CN110875699B - Interference observer, control device, machine tool, and interference estimation method - Google Patents

Interference observer, control device, machine tool, and interference estimation method Download PDF

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Publication number
CN110875699B
CN110875699B CN201910720856.9A CN201910720856A CN110875699B CN 110875699 B CN110875699 B CN 110875699B CN 201910720856 A CN201910720856 A CN 201910720856A CN 110875699 B CN110875699 B CN 110875699B
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motor
torque
temperature
constant
current
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CN110875699A (en
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寺田弦
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Brother Industries Ltd
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Brother Industries Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/13—Observer control, e.g. using Luenberger observers or Kalman filters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
    • B23Q1/00—Members which are comprised in the general build-up of a form of machine, particularly relatively large fixed members
    • B23Q1/0009—Energy-transferring means or control lines for movable machine parts; Control panels or boxes; Control parts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
    • B23Q17/00—Arrangements for observing, indicating or measuring on machine tools
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/14—Estimation or adaptation of machine parameters, e.g. flux, current or voltage
    • H02P21/20—Estimation of torque
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Power Engineering (AREA)
  • Numerical Control (AREA)
  • Control Of Electric Motors In General (AREA)
  • Feedback Control In General (AREA)

Abstract

The invention provides an interference observer, a control device, a machine tool and an interference estimation method, wherein the interference observer performs feedback control on a motor based on a command, acquires position information and current information of the motor, and estimates interference acting on the motor. The interference observer includes: a constant calculation unit that acquires temperature information of the motor, and calculates a torque constant of the motor based on a temperature indicated by the acquired temperature information; a torque calculation unit that multiplies the torque constant calculated by the constant calculation unit by the current indicated by the acquired current information to calculate the torque of the motor; and a torque estimation unit that estimates the torque of the motor based on the position indicated by the acquired position information and a constant of the load machine driven by the motor, wherein the disturbance observer subtracts the torque estimated by the torque estimation unit from the torque calculated by the torque calculation unit to estimate the disturbance.

Description

Interference observer, control device, machine tool, and interference estimation method
Technical Field
To an interference observer, a control device, a machine tool, and an interference estimation method of a feedback control system.
Background
Conventionally, in a feedback control device for a motor, interference affecting a system is estimated by an interference observer, and the estimated interference is used. When a disturbance observer is used in the feedback control device of the motor, the torque constant is regarded as a fixed value that is independent of temperature.
Japanese patent laid-open publication and Japanese patent laid-open publication No. 03-196313 disclose a collision detection method using an interference observer. The disturbance observer detects a collision of the driven body and stops the motor when the estimated magnitude of the disturbance torque is equal to or greater than a set value.
In the technique disclosed in the above publication, the torque constant Kt that varies depending on the temperature is set to a fixed value. Therefore, when the motor temperature increases, the error of the estimated disturbance torque increases, and even when the driven body does not collide, the collision may be erroneously detected.
Disclosure of Invention
The invention aims to provide an interference observer, a control device, a machine tool and an interference estimation method, wherein the error of the estimated interference can be reduced.
The disturbance observer according to claim 1 performs feedback control on a motor based on a command, acquires position information and current information of the motor, and estimates disturbance acting on the motor, and includes: a constant calculation unit that acquires temperature information of the motor, and calculates a torque constant of the motor based on a temperature indicated by the acquired temperature information; a torque calculation unit that multiplies the torque constant calculated by the constant calculation unit by a current indicated by the acquired current information to calculate a torque of the motor; and a torque estimating section that estimates a torque of the motor based on a position indicated by the acquired position information and a constant of a load machine driven by the motor, wherein the disturbance observer subtracts the torque estimated by the torque estimating section from the torque calculated by the torque calculating section to estimate the disturbance. The disturbance observer corrects the torque constant according to the temperature of the motor, so that the actual torque of the motor including the disturbance-free torque can be calculated with high accuracy, and the calculation accuracy of the disturbance can be improved.
The instruction of the disturbance observer according to claim 2 is either one or both of a position instruction and a velocity instruction.
The disturbance observer feedback-controls the current of the motor that generates the torque of the motor according to the instruction content, and therefore, either one or both of the position and the speed of the motor are converged on the target.
The torque estimation unit of the disturbance observer according to claim 3 estimates the torque based on a sum of a product of a rotational speed obtained by first-order differentiating the position indicated by the acquired position information and the viscosity of the load machine, a product of an acceleration obtained by further first-order differentiating the rotational speed and the moment of inertia of the load machine, and a coulomb frictional force corresponding to the moving direction of the load machine.
The disturbance observer adds a viscous torque calculated by multiplying a rotational speed obtained by first-order differentiating the position of the motor by the viscosity of the load machine, an inertia torque calculated by multiplying an acceleration obtained by further first-order differentiating the rotational speed by the inertia moment of the load machine, and a coulomb friction whose sign is positive/negative according to a change in the moving direction of the load machine to estimate the torque. The disturbance observer estimates the torque of the motor by combining the moment of inertia, viscosity, and coulomb friction of the load machine including the motor, and thus can estimate the torque of the motor from which the disturbance is removed with high accuracy.
The constant calculation unit of the disturbance observer according to claim 4 approximates the torque constant using a polynomial or a piecewise polynomial of degree n (n is an integer of 1 or more) obtained based on a relationship between the temperature of the motor and the torque actually measured in advance.
Therefore, the disturbance observer determines polynomials to be applied to all or each section in consideration of the curvature, inflection point, and actual measurement point number of the curve represented by the actual measurement result, and improves the approximation accuracy of the torque constant according to the degree of the polynomial or the number of sections of the piecewise polynomial.
The disturbance observer according to claim 5 further includes a table storing a correspondence relation between a current and a rotation speed of the motor and a torque constant of the motor, and the constant calculating unit calculates the torque constant based on the polynomial or the piecewise polynomial and contents stored in the table in correspondence with a current indicated by the acquired current information and a rotation speed obtained by first-order differentiating a position indicated by the acquired position information.
In addition to the above-described polynomial or piecewise polynomial, the correspondence between the current and rotational speed of the motor and the torque constant of the motor is actually measured in advance and stored in a table. When calculating the torque constant at the time of execution, the torque constant calculated based on the content stored in the table corresponding to the current of the motor and the rotation speed of the motor is corrected based on the polynomial or the piecewise polynomial, or the torque constant calculated by applying the detected temperature to the polynomial or the piecewise polynomial is corrected based on the stored content of the table. Thus, the disturbance observer can further improve the calculation accuracy of the torque constant and reduce the calculation load.
The disturbance observer according to claim 6 further includes a table storing a correspondence relation between the current and the temperature of the motor and a torque constant of the motor, and the constant calculating unit calculates the torque constant based on contents stored in the table in correspondence with the current indicated by the acquired current information and the temperature indicated by the acquired temperature information.
Thus, the disturbance observer can improve the calculation accuracy of the torque constant and reduce the calculation load.
The disturbance observer according to claim 7 further includes a table storing a correspondence relation between a current, a temperature, and a rotational speed of the motor and a torque constant of the motor, and the constant calculating unit calculates the torque constant based on contents stored in the table in correspondence with the current indicated by the acquired current information, the temperature indicated by the acquired temperature information, and the rotational speed obtained by first-order differentiating the position indicated by the acquired position information.
The disturbance observer can further improve the calculation accuracy of the torque constant and reduce the calculation load.
The control device according to claim 8 includes the disturbance observer described above, and a control unit that issues the command.
The disturbance observer that estimates the disturbance with high accuracy can be applied to a control device that controls a load machine.
The machine tool according to claim 9 is provided with the control device, the motor, and the load machine, and further comprises: a position detection unit that detects a position of the motor and feeds back position information indicating the detected position; a current detection unit that detects a current of the motor and feeds back current information indicating the detected current; and a temperature detection unit that detects a temperature of the motor and generates temperature information indicating the detected temperature, wherein the disturbance observer acquires the temperature information from the temperature detection unit.
A control unit of the control device issues a command to feedback-control a motor that drives the load machine. The disturbance observer of the control device acquires position information and current information of the motor and temperature information from the temperature detection unit, which are fed back by the position detection unit and the current detection unit, respectively, to estimate the disturbance. Thus, the machine tool can estimate the disturbance acting on the motor with high accuracy via the load machine.
The interference estimation method of claim 10 performs feedback control on a motor based on an instruction, and acquires position information and current information of the motor to estimate interference acting on the motor, the interference estimation method comprising the steps of: acquiring temperature information of the motor, and calculating a torque constant of the motor based on a temperature indicated by the acquired temperature information; multiplying the calculated torque constant by a current represented by the acquired current information to calculate a torque of the motor; estimating a torque of the motor based on a position indicated by the acquired position information and a constant of a load machine driven by the motor; and subtracting the estimated torque from the calculated torque to estimate the disturbance.
Drawings
Fig. 1 is a perspective view showing a machine tool according to embodiment 1.
Fig. 2 is a block diagram showing a control device.
Fig. 3 is a block diagram showing information exchanged by the control device and the X-axis motor.
Fig. 4 is a block diagram showing a functional configuration of the servo circuit.
Fig. 5 is a block diagram showing a functional configuration of the disturbance observer.
Fig. 6 is a flowchart showing a processing procedure of the CPU for estimating the interference force by using the interference observer of embodiment 1.
Fig. 7 is a flowchart showing a processing procedure of the CPU that detects the rotation direction of the motor to calculate the rotation speed and the acceleration.
Fig. 8 is a graph showing the contents of a table storing the correspondence relationship between the current, temperature, and rotational speed of the motor and the torque constant.
Fig. 9 is a flowchart showing a processing procedure of a CPU for estimating an interference force by using the interference observer of embodiment 2.
Fig. 10 is a graph showing the contents of a table storing the correspondence relationship between the current and the rotational speed of the motor and the torque constant.
Fig. 11 is a flowchart showing a processing procedure of a CPU for calculating a torque constant by using the disturbance observer according to embodiment 3.
Fig. 12 is an explanatory diagram schematically showing a temperature model of the motor.
Fig. 13 is a graph showing simulation results of temperature changes in each part of the motor.
Detailed Description
The present invention will be described in detail below based on drawings showing embodiments of the present invention.
(embodiment 1)
In the following description, up and down, left and right, and front and back as indicated by arrows in the drawings are used. As shown in fig. 1, the machine tool 100 includes a rectangular base 1 extending in the front-rear direction. The work holding portion 3 is provided on the front side of the upper portion of the base 1. The work holding portion 3 is rotatable about an a axis extending in the left-right direction and a C axis extending in the up-down direction. The support table 2 is provided at the rear side of the upper portion of the base 1 and supports the column 4.
The Y-axis direction moving mechanism 10 (corresponding to a load machine) is provided above the support table 2, and moves the moving plate 16 in the front-rear direction. The Y-axis direction moving mechanism 10 includes two rails 11 extending in the front-rear direction, a Y-axis screw shaft 12, a Y-axis motor 13, and a bearing 14. The rails 11 are provided on the left and right sides of the upper portion of the support table 2. The Y-axis screw shaft 12 extends in the front-rear direction and is disposed between the two rails 11. The bearing 14 is provided at the front end portion and the middle portion (not shown) of the Y-axis screw shaft 12. The Y-axis motor 13 is connected to the rear end of the Y-axis screw shaft 12. A nut (not shown) is screwed with the Y-axis screw shaft 12. A plurality of sliders 15 are slidably provided to each rail 11. The moving plate 16 extends in the horizontal direction and is connected to the nut and the upper portion of the slider 15. The Y-axis screw shaft 12 is rotated by rotation of the Y-axis motor 13, the nut moves in the front-rear direction, and the moving plate 16 moves in the front-rear direction.
An X-axis direction moving mechanism 20 (corresponding to a load machine) is provided on the upper surface of the moving plate 16, and moves the column 4 in the left-right direction. The X-axis direction moving mechanism 20 includes two rails 21 extending in the left-right direction, an X-axis screw shaft 22, an X-axis motor 23 (see fig. 2), and a bearing 24. Rails 21 are provided on the front and rear sides of the upper surface of the moving plate 16. The X-axis screw shaft 22 extends in the left-right direction and is disposed between the two rails 21. The bearing 24 is provided at the left end portion and the middle portion (not shown) of the X-axis screw shaft 22. The X-axis motor 23 is connected to the right end of the X-axis screw shaft 22. A nut (not shown) is screwed with the X-axis screw shaft 22. A plurality of sliders 26 are slidably provided to each rail 21. The column 4 is connected to the nut and the upper part of the slider 26. The X-axis screw shaft 22 is rotated by rotation of the X-axis motor 23, the nut is moved in the left-right direction, and the column 4 is moved in the left-right direction.
The Z-axis direction moving mechanism 30 (corresponding to a load machine) is provided on the front surface of the column 4, and moves the spindle head 5 in the up-down direction. The Z-axis direction moving mechanism 30 includes two rails 31 extending in the up-down direction, a Z-axis screw shaft 32, a Z-axis motor 33, and a bearing 34. Rails 31 are provided on the left and right sides of the front surface of the pillar 4. The Z-axis screw shaft 32 extends in the up-down direction and is disposed between the two rails 31. The bearing 34 is provided at a lower end portion and a middle portion (not shown) of the Z-axis screw shaft 32. The Z-axis motor 33 is connected to the upper end of the Z-axis screw shaft 32. A nut (not shown) is screwed to the Z-axis screw shaft 32. A plurality of sliders 35 are slidably provided on each rail 31. The spindle head 5 is coupled to the front portion of the nut and slider 35. The Z-axis screw shaft 32 is rotated by rotation of the Z-axis motor 33, the nut moves in the up-down direction, and the spindle head 5 moves in the up-down direction.
A spindle 51 (corresponding to a load machine) extending in the up-down direction is provided in the spindle head 5. The main shaft 51 rotates around the shaft. The spindle motor 6 is provided at the upper end of the spindle head 5. A tool is attached to the lower end of the main shaft 51. The spindle 51 is rotated by the rotation of the spindle motor 6, whereby the tool rotates. The rotating tool processes the workpiece held by the workpiece holding portion 3.
As shown in fig. 2, the machine tool 100 includes a control device 60 that controls driving of the spindle motor 6, the Y-axis motor 13, the X-axis motor 23, the Z-axis motor 33, and the like. The control device 60 includes a CPU 61, a ROM 62, a RAM63, a nonvolatile memory 64 such as an EEPROM, an input interface 65, an input/output interface 66, and the like. The storage device 64 stores a machining process for machining a workpiece. The processing step includes a plurality of rows (commands). The CPU 61 reads the rows in order, and issues an instruction for executing a command to drive each section.
The machine tool 100 further includes a receiving portion 67 (setting portion), a Z-axis sensor 68, and a spindle sensor 69. The receiving unit 67 includes a keyboard, a touch panel, a display screen, and the like, and receives a user operation. The user sets execution of a specific process in the storage device 64 via the receiving unit 67. The Z-axis sensor 68 detects the position of the spindle 51 in the up-down direction (the axial position of the spindle 51). The spindle sensor 69 detects the position of the spindle 51 in the circumferential direction. The control device 60 receives a setting from the receiving unit 67 via the input interface 65, receives an axial position from the Z-axis sensor 68, and receives a rotational speed from the main shaft sensor 69. The control device 60 sends a position command or a speed command to the spindle motor 6, the X-axis motor 23, the Y-axis motor 13, and the Z-axis motor 33 via the input/output interface 66. The control device 60 also acquires the position information and the current information of the spindle motor 6, the X-axis motor 23, the Y-axis motor 13, and the Z-axis motor 33 via the input/output interface 66.
When the CPU 61 performs the machining process, the CPU 61 issues instructions to the spindle motor 6, the X-axis motor 23, the Y-axis motor 13, and the Z-axis motor 33 to control the rotation of the spindle 51 and the movement of the X-axis direction moving mechanism 20, the Y-axis direction moving mechanism 10, and the Z-axis direction moving mechanism 30. The CPU 61 processes a workpiece using a tool mounted on the spindle 51.
The flow of information between the X-axis motor 23 and the control device 60 will be described with reference to fig. 3. The Y-axis motor 13, the Z-axis motor 33, and the spindle motor 6 are the same as the X-axis motor 23, and therefore, the description thereof will be omitted. The control section 600 and the disturbance observer 610 included in the control device 60 are one of the functional blocks implemented by the control device 60. The X-axis motor 23 has a motor 23a that drives the X-axis screw shaft 22 and a servo circuit 230. The servo circuit 230 performs feedback control of the current flowing through the motor 23a based on either one or both of the position command and the speed command output from the control unit 600. The current flowing through the motor 23a is detected by the current detecting unit 237, and the current detecting unit 237 feeds back current information indicating the detected current to the servo circuit 230.
The motor 23a is an AC servo motor having a magnet in a rotor, but is not limited thereto. The rotational position of the motor 23a is detected by an encoder 23b (corresponding to a position detecting unit), and the encoder 23b feeds back position information indicating the detected rotational position to the servo circuit 230 as a pulse signal. The temperature of the motor 23a is detected by the temperature detecting unit 23c, and the temperature detecting unit 23c supplies temperature information indicating the detected temperature to the disturbance observer 610. The temperature detecting unit 23c preferably detects the temperature of the magnet of the rotor (hereinafter referred to as the magnet temperature). When the magnet temperature cannot be directly detected, the magnet temperature may be estimated by detecting the current of the motor 23a and the outside air temperature of the motor 23a (see simulation described later). Instead of using the magnet temperature, the temperature of the outer wall of the motor 23a, the temperature of the encoder 23b, and the like may be used.
The disturbance observer 610 acquires position information and current information from the servo circuit 230, and acquires temperature information from the temperature detection unit 23c, and estimates disturbance acting on the motor 23a, that is, disturbance torque (disturbance force). The disturbance observer 610 may acquire the position information and the current information without via the servo circuit 230. When the disturbance force estimated by the disturbance observer 610 exceeds a predetermined threshold value, the control unit 600 can issue a predetermined alarm and a command to stop the motor 23 a.
The operation of the servo circuit 230 that receives the position command from the control unit 600 will be described with reference to fig. 4. The servo circuits of the Y-axis motor 13, the Z-axis motor 33, and the spindle motor 6 are also the same. The servo circuit 230 has an amplifier 231 (position proportional gain), and the amplifier 231 amplifies a position error, which is a difference between a target position included in the position command and a position indicated by position information fed back from the encoder 23b, to generate a speed command. The servo circuit 230 further has: a differentiator 232 that first-order differentiates the position indicated by the position information to generate the rotation speed of the motor 23 a; an amplifier 233 (speed proportional gain) that amplifies a speed error, which is a difference between the speed command generated by the amplifier 231 and the rotation speed generated by the differentiator 232; and an integrator 234 and an amplifier 235 (speed integrating gain) that integrate and amplify the speed error.
The servo circuit 230 performs PI control by setting a result obtained by adding an amount proportional to the speed error amplified by the amplifier 233 and an amount proportional to the integral result of the speed error amplified by the amplifier 235 as a current command. The servo circuit 230 further has a current controller 236, and the current controller 236 feedback-controls the current flowing through the motor 23a based on the above-described current command. The current detection unit 237 feeds back current information indicating the detected current to the current controller 236, and the current controller 236 controls such that a current corresponding to the current command flows through the motor 23a.
The operation of the servo circuit 230 when the control unit 600 issues a position command has been described above, but the speed command from the control unit 600 may be used instead of the speed command generated by the amplifier 231 when the control unit 600 issues a speed command. When the control unit 600 issues the position command and the speed command simultaneously, the operations when the respective commands are issued individually may be overlapped.
The operation of the disturbance observer 610 will be described with reference to fig. 5. The same applies to the disturbance observers of the Y-axis motor 13, the Z-axis motor 33, and the spindle motor 6. The disturbance observer 610 has a constant calculation unit 611, and the constant calculation unit 611 acquires temperature information from the temperature detection unit 23c and calculates a torque constant based on the temperature indicated by the acquired temperature information. The disturbance observer 610 further has a torque calculation section 612, and the torque calculation section 612 multiplies the torque constant calculated by the constant calculation section 611 by the current indicated by the acquired current information to calculate the torque of the motor 23a. The torque calculated by the torque calculation unit 612 includes an anti-disturbance torque. The disturbance observer 610 further has a torque estimating section 613, and the torque estimating section 613 estimates the torque of the motor 23a based on the position indicated by the acquired position information and a constant related to the X-axis direction moving mechanism 20.
The constant calculation unit 611 approximates the torque constant Kt by applying the temperature T indicated by the acquired temperature information to a polynomial or a piecewise polynomial of degree n (n is an integer of 1 or more). The polynomial expression is one of a first order expression of the temperature T as in the following expression (1), a second order expression of the temperature T as in the expression (2), and an n-th order expression of the temperature T as in the expression (3) which are determined in advance so that the actual measurement is performed while changing the temperature of the motor 23 a. In general, the higher the temperature of the motor 23a, the higher the magnet temperature of the rotor of the motor 23a becomes, and the lower the magnetic flux density of the magnet becomes, and therefore the smaller the torque constant becomes. The relation between the temperature and the torque of the motor 23a can be actually measured in advance, and an equation that optimally expresses the relation between the temperature and the torque can be established in consideration of the curvature, inflection point, and actual measurement point number of the curve expressed by the actual measurement result.
Kt＝a-bT···(1)
Kt＝a-b(T-c) 2 ···(2)
Kt＝a0+a1T+a2T 2 +···+anT n ···(3)
Wherein, the liquid crystal display device comprises a liquid crystal display device, a, b, c, a, a1, a2 the term an is a fixed constant or coefficient.
Instead of the above-described formulas (1) to (3), a function Sj (T) as shown in the following formula (4) for performing spline interpolation in the interval [ Tj, tj+1] (j=0, 1, 2) may be actually measured and determined in advance. At this time, the constant calculation unit 611 sets the value of the function Sj (T) defined by the section [ Tj, tj+1] including the temperature T indicated by the acquired temperature information as the torque constant Kt at the temperature T.
Sj(T)＝aj(T-Tj) 3 +bj(T-Tj) 2 +cj(T-Tj)+dj···(4)
Wherein aj, bj, cj, dj is a fixed coefficient or constant.
The torque estimation unit 613 includes: a direction detector 614 that detects a rotational direction of the motor 23a, that is, a moving direction of the X-axis direction moving mechanism 20, based on the acquired position information; a differentiator 615 that first-order differentiates the position represented by the acquired position information to generate a rotation speed; and a differentiator 616 that first-order differentiates the rotational speed generated by the differentiator 615 to generate acceleration. The torque estimating unit 613 in fig. 5 further includes an output unit 617 for outputting positive or negative coulomb friction acting on the X-axis direction moving mechanism 20 including the motor 23 a. Multiplier 618 multiplies the viscosity of X-axis direction moving mechanism 20 including motor 23a, and multiplier 619 multiplies the moment of inertia.
The direction detector 614 may calculate the difference between the previous value and the current value of the position information and output the sign of the difference. The direction detector 614 may detect the rotational direction of the motor 23a using a well-known hardware circuit. The output section 617 outputs positive and negative friction torques according to the detection result of the direction detector 614. The differentiator 615 calculates a difference between a previous value and a current value of the position information and divides the difference by an acquisition interval time of the position information, thereby calculating a rotational speed. The differentiator 616 calculates the difference between the previous value and the current value of the rotational speed calculated by the differentiator 615 and divides the difference by the acquisition interval time of the position information, thereby calculating the acceleration. Multiplier 618 multiplies the rotational speed generated by differentiator 615 by viscosity to output a viscous torque. Multiplier 619 multiplies the acceleration generated by differentiator 616 by the moment of inertia to output the moment of inertia. The result of adding the friction torque, the viscous torque, and the inertia torque is the torque estimated by the torque estimating unit 613. The disturbance observer 610 subtracts the torque estimated by the torque estimating unit 613 from the torque calculated by the torque calculating unit 612 (including the torque calculated by the anti-disturbance unit) to estimate the disturbance force. The speed of the motor 23a is fixed to a plurality of rotational speeds and the torque value in rotation is measured, and the viscosity is calculated from the proportional relationship between the speed and the torque value. The acceleration of the motor 23a is fixed to a plurality of accelerations, and the torque value in rotation is measured, and the moment of inertia is calculated from the proportional relationship between the acceleration and the torque value. As the moment of inertia, a value calculated from a design drawing of the load machine may be used.
The operation of the disturbance observer 610 will be described with reference to fig. 6 and 7. The Y-axis motor 13, the Z-axis motor 33, and the spindle motor 6 are also similar. The process shown in fig. 6 starts at a fixed period (e.g., every 1 ms).
When the process of fig. 6 is started, the CPU 61 acquires temperature information of the motor 23a from the temperature detecting unit 23c (S11), and applies the temperature T indicated by the acquired temperature information to any one of the polynomials of formulas (1) to (3) or the piecewise polynomial of formula (4) to calculate a torque constant Kt (S12: corresponding to the constant calculating unit 611). The CPU 61 causes the torque estimating unit 613 to estimate the torque of the motor 23a based on the rotational direction, rotational speed, and acceleration of the motor 23a, which are the processing results of fig. 7 (S13: corresponding to the torque estimating unit 613). The CPU 61 directly acquires or acquires current information from the current detecting unit 237 via the servo circuit 230 (S14), and multiplies the current represented by the acquired current information by the torque constant calculated in step S12 to calculate the torque of the motor 23a (S15: corresponding to the torque calculating unit 612). The CPU 61 subtracts the torque estimated in step S13 from the calculated torque to estimate the disturbance force as the disturbance torque (S16), and ends the process of fig. 6.
When the process of fig. 7 is started, the CPU 61 detects the rotation direction of the motor 23a based on the pulse signals of different phases from the encoder 23b (S21: corresponding to the direction detector 614). The output section 617 shown in fig. 5 outputs a positive or negative frictional force according to the rotation direction detected by the direction detector 614. The CPU 61 calculates the rotation speed of the motor 23a as a value proportional to the reciprocal of the acquisition interval of the position information (S22: corresponding to the differentiator 615). The CPU 61 calculates the acceleration of the motor 23a as a value proportional to the time rate of change of the rotational speed of the motor 23a (S23: corresponding to the differentiator 616), and ends the process of fig. 7.
In embodiment 1, the explanation has been made on the premise that the torque constant does not depend on the rotation speed of the motor 23a, but the torque constant is smaller when the low-magnetic-field control is performed than when the low-magnetic-field control is not performed. At this time, any one of the polynomials of the formulas (1) to (3) or the piecewise polynomial of the formula (4) may be determined based on a result actually measured in advance so as to change the temperature and the current of the motor 23 a. The constant calculation unit 611 may calculate the torque constant using a polynomial or a piecewise polynomial corresponding to the detected current of the motor 23 a.
The torque constant is also different depending on whether the motor 23a is in the power running state or the regenerative state. In the regeneration state, any one of the polynomials of the plurality of formulas (1) to (3) or the piecewise polynomial of the formula (4) may be determined based on a result actually measured in advance so as to change the temperature of the motor 23a and the power running state/regeneration state. The constant calculating unit 611 may detect the power running state and the regenerative state of the motor 23a and calculate the torque constant using a polynomial or a piecewise polynomial corresponding to the detected state.
As described above, in embodiment 1, the torque constant of the motor 23a is calculated based on the temperature of the motor 23a, the calculated torque constant is multiplied by the current of the motor 23a to calculate the torque of the motor 23a, the torque of the motor 23a is estimated based on the position of the motor 23a and the constant of the X-axis direction moving mechanism 20 driven by the motor 23a, and the estimated torque of the motor 23a is subtracted from the calculated torque of the motor 23a to estimate the disturbance force as the disturbance torque acting on the motor 23 a. Since the disturbance observer 610 corrects the torque constant based on the temperature of the motor 23a, the actual torque of the motor 23a including the disturbance-free torque can be calculated with high accuracy, and the accuracy of calculating the disturbance can be improved. Thus, the interference observer 610 can reduce the error of the estimated interference.
In embodiment 1, the current flowing through the motor 23a is controlled based on either or both of the issued position command and the issued speed command. Thus, the disturbance observer 610 feedback-controls the current of the motor that generates the torque of the motor 23a according to the instruction content, and therefore either or both of the position and the speed of the motor 23a converge on the instructed target.
In embodiment 1, the torque is estimated by adding a viscous torque calculated by multiplying the rotational speed obtained by first-order differentiating the position of the motor 23a by the viscosity of the load machine, an inertial torque calculated by multiplying the acceleration obtained by further first-order differentiating the rotational speed by the inertia moment of the X-axis direction moving mechanism 20, and a coulomb friction whose sign is positive/negative according to the change in the moving direction of the X-axis direction moving mechanism 20. Accordingly, the disturbance observer 610 combines the moment of inertia, viscosity, and coulomb friction of the X-axis direction moving mechanism 20 including the motor 23a to estimate the torque of the motor 23a, and thus can estimate the torque of the motor 23a from which the disturbance is removed with high accuracy.
In embodiment 1, a polynomial or a piecewise polynomial of n degrees is established by actually measuring the relation between the temperature of the motor 23a and the torque in advance, and the detected temperature of the motor 23a is applied to the polynomial to approximate the torque constant. Thus, the disturbance observer 610 determines polynomials to be applied to all or each section in consideration of the curvature, inflection point, and actual measurement point number of the curve represented by the actual measurement result, and the approximation accuracy of the torque constant increases according to the degree of the polynomial or the number of sections of the piecewise polynomial.
In addition, embodiment 1 can apply the disturbance observer 610 that estimates disturbance with high accuracy to the control device 60 that controls the X-axis direction moving mechanism 20.
In embodiment 1, the control unit 600 of the control device 60 issues a position command to the servo circuit 230, and the servo circuit 230 that has received the position command performs feedback control on the motor 23a that drives the X-axis direction moving mechanism 20. The disturbance observer 610 of the control device 60 acquires position information and current information of the motor 23a fed back to the servo circuit 230 by the encoder 23b and the current detection unit 237, and temperature information from the temperature detection unit 23c, respectively, to estimate disturbance. Thus, the disturbance observer 610 can estimate the disturbance acting on the motor 23a with high accuracy via the X-axis direction moving mechanism 20.
(embodiment 2)
In embodiment 1, the constant calculating unit 611 calculates the torque constant using a polynomial or a piecewise polynomial of the temperature, whereas in embodiment 2, the constant calculating unit 611 calculates the torque constant by reading the contents stored in the table. Further, the relation between more variables including temperature and torque constant is stored in the table. In embodiment 2 and embodiment 3 described below, the motor 23a included in the X-axis motor 23 is described, but other motors included in the Y-axis motor 13 and the Z-axis motor 33 are also the same.
Tables 641, 642, 643 shown in fig. 8 are recorded in the storage device 64, but may be recorded in the ROM 62. Tables 641, 642, 643 store the relationship between the current and temperature of motor 23a and the torque constant when the rotational speed of motor 23a is 0rpm, 5000rpm, 10000rpm, respectively. The basic tables 641, 642, 643 are tables 641 corresponding to the case where the rotation speed of the motor 23a is 0 rpm. In each table, when the temperature is 0 ℃ and the current is 50A, the torque constant becomes smaller as the temperature ratio becomes higher or the current ratio becomes larger.
Table 641 stores torque constants of 1, 0.99, 0.98, and 0.97 at a current of 50A and a temperature of 0 ℃, 10 ℃, 20 ℃, and 30 ℃. This corresponds to a magnetic flux density drop of about 0.1% for a temperature rise of 1 ℃ for a magnet commonly used in AC servomotors. Table 641 shows: at the same temperature, when the current is greater than 50A, the torque constant of the motor decreases. The same trend applies to tables 642 and 643. In table 642, since the revolution speed of the motor 23a is increased, the current of 10A is passed by the low-field control, and the torque constant is lowered with respect to table 641. In table 643, it is assumed that the weak field current of 20A flows, and the torque constant further decreases.
A method of calculating a torque constant based on the contents stored in the table shown in fig. 8 will be described with reference to fig. 9. The process shown in fig. 9 starts at a fixed period (e.g., every 1 ms). The rotational speed and acceleration in the figure are the rotational speed and acceleration of the motor 23a calculated by the CPU 61 through the process shown in fig. 7 of embodiment 1.
At the start of the process of fig. 9, the CPU 61 directly acquires or acquires current information from the current detecting section 237 via the servo circuit 230 (S31), and acquires temperature information of the motor 23a from the temperature detecting section 23c (S32). The CPU 61 reads out the contents stored in any one of the tables 641, 642, 643 in correspondence with the current indicated by the acquired current information, the temperature indicated by the acquired temperature information, and the rotation speed of the motor 23a (S33). Specifically, the CPU 61 selects two tables close to the calculated rotation speed, and reads out the contents of four cells close to the acquired current and temperature from each table. More specifically, at a rotation speed of 500rpm, the current obtained was 35A, and at a temperature obtained was 5 ℃, the CPU 61 read 1, 0.99, 1, 0.99 from table 641, and read 0.67, 0.66, 0.6, 0.59 from table 642.
After that, the CPU 61 calculates one torque constant by linear interpolation, for example, based on the eight torque constants read out by step S33 (S34: corresponding to the constant calculating section 611). The CPU 61 causes the torque estimating unit 613 to estimate the torque of the motor 23a based on the rotational direction, rotational speed, and acceleration of the motor 23a (S35: corresponding to the torque estimating unit 613). The CPU 61 also multiplies the current represented by the current information acquired in step S31 by the torque constant calculated in step S34 to calculate the torque of the motor 23a (S36: corresponding to the torque calculation unit 612). The CPU 61 subtracts the torque estimated in step S35 from the calculated torque to estimate the disturbance force as the disturbance torque (S37), and ends the process of fig. 9.
The torque constant is also different depending on whether the motor 23a is in the power running state or the regenerative state. Thus, the table shown in fig. 8 may be prepared for each of the power running state and the regeneration state. The powering operation indicates a state in which the motor 23a performs work to the outside, specifically, a state in which the rotational speed of the motor 23a is the same as the sign of the torque. The regeneration indicates a state in which work is performed on the motor 23a from the outside, specifically, a state in which the rotation speed of the motor 23a is different from the sign of the torque.
In embodiment 2, tables 641, 642, 643 obtained by subdividing the rotation speed of the motor 23a are used, but the present invention is not limited thereto, and the description method of the tables may be changed to one table. When the difference in rotation speed of the motor 23a is not considered, the table 641 is prepared to calculate the torque constant.
As described above, embodiment 2 actually measures the correspondence between the current and the temperature of the motor 23a and the torque constant of the motor 23a in advance, stores the correspondence in the table 641, and interpolates the content stored in the table 641 in correspondence with the current of the motor 23a and the temperature of the motor 23a as needed to approximate the torque constant. Thus, the calculation accuracy of the torque constant of the disturbance observer 610 improves, and the calculation load can be reduced.
Embodiment 2 also actually measures the correspondence between the current, temperature, and rotation speed of the motor 23a and the torque constant of the motor 23a in advance, stores the correspondence in tables 641, 642, 643, reads the contents stored in tables 641, 642, 643 in correspondence with the current, temperature, and rotation speed of the motor 23a, and interpolates the values as necessary to approximate the torque constant. Thus, the calculation accuracy of the torque constant of the disturbance observer 610 is higher, and the calculation load can be reduced.
Embodiment 3
In embodiment 1, the constant calculating unit 611 calculates the torque constant using a polynomial or a piecewise polynomial of the temperature. In embodiment 2, the constant calculating unit 611 calculates the torque constant by reading the contents stored in the table. In contrast, in embodiment 3, the constant calculation unit 611 corrects the torque constant calculated using the temperature polynomial or the piecewise polynomial based on the contents stored in the table, or corrects the torque constant calculated by reading out the contents stored in the table using the temperature polynomial or the piecewise polynomial.
The table 644 of fig. 10 is recorded in the storage device 64, but may also be recorded in the ROM 62. Table 644 stores torque constants obtained by combining the currents of motor 23a at 100A, 75A, 50A, and 25A with the rotational speeds of motor 23a at 0rpm, 5000rpm, and 10000 rpm. These torque constants are the same as those stored in tables 641, 642, 643 when the temperature is 0 ℃. For example, the torque constant (0.81) at 75A and 5000rpm is the same as the torque constant at 75A and 0 ℃ in the torque constant stored in the table 642 corresponding to 5000 rpm.
In embodiment 3, the relationship between the temperature and the torque constant of the motor 23a is shown in any one of the expressions (1) to (4), and the relationship between the current and the rotation speed of the motor 23a and the torque constant is shown in the table 644. When the temporary torque constant a is calculated using any one of the formulas (1) to (4), the target torque constant is calculated by correcting the torque constant a using the table 644. When the temporary torque constant a is calculated using the table 644, the torque constant a is corrected using any one of the equations (1) to (4) to calculate the target torque constant. To calculate the temporary torque constant a, either one of the equations (1) to (4) may be used first or the table 644 may be used first, or may be determined to be fixed, depending on the setting.
A method of calculating a torque constant using any one of the formulas (1) to (4) and the table 644 will be described with reference to fig. 11. The processing shown in fig. 11 is executed by the CPU 61 as a part of the processing of estimating the disturbance force. The rotation speed in the figure is the rotation speed of the motor 23a calculated by the CPU 61 through the process shown in fig. 7 of embodiment 1.
At the start of the process of fig. 11, the CPU 61 acquires temperature information of the motor 23a from the temperature detecting section 23c (S41), and acquires current information from the current detecting section 237 (S42). The CPU 61 determines whether to use any one of the polynomials of formulas (1) to (3) or the piecewise polynomial of formula (4) first (S43). As described above, this determination may be omitted, and the process may be fixedly transferred to the next step S44 or S51.
When the polynomial or the piecewise polynomial is previously used (S43: YES), the CPU 61 calculates a temporary torque constant A by applying the temperature T indicated by the acquired temperature information to any one of the polynomials of formulas (1) to (3) or the piecewise polynomial of formula (4) (S44). The CPU 61 reads out the contents stored in the table 644 in association with the current indicated by the acquired current information and the rotation speed of the motor 23a (S45), and calculates a temporary torque constant B by linear interpolation (S46).
The CPU 61 also reads out a temporary torque constant C at a current of 4A and a rotational speed of 0rpm from the table 644 (S47), and calculates a ratio D of the torque constant B to the torque constant C (S48). The CPU 61 multiplies the provisional torque constant a by the ratio D to calculate a target torque constant (S49: corresponding to the constant calculating unit 611), and ends the process of fig. 11.
When it is determined in step S43 that the polynomial or piecewise polynomial is not used first (S43: no), the CPU 61 reads out the contents stored in the table 644 in correspondence with the current indicated by the acquired current information and the rotation speed of the motor 23a (S51), and calculates a temporary torque constant a by linear interpolation (S52). The CPU 61 applies the temperature T indicated by the acquired temperature information to any one of the polynomials of formulas (1) to (3) or the piecewise polynomial of formula (4) to calculate a temporary torque constant B (S53). The CPU 61 also calculates a temporary torque constant C at a temperature T of 0 ℃ using the polynomial or piecewise polynomial described above (S54), and passes the process to step S48 to calculate a target torque constant.
In embodiment 3, the torque constants at the temperature of 0 ℃ among the torque constants stored in tables 641, 642, 643 are stored in table 644, but the present invention is not limited thereto. The same results were obtained even when the torque constant at any one of the temperatures of 10 ℃, 20 ℃ and 30 ℃ was stored in table 644.
As described above, in embodiment 3, in addition to the above-described polynomial or piecewise polynomial, the correspondence between the current and rotational speed of the motor 23a and the torque constant of the motor 23a is actually measured in advance and stored in the table 644. When executing the calculation of the torque constant, the temporary torque constant a calculated based on the contents stored in the table 644 corresponding to the current of the motor 23a and the rotation speed of the motor is corrected based on the polynomial or the piecewise polynomial, or the temporary torque constant a calculated by applying the detected temperature to the polynomial or the piecewise polynomial is corrected based on the stored contents of the table 644. Thus, the calculation accuracy of the torque constant of the disturbance observer 610 becomes higher, and the calculation load can be reduced.
(simulation)
The results obtained by modeling the temperature change of each part of the motor 23a and performing the simulation will be described with reference to fig. 12 and 13. In the temperature model of fig. 12, heat transfer is provided between the winding wire and the motor inner air, between the winding wire and the outside air, between the motor inner air and the magnet, and between the motor inner air and the outside air. The heat Qc J supplied to the winding can be expressed by the following equation (5) by the motor current Im a and the winding resistance Rc Ω.
Qc＝Rc×Im 2 ···(5)
The heat Qca transferred from the winding to the air in the motor can be represented by the following formula (6) by the winding temperature Tc [ DEG C ], the air temperature Ta [ DEG C ] in the motor, and the thermal resistance Trca [ sK/J ]. The heat Qcat transferred from the winding to the outside air can be expressed by the following equation (7) by the winding temperature Tc, the outside air temperature Tat, and the thermal resistance Trcat.
Qca＝(Tc-Ta)/Trca···(6)
Qcat＝(Tc-Tat)/Trcat···(7)
The heat Qam transferred from the air in the motor to the magnet can be expressed by the following equation (8) by the air temperature Ta in the motor, the magnet temperature Tm, and the thermal resistance tran. The heat Qaat transferred from the in-motor air to the outside air can be expressed by the following equation (9) by the in-motor air temperature Ta, the outside air temperature Tat, and the thermal resistance Traat.
Qam＝(Ta/Tm)/Tram···(8)
Qaat＝(Ta-Tat)/Traat···(9)
When Hc [ J/K ] is the heat capacity of the winding, ha is the heat capacity of the air in the motor, and Hm is the heat capacity of the magnet, the temperature changes Δtc, Δta, Δtm of the winding, the air in the motor, and the magnet for 1 second can be expressed by the following equations (10), (11), and (12).
ΔTc＝(Qc-Qca-Qcat)/Hc···(10)
ΔTa＝(Qca-Qam-Qaat)/Ha···(11)
ΔTm＝(Qam)/Hm···(12)
Using the above modeling-based formulas (10) to (12), simulations were performed under the following conditions.
Initial value of Tc, ta, tm, tat: 20
Rc＝0.1
Trca＝Tram＝0.05
Traat＝Trcat＝0.1
Hc＝2000，Ha＝100，Hm＝2000
In FIG. 13, the horizontal axis represents time (seconds) and the vertical axis represents temperature (. Degree. C.). In the drawing, a solid line, a broken line, and a dash-dot line indicate the magnet temperature Tm, the winding temperature Tc, and the air temperature Ta in the motor, respectively. The motor current Im is set to 100 a only for a period of time of 0 to 1500 seconds, and then to 0.
From the results of the above simulation, it can be seen that: the temperature Ta of the air in the motor rises slightly later than the winding temperature Tc of the motor 23a, and the temperature Tm of the magnet rises slightly later. After 1500 seconds have elapsed, the winding temperature Tc gradually approaches around 80 ℃, and the in-motor air temperature Ta gradually approaches around 60 ℃ lower than it. The magnet temperature Tm is in heat transfer with only the air in the motor, and thus gradually approaches the same temperature as the air temperature Ta in the motor. The same operation as in the present simulation is performed in real time, and the magnet temperature Tm is obtained from the motor current Im and the outside air temperature Tat. As the outside air temperature Tat, in addition to the direct measurement of the outside air temperature by the temperature sensor, the value of the temperature sensor of the encoder 23b of the motor 23a and the temperature sensor in the control board may be used as a substitute value for the outside air temperature, and an approximation value may be calculated from these values to be used as the outside air temperature.

Claims (7)

1. An interference observer (610) for performing feedback control on a motor (23 a) based on a command, acquiring position information and current information of the motor, and estimating interference acting on the motor, the interference observer (610) comprising:
A constant calculation unit (611) that acquires temperature information of the motor, and calculates a torque constant of the motor based on the temperature indicated by the acquired temperature information;
a torque calculation unit (612) that multiplies the torque constant calculated by the constant calculation unit by a current represented by the acquired current information to calculate the torque of the motor; and
a torque estimation unit (613) that estimates the torque of the motor based on the position indicated by the acquired position information and a constant of the load machine (10, 20, 30, 51) driven by the motor,
wherein the disturbance observer (610) subtracts the torque estimated by the torque estimating section from the torque calculated by the torque calculating section to estimate the disturbance,
the constant calculation unit approximates the torque constant using an n-degree polynomial obtained based on a relationship between the temperature and the torque of the motor, where n is an integer of 1 or more,
a plurality of the polynomials are determined in such a manner as to change the temperature and the power running state or the regeneration state of the motor,
the constant calculating section detects whether the motor is in a power running state or a regenerative state and uses a polynomial corresponding to the detected state,
The polynomial is any one of the following 3 formulas:
Kt＝a-bT
Kt＝a-b(T-c) 2
Kt＝a0+a1T+a2T 2 +···+anT n
wherein, kt: constant of torque
T: the temperature indicated by the temperature information
a. b, c, a0, a1 a2 (a 2) carrying out the following an: a fixed constant or coefficient.
2. The disturbance observer according to claim 1, wherein,
the command is either one or both of a position command and a speed command.
3. The disturbance observer according to claim 2, wherein,
the torque estimation unit estimates torque based on a sum of a product of a rotational speed obtained by first-order differentiating the position indicated by the acquired position information and the viscosity of the load machine, a product of an acceleration obtained by further first-order differentiating the rotational speed and the inertia of the load machine, and a coulomb friction corresponding to the moving direction of the load machine.
4. The disturbance observer according to claim 1, wherein,
further provided with a table (644), wherein the table (644) stores the correspondence relationship between the current and rotation speed of the motor and the torque constant of the motor,
the constant calculation unit calculates a torque constant based on the polynomial and contents stored in the table in correspondence with a current represented by the acquired current information and a rotation speed obtained by first-order differentiating a position represented by the acquired position information.
5. A control device is characterized in that,
the interference observer according to any one of claims 1 to 4 and a control unit (600) that issues the instruction are provided.
6. A machine tool (100) provided with the control device (60), the motor, and the load machine according to claim 5, the machine tool (100) further comprising:
a position detection unit (23 b) that detects the position of the motor and feeds back position information indicating the detected position;
a current detection unit (237) that detects the current of the motor and feeds back current information indicating the detected current; and
a temperature detection unit (23 c) for detecting the temperature of the motor and generating temperature information indicating the detected temperature,
wherein the disturbance observer acquires temperature information from the temperature detection section.
7. A disturbance estimation method for performing feedback control on a motor based on an instruction, acquiring position information and current information of the motor to estimate disturbance acting on the motor, the disturbance estimation method comprising the steps of:
acquiring temperature information of the motor, and calculating a torque constant of the motor based on a temperature indicated by the acquired temperature information;
Multiplying the calculated torque constant by a current represented by the acquired current information to calculate a torque of the motor;
estimating a torque of the motor based on a position indicated by the acquired position information and a constant of a load machine driven by the motor; and
subtracting the estimated torque from the calculated torque to estimate the disturbance,
in the step of calculating the torque constant of the motor, the torque constant is approximated using a polynomial of degree n obtained based on a relation between the temperature and the torque of the motor, where n is an integer of 1 or more,
a plurality of the polynomials are determined in such a manner as to change the temperature and the power running state or the regeneration state of the motor,
detecting whether the motor is in a power running state or a regeneration state and using a polynomial corresponding to the detected state,
the polynomial is any one of the following 3 formulas:
Kt＝a-bT
Kt＝a-b(T-c) 2
Kt＝a0+a1T+a2T 2 +···+anT n
wherein, kt: constant of torque
T: the temperature indicated by the temperature information
a. b, c, a0, a1 a2 (a 2) carrying out the following an: a fixed constant or coefficient.
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