JP3397953B2 - Motor control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device applied to an electric vehicle or the like.

[0002]

2. Description of the Related Art Conventionally, in an electric vehicle such as an electric wheelchair, various control devices have been known for controlling a DC motor according to a speed command from an operating portion.

By the way, in the motor control device for controlling the DC motor by voltage, if the rotation of the motor shaft is forcibly stopped due to sticking of the motor shaft or the like, an excessive motor current flows due to the characteristics of the DC motor. The current value at this time is generally much larger than the current value that is constantly used. Therefore, it is impractical and impractical to equip a control device that allows such an excessive motor current to flow and is not thermally damaged. Further, there is a problem such as burnout of the motor itself when the excessive current flows as described above.

Therefore, limiting the motor current so that an excessive current does not flow has been performed in the past.
Many conventional motor current limiting methods perform processing at the stage of an analog signal. For example, in the case of performing PWM control or chopper control, current limiting is performed at the analog signal level. After processing, the analog signal is converted into a pulse signal.

[0005]

The conventional device of this type has a problem that a circuit and a process for preventing an excessive current from flowing become complicated.

In recent years, the CPU often performs motor control, and in that case, the CPU generally processes the pulse signal. And in such a thing, it is possible to implement | achieve a current limitation by the software processing in CPU. However, in order to reliably limit the current in the internal processing, it is necessary to perform the processing for limiting the motor current in a short time of about several tens of microseconds. Therefore, a high-cost CPU capable of high-speed processing is required. There are problems such as need.

In view of the above circumstances, the present invention can achieve control for limiting the motor current so as not to exceed a specified value by hardware processing of the pulse signal and by a simple circuit configuration. A motor controller is provided.

[0008]

The invention according to claim 1 is
A motor control device that is interposed between a DC motor and a power supply and that controls the amount of power supplied to the motor by changing the time for which the power supply voltage is applied, and a pulse that responds to a command from a speed command operating unit. A pulse generation circuit for generating a motor current detection circuit for converting a current flowing in the motor into a voltage value, a circuit for giving a combined signal obtained by combining the output of the pulse generation circuit and the output of the motor current detection circuit, Compare the synthesized signal with the reference value and respond to the difference.
A comparator for outputting, and a circuit for controlling the energization amount of increase or decrease of the motor according to the output of the comparator, the motor
If the current flowing through is lower than the specified value, the pulse generation circuit
Depending on the on / off switching of the output of
When the output is switched, the current flowing through the motor is
Increased or decreased, when <br/> the current flowing through the motor reaches the specified value, the synthesized signal is reached the reference value, this and
Depending on the output of the comparator,
It is controlled near the specified value .

According to this structure, the electric current flowing through the motor is
If the current is lower than the specified value, the output of the pulse generator circuit is turned off.
The current flowing through the motor repeatedly increases and decreases according to the on / off.
Controlled as.

Further, the current flowing through the motor is a specified value.
When the output reaches the pulse generation frequency,
Independent of the on / off switching of the road output
Switched to control the motor current near the specified value.
Therefore, the current flowing through the motor increases beyond the specified value.
Is prevented. Therefore, in hardware processing
This prevents excessive current from flowing to the motor.
It

In addition, a motor current detection circuit, which is also required for detecting abnormalities in a device for controlling the motor, is used, and a current flowing through the motor is generated based on a combined signal of the output of this circuit and the output of the pulse generation circuit. Due to the restriction of 1), the circuit configuration can be easily maintained.

According to a second aspect of the present invention, there is provided a motor control device which is interposed between a DC motor and a power supply, and which controls the amount of electricity supplied to the motor by changing the time for applying the power supply voltage. A pulse generation circuit that generates a pulse according to a command from the speed command operation unit, a motor current detection circuit that converts a current flowing in the motor into a voltage value, an output of the pulse generation circuit and an output of the motor current detection circuit comparing the door, a comparator for performing an output corresponding to the difference, and a circuit for controlling the energization amount of increase or decrease of the motor according to the output of the comparator, current flowing through the motor is a specified value
If the output is too low , turn the pulse generator circuit output on and off.
The output of the above comparator switches according to the switching
More current increases and decreases to flow to the motor, when the current flowing through the motor reaches the predetermined value, the motor electric
The output of the flow detection circuit is equal to the output of the pulse generation circuit
Value is reached, and the motor is output according to the output of the comparator at this time.
The current flowing through is controlled to be near the specified value .

With this configuration, it is possible to obtain the same operation as that of the above-mentioned claim 1.

A third aspect of the present invention is the invention of the second aspect.
And the comparator outputs the output from the pulse generating circuit and
Combine the output from the analog voltage whose voltage value can be freely changed.
Compare the generated output with the output of the above motor current detection circuit
The current flowing through the motor reaches the specified value.
The motor current detection circuit has the output of the pulse generation circuit.
And the combined output of the above analog voltages
Has reached a certain value, and the motor is output according to the output of the comparator at this time.
The current flowing is controlled to be near the above specified value.
Of.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a drive system of an electric wheelchair as an example of application of the present invention. This electric wheelchair is equipped with left and right drive wheels 1, 1 ′ and left and right DC motors 2, 2 ′ that individually drive these drive wheels via reduction gears 3, 3 ′, while a speed command operation unit is provided. As a result, the passenger operation unit 4 is provided, and the attendant operation unit 5 is also provided.

The occupant operation section 4 is provided with a joystick 4a for commanding the traveling direction and speed, a main switch 4b, an indicator lamp 4c,
4d etc. are provided. The joystick 4a can be tilted in various directions, and a circuit (not shown) including a variable resistor whose resistance value changes according to the tilt of the joystick 4a is incorporated inside the occupant operation section 4. Thus, a signal for speed command corresponding to the operation amount of the joystick 4a is output from the occupant operation unit 4. In addition, the operation section 5 for the attendant has a switch 5a for designating forward and backward movements at a predetermined speed, and a main switch 5
b, indicator lights 5c, 5d, etc. are provided.

Further, in this electric wheelchair, a battery 6,
A main control unit 7, a left motor power control unit 11, a right motor power control unit 11 ', etc. are provided. Main control unit 7
Has a CPU 8, a warning buzzer 9 and the like, and is arranged in a housing 10 below the battery box. The power control units 11 and 11 'are housed inside the left and right wheel hubs 12 and 12'.

Each of the operation sections 4 and 5 is connected to the main control section 7 via a signal line 13 and a connector 15. Also,
For the battery 6, the main control unit 7 and each power control unit 1
1, 11 ′ are connected via the power line 14 and the connector 15, and the respective power control units 11, 11 ′ are connected to the main control unit 7 via the signal line 13 and the connector 15. The motors 2 and 2 ′ are connected to the power control units 11 and 11 ′ via the power line 14 and the connector 15. Further, encoders 16 and 16 'for detecting the rotation speeds of the motors 2 and 2'are provided, and the encoders 16 and 16' are provided to the signal line 13 and the connector 1 respectively.
It is connected to the main controller 7 via 5.

FIG. 2 shows the main controller 7 and the power controller 11 described above.
3 shows a circuit configuration of a control device including the above. In this figure, for simplification of the drawing, only the motor 2 and the power control unit 11 corresponding to the one-side drive wheel are shown.

The main control section 7 has a CPU 8, a control power supply 20, a capacitor C1 for stabilizing the power supply voltage, and a pulse generation circuit 21. Pulse generation circuit 21
Is an FET (field effect transistor) 22 and a resistor R
1, R2, R3, R4, and the FET22
The resistors R3 and R4 are connected between the drain of the control source 20 and the control power source 20, and the gate of the FET 22 is connected to the CPU 8 via the resistor R1 and also connected to the ground side via the resistor R2. .

[0022] The control power supply 20, converts the voltage from the battery 6 to a stable voltage value necessary for the control, in this embodiment, below the driving circuit 32, operates the comparator 31 and the differential amplifier 34 Therefore, a voltage Vcc1 (for example, 12V) necessary for this purpose, a voltage Vcc2 (for example, 5V) necessary for operating the CPU 8 and a voltage V1 applied to the pulse generation circuit 21 are generated.

The CPU 8 receives the speed command signal input from the operation unit 4 through the A / D converter 23 and the signal from the encoder 16 and calculates the PW calculated from these signals.
Outputs M pulse signal. The PWM pulse signal is applied to the gate of the FET 22 via the resistor R1, so that the FET 22 performs a switching operation for switching between the drain and the source between conductive and non-conductive, and a signal corresponding to the switching operation is generated. Resistors R3, R4
It is designed to be output from between.

On the other hand, the power control unit 11 includes relays 25 and 4
FETs 26, 27, 28, 29 and resistors r1, r2
Circuit for energizing the motor 2 provided with a comparator 31 for controlling energization of the motor 2 by this circuit
And a drive circuit 32 and a motor current detection circuit 33 including a differential amplifier 34 and the like.

The relay 25 operates as a CP when a speed command signal corresponding to an operation is input from the operation unit 4 to the CPU 8.
It is turned on by exciting a relay coil (not shown) by U8. Further, the comparator 31 compares both the + side input and the − side input and outputs a high level signal when the + side is large, and outputs a low level signal when the − side is large.
Receives the output signal of the comparator 31 and outputs this signal to each of the above F
The signals are distributed and converted into signals required for ON / OFF operation of the ETs 26 to 29.

In the circuit for energizing the motor 2, F
While ET26 and FET29 are turned on and off at the same time, FET27 and FET28 are turned on and OF at the same time.
F is repeated, and FET26,29 and FET27,
The ON and OFF operations are performed in the opposite manner to 28. When the output of the comparator 31 becomes high level, the FETs 26 and 29 are turned ON by the drive circuit 32, and the output of the comparator 31 becomes low. When it becomes the level, FET27,
28 is turned on. And the FETs 26 and 29 are turned on
In the case of, a path is formed so that the current passes through the FET 26, the motor 2, the FET 29, and the resistor r2.
When is ON, the current is FET28, motor2, FET2
7. A path is formed so as to pass through the resistor r1.

The resistors r1 and r2 are for converting the currents I1 and I2 flowing through the paths into the voltages V3 and V4. The portions for taking out the converted voltages V3 and V4 are resistors R7 and R9. Through the negative side of the differential amplifier 34, +
Is connected to each input terminal on the side. The resistance r1
And the resistance r2 have the same resistance value, the resistances R7 and R9 have the same resistance value, and the resistance r
1 and r2 have resistance values sufficiently smaller than the resistances R7 and R9.

A predetermined voltage V2 is applied to the + side input terminal of the differential amplifier 34 via the resistor R8. The circuit for applying the predetermined voltage V2 is composed of two resistors R10 and R11 having the same resistance value and a capacitor C2. Both the resistors R10 and R11 are connected in series to which a voltage of Vcc1 is applied from a control power source. As a result, a predetermined voltage V2 (= Vcc1 / is generated between the resistors R10 and R11.
2) can be obtained. The capacitor C2
Is for stabilizing the voltage.

Regarding the output voltage V5 of the differential amplifier 34, the resistance value of the resistor R7 is R ₇ , and the resistance value of the feedback resistor R6 is R 5.
_{If we say 6} ,

[0030]

## EQU1 ## V5 = (R ₆ / R ₇ ) × (V4-V3) + V2 ...

The output side of the differential amplifier 34 has a resistor R5.
Output side of the pulse generation circuit 21 (resistors R3, R4
The output of the pulse generation circuit 21 and the output of the motor current detection circuit 33 are combined. Then, this combined signal is the − of the comparator 31.
Input to the side input terminal. Further, the above-mentioned predetermined voltage V2 is applied to the resistor R as a reference voltage at the + side input terminal of the comparator.
It is input via 13. R12 is a feedback resistor.

The operation of the apparatus of this embodiment as described above is
It will be described next.

3 to 6 are for explaining the motor current detection operation, the ON and OFF operations of the FETs 26 and 29 and the corresponding motor voltage Vm, motor current Im, and resistance r1.
Current I1 flowing through the resistor r2, current I2 flowing through the resistor r2, (R ₆
/ R ₇ ) × r 1 × (I 2 −I 1), and the output V 5 of the differential amplifier 34 obtained by adding a predetermined voltage V 2 to this value.

Note that FIG. 3 is for forward power running (when the vehicle is moving forward with the driving force of the motor), and FIG. 4 is for forward regeneration (when the vehicle is in an energy recovery state during downhill or deceleration during forward travel). FIG. 5 is during reverse powering, and FIG. 6 is during reverse regeneration. In these figures, the positive and negative signs of the currents Im, I1, I2 are positive in the directions of the broken line arrows shown in FIG. 2 for the respective currents Im, I1, I2.

As shown in these figures, FETs 26, 2
The motor voltage Vm is switched according to ON / OFF of 9, and the motor current Im fluctuates. Specifically, the motor current Im during forward power running is a positive value and
T26 and 29 fluctuate so as to increase when turned on and decrease when turned off (see FIG. 3), and the motor current Im at the time of forward regeneration has a negative value and the absolute value is O of the FETs 26 and 29.
It changes so that it decreases at N and increases at OFF (Fig. 4).
reference). Further, the motor current Im during reverse powering is
It is a negative value, and the absolute value fluctuates so that it decreases when the FETs 26 and 29 are turned on and increases when they are turned off (see FIG. 5), and the motor current Im during reverse regeneration is a positive value and F
It changes so that it increases when ETs 26 and 29 are on and decreases when they are off (see FIG. 6).

The current I1 is the ON state of the FETs 26 and 29.
Value of the motor current Im when the time is reversed, the current I
2 is the motor current Im when the FETs 26 and 29 are ON
The value is equivalent to. Further, assuming that the resistance values of the resistors r1 and r2 are equal and the value is r ₁ ,

[0037]

[Number 2] _{V3 = r 1 × I1 ... V4} = r 1 × I2 ... it is.

By inputting these voltages to the differential amplifier 34, the voltage proportional to (I2-I1) is amplified. Therefore, on the output side of the differential amplifier 34 to which these voltages and the predetermined voltage V2 are input, the predetermined voltage V
A value depending on the motor current Im centering around 2 is obtained,
Specifically, from the above formulas, the output voltage V5 of the differential amplifier is
But

[0039]

## EQU3 ## V5 = (R ₆ / R ₇ ) × r ₁ × (I2-I1) + V2. The output voltage V5 of the differential amplifier 34 becomes the predetermined value V2 when the motor current is zero.

In order to explain the current limiting operation, FIG. 7 shows the position a (the output portion of the CPU 8) and the position b (the FET in FIG. 2).
22), c position (output part of differential amplifier 34), d position (combined part of output of motor current detection circuit 33 and output of pulse generation circuit 21), e position (comparator 3)
1 output portion).

In this figure, for ease of understanding, it is assumed that the resistor R12 in FIG. 2 is not connected and the resistor R13 is short-circuited. This way,
The comparator 31 has no hysteresis, and the voltage at its + input terminal is kept constant at the above-mentioned predetermined voltage V2. Also,
In the drawing, the signals at the c position and the d position are shown on a larger scale in the vertical axis direction than the other signals in order to make the changes easier to understand.

As shown in the figure, when the PWM pulse signal corresponding to the speed command input is output to the a position on the output side of the CPU 8, the FET corresponding to the PWM pulse signal changes the voltage at the b position of the pulse generating circuit 21. , 0 when FET22 is ON, O
It becomes a value equal to the voltage at the d position during FF. On the other hand, at the position c on the output side of the differential amplifier 34, as described above, the voltage V5 depending on the motor current Im centering around the predetermined voltage V2 is obtained.

The voltage at the d position is the ON state of the FET 22.
Time is determined by the voltages V1 and V5 and the resistance values of the resistors R3, R4, and R5. If the resistance values of the resistors R3, R4, and R5 are equal, [(V1 + V5) / 3] is obtained, while FET2
When 2 is OFF, it is determined by the voltages V1 and V5 and the resistance values of the resistors R3 and R5. If the resistance values of the resistors R3 and R5 are equal, [(V1 + V5) / 2].

By the way, the relationship between the voltages V1 and V2 is set as V2 <V1 <2 × V2.

Under these conditions, before the speed command is input, the motor current Im is 0, so that the voltage (V5) at the c position becomes the predetermined voltage V2, and the FET
Since 22 is OFF, the voltage at the d position has a value between V1 and V2. From this state, the speed command is input and the FET
When 22 is turned on, the voltage at the d position becomes [(V1 + V2)
/ 3], but this value is smaller than V2, and therefore the voltage at the-side input terminal of the comparator 31 is smaller than the voltage at the + side input terminal, so the voltage at position e on the comparator output side is high. It becomes a level. As a result, the motor current begins to flow, so that the voltage (V5) at the position c gradually becomes larger than the predetermined value V2.

Next, when the FET 22 is turned off, the voltage at the d position becomes [(V1 + V5) / 2] and the above predetermined value V
2, the voltage at the negative input terminal of the comparator 31 becomes higher than the voltage at the positive input terminal, and the voltage at the e position on the output side of the comparator 31 is switched to the low level. As a result, the current flowing in the motor 2 is FET2.
It flows to the battery side through the parasitic diode inside 7 and 28, and gradually decreases. Along with this, the voltages at positions c and d also gradually decrease.

As described above, the increase / decrease of the motor current Im and the voltage change at the c position and the d position are repeated according to the ON / OFF of the FET 22, but as the ON time of the FET 22 increases and the motor current Im increases, the motor current Im increases accordingly. When the voltage at the c position and the d position rises and the motor current in the direction of the arrow in FIG. 2 becomes excessively large, so that the voltage at the c position (V5) increases significantly, the voltage at the d position during the ON period of the FET 22 becomes a predetermined value. It reaches the value V2. When this state is reached, the output of the comparator 31 repeats high and low regardless of whether the FET 22 is ON or OFF, and the current Im flowing through the motor 2 is limited.

As described above, when the motor current Im increases to a certain value (specified value), the voltage at the d position corresponding to the combined signal of the output of the pulse generation circuit 21 and the output of the motor current detection circuit 33 is the comparator 31. Predetermined value V2 corresponding to the reference value of
The output of the comparator 31 is regulated by reaching
The motor current Im is limited. Therefore, by selecting the amplification factor of the differential amplifier 34, the motor current Im can be limited to a predetermined value.

In the example of FIG. 7, the current limiting operation is shown when the motor current Im in the direction of the arrow in FIG. 2 increases during forward power running or the like. Even when an excessive motor current Im is about to flow in the opposite direction, the voltage (V5) at the c position decreases, and the voltage at the d position during the OFF period of the FET 22 reaches the predetermined value V2. The effect of limiting the motor current Im is obtained.

In the example shown in FIG. 7, the comparator 3
1 has no hysteresis, and the switching frequency of the FETs 26 to 29 becomes extremely high when the motor current is limited. Therefore, the loss in the FETs 26 to 29 during switching becomes large.

Therefore, it is desirable to provide the comparator 31 with hysteresis. In order to provide the hysteresis, resistors R12 and R13 are provided for the comparator 31 as shown in the circuit of FIG. The value should be set appropriately.

By doing so, the voltages at the positions a to e are as shown in FIG. That is, when the resistors R12 and R13 are provided for the comparator 31, the output side of the comparator 31 (e
The voltage at the + side input terminal of the comparator 31 changes between high and low VH and VL with a predetermined fluctuation width as indicated by the alternate long and short dash line in accordance with the change in position) between high and low. Therefore, when the voltage at the position d exceeds the voltage VH at the + side input terminal of the comparator 31, the comparator 31
As the output side is switched to low, the + side input terminal becomes a low voltage VL, and it takes some time for the voltage at the d position to drop to this voltage VL.
Hysteresis occurs in the switching operation of.

Therefore, by appropriately setting the resistance values of the resistors R12 and R13, the switching frequencies of the FETs 26 to 29 when the motor current is limited can be appropriately lowered.

In the example shown in FIGS. 1 and 2, the comparator 3
1, the current control unit 11 including the drive circuit 32, the motor current detection circuit 33, etc. is provided in the wheel hub 12, so that these are compactly arranged, and the comparator 31, the drive circuit 32, The number of wires between the main controller 7 and the current controller 12 can be reduced as compared with the case where the motor current detection circuit 33 and the like are provided in the main controller 7.

FIG. 9 shows another embodiment of the present invention. In this figure, the main control unit 7 includes a CPU 8, a control power supply 20, and a capacitor C1 for stabilizing the power supply voltage.
A pulse generation circuit 41, an A / D converter 23 for inputting a speed command from the operation unit 4 to the CPU 8, and an A / D converter 36 for converting a signal from the CPU 8 into an analog voltage V11. There is. The pulse generation circuit 41 is FET4
2 and resistors R21, R22, and R23. The voltage V is applied to the circuit in which the resistor R23 is connected to the FET 42.
11, the gate of the FET 42 is connected to the CPU 8 via the resistor R21, and is also connected to the ground side via the resistor R22.

The control power source 20 includes a drive circuit 52, which will be described later.
The voltage Vcc1 required to operate the comparator 51 and the non-inverting amplifier 54, the CPU 8 and the A / D converter 36.
To generate a voltage Vcc2 (for example, 5 V) necessary for operating the.

The CPU 8 outputs a PWM pulse signal calculated from the speed command signal or the like, and this signal is output by the resistor R21.
By being applied to the gate of the FET 42 through the FET 42, the FET 42 performs a switching operation, and a signal corresponding to the switching operation is output from between the drain of the FET 42 and the resistor R23.

On the other hand, the power control unit 11 includes relays 25, F
A motor including a circuit for energizing the motor 2 including the ET 46, the resistor r10 and the diode D1, a comparator 51 and a drive circuit 52 for controlling energization of the motor 2 by this circuit, and a non-inverting amplifier 54 and the like. And a current detection circuit 53.

The comparator 51 compares both the + and-side inputs and outputs a high level signal when the + side is high and a low level signal when the − side is high. In addition, the drive circuit 5
2 receives the output signal of the comparator 51 and outputs this signal to the F
It converts into a signal required for ON / OFF operation of the ET 46, and when the output of the comparator 51 is high level, FE
The drive circuit 52 is configured to turn on T46 and turn off the FET 46 when the output of the comparator 51 is at a low level.

The FET 46 is OF
At the time of F, the diode D1 exists in order to continue to flow due to the induction component (inductance component) of the motor 2 and to supply this current Im. The resistance r10
Is for converting the current Im flowing through the motor 2 into the voltage V12, and the converted voltage V12 is input to the + side input terminal of the non-inverting amplifier 54. The non-inverting amplifier 54 is connected to the negative input terminal of the non-inverting amplifier 54.
An intermediate point of the pair of resistors R24 and R25 connected to the output side of is connected.

The non-inverting amplifier 54 is connected to the voltage V12.
Amplifies the, and the resistance value of the resistor R24, R25 and R _24, R _25, the output voltage V1 of the non-inverting amplifier 54
3 is

[0062]

## EQU4 ## V13 = (1 + R ₂₄ / R ₂₅ ) × V12 ...

The output side of the non-inverting amplifier 54 is connected to the-side input terminal of the comparator 51. On the other hand, the output side of the pulse generation circuit 41 is connected to the + side input terminal of the comparator 51. A resistor R26 is connected between the input side and the output side of the comparator 51.

The operation of the apparatus of this embodiment as described above is
It will be described next.

The motor terminal voltage is equal to the battery voltage when the FET 46 is ON, and 0 when the FET 46 is OFF.
Becomes The motor current Im is equal to the current I11 flowing through the FET 46 when the FET 46 is ON,
When 6 is OFF, it becomes equal to the current I12 flowing through the diode D1. The magnitude of the motor current Im is FET46.
Depending on the ON time, the motor current Im becomes sawtooth-like because it gradually increases when the FET 46 is ON and gradually decreases when the FET 46 is OFF.

[0066] Further, when the resistance value of the resistor r10 and r _10, the voltage V2 caused by the motor current Im flows through the resistor r10 is

[0067]

[Number 5 is a V12 = r ₁₀ × Im .... Then, the output voltage V13 of the non-inverting amplifier 54 the voltage V12 is input, the, from the _{equation, V13 = (1 + R 24} / R 25) × r 10 × Im becomes, in proportion to the motor current Im output is obtained .

FIG. 10 illustrates the current limiting operation.
In FIG. 9, position f (output portion of CPU 8), position g (output portion of pulse generation circuit 41), position h (non-inverting amplifier 5)
4) and the voltage signals at the i position (the output portion of the comparator 51).

As shown in the figure, when the PWM pulse signal corresponding to the speed command input is output to the f position on the output side of the CPU 8, the FET 42 operates in response to the PWM pulse signal, and the g position on the output side of the pulse generation circuit 21. Voltage changes.

That is, the voltage at the g position is
When the FET 42 is on, the voltage is about 0 V, and when the FET 42 is off, the voltage at the i position, the voltage V11, and the resistor R23.
And on the resistance values R _23, R ₂₆ of resistor R26.
Here, the voltage at the i position is the output of the comparator 51, and if the voltage at the high level is VH and the voltage at the low level is VL, then the voltage at the g position when the FET 42 is OFF and the comparator output is VL. The voltage V14L is

[0071]

## EQU6 ## V14L = {R ₂₆ / (R ₂₃ + R ₂₆ ) × V 11} + {R ₂₃ / (R ₂₃ + R ₂₆ ) × VL} ≈ {R ₂₆ / (R ₂₃ + R ₂₆ ) × V 11} (∵VL ≒ 0), and the addition, the voltage V14H the g position when comparator output a time OFF of FET42 is VH is _{V14H = {R 26 / (R} 23 + R 26) × V11} + {R 23 / (R ₂₃ + R ₂₆ ) × VH} ≈V14L + {R ₂₃ / (R ₂₃ + R ₂₆ ) × VH}.

When the speed command is input after the power is turned on, F
The ET 42 is turned off, and the motor current has not yet flown at this point, so the voltage at the h position is 0, and the comparator 5
Since the voltage at the + side input terminal of 1 becomes higher than the voltage at the − side input terminal, the voltage at the i position becomes VH. Next, when the FET 42 is turned on, the voltage at the g position becomes 0, and the motor current has already flowed at this time, so the voltage at the h position is not 0, and therefore the voltage at the + side input terminal of the comparator 51 is − Since the voltage at the side input terminal is higher, the voltage at the i position is VL.

Next, when the FET 42 is turned off, the voltage at the g position instantaneously becomes V14L. However, if the motor current is small and the voltage at the h position does not reach V14L, the voltage immediately becomes i.
The voltage at the position is VH. Below, the voltage at point h is V14
These states are repeated until L is reached.

When the motor current increases as the period in which the voltage at the i position becomes VH increases, the voltage at the h position becomes V14H.
Is reached, the voltage at the i position becomes VL (about 0 V), and the motor current decreases. Then, the voltage at the g position becomes V14L.

In such a case, if the FET 42 is turned on before the voltage at the h position reaches V14L, the voltage at the i position maintains VL. And then F
If ET42 is turned off, the above operation is repeated.

As described above, the voltage at the position g is V14.
When the voltage at the point h reaches V14L before the FET 42 is turned on when the voltage becomes L, the voltage at the point i becomes VH and the motor current starts to increase again.

In this way, when an excessive motor current is about to flow, the output of the comparator 51 repeats high and low, so that the motor current is limited to a certain value (specified value).

In this case, the voltage V11 and the resistors R23 and R2
By appropriately selecting the value of 6 and the amplification factor of the non-inverting amplifier 54, the motor current Im can be limited to a predetermined range, and the switching frequency at that time can be set to a predetermined frequency.

Further, according to this embodiment, the voltage V11 can be freely changed from the CPU 8 side, whereby the current limit value can be set from the CPU 8 side. For this reason, the current limit value is set to a large value when the motor current is temporarily required to be large (for an electric vehicle, for example, when climbing over a step or climbing a hill), and the current limit value remains constant. After the time has passed, the current limit value can be adjusted to lower the current limit value and protect the motor and the control device.

[0080]

The motor control device of the invention according to claim 1 combines the output of the pulse generation circuit and the output of the motor current detection circuit, and based on the comparison of the combined signal in the comparator with the reference value. so as to control the energization amount of increase or decrease of the motor, if current flowing through the motor is lower than the specified value,
Depending on the on / off switching of the pulse generator output
The output of the comparator is switched by the
When the current flowing through the motor increases or decreases and the current flowing through the motor reaches the specified value, the composite signal reaches the reference value.
Depending on the output of the comparator at this time.
Since the current is controlled near the specified value, it is possible to reliably prevent an excessive current from flowing to the motor, prevent burnout of the motor before it occurs, and control the current capacity of the control device and the heat dissipation part. Since it is not necessary to make a large margin such as the heat capacity of the device, the weight and size of the device can be reduced.

Moreover, since the processing is not performed by software in the CPU, high-speed processing is not required of the CPU, and the cost increase of the CPU can be avoided.
In addition, the motor current detection circuit can be used to restrict an excessive current from flowing even with a simple circuit configuration.

Also, in the motor control device of the invention according to claim 2, the output of the pulse generation circuit and the output of the motor current detection circuit are compared by a comparator, and the amount of electricity supplied to the motor is determined according to the output of the comparator. Control the increase and decrease of the
If the flowing current is lower than the specified value, the pulse generator circuit
The output of the above comparator is output according to the switching of the output on / off.
By switching the force, the current flowing through the motor increases.
Hesi, when the current flowing through the motor reaches the predetermined value
The output of the motor current detection circuit is the pulse generation
A value equal to the output of the path is reached, at which time the output of the comparator
Depending on the force, the current flowing through the motor is controlled near the specified value.
Because you have so that, similarly to the invention substantially according to Claim 1, it is possible to reliably prevent an excessive current from flowing to the motor while more simple circuit structure, and lightweight devices, miniaturization There is an effect that it can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an electric system of an electric vehicle including a motor control device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a motor control device.

FIG. 3 is a diagram showing currents and voltages of respective parts related to energization of a motor and motor current detection during forward power running.

FIG. 4 is a diagram showing currents and voltages of respective parts relating to energization of a motor and motor current detection during forward regeneration.

FIG. 5 is a diagram showing currents and voltages of respective parts relating to energization of a motor and detection of a motor current during reverse power running.

FIG. 6 is a diagram showing currents and voltages of respective parts related to energization of a motor and detection of a motor current, during reverse regeneration.

FIG. 7 is a diagram showing voltage signals of respective parts related to operation for current limitation.

FIG. 8 is a diagram showing voltage signals of respective parts related to an operation for current limitation when a comparator is provided with hysteresis.

FIG. 9 is a circuit diagram showing another embodiment of the motor control device.

FIG. 10 is a diagram showing voltage signals of respective parts related to an operation for current limitation in the case of the embodiment of FIG. 9.

[Explanation of symbols]

2,2 'motor 4 operation part 7 Main control unit 8 CPU 11, 11 'Current control unit 21,41 pulse generator 31,51 comparator 32,52 drive circuit 33,53 Motor current detection circuit

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02P 5/00-5/26 H02P ⁷ /00-7/34 A61G 5/04 502 B60L 15/20

Claims (3)

(57) [Claims] 1. A motor control device which is interposed between a DC motor and a power supply, and which controls the amount of electricity supplied to the motor by changing the time of applying the power supply voltage. A pulse generation circuit that generates a pulse according to a command, a motor current detection circuit that converts the current flowing through the motor into a voltage value, and a composite signal that combines the output of the pulse generation circuit and the output of the motor current detection circuit. And a circuit that gives the above-mentioned synthesized signal to a reference value and outputs an output according to the difference.
It is equipped with a comparator and a circuit that controls the increase / decrease in the amount of electricity supplied to the motor according to the output of this comparator. If the current flowing in the motor is lower than the specified value,
Output according to the on / off switching of the output
When the output of the comparator is switched, it flows to the above motor.
When the current that flows in the motor reaches the specified value , the
When the above composite signal reaches the above reference value,
The current flowing through the motor according to the output of the comparator is specified as above.
A motor control device characterized by being controlled to a value close to a value . 2. A motor control device which is interposed between a DC motor and a power supply, and which controls the amount of electricity supplied to the motor by changing the time for which the power supply voltage is applied. A pulse generation circuit that generates a pulse according to a command, a motor current detection circuit that converts a current flowing in the motor into a voltage value, an output of the pulse generation circuit and an output of the motor current detection circuit are compared, and It is equipped with a comparator that outputs according to the difference, and a circuit that controls the increase or decrease of the amount of electricity supplied to the motor according to the output of this comparator.If the current flowing through the motor is lower than the specified value,
Output according to the on / off switching of the output
Flow to the motors by the output of the serial comparator is switched
When the current that flows in the motor reaches the specified value , the
The output of the motor current detection circuit is the pulse generation
A value equal to the output of the path is reached, at which time the output of the comparator
The current flowing to the motor is controlled near the specified value according to the force.
Motor control device characterized in that it is. 3. The comparator is based on the pulse generator circuit.
From the analog voltage that can freely change the output and voltage value of
Output that is a composite of the output of Compare the output of the motor current detection circuit, When the current flowing through the motor reaches the specified value,
The motor current detection circuit outputs the output of the pulse generation circuit and
Value equal to the combined output of the above analog voltages
And the motor flows according to the output of the comparator at this time.
Current is controlled near the above specified value.
The motor control device according to claim 2.