JPH0820350A - Electric power steering device - Google Patents

Abstract

PURPOSE:To provide an electric power steering device capable of generating the steering auxiliary force in response to the target current even when the reaction force from tires is applied. CONSTITUTION:This electric power steering device is provided with a control means 20 constituted of a target current setting means 15, a deviation determining means 16, a drive control section 17 including at least a proportional integration(PI) control means, a low pass filter (L) 21, a low pass filter (H) 22, and a switching means 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering system for reducing the steering force of a driver by directly applying the power of an electric motor as a steering assist force to a steering system.

[0002]

2. Description of the Related Art In a conventional electric power steering system, a target current is set based on a steering torque detected by a steering torque sensor and a vehicle speed detected by a vehicle speed sensor to drive the motor, and the target current and the current actually flow to the motor. Deviation from the motor current is proportional / integral control means (PI control) or proportional / integral / derivative control means (PID control)
It is known to compensate for phase delays as well as deviations via.

FIG. 7 is an overall block diagram of a conventional electric power steering system, and FIG. 8 is a block diagram of essential parts of the conventional electric power steering system. In FIG. 7, the electric power steering system 1 includes a steering wheel 2, a steering shaft 3, a hypoid gear 4, a rack and pinion mechanism 5 including a pinion 5a, a rack shaft 5b, a tie rod 6, a front wheel 7 of a steering wheel, and a steering assist force. A generated electric motor 8, a steering torque sensor 10 for detecting a steering torque acting on the steering wheel 2 and outputting a steering torque signal T converted into an electric signal corresponding to the steering torque, an electric vehicle corresponding to a vehicle speed by detecting a vehicle speed A vehicle speed sensor 11 that outputs a vehicle speed signal V converted into a signal, a control unit 12 that drives and controls the electric motor 8 based on the steering torque signal T and the vehicle speed signal V, an electric motor drive unit 13, and an electric motor current detection unit 14.
Is provided.

When the steering wheel 2 is steered, the steering torque sensor 10 provided on the steering shaft 3 detects the steering torque, converts it into a corresponding electric signal, and sends the steering torque signal T to the control means 12. Further, the rotation applied to the steering shaft 3 converts the rotational force of the pinion 5a into a linear motion in the axial direction of the rack shaft 5b via the rack and pinion mechanism 5, and changes the steering of the front wheels 7 via the tie rods 6. Let

On the other hand, the vehicle speed sensor 11 detects the vehicle speed of the vehicle, converts it into a corresponding electric signal, and sends the vehicle speed signal V to the control device 12. Control means 12, the motor control voltage V _O supplied to the motor drive unit 13 based on the steering torque signal T and the vehicle speed signal V, the motor drive unit 13 supplies a motor voltage V _M corresponding to the motor control voltage V _O Drive the electric motor 8.

Electric motor 8 driven by electric motor voltage V _M
Is configured to apply a steering assist force to the steering system via the hypoid gear 4 to reduce the steering force applied to the steering wheel 2.

In FIG. 8, the electric power steering 1
Based on the steering torque signal T from the steering torque sensor 10 and the vehicle speed signal V from the vehicle speed sensor 11, the control means 12 of the steering torque (T) -target current ( _IMS ) using the vehicle speed signal V shown in FIG. 9 as a parameter. Target current setting means 15 for converting to the target current I _MS in the characteristic diagram (Table 1), subtracter 16 for calculating the deviation ΔI between the target current I _MS and the feedback current I _MO obtained by filtering the high frequency components of the motor current I _M , the deviation Drive control means 17 having a proportional / integral (PI) control means for proportional / integral compensation of ΔI and generating a current control current _IO for controlling the motor drive means 13, motor current detection means 1
A low-pass filter 18 for removing high-frequency components of the motor detection current I _MD from No. 4 is provided.

The proportional / integral (PI) control means of the drive control means 17 is provided with a proportional element (P: proportion) and an integral element (I: integral), and its transfer function F (jω) gain G and phase angle θ. Is represented by the Bode diagram shown in FIG. In FIG. 11, in the region where the angular frequency ω corresponding to the steering rotation speed is low, the phase delay (θ = -9
However, the gain G (20logG) can be significantly improved, while the gain G (2
0logG) is low, but it is known that the phase delay can be significantly improved.

The low-pass filter 18 is composed of, for example, a primary CR (resistor, capacitor) low-pass filter shown in FIG. 10, and has a cutoff angular frequency ω _ca {= 1 / (C ×
R)} or higher frequencies, the high frequency components are removed with an attenuation amount of 6 dB in the octave, so that noise contained in a high angular frequency band and high band gain are reduced without affecting the steering. .

[0010]

In the conventional electric power steering apparatus, when the electric motor 8 is driven based on the target current I _MS corresponding to the steering torque generated by the steering wheel operation and the deviation signal ΔI of the feedback current I _MO. , Motor current I
_{Since the} low-pass filter 18 is configured to reduce noise in a high frequency band exceeding the frequency of the steering range included in _M , the motor current I _M can be stably converged to the target current I _MS. When the steering wheel is released while stationary or when the vehicle is in the return state while traveling, braking is applied by the counter electromotive force generated in the electric motor 8 by the reaction force from the tire.

Since the electric motor current I _M generated with the generation of the counter electromotive force includes a signal and noise in a frequency band higher than the electric motor current I _M corresponding to the steering torque due to the normal steering operation, it is provided in the feedback loop. Also, the low-pass filter 18 for normal steering reduces not only noise components but also signals in a high frequency band, and the motor current I
_M can not be stable and converges to the target current I _MS, the target current I _MS
There is a problem that it is difficult to control according to.

The present invention has been made to solve such a problem, and its object is to generate an electric power steering apparatus capable of generating a steering assist force according to a target current even when there is a reaction force from a tire. To provide.

[0013]

In order to solve the above-mentioned problems, the control means of the electric power steering apparatus according to claim 1 includes two low-pass filters having different cutoff frequencies between the motor current detection means and the deviation determination means. In addition to the provision of the steering wheel, a switching means for switching the two low-pass filters by detecting the forward and backward steering states is provided.

Further, the control means of the electric power steering apparatus according to claim 2 is provided with a low-pass filter having a cutoff frequency changing means for switching the cutoff frequency between the electric motor current detecting means and the deviation determining means, and the steering It is characterized in that switching means for switching the cutoff frequency changing means by detecting the going state and the returning state is provided.

Further, the switching means of the electric power steering apparatus according to the third aspect of the invention is based on the steering torque signal, the armature voltage of the electric motor detected by the electric motor voltage detecting means, and the electric motor current detected by the electric motor current detecting means. A steering state detecting means for detecting a forward state and a returning state of the steering wheel is provided.

[0016]

In the electric power steering apparatus according to the first aspect of the present invention, the control means is provided with two low-pass filters having different cutoff frequencies and a switching means, and two low-pass filters are detected by detecting the forward and backward states of steering. Is switched, the electric motor can be driven according to the steering state.

According to another aspect of the electric power steering apparatus of the present invention, the control means is provided with a low-pass filter having a cut-off frequency changing means for changing the cut-off frequency and a changing means, so that the forward and backward steering states can be controlled. Since the cutoff frequency changing means is detected and switched, the electric motor can be driven according to the steering state.

Further, in the electric power steering apparatus according to a third aspect of the present invention, the switching means includes the steering state detecting means, and the steering torque signal, the armature voltage of the electric motor detected by the electric motor voltage detecting means and the electric motor current detecting means are detected. Since the forward and backward steering states are detected based on the electric motor current, the steering rotation speed sensor can be eliminated.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram of an essential part of a control system of an electric power steering system according to a first aspect. In FIG. 1, the control means 20 is basically a microprocessor, and the drive control means 1 includes a target current setting means 15, a deviation determination means 16, and at least a PI (proportional / integral) control means.
7, a low pass filter (L) 21, a low pass filter (H) 22, and a switching means 23. Note that the low pass filter (L) 21 and the low pass filter (H) 22 are used instead of the low pass filter 18, and a switching means 23 for switching between the two low pass filters 21 and 22 is provided. Different to Also, the subtractor 2
Reference numeral 6 represents an equivalent circuit which is inputted as a motor back electromotive force V _N including high frequency noise of the motor 8 generated by the reaction force of the tire.

The target current setting means 15 sets steering torque (T) -target current (I) with a vehicle speed signal V as a parameter, which is set in advance in a memory such as a ROM based on design values and experimental values.
_MS ) The target current I _MS corresponding to the steering torque T and the vehicle speed V is selected from the characteristic (see Table 1 in FIG. 9) and output to the plus (+) terminal of the deviation determining means 16.

The deviation determining means 16 is composed of a subtracter or a soft processing subtracting means, and the target current I _MS selected by the target current setting means 15 and the feedback from the low-pass filter 21 or the low-pass filter supplied from the switching means 23. Current I _MO
(= I _MO1, I _MO2) calculates a deviation (I _MS -I _MO) of, providing a deviation signal ΔI to the drive control unit 17.

The drive control means 17 includes at least a proportional / integral (PI) control means, and a deviation signal ΔI (= I) between the target current _IMS and the feedback current I _MO supplied from the deviation determining means 16.
_MS- I _MO ) with proportional compensation, integral compensation, and in some cases differential compensation represented by the Bode diagram shown in FIG. 11, and having a gain G and a phase angle θ with respect to an angular frequency ω, a motor control voltage Output V _O.

The motor control voltage V _O output from the control means 20 is input to a subtractor 26 representing an equivalent circuit, and a motor counter electromotive voltage V _N including high frequency noise of the motor 8 generated by a reaction force of the tire is generated. of the deviation voltage ΔV (= V _O -
V _N ) is calculated and the deviation voltage ΔV is applied to the motor driving means 13.
(= V _O -V _N) is supplied.

The electric motor drive means 13 has a deviation voltage ΔV (= V
_O -V _N) to be PWM (the pulse width modulated) to generate a motor voltage V _M which has been subjected to driving the motor 8 based controls a steering assist force to be applied to the steering system, the motor current I _M and the motor The voltage (armature voltage) V _M is used as the motor current detection means 14 and the motor voltage detection means 19 respectively.
To provide.

The electric motor current detecting means 14 and the electric motor voltage detecting means 19 detect the electric motor current I _M and the electric motor voltage (armature voltage) V _M , respectively, and control them as the electric motor detected current I _MD and the electric motor detected voltage V _MD. (Low-pass filters 21, 22 and switching means 23) are fed back.

The low-pass filter (L) 21 and the low-pass filter (H) 22 are negative feedback (N) connecting the motor current detecting means 14 and the deviation determining means 16.
FB) is arranged in a loop, and the motor detection current I _MD supplied from the motor current detection means 14 is filtered with predetermined cutoff frequencies f _C1 and f _C2 , respectively, and the feedback currents I _MO1 and I _MO2 are respectively switched. 23 to the changeover switch 25 (Sa, Sb).

FIG. 2 is a circuit diagram of two low-pass filters having different cutoff frequencies of the electric power steering apparatus according to the first aspect. In FIG. 2, each of the low-pass filter (L) 21 and the low-pass filter (H) 22 is an example of a primary CR low-pass filter.

The low-pass filter (L) 21 is composed of a passive element such as a resistor R1 and a capacitor C1.
A feedback current I _MO1 obtained by attenuating the motor detection current I _MD as an input signal with a cutoff frequency f _C1 {= 1 / (2πC1R1): attenuation 3 dB} with an attenuation of octave 6 dB is output.

On the other hand, passive low-pass filter (H) 22 is the resistor R2 and the capacitor C2 formed of (passive) devices, cut off the input signal the motor detection current I _MD frequency _{f C2 {= 1 / (2πC2R2} ): Attenuation 3 dB}
In the above frequency band, the feedback current I _MO2 attenuated by the octave 6 dB is output.

Further, the cut-off frequency f _C1 and the cut-off frequency f _C2 are set to different values (for example, f _C1 <f _C2 ), and the switching means 23, which will be described later, makes a low pass depending on the steering state (steering forward state and return state). Switch between filter (L) 21 and low pass filter (H) 22,
The frequency characteristics of the feedback current I _MO1 and the feedback current I _MO2 are changed and fed back to the deviation determining means 16.

The low-pass filter (L) 21 and the low-pass filter (H) 22 are not limited to the primary CR low-pass filter (passive), but have the frequency characteristics required for the feedback current I _MO1 and the feedback current I _MO2. Depending on the situation, it may be configured by a second or higher order passive low-pass filter or an active low-pass filter.

FIG. 3 shows the frequency of the low-pass filter of FIG.
Attenuation amount characteristic diagram and frequency-phase characteristic diagram are shown. Set the characteristics of the low-pass filter 21 and the low-pass filter 22 to L, respectively.
Shown as PF-L and LPF-H. The LPF-L is set to a cut-off frequency f _C1 (= around 70 Hz) so that sufficient attenuation can be obtained at a frequency exceeding the normal steering use range (steering forward state), and a signal component of 100 Hz or more (motor Current I _M = motor detection current I _MD ) and noise components included in this frequency band are sufficiently reduced.

The LPF-H has a cutoff frequency f _C2 (1 KH) higher than the cutoff frequency f _C1 of the LPF-L.
z), and a signal component (motor current I _M = motor detection current I _DM ) in the frequency region (steering return state: 1 KHz) due to back electromotive force including high-frequency noise of the motor 8 generated by the reaction force of the tire. ) Is not attenuated, and the signal components and noise components in the frequency band higher than that are sufficiently reduced.

The switching means 23 comprises a steering state detecting means 24 and a changeover switch 25. The steering state detecting means 24 has a code determination function and compares a code code F indicating the direction of the steering torque signal T and a code code G indicating the direction of the steering rotation speed signal N, and the codes match (F).
= G: Steering forward state), for example, the H level steering state signal S _H does not match the sign (F ≠).
G: Steering return state), the L-level steering state signal S _L is output to the changeover switch 25, and the changeover switch 25 outputs the feedback current I _MO1 from the low pass filter 21 corresponding to the steering state or the low pass filter. 22 is configured to select the feedback current I _MO2 from 22. The steering rotation speed signal N is configured to be calculated from the steering torque signal T, the motor detection voltage V _MD, and the motor detection current I _MD .

The change-over switch 25 is composed of an electronic switch having a contact having a transfer structure or a software program having the same function. In the case of a steering state signal S _H (steering forward state) from the steering state detecting means 24, the low-pass filter 21 is used. Feedback current I
_{When MO1} is selected and in the case of the steering state signal S _L (steering return state), the feedback current I _MO2 from the low-pass filter 22 is selected to be the feedback current I _MO , which is provided to the deviation detecting means 16.

As described above, the control means 20 is provided with the two low-pass filters 21 and 22 and the switching means 23. In the normal steering forward state, the low-pass filter 21 having a relatively low cut-off frequency is selected and installed while the vehicle is stopped. The low-pass filter 22 having a relatively high cutoff frequency is selected for the steering wheel return state in which a counter electromotive force is generated in the electric motor 8 due to a reaction force from the tire, such as when the steering wheel is released when turning or returning during running. , It is possible to drive the electric motor 8 with the electric motor current I _M of the target current I _MS corresponding to the forward and backward steering states.

FIG. 4 is a block diagram of a main part of a control system of the electric power steering system according to the second aspect. Control means 30
1, one low-pass filter 31 having a cut-off frequency changing means 32 is provided in place of the two low-pass filters 21 and 22 shown in FIG. 1, and one break is provided instead of the switching means 23 having a change-over switch 25 having one transfer function. It differs from the control means 20 in that a switching means 33 having a function changeover switch 34 is provided.

The low-pass filter 31 is composed of one low-pass filter provided with a cut-off frequency changing means 32 composed of resistors Ra and Rb for switching the cut-off frequency, and the changeover switch 34 is used to form the resistor Rb (or the resistor Ra may be used).
Short circuit to switch the cutoff frequency.

FIG. 5 is a low-pass filter circuit diagram having cut-off frequency changing means of the electric power steering apparatus according to the second aspect. In FIG. 5, the low-pass filter 31 is composed of a resistor Ra and a resistor Rb that constitute the cutoff frequency changing means 32, and a capacitor Ca.
When the changeover switch 34 is opened, the low-pass filter 31 having a relatively low cutoff frequency f _C1 = 1 / {2πCa (Ra + Rb)} is formed, and when the changeover switch 34 is short-circuited, a relatively high cutoff frequency f _{C2 is formed.} = 1 / (2
πCaRa) low-pass filter 31 is configured. By setting resistance (Ra + Rb) = R1, Ra = R2, and capacitor Ca = C1 = C2, the low-pass filter 31 has the same cut-off frequency as the low-pass filter (L) 21 and the low-pass filter (H) 22 of FIG. f
_C1 and f _C2 can be used, and the same frequency characteristics (attenuation amount and phase) as in FIG. 3 can be realized.

The cut-off frequency changing means 32 is composed of a parallel circuit of resistors Ra and Rb, and the changeover switch 34 is connected in series with Ra or Rb, and the resistance value is changed by opening or short-circuiting the two switches. Cutoff frequency f _C1 , f
It is also possible to configure the low-pass filter 31 having _C2 . The low-pass filter 31 is composed of a primary CR passive low-pass filter, but may be composed of a secondary or higher-order passive low-pass filter or an active low-pass filter as required.

The switching means 33 is constituted by the steering state detecting means 24 described in FIG. 1 and an electronic switch having a contact of one break structure or a software program having the same function, and the steering state signal S from the steering state detecting means 24 is used. _{In the case of H} (steering forward state), the low-pass filter 31 is set to the cut-off frequency f _C1 to output the feedback current I _MO1, and in the case of the steering state signal S _L (steering return state), the low-pass filter 31 is cut off. Set to frequency f _C2 and set feedback current I
_{The MO2} is output and used as the feedback current I _MO , which is provided to the deviation detecting means 16.

As described above, the control means 30 has one low-pass filter 31 having the cut-off frequency changing means 32.
In the normal steering forward state, the low pass filter 31 is set to f _C1 having a relatively low cutoff frequency,
The low-pass filter 31 has a relatively high cut-off frequency in a steering wheel returning state in which a counter electromotive force is generated in the electric motor 8 due to a reaction force from the tire, such as when the vehicle is stationary while stopped or when returning while traveling. Since it is set to f _C2 , the electric motor 8 can be driven by the electric motor current I _M of the target current I _MS corresponding to the forward and backward steering states.

FIG. 6 is a block diagram of the essential portions of the steering state detecting means of the electric power steering apparatus according to the third aspect. In FIG. 6, the steering state detecting means 24 includes a torque code determining means 41, a steering torque differentiating means 42, an electric motor rotation speed calculating section 43, a multiplication processing means 44,
A spring coefficient storage unit 45, a steering rotation speed calculation unit 46, a rotation speed code determination unit 47, and a code matching determination unit 48 are provided.

In general, the steering rotation speed N of the electric power steering device can be expressed by the equation 1. However,
k _T is the spring coefficient, T is the steering torque, N _M is the motor rotation speed.

[0045]

## EQU1 ## N = (1 / k _T ) * d _T / dt + N _{M Further} , the motor voltage (armature voltage) V _M of the motor is expressed by R _{M as} the motor resistance, k as the induced voltage coefficient of the motor, and I as the motor current. Approximately _M is expressed by Equation 2.

[0046]

[Formula 2] V _M = R _M * I _M + k * N _M

By rearranging Formula 2 with respect to the motor rotation speed N _M and substituting it into Formula 1, the steering rotation speed N is calculated as
Can be obtained from

[0048]

[Number 3] _{N = (1 / k T)} * dT / dt + (V M -R M * I M) / k

The torque code determination means 41 is configured to detect the direction code data or the polarity of the torque signal T detected by the steering torque sensor 10, and outputs the direction signal F indicating the direction code or the polarity to the code coincidence determination section 48. . For example,
When the steering torque is in the right direction, the code 1 or the signal F with the polarity plus (+) is output, and when the steering torque is in the left direction, the code 0 or the signal F with the polarity minus (−) is output.

The steering torque differentiating means 42 is composed of a differentiating circuit and differentiating software, performs a differentiating process on the torque signal T and outputs the differential signal dT / dt to the multiplying process means 44, and the multiplying process means 44 stores the spring coefficient. Reciprocal of spring coefficient k _T (1 / k _T ) stored in advance in the means 45 (memory such as ROM)
When the differential signal dT / dt and the multiplication process to the operation result _{{(1 / k T) *} dT / dt} steering rotational speed calculator 4
Supply to 6.

On the other hand, the electric motor rotation speed calculation unit 43 has a memory, arithmetic functions such as subtraction and multiplication / division, and the electric motor resistance R _M and electric motor current detection means 1 stored in advance in the memory.
4, the motor detection current I _MD (= motor current I _M ) and the motor detection voltage V _MD from the motor voltage detection means 19
Based on (= motor voltage V _M ), the motor rotation speed N _M is calculated from Equation 2, and the calculation result N _M is calculated as the steering rotation speed calculation unit 46.
Supply to.

The steering rotation speed calculation unit 46 receives the calculation result {(1 / k _T ) * dT / dt} from the multiplication processing means 44, and
The motor rotation speed N _M from the motor rotation speed calculation unit 43 is added to calculate the steering rotation speed N shown in Formula 3, and the calculation result N is provided to the rotation speed code determination unit 47.

The rotation speed code determination unit 47 is configured to detect the direction code data or the polarity of the steering rotation speed N to detect the direction code or the polarity, and then the direction code (for example, digital code 1, 0) or the polarity. The (+, −) direction signal G is output to the sign matching determination unit 48.

The code coincidence determination unit 48 has a collating function and a comparing function, compares the direction code F of the torque signal T with the direction code G of the steering rotation speed N, and the direction code F and the direction code G match (F. = G), the steering state signal S _H is output assuming that the steering wheel is in the forward direction, and when the direction code F and the direction code G do not match (F ≠ G), the steering state signal S _L is regarded as the steering wheel returning state. Output.

As described above, the steering state detecting means 24 of the electric power steering apparatus according to the third aspect is configured to calculate the steering rotation speed N based on the electric motor current I _M and the electric motor voltage V _M. Since the steering rotation speed N can be detected without disposing the rotation speed sensor, the steering state can be detected from the direction signal F of the steering torque T and the direction signal G of the steering rotation speed N.

[0056]

As described above, in the electric power steering apparatus according to the first aspect of the present invention, the control means is provided with the two low-pass filters having different cutoff frequencies and the switching means, so that the forward and backward steering states can be controlled. Since the two low-pass filters are detected and the electric motor can be driven according to the steering state, it is possible to generate the optimum steering assist force corresponding to the forward and backward states.

In the electric power steering apparatus according to the second aspect of the present invention, the control means is provided with one low-pass filter having a cutoff frequency changing means for switching the cutoff frequency and the switching means, and the forward and backward states of steering are returned. The state can be detected and the cutoff frequency changing means can be switched to drive the electric motor according to the steering state. Therefore, a simple filter configuration can generate an optimum steering assist force corresponding to the forward and backward states. it can.

Further, in the electric power steering apparatus according to the third aspect, the switching means is provided with the steering state detecting means, and the steering torque signal and the armature voltage of the electric motor detected by the electric motor voltage detecting means and the electric motor current detecting means are detected. The steering rotation speed sensor can be deleted by calculating the steering rotation speed based on the electric motor current, and the steering forward / backward state can be detected. Therefore, the configuration can be simplified and the component arrangement space can be expanded. .

Therefore, it is possible to provide the electric power steering apparatus having a simple structure and capable of obtaining the steering assist force according to the steering state.

[Brief description of drawings]

FIG. 1 is a block diagram of a control system main part of an electric power steering according to claim 1.

FIG. 2 is a circuit diagram of two low-pass filters having different cutoff frequencies of the electric power steering apparatus according to claim 1.

3 is a frequency-attenuation characteristic diagram and a frequency-phase characteristic diagram of the low-pass filter of FIG.

FIG. 4 is a block diagram of a control system main part of the electric power steering according to claim 2;

FIG. 5 is a circuit diagram of a low-pass filter having cut-off frequency changing means of the electric power steering apparatus according to claim 2;

FIG. 6 is a block diagram of a main part of steering state detecting means of the electric power steering apparatus according to claim 3;

FIG. 7 is an overall configuration diagram of a conventional electric power steering system.

FIG. 8 is a block diagram of a main part of a conventional electric power steering system.

FIG. 9 is a characteristic diagram of steering torque (T) -target current ( _IMS ) using the vehicle speed signal V as a parameter (Table 1).

FIG. 10 is a primary CR (resistor, capacitor) low-pass filter circuit diagram.

[Figure 11] Bode diagram

[Explanation of symbols]

1 ... Electric power steering device, 2 ... Steering wheel, 3 ... Steering shaft, 4 ... Hypoid gear, 5
... rack and pinion mechanism, 5a ... pinion, 5b ... rack shaft, 6 ... tie rod, 7 ... front wheel, 8 ... electric motor, 10 ...
Steering torque sensor, 11 ... Vehicle speed sensor, 12, 20, 3
0 ... Control means, 13 ... Motor drive means, 14 ... Motor current detection means, 15 ... Target current setting means, 16 ... Deviation determining means, 17 ... Drive control means, 18 ... Low pass filter,
19 ... Motor voltage detecting means, 21 ... Low-pass filter L, 22 ... Low-pass filter H, 23, 33 ... Switching means, 24 ... Steering state detecting means, 25, 34 ... Changeover switch, 31 ... Low-pass filter, 32 ... Cut-off frequency Change means, 41 ... Torque code determination means, 42 ...
Steering torque differentiating means, 44 ... Multiplying processing means, 45 ... Spring coefficient storage means, 46 ... Steering rotational speed calculating section, 47 ... Rotational speed sign determining section, 48 ... Sign matching determining section, _IMS ... Target current, _IMO , I _MO1 , I _MO2 ... Feedback current, ΔI ... Deviation signal,
I _M ... Motor current, I _MD ... Motor detection current, f _C1 , f _C2
... Cutoff frequency, F ... Torque direction signal, G ... Steering rotation speed direction signal, _SL , _SH ... Steering state signal, k
_T ... spring coefficient, R _M ... motor resistance, the induced voltage coefficient of the k ... motor, N ... steering speed, N _M ... motor rotation speed, [Delta] V
... deviation voltage, V _M ... motor voltage, V _MD ... motor detection voltage, V _N ... motor back electromotive force, V _O ... motor control voltage.

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[Procedure amendment]

[Submission date] July 8, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

In FIG. 8, an electric power steering device is shown.
Control means 12 for location 1, a vehicle speed signal V from the steering torque signal T and the vehicle speed sensor 11 from the steering torque sensor 10
Steering torque as a parameter a vehicle speed signal V as shown in FIG. 9 based on the (T) - a target current setting means 15 for converting the target current I _MS of the target current (I _MS) characteristic diagram (Table 1),
Subtractor 16 for calculating a deviation [Delta] I between the target current I _MS and motor current I _M feedback current I _MO of filtering high frequency components of a proportional deviation [Delta] I, proportional plus integral to integral compensation (P
I) A control unit is provided, and the electric motor control unit 13 controls the electric motor.
The drive control means 17 for providing the voltage V _O and the high frequency component of the motor detection current I _MD from the motor current detection means 14 are removed.
A low pass filter 18 for outputting the feedback current I _MO to the subtractor 16 is provided.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

[Figure 7]

Claims (3)

[Claims] 1. A steering torque sensor for detecting a steering torque of a steering system, an electric motor for applying a steering assist force to the steering system, an electric motor current detecting means for detecting an electric motor current flowing through the electric motor, and the steering torque sensor. Target current setting means for setting a target current of the electric motor based on the steering torque signal, deviation determining means for determining a deviation signal between the target current and the electric motor current, and driving of the electric motor is controlled based on the deviation signal. An electric power steering device comprising: a drive control unit having at least a proportional element and an integral element, wherein the control unit controls the cutoff frequency between the electric motor current detection unit and the deviation determination unit. Two different low-pass filters are installed, and steering forward and return states are set. An electric power steering apparatus characterized in that a switching means for switching the two low-pass filters out. 2. A steering torque sensor for detecting a steering torque of a steering system, an electric motor for applying a steering assist force to the steering system, an electric motor current detecting means for detecting an electric motor current flowing through the electric motor, and the steering torque sensor. Target current setting means for setting a target current of the electric motor based on the steering torque signal, deviation determining means for determining a deviation signal between the target current and the electric motor current, and driving of the electric motor is controlled based on the deviation signal. In the electric power steering apparatus, the control means includes a drive control means having at least a proportional element and an integral element, and the control means sets a cutoff frequency between the electric motor current detection means and the deviation determination means. A low-pass filter having cut-off frequency changing means for switching is provided and Electric power steering apparatus detects a forward state and return conditions characterized in that a switching means for switching the cut-off frequency changing unit. 3. The switching means includes the steering torque signal,
And steering state detecting means for detecting the forward and backward states of steering based on the armature voltage of the electric motor detected by the electric motor voltage detecting means and the electric motor current detected by the electric motor current detecting means. The electric power steering device according to claim 1 or 2.