JPH05338544A - Motor controller - Google Patents

Abstract

PURPOSE:To provide a motor controller in which the response of the motor electric current for the aimed electric current value is not delayed and the generation of the frictional feeling and vibration is suppressed, even in the application to a power steering device. CONSTITUTION:A control part 15 prepares the PWM instruction value for carrying out the pulse width modulation according to the aimed electric current value of the control quantity of a motor 2 and the motor electric current, etc., detected by an electric current detection part 13. A drive characteristic correction part 15c adds the correction quantity which is determined so that the relation between the PWM instruction value and the motor electric current becomes a nearly linear characteristic, to the PWM instruction value prepared by the control part 15a. A PWM driving part 12 consists of an H bridge circuit, etc., and is corrected by the drive characteristic correction part 15c, and further controls the electric current of the motor 2 by the PWM instruction value which is converted into pulses by a pulse generating part 15b.

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 which is applied to, for example, a power steering device of a vehicle and controls a motor current by pulse width modulation (PWM).

[0002]

2. Description of the Related Art Motors are increasingly used as actuators due to their advantages such as small size and light weight. For example, even in power steering devices for vehicles, electric motors using motors instead of hydraulic motors are used. Is used. Control is important for such a motor.

FIG. 9 is a block diagram showing the structure of a conventional motor control device. In the figure, reference numeral 1 denotes a CPU (central processing unit), for example, a steering torque sensor (not shown) when the motor control device is applied to a power steering device (which detects steering force of a steering wheel in a vehicle power steering device). It also receives signals from the vehicle speed sensor and controls the overall control of the motor (DC motor) 2.

Specifically, a current command value (P for assisting the motor 2 based on the detected steering torque, the detected vehicle speed, etc.)
WM command value) is created. The created PWM command value is input to the drive control circuit 3, and the drive control circuit 3 receives the assist PW.
Control for controlling the four switching elements SW1 to SW4 by a pulse width modulation method (PWM method) according to the deviation between the M command value and the motor current detected by the motor current detection circuit 4 and the polarity of the assist PWM command value. A value is calculated and this control value is output to the gate drive circuit 5.

The CPU 1 has a read-only memory (for example, ROM) in which a command program for performing the above operation is written,
Work memory used in the operation (eg RA
M) and A / D that converts analog signals into digital signals
Built-in converter etc. Further, the gate drive circuit 5 inputs the battery voltage boosted by the boost power supply circuit 6 based on the control value from the drive control circuit 3 and drives the gates of the four switching elements SW1 to SW4 by the PWM method.

The switching elements SW1 to SW4 are connected in an H-bridge type and constitute an H-bridge circuit 7 together with four diodes D1 to D4 to control switching of the electric current of the motor 2. The H-bridge circuit 7 is connected to the battery 9 via the power relay 8. H bridge circuit 7
Is PWM-driven as described above. For example, in the case of normal rotation in FIG. 10, the switching elements SW1 and SW4 are PWM-driven.

At this time, when PWM is on, current flows through the route of battery 9 → switching element SW1 → motor 2 → switching element SW4 → shunt resistance Rs → GND, and when PWM is off, motor 2 → diode. A current flows through the path of D3 → battery 9 → GND → shunt resistance Rs → diode D2 → motor 2.

The drive characteristic (PWM drive characteristic) of the H bridge circuit 7 is as shown in FIG.
When the duty ratio of the M command value exceeds approximately 50%, the motor current sharply increases, and in the case of reverse rotation, when the duty ratio of the PWM command value exceeds approximately 50%, the motor current sharply decreases.

In this case, when the duty ratio of the PWM command value is 0%, the all-gate off mode is set, and when the duty ratio is 50% or less, the load current intermittent mode is set. When the duty ratio is 50% or more, the load current continuous mode is set.

Returning to FIG. 9, the motor current detection circuit 4 detects the motor current from the voltage across the shunt resistor RS. The detection result is input to the CPU 1 and the overcurrent detection circuit 10, respectively. The overcurrent detection circuit 10 detects the overcurrent of the motor 2 and supplies the detection result to the CPU 1. Further, the detection result of the overcurrent detection circuit 10 is also input to the drive control circuit 3, and when the overcurrent of the motor 2 is detected, the driving of the motor 2 is prohibited.

The drive control circuit 3, the gate drive circuit 5,
The booster power supply circuit 6 and the H bridge circuit 7 form a PWM drive unit 12. The motor current detection circuit 4 and the overcurrent detection circuit 10 constitute a current detection unit 13.

Next, FIG. 12 is a block diagram showing a schematic configuration of this motor control device. In this figure, the CPU
1 inputs a target current value, a motor current detection value, etc., and creates a PWM command value, which is a voltage operation amount, in its control section 1a.
Convert to WM pulse. Then, the converted PWM pulse is supplied to the PWM drive unit 12. The PWM drive unit 12 applies a voltage to the motor 2 based on the input PWM pulse. The motor current is detected by the current detector 13, and the detected value is supplied to the controller 1a.

[0013]

By the way, in the above-described conventional motor control device, when the drive characteristic of the PWM drive unit 12 is non-linear, the response of the motor current in the region where the current target value is small deteriorates. There was a problem.

For example, a shunt resistor Rs is provided on the ground side of the H bridge circuit 7, and a power element on the diagonal side of the H bridge circuit 7 (for example, switching element SW1,
In the switching method in which 4) is turned on / off at the same time, the drive characteristic of the PWM drive unit 12 becomes a non-linear characteristic as shown in FIG. 8, and the target current value during motor current control is small (near zero). Then, the section A shown in FIG. 11 is used.

For example, when the conventional motor control device is applied to the electric power steering, the control unit is designed to lengthen the control cycle in order to reduce the cost of the peripheral parts including the CPU, so that the frequency characteristic becomes low. ing. For this reason, in the driving characteristics as shown in FIG. 11, a friction sensation is generated near the neutral position of the steering wheel, or vibration is generated.

Therefore, another object of the present invention is to provide a motor control device which corrects the drive characteristics of the PWM drive section and can obtain a good current response to any current target value.

[0017]

To achieve the above object, a motor control device according to the present invention uses a PW for performing pulse width modulation based on a target current value, a detected motor current value, and the like.
A control unit that creates an M command value, a PWM generation unit that converts the PWM command value into a pulse, and a PW that controls a motor current by the PWM command value converted into the PWM pulse.
In a motor control device including an M drive unit, the PW
It is characterized in that a drive characteristic correction unit for adding a correction amount to the M command value to correct the characteristic of the PWM drive unit is provided.

As a preferred mode, the motor control device is applied to an electric power steering device of a vehicle.

[0019]

In the present invention, when the PWM command value created by the control unit is supplied, the drive characteristic correction unit adds a correction amount to this PWM command value so that the relationship between the PWM command value and the motor current is substantially linear. Correct so that the characteristics are correct. Then, the corrected PWM command value is supplied to the pulse generation unit, converted into a PWM pulse for performing pulse width modulation, and supplied to the PWM drive unit including an H bridge or the like. The PWM drive unit controls the current of the motor according to the PWM command value converted into the PWM pulse.

Therefore, even if the drive characteristic of the PWM drive section has a non-linear characteristic, the drive characteristic is improved by correcting so that the relationship between the PWM command value and the motor current becomes a substantially linear characteristic. A good current response can be obtained even for such a current target value.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a motor control device according to the present invention. In this figure, parts having the same functions as those in FIG. 12 are assigned the same reference numerals and explanations thereof are omitted.

The characteristics of the motor control device according to this embodiment are as follows.
A drive characteristic correction unit 1 that corrects the characteristic of the PWM drive unit 12 between the control unit 15a of the CPU 15 and the PWM generation unit 15b.
5b is provided. In this case, the control unit 15a has the same function as the control unit 1a in FIG.
The WM generator 15b has the same function as the PWM generator 1b in FIG.

In FIG. 1, the drive characteristic correction unit 15c is
As described above, the characteristic of the PWM drive unit 12 is corrected, and thereby the relationship between the PWM command value and the motor current is approximated to a linear characteristic. FIG. 2 is a diagram showing the characteristics of the drive characteristic correction unit 15c, in which the horizontal axis represents the PWM command value and the vertical axis represents the correction amount. In this case, the correction amount is the motor 2
Is forward rotation, the duty ratio of the PWM command value is determined to be from 2% to 50%.
It is determined that the duty ratio of the command value is 2% to -50%.

The correction amount for the PWM command value is written in a ROM (not shown) in the CPU 15 in the form of a table and read by the CPU 15 as appropriate.

When the correction amount of such a characteristic is added to the PWM command value and the input of the PWM generating section 15b is performed, the PWM drive characteristic as shown in FIG. 3, that is, the relationship between the PWM command value and the motor current is substantially linear. The characteristics are obtained. As a result, the same current control characteristic can be obtained for any target current value.

Further, FIG. 4 is a diagram showing the characteristics of the drive characteristic correcting section for performing more precise correction, and the PWM driving characteristics as shown in FIG. 5 are obtained by this characteristic. In this case, it can be seen that the relationship between the PWM command value and the motor current has a completely linear characteristic.

Next, the motor control device of the present invention will be described, for example.
When applied to a power steering device, a very effective effect can be obtained, and this example will be described with reference to FIGS. 6 to 8.

FIG. 6 is a block diagram showing an example of a mechanical system of the electric power steering apparatus. In this figure, the rotational force of the steering handle 31 is transmitted to the steering gear 32 including the pinion gear via the handle shaft. With
It is transmitted to the rack shaft 33 by the pinion gear, and the wheels 34 are turned through the knuckle arm and the like.

Further, a steering assist (auxiliary) motor (DC motor) 2 controlled and driven by the control device 35.
The rotational force (denoted by the same number as above) is transmitted to the rack shaft 33 by meshing between the steering gear 36 including a pinion gear and the rack shaft 33, and assists the steering by the handle 31.

The rotating shaft of the handle 31 and the motor 2 is the gear 3
2, 36 and the rack shaft 33 are mechanically connected. The steering torque sensor 41 detects the steering torque (return torque), and the vehicle speed sensor 42 detects the vehicle speed. Then, the motor 2 is controlled by the control device 35 based on the detected torque, the vehicle speed, and the like.
The control device 35 and the motor 2 are supplied with operating power from a battery 37 mounted on the vehicle.

As shown in FIG. 7, the controller 35 includes a motor current detection circuit 51, a PWM drive circuit 52 for driving the motor 2, and a CPU for controlling the overall control of the motor 2.
53 (for example, a microprocessor), a memory 54, an overcurrent detection circuit 55, A / D conversion circuits 56 to 58, and an interface circuit (not shown) between a computer and the input / output devices described above are mainly configured.

In FIG. 7, the steering torque detected by the steering torque sensor 41 is converted into a digital signal by the A / D conversion circuit 57 and then taken into the CPU 53. The vehicle speed detected by the vehicle speed sensor 42 is converted into a digital signal by the A / D conversion circuit 56 and then counted by a counter (not shown), and the count value representing the vehicle speed is fetched by the CPU 53.

The CPU 53 creates an assist command based on the input steering torque and vehicle speed, outputs a control signal based on the assist command to the PWM drive circuit 52, and the PWM drive circuit 52 drives the motor 2. As a result, the assist torque value (or motor current command value) output from the PWM drive circuit 52 becomes a value determined by the detected torque V _T and the detected vehicle speed V _S , as shown in FIG.

[0034] Figure 8, in accordance with the steering torque V _T, which substantially proportional to the motor current (assist torque is generated) flows against the steering torque V _T of a range, when it exceeds the above range, as constant motor current flows (the assist torque is generated), also according to the vehicle speed V _S, the motor current (assist when when the vehicle speed V _S is high to reduce the motor current (assist torque), the vehicle speed V _S is low It indicates that an assist command for controlling the motor 2 is generated so that the torque is increased.

The motor current is detected by the motor current detection circuit 51, converted into a digital signal by the A / D conversion circuit 58, and then taken into the CPU 53. The memory 54 stores programs and data necessary for the processing of the CPU 53. Further, the overcurrent state of the motor 2 is detected by the overcurrent detection circuit 55 and taken into the CPU 53.

Here, as the PWM drive circuit 52, the one shown in FIG. 1 is used. Therefore, a good PWM drive characteristic can be obtained for any current target value, and in particular, the relationship between the PWM command value and the motor current is completely linear. Therefore, when the motor control device of the present invention is applied to the power steering device, even if the control unit has a longer control cycle and the frequency characteristic is lowered particularly to reduce the cost of peripheral components including the CPU 53, It is possible to obtain an optimum assisting force without causing a friction sensation near the neutral position of the steering wheel or causing a vibration.

In the above embodiment, the control unit 15
Although the a, the PWM generating unit 15b, and the drive characteristic correcting unit 15c are realized by the CPU 15, they may be realized by circuits having respective functions.

Further, the application of the present invention is not limited to the power steering device, but may be applied to other control devices as long as they control the motor. For example, it can be applied not only to a vehicle sunspension control device, a vehicle height control device, and other vehicle control devices, but also to various devices using a motor in other industrial fields other than vehicles. can do.

[0039]

According to the present invention, the drive characteristic of the PWM drive unit is corrected so that the relationship between the PWM command value and the motor current has a substantially linear characteristic. However, a good current response can be obtained.

Even if the present invention is applied to a power steering system in which the control unit has a longer control cycle to reduce the cost of peripheral parts including a CPU and the frequency characteristic is low, the power steering apparatus can be operated near the neutral position of the steering wheel. It is possible to obtain an effect that an optimum assisting force can be obtained without causing a friction sensitivity or becoming vibrational.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a motor control device in an embodiment of the present invention.

FIG. 2 is a diagram showing characteristics of a drive characteristic correction unit in the embodiment.

FIG. 3 is a diagram showing a PWM drive characteristic after being corrected by the drive characteristic correcting unit.

FIG. 4 is a diagram showing characteristics of another drive characteristic correction unit according to the embodiment of the present invention.

FIG. 5 is a diagram showing a PWM drive characteristic after correction by the drive characteristic correction unit.

FIG. 6 is a configuration diagram showing an example of a mechanical system of a power steering device to which the motor control device of the embodiment is applied.

FIG. 7 is a detailed block diagram of a control device of a power steering device to which the motor control device of the embodiment is applied.

FIG. 8 is a diagram showing characteristics of assist torque of the power steering device to which the motor control device of the embodiment is applied.

FIG. 9 is a block diagram showing a configuration of a conventional motor control device.

FIG. 10 is a diagram for explaining a switching method of a conventional motor control device.

FIG. 11 is a diagram showing PWM drive characteristics of a conventional motor control device.

FIG. 12 is a block diagram showing a schematic configuration of a conventional motor control device.

[Explanation of symbols]

 2 motor 12 PWM drive unit 13 current detection unit 15 CPU 15a control unit 15b drive characteristic correction unit 15c PWM generation unit 31 steering wheel 35 control device 41 steering torque sensor 42 vehicle speed sensor 51 motor current detection circuit 52 PWM drive circuit 53 CPU 54 memory 55 Overcurrent detection circuit 56-58 A / D conversion circuit

Claims (2)

[Claims] 1. A control unit that creates a PWM command value for performing pulse width modulation based on a current target value, a detected motor current value, and the like; a PWM generation unit that converts the PWM command value into a pulse; A motor control device comprising: a PWM drive unit that controls a motor current by a PWM command value converted into a PWM pulse; and a drive characteristic correction unit that corrects the characteristics of the PWM drive unit by adding a correction amount to the PWM command value. A motor control device comprising: 2. The motor control device according to claim 1, wherein the motor control device is applied to an electric power steering device of a vehicle.