JPH06178571A - Access controller of linear motor for carriage - Google Patents

Abstract

PURPOSE:To provide a controller where the speedup of access is possible even in the case that the start-up speed of a motor is restricted by the voltage of power source for a driving circuit. CONSTITUTION:An offset input superposing means 10 superposes fixed offset on regular access command, and the operation of the system is started to access the position by a fixed distance apart from the regular target position. Next, it removes the offset input by the control signal of a position detecting means 14; which detects a fixed distance this side of the regular access target position, and at the same time, a gain changeover means 15 changes it over so as to lower the gain of a speed control system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an access control device for a transport linear motor, and more particularly to a control device suitable for shortening access time.

[0002]

2. Description of the Related Art Recently, a conveyance system using a linear motor has been widely used in various fields such as industrial equipment and consumer equipment.

FIG. 5 is a block diagram of a general servo system used for access control of a conventional linear motor. In the figure, 1 is a comparator for comparing the access command input and the output of the position detector 9 (using an optical encoder or the like, the number of pulses is counted to detect the position), and 2 is the output of the comparator 1 converted to a voltage. Position error-voltage converter, 3 is a comparator that compares the output of 2 with the detection output of the speed detector 8 of the linear motor and generates a control signal for driving the linear motor, 4 is a thrust constant of the linear motor, and 5 is a linear The motor load weights, 6 and 7, respectively, represent integrators.

The apparatus shown in FIG. 5 is a numerical value N obtained by converting a distance into an encoder pulse number for position detection as an access command input.
_The feedback control is performed so that the total number of detection pulses from the position detector 9 becomes N ₀ , that is, the moving distance of the linear motor reaches a required target value while applying speed damping with the loop of the speed detector 8. To do. The transfer function (response characteristic of the moving distance x of the linear motor to the command input pulse N ₀ ) H (S) of this system is shown in Equation 1, and the step response of the system obtained from Equation 1 is shown in FIG.

[0005]

[Equation 1]

FIG. 6 (a) shows the response characteristic of the velocity v, and FIG. 6 (b) shows the response characteristic of the moving distance x. In both figures, the horizontal axis is normalized by w _n t. Simultaneously with the start of access, the linear motor is accelerated by the maximum position error signal, and when the speed detection signal increases as the speed increases, damping starts and the speed response becomes slow. The change point where the slope of the speed changes from positive to negative is the time when the position error signal ΔVp and the speed detection signal ΔVv shown in FIG. 5 become equal.

The moving distance x is the integral of the speed v. The larger the damping coefficient ζ, the stronger the speed control system operates and the faster the speed deceleration starts, so the maximum speed decreases.
Although the characteristics themselves are gradual and the convergence time of access tends to be extended, the system has a feature that it always converges automatically. Incidentally, the theoretical w _n t value at which the moving distance x reaches the range of one encoder with respect to the target value when ζ is set to about 1 is about 17. That is, for example, if the access accuracy of the linear motor is set to within 1 encoder resolution and the access time is set to 0.2 sec, then w _n
The value is 85, and each parameter may be set based on this value from Equation 1, and it is also a control device that is easy to design.

As related known examples of this kind, there are JP-A 1-320647 and JP-A-2-179975.

[0009]

However, in the access control apparatus of FIG. 5, even if the system is designed to access within 0.2 sec within the resolution of one encoder as described above, the actual access time is It has the drawback of exceeding 0.2 seconds.

Hereinafter, this point will be described.

As a concrete example, the thrust constant is 6.4 N / V and the weight is 3
A linear motor that bears a load of 0 Kg reduces the distance to 20 mm.
Access is made in 2 seconds, and encoder resolution is 1
μm, access time 0.2sec encoder resolution 1μ
The convergence time is within m. Table 1 shows specific design values of each transfer element shown in FIG. 5 in this specification.

[0012]

[Table 1]

FIG. 7 shows the analysis result of the step response of the system when the parameters shown in Table 1 are designed. In the figure (a)
Is the speed v, (b) is the moving distance x, (c) is the control voltage ΔVp, Δ
The response of Vv and ΔVc is shown. The curves shown by broken lines in both FIGS. (A) and (b) are ideal characteristics for realizing an access time of 0.2 sec. The maximum value of the speed v reaches about 0.55 m / s, and the time for the movement distance x to converge within 1 μm of the encoder 1 resolution for the access target distance of 20 mm is (b).
It is difficult to read from, but it is calculated about 0.2sec
Is.

However, in an actual system, it is difficult to set the velocity v and the moving distance x to theoretical response characteristics such as the characteristics of the broken line. The reason is that the acceleration of the linear motor is about 15 G (about 147 m /
s ² ), about 4400N is required as the generated thrust, and considering the thrust constant of 6.4N / V of the motor used, the required power supply voltage of the motor drive circuit is about 690V, which is a high power supply without any practicality. This is because it ends up. After all, considering the voltage usage range of the integrated circuit used for the motor drive circuit, the economical efficiency of the device, etc., the setting of about 50V is a reasonable value for the power supply voltage. As a result, a constraint naturally arises, and it is not possible to obtain a sharp rise in velocity as shown by the characteristic of the broken line.

The solid curve in FIG. 7 shows the response of speed and movement distance when the power supply voltage of the motor drive circuit is set to 46V. By setting the power supply voltage to 46V, the maximum thrust of the motor is about 294N and the generated acceleration is about 1G (9.8m).
/ s ² ) and the motor speed is about 1 acceleration after the access is started.
It can rise only at G, and accordingly, the response of the moving distance becomes gentler than the ideal characteristic indicated by the broken line. FIG. 7C shows the response of the control voltage of each part. After the access is started, the speed detector 8 outputs a detection signal ΔVv which increases linearly as the motor speed in FIG. The position error-voltage converter 2 outputs a detection signal ΔVp that decreases with the passage of time according to the change in the moving distance of
And ΔVp both respond in an asymptotic direction with the passage of time. The difference ΔVc between the two output by the comparison amplifier 3 (gain is 47 times) is the power supply voltage 46V of the motor drive circuit,
That is, since the servo system becomes active when the input conversion difference of the comparison amplifier 3 becomes within about 1 V, the response of the originally designed system starts and the damping of the motor speed starts. Although ΔVc in the diagram (c) is expressed by the input conversion difference of the comparison amplifier 3, the time T ₀ when ΔVc becomes about 1 V is about 0.039 sec. The specific design example using the access control device in FIG. 5 has been described above.

As can be inferred from the response characteristic of FIG. 7B, the access time by the actual control of the solid line is longer than the access time by the theoretical characteristic of the broken line, and strictly speaking, within 1 μm which is one encoder resolution. Compared with the convergence time, the theoretical characteristic is about 0.2 sec, but in actual control it is extended to about 0.25 sec.

The object of the present invention is to solve the above-mentioned problems, and even if the motor start-up speed is restricted by the restriction of the power supply voltage as shown by the response characteristic of the solid line in FIG. 7, the theoretical response shown by the broken line. It is to provide an access control device capable of obtaining an access time equivalent to

[0018]

In order to achieve the above object, according to the present invention, a fixed offset input is superimposed on a regular access command input, or a fixed offset voltage is applied to the output of the position error-voltage converter. First, the system is operated so as to access a position farther than the regular access position by a fixed distance. Then, by the position detecting means for detecting a position before the regular access target position by a fixed distance, the offset input or the offset voltage is removed at the time when the position reaches the fixed distance before the target value, and at the same time, the speed is reduced. The configuration is such that switching control is performed so as to reduce the gain of the control system.

[0019]

The offset input or the false excessive access command due to the superposition of the offset voltage delays the start point of speed damping, increases the maximum speed of the motor, and speeds up the response of the moving distance after the start of damping. Works. That is, the access time to the regular access target position is relatively shortened. Further, according to the identification result by the position detecting means, the offset input or the offset voltage is removed before the fixed distance of the regular access target position, but at the same time, the gain of the speed control system is controlled so as to be lowered. The system responds convergently towards the normal access target position without any abrupt change in velocity due to removal.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an access control device for a linear motor according to the present invention. In the figure, 10 is an offset input superposing means, 14 is a position detecting means configured to detect a fixed distance before a regular access target position, and 15 is a gain switching means of a speed control system. The parts with reference numerals indicate the same or equivalent parts, and their operations are also the same.

First, the configurations and operations of 10, 14 and 15 different from the conventional access device shown in FIG. 5 will be described.

The offset input superposing means 10 is composed of an offset input source 11 for generating a fixed offset ΔN ₀ with respect to the regular access command input N ₀ , a switch 12 and an adder 13, and the regular access command input N _0. To Δ
It operates so as to superimpose N ₀ and output an access command of N ₀ + ΔN ₀ . For example, when the encoder resolution for position detection is 1 μm as described above, a value of 20 × 10 ³ is input as N ₀ of the access command input when accessing a distance of 20 mm, whereas ΔN ₀ Is set to a value of 2000 and operates so as to output 22 × 10 ³ as N ₀ + ΔN ₀ . The switch 12 is controlled by the control signal Es from the position detecting means 14 and operates so as to be ON when Es is "L" and OFF when Es is "H".

The position detecting means 14 is constructed so as to detect the fixed distance before the regular access target position by monitoring the moving distance x of the motor after the start of access, and detect the fixed distance before the regular access target position. “L” when detected
Outputs a control signal Es which is inverted from "H" to "H", and the offset input superposition means 10 and the gain switching means 15 are generated by Es.
Operate to control. The time point before the fixed distance from the regular access target position means that the access target position is 20
mm (access command input N ₀ = 20 × 10 ³ ), for example, 18 mm (position encoder count number = 18 × 10
³ ) etc. are set.

The gain switching means 15 operates so that the control signal Es from the position detecting means 14 reduces the gain when Es is inverted from "L" to "H". FIG. 2 shows an example of its concrete structure. In FIG. 2, 16 is an attenuator,
Reference numeral 17 is a changeover switch. The changeover switch 17 is
When the control signal Es is "L", the contact is on the A side, and Es
Is configured to close to the B side when is "H",
Therefore, the gain is high (gain = until the fixed distance before the regular access target position is detected by the position detecting means 14 (gain =
1) After the fixed distance before the regular access target position is detected, the gain is low (gain = 1 / k).

The overall operation of this structure will be described below with reference to FIG.

Here, the response of the system when the present invention is applied will be described based on the same conditions as the specific design example of the conventional access device shown in FIG. That is, assuming that each transfer element of the servo system is set to the distance shown in Table 1 and a distance of 20 mm is accessed in 0.2 sec (convergence time within an encoder resolution of 1 μm), the superposition offset ΔN ₀ value by the offset input superposition means 10 is 2000 2 mm in distance conversion, and the moving distance detection point by the position detecting means 14 is 18 mm 2 mm before the target value (count number of position encoder = 18 × 1).
0 ³ ), the gain of the attenuator 16 of the gain switching means 15 is 0.9.
The operation when (k = 1.1) is set will be described. It should be noted that in the characteristics of FIG. 3, the solid curve is for the present invention, and the broken curve is for the conventional device shown in FIG. 7, and is also shown for comparison.

N ₀ = 20 × 10 ³ as an access start command
Is input, the offset ΔN ₀ = 2000 is superposed by the offset input superposing means 10, and 22 × is input to the comparator 1.
A position error signal of 10 ³ is added. At this time, the motor starts to accelerate with the maximum control signal ΔVc because the speed and movement distance are zero, but the power supply voltage of the motor drive circuit is 46 V and the generated thrust is limited to about 294 N, so the motor speed is about 1 G acceleration. Starts climbing at (9.8m / s). This operation is shown in FIG.
3 is the same as that of the conventional access device shown in FIG. 3, and therefore there is no difference in the response of the speed v and the movement distance x in FIGS.
Further, as shown in (c), the speed detector 8 and the gain switching means 1
The same applies to the speed detection signal ΔVv via 5.

However, the control signal ΔVp output from the position error-voltage converter 2 is higher than that of the conventional access device shown in FIG. This is because even if the movement distance characteristics are the same, the offset input superposing means 10 overlaps the offset distance of 2 mm (ΔN ₀ = 2000) and operates. In response to this, the control signal ΔVc output from the comparison amplifier 3 (expressed by the input conversion value of the comparison amplifier 3) also changes in a higher state than in the case of the conventional access device shown in FIG.

Then, after the time To becomes asymptotic between ΔVv and ΔVp due to the increase of the motor speed and the difference between them is within about 1 V (the output of the comparison amplifier 3 is about 47 V), the servo system is in the active state, which is the original condition. Servo control starts. In this case, To is a delay of about 0.042 sec from 0.039 sec in the case of the conventional access device shown in FIG. 7, because the intersection of ΔVv and ΔVp shifts to the right on the time axis.
By giving an offset to the access target position,
The start point of velocity servo, that is, velocity damping, is delayed, and access starts toward a large false target position of 22 mm that includes an offset of 2 mm. Also operates as shown by the solid line so that it is faster than the conventional device (broken line and characteristics).

Next, the distance traveled by the running of the motor is 2 mm before the original access target of 20 mm, that is, 1
When Ts reaches the position of 8 mm (calculated about 0.07 sec)
Then, the control signal Es of the position detection means 14 is inverted from "L" to "H", whereby the switch 12 of the offset input superposition means is opened, and the changeover switch 1 of the gain switching means.
The contact of 7 switches from the A side to the B side. That is, at the time of Ts, the initially superimposed offset is removed, and at the same time, the gain of the speed control system is switched to a low value. As a result, after time Ts, a convergence response is reached in which the remaining distance of 2 mm with respect to the original access target distance of 20 mm is accessed, but the gain of the speed control system is also reduced, so that the speed is rapidly increased due to offset removal. Speed without change,
The movement distance response becomes slow.

The embodiment of FIG. 1 has been described above. As can be inferred from the response characteristic of FIG. 3B, the access time according to this embodiment is faster than that of the conventional access device of FIG. 7, and is calculated to be about 0.19 sec (encoder resolution of 1 μm).
(convergence time within m), and it is possible to obtain almost the same performance as the access time of about 0.2 sec due to the theoretical characteristics described above.

FIG. 4 is a block diagram showing another embodiment of the linear motor access control apparatus according to the present invention. In the figure, reference numeral 18 denotes an offset voltage superimposing means composed of an offset voltage supply source 19, a switch 20 and an adder 21, and other parts designated by the same reference numerals as those in FIGS. 5 and 1 are the same or equivalent parts. , Its operation is also the same.

FIG. 4 is different from the embodiment of FIG. 1 in that the offset ΔN ₀ is superimposed on the access command input N _0, but at the output end of the position error-voltage converter 2, ΔN ₀ of FIG. The offset of a numerical value corresponding to is superimposed as a voltage. The switch 20 is controlled by the control signal Es of the position detecting means 14 like the switch 12 of the embodiment of FIG.
Is ON when it is "L", and OFF when it is "H". Therefore, ΔN ₀ = 20 in the case of the embodiment of FIG.
The voltage corresponding to the offset of 00 is G shown in Table 1.
Considering the p-value, it is 1.466V. Therefore, by setting the voltage value of the offset voltage supply source 19 to 1.466V, it is possible to perform exactly the same control as in the embodiment of FIG. 1 and its response characteristics. Is the same as that shown in FIG.

The embodiments of the present invention have been described above.
In FIGS. 1 and 4, the dedicated position detecting means 14 is provided to detect a fixed distance before the regular access target position, but this is not particularly limited.
For example, the position detector 9 for servo may have this function. Further, the configuration in which the gain switching means 15 is also provided exclusively is shown, but the configuration is not limited to this. For example, in the case where the servo speed detector 8 is composed of a digital circuit, the gain switching means 15 may be used. It is easy to have a function. Further, when the comparison unit that detects the error between the access command input unit and the position detector output is configured by, for example, a microprocessor or the like, control of offset superposition and removal should be performed by software processing. It is also possible, and various modifications are easy within the scope of the present invention.

[0036]

As described above, according to the present invention, the start point of speed control is delayed by the false excess access command due to the offset input or the superposition of the offset voltage, and the maximum speed of the motor is increased to speed control. The system operates so that the response of the moving distance after the start becomes faster. As a result, the access time is shortened. For example, in the case of accessing 20 mm, it is about 0.25 sec (convergence time within 1 μm which is the encoder resolution) in the conventional access device.
The speed can be increased to 19 seconds, and a performance almost equal to the access time of about 0.2 seconds due to the theoretical characteristics described above can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a specific configuration diagram of a gain switching unit of FIG.

3 is a response characteristic diagram of speed, movement distance, and control voltage of each part in the embodiment of FIG.

FIG. 4 is a configuration diagram showing another embodiment of the present invention.

FIG. 5 is a configuration diagram showing a conventional linear motor access control device.

6 is a theoretical response characteristic diagram of speed and movement distance of the apparatus of FIG.

FIG. 7 shows a speed, a movement distance, and an actual control of the apparatus of FIG.
It is a response characteristic view of a control voltage.

[Explanation of symbols]

 8 ... Velocity detector, 9 ... Position detector, 10 ... Offset input superposition means, 14 ... Position detection means, 15 ... Gain switching means, 18 ... Offset voltage superposition means.

Claims (3)

[Claims] 1. A transport linear motor device comprising a position detector configured by an optical encoder or the like for detecting the position of the linear motor, and a speed detector for detecting a traveling speed of the linear motor, and an access command. A first comparator compares the input with the output of the position detector to detect a position error, and the position error is passed through a control amplifier and then compared with the output of the speed detector by a second comparator to obtain the linear error. In an access control device for a linear motor for conveyance configured to obtain a control signal of a motor, an offset superimposing means for superimposing an offset on the position error, a position a fixed distance before the access target position corresponding to the access command input. Is provided with a position detecting means for detecting the gain, and a gain switching means for switching the gain of the speed detector output. The tatami means superimposes an offset on the position error, and when the access position reaches a fixed distance before the target position by the traveling of the linear motor, the superposition offset by the offset superposition means is removed by the control signal of the position detection means. At the same time, the access control device for the linear motor for conveyance is characterized in that the gain of the gain switching means is controlled to be lowered. 2. An access control device for a linear motor for conveyance according to claim 1, wherein said offset superimposing means is constituted by offset input superimposing means for superimposing a fixed offset command input on said access command input. 3. An access control device for a linear motor for conveyance according to claim 1, wherein said offset superimposing means comprises offset voltage superimposing means for superimposing an offset voltage on the output of said control amplifier.