively established by turning a switching element ON and OFF, similar to the first regenerative circuit 8. When the second regenerative circuit 9 is electrically connected to the power supply path C, the regenerative power supplied from the motor 7 to the power supply 5 is consumed or absorbed according to the resistance of the second resistor.

[0027] The second regeneration circuit 9 is also provided with a second detection circuit 12, which is configured similarly to the first detection circuit 11 and detects the voltage and current acting on the second regeneration circuit 9. When the current and voltage detected by the second detection circuit 12 become equal to or greater than a predetermined second threshold, the above-mentioned switching element is switched ON. This electrically connects the second regeneration circuit 9 to the power supply path C. Note that the second detection circuit 12 may include an operational amplifier or a comparator, similar to the first detection circuit 11.

[0028] Furthermore, the second regenerative circuit 9 is arranged in parallel with the first regenerative circuit 8. Therefore, the resistance value generated when both the first regenerative circuit 8 and the second regenerative circuit 9 are electrically connected to the inverter 6 is smaller than the resistance value generated when either the first regenerative circuit 8 or the second regenerative circuit 9 is electrically connected to the inverter 6. In other words, the magnitude of the braking force generated in the motor 7 can be changed by electrically connecting or disconnecting the first regenerative circuit 8 and the second regenerative circuit 9, respectively. Therefore, the performance or resistance value of the first resistor in the first regenerative circuit 8 and the second resistor in the second regenerative circuit 9 is set according to the characteristics and performance of the motor 7 and the power source 5.

[0029] Note that by connecting the first regenerative circuit 8 and the second regenerative circuit 9 to the power supply path C, a second consumption amount of regenerative power is consumed or absorbed according to the resistance values ​​of the first resistor and the second resistor. Also, the second detection circuit 12 corresponds to the detection means in the embodiment of the present invention, the switching element that switches the second regenerative circuit 9 between ON and OFF corresponds to the regenerative state switching means in the embodiment of the present invention, and the state in which the first regenerative circuit 8 and the second regenerative circuit 9 are ON corresponds to the second regenerative state of the regenerative circuit in the embodiment of the present invention.

[0030] For example, when the arm unit 2 makes relatively slight contact with a surrounding object or person at a relatively small relative speed that does not disrupt their posture, the arm unit 2 does not have to be stopped immediately. For example, when it is detected that the arm unit 2 has made slight contact with a surrounding object, the motor 7 may be stopped at a predetermined deceleration, thereby causing the arm unit 2 to stop smoothly. This configuration improves the backdrivability of the robot 1 and increases the degree of freedom in controlling the robot 1. Therefore, for example, the first regenerative circuit 8 is provided with a first resistor that enables the motor 7 to be stopped gradually at a relatively small deceleration. For example, a resistor having a relatively large resistance is used for the first resistor. In this case, the amount of regenerative power consumed is relatively small, and a relatively small braking force is applied to the motor 7, causing the motor 7 to stop at a relatively small deceleration. In other words, the arm unit 2 can perform the above-described relatively smooth stopping operation.

[0031] Conversely, when the arm unit 2 collides with a surrounding object or person at a relatively high relative speed that causes the object or person to lose its position, that is, when relatively serious contact occurs, it may be preferable to immediately stop the arm unit 2. In such a case, a relatively large braking force must be applied to the motor 7 to quickly stop the motor 7. For this reason, the second regenerative circuit 9 is provided with a second resistor that can apply such a relatively large braking force to the motor 7.

[0032] The second regenerative circuit 9 is arranged in parallel with the first regenerative circuit 8 on the power supply path C. Therefore, the second resistor of the second regenerative circuit 9 is a resistor having a resistance value that takes into account the resistance value of the first resistor. As a result, if serious contact occurs with the arm portion 2, the second regenerative circuit 9 is short-circuited to the inverter 6 in addition to the first regenerative circuit 8, thereby increasing the amount of regenerative power consumed and applying a relatively large braking force to the motor 7. In other words, the motor 7 can be decelerated at a relatively large deceleration rate. Therefore, the motor 7 can be stopped quickly, thereby reducing damage caused by serious contact between the arm portion 2 and surrounding objects or people.

[0033] In this way, in the robot 1 according to the embodiment of the present invention, at least one of the first regenerative circuit 8 and the second regenerative circuit 9 is electrically connected between the input terminals of the inverter 6, thereby making it possible to select in stages the braking force generated in the motor 7 by the dynamic brake. Note that the first regenerative circuit 8 and the second regenerative circuit 9 may be configured to short-circuit the input terminals of the inverter 6 by closing a relay.

[0034] The controller 10 is a device that mainly controls the motor 7 or the inverter 6 to control the operation of the robot 1. The controller 10 mainly comprises an input unit, an output unit, a processor, and a memory unit. For example, when an external impact is applied, physical data detected by a sensor that detects load, such as a strain gauge, is converted into signal pulses and input to the processor. Alternatively, when the motor 7 regenerates power due to such an external impact, data related to the power generated by the regeneration is input to the processor.

[0035] The processor performs calculations based on the input detection values ​​and controls the ON / OFF of the motor 7 and the circuit, etc. Note that the controller 10 may be configured such that the processor loads a program stored in a recording medium into a working area of ​​the storage unit, executes the program, and performs various controls through the execution of the program, thereby executing functions that meet a predetermined purpose.

[0036] The processor is, for example, a CPU or a DSP. This processor is configured to control the controller 10 and perform various information processing operations. The storage unit includes, for example, a RAM and a ROM. As described above, the storage unit has a working area for the processor to execute programs. The storage unit may also include an auxiliary storage unit including an EPROM, a hard disk drive, or a portable recording medium, so-called removable media. The auxiliary storage unit freely stores various programs, various data, and various tables in the recording medium by reading or writing them.

[0037] The controller 10 may be configured as a PLC (Programmable Logic Controller) that performs output operations according to a pre-stored program in response to a predetermined input. A PLC is a conventionally known control device that is configured to be able to simultaneously control not only the robot 1 but also other devices to perform sequence control.

[0038] In the robot 1 configured as described above, when the robot 1 comes into contact with an environment such as a surrounding object, a load may be input to the motor 7 that drives the joint 4 of the robot 1, causing the motor 7 to rotate in the opposite direction to the direction of rotation when driven. When such a so-called reverse input torque or reverse driving force is input to the motor 7, the motor 7 enters a regenerative state. In other words, the reverse input torque causes the motor 7 to generate power, and the so-called regenerative power generated by this power generation is supplied to the power supply path C. As a result, the voltage of the power supply 5 increases, which may reduce the durability of the components that make up the power supply path C, such as the power supply 5.

[0039] To prevent such a situation, the robot 1 is provided with a regeneration circuit for consuming or absorbing the excess power generated by regeneration when the motor 7 regenerates power due to an unintended external force. The robot 1 according to the embodiment of the present invention is provided with the above-described first regeneration circuit 8 and second regeneration circuit 9 as such regeneration circuits. The robot 1 according to the embodiment of the present invention is configured so that the first regeneration circuit 8 and the second regeneration circuit 9 are selectively connected to the power supply path C, thereby consuming or absorbing the regenerated power of the motor 7 as appropriate.

[0040] 3 and 4 show a flowchart of an example of the operation when regenerative power of the motor 7 is consumed or absorbed due to an external force being input to the robot 1 or the arm unit 2. The flowchart in Fig. 3 shows the operation flow when a relatively minor collision occurs with the arm unit 2 as described above.

[0041] As shown in FIG. 3, first, in step S1, it is detected that a collision has occurred with the arm unit 2. The occurrence of such a collision is detected by a sensor or the like attached to the robot 1, which detects an input load. For example, in the robot 1, the strain gauges described above are provided in structural parts constituting the axes (links) of the robot 1, and detect the strain (deformation) caused by an external force, thereby detecting the magnitude, position, direction, etc. of the external force input to the arm unit 2. This detects an external force unintentionally input to the robot 1, i.e., a load that rotates the motor 7 in the reverse direction has been input to the arm unit 2 or the robot 1 due to unintentional contact or collision between the arm unit 2 or the robot 1 and the environment, such as a surrounding object. When it is detected that an external force has been input to the arm unit 2 in this way, the operation flow proceeds to step S2.

[0042] In step S1, if a collision is detected as described above, the drive power supplied to the motor 7 may be stopped immediately. In other words, if a collision between the arm unit 2 and a nearby object is detected, it is preferable to quickly reduce the load input to the nearby object or the arm unit 2 due to the collision. Therefore, if such a collision is detected, the inverter 6 may be configured to quickly stop the supply of drive power to the motor 7, thereby suppressing a decrease in durability due to the collision.

[0043] In step S2, the first detection circuit 11 detects a voltage equal to or greater than the first threshold value due to regeneration by the motor 7. That is, the magnitude of energy (power) generated by regeneration by the motor 7 in response to an external force is detected. As a result, it is detected that the voltage on the power supply path C rises and exceeds the voltage of the power source 5. In step S2, the amount of regenerated power of the motor 7 is detected by a sensor or the like that detects voltage, current, or power, which is provided on the power supply path C or the like. Specifically, the first detection circuit 11 and the second detection circuit 12, which are provided in the first regeneration circuit 8 and the second regeneration circuit 9, respectively, detect the voltages supplied to the first resistor and the second resistor. It is then detected that the detected voltage is equal to or greater than a predetermined first threshold value. Note that the first threshold value is not limited to voltage, and may be another electrical parameter such as current or power.

[0044] Such a first threshold value may be set according to the allowable voltage of the power supply 5, etc. For example, the first threshold value may be set based on a voltage slightly higher than the voltage of the power supply 5. In other words, the first threshold value is set to a value that can detect even the amount of regenerative power of the motor 7 that is generated when a relatively small load is input to the arm portion 2. In other words, the first threshold value may be set according to a value that can detect that a voltage that is even slightly higher than the voltage of the power supply 5 acts on the power supply 5, or according to the braking force that is desired to be generated by the motor in the event of a collision, etc.

[0045] When the first detection circuit 11 of the first regenerative circuit 8 detects a voltage equal to or greater than the first threshold thus set, the process proceeds to step S3. In step S3, the first regenerative circuit 8 is switched ON. That is, when the first detection circuit 11 detects a voltage equal to or greater than the first threshold, a voltage exceeding the voltage of the power supply 5 acts on the power supply path C. In order to suppress the resulting voltage rise of the power supply 5, a switching element such as a transistor is switched on in response to the detection of a voltage equal to or greater than the first threshold, and the first regenerative circuit 8 is turned ON.

[0046] That is, the first regenerative circuit 8 is electrically connected to the inverter 6, and a resistance corresponding to the resistance value of the first resistor acts on the power supply path C. When a minor collision occurs, the external force input by the collision is small, and the amount of regenerative power (regenerative energy) of the motor 7 is also relatively small. When the amount of regenerative power is relatively small, a relatively large resistance is applied to the power supply path C, so that the deceleration of the motor 7 is also relatively small.

[0047] When the first regenerative circuit 8 is turned ON in this way and a resistance corresponding to the resistance of the first regenerative circuit 8 acts on the power supply path C, the operation of the robot 1 proceeds to step S4. In step S4, the regenerative power generated by the power generation of the motor 7 is consumed as heat by the first resistor of the first regenerative circuit 8. That is, a relatively small braking force is applied to the motor 7. Such braking force causes the motor 7 to gradually stop (converge) with a relatively small deceleration. That is, the movement of the arm unit 2 caused by an external force is smoothly stopped. Note that when the regenerative power of the motor 7 is consumed by the first regenerative circuit 8 and the voltage becomes smaller than the first threshold, the first regenerative circuit 8 is switched OFF.

[0048] Next, with reference to the flowchart shown in Fig. 4, the operation of the robot 1 when a relatively large collision such as that described above occurs with the arm unit 2 will be described. Note that in the flowcharts described below, explanations of steps that perform the same processing as steps that have already been explained will be omitted or simplified.

[0049] As shown in Fig. 4, first, in step S11, similar to step S1, it is detected that a collision has occurred with the arm unit 2. That is, it is detected that an external force has been applied to the arm unit 2, causing it to rotate in the direction opposite to the driving direction of the motor 7. When it is detected that such regeneration of the motor 7 has occurred, the process proceeds to step S12. Note that, similar to step S1, in step S11, if a collision is detected as described above, the drive power supplied to the motor 7 may be stopped immediately.

[0050] In step S12, similar to step S2, the first detection circuit 11 detects a voltage equal to or greater than the first threshold value due to regeneration by the motor 7. That is, the magnitude of the energy (electric power) generated by regeneration by the motor 7 in response to an external force is detected. As a result, it is detected that the voltage on the power supply path C has increased and exceeded the voltage of the power supply 5. In step S12, the first detection circuit 11 and the second detection circuit 12 provided in the first regeneration circuit 8 and the second regeneration circuit 9, respectively, detect the voltage or current supplied to the first resistor and the second resistor. Then, it is detected that the detected voltage or current is equal to or greater than the predetermined first threshold value described above.

[0051] When the first detection circuit 11 of the first regenerative circuit 8 detects a voltage equal to or greater than the first threshold, the process proceeds to step S13. In step S13, similar to step S3, the first regenerative circuit 8 is switched ON. That is, when the first detection circuit 11 detects a voltage equal to or greater than the first threshold, a voltage exceeding the voltage of the power supply 5 acts on the power supply path C. As a result, in order to suppress a voltage rise of the power supply 5, the switching element is switched and the first regenerative circuit 8 is turned ON. That is, the first regenerative circuit 8 is electrically connected to the inverter 6, and a resistance corresponding to the resistance value of the first resistor acts on the power supply path C. A braking force corresponding to that resistance acts on the motor 7.

[0052] When the first regenerative circuit 8 is turned ON and a resistance corresponding to the resistance of the first regenerative circuit 8 acts on the power supply path C, the operation of the robot 1 proceeds to step S14. In step S14, the second detection circuit 12 detects a voltage equal to or greater than a second threshold, which is greater than the first threshold, due to the regenerative power generated by the regeneration of the motor 7. In other words, although the regenerative power of the motor 7 is consumed as heat by activating the first regenerative circuit 8, the amount of energy generated by the regeneration exceeds the amount of energy consumed by the first regenerative circuit 8. As a result, the voltage on the power supply path C rises even though the first regenerative circuit 8 is activated. In step S14, the voltage equal to or greater than the second threshold is detected, indicating that a serious collision has occurred, in which a relatively large external force has been input. Note that, like the first threshold, the second threshold is not limited to voltage and may be another electrical parameter such as current or power.

[0053] The second threshold is set to a value greater than the first threshold and is set based on the allowable voltage of the power supply 5. For example, the second threshold is set to a value that can detect that a relatively large amount of regenerative power is generated when the arm portion 2 comes into hard contact with a surrounding object and a relatively large load is input to the motor 7. In other words, the second threshold is set to a value that can detect that the regenerative power of the motor 7 cannot be sufficiently consumed by the first regenerative circuit 8 alone and that further consumption of regenerative power is necessary. When the process proceeds to step S14, the second detection circuit 12 has detected a voltage equal to or greater than the second threshold set in this manner.

[0054] When the second detection circuit 12 detects a voltage equal to or greater than the second threshold thus set, the process proceeds to step S15. In step S15, the second regeneration circuit 9 is switched ON. That is, when the second detection circuit 12 detects a voltage equal to or greater than the second threshold, a voltage exceeding the voltage of the power supply 5 acts on the power supply path C. In order to suppress the resulting voltage rise of the power supply 5, a switching element such as a transistor is switched on when a voltage equal to or greater than the second threshold is detected, and the second regeneration circuit 9 is also turned ON. That is, because the second regeneration circuit 9 is electrically connected to the inverter 6, a resistance corresponding to the resistance values ​​of the first resistor and the second resistor acts on the power supply path C.

[0055] By connecting the second regenerative circuit 9 to the power supply path C in addition to the first regenerative circuit 8 in this way, the process proceeds to step S16. In step S15, a braking force corresponding to the resistance values ​​of the first regenerative circuit 8 and the second regenerative circuit 9 acts on the motor 7. At this time, because the first regenerative circuit 8 and the second regenerative circuit 9 are connected in parallel to the power supply path C, a resistance acting on the power supply path C that is smaller than the resistance generated by the first regenerative circuit 8. In other words, the amount of regenerative power consumed by the motor 7 by the first regenerative circuit 8 and the second regenerative circuit 9 increases. Therefore, the braking force acting on the motor 7 is larger than when only the first regenerative circuit 8 is operating. As a result, the motor 7 stops with a relatively large deceleration, and the arm portion 2 quickly stops (converges).

[0056] Furthermore, as the energy consumed by the first regenerative circuit 8 and the second regenerative circuit 9 increases, the voltage on the power supply path C decreases, thereby suppressing a voltage rise in the power supply 5. When the regenerative power of the motor 7 is consumed and the voltage falls below the second threshold, the second regenerative circuit 9 is switched OFF. After that, when the voltage falls below the first threshold, the first regenerative circuit 8 is switched OFF.

[0057] As described above, in the robot 1 according to the embodiment of the present invention, the first regenerative circuit 8 and the second regenerative circuit 9 are connected in parallel to the power supply path C between the power source 5 and the motor 7 as regenerative circuits for applying a dynamic brake to the robot 1. The first regenerative circuit 8 and the second regenerative circuit 9 are provided with the first detection circuit 11 and the second detection circuit 12, respectively. The first detection circuit 11 detects the generation of a voltage equal to or greater than a first threshold value that is higher than the voltage of the power source 5. When a voltage equal to or greater than the first threshold value is generated, the first regenerative circuit 8 is switched ON. As a result, the regenerative power of the motor 7 is consumed as heat by the first resistor, and a braking force corresponding to the consumed energy is applied to the motor 7.

[0058] The second detection circuit 12 also detects the generation of a voltage equal to or greater than a second threshold, which is greater than the first threshold. When a voltage equal to or greater than the second threshold is generated, the second regenerative circuit 9 also switches ON. This causes the regenerative power of the motor 7 to be consumed as heat by the first resistor and the second resistor, thereby suppressing a voltage rise in the power supply 5. Furthermore, a braking force corresponding to the amount of regenerative power consumed by the motor 7 acts on the motor 7.

[0059] When only the first regenerative circuit 8 is turned on, a larger resistance acts on the power supply path C compared to when both the first regenerative circuit 8 and the second regenerative circuit 9 are turned on. As a result, a relatively small braking force acts on the motor 7, causing the motor 7 to stop with a relatively small deceleration. On the other hand, when both the first regenerative circuit 8 and the second regenerative circuit 9 are turned on, a relatively large braking force acts on the motor 7. In other words, the motor 7 stops with a larger deceleration compared to when only the first regenerative circuit 8 is turned on.

[0060] As described above, in the robot 1 according to the embodiment of the present invention, the two regenerative circuits that operate based on different thresholds can change the braking force applied to the motor 7 in stages when an external force is input to the arm section 2 and the motor 7 starts regenerating. Therefore, when a voltage equal to or greater than the first threshold is generated, the first regenerative circuit 8 can be turned ON to suppress a voltage rise in the power supply 5. In addition, in this case, a relatively small braking force acts on the motor 7, so that the movement of the robot 1 can be made relatively supple (smooth) when a relatively small external force is input to the robot 1, such as a minor collision.

[0061] On the other hand, when a voltage equal to or greater than the second threshold is generated, the second regenerative circuit 9 is turned ON in addition to the first regenerative circuit 8. When a voltage equal to or greater than the second threshold is generated, the first regenerative circuit 8 alone is not able to fully consume the regenerative power of the motor 7, and there is a possibility that the voltage of the power supply 5 will rise above the allowable voltage. Therefore, by turning on the second regenerative circuit 9, a relatively small resistance corresponding to the first regenerative circuit 8 and the second regenerative circuit 9 acts, which can further suppress the rise in voltage of the power supply 5. Furthermore, in this case, a relatively large braking force acts on the motor 7, so that the movement of the robot 1 can be quickly stopped when a relatively large external force is input to the robot 1, such as a serious collision.

[0062] Therefore, a dynamic brake can be applied according to an external force input to the robot 1, thereby improving the so-called backdrivability of the robot 1. Furthermore, because it is only necessary to provide two regenerative circuits that operate based on different thresholds, it is possible to prevent the control load from increasing and the electrical circuit from becoming complicated. In other words, high backdrivability can be achieved with a simple circuit without any special control.

[0063] Although the embodiments of the present invention have been described above, the present invention is not limited to the above examples and may be modified as appropriate within the scope of achieving the object of the present invention. For example, the robot 1 according to the embodiments of the present invention may be configured to be capable of gradually changing the magnitude of the braking force generated by the motor 7 while preventing the voltage of the power supply 5 from exceeding the allowable voltage. For example, the first regenerative circuit 8 and the second regenerative circuit 9 may be arranged in series with the power supply path C. In this case, both the first regenerative circuit 8 and the second regenerative circuit 9 are switched ON when a voltage equal to or greater than the first threshold is detected. Alternatively, only the first regenerative circuit 8 may be configured to be switched ON when a voltage equal to or greater than the second threshold is detected.

[0064] Alternatively, a plurality of resistors may be provided in one regenerative circuit to generate a plurality of resistances that differ in stages as described above. In this case, resistors, switching elements, etc. may be appropriately arranged in the regenerative circuit, and the resistors that consume regenerative power may be switched based on predetermined electrical parameters such as voltage, current, and power, thereby generating resistances in stages.

[0065] That is, it is only necessary that the regenerative circuits are configured to be able to selectively connect or disconnect the regenerative circuits to or from the power supply path C to generate a plurality of resistances in stages in the power supply path C, or to set at least two or more regenerative states by the regenerative circuits so that the amount of regenerative power consumed varies in stages. Therefore, the number of regenerative circuits, the configuration of the power supply path C, or the magnitude of the resistance of each regenerative circuit may be changed as appropriate depending on the configuration of the robot or motor.

[0066] Furthermore, the configuration for changing the resistance value generated in the power supply path C is not limited to the configuration described above. For example, a configuration may be adopted in which a desired braking force is generated in the motor 7 by connecting only either the first regenerative circuit 8 or the second regenerative circuit 9. That is, the first resistor may be configured so that the amount of regenerative power consumed becomes the first consumption amount described above when only the first regenerative circuit 8 is connected to the power supply path C, and the second resistor may be configured so that the amount of regenerative power consumed becomes the second consumption amount described above when only the second regenerative circuit 9 is connected to the power supply path C.

[0067] Furthermore, the power supply path C may be configured so that the amount of regenerative power consumption can be set in three stages: when the first regenerative circuit 8 is connected, when the second regenerative circuit 9 is connected, and when both the first regenerative circuit 8 and the second regenerative circuit 9 are connected. In other words, it is sufficient that the amount of regenerative power consumption of the motor 7 can be selected from multiple levels, that is, the braking force applied to the motor 7 can be set in stages, simply by electrically connecting or disconnecting one of the regenerative circuits to or from the power supply path C.

[0068] The above-described operation of the robot 1 may be executed by the controller 10. For example, a detection unit such as a plurality of sensors or circuits provided on the circuit acquires the amount of regenerative power (regenerative energy) of the motor 7 and the voltages of the first regenerative circuit 8 and the second regenerative circuit 9. The controller 10 determines whether the acquired parameters are equal to or greater than a first predetermined value or a second predetermined value stored in advance. The first predetermined value and the second predetermined value are set to values ​​that enable determination of whether the voltage of the power supply 5 becomes equal to or greater than the allowable voltage when a load that rotates the motor 7 in the reverse direction is input to the robot 1. The first predetermined value and the second predetermined value may be set in a stepwise manner, similar to the above-described first threshold value and second threshold value.

[0069] Then, when the controller 10 determines that a value equal to or greater than the first predetermined value set in this manner is acting on the power supply path C, the controller 10 activates the first regenerative circuit 8. That is, the controller 10 switches the switching element of the first regenerative circuit 8 ON. This allows a resistance corresponding to the first regenerative circuit 8 to act on the power supply path C. Thereafter, although the first regenerative circuit 8 is operating, it is detected from the above-mentioned parameters that the regenerated energy exceeds the energy consumed (absorbed) by the first regenerative circuit 8, that is, the voltage rise of the power supply 5 continues. That is, when the controller 10 determines that a value equal to or greater than the second predetermined value is acting on the power supply path C, the controller 10 also activates the second regenerative circuit 9. That is, the controller 10 switches the switching element of the second regenerative circuit 9 ON. This allows a resistance corresponding to the first regenerative circuit 8 and the second regenerative circuit 9 to act on the power supply path C. Even with this configuration, it is possible to change the braking force acting on the robot 1 while suppressing the voltage rise of the power supply 5, thereby improving the so-called backdrivability of the robot 1. [Explanation of symbols]

[0070] 1. Robot 2 Arm section 3 Gripping part 4 Joints 5 Power supply 6 inverters 7 Motor 8 1st generation circuit 9 2nd generation circuit 10 Controllers 11 Detection circuit 12 Detection circuit C Power supply path

Claims

[Claim 1] A robot comprising at least one joint, a motor for operating the joint, and a power source for supplying power for driving the motor, a regenerative circuit that receives and consumes regenerative power generated when the motor is operated by an external force; The regeneration circuit is configured to switch between at least two states, a first regeneration state and a second regeneration state, which have different amounts of power consumption; a detection means for detecting the voltage of the power supply; and a regeneration state switching means for setting the regeneration circuit to the first regeneration state when the detected voltage of the power source is a first predetermined value, and for setting the regeneration circuit to the second regeneration state when the detected voltage of the power source is a second predetermined value that is greater than the first predetermined value. A robot characterized by:

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