JP7298119B2 - Disturbance observer, control device, machine tool, and disturbance estimation method - Google Patents

Description

The present invention relates to a disturbance observer for a feedback control system, a control device, a machine tool, and a disturbance estimation method.

Conventionally, a disturbance observer is used to estimate the disturbance affecting the system as part of the state of the controlled object. In a disturbance observer used in a motor feedback control device, the torque constant used to calculate the output torque of the motor from the current flowing through the motor may be treated as a constant value that does not depend on temperature.

For example, Patent Document 1 discloses a technique for detecting a collision of a driven body and stopping a motor when the magnitude of a disturbance torque estimated by a disturbance observer incorporated in a velocity loop of a servo circuit exceeds a set value. disclosed.

JP-A-03-196313

However, according to the technique disclosed in Patent Document 1, the torque constant Kt, which actually varies with temperature, is set to a constant value. Therefore, when the temperature of the motor rises, an error in the estimated disturbance torque increases. For this reason, depending on the temperature of the motor, it may be erroneously detected that the motor is driving the driven body with a drive load higher than it actually is, or a collision may be erroneously detected even though the driven body is not colliding. There was a fear that

The present invention has been made in view of such circumstances, and its object is to provide a disturbance observer, a control device, a machine tool, and a disturbance estimation method capable of reducing errors in estimated disturbances. It is in.

A disturbance observer according to the present invention is a disturbance observer that acquires position information and current information of the motor, which are fed back to a servo circuit that feedback-controls the motor based on a command, and estimates disturbance acting on the motor, a constant calculation unit that obtains temperature information of the motor and calculates a torque constant of the motor based on the temperature indicated by the obtained temperature information; and a torque estimating unit for estimating the torque of the motor based on the position indicated by the acquired position information and the constant related to the load machine driven by the motor, The torque estimated by the torque estimator is subtracted from the torque calculated by the torque calculator to estimate the disturbance, and the constant calculator calculates the n-th order ( (n is an integer of 1 or more) is used to approximate the torque constant .
The disturbance observer according to the present invention is characterized in that the polynomial is any one of the following three expressions.
Kt = a-bT
Kt = a - b (T - c) ²
Kt=a0+a1T+a2T2 ⁺ ...+ ^anTn
however,
Kt: torque constant
T: temperature indicated by the temperature information
a, b, c, a0, a1, a2, . . . an: constant constant or coefficient
The disturbance observer according to the present invention further includes a table that stores a correspondence relationship between the current and rotation speed of the motor and the torque constant of the motor. The torque constant is calculated based on the content stored in the table corresponding to the rotation speed obtained by differentiating the position indicated by the position information once and the polynomial.
A disturbance observer according to the present invention is a disturbance observer that acquires position information and current information of the motor, which are fed back to a servo circuit that feedback-controls the motor based on a command, and estimates disturbance acting on the motor, a constant calculation unit that obtains temperature information of the motor and calculates a torque constant of the motor based on the temperature indicated by the obtained temperature information; and a torque estimating unit for estimating the torque of the motor based on the position indicated by the acquired position information and the constant related to the load machine driven by the motor, The torque estimated by the torque estimator is subtracted from the torque calculated by the torque calculator to estimate the disturbance, and the constant calculator calculates a section defined by a section including the temperature indicated by the temperature information. It is characterized by approximating a torque constant using a polynomial.
The disturbance observer according to the present invention further includes a table that stores a correspondence relationship between the current and rotation speed of the motor and the torque constant of the motor. The torque constant is calculated based on the piecewise polynomial and the contents stored in the table corresponding to the rotation speed obtained by differentiating the position indicated by the position information once.

A disturbance observer according to the present invention is characterized in that the command is a position command and/or a speed command, and the servo circuit controls the current flowing through the motor.

In the disturbance observer according to the present invention, the torque estimating unit is configured such that the product of the rotational speed obtained by differentiating the position indicated by the acquired position information once and the viscous resistance of the load machine, and the acceleration obtained by further differentiating the rotational speed once and the torque is estimated based on the sum of the product of the moment of inertia of the load machine and the Coulomb frictional force according to the moving direction of the load machine.

A control device according to the present invention includes the disturbance observer described above and a control section that issues the command.

A machine tool according to the present invention includes the control device, the servo circuit, the motor, and the load machine described above, wherein the position of the motor is detected, and position information indicating the detected position is detected. to the servo circuit; a current detection unit that detects the current of the motor and feeds back current information indicating the detected current to the servo circuit; and detects the temperature of the motor and detects the detected temperature and a temperature detection unit that generates temperature information indicating that the disturbance observer acquires the temperature information from the temperature detection unit.

A disturbance estimation method according to the present invention acquires position information and current information of the motor, which are fed back to a servo circuit that feedback-controls the motor based on a command, and estimates disturbance acting on the motor, a step of obtaining temperature information of the motor and calculating a torque constant of the motor based on the temperature indicated by the obtained temperature information; estimating the torque of the motor based on the position indicated by the acquired position information and a constant related to the load machine driven by the motor; and subtracting the estimated torque from the calculated torque to eliminate the disturbance. In the step of calculating the torque constant, the torque constant is approximated using an n-th order (n is an integer of 1 or more) polynomial based on the relationship between the temperature and the torque of the motor. and
A disturbance estimation method according to the present invention acquires position information and current information of the motor, which are fed back to a servo circuit that feedback-controls the motor based on a command, and estimates disturbance acting on the motor, a step of obtaining temperature information of the motor and calculating a torque constant of the motor based on the temperature indicated by the obtained temperature information; estimating the torque of the motor based on the position indicated by the acquired position information and a constant related to the load machine driven by the motor; and subtracting the estimated torque from the calculated torque to eliminate the disturbance. and the step of estimating, wherein the step of calculating the torque constant approximates the torque constant using a piecewise polynomial defined in an interval including the temperature indicated by the temperature information.

In the present invention, the torque constant of the motor is calculated based on the temperature of the motor, the calculated torque constant is multiplied by the current of the motor to calculate the torque of the motor, and the constant related to the position of the motor and the load machine driven by the motor is calculated. and subtracting the estimated motor torque from the calculated motor torque to estimate the disturbance acting on the motor. As a result, since the torque constant is corrected according to the temperature of the motor, the actual torque of the motor including the torque against the disturbance can be calculated with high accuracy, and the calculation accuracy of the disturbance is improved. Also, the relation between the temperature and the torque of the motor is actually measured in advance to form an n-th order polynomial, and the detected motor temperature is applied to this equation to approximate the torque constant. This makes it possible to determine the polynomial applied to all sections or individual sections by considering the curvature of the curve indicated by the actual measurement results, inflection points, and the number of actual measurement points. improves.
In the present invention, the polynomial is any one of the three equations mentioned above.
In the present invention, in addition to predetermining the above-described polynomial, the correspondence relationship between the motor current and rotation speed and the motor torque constant is measured in advance and stored in a table. When the torque constant is calculated during execution, the torque constant calculated based on the contents stored in the table corresponding to the motor current and the motor rotation speed is corrected based on the above-described polynomial, or the above-described The torque constant calculated by applying the detected temperature to the polynomial is corrected based on the stored contents of the table. As a result, the torque constant can be calculated more accurately and the calculation load can be reduced.
In the present invention, the torque constant of the motor is calculated based on the temperature of the motor, the calculated torque constant is multiplied by the current of the motor to calculate the torque of the motor, and the constant related to the position of the motor and the load machine driven by the motor is calculated. and subtracting the estimated motor torque from the calculated motor torque to estimate the disturbance acting on the motor. As a result, since the torque constant is corrected according to the temperature of the motor, the actual torque of the motor including the torque against the disturbance can be calculated with high accuracy, and the calculation accuracy of the disturbance is improved. Also, the relationship between motor temperature and torque is actually measured in advance to form a piecewise polynomial, and the detected motor temperature is applied to this equation to approximate the torque constant. As a result, it is possible to determine the polynomial applied to all sections or individual sections in consideration of the curvature of the curve indicated by the actual measurement results, the point of inflection, and the number of actual measurement points. Improves accuracy.
In the present invention, in addition to predetermining the piecewise polynomial, the relationship between the motor current and rotation speed and the motor torque constant is actually measured in advance and stored in a table. When the torque constant is calculated during execution, the torque constant calculated based on the contents stored in the table corresponding to the motor current and the motor rotation speed is corrected based on the above-mentioned piecewise polynomial, or the above-mentioned The torque constant calculated by applying the detected temperature to the piecewise polynomial is corrected based on the contents of the table. As a result, the torque constant can be calculated more accurately and the calculation load can be reduced.

In the present invention, the current flowing through the motor is controlled according to either or both of the issued position command and speed command. As a result, the current of the motor that produces the torque of the motor is feedback-controlled in accordance with the content of the command, so that the position and/or speed of the motor converges to the commanded target.

In the present invention, the viscous torque is calculated by multiplying the rotational speed obtained by differentiating the position of the motor once by the viscous resistance of the load machine, and the acceleration obtained by differentiating the rotational speed once more is multiplied by the moment of inertia of the load machine. The torque is estimated by adding the calculated inertia torque and the Coulomb frictional force whose sign changes plus/minus according to the moving direction of the load machine. As a result, since the torque of the motor is estimated by combining the moment of inertia, viscous resistance, and Coulomb friction of the load machine including the motor, the torque of the motor excluding disturbance can be accurately estimated.

In the present invention, a disturbance observer that estimates disturbances with high accuracy can be applied to a control device that controls a load machine.

In the present invention, the control unit of the control device issues a command to the servo circuit, and the servo circuit that receives the command feedback-controls the motor that drives the load machine. A disturbance observer of the control device obtains motor position information and current information fed back to the servo circuit from the position detection section and the current detection section, respectively, and temperature information from the temperature detection section to estimate the disturbance. As a result, the disturbance acting on the motor via the load machine can be estimated with high accuracy.

According to the present invention, it is possible to reduce errors in estimated disturbances.

1 is a perspective view showing a machine tool according to Embodiment 1; FIG. It is a block diagram which shows a control apparatus. 3 is a block diagram showing information exchanged inside and outside the control device and the X-axis motor; FIG. 3 is a block diagram showing the functional configuration of a servo circuit; FIG. It is a block diagram which shows the functional structure of a disturbance observer. 4 is a flow chart showing a processing procedure of a CPU for estimating a disturbance force with a disturbance observer according to Embodiment 1; 4 is a flow chart showing the processing procedure of a CPU for detecting the rotation direction of a motor and calculating the rotation speed and acceleration; 4 is a chart showing the contents of a table that stores a correspondence relationship between motor current, temperature, rotational speed, and torque constant; 10 is a flow chart showing a processing procedure of a CPU for estimating a disturbance force with a disturbance observer according to Embodiment 2; 4 is a chart showing the contents of a table that stores a correspondence relationship between a motor current and rotation speed and a torque constant; 11 is a flow chart showing a processing procedure of a CPU for calculating a torque constant with a disturbance observer according to Embodiment 3; FIG. 3 is an explanatory diagram schematically showing a temperature model of a motor; 4 is a graph showing a simulation result of temperature change of each part of the motor;

Hereinafter, the present invention will be described in detail based on the drawings showing its embodiments.
(Embodiment 1)
FIG. 1 is a perspective view showing a machine tool 100 according to Embodiment 1. FIG. In the following description, up/down, left/right, and front/rear directions indicated by arrows in the drawing are used. As shown in FIG. 1, a machine tool 100 includes a rectangular base 1 extending forward and backward. The work holding part 3 is provided on the front side of the upper part of the base 1 . The work holding part 3 is rotatable around an A axis extending horizontally and a C axis extending vertically. A support base 2 is provided on the rear side of the upper part of the base 1 and supports the upright column 4. - 特許庁

A Y-axis direction moving mechanism 10 (corresponding to a load machine) is provided above the support table 2 and moves a moving plate 16 in the front-rear direction. The Y-axis movement mechanism 10 includes two tracks 11 extending back and forth, a Y-axis screw shaft 12 , a Y-axis motor 13 and bearings 14 . Tracks 11 are provided on the left and right sides of the upper part of support base 2 . The Y-axis screw shaft 12 extends back and forth and is provided between the two tracks 11 . The bearings 14 are 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 onto the Y-axis screw shaft 12 via rolling elements (not shown). The rolling bodies are, for example, balls. A plurality of sliders 15 are slidably provided on each track 11 . The moving plate 16 extends horizontally and is connected to the top of the nut and slider 15 . The Y-axis screw shaft 12 is rotated by the 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 vertical column 4 in the horizontal direction. The X-axis movement mechanism 20 includes two tracks 21 extending left and right, an X-axis screw shaft 22, an X-axis motor 23 (see FIG. 2), and a bearing 24. As shown in FIG. Tracks 21 are provided in front and rear of the upper surface of moving plate 16 . The X-axis screw shaft 22 extends left and right and is provided between the two tracks 21 . The bearings 24 are 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 onto the X-axis screw shaft 22 via rolling elements (not shown). A plurality of sliders 26 are slidably provided on each track 21 . The upright 4 is connected to the upper part of the nut and slider 26 . The X-axis screw shaft 22 is rotated by the rotation of the X-axis motor 23, the nut moves in the left-right direction, and the vertical column 4 moves in the left-right direction.

A Z-axis direction moving mechanism 30 (corresponding to a load machine) is provided on the front surface of the vertical column 4 and moves the spindle head 5 in the vertical direction. The Z-axis movement mechanism 30 includes two vertically extending tracks 31 , a Z-axis screw shaft 32 , a Z-axis motor 33 and bearings 34 . Tracks 31 are provided on the left and right sides of the front surface of the upright column 4 . The Z-axis screw shaft 32 extends vertically and is provided between the two tracks 31 . The bearings 34 are provided at the lower end portion and the 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 onto the Z-axis screw shaft 32 via rolling elements (not shown). A plurality of sliders 35 are slidably provided on each track 31 . The spindle head 5 connects to the front of the nut and slider 35 . The Z-axis screw shaft 32 is rotated by the rotation of the Z-axis motor 33, the nut moves vertically, and the spindle head 5 moves vertically.

A vertically extending spindle 51 (corresponding to a load machine) is provided in the spindle head 5 . The main shaft 51 rotates about its axis. A spindle motor 6 is provided at the upper end of the spindle head 5 . A tool is mounted on the lower end of the spindle 51 . The spindle 51 is rotated by the rotation of the spindle motor 6, and the tool is rotated. The rotated tool processes the work held by the work holding part 3 .

FIG. 2 is a block diagram showing the control device 60. As shown in FIG. The machine tool 100 includes a control device 60 that controls the driving of the spindle motor 6, the Y-axis motor 13, the X-axis motor 23, the Z-axis motor 33, the workpiece holder 3, and the like. As shown in FIG. 2, the control device 60 has a CPU 61, a ROM 62, a RAM 63, a nonvolatile storage device 64 such as an EEPROM, an input interface 65, an input/output interface 66, and the like. A storage device 64 stores a machining program for machining a workpiece. A machining program comprises a plurality of lines (instructions). The CPU 61 reads lines in order, executes instructions, and issues commands for driving each section.

The machine tool 100 further includes a reception section 67 (setting section), a Z-axis sensor 68 and a spindle sensor 69 . The receiving unit 67 includes, for example, a keyboard, a touch panel, a display screen, etc., and receives user's operations. The user sets execution of a specific process in the storage device 64 via the reception unit 67, for example. The Z-axis sensor 68 detects the vertical position of the main shaft 51 , in other words, the axial position of the main shaft 51 . A spindle sensor 69 detects the circumferential position of the spindle 51 . The control device 60 inputs settings from the reception unit 67 via the input interface 65 , inputs the axial position from the Z-axis sensor 68 , and inputs the rotation speed from the spindle sensor 69 . The control device 60 issues 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 position information and current information of each 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 . The positional information of the Z-axis motor 33 and the main shaft motor 6 are provided in the Z-axis motor 33 and the main shaft motor 6 instead of the Z-axis sensor 68 and the main shaft sensor 69, which correspond to the encoder 23b shown in FIG. You may detect using an encoder.

When the CPU 61 executes machining processing, the CPU 61 issues commands to the main shaft motor 6, the X-axis motor 23, the Y-axis motor 13, and the Z-axis motor 33 to rotate the main shaft 51, move the X-axis direction moving mechanism 20, It controls the movements of the Y-axis direction moving mechanism 10 and the Z-axis direction moving mechanism 30 . Thereby, the CPU 61 uses the tool attached to the spindle 51 to machine the workpiece.

Next, the flow of information between the X-axis motor 23 and the control device 60 will be described as an example. The same applies to the information flow between the Y-axis motor 13 and the control device 60, the information flow between the Z-axis motor 33 and the control device 60, and the information flow between the spindle motor 6 and the control device 60. FIG. 3 is a block diagram showing information exchanged inside and outside the control device 60 and the X-axis motor 23. As shown in FIG. The control unit 600 and the disturbance observer 610 included in the control device 60 are one of functional blocks realized by the control device 60 having the CPU 61 shown in FIG. The X-axis motor 23 includes a motor 23a that drives the X-axis screw shaft 22, and a servo circuit 230 that feedback-controls the current flowing through the motor 23a based on one or both of a position command and a speed command from the control unit 600. have. A current detection unit 237 detects the current flowing through the motor 23 a , and the current detection unit 237 feeds back current information indicating the detected current to the servo circuit 230 .

The motor 23a is, for example, an AC servomotor having a magnet in its rotor. The rotational position of the motor 23a is detected by an encoder 23b (corresponding to a position detector), 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 detector 23c, and the temperature information indicating the detected temperature is provided to the disturbance observer 610. FIG. The temperature detection unit 23c preferably detects the temperature of the magnet of the rotor (hereinafter referred to as magnet temperature).

If it is difficult to directly detect the magnet temperature, 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). As a substitute for the magnet temperature, the temperature of a portion different from the magnet, such as the case temperature of the motor 23a and the temperature of the encoder 23b, may be used.

The disturbance observer 610 acquires position information and current information fed back to the servo circuit 230 and temperature information from the temperature detection unit 23c, and estimates disturbance acting on the motor 23a, that is, disturbance force as disturbance torque. . The disturbance observer 610 may acquire position information and current information without going through the servo circuit 230 . For example, when the disturbance force estimated by the disturbance observer 610 exceeds a predetermined threshold value, the control unit 600 can issue a predetermined alarm or issue a command to stop the motor 23a.

Next, the operation of the servo circuit 230 that receives a position command from the control unit 600 will be described as an example. FIG. 4 is a block diagram showing the functional configuration of the servo circuit 230. As shown in FIG. The same applies to the servo circuits of the Y-axis motor 13, the Z-axis motor 33 and the spindle motor 6. 231, 233 and 235 in the figure represent amplifiers whose amplification factors are position proportional gain, velocity proportional gain and velocity integral gain, respectively. The servo circuit 230 has an amplifier 231 that amplifies a position error, which is the difference between the target position included in the position command and the position indicated by the position information fed back by the encoder 23b, to generate a speed command. The servo circuit 230 also has a differentiator 232 that differentiates once the position indicated by the position information to generate the rotation speed of the motor 23a, and a difference between the speed command generated by the amplifier 231 and the rotation speed generated by the differentiator 232. It has an amplifier 233 that amplifies a certain speed error, and an integrator 234 and an amplifier 235 that integrate and amplify the speed error.

In the example shown in FIG. 4, the sum of the amount proportional to the speed error amplified by the amplifier 233 and the amount proportional to the integration result of the speed error amplified by the amplifier 235 is used as the current command. Thus, so-called PI control is performed. The servo circuit 230 further has a current controller 236 that feedback-controls the current flowing through the motor 23a based on the current command. The current detector 237 feeds back current information indicating the detected current to the current controller 236, and the current controller 236 controls the current according to the current command to flow through the motor 23a.

In FIG. 4, the operation of the servo circuit 230 has been described in the case where the control unit 600 issues a position command. A speed command from the control unit 600 may be used. When the control unit 600 issues a position command and a speed command simultaneously, the operations when issuing each command alone may be superimposed.

Next, the operation of disturbance observer 610 will be described. FIG. 5 is a block diagram showing the functional configuration of the disturbance observer 610. As shown in FIG. The same applies to disturbance observers for the Y-axis motor 13, Z-axis motor 33, and spindle motor 6. FIG. The disturbance observer 610 acquires temperature information from the temperature detection unit 23c, and calculates a torque constant based on the temperature indicated by the acquired temperature information. and a torque calculator 612 that calculates the torque of the motor 23a by multiplying the current indicated by the acquired current information. The torque calculated by the torque calculator 612 includes torque that resists disturbance. The disturbance observer 610 also has a torque estimator 613 that estimates the torque of the motor 23 a based on the position indicated by the acquired position information and constants related to the X-axis direction moving mechanism 20 .

The constant calculator 611 applies the temperature T indicated by the acquired temperature information to an n-th order (n is an integer equal to or greater than 1) polynomial or piecewise polynomial to approximate the torque constant Kt. The polynomial here is a linear expression of the temperature T such as the following expression (1), a secondary expression of the temperature T such as the expression (2), or It is an nth order expression of the temperature T like the expression (3). Generally, the higher the temperature of the motor 23a, the higher the temperature of the magnet of the rotor of the motor 23a, and the lower the magnetic flux density of the magnet, resulting in a smaller torque constant. By measuring the relationship between the temperature and torque of the motor 23a in advance, it is possible to formulate an equation that best expresses the relationship between temperature and torque in consideration of the curvature of the curve indicated by the actual measurement results, the point of inflection, and the number of actual measurement points.

Kt=a−bT (1)
Kt = a - b (T - c) ² (2)
Kt=a0+a1T+ ^a2T2 +...+ ^anTn (3)
where a, b, c, a0, a1, a2, . . . an are constant constants or coefficients

Instead of the above equations (1) to (3), for example, a function Sj such as the following equation (4) for spline interpolation in the interval [Tj, Tj+1] (j=0, 1, 2 . . . ) (T) may be determined in advance by actual measurement. In this case, the constant calculator 611 sets the value of the function Sj(T) defined in the interval [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)
where aj, bj, cj, and dj are constant coefficients or constants

A torque estimating unit 613 includes a direction detector 614 that detects the rotation direction of the motor 23a, that is, the moving direction of the X-axis direction moving mechanism 20, based on the acquired position information, and a direction detector 614 that differentiates once the position indicated by the acquired position information. and a differentiator 616 that differentiates once the rotational speed generated by the differentiator 615 to generate acceleration. 617 further included in the torque estimation unit 613 in FIG. 5 is an output unit that outputs a positive or negative Coulomb frictional force acting on the X-axis direction moving mechanism 20 including the motor 23a. 618 and 619 in FIG. 5 represent multipliers for multiplying the viscous resistance and moment of inertia of the X-axis movement mechanism 20 including the motor 23a.

The direction detector 614 may, for example, calculate the difference between the previous value of the position information and the current value, and output the sign of the difference. Direction detector 614 may detect the direction of rotation of motor 23a using a known hardware circuit. The output unit 617 outputs plus and minus frictional torque according to the detection result of the direction detector 614 .

The differentiator 615 calculates, for example, the difference between the previous value of the position information and the current value, and divides the difference by the acquisition interval time of the position information to calculate the rotational speed. The differentiator 616 calculates the acceleration by calculating the difference between the previous value and the current value of the rotation speed calculated by the differentiator 615, for example, and dividing the difference by the positional information acquisition interval time.

A multiplier 618 multiplies the rotational speed generated by the differentiator 615 by the viscous resistance and outputs viscous torque. A multiplier 619 multiplies the acceleration generated by the differentiator 616 by the moment of inertia to output an inertia torque. The torque estimated by the torque estimator 613 is obtained by adding these frictional torque, viscous torque, and inertia torque. The disturbance observer 610 estimates the disturbance force by subtracting the torque estimated by the torque estimator 613 from the torque calculated by the torque calculator 612, that is, the torque calculated including the torque against the disturbance. The viscous resistance is calculated from the proportional relationship between the speed and the torque value by measuring the torque value while the motor 23a is rotating at a constant speed for a plurality of rotation speeds. For a plurality of accelerations, the moment of inertia is calculated by measuring torque values while the motor 23a is rotating at a constant acceleration and calculating the proportional relationship between the acceleration and the torque value. A value calculated from the design drawing of the load machine may be used as the moment of inertia.

The operation of the disturbance observer 610 described above will be described below using a flowchart. The same applies to the Y-axis motor 13, the Z-axis motor 33, and the spindle motor 6. FIG. 6 is a flow chart showing the processing procedure of the CPU 61 for estimating the disturbance force with the disturbance observer 610 of the first embodiment. FIG. 7 is a flow chart showing the processing procedure of the CPU 61 for detecting the rotation direction of the motor 23a and calculating the rotation speed and acceleration. The processing shown in FIG. 6 is activated at regular intervals (for example, every 1 ms).

When the process of FIG. 6 is started, the CPU 61 acquires the temperature information of the motor 23a from the temperature detector 23c (S11), and sets the temperature T indicated by the acquired temperature information to any one of equations (1) to (3). or the piecewise polynomial of equation (4) to calculate the torque constant Kt (S12: corresponding to the constant calculator 611). Next, the CPU 61 causes the torque estimator 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. ).

Thereafter, the CPU 61 acquires current information from the current detection unit 237 via the servo circuit 230 or directly (S14), and multiplies the current indicated by the acquired current information by the torque constant calculated in step S12. The torque of the motor 23a is calculated (S15: corresponding to the torque calculation section 612). Then, 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 processing of FIG.

Next, 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, for example, as described above (S21: the direction detector 614 equivalent). Depending on the direction of rotation detected by the direction detector 614, the output section 617 shown in FIG. 5 outputs a positive or negative frictional force. Next, the CPU 61 calculates the rotational speed of the motor 23a as a numerical value proportional to, for example, the reciprocal of the positional information acquisition interval (S22: corresponding to the differentiator 615). Next, the CPU 61 calculates the acceleration of the motor 23a as a numerical 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 processing of FIG.

In the first embodiment, the torque constant is assumed to be independent of the rotation speed of the motor 23a. torque constant becomes smaller. In this case, a plurality of polynomials of any one of the equations (1) to (3) or the piecewise polynomial of the equation (4) may be determined based on the results of actual measurements while changing the temperature and current of the motor 23a in advance. The constant calculator 611 may calculate the torque constant using a polynomial or piecewise polynomial corresponding to the detected current of the motor 23a.

The torque constant also differs depending on whether the motor 23a is in a power running state or in a regenerative state. When considering regeneration, any polynomial of equations (1) to (3) or a piecewise polynomial of equation (4) is calculated based on the results of actual measurements while changing the temperature and powering/regeneration state of the motor 23a in advance. You can define more than one. The constant calculator 611 may detect the power running and regeneration states of the motor 23a and calculate the torque constant using a polynomial or piecewise polynomial corresponding to the detected state.

As described above, according to the first embodiment, the torque constant of the motor 23a is calculated based on the temperature of the motor 23a, and the torque of the motor 23a is calculated by multiplying the current of the motor 23a by the calculated torque constant. The torque of the motor 23a is estimated based on the position of the motor 23a and the constant related to 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 act on the motor 23a. A disturbance force is estimated as a disturbance torque. As a result, since the torque constant is corrected according to the temperature of the motor 23a, the actual torque of the motor 23a including the torque against the disturbance can be calculated with high accuracy, and the calculation accuracy of the disturbance is improved. Therefore, it is possible to reduce the error of the estimated disturbance.

Further, according to the first embodiment, the current flowing through the motor 23a is controlled according to either or both of the issued position command and speed command. Therefore, since the motor current that generates the torque of the motor 23a is feedback-controlled according to the contents of the command, the position and/or speed of the motor 23a converges to the commanded target.

Furthermore, according to the first embodiment, the inertia torque calculated by multiplying the rotational speed obtained by differentiating the position of the motor 23a once by the moment of inertia of the load machine, and the acceleration obtained by further differentiating the rotational speed once, The torque is estimated by adding the viscous torque calculated by multiplying the viscous resistance of the movement mechanism 20 and the Coulomb friction force whose sign changes plus/minus according to the movement direction of the X-axis direction movement mechanism 20 . Therefore, since the torque of the motor 23a is estimated by combining the moment of inertia, viscous resistance, and Coulomb friction of the X-axis direction moving mechanism 20 including the motor 23a, the torque of the motor 23a can be accurately estimated without disturbance.

Furthermore, according to the first embodiment, the relationship between the temperature and the torque of the motor 23a is actually measured in advance to form an n-th order polynomial or piecewise polynomial, and the detected temperature of the motor 23a is applied to this equation to approximate the torque constant. do. Therefore, considering the curvature of the curve indicated by the actual measurement results, the inflection point, and the number of actual measurement points, it is possible to determine the polynomial applied to all sections or individual sections. Improves constant approximation accuracy.

Furthermore, according to Embodiment 1, the disturbance observer 610 that estimates the disturbance with high accuracy can be applied to the control device 60 that controls the X-axis direction moving mechanism 20 .

Furthermore, according to Embodiment 1, the control unit 600 of the control device 60 issues, for example, a position command to the servo circuit 230, and the servo circuit 230 that receives the position command activates the motor 23a that drives the X-axis direction moving mechanism 20. feedback control. A 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 from the encoder 23b and the current detection unit 237, and temperature information from the temperature detection unit 23c, and detects the disturbance. presume. Therefore, the disturbance acting on the motor 23a via the X-axis direction moving mechanism 20 can be estimated with high accuracy.

(Embodiment 2)
In the first embodiment, the constant calculator 611 calculates the torque constant using a temperature polynomial or piecewise polynomial. It is a form in which the torque constant is calculated by Here, the relationship between more variables including temperature and the torque constant is stored in a table. Although the motor 23a of the X-axis motor 23 will be described in the second embodiment and a third embodiment to be described later, other motors of the Y-axis motor 13 and the Z-axis motor 33 are similarly described.

FIG. 8 is a diagram showing contents of tables 641, 642, and 643 that store correspondence relationships between the current, temperature, and rotational speed of the motor 23a and the torque constants. These tables are recorded in the storage device 64, but may be recorded in the ROM 62 as well. Tables 641, 642 and 643 store the relationship between the current and temperature of the motor 23a and the torque constant when the rotation speed of the motor 23a is 0 rpm, 5000 rpm and 10000 rpm, respectively. Of the tables 641, 642, and 643, the basic one is the table 641 corresponding to the case where the rotation speed of the motor 23a is 0 rpm. In each table, the base case is the case where the temperature is 0° C. and the current is 50 A, and the higher the temperature or the higher the current, the smaller the torque constant.

For example, when the current is 50 A in the table 641, the torque constants at temperatures of 0° C., 10° C., 20° C. and 30° C. are stored as 1, 0.99, 0.98 and 0.97. . This corresponds to the fact that the magnetic flux density of neodymium magnets generally used in AC servomotors decreases by about 0.1% with respect to a temperature rise of 1°C. Table 641 shows that for the same temperature, the torque constant of the motor decreases when the current is greater than 50A. Such tendency is the same for tables 642 and 643 as well. On the other hand, in table 642, it is assumed that a current of 10 A is flowing due to field-weakening control because the rotational speed of motor 23a has increased, and the torque constant is lower than that in table 641. Table 643 assumes a field-weakening current of 20 A, which further reduces the torque constant.

Next, a method for calculating the torque constant based on the contents stored in the table shown in FIG. 8 will be described using a flowchart. FIG. 9 is a flow chart showing the processing procedure of the CPU 61 for estimating the disturbance force with the disturbance observer 610 of the second embodiment. The processing shown in FIG. 9 is activated at regular intervals (for example, every 1 ms). The rotation speed and acceleration in the figure are the rotation speed and acceleration of the motor 23a calculated by the CPU 61 in the processing shown in FIG. 7 of the first embodiment.

When the process of FIG. 9 is started, the CPU 61 acquires the current information from the current detection unit 237 via the servo circuit 230 or directly (S31), and further acquires the temperature information of the motor 23a from the temperature detection unit 23c. (S32). Next, the CPU 61 reads the contents stored in any one of the tables 641, 642, and 643 corresponding to the current indicated by the acquired current information, the temperature indicated by the acquired temperature information, and the rotational speed of the motor 23a (S33). Specifically, the CPU 61 selects two tables that are close to the calculated rotation speed, and reads the contents of four cells that are close to the acquired current and temperature from each table. More specifically, for example, when the rotation speed is 500 rpm, the acquired current is 35 A, and the acquired temperature is 5° C., the CPU 61 reads 1, 0.99, 1, 0.99 from the table 641 and reads 0 from the table 642. .67, 0.66, 0.6, 0.59.

After that, the CPU 61 calculates one torque constant by linear interpolation, for example, based on the eight torque constants read out in step S33 (S34: corresponding to the constant calculator 611). Next, the CPU 61 estimates the torque of the motor 23a by means of the aforementioned torque estimating section 613 based on the rotational direction, rotational speed and acceleration of the motor 23a (S35: corresponding to the torque estimating section 613). The CPU 61 further multiplies the current indicated by the current information obtained 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). Then, 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 processing of FIG.

The torque constant also differs depending on whether the motor 23a is in the power running state or in the regenerative state. If this is taken into account, the tables shown in FIG. 8 should be prepared separately for the power running state and the regenerative state. Here, "powering" means a state in which the motor 23a is doing work to the outside, and specifically, it is a case where the rotational speed and the torque of the motor 23a have the same sign. Here, regeneration represents a state in which the motor 23a is working from the outside, and specifically, it is a case where the sign of the rotation speed and the torque of the motor 23a are different.

In the second embodiment, the tables 641, 642, and 643 subdivided according to the rotational speed of the motor 23a are used, but the present invention is not limited to this. can be If the difference in rotational speed of the motor 23a is not taken into consideration, only the table 641 should be prepared to calculate the torque constant.

As described above, according to the second embodiment, the correspondence relationship between the current and temperature of the motor 23a and the torque constant of the motor 23a is actually measured in advance and stored in the table 641. The contents stored in the table 641 corresponding to the temperature are interpolated as necessary to approximate the torque constant. Therefore, it is possible to improve the calculation accuracy of the torque constant and reduce the calculation load.

Further, according to Embodiment 2, the correspondence relationship between the current, temperature, and rotation speed of the motor 23a and the torque constant of the motor 23a is actually measured in advance and stored in the tables 641, 642, and 643, and the The contents stored in the tables 641, 642 and 643 are read out corresponding to the current, temperature and rotational speed, and interpolated as necessary to approximate the torque constant. Therefore, the calculation accuracy of the torque constant is improved, and the calculation load can be reduced.

(Embodiment 3)
In the first embodiment, the constant calculation unit 611 calculates the torque constant using a temperature polynomial or piecewise polynomial. In the second embodiment, the constant calculation unit 611 reads the contents stored in the table. It was in the form of calculating the torque constant. In contrast, in the third embodiment, the constant calculation unit 611 corrects the torque constant calculated using the temperature polynomial or piecewise polynomial based on the contents stored in the table, or stores the torque constant in the table. This is a form in which a torque constant calculated by reading certain content is corrected using a temperature polynomial or piecewise polynomial. The table used here is part of the tables 641, 642, and 643 used in the second embodiment.

FIG. 10 is a diagram showing the contents of a table 644 that stores the correspondence between the current and rotational speed of the motor 23a and the torque constant. Although this table is recorded in the storage device 64, it may be recorded in the ROM 62 as well. The table 644 stores torque constants for 12 combinations of currents of the motor 23a of 100A, 75A, 50A and 25A and rotation speeds of the motor 23a of 0 rpm, 5000 rpm and 10000 rpm. These torque constants are the same as the torque constants stored in the tables 641, 642, 643 when the temperature is 0.degree. For example, the torque constant (0.81) when the current is 75 A and the rotation speed is 5000 rpm is the torque constant stored in the table 642 corresponding to the rotation speed of 5000 rpm when the current is 75 A and the temperature is 0. It is the same as the torque constant for °C.

In the third embodiment, the relationship between the temperature of the motor 23a and the torque constant is represented by one of the equations (1) to (4), and the relationship between the current and rotation speed of the motor 23a and the torque constant is shown in a table 644. is represented in If the provisional torque constant A is calculated using any one of the equations (1) to (4), the torque constant A is corrected using the table 644 to calculate the target torque constant. On the other hand, when the provisional torque constant A is calculated using the table 644 in advance, the torque constant A is corrected using one of the equations (1) to (4) to calculate the target torque constant. Whether one of the formulas (1) to (4) is first used or the table 644 is used to calculate the provisional torque constant A may be changed according to settings or fixedly determined. There may be.

A method of calculating the torque constant using any of the equations (1) to (4) and the table 644 will be described below using a flowchart. FIG. 11 is a flow chart showing the processing procedure of the CPU 61 for calculating the torque constant with the disturbance observer 610 of the third embodiment. The process shown in FIG. 11 is executed by the CPU 61 as part of the process of estimating the disturbance force. The rotation speed in the figure is the rotation speed of the motor 23a calculated by the CPU 61 in the process shown in FIG. 7 of the first embodiment.

When the process of FIG. 11 is started, the CPU 61 acquires temperature information of the motor 23a from the temperature detector 23c (S41), and further acquires current information from the current detector 237 (S42). Here, the CPU 61 first determines whether or not to use any of the polynomials of equations (1) to (3) or the piecewise polynomial of equation (4) (S43). As described above, this determination may be omitted and the process may be fixedly moved to either step S44 or S51.

If the polynomial or piecewise polynomial is used first (S43: YES), the CPU 61 applies the temperature T indicated by the acquired temperature information to any of the polynomials of equations (1) to (3) or the piecewise polynomial of equation (4). Then, a provisional torque constant A is calculated (S44). Next, the CPU 61 reads out the contents stored in the table 644 corresponding to 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).

Further, the CPU 61 reads the provisional torque constant C from the table 644 when the current is 4 A and the rotation speed is 0 rpm (S47), and calculates the ratio D of the torque constant B to the torque constant C (S48). Then, the CPU 61 multiplies the provisional torque constant A by the ratio D to calculate the target torque constant (S49: corresponding to the constant calculation unit 611), and terminates the processing of FIG.

On the other hand, in step S43, if the polynomial or piecewise polynomial is not used first (S43: NO), the CPU 61 reads out the contents stored in the table 644 corresponding to the current indicated by the acquired current information and the rotational speed of the motor 23a. (S51), a temporary torque constant A is calculated by linear interpolation (S52). Next, the CPU 61 applies the temperature T indicated by the acquired temperature information to any of the polynomials of equations (1) to (3) or the piecewise polynomial of equation (4) to calculate a provisional torque constant B (S53 ). The CPU 61 further calculates a provisional torque constant C when the temperature T is 0° C. using the above polynomial or piecewise polynomial (S54), and shifts the process to step S48 to calculate a target torque constant.

In the third embodiment, among the torque constants stored in the tables 641, 642, and 643, the torque constant when the temperature is 0° C. is stored in the table 644, but it is limited to this. not a thing Similar results are obtained when the torque constants are stored in the table 644 for any of the temperatures of 10°C, 20°C, and 30°C.

As described above, according to the third embodiment, in addition to predetermining the above-described polynomial or piecewise polynomial, the correspondence between the current and rotation speed of the motor 23a and the torque constant of the motor 23a is actually measured in advance. It is stored in table 644 . When the torque constant is calculated during execution, 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 calculated based on the above polynomial or piecewise polynomial. Alternatively, the provisional torque constant A calculated by applying the detected temperature to the above polynomial or piecewise polynomial is corrected based on the contents stored in the table 644 . Therefore, the calculation accuracy of the torque constant is improved, and the calculation load can be reduced.

(simulation)
Below, the result of having modeled and simulated the temperature change of each part of the motor 23a is demonstrated. FIG. 12 is an explanatory diagram schematically showing a temperature model of the motor 23a. In the temperature model of FIG. 12, heat transfer occurs between the windings and the air inside the motor, between the windings and the outside air, between the air inside the motor and the magnet, and between the air inside the motor and the outside air. The amount of heat Qc [J] supplied to the winding can be expressed by the following equation (5) from the motor current Im [A] and the winding resistance Rc [Ω].

Qc=Rc×Im ² (5)

The amount of heat Qca transferred from the windings to the air in the motor can be expressed by the following equation (6) from the winding temperature Tc [°C], the air temperature Ta [°C] in the motor, and the thermal resistance Trca [sK/J]. Also, the amount of heat Qcat transferred from the windings to the outside air can be expressed by the following equation (7) from 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 amount of heat Qam transferred from the air in the motor to the magnet can be expressed by the following equation (8) from the air temperature Ta in the motor, the magnet temperature Tm, and the thermal resistance Tram. Also, the amount of heat Qaat transferred from the air inside the motor to the outside air can be expressed by the following equation (9) from the air temperature Ta inside the motor, the outside air temperature Tat, and the thermal resistance Traat.

Qam=(Ta/Tm)/Tram (8)
Qaat=(Ta−Tat)/Traat (9)

Assuming that the heat capacity of the winding is Hc [J/K], the heat capacity of the air inside the motor is Ha, and the heat capacity of the magnet is Hm, temperature changes ΔTc, ΔTa, and ΔTm per second of the winding, the air inside the motor, and the magnet are given by , 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)

A simulation was performed under the following conditions using equations (10) to (12) based on the above modeling.

Initial values of Tc, Ta, Tm, Tat: 20
Rc=0.1
Trca = Tram = 0.05
Traat=Trcat=0.1
Hc=2000, Ha=100, Hm=2000

FIG. 13 is a graph showing simulation results of temperature changes in each part of the motor 23a. The horizontal axis of the figure represents time (seconds), and the vertical axis represents temperature (°C). A solid line, a broken line, and a one-dot chain line in the figure indicate the magnet temperature Tm, the winding temperature Tc, and the motor internal air temperature Ta, respectively. Note that the motor current Im was set to 100 [A] from time 0 to 1500 seconds, and then set to 0.

According to the above simulation results, it can be seen that the motor internal air temperature Ta rises with a slight delay from the rise in the winding temperature Tc of the motor 23a, and the magnet temperature Tm rises with a slight delay. In addition, the winding temperature Tc asymptotically approaches 80° C. after 1500 seconds, and the motor internal air temperature Ta asymptotically approaches 60° C., which is lower than that. Since the magnet temperature Tm transfers heat only to the air inside the motor, it asymptotically approaches the same temperature as the air temperature Ta inside the motor. By executing the same calculation as this simulation in real time, the magnet temperature Tm can be obtained from the motor current Im and the outside air temperature Tat. The outside air temperature Tat may be directly measured by a temperature sensor, for example, the value of the temperature sensor of the encoder 23b of the motor 23a or the temperature sensor in the control panel may be used as an alternative value of the outside air temperature, or an approximate value may be obtained from these. It may be calculated and used as the outside air temperature.

The embodiments disclosed this time should be considered as examples in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the meaning described above, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. Also, the technical features described in the embodiments can be combined with each other.

10 Y-axis direction movement mechanism 13 Y-axis motor 20 X-axis direction movement mechanism 23 X-axis motor 23a Motor 23b Encoder 23c Temperature detector 230 Servo circuit 237 Current detector 30 Z-axis direction movement mechanism 33 Z-axis motor 51 Spindle 6 Spindle motor 60 control device 600 control section 610 disturbance observer 611 constant calculation section 612 torque calculation section 613 torque estimation section 61 CPU
62 ROMs
63 RAM
64 storage device 641, 642, 643, 644 table 66 input/output interface 67 reception unit 68 Z-axis sensor 69 spindle sensor 100 machine tool

Claims (7)

A disturbance observer that acquires position information and current information of the motor, which are fed back to a servo circuit that feedback-controls the motor based on a command, and estimates disturbance acting on the motor,
a constant calculation unit 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 that calculates the torque of the motor by multiplying the current indicated by the acquired current information by the torque constant calculated by the constant calculation unit;
a torque estimating unit that estimates the torque of the motor based on the position indicated by the acquired position information and the constant related to the load machine driven by the motor,
The disturbance is estimated by subtracting the torque estimated by the torque estimation unit from the torque calculated by the torque calculation unit,
The constant calculation unit approximates a torque constant using an n-th order (n is an integer of 1 or more) polynomial based on the relationship between the temperature and torque of the motor,
A plurality of the polynomials are determined by changing the temperature of the motor and the state of power running or regeneration,
The constant calculation unit detects whether the motor is in a power running state or a regenerative state, uses a polynomial corresponding to the detected state,
A disturbance observer, wherein the polynomial is any one of the following three equations.
Kt = a-bT
Kt = a - b (T - c) ²
Kt=a0+a1T+ ^a2T2 +...+ ^anTn
however,
Kt: torque constant T: temperature indicated by the temperature information a, b, c, a0, a1, a2, . . . an: constant constant or coefficient further comprising a table that stores a 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 content stored in the table corresponding to the rotation speed obtained by differentiating once the current indicated by the acquired current information and the position indicated by the acquired position information and the polynomial. 2. The disturbance observer of claim 1, wherein: the command is a position command and/or a speed command;
3. The disturbance observer according to claim 1, wherein the servo circuit controls current flowing through the motor. The torque estimator calculates the product of the rotational speed obtained by differentiating the position indicated by the acquired position information once and the viscous resistance of the load machine, the acceleration obtained by further differentiating the rotational speed once, and the moment of inertia of the load machine. 4. The disturbance observer according to any one of claims 1 to 3, wherein the torque is estimated based on the sum of the product of and the Coulomb frictional force according to the moving direction of the load machine. A control device comprising: the disturbance observer according to any one of claims 1 to 4; and a control unit that issues the command. A machine tool comprising the control device according to claim 5, the servo circuit, the motor, and the load machine,
a position detection unit that detects the position of the motor and feeds back position information indicating the detected position to the servo circuit;
a current detection unit that detects the current of the motor and feeds back current information indicating the detected current to the servo circuit;
a temperature detection unit that detects the temperature of the motor and generates temperature information indicating the detected temperature,
The machine tool, wherein the disturbance observer acquires temperature information from the temperature detection unit. A method of estimating a disturbance acting on the motor by acquiring position information and current information of the motor that are fed back to a servo circuit that feedback-controls the motor based on a command,
obtaining temperature information of the motor and calculating a torque constant of the motor based on the temperature indicated by the obtained temperature information;
calculating the torque of the motor by multiplying the calculated torque constant by the current indicated by the acquired current information;
estimating the torque of the motor based on the position indicated by the acquired position information and a constant related to the load machine driven by the motor;
and estimating the disturbance by subtracting the estimated torque from the calculated torque,
In the step of calculating the torque constant, approximating the torque constant using an n-th order (n is an integer of 1 or more) polynomial based on the relationship between the temperature and the torque of the motor,
A plurality of the polynomials are determined by changing the temperature of the motor and the state of power running or regeneration,
The step of calculating the torque constant of the motor detects whether the motor is in a power running state or in a regenerative state, and uses a polynomial expression corresponding to the detected state,
A disturbance estimation method, wherein the polynomial is any one of the following three equations.
Kt = a-bT
Kt = a - b (T - c) ²
Kt=a0+a1T+ ^a2T2 +...+ ^anTn
however,
Kt: torque constant T: temperature indicated by the temperature information a, b, c, a0, a1, a2, . . . an: constant constant or coefficient

Images