JPS61277394A - Speed-controlling method for brushless dc motor - Google Patents

Abstract

PURPOSE:To enable positional detection signal and speed control treatment to be synchronized, by computing the proportional member, integral member, and differential member of the deviation between command rotational frequency and detected rotational frequency performed arithmetic every specified time, and by determining the output voltage of an inverter according to the computation. CONSTITUTION:The position of the rotor 4 of a synchronous motor 3 is detected by a positional detection circuit 5. By a control circuit 6, a time for a very electrical angle 60n1 (n1 is positive integer) degrees is measured through positional detection signal from the positional detection circuit 5, and through the obtained time, rotational frequency every time on 60n2 (n2 is positive integer) degrees is calculated, and the proportional member, integral member, and differential member of the deviation between the command rotational frequency and the detected rotational frequency as the result of the arithmetic operation are computed, and according to the members, the output voltage of an inverter 2 is determined.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a speed control method for a brushless DC motor,
In particular, the present invention relates to a speed control method for a brushless DC motor that calculates the number of rotations by measuring the rotation period based on a position detection signal.

[Background of the invention]

The conventional speed control method of this type is
As described in the issue, the position detection signal is used to measure the time for every 60 degrees of air angle, calculate the time for 60 J degrees of electrical angle using nI as a positive remanent, and calculate the number of rotations from that time. 'Difference between the detected rotation speed and the commanded rotation speed determined by the result; calculation of the proportional, integral, and differential terms of the rotation speed; and determination of the output voltage of the inverter based on this.

However, the first process, which is the measurement of time for every 60 degrees of electrical angle, and the other processes that follow are asynchronous. That is, after calculating the time for 60 degrees, there is a time delay between the calculation result and the determination of the inverter output voltage, which causes a problem in that the response speed of the speed control system decreases.

In particular, when a brushless DC motor employing a conventional speed control method is used as a compressor motor, the following problems occur. In other words, the compressors used in room air conditioners and refrigerators are generally sealed in a chamber together with the drive motor, and the load torque applied to the compressor motor is Regardless of the rotation angle, the maximum load torque is approximately 3 times the average load torque.
It reaches twice as much. This pulsating load has a roughly fixed pattern with respect to the rotation angle.

Therefore, in the conventional speed control method that performs speed control asynchronously with the position detection signal synchronized with the rotation angle,
It becomes difficult to quickly determine the output voltage of the inverter in response to the load that changes depending on the rotation angle of 0 degrees. As a result, the differential torque between the motor output torque and the load torque increases, causing rotational pulsation, which increases the amplitude of the rotational pulsation, especially at low speeds, and also reduces the frequency of the rotational pulsation, which intensifies the vibration of the entire chamber. This problem happened very often.

[Purpose of the invention]

The purpose of the present invention is to solve the problems with the conventional speed control methods as described above, and to provide a speed control method for brushless DC motors that can control the speed in a high-speed response even when the load changes with respect to the rotational position. It is about providing.

[Summary of the invention]

The present invention is characterized by an inverter that converts power from DC to three-phase AC, a permanent magnet rotor type synchronous motor driven by the output of the inverter, and means for detecting the magnetic pole position of the rotor and outputting a position detection signal. From the position detection signal, a basic signal is generated every 60n electrical degrees, where nt is a positive integer, the rotation speed is detected from the period of this signal, and the output voltage of the inverter is determined depending on the detected rotation speed and the command rotation speed. In a brushless DC motor that performs speed control by determining the output voltage of the inverter, the process of determining the output voltage of the inverter is performed every 6012 electrical degrees in synchronization with the position detection signal, and where n is a positive integer. There are speed control methods to be implemented.

In other words, in the speed control method of the present invention, from the rotor position detection signal, nt and nt are positive integers,
Measure the time for each electrical angle of 60n1 degree, calculate the rotation speed for each 6on8 degree time from the obtained time, and calculate the proportionality, integration, and differentiation of the deviation rotation speed between the detected rotation speed and the commanded rotation speed, which are the results of this calculation. By calculating the term and determining the output voltage of the inverter based on this, it is possible to synchronize the position detection signal and the speed control process.

[Embodiments of the invention]

An embodiment of the present invention will be explained below with reference to FIGS. 1 to 4.

FIG. 1 is a block diagram of a brushless DC motor to which the present invention is applied, and its main circuit is configured to supply power to a synchronous motor 3 via a DC power supply 1 and an inverter 2.

Here, the magnetic pole position of the permanent magnet type rotor 4 of the synchronous motor 3 is detected in the position detection circuit 5 using the output voltage of the inverter 2, and based on this position detection signal, the control circuit 6 detects the rotor A switching control signal is supplied via the pace driver 7 to the transistor in the inverter 2 corresponding to the 40 rotation position.

FIG. 2 is a signal waveform diagram of each part of the main circuit, showing the operation of the brushless DC motor. FIG. 2(a) shows the position detection signal which is the output of the position detection circuit 5, and FIG. 2(b) shows the electrical angle 60.
The timing signal PS, (C) is a triangular carrier wave and has a constant oscillation frequency. A drive signal (e) for the transistor is created by logic processing with FIG. 2 (Φ is a modulation signal created by the slice level DI in FIG. Here, the rotation speed of the brushless DC motor is the slice level D above.
It is determined by changing the output voltage of the inverter 2 according to z.

FIG. 3 is a control system diagram according to the speed control method of this embodiment, which is realized by the configuration of the control circuit 6 of FIG. 1. First, in Fig. 3C, the timing signal P8C for every 60 electrical degrees is shown in Fig. 2(b)].
Multiply the period (TI+T+-Il time by 3 to calculate the time T equivalent to 1 f cycle. In the next It, calculate the rotation speed N 'k N =/T (K is a constant). death,
In Setup 3, the proportional, integral, and differential terms of the deviation rotation speed between the detected rotation speed N and the commanded rotation speed N blades, Kp, Kl,
KD is determined, and the slice level DI is determined from the sum (Kp + KI + Ko). These processes are performed by the microcomputer in the control circuit 6,
This is performed every 60 electrical degrees in synchronization with the PS signal.

FIG. 4 is a diagram showing the time relationship between the PS signal and the above processing. The processing "e fz + I3 is performed continuously at once every 60 degrees of electrical angle, while the information for calculating the rotation speed is obtained from two cycles of the latest PS signal each time processing If is executed. The time period corresponding to 120 electrical degrees is used.

According to the above method, by using two cycles of the PS signal as information on the rotation speed, the variations in measurement values that occur every cycle are averaged out, and the time measurement results for two cycles can be immediately obtained. Since this is reflected in the slice level D1, the accuracy of the detected rotational speed is improved and the response of the speed control system to changes in the rotational speed becomes faster.

Another embodiment of the present invention will be described with reference to FIGS. 5 and 6. FIG. 5 is a control system diagram showing the speed control method according to this embodiment. The difference from the control system diagram shown in Figure 3 is that L
In this method, the calculation of the time T for one cycle is switched between high speed and low speed, and the execution cycle of the process following III * L t iIs is also switched,
The processing contents of Ih and IIs are the same as in the case of FIG.

That is, since it takes a certain amount of time for a microcomputer or the like to execute processing related to speed control, at high speeds, one period of the PS signal becomes shorter, making it difficult to process within this one period. In order to avoid this, in the high speed rotation area, in the embodiments shown in FIGS.
Each process related to speed control is executed every three cycles of the signal, that is, every 180 electrical degrees. Furthermore, in the high-speed rotation region, variations in the component parts of the position configuration circuit 5 related to the position detection signal have a greater influence on the variations in the period of the PS signal, so the L Each time the process is executed, it is averaged using a time of 360 electrical degrees, which corresponds to six cycles of the latest PS signal.

FIG. 6 is a diagram showing the time relationship between the PS signal and the processing, TJx, and IIs in the high-speed rotation region. Each process is executed continuously in synchronization with the PS signal every 180 degrees of electrical angle, and the information for calculating the rotation speed is assumed to use the time equivalent to 6 cycles of the latest PS signal each time. There is.

Here, the three processes I[t, I[z, Its) do not have to be executed consecutively, but the same effect can be obtained by dividing each process and executing each process in synchronization with the PS signal. can get.

〔Effect of the invention〕

According to the present invention, since speed control is executed every 5 ounces of electrical angle of the position detection signal, for example, in a brushless DC motor for driving a compressor, the load pulsates with respect to the rotational position. The effect is particularly noticeable in practical applications, as changes in rotation speed caused by changes in load can be quickly reflected in the inverter output voltage, allowing the speed control system to achieve high speed rotation and a brushless DC motor with little pulsation. . Furthermore, according to the embodiments of the present invention, in a high-speed rotation region where changes in rotation speed caused by changes in load are alleviated by increases in physical force generated by the load and the motor, the processing time of the speed control system is reduced. Considering this, n2 is made larger than at low speeds, so it can be said that this control method has excellent practical effects.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a brushless DC motor to which the present invention is applied, Fig. 2 is a diagram of various parts and signal waveforms showing the operation of the motor shown in Fig. 1, and Fig. 3 is a speed control method according to an embodiment of the present invention. FIG. 4 is a diagram showing the processing execution timing of the speed control in FIG. 3, FIG. 5 is a control system diagram showing a speed control method according to another embodiment of the present invention, and FIG. 6 is a diagram showing the processing execution timing of the speed control in FIG. 5. FIG. 1...DC 11tL 2...Inverter, 3...
・Synchronous motor, 4... Rotation motor, 5... Position acclimatization circuit, 6... Control (b) path, 7... Pace driver,
PS...Timing signal, T...1 cycle time, T1-T6...Time for every 60 degrees of timing signal PS, N...Rotation speed, Nu...Finger first concavity $2 figure Figure 4 Figure 5 W.

Claims (1)

[Claims] 1. An inverter that converts power from direct current to three-phase alternating current, a permanent magnet rotor type synchronous motor driven by the output of this inverter, and detects the magnetic pole position of the rotor and outputs a position detection signal. from the position detection signal, generates a basic signal every 60n_1 electrical angle with n_t as a positive integer, detects the rotation speed of the rotor from the period of this signal, and combines the detected rotation speed and the command rotation speed. In the control of a brushless DC motor that performs speed control by determining the output voltage of the inverter according to the position detection signal, the process of determining the output voltage of the inverter is synchronized with the position detection signal, and
1. A speed control method for a brushless DC motor, characterized in that the speed control method is performed every 60n_2 electrical degrees as a positive integer. 2. The speed control method for a brushless DC motor according to claim 1, wherein the positive integer n_2 is determined to be a smaller number during low speed rotation than during high speed rotation.