JP4843942B2 - Thrust ripple correction method and thrust ripple correction device - Google Patents

Description

The present invention relates to a thrust ripple correction method for correcting thrust ripple of a motor, a thrust ripple correction device, or a position control for controlling the position of a moving member in a mechanism including a motor and a load to which the thrust of the motor is applied. It relates mETHODS, particularly, by correcting the thrust of the motor, to a method and apparatus capable of accurately controlling the position of the moving member.

As an XY stage for positioning a two-dimensional position of an object, a grid platen having teeth formed at a constant pitch in the X-axis and Y-axis directions, and a slider unit levitated on the grid platen are provided. An XY stage is disclosed in which a slider portion is configured to be movable in a plane by attaching a motor and a Y-axis motor (see Patent Document 1 below).
JP 2000-65970 A

In the XY stage, teeth are formed on the X-axis motor and the Y-axis motor at a constant pitch in the X-axis and Y-axis directions, respectively, and between these teeth and the teeth formed on the lattice platen described above. By generating a magnetic force, thrust in the X-axis and Y-axis directions is generated, and the slider portion is driven in the XY plane.
As described above, in the XY stage, the stepping motor is configured by the teeth formed on the lattice platen and the slider portion. However, there is a variation in thrust based on the positional relationship between the teeth, that is, a thrust ripple. Therefore, if the thrust ripple can be corrected, the positioning accuracy of the XY stage can be further improved.

  An object of the present invention is to provide a thrust ripple correction method and the like that can suppress fluctuations in thrust caused by thrust ripple by correcting the thrust of the motor.

The thrust ripple correction method of the present invention is a thrust ripple correction method for correcting periodic thrust ripple in a stepping motor subjected to feedback control based on a difference between a command value and a detected value,
A first error component is acquired in a state where a periodic first temporary correction component having a fixed period is added to the control loop, and a period of the fixed period different from the first temporary correction component is added to the control loop. An error acquisition step of acquiring a second error component in a state in which a second temporary correction component is added;
A calculation step of calculating a periodic main correction component having a fixed period to be added to the control loop based on the first error component and the second error component acquired by the error acquisition step;
It is characterized by providing.

The second temporary correction component may be determined based on the first error component.

The main correction component may be a function of the commutation phase of the motor.

The first error component and the second error component may be position error components.

The first error component may be zero.

The difference may I difference der between the speed command value and the speed detection value.

In the error acquisition step, the first error component and the second error component are acquired at the time of acceleration / deceleration of the stepping motor, and the stepping at the time of acquiring the first error component and the second error component is acquired. The motor acceleration may be equal.

The thrust ripple correction device of the present invention is a thrust ripple correction device that corrects periodic thrust ripple of a stepping motor subjected to feedback control based on a difference between a command value and a detection value,
A first error component is acquired in a state where a periodic first temporary correction component having a fixed period is added to the control loop, and a period of the fixed period different from the first temporary correction component is added to the control loop. Error acquisition means for acquiring a second error component in a state in which a second temporary correction component is added;
Calculation means for calculating a periodic main correction component having a fixed period to be added to the control loop based on the first error component and the second error component acquired by the error acquisition means;
It is characterized by providing.

  According to the present invention, the main correction value for correcting the thrust ripple is calculated based on the error component at the time of correction by the first temporary correction value and the error component at the time of correction by the second temporary correction value. The error component due to the actual thrust ripple can be effectively reflected in the calculation of the main correction value, and the main correction value can be obtained with high accuracy.

  Further, according to the present invention, the main correction value for correcting the thrust of the motor is calculated based on the error component at the time of correction by the first temporary correction value and the error component at the time of correction by the second temporary correction value. Since the calculation is performed, the actual error component can be effectively reflected in the calculation of the main correction value, and the main correction value can be obtained with high accuracy.

  Hereinafter, an embodiment of a thrust ripple correction method according to the present invention will be described with reference to FIGS.

  FIG. 1 is a block diagram showing the configuration of a position control device to which the thrust ripple correction method of this embodiment is applied. This position control device is a device that controls the position of the moving element of the motor in accordance with the speed command Vin. FIG. 1 shows a component for controlling the motor while correcting the thrust ripple.

  As shown in FIG. 1, the position control device includes a motor 1 including a drive circuit, and a speed error amplifier 2 that amplifies a difference between a speed of a moving element of the motor 1 and a speed command Vin. The motor 1 is given a thrust generator 11 that generates thrust according to the output signal of the speed error amplifier 2, an adder 12 that adds a thrust ripple Fr to the thrust from the thrust generator 11, and a thrust output from the adder 12. It consists of a load 13. As shown in FIG. 1, the output value of the speed error amplifier 2 is corrected by a correction value Vc for canceling the thrust ripple Fr, and is given to the thrust generator 11. A method for canceling the thrust ripple Fr will be described later.

  The speed of the moving element is measured by the speed sensor 3 and given to the adder 5. From the adder 5, the difference between the speed of the moving element and the speed command Vin is output and supplied to the speed error amplifier 2. As described above, in the position control device of FIG. 1, the speed of the moving element is feedback-controlled.

  On the other hand, the position of the moving element is measured by the position sensor 6, and the measured value is output as the commutation phase θ of the motor 1. The commutation phase θ indicates the phase relationship between the positions of the stator and the mover, and corresponds to the relative phase between the stator and the mover teeth in the stepping motor. The value of the thrust ripple Fr is substantially a function of the commutation phase θ.

  In the storage unit 7 of the position control device, Sin (kθ) tables 71a, 71b,... In which kθ and Sin (kθ) values are associated, and Cos ( kθ) tables 72a, 72b,... are stored. “K” is a positive number from 1 to n and is set according to the accuracy required for ripple correction. “K” is, for example, 1 to 5, but the value of “n” increases if high accuracy is required.

  The storage unit 8 of the position control device stores a constant Pk (constants P1, P2,...) And a constant Qk (constants Q1, Q2,...).

  As shown in FIG. 1, when the motor 1 is driven, the Sin (kθ) tables 71a, 71b,... And the Cos (kθ) tables 72a, 72b,. Corresponding values of Sin (kθ) and Cos (kθ) are read out. The read Sin (kθ) and Cos (kθ) are multiplied by constants Pk and Qk in multipliers 91a, 91b,... And multipliers 91a, 91b,.

  These multiplication values are added to each other by adders 21 to 23 and the like. The added value is further multiplied by an error ΔF, which is an output value of the speed error amplifier, in the multiplier 24 to calculate a correction value Vc. The correction value Vc is added to the error ΔF that is the output value of the speed error amplifier 2 in the adder 25, and the added value is given to the thrust generator 11.

  The correction value Vc output in the above procedure is a value applied to the thrust generator 11 in order to correct the thrust ripple Fr of the motor 1. Based on the periodicity of the thrust ripple Fr (the thrust ripple Fr is substantially a function of the commutation phase θ), the correction value Vc is a Fourier series (P1 · Sin (θ) + P2 · Sin (2θ) +. + Q1 · Cos (θ) + Q2 · Cos (2θ) +... The correction value Vc is determined based on a constant Pk and a constant Qk that are coefficients of each term.

  Next, a method for calculating the constant Pk and the constant Qk for determining the correction value in the thrust ripple correction method of the present embodiment will be described. This correction value is a correction value Vc that is finally used to cancel the thrust ripple Fr.

  FIG. 2 is a block diagram showing components for calculating the constant Pk and the constant Qk in the position control device to which the thrust ripple correction method of this embodiment is applied.

  As shown in FIG. 2, the dθ detector 31 detects that θ has changed by dθ based on the commutation phase θ output from the position sensor 6. The multipliers 32a, 32b,... Add dθ and the error ΔF output from the speed error amplifier 2 to the value of Sin (kθ) read from the Sin (kθ) tables 71a, 71b,. Multiply sequentially. Further, the multipliers 33a, 33b,... Sequentially multiply the value of Cos (kθ) read from the Cos (kθ) tables 72a, 72b,.

  The integrators 34a, 34b,... Integrate the multiplication values output from the multipliers 32a, 32b,. The integrators 35a, 35b,... Integrate the multiplication values output from the multipliers 33a, 33b,.

  The above operation is executed while driving the motor 1 based on the speed command Vin. By such an operation, a value obtained by integrating the product of ΔF and Sin (kθ) with respect to θ and a value obtained by integrating the product of ΔF and Cos (kθ) with respect to θ are calculated. For example, the integrator 34a obtains a value obtained by integrating the product of ΔF and Sin (θ) with respect to θ. Similarly, the integrator 34b obtains a value obtained by integrating the product of ΔF and Sin (2θ) with respect to θ. Further, the integrator 35a obtains a value obtained by integrating the product of ΔF and Cos (θ) with respect to θ. Similarly, in the integrator 35b, a value obtained by integrating the product of ΔF and Cos (2θ) with respect to θ is obtained.

  As described above, in each of the accumulators 34a, 34b,... And the accumulators 35a, 35b,..., The coefficient of each term when ΔF is expanded by Fourier series is obtained.

  On the other hand, the integrator 41 of FIG. 2 integrates the absolute value of ΔF during the above operation. After the above operation is finished, the dividers 36a, 36b,... Divide the integrated value obtained by the integrators 34a, 34b,. Further, the dividers 37a, 37b,... Divide the integrated value obtained by the integrators 35a, 35b,... By the output value (integrated value) of the integrator 41. By these processes, the constant Pk and the constant Qk in which the integral value is normalized by the magnitude of the error ΔF during the operation can be obtained.

  FIG. 3 is a block diagram functionally showing a procedure for calculating the correction value in the thrust ripple correction method of the present embodiment.

  In FIG. 3, the first error acquisition unit 101 acquires an error component at the time of correction using the first temporary correction value. The second error acquisition unit 102 acquires an error component at the time of correction using the second temporary correction value. The correction value calculation unit 103 corrects the thrust of the motor based on the acquired error component at the time of correction using the first temporary correction value and the error component at the time of correction using the second temporary correction value. This correction value is calculated.

  FIG. 4 is a control block diagram showing a configuration for executing control of the position control device, and FIG. 5 is a flowchart showing a procedure for calculating the correction value.

  As shown in FIG. 4, the control unit 51 controls a calculation unit 52 for performing calculations necessary for position control and correction value calculation.

  The arithmetic unit 52 constitutes each element of FIG. 1 and FIG. 3 having an arithmetic function (speed error amplifier 2, adder group, multiplier group, integrator group, divider group, dθ detector 31 and the like). . In addition, the calculation unit 52 executes a calculation process necessary for calculating the correction value.

  Further, the control unit 51 stores the speed sensor 3, the position sensor 6, the Sin (kθ) tables 71a, 71b,... And the Cos (kθ) tables 72a, 72b,. A storage unit 7 and a storage unit 8 for storing constants Pk and Qk are connected. Further, the speed command Vin is input to the control unit 51, and the drive circuit 55 provided in the motor 1 is controlled by the control unit 51.

  FIG. 6 is a diagram illustrating changes in the speed and thrust of the motor 1 when the correction value is calculated. As shown in FIG. 6, this correction value can be calculated while accelerating the motor 1. In the example of FIG. 6, the first to third steps described later are sequentially executed while continuing the acceleration of the motor 1. A series of processes to be described later may be executed while the motor 1 is decelerated.

  Hereinafter, the procedure for calculating the correction value will be described with reference to the flowchart of FIG. The procedure shown in FIG. 5 is executed using the configuration shown in FIG. 2 based on the control of the control unit 51 shown in FIG.

  In step S1 to step S6 of FIG. 5, a first stage process is performed. This process corresponds to the function of the first error acquisition unit 101 (FIG. 3).

  In step S1 of FIG. 5, it is determined whether or not the motor 1 is accelerating or decelerating, and the process proceeds to step S2 after the determination is affirmed. In step S2, the values of the constant Pk and the constant Qk are all set to zero. As a result, the thrust ripple Fr is not corrected, that is, the correction value Vc is zero. This correction value Vc (zero) corresponds to the first temporary correction value.

  Next, in step S3, each time the dθ detector 31 detects that the commutation phase θ has changed by dθ while accelerating or decelerating the motor 1, the multipliers 32a, 32b,. , 33b,... Are sequentially executed. Moreover, these multiplication values are integrated by integrators 34a, 34b,... And integrators 35a, 35b,. As a result, ΔF is expanded into a Fourier series, and the coefficient of each term is calculated. Further, the absolute value of ΔF is integrated by the integrator 41.

  Next, in step S4, it is determined whether or not the mover has moved by a predetermined position change. Here, it is determined whether or not the commutation phase θ has periodically changed a predetermined number of times (for example, 1 to 4 times). If the motor 1 is a stepping motor, it is determined whether or not the mover has moved a distance that is a predetermined multiple (for example, 1 to 4 times) the pitch cycle of the mover teeth. If the determination is negative, step S3 is repeated, and if the determination is affirmative, the process proceeds to step S5. Thus, the above process is repeated each time the commutation phase θ changes by dθ in step S3 while the moving element moves by a predetermined position change.

  Next, in step S5, error component harmonic analysis is executed in the region R of FIG. In this processing, the dividers 36a, 36b,... Divide the integrated values obtained by the integrators 34a, 34b,. Further, the dividers 37a, 37b,... Divide the integrated values obtained by the integrators 35a, 35b,.

  Next, in step S6, a constant Pk and a constant Qk are obtained based on the process in step S5. This value is defined as a constant P0k and a constant Q0k.

  In step S12 to step S16 in FIG. 5, a second stage process is performed. This processing corresponds to the function of the second error acquisition unit 102 (FIG. 3).

  In step S12, the values of the constant Pk and the constant Qk are set to the values obtained in the first stage processing, that is, the constant P0k and the constant Q0k. As a result, the thrust ripple Fr is corrected by the correction value Vc defined by the constant P0k and the constant Q0k acquired in the first stage process. This correction value Vc corresponds to a second temporary correction value.

  Next, in step S13, as in step S3, each time the dθ detector 31 detects that the commutation phase θ has changed by dθ, the multipliers 32a, 32b,... And the multipliers 33a, 33b,. The multiplication by... Is sequentially executed. Moreover, these multiplication values are integrated by integrators 34a, 34b,... And integrators 35a, 35b,. As a result, ΔF is expanded into a Fourier series, and the coefficient of each term is calculated. Further, the absolute value of ΔF is integrated by the integrator 41.

  Next, in step S14, it is determined whether the mover has moved by a predetermined position change. Here, as in step S4, it is determined whether or not the commutation phase θ has periodically changed a predetermined number of times (for example, 1 to 4 times). If the determination is negative, step S13 is repeated, and if the determination is affirmative, the process proceeds to step S15. As a result, the above process is repeated each time the commutation phase θ changes by dθ in step S13 while the moving element moves by a predetermined position change.

  Next, in step S15, error component harmonic analysis is executed in the region R of FIG. Here, processing similar to that in step S5 is executed, and new constants Pk and Qk are obtained. This value is defined as a constant P1k and a constant Q1k.

  Next, in step S16, a constant P2k and a constant Q2k that define this correction value are calculated based on the constants P0k and Q0k acquired in the first stage and the constants P1k and Q1k acquired in the second stage. To do. In step S16, a constant P2k and a constant Q2k are calculated by vector calculation. The constants P0k and Q0k represent the position error components of the mover in the first stage, and the constants P1k and Q1k represent the position error components of the mover in the second stage. Therefore, the process of step S16 is equivalent to the process of calculating the main correction value based on the position error component in the first stage and the position error component in the second stage, and the main correction value calculation means 103 (FIG. 3). ) Function.

  In step S22 to step S25 in FIG. 5, a third stage process is performed. In this process, the validity of the calculated correction value is verified.

  In step S22 of FIG. 5, the values of the constant Pk and the constant Qk are set to the values obtained in the process of step S16, that is, the constant P2k and the constant Q2k. Thus, the thrust ripple Fr is corrected by the correction value Vc defined by the constant P2k and the constant Q2k. This correction value Vc becomes the main correction value.

  Next, in step S23, as in step S3, each time the dθ detector 31 detects that the commutation phase θ has changed by dθ, the multipliers 32a, 32b,... And the multipliers 33a, 33b,. The multiplication by... Is sequentially executed. Moreover, these multiplication values are integrated by integrators 34a, 34b,... And integrators 35a, 35b,. As a result, ΔF is expanded into a Fourier series, and the coefficient of each term is calculated. Further, the absolute value of ΔF is integrated by the integrator 41.

  Next, in step S24, it is determined whether or not the mover has moved by a predetermined position change. Here, as in step S4, it is determined whether or not the commutation phase θ has periodically changed a predetermined number of times (for example, 1 to 4 times). If the determination is negative, step S23 is repeated, and if the determination is affirmative, the process proceeds to step S25. Thus, the above process is repeated each time the commutation phase θ changes by dθ in step S23 while the moving element moves by a predetermined position change.

  Next, in step S25, error component harmonic analysis is executed in the region R of FIG. Here, the same processing as in step S5 is executed to obtain the constant Pk and the constant Qk. In step S25, based on the calculated constant Pk and constant Qk, it is determined whether or not the thrust ripple Fr is effectively corrected by this correction value. If the determination is positive, the process proceeds to step S31. If the determination is negative, the process returns to step S1, and the correction value calculation process is executed again by repeating a series of processes. In step S31, it is determined whether or not the speed of the moving element is constant, and the series of processing is terminated after the determination is affirmed.

  In the position control device, the thrust ripple Fr can be effectively corrected from the operation immediately after the power is turned on by using the constant P2k and the constant Q2k calculated by the series of processes shown in FIG. 5 as initial values. In addition, by appropriately executing the calculation of the correction value, it is possible to cope with a change with time of the position control device and a change in use environment.

  Further, in the above-described embodiment, an error component due to thrust ripple when the motor 1 is accelerated or decelerated is taken in. In general, thrust ripple causes a large error during acceleration or deceleration. For this reason, according to this embodiment, it becomes possible to cancel the thrust ripple at the time of acceleration / deceleration effectively, and an error can be suppressed effectively.

  In the above process, as shown in FIG. 6, the first to third stage processes are executed while continuously increasing the speed of the motor 1. However, when the motor stroke is short and the acceleration / deceleration time necessary for calculating the constant Pk and the constant Qk cannot be obtained, or when the generated error is speed-dependent, the first to third stages. The acceleration / deceleration time may be secured independently for each of the processes. FIG. 7 shows such a method, in which acceleration time is ensured for each process of the first to third stages, and the motor is reversely rotated between the stages to return to the origin. According to the example of FIG. 7, since the error is acquired in a wide range of the motor speed, the error can be effectively corrected even when the error is highly dependent on the speed. In addition, the correction accuracy can be improved by performing the first to third stage processes under the same conditions.

  In the above embodiment, the correction value Vc is determined by the constant Pk and the constant Qk. However, instead of the constant, a variable that changes in accordance with the position, speed, acceleration, etc. of the slider may be used. In this case, even when the fluctuation of the thrust of the motor changes depending on the position, speed, etc., correction with high accuracy is possible.

  The scope of application of the present invention is not limited to the above embodiment. The present invention can be widely applied to cases where errors are suppressed by correcting the thrust of the motor.

The block diagram which shows the structure of the position control apparatus to which the thrust ripple correction method of this embodiment is applied. The block diagram which shows the component part of the position control apparatus for calculating the constant Pk and the constant Qk. The block diagram which shows the procedure which calculates this correction value functionally. The control block diagram which shows the structure for performing control of a position control apparatus. The flowchart which shows the procedure which calculates this correction value. The figure which shows the change of the speed and thrust of a motor at the time of calculating this correction value. The figure which shows the change of the speed and thrust of a motor at the time of calculating this correction value.

Explanation of symbols

51 Control Unit 52 Calculation Unit 101 First Error Acquisition Unit 102 Second Error Acquisition Unit 103 Main Correction Value Calculation Unit

Claims (8)

A thrust ripple correction method for correcting a periodic thrust ripple in a stepping motor subjected to feedback control based on a difference between a command value and a detected value,
A first error component is acquired in a state where a periodic first temporary correction component having a fixed period is added to the control loop, and a period of the fixed period different from the first temporary correction component is added to the control loop. An error acquisition step of acquiring a second error component in a state in which a second temporary correction component is added;
A calculation step of calculating a periodic main correction component having a fixed period to be added to the control loop based on the first error component and the second error component acquired by the error acquisition step;
A thrust ripple correction method comprising: The thrust ripple correction method according to claim 1, wherein the second temporary correction component is determined based on the first error component. 3. The thrust ripple correction method according to claim 1, wherein the main correction component is a function of a commutation phase of the motor. The thrust ripple correction method according to claim 1, wherein the first error component and the second error component are position error components. The thrust ripple correction method according to any one of claims 1 to 4, wherein the first error component is zero. The thrust ripple correction method according to claim 1, wherein the difference is a difference between a speed command value and a speed detection value. In the error acquisition step, the first error component and the second error component are acquired at the time of acceleration / deceleration of the stepping motor, and the stepping at the time of acquiring the first error component and the second error component is acquired. The thrust ripple correction method according to any one of claims 1 to 6, wherein the motors have the same acceleration . A thrust ripple correction device that corrects periodic thrust ripple of a stepping motor subjected to feedback control based on a difference between a command value and a detected value,
A first error component is acquired in a state where a periodic first temporary correction component having a fixed period is added to the control loop, and a period of the fixed period different from the first temporary correction component is added to the control loop. Error acquisition means for acquiring a second error component in a state in which a second temporary correction component is added;
Calculation means for calculating a periodic main correction component having a fixed period to be added to the control loop based on the first error component and the second error component acquired by the error acquisition means;
A thrust ripple correction device comprising:

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