JPH01218395A - Miniature step driver for stepping motor - Google Patents

Abstract

PURPOSE:To largely improve a step response of miniature step drive by stepwisely switching an exciting signal of input one pulse by an additional pulse. CONSTITUTION:An additional pulse generator 34 including an oscillator 90 is provided, and an exciting signal of input one pulse is stepwisely switched by an additional pulse. Thus, when one pulse is input by a miniature step drive, the exciting signal is not immediately switched for one pulse, but the signal is stepwisely switched by the additional pulse. Accordingly, the step response of the miniature step drive is largely improved, its rotary vibration is reduced, a settling time is shortened to be adapted for a high speed control.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a mini-step drive device for a step motor, and in particular, it is suitable for driving a table of a machine tool, a stage of a measuring device, etc., and finely changes the magnitude of each phase excitation signal of the step motor. By doing so, the position of the stable point is gradually moved and the step angle is subdivided. The present invention relates to an improvement of a mini-step drive device for a step motor as described above.

[Conventional technology]

In recent years, open-loop control has become possible as a drive source for machine tool tables, measuring equipment stage, etc., and servo mechanisms can be configured easily and with high precision without using feedback elements such as encoders and potentiometers. Step motors are attracting attention because of their ability to There are basically two types of step motors: variable reluctance (hereinafter referred to as VR) type and permanent magnet (hereinafter referred to as PM) type, but PM type step motors, which also include the type usually called hybrid type, are basic. Specifically, it is a two-phase AC synchronous motor, and normally each phase excitation signal is given as a rectangular wave of, for example, 200 to 800 pulses per rotation of the motor. Generally, the behavior of the motor rotating shaft (rotor shaft) when driven by only one pulse is called a step response, and Figure 9 shows the behavior of the motor rotating shaft (rotor shaft)
As shown in the example when driven with a 00 pulse rectangular wave, a damped oscillatory transient response occurs. This transient phenomenon in step response resonates in relation to the drive frequency, causing vibration.Also, when a positioning table is driven by a step motor for precise positioning, there is a settling time during positioning, so high-speed control is required. There was a problem. On the other hand, in recent years, by finely changing the magnitude of each phase excitation signal, the position of the stable point is gradually moved, and the step angle is subdivided, for example, so that the motor rotates once in several thousand pulses. A so-called mini-step drive has been put into practical use, which improves the drive resolution per pulse and achieves smooth rotation, especially at low speeds. There are methods to finely change each phase excitation signal, such as by switching resistances and by pulse width modulation by switching. In the case of bipolar drive, PM type step motors have two methods, as shown in Fig. 10. A common method is to change the phase excitation current into a sine waveform (first phase) and a cosine waveform (second phase). The drive device for performing this mini-step drive is basically configured as shown in FIG.
In order to divide the cycle into 216 equal parts by mini-step driving, for example,
8-bit data k (k=o...2
16) Make. A sine wave sinθk corresponding to this data k (θ=k
・The values of Δθ, Δθ; 2π/216> and the cosine wave COSθ are output from the read-only memory (ROM) section 14, and are converted into digital/analog (D/A> converter section 16
After D/A conversion, the signal is input to the drive circuit 18 as an excitation signal. The drive circuit 18 drives the step motor 20 by, for example, constant voltage drive. The step angle of the step motor 20 in normal drive is 1.8 degrees, and it rotates 7.2 degrees in one cycle of the excitation current waveform (8 steps in the case of 1-2 phase excitation) in mini-step drive. , when dividing into 216 equal parts by mini-step driving, the step angle in one step is 1/30 degree. According to this mini-step drive, for example, one revolution is 128
The step response when driving with 00 pulses is as shown in Figure 12, and the amplitude of the step response is 1/1 compared to the general drive shown in Figure 9 above.
0 or less, the settling time is also improved to about 1/4.

[The problem that the invention tries to solve! ! ! ] However, even in this mini-step drive, a transient response exists microscopically, and depending on the application, the excessive amount of the step response and the settling time may become a problem. In particular, when the driving frequency becomes high and the next pulse enters before settling and matches the phase of the transient response caused by the previous pulse, the amplitude may be emphasized and resonance may occur, as shown in Figure 13, for example. Ta. In order to solve these problems, it is possible to further increase the number of divisions of the mini-step drive, but this increases the drive frequency and requires high-frequency oscillation of input pulses with high precision, and the number of set pulses increases. As a result, the count value of the ring counter becomes enormous, resulting in a problem that the driving device becomes extremely expensive. OBJECTS OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and uses a simple circuit configuration to significantly improve the step response of the mini-step drive, reduce rotational vibration, and reduce the settling time. An object of the present invention is to provide a mini-step drive device for a step motor that can be adapted to high-speed control by shortening the time.

[Means to solve the problem]

The present invention provides a mini-step drive device for a step motor that gradually moves the position of a stable point and narrows the step angle by finely changing the magnitude of each phase excitation signal of the step motor. The above object is achieved by providing an additional pulse generating section that generates a predetermined number of additional pulses for each input pulse, and by using the additional pulses, the excitation signal for one input pulse is switched in stages.

[Effect]

In the present invention, as shown in Fig. 2, when one pulse is input by minischip drive, the excitation signal is not suddenly switched by one pulse, but a predetermined number of additional pulses are applied for each input pulse as shown in Fig. 3. The excitation signal is switched in stages by the additional pulses. Therefore, with a simple (that is, inexpensive) circuit configuration, the step response of mini-step drive can be greatly improved, rotational vibrations can be reduced, and settling time can be shortened to adapt to high-speed control.

【Example】

Hereinafter, with reference to the drawings, an embodiment will be described in detail in which the present invention is applied to a unipolar drive in which a human phase and a B phase are created by switching the A phase and B phase according to rotation. The basic configuration of this embodiment is as shown in FIG.
A ring counter section 12, a ROM section 14, and a D/A-converter section 16 are substantially similar to the conventional example shown in FIG. 11 mentioned above.
, a drive circuit 18, and a step motor 20, an oscillator 9 for generating a predetermined number (16 in the embodiment) of additional pulses for each input pulse.
This differs from the conventional example in that an additional pulse generating section 34 including 0 is provided, and the excitation signal for one input pulse is switched in stages (16 stages F# in the embodiment) using the additional pulses. Specifically, this embodiment is configured as shown in FIG. In FIG. 4, the input pulse CW in the forward direction and the input pulse CCW in the reverse direction are supplied to the inverter 40A, respectively.
40B, the D flip-flops 42A, 42B, 44A, 44B of the additional pulse generating section 34, and the Nant gates 46A, 46B, and are input to the lowest reversible counter 12A of the ring counter section 12. Here, the D flip-flops 42A, 42B, 44
A, 44B are the Nant gates 46A, 46B until one cycle of additional pulses of, for example, 16 pulses per input l pulse generated by the additional pulse generator 34 pass through.
It has a function to hold in an open state. The outputs of the D flip-flops 44A and 44B are output from the D (SR) flip 7'70 of the subsequent forward/reverse switching section 30.
The rotational direction (
CW or CCW) is held. The rotational direction hold signal output from the D flip-flop 47 is input to the D flip-flop 48, and is synchronized with the output of the NOR gate 120 of the 1/4 cycle detection section 36, which will be described later. The output of the D flip-flop 48 is input to an AND gate 52 together with the output of a changeover switch 50 for selecting the correction table switching point. The changeover switch 50 is turned on when it is desired to switch the correction table at the same time as the direction of the input pulse is reversed, and after the direction of the input pulse is reversed, the rotation axis will not jump due to a deviation in the correction value due to the difference in the rotation direction. Cycle (in case of unipolar drive) It is turned off when it is desired to switch the correction table at a location linked to the position. The rotational direction hold signal output from the D flip-flop 47 is also input to an AND gate 54 together with the output of an inverter 53 that inverts the output of the changeover switch 50. Therefore, when the changeover switch 50 is on, the AND gate 52 is turned off, the AND gate 54 is turned on, and the output of the D flip-flop 47 is input to the mother-or gate 56. On the other hand, when the changeover switch 50 is off, the AND gate 52 is on, the AND gate 54 is off, and the output of the D flip-flop 48 is input to the OR gate 56. The output of the OR gate 56 is input to an AND gate 62 together with the output of a changeover switch 60 for selecting whether or not to use independent correction tables for normal rotation and reverse rotation. The changeover switch 60 has a problem of uneven step angle due to the difference in the static angle characteristics when the step motor 20 rotates in the forward direction and in the reverse direction. On the other hand, the difference in static angle characteristics depending on the rotation direction is not a problem, and the same correction table (for example, average value) can be used during forward rotation and reverse rotation. It is turned off when it is not available. The output of the AND gate 62 is input to the ROM section 14 as the ROM address switching signal 1. Mainly the above D flip-flops 47 to AND gates 62
In this embodiment, it is determined whether the input pulse is a forward rotation pulse or an inversion pulse, and when the changeover switch 60 is turned on, the correction table is switched between when the motor rotates in the normal direction and when the motor rotates in the reverse direction. A normal rotation/reverse rotation switching section 30 is configured. The ring counter section 12 is connected to the Nantes gate 46A.
, 46B, and the logical sum of the negation of the outputs of the Nant gates 46A and 46B is calculated by the frequency division counter 94B of the additional pulse generator 34. latter 4
a NOR gate 70 that outputs to a bit binary counter;
For example, a group of setting switches 72A to 72C for initially setting arbitrary values to the reversible counters 12A to 12C when adjusting the D/A converter section 16, and a load switch 74 that is turned on when performing the initial setting. and the load switch 74 output to the reversible counters 12A to 12C.
and the reversible counter 1.
A zero switch 78 that is turned on when clearing the count values 2A to 12C, a NOR gate 80 that inputs the output of the zero switch 78 to the reversible counters 12A to 12C, and a detection of the output of the NOR gate 80 and the following 16 pulses. Part 38
The negation of the logical sum of the multivibrator 38F output is input to the reset terminals of the D flip-flops 42A, 42B, 44A, and 44B, and when 16 additional pulses equal to 1 input pulse have passed, these hold states are reset. It mainly consists of a Noah gate 82 for Here, the reversible counter 12A is used to count additional pulses, and the reversible counters 12B and 12C are used to count input pulses. The ROM section 14 has three ROMs 14A to 14A having addresses corresponding to the count values of the ring counter section 12.
It is composed of 4C, all of the ROM14A and RO
The upper half of the diagram of M14B outputs the data for the first phase (human face), and the lower half of the diagram of ROM14B and the ROM14C
All of them are adapted to output second phase (B phase) data. Each of the ROMs 14A to 14C includes a correction table 32A for normal rotation and a correction table 32A for reversal, which contain data necessary to obtain correction excitation signals for normal rotation (solid line) and reverse rotation (broken line) as shown in FIG. 5, for example. As shown in Figure 6, the table 32B has separate addresses for forward rotation and reverse rotation (in the example of Figure 6, addresses 1 to 100 are for forward rotation and addresses 101 and above are for reverse rotation).
remembered. Therefore, by switching the addresses in each of the ROMs 14A to 14C according to the state of the ROM address switching signal 1 inputted from the normal/inversion switching section 30, the correction table can be easily switched. The D/A converter section 16 amplifies the outputs of the A-phase D/A converter 16A, the B-phase D/A converter 16B, and the A-phase/A converter 16A, and outputs the outputs from the drive circuit 18. An operational amplifier 16C outputs to the A and A phases of
It mainly consists of an operational amplifier 16E that amplifies the output of 6B and outputs it to the B and B phases of the drive circuit 18. The drive circuit 18 switches the A-phase and B-phase outputs of the D/A converter section 16 according to the rotation to create A-phase and ■phase;
The step motor 20 is driven by unipolar drive. The additional pulse generating section 34 according to the present invention is, for example, 8M
an oscillator 90 that generates a Hz pulse signal;
An inverter 92 that inverts the output of 0, the first stage is a 4-bit binary counter that divides the output of the inverter 92 by 1/16 to make it 500 KHz, and the second stage is a 4-bit binary counter that further divides the output of the previous stage. A frequency division counter 94A is used as a counter, the front stage is a 4-bit binary counter that further divides the frequency of the output of the frequency division counter 94A, and the rear stage is a NOR of the ring counter section 12, and the output of the gate 70 is divided into 1/16. Either the frequency division counter 94B, which is a 4-bit binary counter that divides the frequency and outputs it to the last output 6 pulse detection section 38, or the frequency division output of the downstream stage of the frequency division counter 94A or the frequency division output of the front stage of the frequency division counter 94B. Then, change the data selector 96 and the set value of the data selector 96 (i.e., the layer separation rate) to create an additional pulse of the necessary period according to the stepwise switching time (T in Figure 3). By using the setting switches 98A to 98G and inverters 100A to 100C to change the slope of the additional pulse (that is, the stepwise switching time T), the output of the data selector 96 is shaped into a waveform, so that the pulse width is constant regardless of the period. and the Nant gates 46A, 46B as additional pulses.
It is mainly composed of a D foot 70 and a D foot 102 and 104 that output to. A 4-bit binary counter subsequent to the frequency division counter 94B receives the D
It is reset by the AND of the outputs of flip-flops 44A and 44B. Further, the data selector 96 outputs the input to the Do terminal to the Y terminal when all of the setting switches 98A to 98C are turned off, and outputs the input to the Do terminal to the Y terminal when all of the setting switches 98A to 98C are turned on. Outputs the input to the Y terminal. The additional pulse generating section 36 further includes 16 additional pulses for one input pulse from a predetermined combination of the outputs of the lowest reversible counter 12A of the ring counter section 12.
a Nant gate 38A that detects that a pulse is generated;
38B and 38C, an integrator 38D that delays the output of the Nant gate 38C, and an output of the NOR gate 70 of the ring counter section 12 whose frequency is divided by the output of the integrator 38D or the 4-bit binary counter downstream of the frequency division counter 94B. (one of them is selected in advance), and a multivibrator 38F that generates a reset pulse according to the output of the inverter 38E and outputs it to the NOR gate 82 of the ring counter section 12. A pulse detection section 38 is provided, and this 1
When the predetermined 16 additional pulses are generated by the output of the 6-pulse detection section 38, the D flip-flop 4
2A, 42B, 44A, and 44B have been reset. In this embodiment, not only the normal rotation/reverse rotation switching section 30 is provided, but also the changeover switch 60 is turned on,
When the forward and reverse independent data is selected, instead of immediately switching between the forward and reverse data, in the case of the unipolar drive of the embodiment, as shown in FIG. 1/4 to delay data switching until 1/4 cycle when both data and inversion data become zero (wJ magnetic current is zero) and the correction result by the forward rotation data and the correction result by the inversion table match. A period detection section 36 is provided. This 1/4 cycle detecting section 36 detects the ring counter section 1.
Inverters 110A and 110B invert the outputs QC and QD of the top reversible counter 12C of No. 2 and
AND gates 112A to 112D that output the AND of a predetermined combination of the outputs of the reversible counters 10A and 110B and the outputs QC and QD of the reversible counter 12C, and the AND gate 11
Inverter 1 that inverts and delays the output of 2A to 112D
14A to 114D and integrators 116A to 116D, the output of each AND gate 112A to 112D, and each integrator 11
AND gates 118A to 118D that output the AND of the outputs of 6A to 116D, and the AND gates 118A to 11
It mainly consists of an OR gate 120 that outputs the logical sum of 8D as a 1/4 period signal to the D flip-flop 48 of the forward/inversion switching section 30. When the changeover switch 60 is switched, this 1/4
R until the period detection section 36 outputs the 1/4 period signal.
By delaying the generation of the OM address switching signal 1, it is possible to prevent the rotation angle from jumping due to a deviation in the correction value, even when using the step motor 2o, which has a large hysteresis in static angle cleanliness between forward and reverse rotations. The operation of the embodiment will be explained below. The oscillator 90 of the additional pulse generator 34 is always in operation as long as the power is on, and the data selector 96 (
From the D flip-flop 104), the setting switch 98
Additional pulses of a predetermined frequency set in A to 98C are always generated. Therefore, the input pulse CW or CCW is input to the D flip-flop 42A or 42B, and the output of the D flip-flop 44A or 44B causes the Nant gate 46A
Or when 46B is opened, the additional pulse is input to the lowest reversible counter 12A. Said Nantes Gate 46A
Alternatively, the input pulse 46B is opened until the 16 pulse detection section 38 detects 16 pulses, so that the input pulse is divided into 16 predetermined pulses as shown in FIG. 3 mentioned above. Therefore, one mini-step pulse can be driven stepwise, and the driving resolution per pulse can be further reduced.
The settling time can be shortened, the step response of the mini-step drive can be greatly improved, and rotational vibration can be further reduced. The time T required for the stepwise switching, that is, the slope of the additional pulse output, is set so that there is no delay even when the input pulse is at the highest frequency, that is, the next input pulse is input after 16 additional pulses have been output. , setting switches 98A to 98C
is set. In the example, if the input pulse frequency is 250- or less, the output time of the additional pulse is set to 811 SeC, and 250 H
When exceeding z, it is set to 41st3c. It should be noted that the setting switches 98A to 98C may be automatically switched according to the speed, and the inclination may be automatically switched for each speed zone so that there is no delay even at the highest distance within the zone. is also possible. In this embodiment, generation of a predetermined 16 additional pulses is determined by the count value of the output of the lowest reversible counter 12A, or by dividing the input of the lowest reversible counter 12A by 1/16 at the subsequent stage of the frequency dividing counter 94B. Since it is possible to detect the occurrence of any of the signals frequency-divided into , it is possible to reliably detect the occurrence of 16 pulses. Note that the method for detecting the occurrence of the 16 pulses is not limited to this, and it may be detected from only one of them, or may be detected using another method. Further, in this embodiment, since the forward rotation/reverse rotation switching section 30 is provided, 1. When the changeover switch 60 is turned on, RO is output from the forward/reverse switching unit 30 depending on the forward direction (cw) or reverse direction (ccw) of the input pulse.
ROM address switching signal 1 is input to M14 A to 14 and C, and among the addresses of ROM14A to 14C, for example, addresses 1 to 100 are selected during normal rotation, and 10 during reverse rotation.
Addresses 1 and onwards are selected. Therefore, different correction tables are used for normal rotation and reverse rotation, so R
By storing them in the OMs 14A to 14C, it is possible to improve the step pitch accuracy, make the amount of rotation per pulse more uniform, improve the constant speed of rotation, and further reduce vibration. Note that data correction for normal rotation and inversion corresponding to the additional pulse of the present invention can be performed, for example, by linear correction in which one input pulse is simply divided into 16 parts. In experiments conducted by the inventors, the step response when performing stepwise switching using the additional pulses of the present invention is as shown in FIG. It is clear that the step response is significantly improved. In this embodiment, the normal rotation/reverse rotation switching section 34 and 1/4
Since the period detection section 36 is provided, more accurate control can be performed. Note that these circuits can also be omitted. In the embodiment described above, the present invention is applied to mini-step drive with a number of divisions of 256 by unipolar drive, but the scope of application of the present invention is not limited to this, and the number of divisions of mini-step drive may be any number. Further, the number of divisions (the number of additional pulses) according to the present invention is not limited to 16, and the present invention can be similarly applied to a bipolar drive in which the A phase and B phase are driven as they are. In the case of this bipolar drive, the corrected excitation signal is as shown in FIG. 8, for example. Further, in the above embodiments, the present invention is applied to excitation current correction by constant voltage driving, but the scope of application of the present invention is not limited to this, and may be similarly applied to excitation voltage correction. Can be done.

【Effect of the invention】

As described above, according to the present invention, the step response of mini-step drive can be significantly improved and the rotational vibration characteristics can be improved with a simple and therefore inexpensive circuit configuration. Further, it has excellent effects such as shortening the settling time and responding to high-speed control.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the basic configuration of an embodiment of a mini-step drive device for a step motor using unipolar drive according to the present invention, and Fig. 2 shows - during in-shell drive and mini-step drive. FIG. 3 is an enlarged diagram of the section ■ in FIG. 2, which shows a comparison of input pulses for mini-step drive and additional pulses according to the present invention. FIG. FIG. 5 is a diagram showing an example of the corrected excitation signal used in the embodiment, and FIG. 6 is a diagram showing an example of the correction table. , FIG. 7 is a diagram showing an example of the step response in the above embodiment, with speed change as the vertical axis, FIG. 8 is a diagram showing an example of the excitation signal after correction in the case of bipolar drive, and FIG. 10 is a diagram showing an example of a step response in general rectangular wave driving with speed change as the vertical axis; FIG. 10 is a diagram showing an example of an excitation signal in mini-step driving by normal bipolar driving; The figure is a block diagram showing an example of the basic circuit configuration of the mini-step drive device, and FIG.
FIG. 13 is a diagram illustrating an example of a step response in mini-step driving with the vertical axis representing a change in speed. FIG. 13 is a diagram illustrating an example in the case of resonance. 12... Ring counter section, 12A to 12C... Reversible counter, 14... Read only memory (ROM) section, 14A
~14C...ROM. 16... D/A converter section, 16A, 16B... D/A converter, 18... Drive circuit, 20... Step motor, 34... Additional pulse generation section, 38... 16 pulses Detection unit, 90... Oscillator, 94A, 94B... Frequency division counter, 96... Data selector, 98A to 98C... Setting switch.

Claims (1)

[Claims] (1) A mini-step drive device for a step motor in which the position of the stable point is gradually moved and the step angle is made finer by finely changing the magnitude of each phase excitation signal of the step motor. A mini-step drive device for a step motor, characterized in that an additional pulse generator is provided that generates a predetermined number of additional pulses for each input pulse, and the excitation signal for one input pulse is switched in stages using the additional pulses.