JPH0759375A - Controller for sr motor driven by square wave - Google Patents

Abstract

PURPOSE:To stably decide a control command excellent in drive efficiency, in a controller for an SR motor driven by square waves. CONSTITUTION:An angle detection sensor 2 as a means for detecting the rotational angle of a rotor is attached to an SR motor 1 driven by square waves, and the angle signal from the angle sensor is inputted into a controller 3 together with the torque command signal from a torque command generator 4. The controller decides energization commands such as energization width, energization start angle, etc., with power source voltage as energization voltage without applying PWM in a great part of revolution range, based on those signals, and also widens the energization width, setting the energization voltage in low condition in advance in low revolution range. A power head driver 5 is operated by the output device inside the controller, according to the decided energization command value so as to drive a motor. Hereby, the switching loss of the power element inside a driver is reduced, and such effect that desired torque can be generated under high efficiency can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for a square wave drive SR motor.

[0002]

2. Description of the Related Art Generally, a square wave drive SR motor produces a magnetic field by passing an exciting current through an exciting winding, and the action of the magnetic field exerts a magnetism on a rotor, and a magnetic field generated between them is generated. The rotational torque is generated by utilizing the attractive force or the repulsive force generated in the protrusion of the rotor by the force. Therefore, when controlling the output, it suffices to control the exciting current corresponding to the exciting winding. However, in a square-wave drive SR motor, when a constant exciting current is applied to the exciting winding, the torque generated in the rotor is not constant and changes according to the rotation angle of the rotor. Particularly, when the protrusion of the rotor and the magnetic pole of the stator are close to each other, almost no output torque is generated, and the exciting current causes heat generation in the exciting winding. Further, the torque generated in the rotor is only partially proportional to the magnitude of the exciting current of the exciting winding. For example, the magnitude of the torque generated in the rotor sequentially shifts to the square region, the direct proportional region, and the saturation region as the exciting current increases.

Therefore, when a constant exciting current is applied to the exciting winding when a predetermined output is required, the exciting current is wastefully consumed and a torque ripple is generated in the rotor to stabilize the current. Not only the output torque cannot be obtained, but the driving efficiency is reduced. In addition, the inductance of the exciting winding increases as the number of rotations of the rotor increases, and the delay of the exciting current with respect to the current command value becomes significant. Therefore, in this case, torque cannot be generated in the rotor with good responsiveness.

On the other hand, as a control device of a square wave drive SR motor for improving drive efficiency and obtaining a stable output torque, there is one disclosed in Japanese Patent Laid-Open No. 3-143285. This is a control method for exciting current control by current pattern control in the low rotation range and compensating for phase delay due to the inductance of the excitation winding in the high rotation range.

In this method, a constant torque is generated in consideration of the torque characteristics peculiar to the SR motor, and the value of the exciting current, which eliminates unnecessary parts, is stored in advance in the storage means as a current pattern. When the rotation angle of the rotor of the SR motor is detected, a current pattern is read from the current pattern storage means in accordance with the detected value, and a current command value of the exciting current is given to the exciting means based on the read value. To be As a result, the exciting means controls the actual current by PWM or the like according to this current pattern. Further, when controlling in the high rotation range, the excitation current is delayed with respect to the current command value, but the switching phase for applying the excitation current is advanced from the low rotation range in advance so that the actual excitation winding This is intended to cover the delay of the exciting current due to the inductors and enable high efficiency and stable output in a wide range of rotation range.

[0006]

However, in such an SR motor control method, the exciting means controls the actual current by PWM or the like according to this current pattern in the low rotation range, so that the PWM carrier frequency is used. Frequently turns on and off, and the forward voltage drop of the switching element in the excitation means becomes large. Therefore, switching loss is increased and the efficiency of the motor as a whole is reduced.
Further, in the high rotation range, the inductance of the excitation winding changes with changes in the rotation speed of the rotor, so the delay of the excitation current changes with the rotation speed of the rotor and is not constant. However, since the lead phase is fixed, the delay of the exciting current of the exciting winding cannot be covered over the entire rotation range.

Since the cover of the delay of the exciting current due to the inductance of the exciting winding is good, and even if the exciting current rises at a good timing, the maximum value of the exciting current is still suppressed by PWM or the like. Similarly, the loss due to the switching element increases. That is, the conventional combination of the control of the exciting current by the current pattern control in the low rotation speed range and the control of the energization phase delay compensation in the high rotation speed range does not always maximize the driving efficiency of the motor.

Further, considering the characteristic that the exciting current changes with the fluctuation of the voltage peculiar to the SR motor, a desired motor output torque is not always obtained in the case of a power supply such as a battery whose output voltage changes with discharge. There was a problem that it did not exist. Therefore, in view of the above problems, the present invention provides a control device for an SR motor in which switching loss of a power element is reduced in a constantly efficient state, and a stable output can be obtained even when the power supply voltage fluctuates. It is an object of the present invention to provide a square wave drive SR motor that is used.

[0009]

Therefore, according to the present invention as set forth in claim 1, there is provided a rotation angle detecting means for detecting a rotation angle of a rotor of a square wave drive SR motor, and the rotation angle detecting means for detecting the rotation angle. In accordance with the detected value of the rotation angle of the rotor of the SR motor and the command value of the required torque, the SR motor is energized while the power supply voltage is still supplied to the SR motor in the normal medium rotation range, and the energization start angle, Control means for determining the energization width and outputting a control command, and the S based on the control command
It has a drive means for driving the R motor. The invention according to claim 4 is a rotation angle detecting means for detecting a rotation angle of a rotor of a square wave drive SR motor;
Voltage detection means for detecting the voltage of the drive power supply of the R motor,
The command value of the required torque is corrected by the voltage value detected by the voltage detecting means. According to a fifth aspect of the present invention, a rotation angle detecting means for detecting a rotation angle of a rotor of a square wave drive SR motor, a voltage detecting means for detecting a voltage of a drive power source of the SR motor, and the voltage detecting means. Of the SR motor, the detected value of the rotation angle of the rotor of the SR motor by the rotation angle detection means, and the command value of the required torque, the energization voltage of the SR motor, the energization start angle, and the energization. It is characterized by having a control means for determining the width and outputting a control command, and a drive means for driving the SR motor based on the control command.

[0010]

According to the first aspect of the invention, in the control means, the energization command to the SR motor is generated in most of the rotation range based on the rotation speed of the SR motor and the required torque command value. Since it is determined that the voltage of the power source is supplied as it is without being applied, the switching loss of the power element or the like used in the drive means of the SR motor is reduced and the drive efficiency is optimized.

In the emergency low speed range, the higher the command value of the required torque, the lower the energizing voltage to the SR motor and the wider the energizing width. Of the exciting current is slowed and the energization width is increased to compensate the torque, thereby preventing the exciting current from becoming an overcurrent due to the reduction of the counter electromotive voltage in the exciting winding. This makes it possible to prevent damage to the power element and the like due to overcurrent. In the emergency high rotation speed range, when the energization start angle is set to be earlier as the command value of the required torque is higher, the energization voltage, the energization start angle, and the energization width are changed as three control parameters. Torque can be generated under driving efficiency.

In the invention according to claim 4, since the power supply voltage is detected and the torque command value is corrected by the detected voltage value, the output is not affected by the fluctuation of the power supply voltage, and the output is highly efficient and stable. Output torque is obtained. In the invention according to claim 5, since the detected voltage value of the power source is further added to the parameter for determining the energization command, the actual driving state of the SR motor is reflected, and the driving efficiency is improved and stable output is obtained with high accuracy. To be

[0013]

FIG. 1 shows a first embodiment of the present invention. An angle detection sensor 2 is attached to the square wave drive SR motor 1 as a rotation angle detection means of the rotor, and an angle signal from the angle sensor is input to the control unit 3 together with a torque command signal from the torque command generation unit 4. The control unit determines the energization command such as the energization start angle and the energization width to the SR motor based on these signals. The output device in the control unit operates the power head drive unit 5 in accordance with the determined energization command value, and the power from the power supply 7 is supplied to the excitation winding of the SR motor according to the operation of the power head drive unit 5.

Here, the voltage applied to the excitation winding of the SR motor refers to the effective voltage after the power supply voltage is subjected to PWM, for example. As shown in FIG. 2, the energization angle and the energization width are the salient poles of the rotor with respect to the center point B of the stator when the magnetic pole C of the stator is energized while the rotor is rotating in the clockwise direction. The angle of the central point A is the energization start angle, and the angle at which the point A moves from the energization start to the end is the energization width.

To drive a square wave drive SR motor,
It is highly efficient to keep the voltage applied to the motor high and to control the torque by using the time for applying current to the winding, that is, the current width. Further, as described above, it is necessary to reduce the switching loss in order to improve the driving efficiency of the motor. For this reason, the energized voltage is maintained at the power supply voltage value without applying PWM or the like in most of the rotation range. The output is controlled by the current value of the excitation winding of the motor, that is, the energization width and energization start angle. However, in the low rotation speed range, the back electromotive force of the excitation winding is small, so if the same voltage as in the normal rotation speed is applied, the phase current flowing through the winding rises rapidly, and there is a problem that an overcurrent is likely to occur. .

That is, if the drive circuit when the SR motor 1 has three magnetic poles has the configuration shown in FIG.
The voltage equation of the phase is as shown in Equation 1.

[Equation 1] However, V: conduction voltage R: excitation winding resistance i: phase current L: self-inductance M: mutual inductance. By substituting dθ / dt = ω into Equation 1, Equation 2 is obtained.

[Equation 2] Where θ is the rotation angle of the rotor, and ω is the rotation speed of the rotor.

When the rotation speed is low, that is, when ω is small in Equation 2, if the energized voltage V is constant, the time derivative term on the right side becomes large and the time change amount such as the rise or fall of the phase current i becomes large. Therefore, as shown in FIG. 4, an overcurrent is likely to occur. That is, when energizing at a high voltage in a rotation range where the back electromotive force is not so large, the peak value of the phase current easily exceeds the current capacity of the power element of the power head driving unit. Naturally, in this rotation range, if the energization voltage is increased to increase the output torque, the same inconvenience as described above occurs. For this reason, it is necessary to reduce the voltage to be applied in the low rotation speed range to slow down the rise of the phase current as shown in FIG.

Since the SR motor has the characteristics shown in FIG. 6, the efficiency has a maximum value at a certain energization start angle, and the torque has a maximum value at an angle at which the energization start is advanced. The value of the energization start angle that maximizes the efficiency changes depending on the energization width and the number of revolutions, and takes a larger value as the energization width is wider and the number of revolutions is higher. Therefore, high load,
As the rotation speed increases, it is more efficient to start energization earlier. The wider the energization width, the longer the current rise time, so the effective current value increases. Further, the energization start angle is such that a larger amount of current flows when the energization is started than before the angle at which the magnetic poles of the stator and the salient poles of the rotor are overlapped with each other, and the effective current value rises to increase the torque.

As the energization start angle is advanced, the torque,
The efficiency increases, but if it goes too far, it decreases. Therefore, it is necessary to control to an optimum value. Then, according to the experiment, it was found that the drive efficiency of the motor was optimum when the energizing voltage was changed in the form as shown in FIG. The energization width and the energization start angle are controlled according to FIGS. 8 and 9. From these, it can be seen that, for a constant output torque, the energization voltage to the motor, the energization width, and the energization start angle change depending on the level of the rotation speed. Further, in the low rotation speed region, since the counter electromotive force is small, the energization voltage can be decreased, the rising of the exciting current can be delayed, and the energization width can be widened to control the output torque.

In order to prevent an overcurrent in the low speed range, it is possible to make the energization voltage sufficiently low in advance and to control the torque by the energization phase. In the SR motor, the higher the energization voltage, the better the efficiency. It's not a good idea.

The control section 3 stores in the internal memory the information on the energization voltage, energization width and energization start angle shown in FIGS. 7, 8 and 9 obtained by these experiments. This information may be in the form of a map with the output torque and the number of revolutions divided into appropriate sections as parameters. The stored energization voltage, energization width, and energization start angle are read and output from the rotation speed detected by the angle sensor and the torque signal from the torque command generator.

As described above, in the present embodiment, without applying PWM in most of the rotation range, the voltage of the power source is directly applied to the motor and the maximum value of the current is controlled by the energization width and energization start angle of the motor. As a result, driving efficiency is improved. In the low rotation speed range, PWM is applied to squeeze the energization voltage, and the energization width is expanded by the amount that compensates for it. It is possible to prevent the peak value of the winding current due to the rising from exceeding the current capacity of the power head portion or the like. Then, since the energization start angle is advanced in the high rotation range, the motor winding current can be passed at an efficient timing. As a result, driving efficiency is improved without wasting power in a wide range.

FIG. 10 shows a second embodiment. In this embodiment, a current peak value detection circuit 8 for the exciting current generated by the exciting winding is further provided in the first embodiment shown in FIG. The peak value of the excitation current generated in the excitation winding detected by the current peak value detection circuit is input to the control unit 13 together with the angle signal from the angle sensor 2 and the torque command signal from the torque command generation unit 4. Other configurations are first
Is the same as the embodiment described above.

Next, the determination of the energization command to the SR motor in the control unit 13 will be described. As described above, the higher the energizing voltage of the SR motor, the better the efficiency. Therefore, SR
It is necessary to supply a high voltage power to the motor.
However, in this case, since the inductance of the exciting winding is small in the low rotation range, the exciting current is likely to become an overcurrent, which causes heat generation of the exciting winding and a decrease in drive efficiency.
Therefore, in order to obtain high driving efficiency, it is necessary to control so as not to cause an overcurrent under a high voltage. For this reason, the calculation is performed in advance so that overcurrent does not occur in correspondence with the energization voltage, energization width, and torque for each rotation speed.
The three-dimensional map created as a result as shown in FIG. 11 is stored in the internal memory provided in the control unit.

Then, the required torque output from the torque command generator 4 is compared with the actually output torque value. In order to know the torque value actually output, a torque sensor may be provided on the output shaft portion of the motor, or the torque value may be calculated from the amount of change in the rotational speed of the rotor. When the required torque is larger, that is, when the generated torque is further increased, the three-dimensional map as shown in FIG. 11 stored in the internal memory is read according to the detected value of the rotational speed at this time. Be done. Based on this figure, the conduction voltage and the conduction width corresponding to the current signal from the current peak value detection circuit are determined. When there is a margin with respect to the current capacity of the power element, the energizing voltage is increased as indicated by A → B in FIG. 11 to increase the exciting current and increase the torque. This is because the higher the energizing voltage, the better the efficiency due to the characteristics of the SR motor. When the current capacity of the power element is exceeded, the energizing voltage is dropped as shown in B → C in FIG. 11 in order to suppress the peak value, the rising is delayed, and the energizing width is widened to allow current to flow. Increase.

The flow of the above control in the control unit is as shown in FIG. First, in step 100, the torque command value from the torque command generator 4 and the detected value of the rotor angle sensor 2 are read into the controller, and then the actual output torque is calculated based on the detected value of the rotation angle. The calculated output torque and the required torque are compared, and it is checked whether the required torque is larger. If the determination here is YES, in step 101, the peak value Ip of the exciting current is read from the current peak value detection circuit. Then, after this, in step 102, it is compared whether the power element current capacity is smaller than the peak value of the exciting current.

If the result of the determination is NO, then in step 103, a command for increasing the voltage applied to the motor is determined. If the decision result in the step 102 is YES, a command to reduce the energizing voltage is decided in a step 104. Then, in step 105, a command to increase the energization width is determined.

When the result of the determination in step 100 is NO, the peak value Ip of the exciting current is read from the current peak value detection circuit in step 201. Step 202
At, it is determined whether the power element current capacity is smaller than the peak value of the exciting current. If the result of the determination is YES, then in step 203, an instruction to reduce the voltage applied to the motor is determined. When the determined result is NO, a command to increase the energization voltage to the motor is determined in step 204. Then, in step 205, a command to reduce the energization width to the motor is determined.

This embodiment is constructed as described above. Since the peak value of the exciting current is detected and the energization width and the energizing voltage are determined based on the detected values, the peak value of the exciting current is suppressed. Overcurrent is unlikely to occur even in the high load region, and the same effect as that of the high load can be obtained in the low rotation region as well, and control can be performed under a high energizing voltage without always causing overcurrent. This improves the driving efficiency of the SR motor over a wide range.

FIG. 13 shows a third embodiment. In this embodiment, the torque command is corrected by the power supply voltage. In the square wave drive SR motor, the influence of the power supply voltage on the motor output is considerably large. That is, the optimum value of the control parameter changes according to the fluctuation of the power supply voltage. If a power supply device in which the output voltage does not change depending on the load is used, the optimum value of the control parameter at a certain constant voltage value can be obtained, and highly efficient driving can be performed. Therefore, the power supply voltage is set to PW
Although it is possible to change it by M or the like, in the control method of each of the above-described embodiments, most of the operating range does not apply PWM, that is, the duty ratio is 100%, so that the energization voltage can be lowered. , You can't raise it. Generally, in a battery, the output voltage decreases as the discharge progresses, and the energization voltage to the motor decreases, so that the torque generated by the motor decreases. Therefore, the desired torque cannot be obtained.

For this reason, in this embodiment, the power supply voltage detection circuit 6 is provided, and the power supply voltage detected by the power supply voltage detection circuit 6 together with the angle signal from the angle sensor 2 and the torque command signal from the torque command generator 4 are detected. It is input to the control unit 23. The other structure is the same as that of the first embodiment. Therefore, the relationship between the torque and the power supply voltage obtained by the experiment as shown in FIG. 14 is stored in advance in the internal memory of the control unit, and this is stored according to the signal from the torque command generation unit and the detected value of the power supply voltage. Read out and correct the torque command based on the power supply voltage change. If the power supply voltage decreases, the correction value for the torque command increases, and the desired torque value can be output.

As described above, in this embodiment, the torque command is corrected by detecting the power supply voltage, so that an output according to the torque command is obtained and the drive performance of the SR motor is improved. Note that this correction value may be stored in advance as a two-dimensional map in the internal memory of the control unit, and may be obtained by a certain method during driving.

Next, a fourth embodiment will be described. In this embodiment, torque changes due to fluctuations in the power supply voltage are corrected by control parameters such as energization voltage, energization start angle and energization width. This correction is performed by the control unit, and other configurations are the same as those in the first embodiment.

The control unit has an internal memory, and the optimum values of the energization voltage, energization start angle, and energization width are calculated in advance in correspondence with the rotation speed and torque divided into appropriate sections for each power supply voltage. The results are stored as a three-dimensional map as shown in FIGS. FIG. 15 shows the relationship between the energizing voltage, the torque, and the rotation speed when the power supply voltage changes. FIG. 16 shows the relationship between the energization voltage, the torque, and the energization start angle when the power supply voltage changes. FIG. 17 shows the relationship between the energization voltage, the torque, and the energization width when the power supply voltage changes.

When the detection value of the angle sensor is input to the control unit, the actual rotation speed is calculated by the arithmetic unit in the control unit based on the detection value of the angle sensor, and based on the calculation value of the rotation speed, The energization commands such as the energization voltage, the energization start angle, and the energization width are read according to the detected power supply voltage value and the torque command value, and are output to the power head drive unit.

.. This embodiment is configured as described above, and when determining the energization command, the energization command values such as the energization voltage, the energization start angle, and the energization width that are precalculated with the torque, the rotation speed, and the power supply voltage as parameters are stored in the internal memory. The optimum drive command is determined because the division pattern of each power supply voltage is selected for the required torque.
As a result, the output does not change even if the voltage of the power supply fluctuates, and the driving efficiency is maintained high.

FIG. 17 shows a modification of the power supply voltage detection in the third and fourth embodiments. This is one in which a power supply voltage is estimated and calculated. A current sensor is provided at the output part of the power supply, and the power supply voltage is estimated by the control part using this current value. When a secondary battery is used as a driving power source for a motor, the output voltage of the battery generally decreases as the discharge progresses. Moreover, the output voltage also decreases depending on the magnitude of the discharge current. The output voltage can be estimated by detecting the depth of discharge and the discharge current. First, as for the motor input power, the actual power is calculated by combining the motor output obtained from the torque command value and the motor rotation speed as a and the corresponding efficiency with the efficiency map prepared in advance as b. . Then, the depth of discharge is estimated by time-integrating the output power of the battery, that is, the input power to the motor as indicated by c. After that, the output voltage of the battery is estimated from the current value detected by the current sensor as in d and the previous discharge depth based on the discharge characteristic diagram.

[0038]

As described above, the square wave drive S of the present invention is used.
In the control means of the R motor, the voltage applied to the SR motor is set so that the voltage of the power supply is applied as it is without applying PWM in most rotation regions, so that the switching loss is reduced. Also, in the low speed range, overcurrent can be prevented by lowering the energizing voltage, and
Since the energization start angle is advanced in the high rotation range, the motor winding current can be passed at an efficient timing. As a result, driving efficiency is improved without wasting power in a wide range. Furthermore, since the power supply voltage is detected and the detected command value is used to correct the torque command value or determine the energization command, the drive efficiency can be improved and the desired torque can be generated accurately even if the power supply voltage changes. The effect that it can be obtained is obtained.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of an energization start angle.

FIG. 3 is a drive circuit diagram of a motor.

FIG. 4 is an explanatory diagram of phase current overcurrent.

FIG. 5 is a diagram illustrating energization control for preventing overcurrent.

FIG. 6 is a characteristic explanatory diagram of an SR motor.

FIG. 7 is a relational diagram of energization voltage, torque, and rotation speed.

FIG. 8 is a diagram showing the relationship between the energization width, the torque, and the rotation speed.

FIG. 9 is a diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 10 is a diagram showing the relationship between the energization voltage, the energization width, and the torque.

FIG. 11 is a three-dimensional map of energization voltage.

FIG. 12 is a flow chart showing a flow of determining a conduction voltage and a conduction width.

FIG. 13 is a diagram showing a configuration of a third exemplary embodiment of the present invention.

FIG. 14 is a diagram showing the relationship between output torque and power supply voltage.

FIG. 15 is a diagram showing a three-dimensional map of a duty ratio.

FIG. 16 is a diagram showing a three-dimensional map of energization start angles.

FIG. 17 is a diagram showing a three-dimensional map of energization width.

FIG. 18 is an explanatory diagram showing a flow of estimation and calculation of a power supply voltage value.

[Explanation of symbols]

 1 SR Motor 2 Angle Sensor 3, 13, 23 Control Section 4 Torque Command Generation Section 5 Power Head Drive Section 6 Voltage Detection Circuit 7 Power Supply 8 Phase Current Peak Value Detection Circuit

Claims (5)

[Claims] 1. A rotation angle detecting means for detecting a rotation angle of a rotor of a square wave drive SR motor, and a detected value of a rotation angle of the rotor of the SR motor by the rotation angle detecting means and a required torque. Control means for energizing the SR motor with the power supply voltage as it is in the medium-revolution range of normal use in accordance with the command value, determining the energization start angle and energization width, and outputting a control command; Based on S
A control device for an SR motor of a square wave drive, comprising: a drive means for driving an R motor. 2. The control means determines to increase the energization width by lowering the energization voltage to the SR motor as the command value of the required torque is higher in the emergency low rotation speed range. A control device for a square wave drive SR motor according to claim 1. 3. The SR motor control device according to claim 1, wherein the control means determines such that the energization start angle is advanced as the command value of the required torque is higher in the emergency high rotation range. . 4. A rotation angle detection means for detecting a rotation angle of a rotor of a square wave drive SR motor, a voltage detection means for detecting a voltage of a drive power source of the SR motor, and the SR motor by the rotation angle detection means. In accordance with the detected value of the rotation angle of the rotor and the command value of the required torque, the SR motor is energized with the power supply voltage as it is in the normal medium rotation range, and the energization start angle and energization width And a drive unit for driving the SR motor based on the control command, the control unit being requested by the voltage value detected by the voltage detection unit. A square-wave drive SR motor control device for correcting a command value of torque. 5. A rotation angle detection means for detecting a rotation angle of a rotor of a square wave drive SR motor, a voltage detection means for detecting a voltage of a drive power source for the SR motor, and a detection value of the voltage detection means. The SR by the rotation angle detecting means
The energization voltage of the SR motor according to the detected value of the rotation angle of the rotor of the motor and the command value of the required torque;
An SR motor control device comprising: a control unit that determines a power distribution start angle and a power distribution width and outputs a control command; and a drive unit that drives the SR motor based on the control command.