JP3402870B2 - Multi-phase linear motor drive - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-phase linear motor driving device for a multi-phase linear motor, and is particularly used in a field where highly accurate speed control or position control is required. .

[0002]

2. Description of the Related Art FIG. 7 shows an example of the structure of a polyphase linear motor having a plurality of coils. In the figure, reference numeral 12 is a linear motor coil (stator), and for convenience sake No. The numbers from 1 to No. 4 are attached. Again 13
Is a movable magnet (movable element), and is arranged such that the polarities of adjacent and facing magnets are different.

The position of the mover 13 is detected by a Hall element or the like arranged in the coil 12, and the polarity (N, S pole) of the mover 13 is detected to determine the predetermined coil 12
Is energized. This selection method is also shown in FIG. here,

[0004]

[Outer 1] The mark indicates the coil 1 to be energized according to the position of the mover 13.
2 shows the direction of the electric current to be passed through. A circuit configuration for driving a multi-phase linear motor having a configuration as shown in FIG. 7 is disclosed in Japanese Patent Laid-Open No. 1-298410.

In the multi-phase linear motor as shown in FIG. 7, the thrusts generated in the respective coil 12 portions are not necessarily the same. Also, the adjacent coil 12 and coil 1
It is general to dispose a space to some extent between the two. Due to the gap between the coils, the thrust force also varies depending on the position of the mover 13, and the thrust force distribution is normally as shown in FIG. Therefore, for example, when the constant speed control of the mover 13 is performed, it is impossible to sufficiently reduce the control deviation due to the influence of the thrust variation.

Therefore, as a means for solving this problem, it has been proposed to previously create a coefficient sequence having a fluctuation characteristic that is exactly opposite to the thrust fluctuation (Japanese Patent Application No. 5-305303). . First, the mover 13 is moved in a predetermined direction at a sufficiently low speed in advance, and the mover 13 is moved.
If the relationship between the position of and the value of the current flowing through the linear motor coil is sequentially stored and proper normalization is performed, this becomes a reference table. Then, when the polyphase linear motor is driven, the table is referred to according to the position of the mover 13 and the operation amount to the polyphase linear motor is weighted, thereby suppressing an increase in control deviation due to thrust variation.

[0007]

However, in the created table, the load fluctuation due to friction and the mover 1 are
Since the center of gravity moves due to the movement of 3 and the inclination of the entire structure including the polyphase linear motor is generated, a gentle trend tends to be included in addition to the thrust variation of the motor. Therefore, the operation amount of the polyphase linear motor is weighted more than necessary, and the control characteristics of the system may significantly change. That is, there is a problem that the open loop gain of the system fluctuates greatly, the control deviation cannot be suppressed, and the stability of the system deteriorates and large steady vibration remains.

In view of the above problems of the prior art, an object of the present invention is to eliminate the influence of load fluctuation and the like at the time of creating the table and obtain a thrust correction table for compensating only the pure thrust fluctuation of the motor. It is an object of the present invention to provide a driving device for a multi-phase linear motor that is capable of achieving the above, and that is stable and can sufficiently reduce the control deviation.

[0009]

A driving apparatus for a multi-phase linear motor according to the present invention comprises a reference table holding information on thrust change at each point in the driving direction of the multi-phase linear motor, and the reference table is provided during driving. It is characterized in that it is driven while sequentially referring to. Here, the "thrust change" means removal of a trend caused by a load change due to friction or the like, or an inclination of the entire structure including the polyphase linear motor when the center of gravity moves as the mover 13 moves. It is the amount of thrust fluctuation of the motor itself.

Further, in the driving apparatus for a multi-phase linear motor according to the present invention, the reference table is created based on the time series of the state quantities of the system obtained when the multi-phase linear motor is driven at a substantially constant speed prior to the table reference. It is characterized by doing.

The multi-phase linear motor drive apparatus according to the present invention uses a reference table which is normalized by using a coefficient sequence regressed or interpolated by a rational function having at least one degree. Characterize.

In the above-mentioned drive device for a multi-phase linear motor, the reference table is, for example, the linear motor or
Interrupts the time series of state quantities of the system driven by this in the high range.
It is created based on the results of the pre-processed by the cross-sectional linear topological digital filter. In this case , the linear phase digital
Cut-off frequency of the barrel filter is set higher than the frequency represented by the ratio of the coil pitch length of said constant speed value and a multi-phase linear motor.

[0013]

According to this, the linear motor is referred to while sequentially referring to the reference table which stores the information on the thrust change at each position in the driving direction of the linear motor, that is, the information on the thrust change in which the influence of the load fluctuation is eliminated. to drive, a linear motor can be driven to compensate only the thrust force variation of it themselves, whereby stable and controlled deviation is sufficiently reduced driving control is performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the configuration of a linear motor driving device according to an embodiment of the present invention. In the figure, 1
Is a reference table creation means, 2 is a table reference means, 3 is a reference table storage means, 4 is a control calculation means, and 5 is a target position generation means. The reference table creation means 1, the table reference means 2, the control calculation means 4 and the target position generation means 5 are realized by a microprocessor 6 such as a CPU or DSP. D / A converter 7
Receives a command value from the microprocessor 6, converts it into an analog signal, and supplies it to the amplifier 8. A current control loop is formed in the amplifier 8 and thus the amplifier 8 operates as a current mode amplifier. The amplifier 8 drives the multi-phase linear motor 9, and the position detector 10 detects the position of the mover. The multi-phase linear motor 9 has the same structure as that of FIG. 7 described in the related art. In this embodiment, the laser interferometer is used as the position detector 10, but a linear encoder or the like may be used instead.

The control calculation means 4 uses the position information from the position detector 10 to perform a control compensation calculation such as PID and then gives it to the D / A converter 7 as a current command value. It constitutes a feedback loop to be performed.

FIG. 2 is a flowchart showing the operation of the reference table creating means 1. This operation will be described in accordance with FIG. 2 and with reference to FIGS. 1 and 7.

First, according to the target value generated by the target position generating means 5, the movable element 13 of the polyphase linear motor is moved to the first position.
It is moved at a constant speed to the position (step S1). Next, the mover 13 is driven to a second position at a constant speed (steps S2 and S3). At this time, the microprocessor 6 sequentially stores the position P _{n of the} mover 13 and the output value to the D / A converter 8, that is, the current target value C _n in the memory 3 at a constant cycle (step S2). When the movement to the second position is completed, the saving operation in the memory 3 is finished.

The position and the current target value C _n stored in the memory 3 generally include high frequency components represented by external noise. On the other hand, for the thrust force fluctuation correction of the polyphase linear motor, which is the object of the present invention, since the frequency of the fluctuation component is sufficiently low, the digital filter method is applied to sufficiently remove the noise component. Is possible. In this embodiment, a linear phase filter is used as the above filter. As an example, the coil pitch for one phase of the multi-phase linear motor is 20 mm, and the moving speed from the first position to the second position is 10 mm / sec. Then, the thrust fluctuation frequency of the polyphase linear motor is 10/20
= 0.5 Hz, the cutoff frequency of the digital filter is higher than this, and a value capable of sufficiently removing high frequency components may be used. In this embodiment, 5 expressed by the equation 1
The cut-off frequency is set to 10 by using the 0th-order FIR filter.
It is set to Hz.

[0019]

[Equation 1] Here, y is the output of the filter, x is the input time series of the filter, f is the coefficient of the filter, and n is the time. In this way, for the position P _n and the current target value C _n stored in the memory 3, the filtered position time series PF _n and the current target value time series CF _n are respectively obtained (steps S4 to S4). S6).

When a polyphase linear motor is driven at a constant speed, the current target value C _n or CF _n equivalent to the thrust generated by the motor should be a time series centered on 0. Is. However, in actuality, due to the influence of the load and its fluctuation due to friction, etc., and the inclination of the entire structure including the polyphase linear motor caused by the movement of the center of gravity due to the movement of the mover, there is a gentle trend as shown in FIG. Will be included.

In order to remove this and obtain a time series that purely represents the thrust fluctuation of the polyphase linear motor, in the present embodiment, the coefficients a, b, and c expressed by the equation 2 are obtained (step S
7) Perform normalization processing. Symbols a, b, and c respectively represent the coefficients of the quadratic function, the quadratic function, and the constant term of the quadratic function, and are used to obtain the quadratic regression function based on the least squares method according to the equation (2). Regressing and normalizing with such a rational function is one of the features of the present invention.

[0022]

[Equation 2] In the equation (2), t is time, N is the number of time series to be regressed, and v is the current target value time series coefficient CF _n subjected to the filtering process. The normalization process is
Using the obtained regression function, the equation 3 is used (steps S8 to S10).

[0023]

[Equation 3] In Expression 3, α _n represents a time series of the normalized current target value. According to Equation 3, the time series of the current target value is normalized so as to have a value centered on 1, and becomes the one shown in FIG.

Next, the relationship between the position of the mover 13 of the polyphase linear motor and the current target value is created as a table (steps S11 to S13). The filtered time series PF _n is checked one by one in order, and each time it increases by one unit, the value of the current target value time series α _n that has been filtered and normalized is extracted and referred to. It is a table value. Here, 1 unit δ represents the fineness (pitch) of the reference table, and is 0.1 m in this embodiment.
Although it is set to m, it may be set to be sufficiently small within the range allowed by the memory capacity.

Here, the effect of using the linear phase filter in the filtering process appears. In the linear phase filter, a result having a constant phase delay with respect to the time series before filtering is always obtained as the time series after filtering. Therefore, the position time series PF _n and the current target value time series CF _n
Since the temporal relationship between the _values and α _n is completely preserved, the reference table K _m indicating the relationship between the position and the current target value can be created by the above-described simple process. The individual values of the normalized look-up table will be referred to herein as thrust correction factors.

Reference table K obtained by the processing up to this point
_m is stored in the memory 3 and is sequentially referred to by the table reference means 2. Next, the table reference means 2 will be described. When actually driving the multi-phase linear motor to perform operations such as speed control and positioning, the position detecting means 11
The thrust correction coefficient value k at that location is obtained by referring to the table based on the position information p obtained from the above and according to the rule expressed by the equation (4).

[0027]

[Equation 4] That is, by converting the position information p obtained by the position detecting means 11 into an integer multiple of the pitch of the table and using this as an offset (index) from the head of the in-memory reference table, the thrust correction coefficient k for the current position is obtained. Will be done.

The thrust correction coefficient k thus obtained is used in such a manner that it is multiplied by a value obtained as a result of performing a compensation calculation such as PID by the control calculation means 4, and the value after multiplication is used as a manipulated variable, that is, a control input D /. It is input to the A converter 7 to drive the polyphase linear motor.

In order to show the effect of this embodiment, FIGS. 5 and 6 show a comparison of the positional deviation in the steady state when the system shown in FIG. 1 is driven at a constant speed. Figure 5
FIG. 6 shows the case where the thrust correction of the present embodiment is not performed, and FIG. 6 shows the case where the thrust correction of the present embodiment is performed. In the case of the present embodiment, a sufficient thrust correction effect is obtained. Can be confirmed. Further, it can be seen that by the method of the present invention in which the trend shown in FIG. 3 is removed by normalization using a regression function, stable control performance is obtained without affecting the dynamic characteristics of the system.

In the above description, the reference table storage means 3
Although a memory is used as the above, it is also possible to store it in a medium such as a magnetic disk. In this case, once the reference table is created, it is not necessary to repeat the reference table creation unless the mechanical system characteristics change. Therefore, the reference table is read only once from the medium in which the reference table is stored when the device is started up. You can make it. Further, it is possible to correct the secular change of the mechanical system by automatically recreating the reference table after driving the polyphase linear motor for a certain long period.

Further, in the above, the table is normalized by regressing into a quadratic function, but any arbitrary rational function of linear or higher order can be used. Therefore, it is possible to perform normalization on the basis of the regression by the quartic function or the interpolation by the spline function, but since it is obvious, detailed description will be omitted.

[0032]

As described above, according to the present invention, the multi-phase linear motor is driven by sequentially referring to the reference table that stores the information of the thrust change at each position in the driving direction of the multi-phase linear motor. Therefore, in a system using a polyphase linear motor, it is possible to provide a drive device for a polyphase linear motor that can sufficiently eliminate thrust fluctuations of the polyphase linear motor and that can obtain stable dynamic characteristics.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a linear motor driving device according to an embodiment of the present invention.

FIG. 2 is a flow chart showing the operation of a reference table creating means in the apparatus of FIG.

FIG. 3 is a diagram showing a thrust waveform including a trend.

4 is a diagram showing a normalized thrust force waveform of the device of FIG.

FIG. 5 is a diagram showing a thrust waveform when the present invention is not applied.

FIG. 6 is a diagram showing a thrust waveform when the present invention is applied.

FIG. 7 is a diagram illustrating a configuration of a polyphase linear motor having a plurality of coils in a conventional example.

FIG. 8 is a diagram showing a thrust distribution of a conventional example.

[Explanation of symbols]

1: reference table creation means, 2: table reference means,
3: memory, 4: control calculation means, 5: target position generation means, 6: microprocessor, 7: amplifier, 8: amplifier, 9: polyphase linear motor, 10: position detector, 12:
Stator, 13: mover.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60L 13/03 B65G 54/02 H01L 21/68 H02P 7/00 H02P 5/00

Claims (2)

(57) [Claims] 1. A reference table in the driving apparatus using a multi-phase linear motor for selectively switching the coil to be energized according to the position of the movable element, which stores information of the thrust variation at each position before Symbol mover When, and a table referring means for sequentially referring to the reference table at the time of driving, the reference table
Prior to looking up the table,
The linear motor obtained when driven at a constant speed or
This reduces the time series of state quantities of the system driven by
Regression or interpolation with a rational function with an order of 1 or more
A multi-phase linear motor drive device characterized by being subjected to normalization processing using the above-mentioned coefficient sequence . 2. The reference table is created based on a result of preprocessing a time series of state quantities of the linear motor or a system driven by the linear motor by a high frequency cutoff linear phase digital filter, and the linear phase cutoff frequency of the digital filter is a multi-phase linear according to claim 1, characterized in that to be set higher than the frequency represented by the ratio of the coil pitch length of said constant speed value and a multi-phase linear motor Motor drive device.