JPH0318438B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to the control of the rotation speed of a brushless motor, and particularly to a method for controlling an inverter output voltage when controlling the rotation speed of a brushless motor using a pulse width modulation type inverter. [Prior Art] As is well known, in this type of motor control, in order to generate a rotating magnetic field in the armature winding, a predetermined electrical angle π/m (m is the number of phases) is applied to the armature winding in units of radians. It is necessary to switch the direction of current flowing.
This current control, for example, as disclosed in Japanese Unexamined Patent Publication No. 53-54729, detects the relative position between the field pole and the armature winding using a position sensor, and then controls the control circuit based on the output. This is performed by performing chopper control on a plurality of switching elements of a motor rotation control inverter (commutator). In order to perform the above-described current control, a motor drive signal (pulse width modulation signal) is provided at every predetermined electrical angle π/m. When controlling the rotation, the pulse width of the drive signal is modulated to change the conduction rate. That is, for each drive signal, the time T _n corresponding to the electrical angle π/m (where,
T _n can be expressed as T _n =1/2 _I m. _I is assumed to undergo pulse width modulation depending on the inverter frequency). In this case, if the pulse width modulation signal that exists at time T _n corresponding to the electrical angle π/m is a single pulse, the distortion of the current flowing through the motor will be greater than when it is divided into multiple pulses. , motor efficiency tends to be poor. Therefore, it is proposed that a plurality of pulse width modulation signals exist within a time corresponding to a predetermined electrical angle π/m. Here, a conventional example in which a plurality of pulse width modulation signals are present at a predetermined electrical angle π/m will be described with reference to FIGS. 1 to 3. Fig. 1 is a basic configuration diagram of a well-known brushless motor, Fig. 2 is a time chart for explaining the conventional inverter operation, and Fig. 3 is a characteristic diagram of the relationship between apparent conduction rate and rotation speed. . In this conventional example, a three-phase brushless motor is used, the predetermined electrical angle π/m is 60 degrees, and the corresponding time T _n is expressed by the symbol T60 degrees. In FIG. 1, an AC power supply 1 is converted to DC by a rectifier circuit 2 and a smoothing capacitor _Cd , smoothed, and supplied to an inverter 3. The three-phase AC output of the inverter 3 is applied to the armature winding 4 - 1 of the synchronous motor 4 to drive the synchronous motor 4 . Transistor A+ constituting the inverter 3
The drive signals A+b to C-b given to ~C- are
A position detection element 5, such as a Hall element, for detecting the position of the rotor 4-2 of the synchronous motor 4.
It is formed by the control circuit 6 based on the output signals of -1 to 5-3. In the brushless motor configured as described above, the rotation speed of the synchronous motor 4 can be controlled by changing the output voltage of the inverter 3 using a pulse width modulation method. Here, a conventional method of forming drive signals A+b to C-b for making the inverter 3 of the pulse width modulation type will be explained with reference to FIG. 1 in FIG. 2 is the position detection element 5 shown in FIG.
These are the position detection signals a to c obtained from -1 to 5-3, and each rise of the position detection signals a to c,
And from the falling point, the electrical angle of 2 in Fig. 2
A synchronization pulse s every 60 degrees is obtained. Then, by this synchronization pulse s, _{the triangular wave VT is} reset as shown in ₃ in _FIG . A pulse width modulated signal g shown in 4 is formed to have 4 pulses. Next, this modulation signal g and the above position detection signal a
-c are appropriately combined to obtain desired drive signals A+b to C-b as shown in 5 in FIG. Here, it is assumed that each drive signal is modulated by the modulation signal g in units of time T60° corresponding to 60 electrical degrees. In this way, when a modulation signal is taken in every 60 electrical degrees of each drive signal, if it exists as multiple pulse width modulation signals as shown in 5 in Figure 2, the current flowing through the motor can be reduced as described above. Since distortion is reduced, efficient motor control can be performed. [Problem to be Solved by the Invention] By the way, the conduction rate Da of the modulation frequency is generally calculated as follows, where T _ON is the pulse conduction time per period T _M , Da=T _ON /T _M ×100%...(a) It is expressed as 60 electrical degrees (π/
m) When a plurality of pulse width modulation signals are present within the corresponding time T60° (Tm), equation (a) does not necessarily hold true for the following reason. In other words, when capturing multiple pulse width modulated signals at time T60°, unless some consideration is taken, time T60° and the sum of the periods of the modulated signals existing within this time will not necessarily match, and as a result, the second As shown in FIG. 5, the period T _M ' of the last modulated signal among the pulse width modulated signals existing at time T60° may not satisfy the period T _M . In this case, formula (a) cannot be applied,
The true conduction rate D _T (%) is obtained from the sum ΣT _ON of the on-pulses of the modulation signal g within the time T60° at a certain rotational speed N (rpm), and in this case the time T60°. The true conductivity _DT is expressed by the following formula. D _T = (PNΣT _ON /10) x 100%...(b) In addition, P is the number of poles of the synchronous motor, and N is the number of rotations of the synchronous motor. That is, the true conductivity _DT , which determines the rotation speed, is also a function of the rotation speed N. The motor rotation speed N is the true conduction rate of the modulation signal g
D Proportional to _T. Here, the conductivity D _T in equation (b) is referred to as the true conductivity, while the conductivity Da in equation (b) is referred to as the apparent conductivity for convenience. By the way, in the conventional pulse width modulation method described above, the frequency of the modulation signal g (hereinafter referred to as modulation frequency) _M (1/T _M ) is always constant regardless of the rotation speed N of the synchronous motor. What can be controlled externally is one cycle of the modulation signal g, which was already mentioned.
The ratio of on-pulse to T _M is the so-called apparent conduction rate Da, and since this apparent conduction rate Da and the true conduction rate D _T do not match, the apparent conduction rate is The ratio Da and the rotational speed N do not have a linear relationship, and furthermore, the rotational speed sometimes becomes unstable in a certain rotational speed range. I would like to add here that pulse width modulation type inverters for general induction motors are different from those for brushless motors mentioned above, and do not have anything that corresponds to the position detection signal, so the modulation signal is used as the reference. The output frequency and output voltage of the inverter can be determined independently. However, on the other hand, a brushless motor exhibits the same characteristics as a DC motor, and when the inverter output voltage is determined, the rotation speed, that is, the inverter output frequency is determined in relation to the load on the synchronous motor. In other words, the inverter output frequency is determined secondarily. In the conventional pulse width modulation method for brushless motors, there is no correlation between the frequency of the position detection signal and the modulation signal shown in 1 and 4 in FIG.
This is why the above-mentioned problem arose. Incidentally, such a problem is not limited to the electrical angle of 60 degrees, but also occurs in cases other than three phases if the electrical angle is in the relationship of π/m. The present invention has been made in view of the above points, and its purpose is to provide synchronization even when the inverter drive signal is modulated with a plurality of pulse widths within the time corresponding to the electrical angle π/m. By associating the motor rotation speed with the modulation frequency, the true conduction rate and apparent conduction rate described above can be made to match, eliminating unstable operating regions and allowing the motor to rotate stably in any rotational range. At the same time, the modulation frequency of this pulse width modulation signal and its conduction rate are
The electrical angle π/ which is the unit for switching the direction of the rotating magnetic field
The purpose is to be able to determine and update in short intervals of m radians, to quickly respond to speed fluctuations, and to improve control accuracy. [Means for Solving the Problems] In order to achieve the above object, the present invention controls the output voltage of an inverter for a brushless motor as follows. That is, the present invention includes a rotor 4-2 made of a permanent magnet with 2P (P is the number of poles) poles, and an m-phase armature winding 4-1 that magnetically applies rotational force to the rotor.
and a synchronization pulse s every predetermined electrical angle π/m (radian, m is the number of phases) based on the rising and falling signals of the position detection signals a to c obtained from the magnetic pole position of the rotor 4-2. is generated, a plurality of pulse width modulation signals g are made to exist within a time T _n corresponding to the electrical angle π/m, which is the interval between these synchronization pulses, and the conductivity Da of this pulse width modulation signal g is changed to produce a brushless A method for controlling an inverter output voltage of a motor, comprising: rotation speed data detection means for detecting data regarding the rotation speed of the motor based on a pulse train proportional to the rotation speed; A modulation frequency determining means for determining a modulation frequency _M of the pulse width modulation signal g; and a conduction rate determination means for changing the conductivity Da of the pulse width modulation signal g in relation to the output signal of the rotation speed data detection means. , the operation of the rotation speed data detection means is synchronized with the synchronization pulse s in units of time T _n corresponding to the electrical angle π/m, and data regarding the motor rotation speed is detected every T _n ; In addition, the modulation frequency _M is set as _M = 2 x m x n x _I for the inverter output frequency _I determined from this detection data.
(n is an arbitrary integer of 2 or more), and the conductivity Da is also determined based on the rotational speed detection data for each time _{T n} , and The first modulated signal among the pulse width modulated signals g is generated in synchronization with the synchronization pulse s. [Operation] According to such a control method, as a precondition, as mentioned in the section of the prior art, the rise and rise of the position detection signals a to c obtained from the magnetic pole position of the rotor 4-2 during rotation of the motor are A synchronization pulse s is generated every electrical angle π/m based on the downlink signal. In the present invention, the rotation speed data detection means synchronizes with the synchronization pulse s and detects the motor rotation speed every T _{n based on a pulse train proportional to the motor rotation speed in units of time T n corresponding} to the electrical angle π/m. Detect data related to T n (e.g., measured time required for T _n , rotation speed, etc.). Here, as the pulse train proportional to the motor rotation speed, a reference clock signal generated at a predetermined period or an output signal from an encoder or the like may be used, for example, as will be described in the embodiment described later. In the embodiment, these pulse trains are counted in units of T _n . Based on the rotational speed data detection value detected in units of T _n , the conduction rate determining means determines the conductivity Da of the pulse width modulation signal g, and the modulation frequency determining means determines the modulation frequency _M that satisfies the following relational expression. , are determined and updated every T _n . The modulation frequency _{M is} determined from the inverter frequency _I determined from the motor rotation speed detection value.
It is determined to satisfy the relational expression =2×m×n× _I . Here, the arbitrary integer n corresponds to the number of pulse width modulation signals that should be present during the time T _n corresponding to the electrical angle π/m. Since this relational expression is satisfied,
The modulation frequency _M is always a constant integer ratio (integer multiple) to the inverter output frequency, that is, the motor rotation speed.
relationship can be maintained. Therefore, even if the motor rotational speed fluctuates and the time width T _n corresponding to the electrical angle π/m changes, it is difficult to compare T _n with each period of the plurality of pulse width modulation signals taken into this time width. can also be maintained in a constant integer ratio relationship. Therefore, when a plurality of frequency-modulated pulse width modulated signals are taken in (existed) in the time T _n in this way, if the first modulated signal among them is generated in synchronization with the synchronization pulse s, The conventional difference between the time width of T _n and the period T _M of the pulse width modulation signal is
Since a deviation such as T _M ′ does not occur, development in which the apparent throughput Da and the true throughput D _T do not match does not occur. Therefore, the generally known conduction rate of equation (A) is
Even when Da is used for inverter output control, the conduction rate and motor rotational speed are in a proportional relationship, and the existence of an operating region where the rotational speed is unstable can be eliminated. In addition, both the conductivity and modulation frequency of such a pulse width modulation signal are determined (updated) by the motor rotation speed detection value every short time T _n , which is the minimum unit for switching the direction of the rotating magnetic field. , these update duty factor and modulation frequency for the next time T _n
can be applied to quickly respond to speed fluctuations. In particular, since the time T _n is the unit for switching the direction of the rotating magnetic field of the m-phase winding, updating the conduction rate and modulation frequency for each time unit allows the strength of the rotating magnetic field to be controlled in a timely manner, and the motor control Improve accuracy. Furthermore, since a plurality of pulse width modulation signals are present within the time period of this electrical angle π/m, distortion of the current flowing through the motor is reduced, thereby increasing the efficiency of the brushless motor. [Embodiment] Next, an embodiment of the present invention will be described based on FIGS. 4 to 9. Here, FIG. 4 is a basic configuration diagram of a brushless motor used for rotation speed control (inverter output voltage control) according to an embodiment of the present invention, and FIG. Figure 6 is a diagram showing the configuration of the main parts, Figure 6 is a time chart explaining its operation, Figure 7 is a diagram showing the configuration of the main parts related to the rotation speed detection section, Figure 8 is a time chart showing the waveforms of each part, and Figure 9 is the calculation process. This is a flowchart. First, in Fig. 4, the same symbols as in Fig. 1 above indicate equivalent parts, 7 is a waveform shaping circuit, and 8 is a waveform shaping circuit.
1 is a microcomputer with arithmetic functions, 9 is a central processor (referred to as CPU), 10 is random access memory (referred to as RAM), 11 is read-only memory (referred to as ROM), and 1
2 is an input/output circuit, 13 is a pulse output circuit, 14 is an interface circuit, and 15 is a pulse input circuit. Further, 16 is a data bus, 17 is an address bus, 18 is a control bus, and 19 is a driver circuit. Microcomputer 8 has CPU9, RAM1
0 and ROM 11, and the input/output circuit 12 is an interface circuit 1 with the CPU 9.
4, a pulse output circuit 13, and a pulse input circuit 15. The CPU 9, RAM 10, ROM 11 and input/output circuit 12 are connected to the data bus 16, address bus 1
7, connected by control bus 18. The microcomputer 8 and the input/output circuit 12 are synchronized by applying an enable signal E from the CPU 9 as shown in the figure. Further, signals corresponding to the rotational position of the rotor 4-2 of the synchronous motor 4 from the position detection elements 5-1 to 5-3 are input to the waveform shaping circuit 7, and are shown in 1 in FIG. The position detection signals a to c are input to the pulse input circuit 15 in the input/output circuit 12. Then, these position detection signals a to c are processed by the pulse output circuit 13 to generate a drive signal A+b.
~C-b is formed, thereby driver circuit 1
The inverter 3 is driven through the inverter 9. The above-mentioned pulse output circuit 13 is a circuit provided to achieve the object of the present invention, and is a circuit provided in order to achieve the object of the present invention.
It consists of seed registers (P1 register, D1 register, rotation speed register NR), a modulation signal generation section 200 (shown in FIG. 5), and a rotation speed detection section 30 (shown in FIG. 7). Of these, the rotation speed detection section 30 serves as rotation speed data detection means (means for detecting data regarding the rotation speed of the motor) which is a component of the present invention. In the embodiment, the rotation speed detection section 30 receives the position detection signals a~
It has a function of detecting data regarding the rotation speed of the synchronous motor 4 based on the rotation speed of the synchronous motor 4. The modulation signal generation section 200 works together with the CPU 9 to determine the modulation frequency determining means (means for determining the modulation frequency _{M of the pulse width modulation signal g in relation to the rotational speed data detection signal) and the conduction rate determining means (means for determining the modulation frequency M} of the pulse width modulation signal g in relation to the rotational speed data detection signal). The conduction rate of the pulse width modulated signal g in relation to the signal
In other words, it is configured to also serve as means for changing the conductivity of the drive signals A+b to C-b. That is, the CPU 9 calculates the above-mentioned _M = 2× based on the rotation speed data detection signal from the rotation speed detection unit 30.
The data of the modulation frequency _M that satisfies the relational expression m×n× _I is calculated, and this calculated data is sent to the modulation signal generator 2.
Send to P1 register of 00. Then, the modulation signal generating section 200 controls the pulse width modulation signal g so that it becomes the modulation frequency _M corresponding to the modulation frequency data P1D of the P1 register. Further, the CPU 9 generates a pulse width modulation signal g based on the rotation speed data detection signal from the rotation speed detection section 30.
The conduction rate Da is calculated and the calculated data is sent to the D1 register of the modulation signal generation section 200. and,
The modulation signal generating section 200 controls the pulse width modulation signal g so that the conduction rate corresponds to the conduction rate data D1D of the D1 register. Note that specific operations of the modulation signal generating section 200 and the rotation speed detecting section 30 will be described later. The basic operation of the embodiment shown in FIG. 4 having the above configuration is as follows. That is, all the operation contents necessary to operate as a brushless motor are stored as a program in the ROM 11, and according to the program, the pulse output circuit 13 is transmitted via the CPU 9, the RAM 10, and the interface circuit 14.
Transmission of data to various registers within is performed in synchronization based on enable signal E. Then, when the position detection signals a to c as input data are input to the input/output circuit 12, based on the position detection signals a to c, the CPU 9 sends the address bus 17, data bus 16, and control bus 1 to the input/output circuit 12.
8, drive signals A+b to C-b are formed according to data given to various registers in the pulse output circuit 13, which will be described later. Next, the pulse output circuit 13, which forms the basis of the present invention as described above, will be described in detail. First, Table 1 summarizes the functions of each of the various registers in the pulse output circuit 13.

〔Effect of the invention〕

As described above, according to the present invention, even when the inverter drive signal is present as a plurality of pulse width modulated signals within the time corresponding to the electrical angle π/m, the rotation speed and modulation frequency of the synchronous motor can be adjusted. By associating them, the true conductivity and the apparent conductivity described above can be made to match, thereby eliminating unstable operating regions and allowing the motor to rotate stably in any operating region. In addition, the modulation frequency of this pulse width modulation signal and its conductivity can be determined and updated in short intervals of electrical angle π/m radian, which is the unit of switching the directionality of the rotating magnetic field, so it can quickly respond to speed fluctuations. It is possible to increase the control accuracy of motor rotation. Moreover, since it is assumed that multiple pulse width modulation signals exist within the time of this unit electrical angle π/m, it is possible to reduce distortion of the current flowing through the motor and maintain high efficiency of the brushless motor. can.

[Brief explanation of drawings]

Figure 1 is a basic configuration diagram of a conventional brushless motor, Figure 2 is a time chart for explaining the conventional method, and Figure 3 is the relationship between apparent conduction rate and rotation speed. A characteristic diagram, FIG. 4 is a basic configuration diagram of a brushless motor used in the brushless motor rotation speed control method according to an embodiment of the present invention, and FIG. 5 is a configuration of main parts related to the modulation signal generation section. 6 is a time chart explaining its operation, FIG. 7 is a configuration diagram of main parts related to the rotation speed detection section, FIG. 8 is a time chart showing waveforms of each part, and FIG. FIG. 3 is a flowchart of calculation processing. 3...Inverter, 4...Synchronous motor, 7...
Waveform shaping circuit, 8...Microcomputer, 1
2...Input/output circuit, 13...Pulse output circuit, 1
5... Pulse input circuit, 19... Driver circuit,
30...Rotation speed data detection means (rotation speed detection section),
9,200...Modulation frequency determining means/conduction rate determining means (CPU, modulation signal generation unit), a to c...Position detection signal, g...Modulation signal.

Claims (1)

[Claims] A rotor 4-2 made of a permanent magnet with 12P (P is the number of poles) and an m-phase armature winding 4-1 that magnetically applies rotational force to the rotor. , the rotor 4-
A synchronization pulse s is generated every predetermined electrical angle π/m (radian, m is the number of phases) based on the rising and falling signals of the position detection signals a to c obtained from the magnetic pole positions of No. 2, and this synchronization A plurality of pulse width modulation signals g are made to exist within a time T _n corresponding to the electrical angle π/m, which is the interval between pulses, and the inverter output voltage of the brushless motor is controlled by changing the conduction rate Da of the pulse width modulation signals g. A method comprising: rotation speed data detection means for detecting data regarding the rotation speed of the motor based on a pulse train proportional to the rotation speed; and modulation of the pulse width modulation signal g in relation to an output signal of the rotation speed data detection means. A modulation frequency determining means for determining the frequency _M , and a conduction rate determining means for changing the conduction rate Da of the pulse width modulation signal g in relation to the output signal of the rotation speed data detection means, The operation of the detection means is synchronized with the synchronization pulse s in units of time T _n corresponding to the electrical angle π/m, and data regarding the motor rotation speed is detected every T _n , and the inverter is determined from the detected data. The modulation frequency _M for the output frequency _I is _M = 2 x m x n x _I
(n is an arbitrary integer of 2 or more), and the conductivity Da is also determined based on the rotational speed detection data for each time _{T n} , and A method for controlling an output voltage of an inverter for a brushless motor, characterized in that a first modulation signal among the pulse width modulation signals g is generated in synchronization with the synchronization pulse s. 2. In claim 1, position detection signals a to c having a frequency proportional to the rotation speed are inputted to the rotation speed data detection means, and the position detection signal is detected based on the rising and falling signals of these position detection signals. Measure the time T _n corresponding to π/m in electrical angle,
The modulation frequency determining means includes a first register that stores the time data, and the modulation frequency determining means includes a second register that can be written arbitrarily to determine the time of one cycle of the modulation frequency, and the second
A method for controlling an output voltage of an inverter for a brushless motor, characterized in that data in a register is determined based on data in a first register so as to satisfy the following relationship: modulation frequency _M = 2 x m x n x _I.