JP3387715B2 - Polyphase linear motor controller - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates generally relates to a control apparatus for a multi-phase linear motor, is intended to be utilized in the fields requiring particularly precise speed control or position control.

[0002]

2. Description of the Related Art FIG. 5 shows an example of the structure of a polyphase linear motor having a plurality of coils. In FIG. 5, reference numeral 12 is a linear motor coil (stator), which is N for convenience.
o. 1-No. Numbers up to 4 are attached. Reference numeral 13 denotes a movable magnet (movable element), which 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, and the polarity (N,
A predetermined coil is energized by detecting the (S pole). The method of selecting the energizing coil is also shown in FIG. Where the sign

[0004]

[Outer 1] and

[0005]

[Outside 2] Indicates the direction of current flowing through the coil. The circuit configuration for driving the multi-phase linear motor having the configuration shown in FIG. 5 is disclosed in Japanese Patent Laid-Open No. 1-298410.

[0006]

In the polyphase linear motor as shown in FIG. 5, the thrusts generated in the respective coil portions are not necessarily the same. Further, it is general that the coils are arranged with a certain distance therebetween.
Due to the gap between the coils, the thrust varies depending on the location of the mover, and the thrust distribution is usually as shown in FIG. Therefore, for example, when performing a constant speed control of the mover, it is impossible to sufficiently reduce the control deviation due to the influence of such thrust variation.

Further, as the speed of the mover is increased, the frequency of the thrust fluctuation shown in FIG. 6 also increases, so that the influence of the thrust fluctuation is more likely to occur. This can be explained using the block diagram of FIG. 7 in which the motor is approximated by an integrator. FIG. 7 shows a speed control system of a motor that constitutes a speed feedback loop, and is provided with a PI (proportional + integral) compensator for simplicity. Further, K _t represents a torque constant, and M represents the mass of the movable part.

From FIG. 7, the transfer function from the thrust disturbance T to the velocity V (disturbance suppression characteristic) is given by the equation (1), and shows a differential characteristic in the low range.

[0009]

[Equation 1] Therefore, as the speed of the mover is increased, the influence of thrust disturbance is more likely to occur. Similarly, the smaller the mass of the movable part (load) is, the larger the gain of the equation (1) is, and as a result, the disturbance suppression capability is deteriorated. Conversely, the larger the mass, the less likely it is to be affected by the disturbance caused by the thrust fluctuation, and this is well known as the so-called "flywheel effect".

Further, as can be read from the equation (1), in order to enhance the thrust disturbance suppression capability, the control band may be expanded by increasing the gain of the PI compensator. However, in this case, the resonance point of the mechanical system generated by the connection state of the load may be excited, and thus the expected control band is not always obtained.

The present invention has been made to solve the above problems, and even when the gain of the compensator cannot be made sufficiently high due to the existence of a resonance point, etc., the control deviation caused by the fluctuation of the thrust force of the motor or the like. The present invention provides a control device for a polyphase linear motor that can sufficiently suppress the above.

[0012]

A control device for a multi-phase linear motor according to the present invention is arranged according to the position of a mover.
Multi-phase linear mode that selectively switches the coil to be energized
Equipped with a servo loop for negative feedback of position or speed
The moving direction of the mover
Have a reference table for holding correction information of the control deviation as the difference between the target position and the current position, the linear motor control during <br/> is obtained, et al with reference to the correction information of the reference table sequentially
The values and controls while adding to the control deviation. As a result, control is performed in which the control deviation portion resulting from thrust fluctuation or the like is compensated in advance and the occurrence of control deviation due to thrust fluctuation or the like is sufficiently suppressed.

Further, the control device for a multi-phase linear motor according to the present invention uses a reference table based on the time series of the state quantity of the system, that is, the position of the mover and the control deviation obtained when the multi-phase linear motor is driven prior to the table reference. It is characterized by creating.

Further, in the control apparatus for a multi-phase linear motor according to the present invention, the time series of the state quantity of the system obtained when the multi-phase linear motor is driven prior to the table reference is preprocessed by the linear phase digital filter. The reference table is created based on the result, and the cutoff frequency of the filter is set lower than the servo loop band. As a result, a table is created in which high-frequency components caused by external noise or the like are excluded, and stable control is performed based on the table.

Further, in the control device for a polyphase linear motor according to the present invention, the result of further driving the linear motor using the reference table prepared by the above method
It is characterized in that a coefficient sequence for correcting the reference table is generated and the reference table is sequentially corrected. As a result, the effect of suppressing the control deviation is further enhanced.

[0016]

【Example】

First Embodiment FIG. 1 shows the configuration of a polyphase linear motor controller according to the first embodiment of the present invention. In FIG. 1, reference numeral 1 is a reference table creating means, 2 is a table referring means, 3 is a memory as a reference table storing means, 4 is a control calculating means, and 5 is a target position generating means. Reference table creation means 1, table reference means 2, control calculation means 4, and target position generation means 5
Are realized by a microprocessor 6 such as a CPU or a DSP. The D / A converter 7 receives the 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 multi-phase linear motor 9 is driven by the amplifier 8, and its position is detected by the position detector 10. The multi-phase linear motor 9 has the same structure as that shown in FIG. Although a laser interferometer is used as the position detector 10 in this embodiment, a linear encoder or the like may be used instead.

In the control calculation means 4, the position information from the position detector 10 is used to perform a control compensation calculation such as PID, and then the result is given to the D / A converter 7 as a current command value. A feedback loop for position control is constructed.

Next, the operation of the reference table creating means 1 will be described with reference to the flowchart of FIG.

First, according to the target value generated by the target position generating means 5, the multi-phase linear motor mover is moved to the first position at a constant speed (step S1). Next, the mover is driven to the second position by giving the same target value pattern as that for actually driving the polyphase linear motor (steps S2 and S3). At this time, the microprocessor 6 determines the position P _n of the mover and the difference between the target position and the position of the mover, that is, the control deviation E _n , to be 1 msec. The data is stored in the memory 3 at a constant cycle every time (step S2). When the movement to the second position is completed, the storing operation in this memory is finished.

The position and control deviation stored in the memory 3 generally include high frequency components represented by external noise. Including such high-frequency components in the table is not preferable because it forces the control system to perform meaningless operation. In some cases, the control system may become unstable. In this embodiment, high frequency components are removed by using a high frequency cutoff type linear phase filter (step S4).
~ S6). Here, the cutoff frequency of the filter is set to be lower than the control band that can be estimated from the parameter of the control compensator included in the control calculation means 4. In this embodiment, a 50th-order FIR filter expressed by the equation 2 is used, and its cutoff frequency is set to 20 Hz.

[0021]

[Equation 2] 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, the position time series PF _n and the control deviation time series EF _n, which have been filtered for the position P _n and the control deviation E _n stored in the memory 3, are obtained.

Next, the relationship between the position of the polyphase linear motor mover and the control deviation is created as a table. The filtered position time series PF _n are sequentially checked one by one, and the value of the filtered control deviation time series EF _n is extracted every time it increases by one unit and used as a reference table value. (Steps S7 to S9). The one unit δ referred to here represents the fineness (pitch) of the reference table, and is 0.1 mm in the present embodiment, but may be sufficiently small within the range allowed by the memory capacity.

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 table is referred to according to the rule expressed by the equation 3 based on the position information p obtained from the position detector 10. The correction value k at that location is obtained.

[0024]

[Equation 3] That is, the position information p obtained by the position detection means 10 is converted into an integral multiple of the table pitch δ, and this is offset from the head of the in-memory reference table (index L).
As a result, the correction value k for the current position can be obtained.

The obtained correction value k is used in a form of being added to the result of calculating the control deviation by the control calculating means 4, and the result of the compensation calculation such as PID thereafter is D / as the manipulated variable, that is, the control input. It is input to the A converter 7 to drive the polyphase linear motor.

In order to show the effect of the present invention, FIG. 3 shows a positional deviation in the steady state when the system shown in FIG. 1 is driven at a constant speed, and a comparison with the prior art. It can be confirmed that the position deviation is suppressed by the present invention.

In this embodiment, the case where the position control is carried out has been described, but it is clear that the same means can be used even when the speed control is carried out. Therefore, the detailed description in this case will be omitted. Second Embodiment As shown in the first embodiment, the reference table is created according to the flowchart of FIG. 2, but by repeating this procedure, the position deviation suppression capability can be further enhanced. This procedure is shown in the flowchart of FIG.

Explaining with reference to FIG. 4, first, the first reference table K _m is created according to the flowchart of FIG. 2 (step S41). Then, as described in the first embodiment, the value obtained from the first reference table K _m is added to the control deviation to drive. At the same time according to the flowchart of FIG. 2 to create a second reference table K _'m (step S42), and a new reference table by adding each element to the first reference table K _m (step S
44-S46). By repeating this (step S43), the information that could not be reflected in the table created in the Nth time can be reflected in the table created in the (N + 1) th time, and the position deviation suppression capability can be further enhanced.

In order to show the effect of suppressing the position deviation according to this embodiment, the position deviation waveform when the table is corrected three times is also shown in FIG. It can be confirmed that the position deviation is further suppressed to half as compared with the case where the table is not corrected. Third Embodiment In the first and second embodiments, the reference table storage means 3 is used.
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 characteristics of the mechanical system change. You can do it with 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.

[0030]

As described in the foregoing, according to the present invention,
In systems using a multi-phase linear motor, to sufficiently remove thrust force variation of the multi-phase linear motor, the braking of polyphase linear motor
Control device can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a multi-phase linear motor control device according to a first embodiment of the present invention.

2 is a flowchart showing the operation of the apparatus of FIG.

FIG. 3 is a diagram illustrating an effect of the present invention.

FIG. 4 is a flowchart showing an operation of the device according to the second exemplary embodiment of the present invention.

FIG. 5 is a diagram showing a polyphase linear motor.

FIG. 6 is a diagram showing thrust variation in a polyphase linear motor.

FIG. 7 is a diagram illustrating a conventional technique.

[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: D / A converter,
8: amplifier, 9: polyphase linear motor, 10: position detector.

Continuation of the front page (56) Reference JP-A-7-87620 (JP, A) JP-A-7-143729 (JP, A) JP-A-7-288967 (JP, A) JP-A-63-249494 (JP , A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02P 5/00 B65G 54/02 H01L 21/68

Claims (5)

(57) [Claims] 1. A controller having a servo loop for negatively feeding back the position or velocity in multiphase linear motor selectively switching the coil to be energized according to the position of the movable element, the movement direction each point of said movable element Of the mover in
Have a reference table for holding correction information of the control deviation as the difference between the target position and the current position, wherein the time control of the linear motor, by adding the value obtained by referring to the correction information of the reference table sequential control deviation controlling with polyphase linear motor control device you <br/> characterized. 2. A reference table creating means for creating the reference table based on time series data of the position and control deviation of the mover obtained when the linear motor is driven prior to the table reference. polyphase linear motor control device according to claim 1 wherein. 3. The reference table creating means creates the reference table based on a result of preprocessing the time-series data with a high-frequency cutoff linear phase filter, and the cutoff frequency of the filter is 3. The multi-phase linear motor control device according to claim 2, wherein the control band is set lower than a control band by the servo loop. 4. A driving device for a linear motor comprising a servo loop that negatively feeds back position or speed to a multi-phase linear motor that selectively switches coils to be energized according to the position of the mover. A first reference table holding control deviation correction information at each point,
A second reference table created by the reference table creating means according to claim 2 or 3 while adding a value obtained by sequentially referring to the first reference table to the control deviation, and using the second reference table And a means for correcting the first reference table, and at the time of controlling the linear motor, control is performed while adding a value obtained by sequentially referring to the corrected first reference table to the control deviation. A multi-phase linear motor controller characterized by. 5. The multi-phase linear motor control device according to claim 4, wherein the correction of the first lookup table is repeated a plurality of times.