JP3764513B2 - Method and apparatus for controlling current profile in an SRM - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a switching reaction motor (abbreviated herein as "SRM"), and more particularly to reduce motor noise by controlling or manipulating a current profile for the motor. It relates to a method and apparatus.
[0002]
[Prior art and problems to be solved by the invention]
Switching reaction motors, or SRMs, are well known in the art. One problem with operating this type of motor is noise. As described in U.S. Patent Application No. 175,268 by the inventor of the present application, such noise is generated as one source in the phase winding of the motor as each phase is switched at the end of the cycle. Caused by the dissipation of current. When the motor is switched from one phase to another, about 30% of the energy supplied to the phase winding is attenuated while the phase winding is energized. As described in the above US patent application, a portion of this energy is recovered or dissipated using a storage capacitor.
[0003]
In general, the main cause of motor noise is a sudden change in the normal force acting between the stator and rotor of the motor. Noise is also particularly severe when such abrupt changes occur at the position of maximum deformation of the motor cycle. US Pat. No. 5,239,217, filed by the inventor of the present application, describes a phenomenon called “elliptical deformation”. This phenomenon is a state in which the substantially circular rotor and stator of the motor are deformed into an oval shape by the force generated when the rotor pole and the stator pole are aligned with each other. The above-mentioned US patent applications and US patents describe methods for reducing such elliptical deformation forces.
[0004]
The methods described in the above-mentioned US patent applications and US patents are effective in reducing motor noise, but other methods of further reducing motor noise are also important. One such method is to control the current profile of each phase of the motor. In one control method where the current is controlled to reduce torque, various look-up tables and schedules are used to achieve the control (see US Pat. No. 4,868,477). It is also known to control the current profile by increasing the phase length and thereby increasing the phase dwell time (US Pat. No. 4,253,053). The third method is a paper by S. Chan and HR Bolton titled “Performance Enhancement of Single-phase Switched Reluctance Motor by DC Link Voltage Boosting” (IEEE Proceedings-B, Volume 140, paper number 5, September 1993). It is described in. In this paper, current is supplied to the phase and the current is removed faster than normal by using the boost voltage at the beginning of the end of the later phase. One disadvantage of this method is that it lacks flexibility.
[0005]
Each of the above-described methods is effective, but a large number of circuits and a large amount of operation are necessary to achieve sufficient control in these methods. Other methods of controlling the current profile are even more effective and easily achievable. Noise reduction is achieved by matching the slope of the current profile at the end of the energized portion of the phase as closely as possible with the slope of the tail current decay portion of the current profile. The present inventor has proposed an apparatus and method for controlling tail current decay in the aforementioned US patent application Ser. No. 175,268. According to this method, the slope of the decay portion of the current profile can be controlled. In contrast, the circuit and method of the present invention achieves a smooth change in the current profile without affecting the phase energization section and other important operating parameters of the motor, thereby greatly reducing noise. The phase biasing portion of the current profile can be controlled.
[0006]
SUMMARY OF THE INVENTION
Some objects of the present invention are to provide a current in each phase of a single-phase or two-phase SRM, for example a two-phase or three-phase SRM, such as a 12-6 type two phase SRM or a 6-4 type three phase SRM. Providing a control method and device for manipulating the profile, providing a control method and device for controlling the current profile in the energized portion of each phase to reduce motor noise, current by hard chopping or soft chopping Providing a control method and apparatus for controlling the current profile using a control method, providing a control method and apparatus for raising the current level to a peak value higher than the normal current level, In the active portion, the current is reduced below its peak value to a level below this peak value, so that the slope of the current profile that occurs when the phase becomes inactive To provide a control method and apparatus in which the implementation is much gentler than in other cases, a control method and apparatus that can be easily incorporated into existing SRM control circuits, and that may include a microprocessor. Providing, providing a control method and apparatus that raises the current to a peak value by initially greatly increasing the voltage applied to the phase winding, phase winding when the phase is energized Providing a control method and apparatus for controlling the duty cycle of a PWM signal that is used to control the current flowing through and thus to quickly raise the current to its peak value at the start of the phase energization interval, Providing a control method and apparatus for controlling the frequency of a PWM signal to achieve the same result as above, and the duty of the PWM signal to achieve the same result as To provide a control method and apparatus for changing both the vehicle and the frequency, and the change in the leveled elliptical deformation force acting on the motor when the phase of the motor changes from the energized state to the de-energized state is moderated. Therefore, it is possible to provide a control method and apparatus for correcting the vertical force generated in the electric motor so that ringing in the electric motor is reduced, and to reduce the noise over the entire operation range of the SRM and to reduce the reliability. It is to provide an excellent control circuit.
[0007]
According to the present invention, generally, an apparatus is provided for controlling the current profile in the energized portion of a single-phase or multi-phase SRM. The switch is closed to direct current to the windings when the phase is energized. Hall effect sensors and other types of sensors are used to detect various operating parameters of the SRM. A PWM signal generator or microprocessor having a PWM signal output terminal responds to the input from the sensor and outputs a PWM operation signal to at least one of the two switches to control the current to the winding. The operating signal controls the switch so that the operation of the switch is controlled as a function of the signal characteristics of the operating signal. As a result, current is supplied to the winding according to a predetermined profile. According to this predetermined profile, the current is quickly increased from 0 to the peak value initially when the phase becomes energized. The current is then reduced from the peak value to a second value lower than the peak value until the phase is de-energized. Further current decreases from the second value when the phase is de-energized state to 0. The change in current profile that occurs when the phase switches from the energized state to the de-energized state is a gentle change, not a sudden change. This gentle change generally reduces the degree of ringing that occurs in the motor when supply of current to the winding is stopped, thereby reducing motor noise. Also disclosed herein is a method for controlling the current profile.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0009]
In the accompanying drawings, the switching reaction motor M (see FIGS. 6A and 6B) may be a single-phase switching reaction motor or a two-phase, three-phase or four-phase motor, It is a multiphase motor. Examples of such motors are 12-6 type two-phase motors and 6-4 type three-phase motors. The motor has a stator assembly S that includes a plurality of stator teeth ST (only one of which is shown in the drawing). The electric motor further includes a rotor assembly R attached to the shaft H and arranged to rotate relative to the stator assembly, the rotor assembly R having a plurality of rotor teeth RT. When the rotor rotates in the clockwise direction as shown, a force is generated in the stator assembly and the rotor assembly. These forces reach their maximum values when the rotor teeth are directly facing the stator teeth, as indicated by the lengths of the arrows in FIGS. 6 (A) and 6 (B), respectively. These forces produce an elliptical deformation effect on the motor.
[0010]
During operation of the motor, each phase of each motor is sequentially energized and de-energized. The time during which each phase is energized depends on various operating parameters, and various control methods have been developed in the past to determine when to switch from one phase to the next. When the phase is energized, current is supplied to the phase winding W of the motor. Current is continuously supplied to the winding while the phase is energized. As shown in FIG. 4B, the supply of current to the winding starts at time To.
[0011]
The apparatus 10 of the present invention is used to control the current profile P (see FIG. 4D) in a single-phase or multi-phase switching reaction motor M during the energized portion of each phase. As shown in FIG. 1, the phase winding W is connected to the DC bus by the switch device 12. The switch device directs current to the winding when the phase is energized, the first switch S1 connecting the winding to one side of the bus and the winding to the other side of the bus And a second switch S2. The switching device also includes corresponding diodes D1 and D2. When the phase indicated by the winding is in the energized state, switches S1 and S2 are closed.
[0012]
Various detection devices for detecting the operating parameters of the electric motor are provided. For example, in FIG. 6A, a Hall effect sensor 14 for detecting the instantaneous position of the rotor assembly R is provided. Although not shown in the figure, other sensors for outputting the rotational speed and torque of the motor and parameter information similar to these are also provided. In addition, a signal generator, indicated generally at 16 in FIG. 1, is provided, which includes a PWM signal generator, which controls the current to winding W. Therefore, an operation signal is output to one or both of the switches S1 and S2 for the reason described later. In FIG. 1, a control device generally indicated by reference numeral 18 is provided, and this control device controls the operation of the signal generator in response to an input signal from the detection device. The control device controls the operation of the signal generation device so that the signal generation device outputs an operation signal having an operation characteristic that allows a current to be supplied to the winding according to a predetermined profile.
[0013]
4A, 4B, and 5A, a typical current profile P1 for one phase of the motor and the leveled force generated in the motor are illustrated. In particular, in FIG. 4B, the current level is illustrated as being zero before the particular phase corresponding to the winding is energized. The phase becomes energized at time To. Thereafter, current is supplied to the phase winding until time Tc. At time Tc, the phase is de-energized and no current is supplied to the winding. From time Tc to time Tf, the current gradually decreases to zero. As current begins to flow into the phase winding, the current level rises to level Ip and reaches this level at time Tx. From time Tx to time Tc, the current flowing in the winding is constant and maintained at level Ip. When the supply of current to the winding is stopped at time Tc, the slope of the current profile changes rapidly. This is due to the fact that the current in the winding is abruptly reduced to 0 below Ip at time Tc as shown by the steep slope of the current profile. An inductance profile L for winding W is shown in FIG. 4A, showing the inductance in the winding for the current supplied to the phase according to the profile of FIG. 4B. As shown in FIG. 5A, the leveled force profile F1 for the motor also shows a sudden change at time Tc when the current is interrupted. The abrupt change in the slope of the leveled force profile thus causes the noise ringing shown by waveform V1 in FIG. This ringing generates a high level of noise in the motor, which is undesirably high.
[0014]
It is a feature of the circuit 10 and method of the present invention to generate a current profile such as the profile P2 shown in FIG. According to the method of the present invention, the current to the winding rises rapidly from zero to the peak value Ip 'when the phase is energized. As shown in FIG. 4D, the current is raised to this peak value between time point To and time point Tx. At time Tx, current reduction begins and the current is reduced to a second value lower than the peak value, eg, current level Ip, until the phase is de-energized at time Tc. The current then decreases from this second value to zero when the phase is de-energized. Thus, the advantage of controlling the current profile is that the current profile slope between time Tx and time Tc occurs in a substantially horizontal state as occurs in the typical situation of FIG. It is not to be. That is, the current profile has a negative slope that is similar to the slope from the time Tc to the time Tf and has a small slope. Thus, even if the current supply to the phase is stopped at time Tc, the current profile change that occurs is not a sudden change but a much gentler and smoother change. In FIG. 5B, which shows the leveled force profile F2 of the motor when current is supplied to the phase according to the profile P2, the motor is currently turned off when the current to the winding is stopped. The degree of ringing that occurs is reduced by the gentle and smooth changes described above. This is shown by the waveform V2 in FIG. 5B, and the noise of the motor is greatly reduced as shown.
[0015]
As previously mentioned, the circuit 10 of the present invention includes a PWM signal generator 16 that provides an operating signal to one or both of the switches S1 and S2. Alternatively, as shown in FIG. 2, the circuit 10 'includes a microprocessor having a PWM signal output terminal for supplying an operating signal to the switch. Either the signal generator 16 or the microprocessor 20 can output a PWM signal which is a “soft” chopping signal or a “hard” chopping signal. A soft chopping PWM signal is shown in FIG. 3A, and a hard chopping PWM signal is shown in FIG. If the signal generator or microprocessor outputs a soft chopping signal, that signal is only supplied to one switch, eg switch S2, so that the switch is between the “on” and “off” positions. Switched. The other switch S1 is maintained in the “on” state during the energized portion of the phase. On the other hand, if the signal generator or microprocessor outputs a hard chopping signal, that signal is supplied to both switches simultaneously.
[0016]
FIG. 4C shows a PWM signal G1 for supplying current to the phase winding according to the current profile P1. The signal G1 has a constant frequency and a constant duty cycle over the entire energization time from time To to time Tc. The average voltage curve A1 shows the average voltage of the PWM waveform supplied to the phase during the phase energization time, and is a constant value throughout the phase energization time. In order to achieve the current profile P2 according to the invention, the PWM signal supplied to the windings, i.e. the signal G2 (see FIG. 4E), may be controlled in a number of different ways. In FIG. 4E, the frequency of the operation signal is constant, but its duty cycle is variable. As shown in FIG. 4E, from the time point To to the time point Tx, the operation signal starts with the first value and has a duty cycle that gradually decreases over the entire interval. The operation signal has a constant duty cycle from time Tx to time Tc. However, this duty cycle is shorter than the duty cycle of the operating signal supplied to one or both switches from time To to time Tx. Thus, the average voltage curve of the PWM signal supplied to the phase in the phase energized portion has a first portion where the average voltage is substantially higher than the average voltage of the second portion. The lengths of the first and second portions correspond to the time of the variable and constant duty cycle of the PWM signal supplied to the phase, respectively. This is important. This is because, in order to increase the current to the desired peak value Ip 'by time Tx, the average voltage input to the phase is substantially higher than the average voltage supplied otherwise. This means that it must be a value.
[0017]
7A to 7C, in particular, FIG. 7A shows the waveform of another PWM operation signal corresponding to the operation signal shown in FIG. 4E. According to this waveform, in the period from the time point To to the time point Tx, the duty cycle of the operation signal is initially the first value, and then gradually decreases. In the section from the time Tx to the time Tc, the operation signal has a constant duty cycle shorter than the duty cycle of any operation signal supplied to the switch device in the section from the time To to the time Tx. FIG. 7B illustrates another way of achieving the same result, i.e., providing a fairly high voltage to the phase during the first part of the phase energization time, which is represented by a duty cycle. Includes supplying a PWM signal having a constant frequency but a variable frequency. The frequency starts at a predetermined frequency and gradually increases from time To to time Tx. In the section from the time point Tx to the time point Tc, the operation signal has a constant frequency higher than the frequency of any operation signal supplied to the switch device from the time point To to the time point Tx. In addition, FIG. 7C illustrates a third method of supplying a fairly high voltage to the phase during the first part of the phase energization time, which is variable in both duty cycle and frequency. Including supplying a PWM signal. Regardless of how the frequency and duty cycle of the operating signal change from the time point To to the time point Tx, the operating signal has a constant frequency and a constant duty during the period from the time point Tx to the time point Tc. Have a cycle.
[0018]
What has been described above is a control method and apparatus for manipulating the current profile in each phase of a single-phase or multi-phase SRM. A circuit that accomplishes this control method controls the current profile in the energized portion of each phase to reduce motor noise. Also, in the circuit and method of the present invention, either hard chopping or soft chopping current control methods may be used to control the current profile. In operation, the current level is first increased to a peak value higher than normal. The current is then reduced from its peak value to the same current level as the normal value when the phase enters the de-energized state. As a result, the slope of the current profile when the phase is deactivated is much gentler than in other cases. The control device and method of the present invention can be easily incorporated into existing SRM control circuits and may include a microprocessor. In accordance with the method of the present invention, PWM is used to control the current flowing in the phase winding when the phase is in the energized state, thereby quickly raising the current to its peak value at the start of the phase energization time. The duty cycle of the signal is used. Also, the frequency of the PWM signal is changed to achieve the same result. Also, both the duty cycle and frequency of the PWM signal may be changed to achieve the same result. In the motor to moderate the variation of the leveled elliptical deformation force acting on the motor when the phase of the motor changes from the energized state to the de-energized state, thereby reducing ringing in the motor Correcting the generated normal force is one advantage of the control method and apparatus of the present invention.
[0019]
In view of the foregoing, it will be seen that the several objects of the invention are achieved and other advantageous results are obtained.
[0020]
Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention. This will be apparent to those skilled in the art.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a first circuit of the present invention for manipulating the current profile of the current supplied to the SRM winding in the phase energization portion.
FIG. 2 is a block diagram illustrating a second circuit of the present invention for manipulating a current profile.
FIGS. 3A and 3B show waveforms of PWM signals for soft chopping and hard chopping for controlling the current supplied to the windings, respectively.
4A is a graph showing phase winding inductances in the energized and de-energized portions of the motor phase, and FIG. 4B is a typical one in the energized portion of the phase. (C) shows the PWM signal and its average voltage used to generate the current profile of (B), and (D) shows the current profile generated by the circuit of the present invention. (E) shows the PWM signal used to generate the current profile of (D) and its average voltage.
FIG. 5 (A) shows the normal force in the motor and the phase in the deenergized state at the energized portion of the phase for the case where the current profile for the motor corresponds to the profile of FIG. 4 (B). (B) shows the generated ringing and the normal force in the motor and the phase is de-energized in the energized part of the phase for the case where the current profile for the motor corresponds to the profile of FIG. It shows the ringing that occurs when entering a state.
FIG. 6 shows the force generated in the motor when the rotor pole of the motor passes through the stator pole. In particular, FIG. 6A shows the case where the two poles are not aligned with each other, and FIG. The case where two poles are aligned with each other is shown.
FIG. 7 illustrates various PWM signals that can be used by the circuit of the present invention to obtain the current profile of FIG. 4 (D).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Apparatus 12 of this invention ... Switch apparatus 14 ... Hall effect sensor 16 ... Signal generator (PWM signal generator)
18 ... Control device 20 ... Microprocessor M ... Switching reaction motor S ... Stator assembly R ... Rotor assembly

Claims (8)

An apparatus for controlling a current profile of a current supplied to a phase winding of an SRM,
A switching device that directs current to the phase winding when the phase is energized;
A detection device for detecting an operating state of the SRM;
A signal generator for supplying an operation signal to the switch device for controlling a current to the phase winding;
In the control device that controls the signal generation device in response to the detection device,
A profile of the current supplied to the phase winding is supplied to the phase winding by applying a voltage having a first positive average voltage to the phase winding when the phase is in an energized state. The current is rapidly increased to a peak value, and then the phase winding is given a second positive average voltage lower than the first average voltage by the time the phase is deactivated. PWM operating signal that the signal generator supplies current to the phase winding such that the current supplied to the phase winding has a profile that is reduced from the peak value to a second value lower than the peak value. A control device for controlling the signal generator to output
Including
The signal generator is a PWM signal generator,
A PWM operation signal with a variable duty cycle that gradually shortens the duty cycle when the current increases from 0 to its peak value, and then a PWM operation with a constant duty cycle until no current flows through the phase winding. Generating the signal and, as a function of the duty cycle, the average of the operating signal so that the average voltage of the operating signal increasing to the peak value of the current is higher than the average voltage of the operating signal after reaching the peak value Control the voltage, or
Generates a frequency variable PWM operation signal whose frequency gradually increases as the current increases from 0 to its peak value, and then no current flows through the phase winding after reaching the current peak value. A PWM operation signal with a constant frequency is generated, and as a function of frequency, the average voltage of the operation signal that is increasing up to the peak value of the current is higher than the average voltage of the operation signal after reaching the peak value Control the average voltage of the operating signal
Including a PWM signal generator,
The magnitude of the current in the phase winding is a function of the operating signal, and the current decays from the second value when the phase is in the de-energized state, thereby causing the phase to be de-energized from the energized state. The change that occurs in the current profile when switching to the energized state is not an abrupt change, and the degree of ringing that generally occurs in the motor when the supply of current to the phase winding is stopped by this non-abrupt change A device that is configured to reduce and thereby reduce motor noise. 2. The apparatus of claim 1, wherein the SRM is a multi-phase SRM having one phase winding for each phase, and the controller provides current to each phase winding when each phase is in an energized state. A device characterized in that the current profile supplied to each phase winding is controlled by controlling the average voltage of the operation signal supplied to the switch means for passing the current. 3. The apparatus of claim 2, wherein the switch means includes first and second switches, wherein the phase windings are each connected between corresponding first and second switches, And the second switch allows current to flow to the corresponding phase winding when energized, and the signal generator modulates one of the first and second switches according to the operating signal. To control the operation of the switch. 4. The apparatus according to claim 3, wherein the signal generator modulates both the first and second switches by the operation signal, and the both switches are controlled by characteristics of the operation signal. Equipment. 5. The apparatus of claim 4 , wherein the control unit includes a microprocessor that receives inputs relating to operation of the SRM and is to be generated when these inputs and the phase are in an activated state. An apparatus for controlling the signal characteristic of the operating signal generated by the signal generator as a function of a current profile of the signal. 6. The apparatus of claim 5 , wherein the controller is responsive to an input from the detector and varies the pulse width, duty cycle and frequency of the PWM signal generator while current is supplied to the phase winding. Generating an operating signal having the average voltage to achieve the current profile. 7. The apparatus of claim 6, wherein the microprocessor is responsive to an input representative of the operating state of the SRM and the PWM signal generator pulse width, duty cycle, and frequency while current is supplied to the phase winding. To achieve the current profile. A method for controlling current to a phase winding of an SRM, comprising:
Incorporating the phase winding into a circuit that conducts current to the phase winding when the phase is energized;
Generating an operating signal used to control a current to the phase winding to follow a predetermined profile;
The process of controlling the characteristics of the operating signal, where the current is rapidly increased to a peak value when the phase is in the energized state and then supplied to the phase winding by the time the phase is de-energized Controlling the operation signal such that the current to be applied is reduced from the peak value to a second value lower than the peak value;
Including
In the process of controlling the characteristics of the operation signal,
(A) Generate a PWM operation signal with a variable duty cycle that gradually shortens the duty cycle when the current increases from 0 to its peak value, and then the duty cycle is constant until there is no current flowing through the phase winding. The PWM operation signal is generated and, as a function of the duty cycle, the average voltage of the operation signal that is increasing up to the peak value of the current is higher than the average voltage of the operation signal after reaching the peak value. Control the average voltage of the signal, or
Generates a frequency variable PWM operation signal whose frequency gradually increases as the current increases from 0 to its peak value, and then no current flows through the phase winding after reaching the current peak value. A PWM operation signal with a constant frequency is generated, and as a function of frequency, the average voltage of the operation signal that is increasing up to the peak value of the current is higher than the average voltage of the operation signal after reaching the peak value Control the average voltage of the operating signal so that
The magnitude of the current in the phase winding is a function of the operating signal, and the current decays from the second value when the phase is in the de-energized state, thereby causing the phase to be de-energized from the energized state. The change that occurs in the current profile when switching to the energized state is not an abrupt change, and this non-abrupt change reduces the degree of ringing that typically occurs in motors when the current supply to the windings is stopped And thereby reducing the noise of the motor.

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