JP3248281B2 - Rotation control method of sensorless multi-phase DC motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation control method for a sensorless multi-phase DC motor, and more particularly to a technique for increasing torque during rotation and avoiding a start dead center.

[0002]

2. Description of the Related Art A brushless multi-phase DC motor has been conventionally used as a motor for rotating a magnetic disk drive. This type of motor is also called a spindle motor, and includes, for example, a stator provided with a stator coil that generates a magnetic field in an excited state, and a rotor provided with a rotor magnet that obtains rotational force by electromagnetic interaction with the magnetic field of the stator coil. , A structure having a sensor for detecting the rotational position of the rotor magnet is well known,
In a spindle motor having such a structure, in many cases,
Rotation control is performed by an electronic circuit formed into a semiconductor chip.

In this case, the timing of the generation of the magnetic field on the stator side is controlled by detecting the rotational position of the rotor magnet by a sensor, and a Hall element has been conventionally used for this type of sensor. However, recently, in order to avoid downsizing of the motor and deterioration of sensor characteristics, the position of the rotor magnet is detected using the induced voltage (or induced current) generated in the coil at rest without using the sensor. The so-called sensorless multi-phase DC motor is becoming popular.

[0004] When the sensorless motor is started, when the motor is stopped, a back electromotive force cannot be obtained, so that the rotor is first swung. For example, in a three-phase coil spindle motor, a step of sequentially supplying an exciting current to a stator coil is repeated, and during this step,
Normally, the method includes a step of passing an exciting current in a forward direction, a rest, and a reverse direction to each phase, and a magnetic field generated by flowing an exciting current of a predetermined pattern including such steps and a rotor magnet. The driving torque is generated by the suction and repulsive force during the operation, and the motor is started.

On the other hand, when the motor is started, a back electromotive voltage is detected, and the rotation of the motor is controlled based on the detected value. However, such a rotation control method for a sensorless multi-phase DC motor has the following technical problems.

[0006]

That is, in the above-mentioned sensorless multi-phase DC motor, the position of the rotor magnet is detected by the induced voltage due to the magnetic flux linked to the coil. However, when the motor stops, there is no induced voltage. Also,
Since the polarity of the magnet is unknown, it is forcibly started when starting. However, depending on the position of the rotor, start-up failure may occur due to low torque, or a magnetic field due to energization may be generated in the opposite direction, causing a reverse rotation of the mechanical angle of 60 ° or more at start-up.

Therefore, in order to avoid such inconveniences and to enhance the starting reliability, the present applicant has developed a starting control method in which a part of the step is made a double drive system. In this control method, at the time of starting the sensorless motor, the method includes a reverse excitation driving operation in which the energizing direction is reversed from positive to negative or from negative to positive without including the pause time. A large change width of the magnetic flux density is generated, a high torque is generated, and the starting reliability is improved.

However, even in such a double drive system, especially when the positional relationship between the rotor and the stator happens to be at a position where the torque generated by energization is small, that is, at the starting dead center, the starting current is particularly high. If the number is small, there is a problem that the step sequence is repeated in a state where the rotor does not move much. Also, in the control after the motor is started and rotated, generally, the excitation current is sequentially supplied to the multi-phase stator coils. He was also dissatisfied with the torque.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a sensorless multi-phase system capable of sufficiently increasing the torque at the start and eliminating the start dead center. An object of the present invention is to provide a rotation control method for a DC motor.

[0010]

In order to achieve the above object, the present invention provides a method for generating a current magnetic field in an excited state and using a three-phase star.
A stator having a connected stator coil, a rotor having a rotor magnet for obtaining a rotational force by an electromagnetic interaction with a current magnetic field of the stator coil, and a pulse-shaped rotor for rotating the rotor in a predetermined direction. To the two phases of the stator coil and one phase to the reverse excitation.
Negative in the rotation control method of a sensorless polyphase dc motor having a control device for feeding in that state, stepping process for starting the motor, each phase, the energizing direction is positive in substantially free rest period Or a reverse excitation driving operation of reversing from negative to positive , the reverse excitation driving operation being sequentially performed in a plurality of phases, and an internal switch including the reverse excitation driving operation .
A stop period for stopping the supply of the exciting current in all of the plurality of phases after the step is repeated twice is provided.

[0011]

[0012]

According to the rotation control method of the sensorless multi-phase DC motor having the above-described structure, the exciting current in each phase is reversed excitation in which the energizing direction is reversed from positive to negative or from negative to positive without a pause period. Since the reverse excitation drive operation is sequentially performed in a plurality of phases including the drive operation, the reverse excitation drive operation causes a large magnetic flux density change width at the time of startup, and generates a high torque. Further, according to the rotation control method, the stop period in which the supply of the excitation current is stopped in all of the plurality of phases after the internal step including the reverse excitation drive operation is repeated twice is provided. At start-up, resetting to the initial value, in other words, the dead point elimination operation is repeated, and even if it is at the dead point at the first start, at the time of the next start (the next Due to the difference in the magnetic flux density variation width due to the asymmetry of the positional relationship between the rotor and the stator in the reverse excitation driving operation, a dead center is avoided and such operation is continuously repeated during the stepping process.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 1 to 5 show one embodiment of a method for starting a sensorless multiphase DC motor according to the present invention. The starting method shown in FIG. 1 applies the present invention to a three-phase sensorless DC motor. FIG. 1 shows the entire configuration including a motor control device. And a rotor (not shown) that obtains rotational force by electromagnetic interaction with a magnetic field of the stator.

The stator includes three-phase stator coils u,
v, w, each stator coil u, v, w
Are commonly connected at one end. The control device 10 includes a power circuit 10a having one end connected to each of the stator coils u, v, w, a driver circuit 10b having an output connected to the power circuit 10a, and a control unit 10c having an output connected to the driver circuit 10b. And a sequencer 10d connected to the output side of the control unit 10c, and the excitation counter 1
0e and a stepping timer 10f.

The power circuit 10a receives an output signal of a driver circuit 10b which operates based on a command from the control unit 10c, and supplies an excitation current to each of the stator coils u, v, w in a pattern set by an excitation counter 10e. Supply.
The control unit 10c performs startup control of the motor and rotation control after startup. The sequencer 10d receives a control signal from the control unit 10c and sends out an exciting current of a preset step pattern. As shown in FIG. u → w, u → v, w
A pattern of the exciting current in which six internal steps of → v, w → u, v → u, v → w are repeated is set.

The excitation counter 10e receives the signal from the control unit 10c and changes the step pattern of the sequencer 10d based on the signal. For example, when this is set to 1, In the hexadecimal pattern, the exciting current in which the steps are repeated is applied to the driver circuit 10b.
When the excitation counter 10e is set to +2, the excitation current in which the internal steps of,, and are repeated is transmitted in the step pattern shown in FIG.

The step-up timer 10f includes an excitation counter 10e.
Is set individually based on a signal from the control unit 10c. FIG. 3 shows an example of a control procedure executed by the control unit 10c, and FIG. 4 is a time chart of the exciting current in each of the stator coils u, v, w at the time of starting the motor and at the time of steady rotation. It is shown.

In the control procedure shown in FIG. 3, when the control unit 10c operates upon receiving a start signal, first, at step s1.
In step s2, the excitation counter 10e is set to +2. In step s3, the energizing period T, the stop period t, and the number of repetitions n of the step timer 10f are set, and the step of starting is started. In the next step s4, it is determined whether or not the internal step has been repeated twice. If it is determined that this has been repeated twice, the process proceeds to step s5.

In step s5, it is determined whether or not the suspension period t set in step s3 has elapsed. When the period t has elapsed, in step s6, the number n of repetitions of the suspension period is determined, and the number n ends. If so, it is determined in step s7 whether or not it is a zero cross. If it is not zero cross, the process returns to step s2. If it is determined that the zero cross has been made, the stepping process ends and the process in step s8 is terminated. The process proceeds to the acceleration process, and then the motor is operated in a steady state.

When the rotation of the motor is controlled according to the above-described procedure, first, in step s2, the excitation counter 10e is set to +2.
And the energization period is set to T in step s3, so that each stator coil u, v, w has internal steps u → w, w → v, v → u as shown in FIG. Is repeated for a period T, for example, 2 ms.
Only supplied.

When such an exciting current is supplied, in the stator coils u, v, w, the exciting current reverses from negative to positive without a stop period, as indicated by the thick arrows in FIG. The excitation driving operation is performed when the stator coils w, u,
This is performed sequentially in the order of v, whereby a large magnetic flux density change width occurs, a high torque is generated in the stepping step at the time of starting, and the starting probability of the motor is greatly improved, and the starting time is increased. Can also be shortened.

In this embodiment, the stop period t is set in step s3, and the stop period t is provided after the internal steps are repeated twice in steps s4 and s5. As shown in FIG. 4, every time the internal step is repeated twice, a stop period of time t is executed,
The stop period t is set during the reverse excitation driving operation. In this stop period, as is clear from FIG. 4, the supply of the exciting current is stopped in all three phases, and the motor is substantially reset in the stop period.

The stop period t in this case is set to about 5 ms, which is 2.5 times as long as the energization period T is 2 ms, and a period of 500 μs or more is selected. In this way, when the stop period t is provided between the reverse excitation driving operations,
The residual magnetic flux density of the stator core becomes substantially zero, so that the motor repeatedly starts and resets at a high speed at the time of starting. At this point, dead center is avoided due to the asymmetry of the positional relationship between the rotor and the stator.

In other words, since the width of change of the magnetic flux density generated when the current is supplied in one direction and the width of change of the magnetic flux density generated during the reverse excitation driving operation are different, a dead center is avoided.
Such an operation is repeated every reset. Therefore, the starting characteristics of the motor can be improved. In the above embodiments, Te control procedure odor 3, after completion of step proceeds step, the pattern supplying normal excitation current without the inverse excitation driving operation, for example, it is also possible to known unipolar control is there.

The energizing period T and / or the stop period t set in the step s3 do not necessarily have to be set to the same time during the period in which they are repeated. For example, these periods are gradually increased or decreased. It is also possible.

[0026]

As described above in detail in the embodiments,
ADVANTAGE OF THE INVENTION According to the rotation control method of the sensorless multiphase DC motor according to the present invention, the starting effect of the motor is extremely increased, the torque during operation is increased, and an excellent effect that the starting dead center is eliminated is obtained. Can be

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram including a control system of a sensorless multiphase DC motor to which a rotation control method according to the present invention is applied.

FIG. 2 is an explanatory diagram showing an example of an excitation current pattern in an energization step employed in a rotation control method according to the present invention.

FIG. 3 is a flowchart showing an example of a control procedure in the rotation control method of the present invention.

FIG. 4 is a waveform chart showing an example of an exciting current according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 control device 10a power circuit 10b driver circuit 10c control unit 10d sequencer 10e excitation counter 10f stepping timer u, v, w stator coil

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-1-308192 (JP, A) JP-A-4-38190 (JP, A) JP-A-4-281389 (JP, A) JP-A-4-308 304192 (JP, A) JP-A-4-359693 (JP, A) JP-A-5-300787 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 6/20

Claims (1)

(57) [Claims] An electric current magnetic field is generated in an excited state, and a three-phase
A stator having a connected stator coil, a rotor having a rotor magnet for obtaining a rotational force by an electromagnetic interaction with a current magnetic field of the stator coil, and a pulse-shaped rotor for rotating the rotor in a predetermined direction. To the two phases of the stator coil and one phase to the reverse excitation.
Negative in the rotation control method of a sensorless polyphase dc motor having a control device for feeding in that state, stepping process for starting the motor, each phase, the energizing direction is positive in substantially free rest period Or negative
The reverse excitation driving operation is performed in a plurality of phases sequentially, and the supply of the excitation current is performed after the internal step including the reverse excitation driving operation is repeated twice. A rotation period of the sensorless multi-phase DC motor, wherein the rotation period is stopped in all the phases.