JP4070280B2 - Stepping motor step-out detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a stepping motor step-out detection device for detecting stepping motor step-out.
[0002]
[Prior art]
Conventional stepping motor out-of-step detection devices are equipped with a detection device such as an encoder connected to the rotor shaft of the stepping motor, the rotor follows the command pulse, and the generated pulse of the encoder corresponds to the command pulse. A step-out detector that determines that a step-out state occurs due to a difference from an expected value is common.
[0003]
[Problems to be solved by the invention]
However, in such a conventional step-out detection device, the encoder is attached to the rotor shaft via a mechanical coupling, so that the overall structural size is increased, and the required specifications tend to be smaller and lighter. I couldn't answer. In addition, the simple structure of the stepping motor can be applied without restricting the installation location and the surrounding environment. However, by attaching the encoder, the application environment is restricted due to the precise structure of the encoder. The characteristic as a simple and robust positioning actuator inherent to the actuator is impaired.
The present invention was devised in view of the above points, and its object is to solve these drawbacks, as a simple and robust positioning actuator inherent in a stepping motor, which is small and light. It is an object of the present invention to provide a stepping motor step-out detection device that does not impair the characteristics of the stepping motor.
[0004]
[Means for Solving the Problems]
In other words, the means to achieve that purpose is
1) In claim 1,
The output of the current detector of each stator coil is input, and a measuring means for measuring the on / off time of the chopper-controlled control element for controlling the current so that the peak value of the coil current falls within a certain range is provided. The measuring means is provided with a determining means for determining the normal operation time and the step-out time, and the stepping motor is controlled by supplying the output signal of the determining means to the drive control circuit of the stepping motor.
[0006]
2 ) In claim 2 , the AC power supply voltage is converted to the secondary voltage of the AC / DC converter by an A / D converter so that the step-out can be detected without error with respect to fluctuations in the AC power supply voltage. The detector according to claim 1, wherein a detector for detection is provided to correct the step-out determination level.
In the unipolar chopper control stepping motor, the effect is that the magnetic resistance between the stator and the rotor is larger in the step-out state than in the normal operation, and the time constant of the stator coil, Tc = R / L decreases, and as a result, the rise and fall times of the excitation current of the stator coil are shortened, and the time during which the chopper current is on is shortened at the time of step-out compared to normal operation. The measured value of the on time of the chopper current is used to determine the difference between the normal operation and the step-out state.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a step-out detection apparatus in which the present invention is applied to 2-3 phase excitation chopper control of a 5-phase unipolar VR stepping motor will be described below with reference to FIGS.
1 is a chopper control circuit diagram with step-out detection added according to an embodiment of the present invention, FIG. 2 is a drive circuit block diagram for one phase of a stepping motor, and FIG. 3 is a current waveform and a high side. FIG. 4 is a timing diagram of the 5-phase 2-3 phase excitation system phase excitation pulse distribution circuit.
1 and 2, 1 is a phase excitation pulse distribution circuit, 2 is a current comparison circuit, 3 is an excitation current setting device, 4 is an AND logic circuit, 5 is a synchronization circuit, 6 is an oscillator, and 7 is a chopper-conduction pulse. Width measurement, comparison circuit, 8 step-out determination chopper-conduction pulse width memory, 10 control circuit, 11 stepping motor A-phase stator coil, 12 high-side drive transistor, 13 chopper switching transistor, Reference numerals 14 and 15 are reflux flywheel diodes, and 16 is a DCCT current detector.
[0009]
In the chopper control circuit having such a configuration, the setting signal of the stepping motor is a simple and highly accurate positioning actuator that can be controlled by a command pulse train Ps that sets the position by the number of pulses and the rotation speed by the frequency. The command pulse Ps is input and the phase excitation pulse distribution circuit 1 determines an order sequence for exciting the five-phase stator coils.
As shown in the timing chart of FIG. 4, the output of the phase excitation pulse distribution circuit 1 is the timing at which the A to E signals excite the A, B, C, D, and E phase stator coils. This signal is used as a base drive signal for the high-side transistor 12 shown in FIG.
[0010]
The chopper-controlled excitation current is detected by the current detector 16, and taking the A phase as an example, it is fed back to the current control circuit 2 as the feedback current Ia, and the excitation current setting circuit 3 shown in FIG. Compared with Ih and Ii, when the feedback current Ia increases, Ih is switched from on to off, and while the feedback current Ia decreases from Ih, control is performed to turn off to Ii.
This is a current on / off control circuit having a so-called hysteresis, and its output is ANDed with the drive signal Vh by the AND circuit 4 and output to the synchronizing circuit 5.
[0011]
In order to stabilize the operation of the synchronizing circuit 5, the on / off timing of the current is synchronized with the clock of the oscillator 6, the initial reset and the non-excitation free state control are performed by the synchronizing circuit 5, and this output VI is chopper-switching. This is the base drive signal for the transistor-13.
In this way, in the present invention, the output of the current detector of each stator coil is input to the device in which the unipolar chopper control is performed in this way, and the peak value of the coil current falls within a certain value range. A chopper for controlling the current is provided with a measuring means for measuring the ON / OFF time of the control element of the control, and provided with a judging means for judging the normal operation and the step-out time by the measuring means, and the output signal of the judging means is stepped The stepping motor is controlled by being supplied to the drive control circuit of the motor.
[0012]
That is, the step-out detector is obtained by adding a chopper-conduction pulse width measurement / comparison circuit 7 and a step-out determination chopper-conduction pulse width memory 8 as measurement means and determination means to the control circuit 10.
[0013]
The on / off timing relationship of the chopper-switching transistor 13 during normal operation is as follows from the excitation current setting Ii to Ih except for the first on-period T0 immediately after the phase change, as shown by the drive signal Vl in FIG. It turns on while Ia changes, and the on-time total of the chopper-switching transistor 13 during the phase excitation period is
ΣT = T1 + T2 + ... Tn (1)
Represented by
If the previous on-time total at the time of step-out is ΣTa, the relationship between ΣT and ΣTa is always
ΣT> ΣTa (2)
The relationship holds.
[0014]
For the time being, during normal operation, the mechanical work of the stepping motor is larger than that at the time of step-out, and as a result, much energy is supplied from the power source. As a result, the switching transistor of the chopper control The on-period has become larger.
When viewed from a magnetic circuit with a different view, the magnetoresistance between the rotor and the stator cannot be kept at the minimum position due to the step-out and becomes larger than during normal operation. The reactance is reduced, which means that the circuit time constant, Tc = R / L, becomes smaller. As a result, the excitation current rises sharply, the on-time of the chopper-switching transistor 13 becomes shorter, and ΣT> ΣTa is always satisfied. It will hold.
[0015]
Since the conduction time ΣT of the chopper-switching transistor 13 naturally varies depending on the rotation speed of the stepping motor, the drive period of the high-side transistor 12, the so-called phase excitation period is taken in, and the Vh signal is taken in. The limit data, ie, ΣTa , is written to the step-out determination chopper-conduction pulse width memory-8, the chopper-conduction pulse width measurement and comparison circuit 7 reads the data for Vh, ie, ΣTa , and inputs the Vl signal. By measuring the on-time, calculating ΣT and comparing it, if ΣT <ΣTa, it is determined that the step-out has occurred, and by outputting the output ER, it is possible to detect step-out in the entire rotation speed range. Notify the abnormality and perform necessary processing.
[0016]
Further, in the drive circuit in which the voltage between the converter outputs Vc-0 shown in FIG. 2 is in a proportional relationship with respect to the fluctuation of the AC power supply voltage, the chopper-conduction pulse width measurement and comparison circuit 7 shown in FIG. The voltage between Vc-0 is taken in by an A / D converter, the step-out determination data is corrected, and step-out detection of the entire specification power supply voltage range is made possible.
[0017]
【The invention's effect】
As described above, according to the present invention, the circuit for measuring the conduction time of the chopper transistor in the chopper-controlled stepping motor drive circuit, the memory for recording the value at the time of normal operation, By simply adding a circuit that compares the two, step-out detection can be reliably performed within the excitation period, and step-out detection can be performed without impairing the characteristics of the simple and robust positioning actuator of the stepping motor. At the same time, it can be made compact and lightweight, and is extremely useful in practice.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a chopper control circuit with step-out detection added according to an embodiment of the present invention.
FIG. 2 is a block diagram of a drive circuit for one phase of a stepping motor.
FIG. 3 is a diagram showing current waveforms and ON / OFF waveforms of high-side and low-side transistors.
FIG. 4 is a timing diagram of a 5-phase 2-3 phase excitation system phase excitation pulse distribution circuit;
[Explanation of symbols]
1 phase excitation pulse distribution circuit 2 current comparison circuit 3 excitation current setting device 4 AND logic circuit 5 synchronization circuit 6 oscillator 7 chopper-conduction pulse width measurement, comparison circuit 8 step-out judgment chopper-conduction pulse width memory-
10 control circuit 11 stepping motor A phase stator coil 12 high side drive transistor 13 chopper switching transistor
14, 15 Reflux flywheel diode 16 DCCT current detector

Claims (2)

In the stepper motor drive control circuit that chopper-controls the excitation current of the stator coil of the unipolar stepping motor, the chopper that controls the current so that the peak value of the coil current falls within a certain range by inputting the output of the current detector of each stator coil The measuring means for measuring the on-time total ΣT in the phase excitation period of the control element of the control , the memory in which the on-time total ΣTa at the time of step-out in the phase excitation period is written, and the ΣT by comparing the ΣT and ΣTa When a value exceeding ΣTa is large , a determination unit is provided that is normal, and the others are out of step, and the output signal of the determination unit is supplied to the drive control circuit of the stepping motor to control the stepping motor. Stepping motor step-out detection device characterized by the above.  A detector for detecting the AC power supply voltage with a secondary voltage of the AC / DC converter with an A / D converter is provided so that the step-out can be detected without error with respect to fluctuations in the AC power supply voltage. The stepping motor step-out detection device according to claim 1, wherein the step-out determination level is corrected.

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