JP2024001791A - Motor controller and motor control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently perform operation of high speed high load of a plurality of motors in a robot mounting the respective motors.

SOLUTION: A motor controller includes: respective axis current calculation parts which calculate q axis current command value and d axis current command value on the basis of speed command value notified from outside; a voltage command value calculation part calculating a plurality of voltage command values to be value of voltage applied to the plurality of motors on the basis of the q axis current command value and the d axis current command value; an acceleration command value calculation part calculating acceleration command value on the basis of the speed command value; and a d axis current command value limiting part which outputs d axis current command value to be first current limit value or below in a power running state and outputs d axis current command value to be second current limit value or below in a regenerating state on the basis of the speed command value and the acceleration speed command value. A regeneration determination part determines either the power running state or the regenerating state on the basis of a motor state of highest load of the plurality of motors.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present disclosure relates to a motor control device and a motor control method using current vector control.

Patent Document 1 discloses a voltage command value calculation unit that calculates a voltage command value of a voltage to be applied to a motor based on a q-axis current command value and a d-axis current command value, and a voltage command value calculation unit that outputs driving power to the motor based on the voltage command value. a d-axis current command value calculation section that calculates a d-axis current command value that limits the voltage command value to below the maximum voltage that can be applied to the drive circuit by field weakening control; The d-axis current command value limiter limits the d-axis current command value, and the d-axis current command value limiter limits the d-axis current command value so that the voltage command value does not exceed the maximum voltage. A motor control device is disclosed that includes a q-axis current command value limiting section that limits the current command value.

Patent Document 2 discloses a synchronous motor control method that controls the synchronous motor by determining a current to be passed through the synchronous motor based on a value obtained by converting the current flowing through the synchronous motor into dq axes. In this control method, the q-axis current command value, which indicates the synchronous motor's q-axis current, is set according to the torque command value, which indicates the output torque of the synchronous motor, until the voltage between the terminals of the synchronous motor reaches a predetermined maximum allowable voltage. The d-axis current command value indicating the d-axis current of the synchronous motor is set to zero. In addition, this control method determines the q-axis current value according to the torque command value when the voltage between the terminals of the synchronous motor reaches a predetermined maximum allowable voltage, and also determines the q-axis current value according to the torque command value. The d-axis current command value is determined based on the following.

International Publication No. 2020/095479 Japanese Patent Application Publication No. 2006-158000

An object of the present disclosure is to provide a motor control device and a motor control method that efficiently realize high-speed, high-load operation of each motor in a robot equipped with a plurality of motors.

The present disclosure provides an axis current calculation unit that calculates a q-axis current command value and a d-axis current command value based on a speed command value notified from the outside; a voltage command value calculation unit that calculates a plurality of voltage command values, which are voltage values to be applied to each of the plurality of motors, based on the voltage command values; a drive circuit that outputs the respective outputs, an acceleration command value calculation section that calculates an acceleration command value based on the speed command value, and a power running state or a regeneration state based on the speed command value and the acceleration command value. a regeneration determination unit that makes a determination; a first current limit value that is a current limit value of the d-axis current command value in the power running state; and a second current limit value that is a current limit value of the d-axis current command value in the regeneration state. a current limit value storage unit that stores a current limit value, and outputs the d-axis current command value that is equal to or less than the first current limit value in the power running state, and the current command value that is equal to or less than the second current limit value in the regenerative state; a d-axis current command value limiting section that outputs a d-axis current command value, and the regeneration determining section determines whether the motor is in the power running state or the regeneration state based on the state of the motor with the highest load among the plurality of motors. Provided is a motor control device that determines either of the following.

The present disclosure also includes a step of calculating a q-axis current command value and a d-axis current command value based on a speed command value notified from the outside, and a step of calculating an acceleration command value based on the speed command value. , determining either a power running state or a regeneration state based on the speed command value and the acceleration command value, and a first current limit value that is a current limit value of the d-axis current command value or less in the power running state. outputting the d-axis current command value that is equal to or less than a second current limit value that is a current limit value of the d-axis current command value in the regenerative state; a step of calculating a plurality of voltage command values, which are voltage values to be applied to each of the plurality of motors, based on the axis current command value and the d-axis current command value; outputting a plurality of driving powers to each of the motors, and the determination of either the power running state or the regeneration state is performed based on the state of the motor with the highest load among the plurality of motors. A motor control method is provided.

According to the present disclosure, in a robot equipped with a plurality of motors, high-speed, high-load operation of each motor can be efficiently realized.

Schematic diagram showing a system configuration example of a welding robot system according to the present embodiment Block diagram showing a configuration example for one axis of a robot control device corresponding to one motor Block diagram showing a detailed configuration example of a PWM inverter circuit Block diagram showing a detailed configuration example of the current vector control section Block diagram showing a detailed configuration example of the control unit for one axis Diagram showing an outline of changes in motor speed over time in power running state and regeneration state Diagram showing an example of time change of speed command and acceleration command Flowchart showing the operation procedure for determining the current limit value of the d-axis current command value of the robot control device according to the present embodiment

(Circumstances leading to this disclosure)
Generally, as a method of controlling the current flowing in a permanent magnet synchronous motor, the motor current is separated into a q-axis current that contributes to torque and a d-axis component (d-axis current) that is perpendicular to the q-axis. Vector control is used. A vector control unit that performs vector control receives an external command and calculates a command voltage to a motor drive unit that supplies electric power to the motor. In such vector control, there is a phenomenon in which the command voltage exceeds the voltage that can be supplied by the motor drive unit, such as when the value of an external command becomes large. This phenomenon is called voltage saturation. Voltage saturation occurs more easily as the rotational speed of the motor increases. This is because the induced voltage generated during motor rotation increases in proportion to the rotation speed, and in order to compensate for this increase with the supply voltage, the voltage between the terminals of the motor also increases. Furthermore, when the load is large or the power supply voltage is low, the supply voltage margin becomes small, making voltage saturation more likely to occur.

When the voltage is saturated, the q-axis current cannot be increased during powering operation, the torque decreases, the integral term of the current controller becomes saturated (windup), and the static or dynamic characteristics deteriorate. Furthermore, during regenerative operation, the load on the motor is lighter than during power operation, so it is possible to drive with less current. During regenerative operation, energy flows backward to the power supply voltage side, so that the voltage value of the electrolytic capacitor installed in the power supply circuit becomes higher than in normal times. If the voltage value of an electrolytic capacitor exceeds a predetermined tolerance, it will break, so during regenerative operation, the power stored in the electrolytic capacitor can be discharged or the energy can be used for other purposes (for example, to other circuit components). power supply and heat dissipation in the resistor) to prevent damage to the electrolytic capacitor (in other words, the power supply circuit). Therefore, as a means for suppressing voltage saturation, field weakening control is used to demagnetize the magnetic flux caused by the permanent magnet by flowing a negative d-axis current to suppress an increase in the induced voltage.

Patent Document 1 discloses a configuration in which the q-axis current command value is also limited by limiting the d-axis current command value in order to limit the voltage command value of the voltage applied to the motor to below the maximum voltage that can be applied to the drive circuit by field weakening control. It has become. Therefore, there has been a problem in that it is difficult to operate the motor at high speed and high load.

Further, in Patent Document 2, when the voltage between the terminals of the synchronous motor reaches the maximum allowable voltage and a speed command value is given that causes the motor rotation speed to exceed the specified rotation speed, the rotation speed and the torque command value are Then, the d-axis current command value of the d-axis current to be passed through the synchronous motor is determined. Therefore, by setting the d-axis current command value to zero during acceleration until the voltage between the terminals of the synchronous motor reaches the maximum allowable voltage, the desired output torque can be obtained regardless of the increase in the induced voltage. However, during constant speed operation and deceleration after the end of acceleration, the d-axis current command value is calculated to be proportional to the torque command value, so the compensation amount by flowing the d-axis current decreases, and the motor The problem has been that it is difficult to operate the system at high speed and under high load.

Therefore, in the following embodiments, an example of a motor control device and a motor control method that efficiently realize high-speed, high-load operation of each motor in a robot equipped with a plurality of motors will be described.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments specifically disclosing a motor control device and a motor control method according to the present disclosure will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed explanations of well-known matters or redundant explanations of substantially the same configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.

First, with reference to FIG. 1, a configuration example of a welding robot system 1000 according to the present embodiment will be described. FIG. 1 is a schematic diagram showing an example of a system configuration of a welding robot system 1000 according to the present embodiment. As shown in FIG. 1, welding robot system 1000 includes a manipulator MC1 and a robot control device 100.

In FIG. 1, the XYZ axes are the axes illustrated in FIG. More specifically, two axes (i.e., Define the Z-axis in the direction). The X-axis is defined in the longitudinal direction of the base portion 110, where the cross section of the manipulator MC1 is rectangular, and the Y-axis is defined in the direction perpendicular to both the X-axis and the Z-axis.

The manipulator MC1 is connected to the robot control device 100 so as to be able to transmit and receive data or signals. In the present embodiment, the manipulator MC1 is, for example, an arc welding robot with six axes and multiple joints. Note that the welding performed by the manipulator MC1 is not limited to arc welding. The manipulator MC1 controls the base section 110, the base section 120, the first arm 130, the second arm 140, the wrist 150, the torch bracket 160, and the positions and angles of these components. The welding torch TCH1 includes at least one motor MT1 (see FIG. 2) and a welding torch TCH1.

The base portion 110 is fixed to the floor surface. The base portion 120 is attached to the base portion 110 so as to be pivotable around a pivot axis J1 extending in the vertical direction (Z-axis). The first arm 130 is fixed to the base portion 120 so as to be swingable around a pivot axis J2 extending in a substantially horizontal direction orthogonal to the pivot axis J1. The second arm 140 is fixed to the first arm 130 so as to be swingable around a pivot axis J3 extending in a direction parallel to the pivot axis J2. The wrist 150 is attached to the second arm 140 so as to be pivotable around a pivot axis J4 extending in a direction parallel to the longitudinal direction of the second arm 140. The torch bracket 160 is fixedly attached to the wrist 150 so as to be pivotable around a pivot axis J5 extending in a direction perpendicular to the pivot axis J4 and pivotably around a pivot axis J6 extending in a direction perpendicular to the pivot axis J5. There is. Further, a welding torch TCH1 is provided at the distal end of the torch bracket 160, and a welding wire (not shown) is inserted through the welding torch TCH1 and fed from the tip of the welding torch TCH1. The robot control device 100 places a welding torch TCH1 holding a welding wire (not shown) at a welding start position (starting point), and moves the welding wire (not shown) extending from the welding torch TCH1 along an arbitrary trajectory (welding line). The motor MT1 for the base part 110, the motor MT1 for the base part 120, the motor MT1 for the first arm 130, the motor MT1 for the second arm 140, the motor MT1 for the wrist 150, and the torch bracket. 160 motor MT1 is controlled.

The robot control device 100 is connected to the manipulator MC1 so as to be able to transmit and receive data or signals. The robot control device 100 controls the driving of the manipulator MC1 during welding according to a welding teaching program for the manipulator MC1 generated based on various information inputted by a teach pendant (not shown). The welding teaching program of the manipulator MC1 includes information regarding each welding section to be welded using the welding torch TCH1 (for example, the start point and end point of the welding section, etc.), various operations for performing welding (for example, It is generated including information such as the position, distance, angle (posture), operating speed, etc. of the welding torch TCH1 for executing (dry run, approach, retract, avoidance, etc.), information such as welding conditions, etc.

Furthermore, the robot control device 100, which is an example of a motor control device, executes operations for controlling the driving of a plurality of motors MT1 (see FIG. 2) mounted on the manipulator MC1. Here, the plurality of motors MT1 include a motor MT1 for the base section 110, a motor MT1 for the base section 120, a motor MT1 for the first arm 130, a motor MT1 for the second arm 140, and a motor MT1 for the wrist 150. , a motor MT1 for the torch bracket 160. In this embodiment, in order to control the rotation of motor MT1, robot control device 100 has a d-axis that corresponds to the magnetic pole position direction of a permanent magnet held by the rotor of motor MT1, and a q-axis that is orthogonal to this d-axis. Current vector control based on a dq-axis coordinate system consisting of axes is used. More specifically, first, on the d-axis, current control is performed based on current vector control in which a d-axis voltage command is generated using an input as a d-axis current value. On the other hand, the q-axis is characterized by voltage control based on speed control that generates a q-axis voltage command using the rotational speed as the input.

The detailed configuration of the robot control device 100 that uses current vector control will be described below with reference to the drawings from FIG. 2 onwards.

Next, with reference to FIG. 2, the internal configuration of the robot control device 100 will be described. FIG. 2 is a block diagram showing an example of the configuration of one axis of the robot control device 100 corresponding to one motor MT1. In other words, FIG. 2 shows only the configuration of the robot control device 100-1 corresponding to one axis (that is, one motor MT1) for controlling each of the six motors MT1 mounted on the manipulator MC1. . Therefore, when controlling each of the six motors MT1 shown in FIG. 1, the robot control device 100 includes six configurations of the robot control device 100-1 shown in FIG. 2.

The robot control device 100-1 includes at least a PWM (Pulse Width Modulation) inverter circuit 10, current detection sections DT1 and DT2, a current vector control section 20, a control section 30, and a rotation speed calculation section 40. Since the robot control device 100-1 drives the motor MT1 according to an external speed command and speed FB (Feedback), the robot control device 100-1 has a d-axis component in the rotor magnetic flux direction and a q-axis perpendicular to the d-axis with respect to the current of the motor MT1. Vector control is used to control the q-axis component and the q-axis component separately. Note that the motor MT1 and the encoder EN1 included in the motor MT1 are not included in the robot control device 100-1.

The motor MT1 is, for example, a brushless motor such as a permanent magnet synchronous motor (PMSM), and includes a rotor that can rotate around a shaft and holds a permanent magnet (not shown). , and a stator (stator) including a three-phase coil in which three-phase windings are wound around a stator core. A rotor is rotatably arranged to face the stator. In the motor MT1, alternating current power having phases different by 120 degrees from each other is applied from the robot control device 100-1 to the windings (coils) of the U-phase, V-phase, and W-phase, so that the rotor of the motor MT1 rotates around the shaft. It rotates around the center. FIG. 2 shows a configuration example in which the motor MT1 is driven by three-phase alternating current power including U-phase, V-phase, and W-phase.

Encoder EN1 is attached to motor MT1. Encoder EN1 outputs a signal corresponding to the rotational position of a rotor (not shown) of motor MT1 to current vector control section 20. In this way, encoder EN1 detects the rotational position of the rotor of motor MT1 as an electrical angle. Note that if the rotational position or rotational speed of the rotor can be detected by estimation, the configuration of the encoder EN1 may be omitted. Further, instead of the encoder EN1, a Hall element capable of detecting the rotational position of the motor MT1 may be arranged near the rotor. In this case, a signal indicating position information detected by the Hall element is input as a feedback signal to each of the control section 30 and the current vector control section 20.

The PWM inverter circuit 10 converts the DC voltage from the power supply voltage Vdc into each phase ( Power conversion processing is performed to convert the voltage into AC voltage that is actually applied to the U-phase, V-phase, and W-phase. A configuration example of the PWM inverter circuit 10 will be described later with reference to FIG. 3.

The current detection unit DT1 detects the phase current i _u (armature current) flowing in the U-phase winding of the motor MT1, and performs current vector control using the current value of the detected phase current i _u as the U-phase current FB (Feedback). 20.

The current detection unit DT2 detects the phase current i _v (armature current) flowing in the V-phase winding of the motor MT1, and performs current vector control using the current value of the detected phase current i _v as the V-phase current FB (Feedback). 20.

The current vector control unit 20 issues voltage commands to each of the d-axis, which is the field direction of the motor MT1, and the q-axis, which is the direction perpendicular to the d-axis (q-axis voltage command v _q ^* , d-axis voltage, which will be described later). A two-phase to three-phase conversion process is performed to convert the command v _d ^* ) into a three-phase voltage command (PWM command) to be applied to the U-phase, V-phase, and W-phase of the motor MT1. Further, the current vector control unit 20 generates a d-axis voltage command v _d ^* so that the error between the value of the d-axis current command i _d ^* from the control unit 30 and the d-axis current value becomes zero, and similarly , the q-axis voltage command v _q ^* _is generated so that the error between the value of the q-axis current command i q * from the control unit 30 and ^the q-axis current value becomes zero. Further, the current vector control unit 20 controls the actual current value of the U phase detected by the current detection unit DT1, the actual current value of the V phase detected by the current detection unit DT2, and the electrical angle ( In other words, processing is performed to calculate the d-axis current value and the q-axis current value based on the rotational position of the rotor. A configuration example of the current vector control section 20 will be described later with reference to FIG. 4.

The control unit 30 generates a q-axis current command i _q ^* and a d-axis current command i _d ^* based on at least a speed command from the outside and a speed FB (Feedback) from the rotation speed calculation unit 40. In particular, the control unit 30 determines the d-axis current command i _d ^* based on the speed command from the outside, the speed FB from the rotational speed calculation unit 40, and the state of the motor MT1 (for example, either the power running state or the regenerative state). Then, a d-axis current command i _d ^* is generated. Although details will be described later, the state of the motor MT1 is determined based on the state of the motor MT1 corresponding to each axis of the manipulator MC1, which is an arc welding robot having six axes and multiple joints. A configuration example of the control unit 30 will be described later with reference to FIG. 5.

The rotational speed calculation unit 40 calculates the rotational speed of the rotor of the motor MT1 from the amount of change per unit time in the electrical angle (in other words, the rotational position of the rotor) detected by the encoder EN1, and calculates the rotational speed of the rotor of the motor MT1 as the speed FB (Feedback). It is output to the control unit 30 as

Next, with reference to FIG. 3, the internal configuration of the PWM inverter circuit 10 will be described. FIG. 3 is a block diagram showing a detailed configuration example of the PWM inverter circuit 10. PWM inverter circuit 10 includes six switching elements 111, 121, 131, 141, 151, and 161.

A free wheel diode 112 is provided in parallel to the switching element 111, a free wheel diode 122 is provided in parallel to the switching element 121, a free wheel diode 132 is provided in parallel to the switching element 131, and a free wheel diode 142 is provided in the switching element 141. are provided in parallel, a free wheel diode 152 is provided in parallel to the switching element 151, and a free wheel diode 162 is provided in parallel to the switching element 161. Each of the switching elements 111 to 161 is, for example, an IGBT (Insulated Gate Bipolar Transistor), but is not limited to an IGBT. In the PWM inverter circuit 10, the interconnection point between the emitter of the switching element 111 and the collector of the switching element 141 is connected to the winding of one of the three phases (for example, U phase) of the motor MT1, and the emitter of the switching element 121 and The interconnection point with the collector of the switching element 151 is connected to the winding of one of the three phases (for example, V phase) of the motor MT1, and the interconnection point between the emitter of the switching element 131 and the collector of the switching element 161 is connected to the winding of one of the three phases (for example, V phase) of the motor MT1. It is connected to the winding of one of the three phases (for example, W phase) of MT1.

The PWM inverter circuit 10 has a pair of switching elements on the positive side of the power supply and a switching element on the negative side of the power supply for three phases, U-phase, V-phase, and W-phase. This is a switching circuit that outputs voltage. The PWM inverter circuit 10 inputs a drive signal (that is, a PWM command) from the current vector control unit 20 to the gates of each of the switching elements 111 to 161, and turns each of the switching elements 111 to 161 on and off in order, thereby generating an applied signal. The torque and rotational speed of motor MT1 are controlled by converting the DC power supply (power supply voltage Vdc) into three-phase AC voltage (U-phase output, V-phase output, W-phase output). For example, the current detected by the current detection unit DT1 from the U-phase output (U-phase current FB) is input (feedback) to the current vector control unit 20, and similarly, the current detected by the current detection unit DT2 from the V-phase output is input (feedback) to the current vector control unit 20. (V-phase current FB) is input (feedback) to the current vector control unit 20.

Next, the internal configuration of the current vector control section 20 will be described with reference to FIG. 4. FIG. 4 is a block diagram showing a detailed configuration example of the current vector control section 20. As shown in FIG. The current vector control section 20 includes at least a dq conversion section 21, a q-axis current control section 22, a d-axis current control section 23, and an inverse dq conversion section 24.

The dq conversion unit 21 converts each phase current i _u , i _v (U-phase current FB, V-phase current FB) detected by the current detection units DT1, DT2 and a rotor (not shown) detected by the encoder EN1. ), the d-axis current i _d and the q-axis current i _q , which are the d-axis and q-axis detection currents, are calculated. _The q-axis current iq is input to the q-axis current control section 22 as a q-axis current FB. The d-axis current i _d is input to the d-axis current control section 23 as a d-axis current FB.

The q-axis current control unit 22 generates an error that is the difference between the value of the q-axis current command i _q ^*, which is the target value of the q-axis current from the control unit 30, and the q-axis current i _q from the dq conversion unit 21. A q-axis voltage command v _q ^* is generated so that the voltage becomes zero. For example, the q-axis current control unit 22 performs proportional integration processing on the difference between the value of the q-axis current command i _q ^* and the value of the q-axis current i _q , and uses the result of the proportional integration as the q-axis voltage command v. Let _q ^* .

The d-axis current control unit 23 generates an error that is the difference between the value of the d-axis current command i _d ^*, which is the target value of the d-axis current from the control unit 30, and the d-axis current i _d from the dq conversion unit 21. A d-axis voltage command v _d ^* is generated so that the voltage becomes zero. For example, the d-axis current control unit 23 performs proportional integration processing on the difference between the value of the d-axis current command i _d ^* and the value of the d-axis current i _d , and uses the result of the proportional integration as the d-axis voltage command v Let it be _d ^* .

The inverse dq conversion unit 24 converts the q-axis voltage command v _q ^* from the q-axis current control unit 22, the d-axis voltage command v _d ^* from the d-axis current control unit 23, and the rotor signal detected by the encoder EN1. (not shown), voltage commands v _u ^* , v _v ^* , v _w ^* , which are PWM commands corresponding to the drive voltage applied to each phase of the motor MT1, are calculated and output to the PWM inverter circuit 10. .

Next, with reference to FIG. 5, the internal configuration of the control unit 30 for one axis will be described. FIG. 5 is a block diagram showing a detailed configuration example of the control unit 30 for one axis. The control unit 30 includes a PI (Proportional Integral) control unit 31, a q-axis current command limiter 32, an acceleration command calculation unit 33, a regeneration determination unit 34, an all-axis regeneration determination unit 35, a field weakening control unit 36, d-axis current command limiter 37.

The PI control unit 31 executes PI control based on the difference (deviation) between the value of the speed command for the motor MT1 from the outside and the feedback value of the rotational speed of the rotor of the motor MT1 calculated by the rotational speed calculation unit 40. do. For example, as PI control, the PI control unit 31 performs an addition operation of a term obtained by multiplying the difference by a constant as a proportional term and a value obtained by multiplying the value obtained by integrating the difference by a constant as an integral term. By performing this PI control, the PI control unit 31 generates a q-axis current command i _q ^* and outputs it to the q-axis current command limiter 32 .

The q-axis current command limiter 32 holds a predetermined q-axis current limit value corresponding to the rotational speed limit value of the motor MT1. When the q-axis current command limiter 32 determines that the value of the q-axis current command i _q ^* generated by the PI control unit 31 exceeds the q-axis current limit value, the q-axis current command limiter 32 changes the value of the q-axis current command i _q ^* A q-axis current command i _q ^* with q-axis current limit value is generated and output to the current vector control unit 20 . This q-axis current command i _q ^* is input to the q-axis current control section 22 of the current vector control section 20 .

The acceleration command calculation unit 33 calculates an acceleration command by performing time differentiation on the value of the speed command for the motor MT1 from the outside, and outputs the acceleration command to the regeneration determination unit 34. Note that in order to suppress noise components due to the influence of quantization errors of high frequency components in the time differentiation process, the acceleration command calculation unit 33 may include a filter FL1 for suppressing noise components.

The regeneration determination unit 34 determines the state of the motor MT1 based on the acceleration command from the acceleration command calculation unit 33 and the speed command of the motor MT1 from the outside, and uses the determination result as regeneration information to control the self-axis control unit 30. It is also output to the all-axis regeneration determining section 35 of the control section 30 for one or more other axes. Regarding the state determination of the motor MT1, specifically, if the regeneration determining unit 34 determines that the signs of the acceleration command and the speed command for a certain period (see FIG. 7) are the same, the motor MT1 is in power running. It is determined that the condition is the same. On the other hand, if the regeneration determination unit 34 determines that the signs of the acceleration command and the speed command for a certain period (see FIG. 7) are different, the regeneration determination unit 34 determines that the motor MT1 is in the regeneration state. The codes of the acceleration command and speed command for a certain period (see FIG. 7) will be described later with reference to FIG.

The all-axis regeneration determination unit 35 uses regeneration information from the regeneration determination unit 34 of the control unit 30 for its own axis and regeneration information from the regeneration determination unit 34 for one or more other axes to determine whether the multiple motors MT1 It is determined whether the entire manipulator MC1 is in a regenerative state or a power running state based on the state of the motor MT1 which has the highest load among them. For example, if the manipulator MC1 is a 6-axis articulated robot shown in FIG. , predetermined weighting is applied to the regeneration information for each axis, and when the weighted regeneration information (regeneration determination value) is larger than a predetermined threshold value, it is determined that the entire manipulator MC1 is in the regeneration state. The all-axis regeneration determination unit 35 generates a signal corresponding to the determination result and outputs it to the d-axis current command limiter 37.

Here, the regeneration determination value and weighting will be briefly explained.

The regeneration information from the regeneration determination unit 34 corresponding to one axis is 1 or 0. For example, if the regeneration information is 1, it indicates that the vehicle is in the regeneration state, and if the regeneration information is 0, it indicates that the vehicle is in the power running state. The all-axis regeneration determination unit 35 calculates a regeneration determination value according to the following (Formula 1). The magnitude of the weighting coefficient for each axis is determined in advance, for example, in light of the structure of the manipulator MC1. For example, in the case of the manipulator MC1 shown in Fig. 1, the load is applied as follows: 2nd axis > 3rd axis > 1st axis > 4th axis > 5th axis > 6th axis, so (weighting coefficient of 2nd axis) > (3rd axis weighting coefficient)>(1st axis weighting coefficient)>(4th axis weighting coefficient)>(5th axis weighting coefficient)>(6th axis weighting coefficient). Regarding the weighting coefficients, the weighting coefficient corresponding to the motor with the highest motor load has the largest value, and the weighting coefficient corresponding to the motor with the lowest motor load has the smallest value.

Regeneration judgment value = (1st axis weighting coefficient) x (1st axis regeneration information)
+ (2nd axis weighting coefficient) × (2nd axis regeneration information)
+ (3rd axis weighting coefficient) × (3rd axis regeneration information)
+ (4th axis weighting coefficient) × (4th axis regeneration information)
+ (5th axis weighting coefficient) × (5th axis regeneration information)
+ (6th axis weighting coefficient) × (6th axis regeneration information) (Formula 1)

The all-axis regeneration determination unit 35 determines that the entire manipulator MC1 is in the regeneration state when determining that the regeneration determination value obtained by the above-mentioned (Formula 1) is larger than a predetermined threshold value. On the other hand, when the all-axis regeneration determination unit 35 determines that the regeneration determination value obtained by the above-mentioned calculation formula is less than or equal to a predetermined threshold value, it determines that the entire manipulator MC1 is in the power running state.

The field weakening control unit 36 performs PI control based on the difference (deviation) between the feedback value of the rotation speed of the rotor of the motor MT1 calculated by the rotation speed calculation unit 40 and a predetermined value held in advance by the field weakening control unit 36. Execute. For example, as PI control, the field weakening control unit 36 performs an addition operation of a term obtained by multiplying the difference by a constant as a proportional term and a value obtained by multiplying the value obtained by integrating the difference by a constant as an integral term. By performing this PI control, the field weakening control unit 36 generates a d-axis current command i _d ^* and outputs it to the d-axis current command limiter 37 .

The d-axis current command limiter 37 holds a current limit value storage section M1. The current limit value storage unit M1 is a storage element (for example, a memory such as a ROM (Read Only Memory)) that holds a d-axis current limit 371 during regeneration and a d-axis current limit 372 during power running. The d-axis current command limiter 37 selects the d-axis current limit corresponding to the overall state of the manipulator MX1 (that is, the regenerative state or the power running state) based on the signal from the all-axis regeneration determining section 35. The d-axis current command limiter 37 selects a regeneration d-axis current limit 371 or a power running d-axis current limit 372 selected based on the signal from the all-axis regeneration determination unit 35 and a d-axis current command i from the field weakening control unit 36. Compare with _d ^* . The d-axis current command limiter 37 sets the d-axis current command i when it is determined that the d-axis current command i _d ^* from the field weakening control unit 36 exceeds the d-axis current limit 371 during regeneration or the d-axis current limit 372 during power running. _{A d} -axis current command i _d ^* in which d ^* is limited to the d-axis current limit 371 during regeneration or the d-axis current limit 372 during power running is generated and output to the current vector control unit 20. This d-axis current command i _d ^* is input to the d-axis current control section 23 of the current vector control section 20 .

Next, with reference to FIGS. 6 and 7, changes over time in the state of motor MT1 (that is, power running state or regenerative state) will be described. FIG. 6 is a diagram schematically showing changes in motor speed over time in a power running state and a regenerative state. FIG. 7 is a diagram illustrating an example of changes over time in speed commands and acceleration commands. In the upper graph of FIG. 6, the horizontal axis indicates time, and the vertical axis indicates motor speed (that is, rotational speed of motor MT1).

As shown in FIG. 6, while the rotational speed of the motor MT1 increases (rises) over time, the PWM inverter circuit 10 uses the power supply voltage Vdc, and based on this power supply voltage Vdc, the U-phase, V-phase, and W-phase Since each AC voltage is supplied (applied) to the motor MT1, the voltage decreases. Therefore, while the rotational speed of the motor MT1 increases (rises) over time, the state of the motor MT1 is in the power running state.

On the other hand, while the rotational speed of the motor MT1 decreases (falls) over time, the voltages converted to direct current from each of the U-phase, V-phase, and W-phase of the motor MT1 via the PWM inverter circuit 10 are applied to the power supply voltage Vdc side. Since the voltage is returned, the voltage will increase. Therefore, while the rotational speed of the motor MT1 decreases (falls) over time, the state of the motor MT1 is in the regenerative state.

The horizontal axis in FIG. 7 shows time, one of the vertical axes (on the left side of the paper) shows the value of the speed command from the outside, and the other vertical axis (on the right side of the paper) shows the value of the acceleration command calculated by the acceleration command calculating section 33. Show value. As shown in FIG. 7, the characteristic Y1 of the speed command and the characteristic Y2 of the acceleration command in the period PR1 have different signs for a certain period of time or more. For example, in period PR1, the acceleration command is almost stable at a negative steady value, but the speed command is decreasing from a positive value to zero over time.

Similarly, the characteristic Y1 of the speed command and the characteristic Y2 of the acceleration command in the period PR2 have different signs for a certain period of time or more. For example, in period PR2, the acceleration command is almost stable at a positive steady value, but the speed command is decreasing from a negative value to zero over time.

In this way, when the regeneration determination unit 34 determines that there is a period in which the signs of the characteristic Y1 of the speed command and the characteristic Y2 of the acceleration command are different for a certain period of time or more, the regeneration determining unit 34 determines that the period is in a regenerative state. That is, in the example of FIG. 7, the regeneration determination unit 34 determines that the state of the motor MT1 is in the regeneration state in each of the periods PR1 and PR2.

Next, with reference to FIG. 8, a procedure for determining the current limit value of the d-axis current command value of the robot control device 100 according to the present embodiment will be described. FIG. 8 is a flowchart showing the operation procedure for determining the current limit value of the d-axis current command value of the robot control device according to the present embodiment. The current limit value of the d-axis current command value referred to here is the d-axis current limit 371 during regeneration and the d-axis current limit 372 during power running. The flowchart shown in FIG. 8 is executed, for example, by each of six control units 30 provided corresponding to each axis of a six-axis articulated robot.

In FIG. 8, the first axis control unit 30 acquires the acceleration command from the acceleration command calculation unit 33 and the speed command of the motor MT1 from the outside for a certain period of time, and determines the sign of each of the certain period of time. (Step St11). If the control unit 30 of the first axis determines in step St11 that the acceleration command and the speed command have the same sign during the certain period (step St11, same sign), the state of the motor MT1 of the first axis is a power running state. information indicating that the regeneration information is 0 (that is, regeneration information = 0) is generated (step St21). On the other hand, if the control unit 30 of the first axis determines in step St11 that the acceleration command and the speed command have different signs during the certain period (step St11, different signs), the state of the motor MT1 of the first axis is Information indicating that it is in a regenerative state (that is, regenerative information=1) is generated (step St31). Further, the first axis control unit 30 selects a predetermined weighting coefficient α1 corresponding to the first axis (Step St41).

Similarly, the sixth axis control unit 30 obtains the acceleration command from the acceleration command calculation unit 33 and the speed command of the motor MT1 from the outside for a certain period of time, and determines the sign of each of the certain period of time. (Step St16). If the control unit 30 of the first axis determines in step St16 that the acceleration command and the speed command have the same sign during the certain period (step St16, same sign), the state of the motor MT1 of the sixth axis is a power running state. information indicating that the regeneration information is 0 (that is, regeneration information = 0) is generated (step St26). On the other hand, if the control unit 30 of the sixth axis determines in step St16 that the acceleration command and the speed command have different signs during the certain period (step St16, different signs), the state of the motor MT1 of the sixth axis is Information indicating that it is in a regenerative state (that is, regenerative information=1) is generated (step St36). Further, the sixth axis control unit 30 selects a predetermined weighting coefficient α6 corresponding to the sixth axis (Step St46).

The processes after step St5 are executed in parallel in each of the control units 30 for the first to sixth axes. For convenience of explanation, what the control unit 30 for the first axis performs will be described as an example, but each of the control units 30 for the second to sixth axes similarly executes the processes from step St5 onwards.

The control unit 30 of the first axis uses the weighting coefficient α1 and regeneration information selected by the control unit 30 of the own axis in step St41, and the control units 30 of each of the other axes (that is, the second to sixth axes). Obtain the selected weighting coefficient and regeneration information. The control unit 30 of the first axis uses the weighting coefficient α1 selected in step St41 by the control unit 30 of the own axis and the integration result of the regeneration information, and controls each of the other axes (that is, the second to sixth axes). A regeneration determination value is calculated by adding the weighting coefficient selected by the unit 30 and the integration result of the regeneration information (see step St5, (Equation 1)).

When the first-axis control unit 30 determines that the regeneration determination value calculated in step St5 is greater than a predetermined threshold value (step St6, greater than the threshold value), the first-axis control unit 30 determines that the entire manipulator MC1 is in a regenerative state. In this case, the first axis control unit 30 selects the d-axis current limit 371 during regeneration (step St7). The first axis control unit 30 generates a d-axis current command i _{d * according to the comparison result between the d-axis current limit 371 during regeneration and the d-axis current command i d} ^* _from ^the field weakening control unit 36, and generates a current vector. It is output to the control section 20.

On the other hand, when the first-axis control unit 30 determines that the regeneration determination value calculated in step St5 is less than or equal to the predetermined threshold value (step St6, less than the threshold value), the first-axis control unit 30 determines that the entire manipulator MC1 is in the power running state. . In this case, the first axis control unit 30 selects the d-axis current limit 372 during power running (Step St8). The first axis control unit 30 generates a d-axis current command i _{d * according to the comparison result between the d-axis current limit 372 during power running and the d-axis current command i d} ^* _from ^the field weakening control unit 36, and generates a current vector. It is output to the control section 20.

As described above, the robot control device 100 according to the present embodiment has each axis current calculation unit (for example, control unit 30), and a voltage command value calculation unit (for example, q axis current control section 22, d-axis current control section 23), a drive circuit (for example, PWM inverter circuit 10) that outputs a plurality of drive powers to a plurality of motors based on a plurality of voltage command values, and a speed command value. an acceleration command value calculation unit (for example, acceleration command calculation unit 33) that calculates an acceleration command value based on the speed command value and a regeneration determination unit that determines either the power running state or the regeneration state based on the speed command value and the speed command value. 34, a first current limit value that is the current limit value of the d-axis current command value in the power running state (for example, the d-axis current limit 372 during power running), and a second current limit value that is the current limit value of the d-axis current command value in the regenerative state. A current limit value storage M1 that stores a current limit value (for example, the d-axis current limit 371 during regeneration), and outputs a d-axis current command value that is equal to or less than the first current limit value in the power running state, and A d-axis current command value limiting section (for example, a d-axis current command limiter 37) that outputs a d-axis current command value that is equal to or less than two current limit values is provided. The regeneration determination unit (for example, the all-axis regeneration determination unit 35) determines either the power running state or the regeneration state based on the state of the motor with the highest load among the plurality of motors.

Further, the motor control method by the robot control device 100 according to the present embodiment includes the steps of calculating the q-axis current command value and the d-axis current command value based on the speed command value notified from the outside, and the step of calculating the q-axis current command value and the d-axis current command value based on the speed command value notified from the outside. a step of calculating an acceleration command value based on the speed command value and an acceleration command value, a step of determining either the power running state or the regeneration state based on the speed command value and the acceleration command value, and a step of calculating the current limit value of the d-axis current command value in the power running state. A d-axis current command value that is less than or equal to a certain first current limit value (for example, the d-axis current limit 372 during power running) is output, and a second current limit value that is the current limit value of the d-axis current command value in the regenerative state (for example, regenerative a step of outputting a d-axis current command value that is equal to or less than the d-axis current limit 371); and a step of outputting a d-axis current command value that is less than or equal to The method includes a step of calculating a voltage command value, and a step of outputting a plurality of drive powers to the plurality of motors based on the plurality of voltage command values. The determination of whether the motor is in the power running state or the regenerative state is performed based on the state of the motor with the highest load among the plurality of motors MT1.

In order to operate the motor MT1 at high speed and high load (in other words, high torque), it is necessary to reduce the influence of the induced voltage component generated in the motor MT1 during high-speed operation. To achieve this, in the prior art, a d-axis current (in other words, a reactive current) is passed to ensure a q-axis current component, which is a motor drive component. However, when the d-axis current increases, the current flowing through the motor MT1 increases, and as a result, the motor MT1 itself generates heat. Further, since the servo motor such as the motor MT1 is equipped with the encoder EN1 and is affected by the heat generated by the motor, it is desirable to suppress the heat generated as much as possible. From the above, it is required to suppress the heat generation of the motor MT1 while properly securing the d-axis current.

Scenes where a large amount of d-axis current must flow at high speed and high load (in other words, high torque) are in the power running state (in other words, the direction of rotation of motor MT1 and the current direction are the same), and in the regenerative state (in other words, , the rotational direction of the motor MT1 is different from the current direction), the operation is possible without the need to flow the d-axis current to that extent. However, when the manipulator MC1 operates with a plurality of axes (for example, six axes), the magnitude of the load applied to the motor MT1 differs for each axis, so the required d-axis current component also differs.

Therefore, according to the present embodiment, the robot control device 100 controls the manipulator MC1 by determining whether the state of the motor MT1 corresponding to the axis with the highest load among the plurality of motors MT1 is the power running state or the regeneration state. When the motor MT1 is considered to be in a regenerative state, the heat generation of the motor MT1 is reduced by limiting the d-axis current command value. As a result, the robot control device 100 can select the current limit value of the d-axis current command value according to the power running state and the regeneration state in a robot equipped with a plurality of motors MT1 such as the manipulator MC1. Even in this state, high-speed, high-load operation of each motor can be efficiently realized.

Further, the regeneration determination section (for example, the all-axis regeneration determination section 35) determines either the power running state or the regeneration state based on a plurality of regeneration determination values corresponding to each of the plurality of motors MT1. As a result, the robot control device 100 can change the power running state or Condition can be determined accurately.

Further, the regeneration determination unit (for example, the all-axis regeneration determination unit 35) weights each of the plurality of regeneration determination values, and determines either the power running state or the regeneration state based on the weighted plurality of regeneration determination values. . As a result, the robot control device 100 appropriately weights the motors MT in consideration of the influence of the load on the motors MT, such as a motor with a high load and a motor with a low load among the plurality of motors MT1 mounted on the manipulator MC1. The power running state or regeneration state of the manipulator MC1 as a whole can be determined with high precision so as to match the state of the motor with the highest load.

Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is clear that those skilled in the art can come up with various changes, modifications, substitutions, additions, deletions, and equivalents within the scope of the claims, and It is understood that it naturally falls within the technical scope of the present disclosure. Further, each of the constituent elements in the various embodiments described above may be arbitrarily combined without departing from the spirit of the invention.

The present disclosure is useful as a motor control device and a motor control method that efficiently realize high-speed, high-load operation of each motor in a robot equipped with a plurality of motors.

10 PWM inverter circuit 20 current vector control section 21 d-q conversion section 22 q-axis current control section 23 d-axis current control section 24 inverse d-q conversion section 30 control section 31 PI control section 32 q-axis current command limiter 33 acceleration command Calculation unit 34 Regeneration determination unit 35 All-axis regeneration determination unit 36 Field weakening control unit 37 d-axis current command limiter 40 Rotation speed calculation unit 100 Robot control device 371 d-axis current limit during regeneration 372 d-axis current limit during power running 1000 Welding robot system DT1 , DT2 Current detection section EN1 Encoder M1 Current limit value storage section MC1 Manipulator MT1 Motor

Claims (4)

each axis current calculation unit that calculates a q-axis current command value and a d-axis current command value based on a speed command value notified from the outside;
a voltage command value calculation unit that calculates a plurality of voltage command values, which are values of voltages to be respectively applied to the plurality of motors, based on the q-axis current command value and the d-axis current command value;
a drive circuit that outputs a plurality of drive powers to the plurality of motors based on the plurality of voltage command values;
an acceleration command value calculation unit that calculates an acceleration command value based on the speed command value;
a regeneration determination unit that determines either a power running state or a regeneration state based on the speed command value and the acceleration command value;
A current that stores a first current limit value that is a current limit value of the d-axis current command value in the power running state, and a second current limit value that is a current limit value of the d-axis current command value in the regeneration state. a limit value storage section;
a d-axis current command value that outputs the d-axis current command value that is less than or equal to the first current limit value in the power running state, and outputs the d-axis current command value that is less than or equal to the second current limit value in the regenerative state; a restriction part;
The regeneration determination unit determines either the power running state or the regeneration state based on the state of the motor with the highest load among the plurality of motors.
Motor control device. The regeneration determination unit determines either the power running state or the regeneration state based on a plurality of regeneration determination values corresponding to each of the plurality of motors.
The motor control device according to claim 1. The regeneration determination unit weights each of the plurality of regeneration determination values, and determines either the power running state or the regeneration state based on the weighted plurality of regeneration determination values.
The motor control device according to claim 2. calculating a q-axis current command value and a d-axis current command value based on a speed command value notified from the outside;
calculating an acceleration command value based on the speed command value;
determining either a power running state or a regeneration state based on the speed command value and the acceleration command value;
Outputting the d-axis current command value that is less than or equal to a first current limit value that is a current limit value of the d-axis current command value in the power running state, and outputting the d-axis current command value that is a current limit value of the d-axis current command value in the regeneration state. outputting the d-axis current command value that is equal to or less than a second current limit value;
calculating a plurality of voltage command values, which are voltage values to be applied to the plurality of motors, based on the q-axis current command value and the d-axis current command value;
outputting a plurality of driving powers to the plurality of motors based on the plurality of voltage command values, respectively;
The determination of either the power running state or the regeneration state is performed based on the state of the motor with the highest load among the plurality of motors.
Motor control method.

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