JPH06351289A - Driver for variable reluctance motor - Google Patents

Abstract

PURPOSE:To provide a driver for VR motor in which the current control loop can be processed through current control of only one phase. CONSTITUTION:In a driver for a variable reluctance motor, a current detector R is fixed at a position where the total current, i.e., the sum of currents flowing through the coils ZA, ZB, ZC of the motor, can be detected. The coils ZA, ZB, ZC are then excited phase by phase based on the total current detected by the current detector R thus processing the current loop of each phase such that the total current follows up a current command.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device for a variable reluctance motor (hereinafter referred to as VR motor).

[0002]

2. Description of the Related Art A VR motor comprises a stator having an exciting coil wound around a projecting tooth and a rotor having a projecting tooth. An exciting current is supplied to the exciting coil of the stator to excite the stator projecting tooth, and the stator projecting tooth is excited. This is a motor that draws the protruding teeth of the rotor by the magnetic attraction force generated in the teeth and uses that force as the rotational force of the rotor to drive the rotor to rotate. A switching element for supplying an exciting current to the exciting coil is provided for each phase, and the exciting coil of each phase is excited by rotating the switching element according to the rotation angle of the motor to rotate the rotor. There is.

For example, in the case of a three-phase VR motor of A-phase, B-phase, and C-phase, a diagram showing the rotating state of the VR motor of FIG. 4 and a drive circuit diagram of the conventional three-phase VR motor of FIG. As shown, when the A-phase switching element is closed and the A-phase exciting coil and the DC power source are connected to start energization, the A-phase stator protruding teeth attract the rotor protruding teeth and the rotor rotates by a predetermined angle. Open the switching element of the phase and stop energization. Then, the B-phase switching element is closed to excite the B-phase exciting coil. Similarly, the motor is rotated in one direction by sequentially exciting the A phase, the B phase, and the C phase. In the case of reverse rotation, the motor is rotated in reverse by sequentially exciting the A-phase, C-phase and B-phase.

When the current flowing through each exciting coil of such a VR motor is controlled by the PWM method, it is necessary to configure a drive circuit for each phase independently, and therefore, four switching elements are provided for each phase, or It requires as many diodes as there are two switching elements. Note that FIG. 5 is an example in which a drive circuit is configured using the same number of diodes as two switching elements for each phase.

As described above, since the conventional VR motor drive circuit has a large number of switching elements and diodes, the drive circuit itself is expensive and requires two cables for each phase. Further, there is a problem that the cost becomes higher and the wiring man-hours are required. Then, the applicant of the present application is Japanese Patent Application No. 4-84966.
Set the number of switching elements to "1" for the number N of VR motor phases.
A driving circuit having a sufficient number of (N + 1) is provided.

FIG. 6 is a circuit diagram showing an example of a drive circuit for a three-phase VR motor having the number of switching elements (the number of phases + 1).

In FIG. 6, ZA, ZB, and ZC are impedances of the A, B, and C phase coils of the VR motor,
Q2, Q3 and Q4 are switching elements (transistors) for selectively exciting A, B and C phase coils. Further, Q1 is a switching element that performs a cycle of PWM, and D1, D2, D3 and D4 are diodes. Reference numeral 1 is a rectifier circuit that rectifies a three-phase AC of R, S, and T to generate a DC voltage (main voltage) V, and C1 is a smoothing capacitor. Currents ia, ib, i flowing in the coils
A current detector is provided to detect c.
In the above example, the current detection resistors Ra, Rb, Rc are shown as being detected by the current detection resistors. Note that it
Is a total current obtained by summing the currents ia, ib, and ic flowing in each coil, and is represented by it = ia + ib + ic.

In the above structure, the driving of the VR motor, that is, the excitation of the coil will be described by taking the excitation of the A-phase coil as an example.

(1) When a positive voltage is applied to the A phase coil to increase the A phase current ia: The A phase switching element Q2 is turned on and the other phase switching elements Q3 and Q4.
Is turned off and the switching element Q1 is turned on / off by the PWM signal, when the switching element Q1 is turned on, the current ia flows in the order of Q1 → Ra → ZA → Q2, and the voltage V is applied to the A-phase coil. The current ia increases.

On the other hand, when the switching element Q1 is turned off, the energy accumulated in the coil of phase A causes D1
The current ia flows in the order of → Ra → ZA → Q2, the voltage “V” is applied to the A-phase coil, and the current ia decreases. Therefore, if the duty ratio of the PWM signal for turning on / off the switching element Q1 is ηa, the average voltage applied to the A phase is (ηa × V).

(2) When a negative voltage is applied to the phase A coil to reduce the phase current ia of the phase A: All the switching elements Q2, Q3, Q4 of the phases A, B, C are turned off.
When the switching element Q that is switched by the PWM signal is on, the current ia flows in the order of Q1 → Ra → ZA → Q2, and the voltage “0” is applied to the A-phase coil. Also,
When the switching element Q1 is off, the current ia is D
1 → Ra → ZA → D2, the voltage of “−V” is applied to the coil of phase A, the current ia decreases, and the average voltage applied to the coil of phase A is (1-ηa ) ×
(-V).

By the operations (1) and (2), the A-phase exciting current ia is controlled by the PWM signal so as to follow the command current iscmd during the A-phase exciting period. When the motor rotates and the excitation phase changes to the B phase, the switching element Q2 turns off and the switching element Q3 turns on.
In the B-phase excitation, the only difference is that the role of the switching element Q2 in the case of the A-phase excitation replaces the switching element Q3, and the operations of the switching elements Q1 and Q3
The relationship of the voltages applied to the phase coils is the same as in the case of the A phase. Similarly, when the motor rotates and becomes C-phase excitation, the switching element Q2 at the time of A-phase excitation only replaces the switching element Q4, and the operation and the voltage applied to the C coil are the same.

FIG. 7 is an explanatory diagram for explaining the relationship between the coil currents ia, ib, ic of each phase and the command current iscmd in this drive circuit. In the case of A-phase excitation as shown in FIG. 7A, The A-phase current ia rises by the duty ratio ηa of the PWM signal determined by the current deviation of the difference between the command current iscmd and the A-phase current ia, and is controlled so as to follow the current command iscmd. Then, when switching to B-phase excitation, as shown in FIG. 7B, the B-phase current ib is the B-phase current ib, the B-phase current ib is the current command icmd, and the detected B-phase current ib.
Is controlled by the duty ratio ηb which is determined by the current deviation of the difference between the current and the current command iscmd.

Immediately after the start of B-phase excitation, the switching element Q2 is off, so that the average voltage applied to the A-phase coil is (1-.eta.
b) × (−V), the A-phase current ia decreases and becomes 0 after a certain time tab after the excitation phase is switched. This A
In the excitation switching section tab from the phase B to the phase B, the total current flowing through the motor is a current obtained by adding the falling current of the A phase to the current ib of the B phase.

[0015]

The above-mentioned conventional VR motor drive device has the following problems.

(1) Since the currents of the respective phases are independently detected and controlled, a current control loop process of a plurality of phases is required in the portion where the excitation sections of the phases overlap in the excitation switching section or the like. A certain amount of calculation is required for each current control loop process, and the amount of calculation increases because current control of a plurality of phases is performed simultaneously. Further, generally, when a motor is driven by a digital servo, it is necessary to shorten the sampling cycle in order to obtain good performance, but in order to process a large amount of calculation in a short time, a high processing speed and high cost are required. MPU is required.

(2) In the drive circuit of the VR motor (the number of phases +
When the drive circuit controlled by the switching element of 1) is used, in the conventional method, a current detector for detecting the current of each phase must be provided for each phase, and the current detection means, etc. Required for each.

It is therefore an object of the present invention to provide a VR motor driving device that enables current control loop processing by current control of only one phase and reduces the number of current detectors.

[0019]

In order to achieve the above object, the present invention provides a drive device for driving a variable reluctance motor, in which current detection is performed at a position where the total current obtained by summing the currents flowing through the coils of the motor can be detected. A coil is attached and each coil is excited one phase at a time based on the total current detected by the current detector, so that the current loop processing for each phase is performed so that the total current follows the current command.

In order to achieve the above object, the present invention is a drive device for driving a variable reluctance motor, wherein one end of a diode is connected to a negative terminal of a DC power supply for power supply and the other end is connected to a switching element. , A common series circuit in which the other end of the switching element is connected to the positive terminal of the DC power supply, one end of the switching element is connected to the negative terminal of the DC power supply for power supply, the other end is connected to the diode, and the target of the diode Is connected to the positive terminal of the DC power supply, a series circuit provided for each phase, and one end is connected to the connection point of the switching element and the diode of the series circuit for each phase and the corresponding excitation coil of the variable reluctance motor, The other end is driven by one current detection circuit connected to the connection point of the switching element and the diode of the common series circuit. The circuit is configured, means for detecting the electrical angle of the rotor, means for determining the phase to be excited using the electrical angle, controlling the switching element corresponding to the excitation phase, and the detection current of the drive circuit The motor is driven by means for controlling the voltage of the motor coil so as to match the command current.

[0021]

According to the present invention, in the drive device for driving the variable reluctance motor, the current flowing in each coil of the motor is detected by the current detector installed at a position where the total current summing the currents flowing in each coil of the motor can be detected. The total current detected by the current detector is detected, and each coil is excited one phase at a time based on the total current detected by the current detector, and the current loop processing for each phase is performed so that the total current follows the current command. The current loop processing can be performed in only one phase even when switching the excitation phase.

According to the present invention, in the drive device for driving the variable reluctance motor, one end of the diode is connected to the negative terminal of the DC power supply for power supply, the other end is connected to the switching element, and A common series circuit whose end is connected to the positive terminal of the DC power supply, and one end of the switching element is connected to the negative terminal of the DC power supply for power supply, the other end is connected to the diode, and the target of the diode is the positive terminal of the DC power supply. A series circuit provided for each phase, one end of which is connected to a connection point of the switching element and the diode of the series circuit of each phase and a corresponding excitation coil of the variable reluctance motor, and the other end of which is connected to the common series. A drive circuit is composed of a switching element of the circuit and one current detection circuit connected to the connection point of the diode. Excitation of each coil of the motor by means of the rotor electrical angle obtained from the means for detecting the total electrical current that sums the currents flowing in each coil of the motor through one current detection circuit of the motor circuit By determining the phase to be controlled, controlling the switching element corresponding to the excitation phase, by controlling the voltage of the motor coil so that the detected current of the current detection circuit matches the command current,
Drives the motor.

[0023]

Embodiments of the present invention will now be described in detail with reference to the drawings, but the present invention is not limited to the embodiments.

(Structure of Embodiment) FIG. 1 is a circuit diagram of a VR motor drive circuit according to an embodiment of the present invention.

A comparison between the conventional VR motor drive circuit shown in FIG. 6 and the circuit of the present invention shown in FIG. 1 is that there is only one current detector (indicated by a current detection resistor R in the figure). , The total current it added with the currents flowing in the respective phases is detected by the current detector R.

In FIG. 1, in the current detector R, one end of the diode is connected to the negative terminal of the DC power supply for power supply, the other end is connected to the switching element, and the other end of the switching element is the positive electrode of the DC power supply. One end is connected to the connection point of the switching element and the diode of the common series circuit connected to the terminal, and the other end is connected to each exciting coil ZA, ZB, ZC. Therefore, with this configuration, the current flowing through each exciting coil ZA, ZB, ZC is
, The total current it can be obtained by adding the currents flowing in the respective phases by the current detector R.

The hardware configuration of the control means for controlling the VR motor drive is the same as that of the conventional processor,
It is composed of a ROM, a RAM, an input / output circuit and the like, and the processing executed by the processor of this control means is different from the conventional one. The hardware configuration of this control means is
Not shown because it is well known.

(Operation of Embodiment) FIG. 2 is a flow chart of the current loop processing executed by the processor of the control means of one embodiment of the present invention. The processor of the control means executes the processing shown in FIG. carry out. Hereinafter, description will be given according to the reference numeral of step S in the flowchart of FIG.

Step S1: First, the current command icmd is read and the total current it is detected by the current detector R.
Is read, and the rotor electrical angle θ is detected and read by a detector that reads the rotor position of the motor. FIG. 3 is an explanatory diagram of each phase current and total current according to an embodiment of the present invention, and the total current it is detected by the current detector R.

Step S2: Next, the current command icmd read in the step S1 is compared with the read total current it.

Step S3: Next, in the comparison step of the step S2, the total current it is the current command icmd.
In the following cases, the total current it from the current command iscmd
The current deviation (icmd-it) obtained by subtracting is multiplied by the set current loop proportional gain K and further divided by the main voltage equivalent value V which is the output of the rectifier circuit to obtain the duty ratio η of the PWM signal. That is, the duty ratio η is obtained by performing the calculation of the following equation (1).

Η = (K / V) (icmd −it) (1) Then, by controlling the switching element by the PWM signal of this duty ratio η, the total current it is increased to follow the current command icmd. Let

Step S4: On the other hand, in the comparison step of Step S2, the total current it is the current command icmd.
If the duty ratio exceeds the duty ratio η of the PWM signal
Is calculated by the following equation (2).

Η = 1 + (K / V) (icmd −it) (2) Then, by controlling the switching element by the PWM signal of this duty ratio η, the total current it is reduced to the current command icmd. Make them follow.

Steps S5 and 6: Next, the step S
From the rotor electrical angle θ read in step 1, the A phase excitation phase,
Either the B-phase excitation phase or the C-phase excitation phase is determined. Then, in the case of the A phase excitation phase, step S7
If it is the B phase excitation phase, proceed to step S8
In the case of the phase excitation phase, the process proceeds to step S9. Each step S
In the steps 7, 8 and 9, the current command iscmd read in the step S1 is compared with the total current it read and the switching element Q1 / Q
4 is turned on and off.

Steps S7, 8: When the excitation phase is the A phase, and when it is determined that the detected total current it is smaller than the current command icmd in the step S7, the total current it is increased to increase the current. In order to follow the command icmd, it is necessary to perform the operation of the above equation (1).

In FIG. 1, the switching element Q2 corresponding to the phase A is turned on and the switching element Q1 is turned on.
The PWM signal for turning on / off the duty ratio η obtained in the process of step S3 is output, and the other switching elements Q3 and Q4 are turned off to increase the A-phase current and increase the total current it. At this time, the voltage applied to the A-phase coil is the main voltage V which is the output of the rectifier circuit 1 when the switching element Q1 is on, and becomes "0" when the switching element Q1 is off, as described above. . Therefore, the average voltage applied to the A-phase coil is expressed by the following equation (3).

Average voltage = η × V = (K / V) (icmd-it) × V = K (icmd-it) (3) Steps S7 and 9: On the other hand, when the excitation phase is the A phase, , Total current it detected in step S7
Is determined to exceed the current command icmd,
In order to decrease the total current it and follow the current command icmd, it is necessary to perform the operation of the above-mentioned formula (2).

In FIG. 1, a PWM signal for turning on / off the switching element Q1 at the duty ratio η obtained in the step S4 is output, and the other switching elements Q2, Q3, Q4 are turned off, and the A-phase current is changed. To reduce the total current it. In this case, as described above, when the switching element Q1 is on, the voltage applied to the A-phase coil is "0", and the switching element Q1
When 1 is off, "-V" will be applied. Therefore, the average voltage applied to the A-phase coil is represented by the following equation (4) based on the duty ratio η obtained in the step S4.

Average voltage = (1−η) × V = − (K / V) (icmd −it) × (−V) = K (icmd −it) (4) Formula (3) and Formula (4) ), The average voltage applied to the A-phase coil is obtained by multiplying the voltage deviation obtained by subtracting the total current it from the current command iscmd by the proportional gain K regardless of whether the total current it is less than or equal to the current command iscmd. It becomes a value, and it can be seen that the proportional control is executed so that the total current it follows the command current iscmd.

Steps S10, 13: If the exciting phase is judged to be the B phase or the C phase in the step S6,
The same process as the process of step S7 in the A phase is executed.

Steps S11, 14: The current command icmd is compared with the total current it. When the current command icmd is large, in the case of B-phase excitation, switching element Q3 is turned on, switching elements Q2 and Q4 are turned off, and C-phase excitation is performed. In the case of, the switching element Q4 is turned on, the switching elements Q2 and Q3 are turned off, and the switching element is set to step S.
Switching is performed with the PWM signal having the duty ratio η obtained in the process of 3. And the PWM of this duty ratio η
By controlling the switching element by the signal, the total current it is increased to follow the current command iscmd.

Steps S12, 15: In addition, the current command i
When the total current it is larger than cmd, as in step S9, the switching elements Q2, Q3 and Q4 are
Is turned off and the switching element Q1 is switched at the duty ratio η obtained in the step S4. Then, by controlling the switching element with the PWM signal of this duty ratio η, the total current it
Is made to follow the current command iscmd.

By carrying out the above-mentioned processing every predetermined period, the excitation phase having a value obtained by multiplying the current deviation (icmd-it) which is the difference between the current command icmd and the detected total current it by the proportional gain K of the current loop. Is applied to control the total current it to follow the current command icmd.

(Effect of Embodiment) Compared to the case where a plurality of phases are controlled at the same time, the amount of calculation processing is small, and even with the same sampling cycle, processing can be performed by the MPU having a low calculation speed. In addition, current detection means, AD converter,
The number of isolation amplifiers and the like can be reduced.

(Modification of Embodiment) As the current detector, it is possible to use an element such as a photocoupler for converting a current signal into another signal form, instead of the current detection resistor R shown in the embodiment.

[0047]

As described above, according to the present invention,
Since the total current of each coil of the motor is detected and the current is controlled by the total current, the current control loop process can control the current of only one phase, and the number of current detectors can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a VR motor drive circuit according to an embodiment of the present invention.

FIG. 2 is a flowchart of a current loop process executed by the processor of the control means according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram of each phase current and total current according to an embodiment of the present invention.

FIG. 4 is a diagram showing a rotating state of a VR motor.

FIG. 5 is a drive circuit diagram of a conventional three-phase VR motor.

FIG. 6 is a drive circuit diagram of a conventional three-phase VR motor.

FIG. 7 is an explanatory diagram illustrating a relationship between a coil current and a command current in a drive circuit of a conventional three-phase VR motor.

[Explanation of symbols]

 1 rectifier circuit Q1 to Q4 switching element D1 to D4 diode ZA A phase impedance ZB B phase impedance ZC C phase impedance R current detector current detection resistance ia A phase current ib B phase current ic C phase current it total current

Claims (2)

[Claims] 1. A drive device for driving a variable reluctance motor, wherein a current detector is attached at a position where a total current obtained by summing the currents flowing through the coils of the motor can be detected, and the total current detected by the current detector is A variable reluctance motor drive device characterized by performing current loop processing for each phase so that the total current follows the current command by exciting each coil based on each phase. 2. In a drive device for driving a variable reluctance motor, (a) one end of a diode is connected to a negative electrode terminal of a DC power supply for power supply, the other end is connected to a switching element, and the other end of the switching element is DC. A common series circuit connected to the positive terminal of the power supply, and (b) one end of the switching element is connected to the negative terminal of the DC power supply for power supply, the other end is connected to the diode, and the target of the diode is the positive terminal of the DC power supply. And (c) one end is connected to the connection point of the switching element and the diode of the series circuit for each phase and the corresponding exciting coil of the variable reluctance motor, and the other end is connected to the series circuit. A drive circuit is configured by the switching element of the common series circuit and one current detection circuit connected to the connection point of the diode; Means for detecting the electrical angle of the rotor; (e) means for determining a phase to be excited by using the electrical angle and controlling a switching element corresponding to the excited phase; and (f) detected current of the drive circuit. Is a drive device for a variable reluctance motor, characterized in that the motor is driven by a means for controlling the voltage of the motor coil so as to match the command current.