JP4054426B2 - Stepping motor step-out detection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a step-out detection method for a stepping motor.
[0002]
[Prior art]
Conventionally, in a drive actuator mechanism using a stepping motor, as a method for detecting whether or not the stepping motor has stepped out, a rotation detector such as a rotary encoder is attached to the stepping motor as shown in FIG. Is compared with the speed command pulse applied to the stepping motor, and the comparison result is input to the determination circuit. The determination circuit compares the signal output from the comparison circuit with the set value, and steps out. It was output as a step-out detection signal.
[0003]
[Problems to be solved by the invention]
However, in the above-described step-out detection method, since it is necessary to attach a rotation detector to the stepping motor, there is a problem that the component cost, assembly cost, etc. increase, and as a result of attaching the rotation detector, a feedback circuit is provided as a system. Therefore, there is a problem in that the simplicity of the open loop control circuit, which is the original characteristic of the stepping motor drive circuit, is hindered.
[0004]
Further, troubles caused by the rotation detector may occur, and there is a risk of being troubled by a decrease in reliability and isolation at the time of failure.
[0005]
An object of the present invention is to solve the above-mentioned problems and to provide a low-cost and highly reliable step-out detection method for a stepping motor that does not require a rotation detector for monitoring the rotation of the stepping motor.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the stepping motor step-out detection method according to the present invention provides a motor current in a stepping motor driver that drives the stepping motor when a stepping motor drives a load whose driving conditions are known. Based on the voltage value obtained by converting the waveform into a rectangular wave signal and the rectangular wave signal into a voltage signal, the reference voltage value is set in advance from the normal operation and when the step-out is forced. In determining the occurrence of step-out by determining the measured voltage value during normal operation and comparing the determined measured voltage value with the reference voltage value, the measured voltage value is a region where the stepping motor operates at a constant speed. Of the motor current waveform generated in step 1, the waveform at both ends of the detection resistor must be converted into a voltage generated as a low level time of 0V or less. The lower limit value of the ripple of the voltage signal converted from the rectangular wave signal becomes smaller as the low level time of the rectangular wave signal obtained as the measured voltage value becomes longer, and the measured voltage The presence or absence of occurrence of step-out is determined by comparing the lower limit value of the voltage signal of the value with the reference voltage value .
[0007]
It is preferable to determine whether or not the stepping motor has stepped out during the constant speed operation of the stepping motor.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram for explaining a stepping motor step-out detection method according to the present invention. A motor driving current waveform (hereinafter referred to as a motor current waveform) obtained from a stepping motor driver 2 driving the stepping motor 1 is shown in FIG. Converts to a rectangular wave signal, compares the measured voltage value obtained by converting the converted rectangular wave signal into a DC voltage signal, and a reference voltage value, without using a rotation detector such as a rotary encoder A step-out detection signal is obtained.
[0009]
As shown in FIG. 2, a stepping motor driver (hereinafter referred to as a motor driver) 2 drives a stepping motor by a bipolar chopper method, and detects the waveform at both ends of the current detection resistor Rs of the motor driver 2 for step-out detection. A motor current waveform that can be used as a motor current waveform and can be observed at both ends of the current detection resistor Rs is shown in FIGS.
[0010]
FIG. 3A shows the motor current waveform during normal driving, and FIG. 4A shows the motor current waveform during step-out.
[0011]
A motor current waveform during normal operation is captured in advance with a load having known driving conditions (how much weight is driven at what speed) connected to the stepping motor. In this motor current waveform, the waveform at both ends of the current detection resistor Rs of the motor driver 2 (only the power stage for one phase is displayed) is used for step-out detection, and can be observed at both ends of the current detection resistor Rs. The motor current waveform is shown in FIG. The captured motor current waveform is converted into a rectangular wave signal by a current waveform / rectangular wave conversion circuit (hereinafter referred to as a rectangular wave conversion circuit) 3. This rectangular wave conversion circuit 3 is composed of a comparator, which compares the motor current waveform with 0 V, converts the motor current waveform on the + side from 0 V into a rectangular wave and outputs the rectangular wave. The motor current waveform input to the wave conversion circuit 3 is converted into a rectangular wave signal and output as shown in FIG. The rectangular wave signal is converted into a DC voltage signal by a rectangular wave / voltage value conversion circuit (hereinafter referred to as a voltage value conversion circuit) 4. The voltage value conversion circuit 4 is constituted by an integration circuit composed of a resistor R1 and a capacitor C1, and the input rectangular wave signal is converted into a DC voltage signal including a ripple and output (see FIG. 3C). ).
[0012]
Next, an external force other than the normal load is applied to the load connected to the stepping motor to forcibly generate step-out. When the step-out occurs, the position of the rotor of the stepping motor changes compared to the normal driving, and the inductance value changes accordingly. Therefore, a change appears in the rising portion of the motor current waveform compared to the normal driving (FIG. 4A). reference).
[0013]
This motor current waveform is input to the rectangular wave conversion circuit 3 to convert it into a rectangular wave signal (see FIG. 4B), and the converted rectangular wave signal is further input to the voltage value conversion circuit 4 to generate a direct current signal. It converts into a voltage signal (refer FIG.4 (c)).
[0014]
Note that when setting the integration circuit constants (values of the resistor R1 and the capacitor C1) of the voltage value conversion circuit 4, the lower limit value V ₁ of the voltage signal ripple at the normal time and the ripple of the voltage signal at the time of the step-out are set. it may be set so that the difference in the lower limit value V ₂ occurs. Then, a reference voltage value V _F is obtained from the voltage signal at the normal time and the voltage signal at the time of step-out. This reference voltage value V _F must be set to be smaller than the lower limit value V ₁ of the ripple of the voltage signal at the normal time and larger than the lower limit value V ₂ of the ripple of the voltage signal at the time of step-out. That is, the value of the reference voltage value V _F may be set as shown in Expression (1).
V ₁ > V _F > V ₂ (1)
[0015]
The rectangular wave signal output from the rectangular wave conversion circuit 3 when step-out occurs reflects the characteristics of the motor current waveform, and the low-level time t of the rectangular wave signal during normal driving (see FIG. 3B). Since the low-level time t ₂ (see FIG. 4B) of the rectangular wave signal at the time of step-out becomes longer than the lower limit value of the ripple of the voltage signal converted by the voltage value conversion circuit 4, the normal voltage It becomes lower than the lower limit value of the ripple of the signal (see FIG. 4C).
[0016]
Then, the output of the voltage value conversion circuit 4 is input to the determination circuit 5 to determine whether or not step-out has occurred. The determination circuit 5 is constituted by a comparator, the measured voltage value V _m of the input voltage signal is a reference voltage V _F and the comparator described above, the input measured voltage value V _m is lower than the reference voltage value V _F In the case (see FIG. 4C), the signal is output as a rectangular wave for a time lower than the reference voltage value V _F (see FIG. 4D). At that time, it is determined that a step-out has occurred, A rectangular wave can be used as a step-out detection signal.
[0017]
During normal operation, the lower limit value V _{1 of the} ripple included in the voltage signal is higher than the reference voltage value V _F as shown in FIG. 3C, and therefore the output of the determination circuit 5 is as shown in FIG. In addition, the step-out detection signal is not output at 0V.
[0018]
According to the stepping motor step-out detection method described above, paying attention to the characteristics of the motor current waveform at the time of normal driving and step-out occurrence, a load having a known driving condition is connected to the stepping motor in advance and predetermined driving is performed. When the motor is operated normally under the conditions, and when the step-out occurs by applying an external force other than the normal load, the motor current waveform is converted into a rectangular wave signal, and further converted into a DC voltage signal, The reference voltage value V _F is set from the lower limit values V ₁ and V _{2 of the} ripple included in the voltage signal during normal operation and step-out, and the motor current waveform is always observed during normal operation. as the comparison with the reference voltage value V _F set the measured voltage value V _m of the voltage signal in advance, when the measured voltage value V _m (the lower limit of the ripple) is below than the reference voltage value V _F is determined that step-out occurs Out of step Can be easily determined without using a rotation detector such as a rotary encoder.
[0019]
In the step-out detection method described above, the case where the bipolar chopper drive circuit is used as the driver circuit for driving the stepping motor has been described. However, the drive circuit is not limited to the bipolar chopper drive circuit, and the unipolar chopper drive circuit is used. It does not matter.
[0020]
Further, a unipolar constant voltage drive circuit or a bipolar constant voltage drive circuit may be used as long as the motor current can be detected.
[0021]
Next, a step-out detection method when the stepping motor is driven at high speed will be described.
[0022]
FIG. 5 shows the relationship between time and speed in the case of trapezoidal driving as an example of driving the stepping motor at high speed. The stepping motor speed command pulse is transmitted in the acceleration area, the high speed area, and the deceleration area. Although controlled, the current waveform detected by the current detection resistor Rs changes every moment in the acceleration region and the deceleration region, and the comparator circuit (determination circuit 5) with the reference voltage value V _F becomes unstable. Therefore, a detection method for detecting only occurrence of step-out in a high speed region (during constant speed operation) where the speed is constant will be described (see FIG. 6).
[0023]
In this case, when setting the reference voltage value V _F , the motor current waveform during normal driving in the high speed region is observed, and this motor current waveform (see FIG. 7A) is converted into a rectangular wave by the rectangular wave conversion circuit 3. The signal is converted into a signal (see FIG. 7B), and further converted into a DC voltage signal (see FIG. 7C) by the voltage value conversion circuit 4. Next, a motor current waveform is observed when an external force is applied to the load being driven in the high speed region to forcibly cause a step-out, and the motor current waveform (see FIG. 8A) is converted into the rectangular wave conversion circuit 3. Is converted into a rectangular wave signal (see FIG. 8B), and further converted into a DC voltage signal (see FIG. 8C) by the voltage value conversion circuit 4. Then, the reference voltage is calculated from the lower limit value of the ripple V ₁ (see FIG. 7C) of the normal voltage signal in the high-speed region and the ripple V ₂ (see FIG. 8C) of the voltage signal when the step-out occurs. The value V _F may be set. Then, the reference voltage value V _F as a criterion of the determination circuit 5.
[0024]
The output of the determination circuit 5 is input to the AND gate 6, and the output obtained by ANDing the enable signal that is the output of the constant speed detection circuit 7 may be determined as a step-out detection signal. The constant velocity detection circuit 7 converts the velocity command pulse (CW · CCW signal) input to the driver circuit DC voltage F / V converter 8, a comparator and a converted DC voltage V _h and the reference value V _CF 9, the enable signal for enabling the AND circuit 6 may be output when the DC voltage V _h output from the F / V converter 7 becomes equal to the reference value V _CF. The reference value V _CF may be obtained by measuring in advance a DC voltage value obtained from a speed command pulse when the stepping motor is driven at a high speed, and using the DC voltage value obtained by the measurement as a reference value.
[0025]
The measured voltage value V _m of the voltage signal obtained from the motor current waveform during normal driving is compared with the set reference voltage value V _p, and the measured voltage value V _m (ripple lower limit) is the reference voltage value V _p. When it falls below, a step-out signal is output from the determination circuit 5 as a step-out signal (see FIG. 8D). This step-out signal is input to the AND gate 6, and an output obtained by ANDing the enable signal (see FIG. 8E) which is the output of the constant speed detection circuit 7 is used as the step-out detection signal (FIG. It may be determined as f).
[0026]
Since a step-out signal is not output during normal driving (see FIG. 7D), a step-out detection signal is not output even if an enable signal (see FIG. 7E) is output (FIG. 7). (Refer to (f)).
[0027]
As a result, the motor current waveform is monitored only when the stepping motor is driven in the high speed range (during constant speed operation), and the presence or absence of occurrence of step-out in the constant speed range can be detected with a simple circuit configuration. Can be detected.
[0028]
The constant speed detection circuit may use an operation monitor signal indicating that the output clock signal is being accelerated or decelerated, which is prepared in a recent motor control LSI.
[0029]
【The invention's effect】
According to the present invention, among the current waveforms generated in the constant speed region of the stepping motor, a voltage generated as a low level time of 0 V or less is converted into a rectangular wave signal, and the rectangular wave signal is converted into a voltage signal. using voltage value, since it is Re comparing the lower limit value of the voltage signal from the reference value set in advance and the measured voltage value, it is not necessary to use a waveform voltage generated by the above 0V current waveform, constant It is possible to detect the presence or absence of stable step-out in the speed region . Therefore, it is possible not only to easily determine the occurrence of out-of-step occurrence as in the prior art without using a rotation detector such as a rotary encoder, but also to reduce the parts cost and assembly cost, as well as the circuit configuration. Effects such as simplification and improved workability during maintenance can be brought about. In addition, since the change in the motor current waveform is directly monitored, when a step-out occurs, it can be detected in a short time.
[0030]
Further , even when a stepping motor such as a trapezoidal drive or an S-shaped drive is operated at a high speed, a simple and low-cost step-out detection method can be provided within a constant speed region.
[Brief description of the drawings]
FIG. 1 is a block diagram for explaining a stepping motor step-out detecting method according to the present invention. FIG. 2 is a circuit diagram showing an example of a circuit for explaining a stepping motor step-out detecting method. d) is a time chart diagram during normal operation. [FIG. 4] (a) to (d) are time chart diagrams when a step-out occurs. [FIG. 5] A drive pattern diagram during high-speed operation of the stepping motor. FIG. 7 is a circuit diagram illustrating an example of a circuit for explaining another example of the step-out detection method of the present invention. FIGS. 7A to 7F are time chart diagrams of other examples during normal operation. FIG. FIG. 9F is a time chart when another step-out occurs. FIG. 9 is a block diagram illustrating a conventional stepping motor step-out detection method.
1 Stepping Motor 2 Motor Driver 3 Rectangular Wave Conversion Circuit 4 Voltage Value Conversion Circuit 5 Judgment Circuit 7 Constant Speed Detection Circuit V _F Reference Voltage Value V _m Measurement Voltage Value

Claims (2)

When a stepping motor is used to drive a load whose driving conditions are known, the motor current waveform in the stepping motor driver that drives the stepping motor is converted into a rectangular wave signal, and the rectangular wave signal is converted into a voltage signal. Based on the measured voltage value, the reference voltage value is set in advance from the normal operation and when the step-out occurs forcibly, and the measured voltage value in the normal operation is obtained. The obtained measured voltage value and the reference voltage value In determining whether or not a step-out has occurred by comparing the measured voltage value with the measured voltage value of the motor current waveform generated in the region where the stepping motor operates at a constant speed , the waveform at both ends of the detection resistor is 0 V or less. And a value based on a rectangular wave signal converted with a waveform generated as a voltage as a low level time, and a rectangle obtained as the measured voltage value As the low level time of the wave signal is longer, the lower limit of the ripple of the voltage signal converted from the rectangular wave signal becomes smaller, and step-out occurs by comparing the lower limit of the voltage signal of the measured voltage value with the reference voltage value. A step-out detection method for a stepping motor, characterized by determining the presence or absence of the stepping motor.   Whether or not the stepping motor has stepped out is determined by setting the reference voltage value to be smaller than the lower limit value of the voltage signal at the normal time and larger than the lower limit value of the voltage signal at the time of stepping out, and the measured voltage value is the reference voltage value. 2. The stepping motor step-out detection method according to claim 1, wherein the determination is made when the voltage value falls below the voltage value.

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