JPH10201284A - Controller for brushless dc motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct sine-wave driving in an encodeless manner, by correcting and processing an electrical angle in a section by the average speed of the information of an edge signal, in which the acceleration of the edge signal is obtained actually under constant conditions, and a time until the electrical angle is changed at a fixed angle, and controlling the brushless DC motor. SOLUTION: A motor current signal is transmitted from a current detecting means 4 to an arithmetic processing section 10 for a correction processing means 8, while a pole-place signal is sent from a pole detecting means 5 to the arithmetic processing section 10 and an edge detecting means 6. The edge detecting means 6 detects the edge of a magnetic pole and outputs edge signals, and a counter means 7 measures the intervals of the edge signals by the resolution of a measuring clock. The correction processing means 8 obtains a fixed electrical angle from the pole-place signal by the arithmetic processing section 10, and an electrical angle in the section of the electrical angle is corrected by the average speed of the information of the edge signals, in which the acceleration of the edge signals in the section of the electrical angle is acquired actually under constant conditions, and a time until the electrical angle is changed at a fixed value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a brushless DC motor driven by a sine wave drive system mounted on, for example, an electric moving body.

[0002]

2. Description of the Related Art For example, a hall motor is a kind of a permanent magnet type synchronous motor, and is characterized by detecting a magnetic pole position of a permanent magnet using a Hall sensor and feeding back the same to prevent loss of synchronism. Unlike an AC servo, it is common to drive with, for example, a 120-phase 180 ° conducting three-phase inverter without using a rotary encoder. Like a DC motor, the DC voltage of an inverter or a current / speed is controlled by a chopper of an energized phase, so that it is also called a brushless DC motor. In this case, unlike the AC servomotor, the permanent magnet is often magnetized in a trapezoidal wave, and a torque ripple is generated, for example, every 60 ° when the energized phase is switched. Such a brushless DC motor (permanent magnet type synchronous motor) has a simple structure without brushes and commutator pieces, and is therefore inexpensive, robust, and inexpensive.
It has an excellent feature of maintenance-free, and demand is rapidly increasing. Another advantage is that the moment of inertia of the rotor is reduced.

[0003]

However, sine wave driving is desirable from the viewpoint of torque ripple, harmonic loss, field weakening control, and the like. In that case, a position sensor, for example, a rotary encoder must be used. Further, at present, it is a three-phase bipolar drive, and is generally more expensive than a DC machine.

The present invention has been made in view of the above points, and provides a brushless DC motor control device that estimates a rotor position based on a magnetic pole position signal and enables sine wave driving without an encoder. It is an object.

[0005]

In order to solve the above-mentioned problems and achieve the object, a brushless DC according to claim 1 is provided.
The motor control device includes: a magnetic pole detecting means for detecting a magnetic pole of the brushless DC motor; an edge detecting means for detecting an edge signal of the magnetic pole from a magnetic pole position signal obtained from the magnetic pole detecting means; and a measuring clock for measuring an interval between the edge signals. A predetermined electrical angle is obtained from the magnetic pole position signal, and the correction of the electrical angle in the section of the electrical angle is actually obtained under a constant condition of the acceleration of the edge signal in the section. It is characterized by comprising a correction processing means for performing the average speed of the information of the edge signal and a time until the electric angle changes by a predetermined angle, and a control means for controlling the brushless DC motor based on the corrected electric angle information. And The rotor position is estimated on the basis of the magnetic pole position signal, sine wave drive is possible without encoder, and the structure is simple and inexpensive. In addition, since the acceleration of the edge signal is corrected based on the average speed of the information of the edge signal actually obtained under a constant condition and the time until the electrical angle changes by a predetermined angle, the position error is small even during acceleration / deceleration, so that it is effective. It is a target.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a brushless DC according to the present invention will be described.
The motor control device will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a configuration of a control device for a brushless DC motor. Brushless DC motor 1
Is a type of a hall motor of, for example, a permanent magnet type synchronous motor, and a brushless DC motor 1 drives a load 2. This brushless DC motor 1 does not use a rotary encoder, and has, for example, a 120-phase 18
It is driven by a 0 ° conducting three-phase inverter.

The control device for the brushless DC motor 1 comprises current detecting means 4, magnetic pole detecting means 5, edge detecting means 6, counter means 7, correction processing means 8 and control means 9. The current of the brushless DC motor 1 is detected by the current detecting means 4 and a motor current signal is sent to an arithmetic processing unit 10 provided in the correction processing means 8. The magnetic pole position is detected by the magnetic pole detecting means 5 and a magnetic pole position signal (U, V, W phase signal) is sent to the arithmetic processing unit 10 and the edge detecting means 6. For example, a Hall sensor (not shown) is used as the magnetic pole detecting means 5 to detect and feed back to prevent step-out. The Hall sensor utilizes the Hall effect generated in the semiconductor element for detecting the position of the rotor.

Output of magnetic pole position signal (U, V, W phase signals)
The edge detecting means 6 detects the edge of the magnetic pole and outputs an edge signal. The counter means 7 measures the interval between the edge signals with the resolution of the measurement clock. Correction processing means 8
Obtains a predetermined electrical angle from the magnetic pole position signal by the arithmetic processing unit 10 and corrects the electrical angle in the electrical angle section by determining the information of the edge signal that is actually obtained under a constant condition of the acceleration of the edge signal in the section. The correction is performed based on the average speed and the time until the electrical angle changes by a predetermined angle. However, at low speeds where time cannot be measured, for example, drive is performed in six steps.

The control unit 9 includes a PWM unit 11 and a gate drive unit 12, and controls the drive unit 3 based on the corrected electrical angle information. The driving unit 3 includes a power amplifying unit 13 of an inverter, drives the brushless DC motor 1 based on the corrected electrical angle information, estimates a rotor position based on a magnetic pole position signal, and performs sine wave driving without an encoder. Possible,
The structure is simple and inexpensive. Further, since the correction is performed based on the average speed of the edge signal information actually obtained under a constant condition of the edge signal and the time until the electrical angle changes by a predetermined angle, the position error is small even during acceleration / deceleration.

Next, a structure for estimating the rotor position based on the magnetic pole position signal and enabling encoderless sine wave driving will be described in detail.

FIG. 2 is a flowchart of the electrical angle estimation, and FIG.
FIG. 4 is a diagram for explaining measurement of a magnetic pole position signal. The magnetic position signals (U, V, W phase signals) output from the magnetic pole detecting means are shown in FIG. In order to control the brushless DC motor 1, it is necessary to know an accurate rotor position in order to perform position control. For this purpose, a correction in a 60 ° section is performed. Although this method uses a velocity observer at the research level, practical problems remain, such as establishing the accuracy and identification mechanism of mathematical models. In particular, the opportunity to know the exact position is electrical angle 6
Once at 0 °, the observer gain cannot be increased, and there is a problem in the convergence, so that it is considered impossible to use it. Recently, a method of dividing the 60 ° section into N by hardware has been studied, but it is considered that the method is suitable for driving at a constant speed due to a large error during acceleration. Therefore, means for further expanding the practical area by performing compensation during acceleration based on the sensor cycle using a microcomputer is required. However, it is difficult to estimate without any fixed conditions. In this case, it is assumed that the acceleration in the 60 ° electrical angle section is constant.

Considering an arbitrary 60 ° section, the speed is 60
° Only know the average speed of the section. Now, in FIG. 2, the variables are initialized in step S1, the electric angle is updated in step S2, and the magnetic pole position signals (U,
V, W-phase signal), and the position at the time t has elapsed.

[0014]

In this case, the following equation is established.

[0016]

Although the instantaneous value of the speed is not known,

[0018]

Therefore, the position of the rotor is given by equation (4). Note that this represents the case of two poles, and otherwise represents a value obtained by multiplying the speed / acceleration by the number of pole pairs.

[0020]

However, the acceleration is not always constant and causes an error in position estimation. Assuming that the only cause of this error is the acceleration error,

[0022]

Here, the symbol with an overline indicates a calculated value (estimated value).

[0024]

When the error of the acceleration is obtained based on this Δθ, the equation (8) is obtained. In the next section, the error in the position estimation during acceleration can be reduced by using this error in addition to the acceleration used in the calculation. Is thought to spread.

[0026]

However, when the acceleration is directly obtained by time derivative of the speed when the speed resolution is low, the value often varies unless an averaging process is performed. Therefore, the method of integrating the error is suitable when the value variation is small and the speed resolution is low.

Equations (4), (8), and (9) are calculated using CP
This can be confirmed by making a program at U.
Further, the expression (4) for position estimation can be well realized at an estimation interval of about 50 to 100 μs. The minimum speed is determined by the frequency and bit length of the counter for measuring time.

[0029]

As described above, according to the first aspect of the present invention, the rotor position is estimated on the basis of the magnetic pole position signal, sine wave driving can be performed without an encoder, and the structure is simple and inexpensive. In addition, since the acceleration of the edge signal is corrected based on the average speed of the information of the edge signal actually obtained under a constant condition and the time until the electrical angle changes by a predetermined angle, the position error is small even during acceleration / deceleration, so that it is effective. It is a target.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a control device for a brushless DC motor.

FIG. 2 is a flowchart of electric angle estimation.

FIG. 3 is a diagram illustrating measurement of a magnetic pole position signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Brushless DC motor 5 Magnetic pole detection means 6 Edge detection means 7 Counter means 8 Correction processing means 9 Control means

Claims (1)

[Claims] 1. A magnetic pole detecting means for detecting a magnetic pole of a brushless DC motor, an edge detecting means for detecting an edge signal of a magnetic pole from a magnetic pole position signal obtained from the magnetic pole detecting means, and an interval between the edge signals as a measurement clock. Counter means for measuring with a resolution, and a predetermined electrical angle obtained from the magnetic pole position signal, and correction of the electrical angle in the section of the electrical angle is performed on the edge at which the acceleration of the edge signal in the section is actually obtained under a constant condition. An average speed of signal information, correction processing means for performing the time until the electrical angle changes by a predetermined angle, and control means for controlling the brushless DC motor based on the corrected electrical angle information, Control device for brushless DC motor.