CN113285644B

CN113285644B - Motor control method, motor drive device, control method for industrial robot, and industrial robot

Info

Publication number: CN113285644B
Application number: CN202110101850.0A
Authority: CN
Inventors: 花冈正志
Original assignee: Nidec Sankyo Corp
Current assignee: Nidec Sankyo Corp
Priority date: 2020-02-04
Filing date: 2021-01-26
Publication date: 2024-05-07
Anticipated expiration: 2041-01-26
Also published as: KR102567726B1; KR20210099518A; CN113285644A; JP2021125950A; JP7428527B2

Abstract

The invention provides a motor control method, which stops the rotation of a motor through open loop control, and prevents the motor from losing step and vibrating caused by insufficient torque. In open loop control, it includes: a step of obtaining a torque required by the motor based on a position command value sent from the upper controller; a step of obtaining a Q-axis current command value corresponding to the torque; and a step of supplying a Q-axis current corresponding to the Q-axis current command value and a D-axis current for a magnetic pole of a magnet for introducing the rotor to the motor.

Description

Motor control method, motor drive device, control method for industrial robot, and industrial robot

Technical Field

The present invention relates to a motor control method, a motor drive device, a control method for an industrial robot, and an industrial robot.

Background

Conventionally, a motor control method for driving a motor by open loop control is known.

For example, in the motor control method described in patent document 1, the motor is started by open loop control by forced commutation (current drawing method). At this time, a constant D-axis current is supplied to the motor, and the Q-axis current is maintained at zero. After that, when the angular velocity of the motor is increased until a sufficient induced voltage can be obtained in the motor, the control mode is switched from open loop control to sensorless vector control in which the rotational position of the motor is estimated based on the current detection value.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2008-11628

Disclosure of Invention

Technical problem to be solved by the invention

Patent document 1 does not describe how to specifically operate when stopping rotation of the motor. In the motor control method described in patent document 1, it is considered that, in normal driving of the motor, the rotational position of the motor is controlled by sensorless vector control, and therefore, when the motor is stopped, the rotational position of the motor is controlled while the rotation is decelerated and stopped. Specifically, the rotation of the motor is decelerated by sensorless vector control until a sufficient induced voltage cannot be obtained in the motor, and thereafter, the control system is switched to open loop control to stop the rotation.

However, according to experiments by the present inventors, if the open loop control described in patent document 1 is used, the motor is out of step or vibrated due to excessive or insufficient torque.

Although the technical problem that occurs when the control system of the motor is switched from the sensorless vector control to the open loop control has been described, the same problem occurs in the following configuration. That is, the control method is switched from feedback control in which a detected value of the rotational position of the motor by the encoder or the like is fed back to open loop control.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a motor control method, a motor driving device, a control method for an industrial robot, and an industrial robot as described below. That is, the motor control method can stop the rotation of the motor by the open loop control without occurrence of the step-out and the vibration of the motor due to the excessive or insufficient torque.

Technical proposal adopted for solving the technical problems

A first aspect of the present application provides a motor control method for driving a motor by open loop control based on a current lead-in method, comprising: a step of obtaining a torque required for the motor based on the rotational position command signal transmitted from the signal transmission unit; a step of obtaining a Q-axis current command value corresponding to the torque; and supplying a Q-axis current corresponding to the Q-axis current command value and a D-axis current for a magnetic pole of a magnet to be introduced into the rotor to the motor.

A second aspect of the present application provides a motor driving device for controlling driving of a motor, wherein the driving of the motor is controlled by the motor control method of the first aspect.

A third aspect of the present application provides a control method of an industrial robot that controls driving of a plurality of motors independently to change a position of an arm of the industrial robot, wherein driving of each of the plurality of motors is controlled by the motor control method of the first aspect.

A fourth aspect of the present application provides an industrial robot that controls driving of a plurality of motors independently to change a position of an arm, wherein driving of each of the plurality of motors is controlled by a motor driving device of the second aspect.

Effects of the invention

According to these inventions, the following excellent effects are obtained: the rotation of the motor can be stopped by the open loop control without occurrence of a step-out or a vibration of the motor due to an excessive or insufficient torque.

Drawings

Fig. 1 is a perspective view showing an industrial robot according to an embodiment.

Fig. 2 is a plan view showing the same industrial robot.

Fig. 3 is a block diagram showing a control structure of a motor driving device mounted on the same industrial robot together with a motor or the like.

Fig. 4 is a flowchart showing a flow of processing of the mode value selection processing executed by the control mode selection unit of the same motor drive apparatus.

Fig. 5 is a block diagram showing an open-loop control electric angle generating unit of the same motor driving device.

Fig. 6 is a graph showing a relationship between a position command value and an actual rotation position of a hand based on control in response to the position command value.

Fig. 7 is a graph showing time changes of various states in the conventional open loop control.

Fig. 8 is a graph showing time variations of various states in a method of determining a Q-axis current command value after the start of open-loop control based on a torque command value before the start of open-loop control.

Fig. 9 is a block diagram showing a control configuration of an open-loop control DQ-axis current command generation unit of the same motor driving apparatus.

Fig. 10 is a graph showing a relationship between a Q-axis current command value and a D-axis current command value in the same motor driving device.

Detailed Description

Embodiments of a motor driving device and an industrial robot using a motor control method according to an embodiment of the present invention will be described below with reference to the drawings. In the following drawings, the actual structure, the scale and the number of the structures may be different for easy understanding of the structures.

First, a basic configuration of the industrial robot according to the embodiment will be described. Fig. 1 is a perspective view showing an industrial robot 1 according to an embodiment. Fig. 2 is a plan view showing the industrial robot 1. The industrial robot 1 is a robot for conveying a glass substrate, and includes an arm 2, a stand 3, and a lifting unit 4. The lifting unit 4 is held by the stand 3 and is lifted and lowered in the vertical direction (arrow direction in fig. 1) by driving a lifting motor (not shown). The arm 2 includes a hand 2A for placing a glass substrate, a front arm 2B, and an upper arm 2C, and is held by a lifting unit 4.

The shoulder joint 2D, which is a connection portion with the lifting portion 4, in the upper arm portion 2C is rotatable in the horizontal direction by driving of the first motor 22A. Specifically, the rotational driving force of the first motor 22A is transmitted to the shoulder joint 2D via the first conveyor belt 2E, whereby the shoulder joint 2D rotates in the horizontal direction. In addition, the elbow joint 2F, which is a connection portion between the upper arm portion 2C and the forearm portion 2B, is rotatable in the horizontal direction by driving of the second motor 22B. Specifically, the rotational driving force of the second motor 22B is transmitted to the elbow joint 2F via the second conveyor belt 2G, whereby the elbow joint 2F rotates in the horizontal direction. Further, the wrist joint, which is the connection between the forearm portion 2B and the hand portion 2A, receives the driving force of the second motor 22B via the conveyor belt, and is thereby rotatable in the horizontal direction.

In the industrial robot 1, in order to move the hand 2A straight in the arrow direction along the trajectory shown by the chain line in fig. 2, it is necessary to rotate the two joints by setting the angles of the shoulder joint 2D and the elbow joint 2F to a ratio of 1 to 2. For this reason, the first motor 22A and the second motor 22B need to be driven in mutually different driving amounts. When the two motors are stopped without controlling the respective rotational positions of the first motor 22 and the second motor 22B, the balance of the driving amounts of the two motors will be broken, resulting in the hand 2A being stopped at a position deviated from the orbit indicated by the chain line. Then, the hand 2A may collide with surrounding structures, devices, or the like.

Next, a motor driving device using the motor control method according to the embodiment will be described.

Fig. 3 is a block diagram showing a control structure of the motor driving device 20 mounted on the industrial robot 1 according to the embodiment, together with the motor 22 and the like. The industrial robot 1 includes three motor driving devices, i.e., a motor driving device 20 for rotating the shoulder joint 2D of the arm 2, a motor driving device 20 for rotating the elbow joint 2F and the wrist joint of the arm 2, and a motor driving device 20 for raising and lowering the raising and lowering unit 4, as the motor driving devices 20 shown in fig. 3.

The three motor driving devices 20 can be switched and perform three controls, i.e., a detection position feedback control, a sensorless vector control, and an open loop control, respectively, as control modes of driving the motor 22. The detected position feedback control is control for generating a command to feed back the result of detecting the rotational position of the motor to the rotational position.

The industrial robot 1 includes a host controller 100 that transmits commands to the three motor driving devices 20. The upper controller 100 transmits a position command value (rotational position command signal) to each of the three motor driving devices 20 based on a control program stored in a storage medium. The three motor driving devices 20 each perform control to rotate the rotor of the motor 22 to a rotational position corresponding to the position command value sent from the upper controller 100. By this control, the arm 2 of the industrial robot 1 performs an operation based on the control program.

The three motor driving devices 20 are identical in structure to each other. Accordingly, only the structure of one of the three motor driving devices 20 will be described in detail below.

The motor drive device 20 includes a control mode selection unit 21, a position speed control unit 23, a vector control DQ-axis current command generation unit 24, a first selector 25, a current control unit 26, a DQ inverse conversion unit 27, a PWM control unit 28, and an inverter 29. The motor 22 driven by the motor driving device 20 is the first motor 22A, the second motor 22B, or the third motor described above. The motor drive device 20 includes a current detection unit 31, a second selector 32, a vector control electrical angle generation unit 33, a third selector 34, a position estimation unit 35, and an open loop control electrical angle generation unit 36. The motor drive device 20 further includes an open-loop control DQ-axis current command generation unit 37, an encoder communication abnormality determination unit 38, and a DQ conversion unit 39. The motor unit includes a motor 22 and a rotary encoder 30.

The position command value output from the upper controller 100 is input to the position speed control unit 23 and the open loop control electric angle generation unit 36 of the motor drive device 20.

The motor 22, which is a driving source for the rotation operation (rotation of the shoulder joint 2D), the joint bending and extending operation (rotation of the shoulder joint 2D, the elbow joint 2F, and the wrist joint), or the lifting operation of the arm 2 of the industrial robot 1, is constituted by a three-phase (U-phase, V-phase, W-phase) ac PM (PERMANENT MAGNET: permanent magnet) motor. The rotary encoder 30, which is a rotary position detector mounted on the motor 22, detects the rotary position of the rotor of the motor 22 by a well-known technique. Then, the rotary encoder 30 outputs information of the detection result of the rotational position as a position detection value (rotational position signal). The output position detection value is input to the encoder communication abnormality determination unit 38 and the control mode selection unit 21. The position detection value is also input to the position and speed control unit 23 via the second selector 32.

In the following, the rotation of the rotor of the motor 22 may be expressed as the rotation of the motor 22.

The encoder communication abnormality determination unit 38 detects the presence or absence of an abnormality in the position detection value transmitted from the rotary encoder 30, and transmits an abnormality occurrence signal to the control mode selection unit 21 and the upper controller 100 when the abnormality is detected. As an example of a method of detecting an abnormality of the position detection value by the encoder communication abnormality determination unit 38, a method of detecting an abnormality when the time variation of the position detection value exceeds a predetermined threshold (or is equal to or greater than a threshold) is given. But is not limited to this method. As a method of detecting an abnormality of the position detection value, a method of detecting an abnormality of the rotary encoder 30 as an abnormality of the position detection value may be employed.

The control mode selecting unit 21 calculates the angular velocity of the motor 22 based on the amount of change per unit time of the position detection value transmitted from the rotary encoder 30, and selects and outputs a control mode value based on the calculation result and the presence or absence of abnormality of the position detection value.

Fig. 4 is a flowchart showing a flow of processing of the mode value selection processing executed by the control mode selection unit 21. In the mode value selection process, first, it is determined whether or not an abnormality occurrence signal transmitted from the encoder communication abnormality determination section 38 as needed has been received (S (step) 1). Then, when the abnormality occurrence signal is not received (N in S1), 0 is selected as the control mode value and outputted from the control mode selection unit 21 (S2). After that, the process flow returns to S1.

On the other hand, when the abnormality occurrence signal is received (Y in S1), it is then determined whether or not the angular velocity of the motor 22 is equal to or higher than a predetermined value (or exceeds a predetermined value) (S3). When the angular velocity is equal to or greater than the predetermined value (Y in S3), a control mode value of "1" is selected and outputted from the control mode selection unit 21 (S4). On the other hand, when the angular velocity is not equal to or higher than the predetermined value (or when the angular velocity is not higher than the predetermined value) (N in S3), the control mode value "2" is selected and outputted from the control mode selecting unit 21. Hereinafter, the predetermined value may be expressed as a lower limit value.

As described above, in the control mode value selection process, when no abnormality of the position detection value occurs, "0" is selected as the control mode value. When an abnormality in the position detection value occurs and the angular velocity is equal to or greater than a predetermined value, "1" is selected as the control mode value, and when an abnormality in the position detection value occurs and the angular velocity is not equal to or greater than a predetermined value, "2" is selected as the control mode value.

The predetermined value is, for example, 10% of the rated angular velocity of the motor 22.

When an abnormality occurrence signal is transmitted from the motor drive device 20, the upper controller 100 changes the position command values transmitted to the three motor drive devices 20 in a mode in which the arm 2 and the motor 22 are decelerated and stopped while the arm 2 is moved on a predetermined track. Thereby, the arm 2 is decelerated and stopped on a predetermined track.

In fig. 3, the control mode value output from the control mode selection unit 21 is input to each of the first selector 25, the second selector 32, and the third selector 34 (hereinafter, these will be collectively referred to as three selectors (25, 32, 34)). The three selectors (25, 32, 34) each have a number 0 input terminal, a number 1 input terminal, and a number 2 input terminal, and switch the output signals based on the control mode value sent from the control mode selection unit 21. Specifically, the three selectors (25, 32, 34) output signals to be input to the input terminal No. 0 when the control mode value is "0", output signals to be input to the input terminal No. 1 when the control mode value is "1", and output signals to be input to the input terminal No. 2 when the control mode value is "2", respectively.

The following signals are outputted from each of the three selectors (25, 32, 34) of the above-described structure. That is, when no abnormality of the position detection value occurs (control mode value=0), a signal for executing the detection position feedback control for rotating the motor 22 from the position indicated by the position detection value to the position indicated by the position command value is output. When an abnormality in the position detection value occurs and the angular velocity of the motor 22 is equal to or higher than a predetermined value (or exceeds a predetermined value) (control mode value=1), a signal for driving the motor 22 by sensorless vector control described later is output. When abnormality of the position detection value occurs and the angular velocity of the motor 22 is lower than a predetermined value (or equal to or lower than a predetermined value) (control mode value=2), a signal for driving the motor 22 by open loop control described later is outputted.

First, detection position feedback control in the three control modes described above will be described.

In the case where the position detection value output from the rotary encoder 30 is not abnormal, the motor driving device 20 drives the motor 22 by detecting the position feedback control. Specifically, when there is no abnormality in the position detection value, the position detection value is output from the second selector 32 and input as a position feedback value to the position speed control unit 23 and the vector control electric angle generation unit 33. The position and speed control unit 23 calculates a torque value required to rotate the motor 22 from a position indicated by the position feedback value to a position indicated by the position command value, and outputs the result as a torque command value to the vector control DQ axis current command generation unit 24. The vector control electrical angle generating unit 33 generates an electrical angle based on the position feedback value. The electrical angle is input to the DQ conversion section 39 via the third selector 34.

The vector control DQ-axis current command generating unit 24 generates a D-axis current command value and a Q-axis current command value (hereinafter, these will also be referred to as DQ-axis current command values) for generating a D-axis current and a Q-axis current, which are currents necessary for generating the same torque as the input torque value, in the motor 22. The D-axis current is a component parallel to the magnetic flux of the permanent magnet in the current flowing through the motor 22. In addition, the Q-axis current is a component orthogonal to the magnetic flux of the permanent magnet in the current flowing through the motor 22.

The DQ axis current command value outputted from the vector control DQ axis current command generation unit 24 is inputted to the No. 0 input terminal and the No.1 input terminal of the first selector 25. In the case of performing the detection position feedback control (control mode value=0) and the case of performing the sensorless vector control (control mode value=1), the DQ-axis current command value generated by the vector control DQ-axis current command generating section 24 is output from the first selector 25. The DQ axis current command value is input to the current control unit 26.

The DQ conversion unit 39 generates a D-axis current feedback value and a Q-axis current feedback value (hereinafter, also referred to as DQ-axis current feedback values) based on the electrical angle transmitted from the third selector 34, and outputs the values to the current control unit 26. In addition, during sensorless vector control described later, the DQ conversion section 39 generates a DQ-axis current feedback value based on the electrical angle transmitted from the third selector 34 and the three-phase current detection value transmitted from the current detection section 31.

The current control unit 26 generates a DQ-axis voltage command value based on the DQ-axis current command value sent from the first selector 25 and the DQ-axis current feedback value sent from the DQ conversion unit 39, and outputs the DQ-axis voltage command value to the DQ inverse conversion unit 27.

The DQ inverse conversion unit 27 generates and outputs U-phase, V-phase, and W-phase voltage command values (hereinafter also referred to as three-phase voltage command values) for generating the requested D-axis current and Q-axis current in the motor 22 based on the electrical angle transmitted from the third selector 34 and the DQ-axis voltage command value transmitted from the current control unit 26. The three-phase voltage command value output from the DQ inverse conversion unit 27 is input to the PWM control unit 28. The PWM control unit 28 generates a U-phase gate signal, a V-phase gate signal, and a W-phase gate signal, each of which is configured by a PWM signal for causing the inverter 29 to output a U-phase voltage, a V-phase voltage, and a W-phase voltage indicated by the U-phase voltage command value, the V-phase voltage command value, and the W-phase voltage command value. The inverter 29 supplies the motor 22 with a U-phase voltage, a V-phase voltage, and a W-phase voltage based on the U-phase gate signal, the V-phase gate signal, and the W-phase gate signal, to rotate the motor 22.

The current detection unit 31 detects a U-phase current, a V-phase current, and a W-phase current (hereinafter, these will be also referred to as three-phase currents) flowing from the inverter 29 to the motor 22, and outputs the detection results as a U-phase current detection value, a V-phase current detection value, and a W-phase current detection value (hereinafter, also referred to as three-phase current detection value). Instead of detecting the current values of three phases, only the current values of two phases of the three phases may be detected, and the current value of the remaining one phase may be calculated based on the detection result of the current values of two phases.

In the case where the position detection value output from the rotary encoder 30 is not abnormal, the motor 22 is driven by the detected position feedback control as described above.

Next, sensorless vector control will be described. When the sensorless vector control is executed, that is, when there is an abnormality in the position detection value and the angular velocity of the motor 22 immediately before the occurrence of the abnormality is equal to or greater than a predetermined value (or exceeds a predetermined value) (control mode value=1), the motor 22 is driven as follows. That is, the three-phase current detection value output from the current detection unit 31 is input to the DQ conversion unit 39. The DQ conversion unit 39 generates and outputs a DQ-axis current feedback value based on the three-phase current detection value and the electrical angle transmitted from the third selector 34. The output DQ-axis current feedback value is input to the current control unit 26 and the position estimation unit 35.

The current control unit 26 generates and outputs a DQ-axis voltage command value based on the DQ-axis current command value sent from the first selector 25 and the DQ-axis current feedback value sent from the DQ conversion unit. The position estimation unit 35 estimates the rotational position of the motor 22 based on the DQ-axis voltage command value sent from the current control unit 26 and the DQ-axis current feedback value sent from the DQ conversion unit 39.

The position estimation unit 35 obtains a position estimation value and an electrical angle estimation value based on the DQ-axis current feedback value sent from the DQ conversion unit 39 and the DQ-axis voltage command value sent from the current control unit 26. Then, the position estimating section 35 outputs the position estimated value to the No. 1 input terminal of the second selector 32, and outputs the electrical angle estimated value to the No. 1 input terminal of the third selector.

The position estimation value output from the position estimation unit 35 is input to the position speed control unit 23 as a position feedback value via the second selector 32. The position/speed control unit 23 outputs a torque command value in the same manner as in the detection position feedback control, except that the position estimated value is used as the position feedback value. The processing until the U-phase gate signal, the V-phase gate signal, and the W-phase gate signal, which are the torque command values, are input to the inverter 29 is the same as the detection position feedback control. That is, in the sensorless vector control, the same processing as in the detected position feedback control is performed except that a position estimation value based on the induced voltage generated in the motor 22 is fed back to the position speed control unit 23 as a position feedback value instead of the position detection value.

In addition, in the sensorless vector control, the motor drive apparatus 20 reduces the control loop gain of the position and speed control as compared with the detection position feedback control. As an example of a method for reducing the control loop gain, a method for reducing the control loop gain by an instruction of the higher-level controller 100 is given. In order to accurately maintain the trajectory of the arm 2, it is preferable to reduce the control loop gain of the position speed control of the motor drive device 20 in which the abnormality in the position detection value occurs, as well as the control loop gain of the position speed control of the other motor drive devices 20. The control loop gain of the position speed control in all the motor driving devices 20 can be appropriately reduced according to the instruction of the upper controller 100.

As another example of reducing the control loop gain of the position speed control of the motor drive apparatus 20, the following method is given: by the processing of the motor drive device 20 that causes abnormality in the position detection value, only the control loop gain of the position speed control of the motor drive device 20 is reduced. As an example of the processing of this method, the following method can be given: in a structure in which the rotational position and the angular velocity are controlled by P-PI control, the speed loop gain, the position loop gain, and the speed loop integral gain are reduced, respectively. Further, as another example, the following method may be mentioned: for example, in the configuration in which the rotational position and angular velocity are controlled by RPP control described in japanese patent application laid-open No. 2002-229604, the gain ω ₂, the gain ω ₁, and the gain ω _q are reduced. Further, as another example, the following method may be mentioned: in a structure in which the rotational position and angular velocity are controlled by RPP control, the inertia nominal set value is lowered. By lowering the inertial nominal set point, the ω ₂ gain, ω ₁ gain can be reduced approximately. According to this method, the control loop gain can be appropriately reduced without constructing a dedicated program for reducing the control loop gain.

Next, the ring opening control will be described. When the open-loop control is executed, that is, when there is an abnormality in the position detection value and the angular velocity of the motor 22 is less than a predetermined value (or equal to or less than a predetermined value) (control mode value=2), the motor 22 is driven as follows. That is, the open-loop control electric angle generating unit 36 calculates the rotational position of the magnetic pole of the attraction motor 22 (hereinafter, referred to as a forced synchronization position command value) based on the position command value sent from the upper controller 100, and outputs the calculated rotational position to the open-loop control DQ-axis current command generating unit 37. Further, an electrical angle estimated value is calculated based on the position command value and output to the third selector 34.

When the control mode is switched to the detection position feedback control or the sensorless vector control, the electric angle of the motor 22 is switched from the angle indicated by the position detection value or the position estimation value to the initial angle for performing the open-loop control. At this time, if the direction of the DQ-axis current vector flowing through the motor 22 is instantaneously switched from the Q-axis direction to the positive direction of the D-axis direction, the following disadvantage occurs. That is, torque for moving the machine to be driven (the entire arm 2, the hand 2A, the forearm portion 2B, or the upper arm portion 2C) using the motor 22 as a driving source cannot be obtained, and the motor 22 is out of step or greatly vibrated.

Therefore, the open-loop control electrical angle generating unit 38 shown in fig. 3 generates the electrical angle so that the rotational position of the motor 22 changes with time, as in the case of executing the detection position feedback control.

Fig. 5 is a block diagram showing the open-loop control electric angle generating unit 36. The open-loop control electrical angle generating unit 36 includes a controller 36a, an electrical system/mechanical system model 36b, and an electrical angle calculating unit 36c.

The controller 36a includes a position and speed control unit 36a1, a vector control DQ-axis current command generation unit 36a2, a current control unit 36a3, a DQ inverse conversion unit 36a4, a PWM control unit 36a5, and a DQ conversion unit 36a6. The position and velocity control unit 36a1 shown in fig. 5 performs the same processing as the position and velocity control unit 23 shown in fig. 3. The vector control DQ axis current command generation unit 36a2 shown in fig. 5 performs the same processing as the vector control DQ axis current command generation unit 24 shown in fig. 3. The current control unit 36a3 shown in fig. 5 performs the same processing as the current control unit 26 shown in fig. 3. The DQ inverse conversion unit 36a4 shown in fig. 5 performs the same processing as the DQ inverse conversion unit 27 shown in fig. 3. The PWM control section 36a5 shown in fig. 5 performs the same processing as the PWM control section 28 shown in fig. 3. The DQ conversion unit 36a6 shown in fig. 5 performs the same processing as the DQ conversion unit 39 shown in fig. 3.

The model 36b of the electric system/mechanical system includes a model of the inverter 36b1, a model of the motor 36b2, and a model of the load machine 36b5 for the motor. These models are provided with the following algorithm: for each of the U-, V-, and W-phases, when the gate signal changes from a pre-change value to a post-change value, it is simulated how the rotational position of the motor 22 and the value of the current flowing through the motor 22 change. The position simulation value obtained by the simulation is output from the model of the rotary encoder 36b4, and is input to the position speed control unit 36a1, the electrical angle calculation unit 36c, and the open-loop control DQ-axis current command generation unit 37 in fig. 3 of the controller 36 a.

The electrical angle calculation unit 36c in fig. 5 calculates the electrical angle of the motor 22 based on the position analog value, and outputs the result to the DQ inverse conversion unit 27 and the DQ conversion unit 39 in fig. 3.

When abnormality occurs in the position detection value, the control mode is switched from the detected position feedback control or the sensorless vector control to the open loop control, and then the motor can be operated by the same behavior as that in the case of performing the position detection value. Thus, according to the motor control method according to the embodiment, the occurrence of the motor step-out and the vibration caused by the abrupt change in the electric angle after the control mode is switched to the open-loop control can be suppressed.

Instead of simulating the rotational position of the motor 22 and the current value supplied to the motor 22, only the rotational position of the motor 22 may be simulated. In this case, the position and speed control unit 36a1 may perform a process of obtaining a required torque command value based on the position command value and the position simulation value, and input the obtained torque command value to the model 36b of the machine system to obtain the position simulation value.

Instead of simulating the rotational position of the motor, the position command value may be converted into the rotational position of the motor 22 after the position detection value in response to the position feedback control performed virtually by the position control response transfer function G(s). In the method of obtaining the position conversion value using the position control response transfer function G(s), regarding the position command value, it is determined with what delay is reflected in what rotational position in the actual control by the position control response transfer function G(s) as the position conversion value. The obtained position conversion value may be output to the DQ inverse conversion unit 27 and the DQ conversion unit 39 shown in fig. 3, and may be output to the open-loop control DQ-axis current command generation unit 37 as a forced synchronization position command value. Further, the electrical angle may be calculated based on the position conversion value.

The basic formula of the position control response transfer function G(s) is expressed by the following formula.

Mathematics 1

The position conversion value is preferably obtained using the basic formula, but the position command value may be converted into the position conversion value by the following formula in which the right side of the basic formula is changed.

Mathematics 2

By using a simple position control response transfer function G(s) including only ω ₂ of ff ₁、ff₂、ω₁ and ω ₂, the position conversion value of the motor 22 can be obtained at high speed without using a high-speed and expensive computing device (e.g., CPU). Even in the case of a simple position control response transfer function G(s), the position conversion value of the motor 22 can be obtained with an appropriate value as long as the motor control is performed as follows. Namely, the following mode is adopted: ff ₁ takes a value close to 1 and ff ₂ takes a value close to 0.

As long as the control mode of the motor 22 is switched from the detected position feedback control or the sensorless vector control to the open loop control, the motor may be operated with the same behavior as in the position feedback control. Therefore, the occurrence of the step-out and the vibration of the motor 22 after the control mode is switched to the open-loop control can be suppressed, and the position conversion value can be appropriately obtained by an inexpensive arithmetic device.

As a method for bringing the electric angle of the motor 22 into close contact with the position command value, the following method is also considered: a first-order lag filter is used that gradually converges the position deviation to zero with the position deviation before switching to open-loop control as an initial value. However, in this method, since the positional deviation is reduced irrespective of the position command value, the hand 2A cannot be moved along a desired trajectory.

Fig. 6 is a graph showing a relationship between a position command value and an actual rotation position of the hand 2A based on control in response to the position command value. When focusing on a graph showing the relationship between the rotational position and time, the actual position change is delayed with respect to the change in the position command value. This is because it takes time to respond to a change in the actual position of the instruction. In the detection position feedback control and the sensorless vector control, the position control gain is set so that the actual rotation position is uniformly delayed with respect to the position command value of the motor of each joint of the industrial robot 1, thereby ensuring the orbit accuracy of the hand 2A. On the other hand, in the open loop control, if a method is used in which only the positional deviation of the specific axis is converged to zero by the first-order lag filter, as shown in the figure, the actual change in the rotational position is different from that in the detected position feedback control. Thus, a difference occurs in the delay pattern of the position command value for each axis position, and the position of the hand 2A deviates from the target orbit. In contrast, in the method using the analog value as in the open loop control according to the embodiment, as shown in the figure, the actual rotation position can be changed (the hand 2A can be moved along the target trajectory) in the same manner as when the detected position feedback control is executed, with respect to the change in the position command value.

Fig. 7 is a graph showing time changes of various states in the conventional open loop control. In fig. 7, the following example is shown: after the motor 22 is started by the detection position feedback control, the motor 22 is stopped by the conventional open loop control due to the occurrence of abnormality in the position detection value before the rotational angular velocity of the motor 22 reaches the lower limit value of the sensorless vector control. In this example, after the motor 22 is started, the Q-axis current command value is increased and the angular velocity of the motor 22 is increased by the detection position feedback control. Thereafter, if the control mode is switched to the open loop control to stop the motor 22 due to occurrence of abnormality in the position detection value, the Q-axis current command value is reduced to zero by the filter processing, and thereafter the Q-axis current command value is maintained to zero until the rotation of the motor 22 is stopped.

However, it has been found that in the above-described change in the Q-axis current command value, the motor 22 is out of step or vibrated due to an excessive or insufficient torque. The reason for this is that in order to generate the required torque, it is necessary to supply a Q-axis current for the motor 22. Specifically, as shown in fig. 7, when it is assumed that the motor 22 is stopped by the normal detection position feedback control, the Q-axis current command value is first reduced to zero in a sinusoidal manner, and then increased again in the negative direction, and returned to zero on the negative side through a sinusoidal fluctuation. In order to stop the motor 22 while obtaining the required torque, as described above, it is necessary to change the Q-axis current command value.

Therefore, in the motor driving device 20 according to the embodiment, after the torque required for the motor 22 is obtained based on the position command value, the Q-axis current command value corresponding to the torque is obtained, and the Q-axis current corresponding to the Q-axis current command value and the D-axis current of the magnetic pole of the magnet for introducing the rotor are supplied to the motor. According to this configuration, by supplying the Q-axis current of a value corresponding to the torque required for the motor 22 to the motor, the driving of the motor 22 can be stopped by the open-loop control without causing the motor 22 to be out of step or vibrate due to the excessive or insufficient torque.

As a method for obtaining the torque required to rotate the motor 22 to the position instructed by the position instruction value, the following method is given: the angular acceleration at the time of virtually executing the detection position feedback control is estimated based on the position command value, and the required torque is obtained based on the obtained angular acceleration estimated value. Thus, the torque required to rotate the motor 22 at a desired angular velocity can be obtained.

Further, as another method for obtaining the required torque, the following method is given: the required angular velocity and angular acceleration are estimated based on the position command value, and the required torque is obtained based on the obtained estimated angular velocity and angular acceleration. More specifically, the torque required for acceleration or deceleration is obtained based on the angular acceleration estimation value, and the torque required for compensation of at least one of the viscous resistance and the coulomb friction is obtained based on the angular velocity estimation value.

Further, in experiments conducted by the present inventors, it has been found that in the open loop control, the following disadvantages occur in the method of estimating the required torque based on the position command value and the previous torque command value. Namely, the following occurs: when switching from the sensorless vector control to the open loop control, the motor 22 may be greatly vibrated due to the difference in timing of occurrence of abnormality in the position detection value.

Fig. 8 is a graph showing time variations of various states in a method of determining a Q-axis current command value after start of open-loop control based on a torque command value before start of open-loop control. In fig. 8, a sequence of various states based on the detected position feedback control is written also in a period after occurrence of an abnormality in the position detection value, but the same sequence indicates how the state changes when no abnormality is assumed to occur.

In the example shown in fig. 8, when the rotational angular velocity of the motor 22 increases to a value slightly higher than the lower limit value (threshold value) of the sensorless vector control after the motor 22 is started by the detection position feedback control, an abnormality in the position detection value occurs.

When the control direction is switched from the detection position feedback control to the sensorless vector control based on the occurrence of an abnormality, as shown in the figure, the rotation of the motor 22 becomes unstable due to a transient phenomenon estimated based on the rotation position of the current detection after the switching, and the angular velocity estimated value of the current detection value greatly fluctuates. Since the angular velocity of the motor 22 is slightly higher than the lower limit value of the sensorless vector control when an abnormality of the position detection value occurs, the sensorless vector control is executed only for a short time. Thus, the vibration of the position estimation value based on the current detection value converges, and the control mode shifts to the open-loop control before the angular velocity estimation value stabilizes. Since the Q-axis current value is calculated by multiplication of a constant with respect to the angular velocity estimated value, the torque command value before the control mode is switched from the sensorless vector control to the open-loop control may be far from a value corresponding to the torque required for execution of the open-loop control. If a torque command value having such a value is used, the motor 22 may be greatly vibrated. Hereinafter, the phenomenon in which the motor 22 greatly vibrates as described above is referred to as vibration of the motor 22 at the time of switching open-loop control due to insufficient position estimation responsiveness of sensorless vector control.

In addition, in the case where an abnormality of the position detection value occurs when the motor 22 rotates at a sufficient angular velocity in the detection position feedback control, after the sensorless vector control is performed for a sufficient time and the angular velocity estimation value is stabilized, the control mode is switched to the open loop control. In the open loop control, the torque command value after switching the control system from the sensorless vector control to the open loop control can be obtained with an appropriate value, and therefore the motor 22 is not greatly vibrated.

In the motor driving device 20 according to the embodiment, a rotational position estimated value of the motor 22 in response to the position command value is obtained, and an angular acceleration estimated value is obtained based on the obtained rotational position estimated value. The rotation position estimated value is obtained as the forced synchronization position command value by the open-loop control DQ-axis electrical angle generating section 36.

Fig. 9 is a block diagram showing a control configuration of the open-loop control DQ-axis current command generation unit 37. The open-loop control DQ-axis current command generating unit 37 includes a Q-axis current command generating unit 37A and a D-axis current command generating unit 37B.

The Q-axis current command generating unit 37A includes a plurality of delay elements, a first numerical differentiating unit 37A1, a first low-pass filter 37A9, a second numerical differentiating unit 37A2, a second low-pass filter 37A4, an inertia moment nominal value (hereinafter referred to as inertia gain) 37A5, and the like. The Q-axis current command generating unit 37A includes a torque constant dividing unit 37A8, a sign function unit 37A3, a nominal value of a coefficient of viscosity (hereinafter referred to as a viscous gain) 37A6, a nominal value of a coulomb friction (hereinafter referred to as a coulomb friction gain) 37A7, and the like.

The processing performed by the Q-axis current command generating unit 37A will be described.

The forced synchronization position command value transmitted from the open-loop control electric angle generating unit (36 in fig. 3) is sequentially input to the first numerical differentiating unit 37A1 and the first low-pass filter 37A9, and becomes an angular velocity estimated value. The angular velocity estimation value is sequentially input to the second numerical differentiation unit 37A2 and the second low-pass filter 37A4, becomes an angular acceleration estimation value, and is then input to the inertial gain 37A5. The inertia gain 37A5 outputs an inertia torque compensation value (inertia force). This is equivalent to the case where the torque required for inertial acceleration is calculated based on the following equation.

Mathematical formula 3

J: moment of inertia

Θ: motor angle

The above-described angular velocity estimation value is also input to the viscous gain 37A6. The viscous gain 37A6 outputs a viscous torque compensation value (viscous drag). This is equivalent to the case where the torque for compensating the viscous drag is calculated based on the following equation.

Mathematics 4

D: viscosity coefficient

The angular velocity estimation value is also input to the sign function section 37A3. A value of a sign opposite to the estimated value of the angular velocity is output from the sign function unit 37A3 and input to the coulomb friction gain 37A7. The coulomb friction gain 37a17 outputs a coulomb friction torque compensation value (coulomb friction). This is equivalent to the case where the torque for compensating the coulomb friction is calculated based on the following equation.

Mathematics 5

C: coulomb friction

The gravity compensation value shown in fig. 9 is a constant. The inertia torque compensation value, the viscous torque compensation value, the coulomb friction compensation value, and the gravity compensation value are added together and input to the torque constant division unit 37A8 as torque command values. The torque constant division unit 37A8 outputs a result of dividing the torque command value by the torque constant Kt (a result of multiplying the torque constant reciprocal) as the Q-axis current command value. The Q-axis current command value is input to the current control unit (26 in fig. 3) and the D-axis current command generation unit 37B. The torque constant dividing unit 37A8 may be omitted by including the torque constant of the motor 22 in the inertia gain, the viscous gain, the coulomb friction compensation value, and the gravity compensation value, respectively.

As shown in fig. 8 for determining the Q-axis current command value immediately after the start,

After the control system is switched from the sensorless vector control to the open loop control, it takes about several tens of [ mu ] seconds until the angular acceleration estimated value is obtained. In this period, if the angular acceleration estimated value cannot be obtained, an appropriate Q-axis current cannot be supplied to the motor.

Therefore, in the motor drive device 20 according to the embodiment, as shown in fig. 3, 5, and 9, the acceleration estimation value is obtained based on the position command value during execution of the sensorless vector control.

Specifically, as shown in fig. 3, the position command value transmitted from the upper controller 100 is input to the open-loop control electric angle generating unit 36 without passing through a separator. The forced synchronization position command value output from the open-loop control electrical angle generating unit 36 is input to the open-loop control DQ-axis current command generating unit 37 without passing through a separator. Thus, the flow of inputting the position command value to the first selector 25 as the DQ-axis current command value via the open-loop control electrical angle generating unit 36 and the open-loop control DQ-axis current command generating unit 37 is executed, regardless of the control method. That is, the above-described flow is also executed in the execution of the sensorless vector control.

As shown in fig. 5, the open-loop control electrical angle generating unit 36 generates a position simulation value based on the position command value, and outputs the position simulation value as a forced synchronization position command value to the DQ-axis current command generating unit 37. As shown in fig. 9, the open-loop control DQ-axis current command generator 37 obtains an angular velocity estimated value based on the forced synchronization position command value, and obtains an angular acceleration estimated value based on the obtained angular velocity estimated value. Thus, the motor drive device 20 obtains an estimated acceleration value based on the position command value during execution of the sensorless vector control.

In this configuration, the required torque can be obtained by immediately using the estimated angular acceleration value obtained before after the control system is switched from the sensorless vector control to the open-loop control. Accordingly, the Q-axis current command value corresponding to the required torque can be obtained immediately after switching from the sensorless vector control to the open-loop control, and occurrence of vibration of the motor 22 due to supply of an inappropriate Q-axis current at the time of switching can be suppressed.

In the motor drive device 20 according to the embodiment, the D-axis current value (D-axis current command value) is changed according to the Q-axis current value (Q-axis current command value).

Fig. 10 is a graph showing a relationship between a Q-axis current command value and a D-axis current command value in the motor drive device 20 according to the embodiment. In fig. 10, the Q-axis norm change rate gain is ∈2, but this value is an example. The current value b is a DQ-axis norm current lower limit value, but in the example of fig. 10, this value is taken as the rated current value of the motor 22. But may not be the rated current value. The current value a is obtained by dividing the DQ-axis norm current lower limit value by the Q-axis norm change rate gain. The current value d is a DQ-axis norm current upper limit value, and in the example shown in fig. 10, this value is taken as the instantaneous maximum current specification value of the motor 22. But may not be the instantaneous maximum current specification value. The current value c is obtained by dividing the DQ-axis norm current upper limit value by the Q-axis norm change rate gain. The DQ-axis norm current value is a current value corresponding to the length of a line segment connecting the intersection of the Q-axis current value and the D-axis current value and the origin in the two-dimensional coordinates of the Q-axis current value and the D-axis current value.

Hereinafter, a torque region obtained at a Q-axis current value smaller than the current value a is referred to as a low torque region. The torque region obtained at the Q-axis current value equal to or higher than the current value a and smaller than the current value c is referred to as a transit region. The torque region obtained at the Q-axis current value equal to or higher than the current value c is referred to as a high torque region.

The open-loop control DQ-axis current command generation unit 37 calculates a D-axis current command value so that the norm of the DQ-axis current vector becomes constant in the low torque region. In order to perform this calculation, as an algorithm for obtaining the D-axis current command value, an algorithm is used in which the D-axis current command value is set to a value lower than the Q-axis current command value and the value is decreased as the Q-axis current command value increases. In this configuration, the magnitude of the current is suppressed to the rated current value or less, whereby heat generation of the motor 22 can be suppressed.

In the low torque region, if the D-axis current command value is always reduced, the value becomes the same as the Q-axis current value (DQ-axis norm current value becomes the same as the DQ-axis norm current lower limit value) in the near future, and the torque region becomes the intermediate torque region. In the intermediate torque region, the open-loop control DQ-axis current command generation unit 37 obtains a D-axis current command value by an algorithm that increases the D-axis current command value with an increase in Q-axis current command value. In the illustrated example, the Q-axis current command value and the D-axis current command value are in a proportional relationship. In the intermediate torque region where the Q-axis current command value normally exceeds the rated current value (b), the D-axis current value is made higher than the D-axis current value in the low torque region, whereby the required torque can be obtained. Further, by increasing the D-axis current command value with an increase in torque, a recovery force against calculation errors and disturbances of the required torque can be obtained, and the driving of the motor 22 can be stopped by open loop control without causing the motor 22 to step out or vibrate.

In the torque transfer region, if the D-axis current command value is always increased, the DQ-axis norm current value will soon reach the DQ-axis norm current upper limit value, and the torque region becomes a high torque region. The open-loop control DQ-axis current command generation unit 37 obtains a D-axis current command value by an algorithm that decreases the D-axis current command value with an increase in the Q-axis current command value in the high torque region. In a high torque region where a torque higher than that in the intermediate torque region is required, the Q-axis current value is reduced as the torque increases, so that the force of the magnetic poles of the magnet attracting the rotor can be weakened, and the current exceeding the maximum allowable value can be suppressed.

The process performed by the D-axis current command generating unit 37B shown in fig. 9 will be described.

The D-axis current command generating unit 37B includes a Q-axis-norm current change rate gain 37B1, an absolute value calculating unit 37B2, a saturation unit 37B3, a first square-method calculating unit 37B4, a second square-method calculating unit 37B5, and a square root calculating unit 37B6.

The Q-axis current command value generated by the Q-axis current command generating unit 37A is converted into a square value by the second square operation unit 37B5, and then inputted to the adder as a negative value. The Q-axis current command value is subjected to gain by the Q-axis-norm current change rate gain 37B1, converted into an absolute value by the absolute value calculation unit 37B, and input to the saturation unit 37B3. The saturation unit 37B3 converts the input value to the DQ-axis norm current lower limit value when the input value is lower than the DQ-axis norm current lower limit value, and converts the input value to the DQ-axis norm current upper limit value when the input value is higher than the DQ-axis norm current upper limit value.

The output from the saturation unit 37B3 is converted into a square value by the first square operation unit 37B4, and then input to the adder as a positive value. The square root operation unit 37B6 converts the output value from the adder into a square root value, and outputs the square root value as a D-axis current command value. Through the processing described above, the D-axis current command value changes with the characteristics shown in the graph of fig. 10.

< Working Effect of Industrial robot 1 >)

Structure 1 >

The structure 1 is a motor control method for driving the motor 22 by open loop control based on a current introduction method. The configuration 1 includes a step of obtaining a torque (for example, a torque command value in fig. 9) required for the motor 22 based on a position command value (rotational position command signal) transmitted from the upper controller 100 (signal transmission means). In addition, the structure 1 includes: a step of obtaining a Q-axis current command value corresponding to the required torque (for example, a torque constant division unit 37A8 in fig. 9); and a step of supplying the Q-axis current corresponding to the Q-axis current command value and the D-axis current for the magnetic poles of the magnet for introducing the rotor to the motor (for example, the D-axis current command generating section 37B of fig. 9).

< Action Effect of Structure 1 >)

According to the configuration 1, the Q-axis current having a value corresponding to the torque required for the motor 22 is supplied to the motor 22, so that the driving of the motor 22 can be stopped by the open loop control without causing the motor 22 to step out or vibrate.

Structure 2 >

In the configuration 2, the step of determining the torque in the configuration 1 includes: a step of obtaining an angular acceleration estimated value (for example, an angular velocity estimated value in fig. 9) of the motor 22 in response to the position command value; and a step of obtaining torque (for example, a torque command value in fig. 9) based on the angular acceleration estimated value.

< Action effect of Structure 2 >)

According to the configuration 2, by supplying the Q-axis current corresponding to the torque required to rotate the motor 22 to the motor 22, it is possible to suppress the supply of unnecessary Q-axis current to the motor 22.

Structure 3 >

In the configuration 3, the step of determining the torque in the configuration 2 includes: a step of obtaining an estimated value of the angular velocity of the motor 22 (for example, an estimated value of the angular velocity of fig. 9) in response to the position command value; and a step of obtaining torque based on the angular velocity estimation value and the angular acceleration estimation value.

< Action effect of Structure 3 >)

According to the configuration 3, the torque is obtained based on the angular velocity estimated value in addition to the angular acceleration estimated value, and thus the required torque can be obtained more accurately.

Structure 4 >

In the structure 4, the step of determining the torque in the structure 2 or 3 includes: a step of obtaining a position analog value (rotational position estimated value) of the motor 22 in response to the position command value (for example, a model of the electric system/mechanical system in fig. 5); and a step of obtaining an angular acceleration estimated value (for example, a torque command value in fig. 9) based on the position simulation value.

< Action effect of Structure 4 >)

According to the configuration 4, by obtaining the angular acceleration estimation value of the motor 22 based on the position simulation value, it is possible to avoid occurrence of vibration of the motor 22 at the time of switching of the open loop control due to insufficient execution time of the sensorless vector control.

Structure 5 >

In the configuration 5, in the step of determining the torque in any one of the configurations 2 to 4, the torque of the force required for acceleration and deceleration of the driving mechanical system, which is obtained by multiplying the diagonal acceleration estimated value by a coefficient corresponding to the moment of inertia (for example, the inertia gain 37A5 in fig. 9), is determined as the torque or a part of the torque.

< Action effect of Structure 5 >)

According to the structure 5, a Q-axis current corresponding to the inertial force of the driving mechanical system can be supplied to the motor 22.

Structure 6 >

In the configuration 6, in the step of determining the torque in the configuration 5, an estimated value of the angular velocity of the motor 22 in response to the position command value is determined, and a moment for compensating the force of the viscous resistance of the driving mechanical system is determined as a part of the torque based on the estimated value of the angular velocity.

< Action effect of Structure 6 >)

According to the configuration 6, in addition to the moment of force required for acceleration and deceleration of the driving mechanical system, the viscous resistance of the driving mechanical system is obtained as the required torque. This can suppress occurrence of excessive or insufficient torque of the motor 22, compared with a case where only torque of force required for acceleration and deceleration is obtained as the required torque.

Structure 7 >

In the structure 7, in the step of determining the torque in the structure 5 or 6, the moment of the force for compensating the gravity is determined as a part of the torque.

< Action effect of Structure 7 >)

According to the configuration 7, in addition to the torque of the force required for acceleration and deceleration of the drive mechanism, the gravity is obtained as the required torque, and the occurrence of the excessive or insufficient torque of the motor 22 can be suppressed as compared with the case where only the torque of the force required for acceleration and deceleration is obtained as the required torque.

Structure 8 >

In the configuration 8, in the step of determining the torque in any one of the configurations 5 to 7, an estimated value of the angular velocity of the motor 22 in response to the position command value is determined, and a moment for compensating the force of the coulomb friction is determined as a part of the torque based on the estimated value of the angular velocity.

< Action effect of Structure 8 >)

According to the configuration 8, the coulomb friction is obtained as the required torque in addition to the moment of the force required for acceleration and deceleration of the drive mechanical system. This can suppress occurrence of excessive or insufficient torque of the motor 22, compared with a case where only torque of force required for acceleration and deceleration is obtained as the required torque.

Structure 9 >

In any one of the configurations 5 to 8, the configuration 9 includes a step of obtaining a D-axis current command value corresponding to the Q-axis current command value. In the structure 9, in the step of supplying the Q-axis current corresponding to the Q-axis current command value and the D-axis current of the magnetic pole of the magnet for introducing the rotor to the motor, the D-axis current corresponding to the D-axis current command value is supplied to the motor.

< Action effect of Structure 9 >)

According to the configuration 9, the burning loss of the motor is prevented, and the recovery force against calculation errors and disturbances of the required torque can be obtained while suppressing the heat generation of the motor as compared with the configuration in which the D-axis current of a constant value flows as in the conventional configuration.

Structure 10 >

In the configuration 10, in the step of determining the D-axis current command value in the configuration 9, the D-axis current command value is determined by an algorithm that increases the D-axis current command value with an increase in the Q-axis current command value.

< Action effect of Structure 10 >)

According to the configuration 10, the D-axis current command value is increased with an increase in the Q-axis current command value, so that the recovery force against the calculation error and disturbance of the required torque is obtained, and the driving of the motor 22 can be stopped by the open loop control without causing the motor 22 to be out of step or vibrate.

Structure 11 >

In the configuration 11, in the step of determining the D-axis current command value in the configuration 10, the D-axis current command value is determined by the following algorithm. That is, in a predetermined low torque region, the D-axis current command value is obtained so that the norm of the DQ-axis current vector becomes constant. In the intermediate torque region higher than the low torque region, the D-axis current command value is increased as the Q-axis current command value increases.

Effect of structure 11

According to the configuration 11, in the low torque region where the magnetic pole of the magnet of the rotor does not need to be strongly drawn, the D-axis current value is obtained so that the norm of the DQ-axis current vector becomes constant, and the magnitude of the current can be suppressed to the rated current value or less, thereby suppressing heat generation of the motor 22.

In addition, according to the configuration 11, in the intermediate torque region where the Q-axis current value normally exceeds the rated current value, the D-axis current value is set higher than the D-axis current value in the low torque region, whereby a recovery force against calculation errors and disturbances of the required torque can be obtained, and the driving of the motor 22 can be stopped by the open loop control without causing the motor 22 to step out or vibrate.

Structure 12

In the configuration 12, in the step of obtaining the D-axis current command value in the configuration 11, the D-axis current command value is obtained by an algorithm that decreases the D-axis current command value with an increase in the Q-axis current command value in the high torque region higher than the intermediate torque region.

< Effect of Structure 12 on action >

According to the configuration 12, in the high torque region where a torque higher than the medium torque region is required, the D-axis current value is reduced with an increase in torque, so that the force of the magnetic poles of the magnet attracting the rotor can be weakened, and the current can be suppressed from exceeding the maximum allowable value.

Structure 13 >

In any one of the configurations 5 to 12, the configuration 13 includes a step of detecting an abnormality in a position detection value (rotational position signal) transmitted from the rotational encoder 30 (rotational position detector) that detects the rotational position of the motor 22. In addition, in the configuration 13, when no abnormality is detected, the motor 22 is driven by the detection position feedback control based on the position detection value. In the configuration 13, when an abnormality is detected and the angular velocity of the motor 22 at the time of detection is not less than a predetermined lower limit value (not more than a threshold value or less than a threshold value), the motor 22 is driven by sensorless vector control. In the sensorless vector control, a position estimation value (rotational position estimation value) estimated based on a current flowing through the motor 22 is fed back. In the configuration 13, when an abnormality is detected and the angular velocity of the motor at the time of detection is smaller than the lower limit value, the driving of the motor 22 is stopped by open loop control.

Effect of structure 13

In the configuration 13, when abnormality occurs in the position detection value when the motor 22 rotates at a high speed, the induced voltage that occurs well in the motor 22 is estimated by sensorless vector control. Then, the rotational position of the motor 22 is estimated from the estimated induced voltage, and the motor 22 is driven based on the estimation result to appropriately control the rotational operation of the motor 22. Then, if the angular velocity of the motor 22 is reduced by the sensorless vector control to such an extent that a sufficient induced voltage is not generated in the motor 22, the drive control of the motor 22 is switched from the sensorless vector control to the open loop control. In the open loop control, the rotation operation of the motor 22 is appropriately controlled by a current introduction method. In this configuration, when abnormality occurs in the position detection value when the motor 22 rotates at a high angular velocity, the sensorless vector control and the open loop control are performed, and the motor 22 is gradually decelerated and stopped while the rotation operation of the motor 22 is appropriately controlled.

In the structure 13, when abnormality occurs in the position detection value when the motor 22 rotates at a low angular velocity, the driving of the motor 22 is stopped by the open loop control.

According to this configuration 13, it is possible to avoid occurrence of an improper operation of the hand 2A (the operated body) caused by the forced stop of the motor 22 immediately when the abnormality occurs in the position detection value. Further, since the motor can be operated with the same behavior as that in the case of performing the detection position feedback control after switching the control method to the open loop control, the occurrence of the step-out and the vibration of the motor after switching can be suppressed.

When an abnormality occurs in the position detection value, the mode of the position command value transmitted from the upper controller 100 (upper device) to stop the operation of the hand 2A is not limited to the mode in which the driving of the motor 22 is simply decelerated and stopped. Depending on the structure of the arm 2, the hand 2A may be stopped along an appropriate track in the following manner. Namely, the following modes: first, the driving of the motor 22 is stopped by the sensorless vector control and the open loop control. After that, the motor 22 is reversely rotated by the open-loop control, and then acceleration and deceleration in the reverse direction are performed by the sensorless vector control, and thereafter, the motor 22 is decelerated and stopped by the open-loop control.

Structure 14 >

In the configuration 14, in the execution of the sensorless vector control of the configuration, a step of obtaining an angular acceleration estimation value of the motor 22 based on the position command value (rotational position command value) is executed.

< Action effect of Structure 14 >)

In the configuration 14, immediately after switching from the sensorless vector control to the open loop control, a Q-axis current command value corresponding to the required torque is obtained based on the estimated angular acceleration value obtained before switching. Thus, according to the configuration 14, the occurrence of vibration of the motor 22 caused by the supply of an improper Q-axis current at the time of switching can be suppressed.

Structure 15

The structure 15 is a motor driving device 20 that controls driving of the motor 22, and the driving of the motor 22 is controlled by the motor control method according to any one of the structures 1 to 14.

< Action effect of Structure 15 >)

According to the configuration 15, by using the motor control method according to any one of the configurations 1 to 15, the driving of the motor 22 can be stopped by the open loop control without causing the motor 22 to be out of step or vibrate.

Structure 16 >

The structure 16 is a control method of the industrial robot 1, which independently controls the driving of the plurality of motors 22 to change the position of the arm 2 of the industrial robot 1. In addition, in the structure 16, the driving of each of the plurality of motors 22 is controlled by the motor control method of any one of the structures 1 to 14.

Structure 17

The structure 17 is an industrial robot 1 that controls driving of a plurality of motors 22 independently to change the position of the arm 2, and controls driving of each of the plurality of motors 22 by the motor driving device 20 of the structure 15.

< Effects of structures 16, 17 >

In the configurations 16 and 17, when abnormality occurs in the position detection value in at least one of the motors 22, the driving of the motor 22 can be stopped by open loop control without causing the motor 22 to step out or vibrate.

While the preferred embodiments of the present invention have been described above, the present invention is not limited to the embodiments, and various modifications and changes can be made within the scope of the gist thereof. The embodiments are included in the scope and spirit of the invention, and are also included in the invention described in the claims and their equivalents.

Description of the reference numerals

1 … Industrial robot;

2 … arms;

20 … motor drive means;

21 … control a mode selection section;

22 … motor;

23 … position speed control section;

24 … vector control DQ axis current command generation unit;

25 … first selectors;

26 … current control parts;

27 … DQ inverse transform section;

28 … PWM control sections;

29 … inverter;

30 … rotary encoder (rotary position detector);

31 … current detection sections;

32 … second selectors;

33 … vector control electrical angle generation section;

34 … third selectors;

35 … position estimation units;

36 … open loop control electrical angle generation;

37 … open-loop control DQ axis current command generation section;

38 … encoder communication abnormality determination section;

39 … DQ conversion part;

100 … upper controller.

Claims

1. A motor control method for driving a motor by open loop control based on a current lead-in method, comprising:

A step of obtaining a torque required for the motor based on the rotational position command signal transmitted from the signal transmission unit; a step of obtaining a Q-axis current command value corresponding to the torque; and a step of supplying a Q-axis current corresponding to the Q-axis current command value and a D-axis current for a magnetic pole of a magnet for introducing into the rotor to the motor,

The step of determining the torque includes: a step of obtaining an estimated value of angular acceleration of the motor in response to the rotational position command signal; and a step of obtaining the torque based on the estimated angular acceleration value.

2. The method for controlling a motor according to claim 1, wherein,

The step of determining the torque includes: a step of obtaining an estimated value of the angular velocity of the motor in response to the rotational position command signal; and a step of obtaining the torque based on the angular velocity estimation value and the angular acceleration estimation value.

3. The motor control method according to claim 1 or 2, characterized in that,

The step of determining the torque includes: a step of obtaining a rotational position estimated value of the motor in response to the rotational position command signal; and a step of obtaining the angular acceleration estimation value based on the rotation position estimation value.

4. The motor control method according to claim 1 or 2, characterized in that,

In the step of determining the torque, a moment of force required for acceleration and deceleration of the driving mechanical system, which is obtained by multiplying the estimated angular acceleration value by a coefficient corresponding to the moment of inertia, is determined as the torque or a part of the torque.

5. The motor control method according to claim 4, wherein,

In the step of determining the torque, an estimated angular velocity value of the motor in response to the rotational position command signal is determined, and a moment for compensating a force of viscous resistance of the driving mechanical system is determined as a part of the torque based on the estimated angular velocity value.

6. The motor control method according to claim 4, wherein,

In the step of determining the torque, a moment of force for compensating for gravity is determined as a part of the torque.

7. The motor control method according to claim 4, wherein,

In the step of obtaining the torque, an estimated angular velocity value of the motor in response to the rotational position command signal is obtained, and a moment of force for compensating for the coulomb friction is obtained as a part of the torque based on the estimated angular velocity value.

8. The motor control method according to claim 4, wherein,

The method includes a step of obtaining a D-axis current command value corresponding to the Q-axis current command value, and in a step of supplying a Q-axis current corresponding to the Q-axis current command value and a D-axis current of a magnetic pole of a magnet for introducing a rotor to a motor, the D-axis current corresponding to the D-axis current command value is supplied to the motor.

9. The method for controlling a motor according to claim 8, wherein,

In the step of obtaining the D-axis current command value, the D-axis current command value is obtained by an algorithm that increases the D-axis current command value with an increase in the Q-axis current command value.

10. The method for controlling a motor according to claim 9, wherein,

In the step of obtaining the D-axis current command value, the D-axis current command value is set to a value lower than the Q-axis current command value in a predetermined low torque region, and the D-axis current command value is obtained by an algorithm that increases the D-axis current command value with an increase in the Q-axis current command value in a middle torque region higher than the low torque region while decreasing the Q-axis current command value.

11. The method for controlling a motor according to claim 10, wherein,

In the step of obtaining the D-axis current command value, the D-axis current command value is obtained by an algorithm that decreases the D-axis current command value with an increase in the Q-axis current command value in a high torque region higher than the intermediate torque region.

12. The motor control method according to claim 4, wherein,

Comprises a step of detecting an abnormality in a rotational position signal transmitted from a rotational position detector for detecting the rotational position of a motor,

In the case where the abnormality is not detected, the motor is driven by feedback control based on the rotational position signal,

When the abnormality is detected and the angular velocity of the motor at the time of detection is not equal to or lower than a predetermined threshold value, the motor is driven by sensorless vector control in which a rotational position estimated value estimated based on a current flowing through the motor is fed back,

In the case where the abnormality is detected and the angular velocity of the motor at the time of detection is equal to or lower than the threshold value, driving of the motor is stopped by open loop control, or

In the case where the abnormality is detected and the angular velocity of the motor at the time of detection is not less than a threshold value, the motor is driven by sensorless vector control that feeds back a rotational position estimated value estimated based on a current flowing through the motor,

When the abnormality is detected and the angular velocity of the motor at the time of detection is smaller than a threshold value, driving of the motor is stopped by open loop control.

13. The method for controlling a motor according to claim 12, wherein,

In the execution of the sensorless vector control, a step of obtaining an angular acceleration estimation value of the motor based on the rotational position command signal is executed.

14. A motor driving device for controlling driving of a motor, characterized in that,

Controlling the driving of the motor using the motor control method according to any one of claims 1 to 13.

15. A control method of an industrial robot, which is characterized in that the driving of a plurality of motors is independently controlled to change the position of an arm of the industrial robot,

The motor control method according to any one of claims 1 to 13, wherein driving of each of the plurality of motors is controlled.

16. An industrial robot for changing the position of an arm by controlling the driving of a plurality of motors independently,

The motor driving device according to claim 14, wherein driving of each of the plurality of motors is controlled.