JP2000041389A - Electric motor control method and controller thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric motor controller which can linearly change the duty ratio of drive current given to an electric motor from a DC source through an inverter circuit, without being affected by the operation delay time of the switching element of the inverter circuit. SOLUTION: A command signal generation part 4 is constituted so that command signals Vu-Vw given to switching elements Su-Sw on the upper side of the bridge of an inverter circuit 2 from the command signal generation part 4, and command signals Vx-Vz given to switch elements Sx-Sz at the lower side of the bridge of the inverter circuit 2, are set to be rectangular signals which discontinue at a prescribed duty ratio; and a period when the on-command period of the command signals Vu-Vw is overlapped with the on command period of the command signals Vx-Vz is set to be a period, when drive current is made to flow to an electric motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control method for controlling a drive current of a motor such as a brushless DC motor using an inverter circuit, and to a control device used for implementing the control method.

[0002]

2. Description of the Related Art A motor control device for controlling the drive current of a motor such as a brushless DC motor using an inverter circuit is configured as shown in FIG. 1, for example. In FIG. 1, 1 is a DC power source such as a battery, 2 is a three-phase bridge type inverter circuit, 3 is a motor having three-phase armature coils connected in a star or triangle connection, 4 is a command signal generator, 5
Is a switch drive circuit.

In the illustrated inverter circuit 2, upper and lower sides of a bridge circuit are respectively constituted by three upper side switch elements Su, Sv and Sw and three lower side switch elements Sx, Sy and Sz. , A pair of input terminals 2
a, 2b are connected to the output terminals of the DC power supply, and three output terminals 2u, 2v, and 2w are connected to the three-phase input terminals 3 of the electric motor 3.
u, 3v and 3w. Switch element Su
Sw and Sx to Sz are semiconductor elements, such as transistors and FETs, that can be turned on / off by the level of a drive signal.

The command signal generator 4 includes rectangular wave command signals Vu to Vw for determining a period during which each of the switch elements Su to Sw and Sx to Sz of the inverter circuit 3 is turned on and a period during which each switch element is turned off. In the illustrated example, the command signals Vu to Vw and Vx to Vz are generated during an ON command period for instructing each of the switch elements Su to Sw and Sx to Sz to be in an ON state.
Are at a high level, respectively, and the switch elements Su ~
Command signals Vu to Vw and Vx during an off command period for commanding to turn off each of Sw and Sx to Sz.
To Vz are each at a zero level.

[0005] The command signal generating section 4 does not short-circuit the DC power supply 1 in order to commutate the current to the three-phase armature coils of the motor 3 in a predetermined order and rotate the rotor in a predetermined direction. (Switch elements S connected in series with each other
u, Sw-Sw, and Sz are not turned on at the same time), while taking into consideration one of the switching elements Su-Sw on the upper side and the switching elements Sx-S on the lower side of the inverter circuit 2.
The command signal corresponding to each switch element is changed so that one of Sz is combined with the other in a predetermined order to turn on.

[0006] The command signal generating section 4 also provides a predetermined command signal to each of the upper switch elements in order to control the rotational speed and the like of the motor by PWM controlling the drive current flowing through the motor through each switch element. A command signal given to a lower-side switch element to be turned on together with each upper-side switch element as a rectangular-wave-shaped signal intermittently (pulse-width-modulated) at a duty ratio is supplied to the motor through the lower-side switch element. It is a signal of a constant level that is not interrupted during the energization period.

[0007] The switch drive circuit 5 includes command signals Vu to V
switch elements Su to Sw on the upper side and switch elements Sx to S on the lower side of the inverter circuit 2 according to w and Vx to Vz.
drive signals Vu 'to Vw' and Vx 'to Vz
′, These drive signals Vu ′ to Vw ′ and Vx ′ to Vz ′ correspond to the corresponding command signals Vu to Vw and V
Signals having the same waveform as x to Vz.

If the motor 3 is a three-phase brushless DC motor, the combination of the switch elements Su to Sw and Sx to Sw which are simultaneously turned on depends on the rotational angle position of the rotor, for example. (Su, Sy),
(Su, Sz) (Sv, Sz), (Sv, Sx), (S
w, Sx), (Sw, Sy), (Su, Sy),...

FIG. 6 shows a conventional motor control device having the configuration shown in FIG. 1, in which the combination of switch elements that are simultaneously turned on is (Su, Sy), that is, the positive side of the DC power supply 1. After the pulse-width-modulated (intermittent at a predetermined duty ratio) waveform drive current flows into the U-phase armature coil through the switch element Su,
In a section in which the drive current is caused to flow out of the V-phase armature coil and returned to the negative terminal of the DC power supply through the switch element Sy, the command signal generator 4 generates the command signals Vu and Vy generated for the switch elements Su and Sy, respectively. And ON / OFF operations of the switch elements Su and Sy when these command signals Vu and Vy are generated.

In the example shown in FIG. 6, command signals Vu and V
The period during which y is at the high level is the ON command period Ton for instructing the switching elements Su and Sy to be in the ON state, and the period during which the command signals Vu and Vy are at the zero level is the switching element Su. And an off command period Toff for commanding Sy to be turned off.

As shown in FIG. 6, in the conventional motor control device having the configuration shown in FIG. 1, the switch element Su on the upper side and the switch element Sy on the lower side are simultaneously turned on, and the U-phase armature of the motor is turned on. When a drive current having a PWM waveform (pulse width modulated waveform) flows through the coil and the V-phase armature coil, a command signal Vu for the switch element Su on the upper side is intermittently interrupted at a predetermined duty ratio (FIG. 6A), and an energizing period in which a command signal Vy for the lower switch element Sy is supplied through both switch elements (a period in which a drive current flows through the U-phase armature coil and the V-phase armature coil through the switch elements Su and Sy). ), Drive signals Vu ′ and Vy ′ having the same waveform as these command signals are used as the signals (FIG. 6C) to maintain a constant level. And Sy control terminals.

The switch drive circuit 5 supplies drive signals Vu 'and Vy' to the switch elements Su and Sy at the same time that the command signals Vu and Vy are generated.
And Sy have an element-specific delay, so that the switching elements Su and Sy cannot perform on / off operations in the same phase as the command signals Vu and Vy, and a predetermined delay time with respect to the command signals Vu and Vy. On / off operation is performed with τ.

FIG. 6E shows a drive current I flowing through the motor 3.
The driving current I flows through the U-phase and V-phase armature coils while the switch elements Su and Sy are simultaneously turned on, as is apparent from FIG. In FIG. 6, the waveform shown by the solid line shows the case where the duty ratio of the drive current is 50%, and the waveform shown by the broken line shows the case where the duty ratio is smaller than 50%.

In the section where the drive current flows through the armature coils of the other phases of the motor 3, the waveforms of the signals applied to the upper and lower switch elements of the inverter circuit 2 are the same as described above.

[0015]

In the conventional motor control device, when the drive current is controlled by PWM, only a command signal given to the switch element on the upper side of the inverter circuit 2 is intermittently switched at a predetermined duty ratio. As shown in FIG. 7, in order to reduce the duty ratio of the driving current, the on-command period of the command signal given to the upper switch element is set to the operation delay time τ of the switch element as shown in FIG.
When it is smaller than the above, the upper switch element (Su in the illustrated example) cannot be turned on. Therefore, the characteristic of the duty of the drive current with respect to the duty of the command signal (the ratio of the ON command period to the period of the sum of the ON command period Ton and the OFF command period Toff) is as shown in FIG. There is a problem that the duty of the drive current cannot be controlled from zero, and there has been a problem that the control of the motor in an extremely low speed region and a light load region cannot be accurately performed.

In the above-described example, a case is shown in which three-phase armature coils are provided. In general, a motor having n-phase (n is an integer of 2 or more) armature coils is subjected to PWM control through an n-phase bridge type inverter circuit. In this case, the same problem as described above occurs.

An object of the present invention is to allow the duty ratio of the drive current of the motor to be changed linearly from zero, so that the motor can be accurately controlled in the extremely low speed range and the light load range. An object of the present invention is to provide a motor control method as described above and a motor control device used for implementing the control method.

[0018]

The motor control method according to the present invention comprises a DC power supply, n upper (n is an integer of 2 or more) switch elements on and off controlled by a drive signal, and n lower switch elements. An upper side and a lower side of a bridge circuit are respectively constituted by switch elements, and a pair of input terminals are connected to output terminals of the DC power supply, and n output terminals of the motor have n-phase armature coils. An n-phase bridge type inverter circuit connected to the input terminals;
A command signal generator for generating a command signal having an ON command period for instructing each switch element of the inverter circuit to be in an ON state and an OFF command period for instructing each switch element to be in an OFF state; In accordance with this method, a drive signal is applied to the upper and lower switch elements of the inverter circuit in response to the drive signal, so that a drive current having a pulse width modulated waveform is supplied to the motor to control the rotation of the motor.

In the present invention, both the command signal given to each upper-side switch element of the inverter circuit and the command signal given to each lower-side switch element of the inverter circuit have an ON command period and an OFF command period of a predetermined duty. As a rectangular wave signal alternately appearing at a different ratio, a drive current is supplied to the motor during an overlapped ON command period in which the ON command periods of the command signals given to the upper switch element and the lower switch element that are simultaneously turned on overlap. The duty ratio of the drive current supplied to the motor is changed by changing the overlap-on command period.

The control device used to carry out the above control method includes a DC power supply, n switch elements on and off (n is an integer of 2 or more) on the upper side and n lower switches on and off controlled by a drive signal. Elements form upper and lower sides of a bridge circuit, respectively. A pair of input terminals is connected to an output terminal of the DC power supply, and n output terminals have n input terminals of a motor having an n-phase armature coil. An n-phase bridge type inverter circuit connected to a terminal, and a command signal having an ON command period for instructing each switch element of the inverter circuit to be in an ON state and an OFF command period for instructing each switch element to be in an OFF state are generated. Command signal generating section,
A switch drive circuit for providing a drive signal to each of the switch element on the upper side and the switch element on the lower side of the inverter circuit in accordance with the command signal.
Both the command signal given to the switch element on each upper side and the command signal given to the switch element on each lower side of the inverter circuit have a rectangular wave shape in which an ON command period and an OFF command period alternately appear at a predetermined duty ratio. As a signal, a command is issued such that an overlapped ON command period in which the ON command periods of the command signals given to the upper side switch element and the lower side switch element that are simultaneously turned on overlaps is a drive period in which a drive current flows through the motor. A signal generator is configured.

With the above arrangement, the duty ratio and / or the phase relationship between the command signal given to the upper side switch element and the command signal given to the lower side switch element are changed to turn on the switch element. The control in the extremely low speed range and the light load range of the motor can be accurately performed by linearly changing the duty ratio of the drive current from zero without being affected by the delay time of the operation and the OFF operation.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic configuration of the hardware of a control device for executing a motor control method according to the present invention is the same as that shown in FIG.

In the present invention, both the command signal given to the switch elements on each upper side of the inverter circuit 2 and the command signal given to the switch elements on each lower side have an on-command period Ton and an off-command period Toff. The electric motor drives an overlap-on command period in which the on-command periods of the command signals given to the upper-side switch element and the lower-side switch element that are simultaneously turned on as a rectangular wave-like signal that alternately appear at a predetermined duty ratio overlap. The command signal generator 4 is configured to be in a drive period in which the current I flows, and by changing the overlap-on command period, the duty ratio of the drive current supplied to the motor is changed to control the rotation of the motor.

As in the present invention, it is assumed that a command signal given to each of the upper side switch element and the lower side switch element which are simultaneously turned on in the inverter circuit is a rectangular wave signal which is intermittent at a predetermined duty ratio. The duty ratio of the drive current can be made zero by setting the command signal given to the upper switch element and the command signal given to the lower switch element to signals of opposite phases.

The upper switch element is changed so as to linearly change the period in which the ON command period of the command signal supplied to the upper switch element and the ON command period of the command signal supplied to the lower switch element overlap. The duty ratio of the drive current can be changed linearly by changing at least one of the ON command period of the command signal given to the switch element and the ON command period of the command signal given to the lower switch element.

FIGS. 2 to 5 show the switching element S on the upper side.
u and the switch element Sy on the lower side are simultaneously turned on, and in the section in which the drive current flows through the U-phase armature coil and the V-phase armature coil, the command signals Vu and Vy given to the switch elements Su and Sy are changed. 5 shows a waveform, an on / off operation of the switch elements Su and Sy, and a waveform of the drive current I. In these examples, the duty ratio of the drive current is changed from 0 to 75%, and the duty ratio [= Ton / (Ton + Toff) of the command signal Vu given to the switch element Su on the upper side of the inverter circuit.
)] Is 75%.

Switch elements Su to Sw and Sx to Sz
Means that even if the command signals Vu to Vw and Vx to Vz enter the ON command period and the OFF command period, the ON operation and the OFF operation cannot be performed immediately, and the command signal enters the ON command period and the OFF command period. After that, when a certain delay time τ elapses, the ON operation or the OFF operation is performed. The delay time of the ON operation and the delay time of the OFF operation of each switch element can be considered to be substantially equal.

FIG. 2 shows a case where the duty ratio of the drive current is set to zero. In this case, the command signal Vy applied to the lower switch element Sy is a signal having a phase opposite to that of the command signal Vu.

FIG. 3 shows that the duty ratio of the drive current is 2
In this case, the command signal Vu given to the switch element Su on the upper side and the command signal Vy given to the switch element Sy on the lower side are ４ of one cycle.
The rising position of the command signal Vy given to the lower switch element is advanced so that the periods overlap.

FIG. 4 shows that the duty ratio of the drive current is 5
In this case, the command signal Vu given to the switch element Su on the upper side and the command signal Vy given to the switch element Sy on the lower side are ２ of one cycle.
The rising position of the command signal Vy given to the lower switch element is advanced so that the periods overlap.

FIG. 5 shows that the duty ratio of the drive current is 7
In this case, the command signal Vu given to the switch element Su on the upper side and the command signal Vy given to the switch element Sy on the lower side have the same phase.

As described above, the period in which the on-command period of the command signal given to the upper switch element and the on-command period of the command signal given to the lower switch element overlap each other is defined as the drive period of the motor (the period in which the drive current flows). When the command signal is generated from the command signal generator 4 so that
The duty ratio of the drive current is linearly changed from zero by appropriately changing at least one of the duty ratios of the command signal given to the upper switch element and the command signal given to the lower switch element. Since the characteristic of the duty ratio of the drive current with respect to the duty ratio of the command signal linearly extends from zero as shown in FIG. 8B, the control at the time of extremely low speed and light load of the motor can be accurately performed. Can be done.

[0033]

As described above, according to the present invention, the ON command period of the command signal given to the upper switch element and the ON command period of the command signal given to the lower switch element overlap each other. Since the drive current is applied to the motor during the period, the duty ratio of the drive current is linearly changed from zero without being affected by the delay time of the ON operation and the OFF operation of the switch element, so that the motor operates in an extremely low speed region and There is an advantage that the control in the light load region can be performed accurately.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a motor control device to which the present invention is applied.

FIG. 2 is a block diagram showing a control device according to the present invention; FIG. 2 is a diagram showing a command signal Vu given by a command signal generator to a switch element on the upper side and switch elements Su and Sy on the lower side of the inverter circuit;
FIG. 4 is a waveform diagram showing the waveforms of V.Y and Vy, the on / off operations of the switching elements Su and Sy, and the waveform of the driving current I when the duty ratio of the driving current is zero.

FIG. 3 is a block diagram showing a control device according to the present invention; FIG. 3 is a diagram showing a command signal Vu given by a command signal generator to a switch element on the upper side and switch elements Su and Sy on the lower side of the inverter circuit;
FIG. 7 is a waveform diagram showing the waveforms of V.Y and Vy, the on / off operations of the switching elements Su and Sy, and the waveform of the drive current I when the duty ratio of the drive current is 25%.

FIG. 4 is a block diagram showing a control device according to the present invention; FIG. 4 is a diagram showing a command signal Vu given by a command signal generator to a switch element on the upper side and switch elements Su and Sy on the lower side of the inverter circuit;
FIG. 7 is a waveform diagram showing the waveforms of V.Y and Vy, the on / off operations of the switching elements Su and Sy, and the waveform of the drive current I when the duty ratio of the drive current is 50%.

FIG. 5 is a block diagram showing a control device according to the present invention; FIG. 5 is a diagram showing a command signal Vu which a command signal generating unit gives to an upper switch element and lower switch elements Su and Sy of an inverter circuit;
FIG. 7 is a waveform diagram showing the waveforms of V.Y and Vy, the ON / OFF operations of the switching elements Su and Sy, and the waveform of the drive current I when the duty ratio of the drive current is 75%.

FIG. 6 shows the waveforms of the command signals Vu and Vy that the command signal generator gives to the upper switch element and the lower switch element Su and Sy of the inverter circuit in the conventional motor control device, and the waveforms of the switch elements Su and Sy. FIG. 3 is a waveform diagram showing an on-off operation and a waveform of a driving current I.

FIG. 7 shows a case where the duty ratio of the drive current is made smaller than the operation delay time of the switch element in the conventional motor control device, and the command signal generation unit includes the upper switch element and the lower switch elements Su and Sy of the inverter circuit.
FIG. 3 is a waveform diagram showing waveforms of command signals Vu and Vy given to the switch, on / off operations of switch elements Su and Sy, and a waveform of drive current I.

FIG. 8A is a diagram showing a relationship between a duty ratio of a drive current and a duty ratio of a command signal in a conventional control device. (B) is a diagram showing a relationship between a duty ratio of a drive current and a duty ratio of a command signal in the control device according to the present invention.

[Explanation of symbols]

1. DC power supply 2. Inverter circuit 3. Electric motor 4.
Command signal generator, 5 ... switch drive circuit, Su to Sw ...
Switch elements on the upper side, Sx to Sz... Switch elements on the lower side.

Claims (2)

[Claims] An upper side and a lower side of a bridge circuit are respectively constituted by a DC power supply, and n (n is an integer of 2 or more) upper-side switch elements and n lower-side switch elements that are turned on / off by a drive signal. An n-phase bridge-type inverter having a pair of input terminals connected to output terminals of the DC power supply and n output terminals connected to n input terminals of a motor having an n-phase armature coil. A circuit, and a command signal generating unit that generates a command signal having an ON command period for instructing each switch element of the inverter circuit to be in an ON state and an OFF command period for instructing each switch element to be in an OFF state, Pulse width modulation is applied to the electric motor by providing a drive signal to each of the upper switch element and the lower switch element of the inverter circuit in response to the command signal. A motor control method for controlling the rotation of the motor by passing a drive current having a waveform formed therein, wherein both a command signal given to each upper side switch element of the inverter circuit and a command signal given to each lower side switch element of the inverter circuit As a rectangular wave signal in which the ON command period and the OFF command period alternately appear at a predetermined duty ratio to the upper switch element and the lower switch element that are simultaneously turned on. An electric motor control method, characterized in that an overlap-on command period in which the periods overlap is a period in which a drive current flows through the motor, and the duty ratio of the drive current applied to the motor is changed by changing the overlap-on command period. 2. An upper side and a lower side of a bridge circuit are respectively constituted by a DC power supply, and n (n is an integer of 2 or more) upper-side switch elements and n lower-side switch elements which are turned on / off by a drive signal. An n-phase bridge-type inverter circuit having a pair of input terminals connected to the output terminal of the DC power supply and n output terminals connected to n input terminals of a motor having an n-phase armature coil. A command signal generating unit that generates a command signal having an ON command period for instructing each switch element of the inverter circuit to be in an ON state and an OFF command period for instructing each switch element to be in an OFF state; A switch driving circuit for supplying a driving signal to each of the switch element on the upper side and the switch element on the lower side of the inverter circuit. In the motor control device that controls the rotation of the motor by passing a pulse-width-modulated drive current to the motor, the command signal generator includes a command signal to be given to a switch element on each upper side of an inverter circuit and a command signal on each lower side. Both of the command signals given to the switch elements are rectangular wave signals in which an ON command period and an OFF command period alternately appear at a predetermined duty ratio, and the upper switch element and the lower switch element that are simultaneously turned on. An electric motor control device characterized in that an overlap-on command period in which the on-command periods of the command signals given to the motors overlap each other is a drive period in which a drive current flows through the motor.