JP3562053B2 - Control device for electric power steering device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a control device for an electric power steering device.
[0002]
[Prior art]
2. Description of the Related Art An electric power steering device for a vehicle detects a steering torque or the like generated in a steering shaft by operating a steering handle, and calculates a steering assist command value which is a control target value of a motor based on the detected signal. In the current feedback control circuit, the difference between the steering assist command value, which is the control target value, and the detected value of the motor current is obtained as a current control value, and the motor is driven by the current control value. Some assist the steering force of the steering wheel.
[0003]
In such an electric power steering apparatus, as shown in FIG. 14, an H bridge having four first and second arms by connecting four field effect transistors FET1 to FET4 to the bridge. A motor control circuit is used in which a circuit is formed and a power supply V is connected between its input terminals and the motor M is connected between its output terminals.
[0004]
The first arm FET1 (or the second arm) of the pair of two FETs forming two opposing arms of the H bridge circuit forming the motor control circuit. The motor current is controlled by driving a PWM signal (pulse width modulation signal) having a duty ratio D determined based on the current control value.
[0005]
Further, based on the sign of the current control value, the FET3 of the second arm is turned ON, the FET4 of the first arm is turned OFF (or the FET3 of the second arm is turned OFF, and the first arm FET3 is turned off). By controlling the FET 4 of the motor to ON), the rotation direction of the motor M is controlled.
[0006]
When the FET 3 is in the conductive state, the current flows through the FET 1, the motor M, and the FET 3, and a positive current flows through the motor M. When the FET 4 of the second arm is conductive, current flows through the FET 2, the motor M, and the FET 4, and a negative current flows through the motor M.
[0007]
This motor control circuit is widely used because FETs on the same arm are not driven at the same time and the possibility of short-circuiting of the arm is low and the reliability is high. See Japanese Patent Publication No. 5-10270).
[0008]
[Problems to be solved by the invention]
FIG. 15 shows the relationship between the motor current I (current actually flowing through the motor and different from the detected current i) and the duty ratio D of the PWM signal. That is, when the steering wheel is operated and the steering torque is generated, the relationship between the motor current I and the duty ratio D changes as shown by the line (a) in FIG. In the circuit, a steering assist command value Iref, which is a motor control target value, is calculated based on a steering torque detection signal, and the difference between the steering assist command value Iref and the detected value i of the motor current to be fed back is calculated. Is output to the motor drive circuit, the duty ratio D for controlling the semiconductor elements of the motor drive circuit takes a certain value, and no particular trouble occurs.
[0009]
However, when the steering wheel returns to the straight traveling position by the self-aligning torque after the steering wheel is turned off (hereinafter referred to as "return of the steering wheel"), since the steering torque is not generated, the motor is not driven. Although the steering assist command value Iref, which is the control target value of the motor, becomes zero, a back electromotive force is generated in the motor. Therefore, the relationship between the motor current I and the duty ratio D is represented by a line in FIG. As shown in (b), the movement changes upward by an amount corresponding to the back electromotive force, and the relationship between the motor current I and the duty ratio D is discontinuous when the value of the duty ratio D is near zero. Part occurs.
[0010]
On the other hand, the feedback control circuit attempts to calculate the current control value E. However, since there is no duty ratio D corresponding to the steering assist command value Iref, the feedback control circuit modulates the current as shown by the line (c) in FIG. An oscillating current having an amplitude substantially corresponding to the discontinuous portion of the data current I is output as the current control value E.
[0011]
The generation of such an oscillating current not only becomes a source of noise but also hinders the stability of feedback control. An object of the present invention is to solve the above problems.
[0012]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION The present invention solves the above-described problems, and provides a steering mechanism based on a steering assist command value calculated based on at least a steering torque signal generated in a steering shaft and a current control value calculated from a detected motor current value. In a control device of an electric power steering device provided with a feedback control means for controlling an output of a motor for providing an auxiliary force, a power supply is connected between input terminals of a bridge circuit formed by connecting a semiconductor element to an H bridge, and a power supply is connected between output terminals. A motor driving means to which the motor is connected and a semiconductor element of a first arm among a pair of semiconductor elements forming two opposing arms of an H bridge circuit forming the motor driving means are controlled by the current control. Driven by a PWM signal having a first duty ratio D1 determined on the basis of the value of A control command for independently outputting a PWM signal having a first duty ratio D1 and a PWM signal having a second duty ratio D2 to the motor driving means so as to drive the motor with a PWM signal having a second duty ratio D2. Means,
The second duty ratio D 2, it is defined by the first duty ratio D 1 of the function in which the following formula (2)
D 2 = a · D 1 + b (2)
Here, a and b are constants represented by the following equations.
a = -K _T ω ret / γV b
b = 1 + K _T ω ret / V b
Where V b : battery voltage
K _T : Motor back EMF constant
ω ret : Motor angular velocity when the handle returns
γ: constant .
The control command means receives a value of the first duty ratio D 1 as an input and calculates a value of the second duty ratio D 2 by the function formula (2), and a first duty ratio D 1 of the first PWM signal output means for outputting a PWM signal, the second is computed by the computing unit duty ratio second based on the value of D 2 duty ratio D 2 second for outputting a PWM signal PWM signal output means.
Further, the control command means receives a value of the first duty ratio D 1 as an input and calculates a value of the second duty ratio D 2 by the function formula (2), and a first duty ratio D 1 A converter for converting a signal having the second duty ratio D 2 into an analog signal, a signal generator for generating a sawtooth signal or a triangular signal having a wavelength corresponding to one cycle of the PWM signal, and a signal converter. The signal converter may use a waveform signal output from the signal generator to output a PWM signal having a time width corresponding to the voltage of the analog signal.
Further, the control instruction means comprises first and function generating means for generating a second analog signal duty ratio D 2 based on the duty ratio D 1 of the signal, the first duty ratio D 1 of the signal analog signal , A signal generator for generating a sawtooth wave signal or a triangular wave signal having a wavelength corresponding to one cycle of the PWM signal, and a signal converter. The signal converter outputs the signal from the signal generator. A PWM signal having a time width corresponding to the voltage of the analog signal may be output using the waveform signal.
[0013]
[Action]
The control command means determines, based on the current control value, a semiconductor element of a first arm among a pair of semiconductor elements constituting two opposing arms of an H-bridge circuit constituting a motor driving means. the first driven with PWM signals duty ratio D 1 is, the semiconductor device of the second arm in a second duty ratio D 2 of the PWM signal, independently driven. Here, the second duty ratio D 2 are those defined by the formula is first function of the duty ratio D 1 of the (2). As a result, even when the steering torque is not generated, such as when the steering wheel returns, the discontinuity does not occur in the relationship between the motor current I and the duty ratio near the value of the duty ratio near zero. There is no possibility that an oscillating current is output as the value E.
[0014]
【Example】
Hereinafter, embodiments of the present invention will be described. First, the basic concept of the present invention will be described. As described earlier with reference to FIG. 15, in the state where the steering wheel is returned to the straight traveling position by the self-aligning torque after the steering wheel is turned off, the steering torque is not generated. Although the steering assist command value Iref, which is the control target value of the motor, becomes zero, the relationship between the motor current I and the duty ratio D is shown in FIG. As shown by the line (b), it moves upward by an amount corresponding to the back electromotive force, and when the value of the duty ratio D is near zero, the relationship between the motor current I and the duty ratio D does not change. A continuous portion is generated, and an oscillating current having an amplitude substantially corresponding to the discontinuous portion of the motor current I is output, thereby generating noise and other disadvantages.
[0015]
For this reason, in the present invention, the discontinuous portion between the motor current I and the duty ratio D is controlled to be continuous, that is, as shown in FIG. On the line (b) showing the relationship between I and the duty ratio D, the motor is continuously connected between the point p indicating the motor current I when the duty ratio D = γ and the origin o. To solve the problem by controlling the relationship between the data current I and the duty ratio D.
[0016]
More specifically, FET3 and FET4 are driven by a PWM signal having a duty ratio D2 defined by a linear function of the duty ratio D1 described above. In the region where is small, the FET1 of the first arm and the FET3 of the second arm are driven simultaneously and with different duty ratios D.
[0017]
In a region where the duty ratio D1 is larger than γ, a conventional driving method, that is, a control method in which the FET3 (or FET4) is controlled to be turned ON or OFF depending on the current direction.
[0018]
Here, first, FET1 (or FET4) is not controlled to be kept ON (or OFF) according to the rotation direction of the motor determined by the sign of the PWM signal as in the conventional driving method. Consider the case where driving is performed at the same time as (or FET2) and at a different duty ratio.
[0019]
FIG. 17 is a diagram for explaining the operation when FET1 and FET3 are driven simultaneously and at different duty ratios. FIG. 18 is a diagram for explaining the operation of the first arm FET1 and the second arm. The effect of the motor back electromotive force KTω is subtracted from the operating state of the FET, the motor terminal voltage VM, and the motor terminal voltage VM when the FET 3 and the FET 3 are driven simultaneously and at different duty ratios D. FIG. 4 is a diagram for explaining a relationship between a value Ri and a motor current I.
[0020]
Now, while driving FET1 at the duty ratio D1, FET3 is driven at the duty ratio D2 larger than the duty ratio D1 of FET1 (that is, longer in time), and FET2 and FET4 are kept OFF. It shall be. FIGS. 18A and 18B show the ON / OFF states of the FETs 1 and 3 with respect to time.
[0021]
At this time, the motor terminal voltage VM changes as shown in FIG. That is, first, when both FET1 and FET3 are ON (this state is called mode A), the battery voltage Vb is applied between the terminals of the motor M. Next, when the FET1 is OFF and the FET3 is ON (this state is called mode B), the voltage between the terminals of the motor M becomes zero.
[0022]
Further, when both FET1 and FET3 are OFF (this state is referred to as mode C), a negative battery voltage -Vb is applied between the terminals of the motor M. That is, in mode C, since both FET1 and FET3 are OFF, the motor M has a resistance R _L → a regenerative diode DT4 of FET4 → motor M as shown in FIG. A current circuit from the regeneration diode DT2 of the FET2 to the power supply is formed, and the voltage VM between the terminals of the motor M becomes the negative battery voltage -Vb.
[0023]
When the motor currents are balanced by driving FET1 and FET3 simultaneously and at different duty ratios, if the period of the PWM signal is sufficiently short compared to the electrical time constant of the motor, The motor current I can be approximately expressed by the following equation (1).
[0024]
I = {(D1 + D2-1) · Vb / R} −K _T ω / R (1)
Here, D1: duty ratio D1, D2: duty ratio D2,
Vb: battery voltage, R: resistance between motor terminals,
_KT : Back electromotive force constant of the motor, ω: Motor angular velocity, where D2 = f (D1), and the duty ratio D2 is a continuous function of the duty ratio D1, and ω = When ωret and D1 = 0, if a function f that satisfies I = 0 is defined, the continuity of the duty ratio D to the motor current I characteristic can be obtained within the range of 0 ≦ ω ≦ ωret. Can be.
[0025]
Here, the following linear function expression (2) is defined as an example of the function f.
[0026]
D2 = aD1 + b (2)
Here, a and b are constants.
[0027]
First, the following conditions are set to obtain the constants a and b.
[0028]
(1) When the duty ratio D1 = γ, the duty ratio D2 = 1 (100%)
Here, γ is an arbitrary set value (2) When the duty ratio D1 = 0 and ω = ωret, I = 0
Where ω is the motor angular velocity and ωret is the motor angular velocity when the steering wheel returns.
[0029]
The above condition (1) is a condition for determining the position of the point p on the line (b) when the duty ratio D1 = γ in FIG. 16, and corresponds to the normal driving state.
[0030]
The condition (2) is a condition for determining that the line (b) passes through the origin o in FIG. Accordingly, by obtaining the constants a and b satisfying the above conditions, a first-order function connecting the point p and the origin o can be determined.
[0031]
In a region where the duty ratio D1 is larger than γ, the driving method is the same as the conventional driving method, that is, the control method in which the FET3 (or FET4) is turned ON or OFF depending on the current direction.
[0032]
The constants a and b satisfying the above conditions are represented by the following equations (3) and (4).
[0033]
a = −K _T ωret / γVb (3)
b = 1 + K _T ωret / Vb (4)
The motor current I at this time is obtained by substituting equation (2) into D2 of equation (1) and substituting the constants a and b determined by equations (3) and (4) into the following. It can be expressed by equation (5).
[0034]
I = Vb / R {1− (K _T ωret / γVb)} · D1
−K _T / R (ωret −ω) (5)
According to the equation (5), the relationship between the motor current I and the duty ratio D is a discontinuous portion even in a region where the motor angular speed ω is smaller than the motor angular speed ωret when the steering wheel returns. Disappears.
[0035]
That is, by driving the FET1 at the duty ratio D1 and simultaneously driving the FET3 at the duty ratio D2 different from the duty ratio D1, the motor angular velocity .omega. Even in a region smaller than the angular velocity ωret, the duty ratio D1 can be continuously changed with respect to the motor current I.
[0036]
Next, an electric power steering apparatus suitable for carrying out the present invention will be described with reference to FIGS. FIG. 1 is a view for explaining the outline of the structure of an electric power steering device. Is bound to The shaft 2 is provided with a torque sensor 3 for detecting a steering torque of the steering handle 1. A motor 10 for assisting the steering force is connected to the shaft 2 via a clutch 9 and a reduction gear 4. I have.
[0037]
An electronic control circuit 13 for controlling the power steering device is supplied with power from a battery 14 via an ignition key 11. The electronic control circuit 13 calculates a steering assist command value based on the steering torque detected by the torque sensor 3 and the vehicle speed detected by the vehicle speed sensor 12, and based on the calculated steering assist command value, the motor 10 Control the current supplied to the
[0038]
The clutch 9 is controlled by an electronic control circuit 13. The clutch 9 is engaged in a normal operating state, and is disconnected when the electronic control circuit 13 determines that the power steering device has failed and when the power is off.
[0039]
FIG. 2 is a block diagram of the electronic control circuit 13. In this embodiment, the electronic control circuit 13 is mainly composed of a CPU. Here, functions executed by a program in the CPU are shown. For example, the phase compensator 21 does not indicate the phase compensator 21 as independent hardware, but indicates a phase compensation function executed by the CPU.
[0040]
Hereinafter, functions and operations of the electronic control circuit 13 will be described. The steering torque signal input from the torque sensor 3 is phase-compensated by the phase compensator 21 to enhance the stability of the steering system, and is input to the steering assist command value calculator 22. The vehicle speed detected by the vehicle speed sensor 12 is also input to the steering assist command value calculator 22.
[0041]
The steering assist command value calculator 22 calculates a steering assist command value Iref which is a control target value of the current supplied to the motor 10 by a predetermined arithmetic expression based on the input and phase-compensated steering torque signal and vehicle speed signal. I do.
[0042]
A circuit composed of a comparator 23, a differential compensator 24, a proportional calculator 25, an integral calculator 26, and an adder 27 performs feedback control so that the motor current matches the steering assist command value Iref. Circuit.
[0043]
The comparator 23 compares a steering assist command value Iref, which is a control target value calculated by the steering assist command value calculator 22, with a motor current value I detected by a motor current detection circuit 42 described later. The signal of the difference is output.
[0044]
The proportional calculator 25 outputs a proportional value proportional to the difference between the steering assist command value Iref and the motor current value I. Further, the output signal of the proportional calculator 25 is integrated in the integration calculator 26 in order to improve the characteristics of the feedback system, and the proportional value of the integrated value of the difference is output.
[0045]
The differential compensator 24 outputs a value proportional to the differential value of the steering assist command value Iref in order to increase the response speed of the motor current value I to the steering assist command value Iref.
[0046]
The differential value of the steering assist command value Iref output from the differential compensator 24, the proportional value proportional to the difference between the steering assist command value Iref output from the proportional calculator 25 and the motor current value I, the integral calculator 26 Is added in the adder 27, and the current control value E as the calculation result is output to the motor control circuit 41. The current flowing through the motor is detected by a motor current detection circuit 42.
[0047]
FIG. 3 shows an example of the configuration of the motor control circuit 41. The motor control circuit 41 comprises a control command unit 45, a gate drive circuit 46, an H bridge circuit comprising FET1 to FET4, and the like, and the control command unit 45 is based on the current control value E input from the adder 27. And outputs a PWM signal for driving the FETs 1 to 4 and a rotation direction signal for instructing the motor rotation direction.
[0048]
The gate of the FET1 (FET2) is turned ON / OFF based on the PWM signal of the duty ratio D1 outputted from the control command unit 45, and the gate of the FET3 (FET4) is based on the PWM signal of the duty ratio D2. The gate is turned ON / OFF to control the magnitude of the current I actually flowing to the motor.
[0049]
Which one of FET1 and FET2 is driven and which one of FET3 and FET4 is driven is determined by a rotation direction signal for determining the rotation direction of the motor.
[0050]
Motor current detection circuit 42 detects the magnitude of the positive current based on the voltage drop across resistor R1, and detects the magnitude of the negative current based on the voltage drop across resistor R2. . The detected motor current value I is fed back to the comparator 23 and input (see FIG. 2).
[0051]
Next, the configuration of the control command unit 45 will be described. FIG. 4 shows a first embodiment of the control commander, which comprises a microprocessor 451 and two PWM timers 452 and 453. In this configuration, based on the input current control value E, the PWM timer 452 is operated to output the PWM signal D1 having the time width of the duty ratio D1, and at the same time, the PWM signal D1 is input to the microprocessor 451. The duty ratio D2 is calculated based on the function equation (2) described above, and the PWM timer 453 is operated to calculate and output the PWM signal D2 having the time width of the duty ratio D2.
[0052]
As the gate drive circuit 46, for example, a circuit composed of four AND circuits AN1 to AN4 and one knot circuit NT1 as shown in FIG. 5 is proposed.
[0053]
According to this circuit, assuming that the rotation direction signal is ON (for example, indicating the forward rotation) and the PWM signals D1 and D2 are input, the FET2 is driven by the output of the AND circuit AN2 and the output of the AND circuit AN4. FET4 is driven. At this time, since the output of the NOT circuit NT1 is OFF, there is no output of the AND circuits AN1 and AN3, and the FET1 and FET3 are OFF.
[0054]
Assuming that the rotation direction signal is OFF (indicating, for example, a negative rotation) and the PWM signals D1 and D2 are input, the output of the NOT circuit NT1 is ON, so that the output of the AND circuit AN1 drives the FET1 and FET3 is driven by the output of the AND circuit AN3. At this time, there is no output of AND circuits AN2 and AN4, and FET2 and FET4 are turned off.
[0055]
FIG. 6 shows a second embodiment of the control commander, which comprises a microprocessor 451, two D / A converters 454 and 455, two comparators 456 and 457, and a signal generator 458.
[0056]
In this configuration, an analog signal AD1 corresponding to the duty ratio D1 based on the input current control value E and a duty ratio D2 obtained as a result of the operation of the function equation (2) correspond to the analog signal AD1. The analog signal AD2 is obtained, and the analog signals AD1 and AD are compared with the sawtooth signal or the triangular signal having a wavelength corresponding to one cycle of the PWM signal output from the signal generator 458 by the comparators 456 and 457. It outputs a PWM signal D1 and a PWM signal D2 having a time width corresponding to the voltage of the signals AD1 and AD. FIG. 7 shows an example of a sawtooth wave signal generation circuit, and FIG. 8 shows an example of a triangular wave signal generation circuit. The signal generation circuit is a known circuit, and a description thereof will be omitted.
[0057]
FIG. 9 shows a PWM signal D1 and a PWM signal D2, which are output by comparing the sawtooth signal output from the signal generator 458 by the comparators 456 and 457 with the analog signals AD1 and AD2, and the motor. FIG. 10 shows waveforms of applied voltages. FIG. 10 shows PWM signals D1 and D2 outputted by comparing a triangular wave signal with analog signals AD1 and AD2, and waveforms of voltages applied to the motor. It is shown. As is apparent from a comparison between FIG. 9 and FIG. 10, in the case of the triangular wave signal, the rising position of the PWM signal D1 is shifted from the PWM signal D2, and the voltage waveform applied to the motor is also different. There is no substantial difference.
[0058]
FIG. 11 shows a third embodiment of the control commander, which comprises a microprocessor 451, a D / A converter 454, a duty function generator 459, two comparators 456 and 457, and a signal generator 458. You.
[0059]
In this configuration, an analog signal AD1 corresponding to the duty ratio D1 is obtained based on the input current control value E, and a duty function generator 459 having a function generation circuit based on the function equation (2) An analog signal AD2 corresponding to the duty ratio D2 is obtained by inputting the analog signal AD1 and a sawtooth wave signal having a wavelength corresponding to one cycle of the PWM signal output from the signal generator 458 by the comparators 456, 457 or It compares the triangular wave signal with the analog signals AD1 and AD, and outputs PWM signals D1 and D2 having a time width corresponding to the voltages of the analog signals AD1 and AD. As the duty function generator 459, for example, a configuration based on a combination of analog circuits using general operational amplifiers as shown in FIGS. 12 and 13 is proposed.
[0060]
The comparators 456 and 457 and the signal generator 458 are the same as those of the second embodiment, and the outputs of the comparators 456 and 457 are the same as those described in FIGS. 9 and 10 in the second embodiment. It does not change.
[0062]
【The invention's effect】
As described above, the control device for the electric power steering device according to the present invention is the first arm of the pair of semiconductor elements constituting two opposing arms of the H-bridge circuit constituting the motor driving means. of the semiconductor device is driven at the first duty ratio D 1 of the PWM signal is determined based on the current control value, the semiconductor device of the second arm in a second PWM signal duty ratio D 2, independently It is driven. Here, the second duty ratio D 2 is defined by the formula is first function of the duty ratio D 1 of the (2).
[0063]
As a result, even when the steering torque is not generated, such as when the steering wheel returns, there is no discontinuity between the motor current and the duty ratio when the duty ratio value is near zero. No oscillating current is generated, and no noise is generated or the stability of feedback control is not hindered.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating the configuration of an electric power steering device.
FIG. 2 is a block diagram of an electronic control circuit of the electric power steering device.
FIG. 3 is a circuit block diagram showing a configuration of a motor driving circuit.
FIG. 4 is a circuit block diagram showing a configuration of a first embodiment of a control command device.
FIG. 5 is a circuit block diagram showing an example of the configuration of a gate drive circuit.
FIG. 6 is a circuit block diagram showing the configuration of a second embodiment of the control command device.
FIG. 7 is a circuit block diagram showing an example of a configuration of a saw-tooth wave signal generation circuit.
FIG. 8 is a circuit block diagram showing an example of a configuration of a triangular wave signal generation circuit.
FIG. 9 is a view for explaining a sawtooth signal waveform, a duty ratio of a PWM signal, and a motor voltage in the second embodiment.
FIG. 10 is a diagram for explaining a duty ratio and a motor voltage of a triangular wave signal waveform and a PWM signal in the second embodiment.
FIG. 11 is a circuit block diagram showing the configuration of a third embodiment of the control command device.
FIG. 12 is a circuit block diagram showing an example of a duty function generator according to a third embodiment.
FIG. 13 is a circuit block diagram showing an example of a duty function generator according to the third embodiment.
FIG. 14 is a motor drive circuit diagram including a conventional H bridge circuit constituted by FETs.
FIG. 15 is a diagram illustrating the relationship between a motor current and a duty ratio of a PWM signal in a conventional motor control circuit.
FIG. 16 is a diagram for explaining a relationship between a motor current and a duty ratio of a PWM signal in the motor control circuit according to the present invention.
FIG. 17 is a diagram for explaining an operation when driving two opposite-arm FETs of the H-bridge circuit at the same time at different duty ratios;
FIG. 18 is a diagram for explaining a relationship between an operation state of a FET, a motor terminal voltage VM, a motor current I, and the like.
[Explanation of symbols]
3 Torque sensor 10 Motor 11 Ignition key
12 Vehicle speed sensor 13 Electronic control circuit 14 Battery 21 Phase compensator 22 Steering assist command value calculator 23 Comparator 24 Differential compensator 25 Proportional calculator 26 Integral calculator 27 Adder 41 Motor control circuit 42 Motor current detection circuit

Claims (4)

Feedback control for controlling an output of a motor for applying a steering assist force to a steering mechanism based on a steering assist command value calculated based on at least a steering torque signal generated in a steering shaft and a current control value calculated from a detected motor current value. In the control device of the electric power steering device including the control means,
Motor driving means for connecting a power supply between input terminals of a bridge circuit formed by connecting a semiconductor element to an H bridge and connecting the motor between output terminals;
A semiconductor element of a first arm among a pair of two semiconductor elements constituting two opposing arms of an H bridge circuit constituting a motor driving means is determined based on the current control value. A PWM signal having a first duty ratio D1 and a PWM signal having a second duty ratio D2 are used to drive the semiconductor element of the second arm with the PWM signal having the second duty ratio D2 by driving with the PWM signal having the duty ratio D1. And control command means for independently outputting signals to the motor driving means.
The second duty ratio D 2, it is defined by the first duty ratio D 1 of the function in which the following formula (2)
D 2 = a · D 1 + b (2)
Here, a and b are constants represented by the following equations.
a = -K _T ω ret / γV b
b = 1 + K _T ω ret / V b
Where V b : battery voltage
K _T : Motor back EMF constant
ω ret : Motor angular velocity when the handle returns
γ: a control device for an electric power steering device, characterized by a constant . The control command means receives a value of the first duty ratio D 1 as an input and calculates a value of the second duty ratio D 2 by the function equation (2), and a PWM of the first duty ratio D 1 first and PWM signal output unit, a second PWM signal to output a second PWM signal duty ratio D 2 based on the second value of the duty ratio D 2 calculated by the arithmetic unit for outputting a signal The control device for an electric power steering device according to claim 1, further comprising an output unit. Wherein the control command means includes a calculator for calculating the function formula (2) by a second value of the duty ratio D 2 a first value of duty ratio D 1 as inputs, the first duty ratio D 1 and the A signal converter for converting a signal having a duty ratio D 2 of 2 into an analog signal, a signal generator for generating a sawtooth signal or a triangular signal having a wavelength corresponding to one cycle of the PWM signal, and a signal converter. 2. The control device for an electric power steering device according to claim 1, wherein the conversion unit outputs a PWM signal having a time width corresponding to the voltage of the analog signal using the waveform signal output from the signal generation unit. . Wherein the control command means, the conversion and the function generating means for generating a second analog signal duty ratio D 2 based on the first duty ratio D 1 of the signal, the first signal of the duty ratio D 1 into an analog signal And a signal generator for generating a sawtooth signal or a triangular signal having a wavelength corresponding to one cycle of the PWM signal, and a signal converter, and the signal converter outputs a waveform signal output from the signal generator. 2. The control device for an electric power steering device according to claim 1, wherein a PWM signal having a time width corresponding to the voltage of the analog signal is output using the analog signal.

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