JP2003276631A - Control device for electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an electric power steering device enhancing an accuracy of neutral presumption of a steering wheel. <P>SOLUTION: In the case where a predetermined sampling condition specified by a yaw rate Y is satisfied in addition to a sampling condition specified by a car speed V, a steering torque T and a steering angular velocity ω, it is presumed that a handle is positioned at a neutral position. A steering neutral angle θc is presumed based on a steering relative angle θd sampled at this time. Therefore, even in the case where a vehicle is turned at a low speed, for example, at which the steering torque T is not generated, this is detected by a yaw rate sensor (yaw rate Y≠0). Accordingly, the accuracy of the neutral presumption of the handle can be enhanced regardless of correction of determination of the sampling condition specified by the car speed V, the steering torque T and the steering angular velocity ω. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an electric power steering device that applies an assist force by an electric motor to a steering system of a vehicle such as an automobile.

[0002]

2. Description of the Related Art Conventionally, the following is known as a control device for an electric power steering device of this type. That is, the control device calculates the basic assist command current value, which is the basic control target value of the electric motor, based on the vehicle speed detected by the vehicle speed sensor and the steering torque detected by the torque sensor. The control device drives and controls the electric motor so that the assist force corresponding to the basic assist current value is output (basic assist control). The steering operation is assisted by the assist force output from the electric motor.

Further, when the steering wheel (hereinafter referred to as "handle") is rotated during traveling and the hand is released from the handle (hereinafter referred to as "handle return"), the handle automatically moves to the straight traveling position ( Return to the neutral position (self-aligning function). In the state where the steering wheel is being returned, the inertia of the electric motor that drives the mechanism of the steering system affects the ability of the steering wheel to return to the neutral position. Especially when traveling at low speed, the return to the neutral position of the steering wheel becomes worse. In order to prevent such a problem at the time of returning the steering wheel, for example, control is performed to facilitate returning the steering wheel to the neutral position during low-speed traveling (steering wheel returning control).

As such a steering wheel return control, for example, there is known one in which the return control is performed according to the steering angle detected by the steering angle sensor. The sensor output of the steering angle sensor is adjusted in advance so as to have a predetermined output value when the vehicle is in a straight traveling state (that is, when the steering wheel is in the neutral position). However, the steering angle sensor itself and the components of the steering mechanism (handle etc.) have errors and variations in manufacturing and mounting. In addition, there is a possibility that the constituent parts and their mounting relationships may change during their use, or that the mounting may be distorted when disassembling and assembling during maintenance of the vehicle.

Therefore, there is a possibility that the preset output value of the steering angle sensor and the neutral position of the steering wheel may deviate from each other, and the neutral position of the steering wheel may not be accurately detected.
Therefore, for example, the neutral position of the steering wheel is estimated by a predetermined calculation based on the output value (detection value) of the steering angle sensor, and the steering wheel is calculated from the difference between the output value of the steering angle sensor and the neutral position of the steering wheel obtained by the calculation. Steering absolute angle (direction,
It was necessary to obtain (size). A predetermined steering wheel return command current value is calculated based on the steering absolute angle and the like. This handle return command current value is added to the basic assist command current value.

For example, when the ignition switch is off, the steering absolute angle is temporarily stored in the memory, and when the ignition switch is turned on again, the steering absolute angle when the ignition switch is off is recognized by being read from the memory. You can But,
While the engine is stopped, the steering wheel may be operated or the alignment may be adjusted, resulting in an erroneous estimation of the neutrality of the steering wheel.

In order to solve this problem, it has been proposed in the past to estimate and correct the neutrality of the steering angle from the vehicle speed, the steering torque, the steering angular velocity and the like. That is, as shown in FIG. 4, during the steering wheel neutrality estimation process, the control device first determines the magnitude of the vehicle speed V detected by the vehicle speed sensor and the preset vehicle speed determination threshold Vs (S2).
01).

The sampling value of the vehicle speed V is the vehicle speed determination threshold value V
When it is determined that it is smaller than s (NO in S201), the control device shifts the processing to S202 and stops the neutral estimation processing of the steering wheel (steering wheel). Then, the control device obtains the steering absolute angle (actual steering angle) θ based on the following equation (11) (S203).

Θ = θd−θc (11) Here, θd is a steering relative angle, which is obtained based on the rotation angle of the electric motor detected by the motor rotation angle sensor. θc is the steering neutral angle estimated last time. For example, when the engine is started, the steering neutral angle θc stored when the engine was stopped last time is used as the initial value (temporary value) of this time.

After this, the control device controls the steering wheel based on the steering absolute angle θ and the steering angular velocity ω determined based on the steering relative angle θd determined by the equation (11) and the vehicle speed V detected by the vehicle speed sensor. Calculate the return command current value.
Then, the control device adds the steering wheel return command current value to the basic assist current value obtained by the assist control means.

On the other hand, when it is determined in S201 that the vehicle speed V is higher than the vehicle speed determination threshold Vs (Y in S201).
ES), the control device shifts the processing to S204. S20
In 4, the control device determines the magnitude of the absolute value | T | of the steering torque T detected by the torque sensor and the preset steering torque determination threshold Ts. When it is determined that the absolute value | T | of the steering torque T is larger than the steering torque determination threshold Ts (NO in S204), the control device shifts the processing to S202. When it is determined that the absolute value | T | of the steering torque T is smaller than the steering torque determination threshold Ts (S20
4), the control device shifts the processing to S205.

In step S205, the control device calculates the absolute value │ω│ of the steering angular velocity ω calculated based on the steering relative angle θd.
And the steering angular velocity determination threshold value ωs. When it is determined that the absolute value | ω | of the steering angular velocity ω is larger than the steering angular velocity determination threshold value ωs (NO in S205), the control device shifts the processing to S202. Absolute value of steering angular velocity ω ω
When it is determined that | is smaller than the steering angular velocity determination threshold value ωs (YES in S205), the control device estimates that the steering is at the neutral position, and shifts the processing to S206.

In S206, the control device estimates the steering neutral angle θc based on the following equation (12), and shifts the processing to S207. [theta] c = (1- [lambda]) [theta] d + [lambda] [theta] c (n-1) (12) Here, [lambda] is the forgetting factor (0≤ [lambda] <1), and determines the weight for the past input. θd is a steering relative angle sampled when all the sampling conditions defined by the vehicle speed V, the steering torque T, and the steering angular velocity ω are satisfied, and is based on the rotation angle of the electric motor detected by the motor rotation angle sensor. Is required. θc (n
-1) is the steering neutral angle estimated last time.

In step S207, the control device executes the above-mentioned step S20.
The steering absolute angle (actual steering angle) θ based on the steering neutral angle θc estimated in 6 is calculated based on the following equation (13).

Θ = θd−θc (13) Here, θd is a steering relative angle, which is obtained based on the rotation angle of the electric motor detected by the motor rotation angle sensor. θc is the steering neutral angle estimated last time. For example, when the engine is started, the steering neutral angle θc stored when the engine was stopped last time is used as the initial value (temporary value) of this time.

After that, the control device controls the steering wheel based on the steering absolute angle θ obtained by the equation (13), the steering angular speed ω obtained based on the steering relative angle θd, and the vehicle speed V detected by the vehicle speed sensor. Calculate the return command current value.
Then, the control device adds the steering wheel return command current value to the basic assist current value obtained by the assist control means.

After that, the control device repeats the processing of S201 to S207 at every predetermined control cycle.

[0018]

However, the conventional control device for the electric power steering system has the following problems. That is, when there is a large amount of friction in the steering mechanism, the steering torque T may not be generated even if the steering wheel is not in the neutral position, and the steering mechanism may be kept in the cut state. Therefore, even if the steering wheel is not in the neutral position, all the sampling conditions (neutral estimation conditions) in S201, S204, and S205 may be satisfied. Therefore, there is a problem that the error of the steering neutral angle θc, and by extension, the steering absolute angle θ becomes large due to the false estimation of the steering wheel neutrality.

The present invention has been made to solve the above problems, and an object thereof is to provide a control device for an electric power steering system which can improve the accuracy of neutral estimation of a steering wheel. is there.

[0020]

According to a first aspect of the present invention, the vehicle speed detected by the vehicle speed detecting means, the steering torque detected by the steering torque detecting means, and the steering angular velocity detected by the steering angular velocity detecting means. When it is determined whether or not a predetermined sampling condition defined by is satisfied, and it is determined that the predetermined sampling condition is satisfied, it is estimated that the steering wheel is in the neutral position, In the control device of the electric power steering apparatus including the neutral angle estimating means for estimating the steering neutral angle based on the steering relative angle detected by the angle detecting means, a vehicle direction determining means for detecting the moving direction of the vehicle is provided. In addition to the predetermined sampling condition, the neutral angle estimating means includes a sun angle specified by the vehicle direction information from the vehicle direction determining means. If it is determined that the ring condition is satisfied, the steering wheel is summarized in that that be estimated to be in the neutral position.

According to a second aspect of the present invention, in the control device for the electric power steering apparatus according to the first aspect, the vehicle direction determining means includes a yaw rate detecting means for detecting a yaw rate of the vehicle. To do.

According to a third aspect of the present invention, in the control device for the electric power steering apparatus according to the first aspect, the vehicle direction determining means includes a wheel speed detecting means for detecting a difference in rotational speed between the left and right wheels. The point is to have it.

(Operation) According to the invention described in claim 1,
It is determined whether a predetermined sampling condition defined by the vehicle speed, the steering torque, the steering angular velocity, and the vehicle direction information is satisfied. When it is determined that the predetermined sampling condition is satisfied, the steering is estimated to be in the neutral position. Then, the steering neutral angle is estimated based on the steering relative angle at this time. By providing the sampling condition defined by the moving direction information of the vehicle, it is possible to estimate the neutrality of the steering wheel without being affected by disturbances such as friction in the steering mechanism and road surface conditions. Therefore, the accuracy of the neutral estimation of the steering wheel is improved.

According to the invention of claim 2, claim 1
In addition to the operation of the invention described in (1), vehicle speed, steering torque,
It is determined whether a predetermined sampling condition defined by the steering angular velocity and the yaw rate of the vehicle is satisfied.

According to the invention of claim 3, claim 1
In addition to the operation of the invention described in (1), vehicle speed, steering torque,
It is determined whether or not a predetermined sampling condition defined by the steering angular velocity and the rotational speed difference between the left and right wheels is satisfied.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is embodied in a control device for an electric power steering system will be described below with reference to FIGS.
It will be described with reference to FIG.

As shown in FIG. 1, the electric power steering system 1 comprises a control device 2 and an electric motor 3 which is driven and controlled by the control device 2. The output shaft of the electric motor 3 is provided with a gear 4. It is fixed. Electric motor 3
Is a brushless DC motor, and includes a motor rotation angle sensor (rotary encoder) 5. The motor rotation angle sensor 5 detects the motor rotation angle θm and sends the detection result (motor rotation angle signal) to the control device 2. Further, the electric motor 3 is provided with a motor drive current sensor 6. The motor drive current sensor 6 detects the actual motor drive current Im in the electric motor 3 and sends the detection result (motor drive current signal) to the control device 2.

On the other hand, a steering shaft 8 is connected to a steering wheel (hereinafter referred to as "handle 7"), and a reduction gear 9 is attached to the steering shaft 8.
Is fixed. The reduction gear 9 meshes with the gear 4 of the electric motor 3. A torsion bar (torsion spring) 10 is incorporated in the steering shaft 8, and a torque sensor 11 is provided in the torsion bar 10. The torque sensor 11 detects the steering torque T acting on the steering wheel 7 based on the twist amount of the torsion bar 10 when the steering wheel 8 is rotated by the driver steering the steering wheel 7. This steering torque signal is sent to the control device 2.

The reduction gear 9 has a pinion shaft 12
The pinion gear 13 is fixed via. The pinion gear 13 meshes with a rack 14, and tie rods 15 are fixed to both ends of the rack 14. A knuckle arm 16 is rotatably connected to the tip end of the tie rod 15.
A cross member 17 is rotatably connected between the six members. Both knuckle arms 16 and 16 have front wheels 18 respectively.
Is attached.

A vehicle speed sensor 19 is provided on each of the front, rear, left and right wheels (in FIG. 1, only the vehicle speed sensor 19 of one front wheel 18 is shown). The vehicle speed sensor 19 detects the wheel speed (the number of rotations of the wheel per unit time, that is, the rotation speed), and sends the detection result (wheel speed signal) to the control device 2. The control device 2 calculates the vehicle speed V based on the wheel speed signal sent from the vehicle speed sensor 19.

A yaw rate sensor 20 is provided in a vehicle such as an automobile equipped with the electric power steering device 1. The yaw rate sensor 20 detects a yaw rate Y which is an angular velocity of rotational motion (yawing) about a vertical axis passing through the center of gravity of the vehicle. This yaw rate signal is sent to the control device 2. The yaw rate Y can also be referred to as a rate of change of the speed at which the vehicle rotates or the direction of the vehicle body. The control device 2 determines the direction of the vehicle (that is, the moving direction of the vehicle) based on the yaw rate Y sent from the yaw rate sensor 20. Sense.

When the driver rotates the steering wheel 7, the steering shaft 8 rotates. This rotation is transmitted to the rack 14 via the torsion bar 10, the pinion shaft 12, and the pinion gear 13, and is converted into an axial movement of the rack 14. As a result, both front wheels 18,
18 is steered.

At this time, the controller 2 controls the torque sensor 1
The electric motor 3 is configured to generate a predetermined steering assist torque (assist torque) based on the steering torque T detected by 1 and the vehicle speed V detected by the vehicle speed sensor 19.
Control the forward and reverse. The rotation of the electric motor 3 is transmitted to the reduction gear 9 via the gear 4, the rotation speed is reduced by the reduction gear 9, and the rotation is transmitted to the pinion shaft 12 and the pinion gear 13. The rotation of the pinion gear 13 is the rack 1
4 and is converted into an axial movement of the rack 14. In this way, the assist torque is applied to the steering of the front wheels 18 by the turning operation of the handle 7.

The steering wheel 7, the steering shaft 8, the reduction gear 9 and the torsion bar 10 constitute a steering system of a vehicle such as an automobile (not shown). (Control Device) Next, the electrical configuration of the control device 2 will be described.

As shown in FIG. 2, the control device 2 includes a CPU
(Central processing unit) 21, ROM (Read-only memory)
22, a RAM (read-only memory) 23, and a motor drive device 24.

The ROM 22 stores various control programs such as a basic assist control program and a steering wheel return control program executed by the CPU 21, various data, and various assist torque maps. The assist torque map is obtained in advance from experimental data based on the vehicle model, known theoretical calculations, and the like. The assist torque map includes, for example, a map for obtaining the basic assist current based on the vehicle speed V and the steering torque T, and a map for obtaining the steering wheel return command current based on the vehicle speed, the steering angular velocity, and the steering absolute angle. .

The RAM 23 is a data work area for expanding various control programs written in the ROM 22 and causing the CPU 21 to execute various arithmetic processes. Also,
The RAM 23 temporarily stores various arithmetic processing results when the CPU 21 performs various arithmetic processing.

A torque sensor 11, a vehicle speed sensor 19, a motor drive device 24, a motor rotation angle sensor 5, and a motor drive current sensor 6 are connected to the CPU 21 via input / output interfaces (not shown). CP
The U21 executes various control programs such as a basic assist control program and a steering wheel return control program based on various information obtained from the torque sensor 11, the vehicle speed sensor 19, the motor rotation angle sensor 5, and the motor drive current sensor 6. .

(Operation of Embodiment) Next, various functions of the control device 2 executed according to various control programs will be described with reference to FIG.
It will be described based on the functional block diagram of the CPU 21 shown in FIG. Various parameters such as the vehicle speed V, the steering torque T, the steering relative angle θd, the steering neutral angle θc, and the steering absolute angle θ are used as the meanings of the corresponding signals.

(Basic Assist Control) First, the basic assist control will be described. The basic assist control in the CPU 21 is performed as follows. That is, the steering torque T detected by the torque sensor 11 is the phase compensation means 31.
The phase compensation is performed by, and thus the stability of the electric power steering device 1 is enhanced. The phase compensated steering torque T is sent to the basic assist control means 32. Further, the vehicle speed sensor 19 is provided in the basic assist control means 32.
The vehicle speed V detected by is input.

The basic assist control means 32 calculates the basic assist current Io based on the vehicle speed V detected by the vehicle speed sensor 19 and the phase-compensated steering torque T, and outputs this basic assist current Io to the adding means 33. To do.

The basic assist current Io output from the adding means 33 is sent to the current control means 34. The current control means 34 is based on the difference between the basic assist current Io sent from the addition means 33 and the motor drive current Im detected by the motor drive current sensor 6, and is based on the PI control value or PI.
Calculate the D control value. The current control means 34 calculates P
The I control value or the PID control value is sent to the PWM (pulse width modulation) calculating means 35.

The PWM calculation means 35 receives the received PI.
PWM calculation is performed according to the control value or the PID control value, and the result of this PWM calculation is sent to the motor drive device 24. The motor drive device 24 supplies an assist current to the electric motor 3 based on the result of the PWM calculation sent from the PWM calculation means 35. The electric motor 3 applies a basic assist force (steering assist torque) to the steering wheel 7 based on the supply of the assist current.

(Handle Return Control) On the other hand, the motor rotation angle θm detected by the motor rotation angle sensor 5 is sent to the relative angle calculation means 36. The relative angle calculation means 36 calculates the steering relative angle θd by dividing the motor rotation angle θm by the reduction ratio of the reduction gear 9. The steering relative angle θd is a steering detection angle based on a certain specific angle.

The relative angle calculating means 36 sends the calculated steering relative angle θd to the neutral angle estimating means 37, the absolute angle calculating means 38 and the differential calculating means 39, respectively. The differential calculation means 39 calculates the steering angular velocity ω by differentiating the sent steering relative angle θd, and sends the steering angular velocity ω to the steering wheel return control means 40.

The neutral angle estimating means 37 includes a differential calculating means 3
In addition to the steering angular velocity ω from 9 and the steering relative angle θd from the relative angle calculating means 36, the vehicle speed V detected by the vehicle speed sensor 19, the steering torque T detected by the torque sensor 11, and the yaw rate sensor 20 are detected. The yaw rate Y is input.

The neutral angle estimating means 37 determines whether or not a predetermined sampling condition defined by the vehicle speed V, the steering torque T, the steering angular velocity ω, and the yaw rate Y is satisfied. Then, when all the conditions are satisfied, the neutral angle estimating means 37 estimates that the steering wheel 7 is in the neutral position, and based on the steering relative angle θd at this time, the steering neutral angle θc is calculated by a known theoretical calculation. Estimate based on the calculation. The neutral angle estimating means 37 sends the calculated steering neutral angle θc to the absolute angle calculating means 38. If the sampling condition is not satisfied, the neutral angle estimator 37 stops the calculation and estimation process of the steering neutral angle θc, and the previously calculated steering neutral angle θc.
Is used as the current steering neutral angle (provisional value) θc, and this is sent to the absolute angle calculation means 38.

The handle 7 by the neutral angle estimating means 37
The calculation and estimation processing of the steering neutral angle θc will be described later. The absolute angle calculation means 38 subtracts the steering neutral angle θc sent from the neutral angle estimation means 37 from the steering relative angle θd sent from the relative angle calculation means 36,
The steering absolute angle (actual steering angle) θ is calculated with reference to the steering neutral angle θc, and this steering absolute angle θ is sent to the steering wheel return control means 40.

In addition to the steering angular velocity ω from the differential calculation means 39 and the steering absolute angle θ from the absolute angle calculation means 38, the vehicle speed V detected by the vehicle speed sensor 19 is input to the steering wheel return control means 40. Handle return control means 40
Is based on the vehicle speed V, the steering angular velocity ω, and the steering absolute angle θ,
The steering wheel return command current Ih is calculated, and the steering wheel return command current Ih is output to the adding means 33. The steering wheel return command current Ih is added to the basic assist current Io from the basic assist control means 32. This improves the handle return characteristics. That is, the handle return control means 4
Reference numeral 0 is a compensating means for adding the steering wheel return command current Ih as a compensation current to the basic assist current Io.

(Neutral Estimation) Next, the process of estimating the steering neutral angle θc of the steering wheel by the neutral angle estimating means 37 will be described with reference to the flowchart shown in FIG. In this embodiment, the step is abbreviated as “S”.

As shown in FIG. 4, during the neutral estimation processing of the steering wheel 7, the CPU 21 first detects the vehicle speed V and the preset vehicle speed determination threshold Vs (for example, 30).
(km / h) is determined (S101).

When it is determined that the sampling value of the vehicle speed V is smaller than the vehicle speed determination threshold value (NO in S101), the CPU
21 shifts the processing to S102, and cancels the neutral estimation processing of the steering wheel 7 (steering). And the CPU 21
Calculates the steering absolute angle (actual steering angle) θ based on the following equation (1) (S103).

Θ = θd−θc (1) Here, θd is a steering relative angle, which is obtained based on the rotation angle of the electric motor 3 detected by the motor rotation angle sensor 5. θc is the steering neutral angle previously estimated and calculated. For example, when the engine is started, the steering neutral angle θc stored when the engine was stopped last time is used as the initial value (provisional value) of this time.

After that, the CPU 21 operates the steering wheel based on the steering absolute angle θ obtained by the equation (1), the steering angular velocity ω obtained based on the steering absolute angle θ, and the vehicle speed V detected by the vehicle speed sensor. The return command current Ih is calculated with reference to the various assist torque maps. Then, the CPU 21 sets the steering wheel return command current Ih to the basic assist current I obtained by the basic assist control means 32.
Append to o.

On the other hand, when it is determined in S101 that the vehicle speed V is higher than the vehicle speed determination threshold Vs (S101).
YES), the CPU 21 shifts the processing to S104.
In S104, the CPU 21 determines the magnitude of the absolute value | T | of the steering torque T detected by the torque sensor 11 and the preset steering torque determination threshold Ts. When it is determined that the absolute value | T | of the steering torque T is larger than the steering torque determination threshold Ts (NO in S104), the CPU 2
1 shifts the processing to S102. When it is determined that the absolute value | T | of the steering torque T is smaller than the steering torque determination threshold Ts, that is, when the steering torque T≈0 is determined (S
(YES in 104), the CPU 21 shifts the processing to S105.

At S105, the CPU 21 determines the magnitude of the absolute value | ω | of the steering angular velocity ω calculated and estimated based on the steering relative angle θd and the steering angular velocity determination threshold value ωs.
The absolute value │ω│ of the steering angular velocity ω is the steering angular velocity determination threshold value ωs.
If it is determined to be greater than (NO in S105), CP
U21 shifts the processing to S102. When it is determined that the absolute value │ω│ of the steering angular velocity ω is smaller than the steering angular velocity determination threshold ωs, that is, when it is determined that the steering angular velocity ω≈0 (S
(YES at 105), the CPU 21 shifts the processing to S106.

In S106, the CPU 21 determines the magnitude of the absolute value | Y | of the yaw rate Y of the vehicle detected by the yaw rate sensor 20 and the yaw rate determination threshold value Ys. When it is determined that the absolute value | Y | of the yaw rate Y is larger than the yaw rate determination threshold value Ys (NO in S106),
The CPU 21 shifts the processing to S102. Yaw rate Y
When it is determined that the absolute value of | Y | is smaller than the yaw rate determination threshold Ys, that is, when the yaw rate Y≈0 is determined (YES in S106), the CPU 21 estimates that the vehicle is in a straight traveling state, and proceeds to S107. Transition.

That is, when all the predetermined sampling conditions (that is, the neutral estimation condition of the steering wheel 7) defined by the vehicle speed V, the steering torque T, the steering angular velocity ω, and the yaw rate Y are satisfied, the CPU 21 causes the steering wheel 7 to be neutral. Presumed to be in position.

The sampling condition defined by the steering torque T may be erroneously satisfied by various disturbances. For example, when the vehicle is traveling at a low speed, the steering wheel 7 may be held in a cut state because the friction in the steering mechanism exceeds the road surface reaction force. In this case, the steering torque T is not generated even though the steering is not in the neutral position (steering torque T≈0), and the sampling condition defined by the steering torque T may be erroneously satisfied. If the sampling condition defined by the yaw rate Y is not provided, if the sampling condition defined by the steering angular velocity ω is satisfied, the CPU 21 will erroneously determine that the neutral estimation of the steering wheel 7 has been established.

However, in the present embodiment, even in such a case, if the steering wheel 7 is turned left and right and the vehicle is turning, this is detected by the yaw rate sensor 20. That is, if the yaw rate Y ≠ 0 (| Y |> Ys), the CPU 21 indicates that the vehicle is turning and the steering wheel 7
Judges that he is not in the neutral position.

As described above, by providing the sampling condition defined by the yaw rate Y, in other words, the sampling condition defined by the moving direction information of the vehicle,
The neutral estimation of the steering wheel 7 is possible without being affected by external disturbances such as friction in the steering mechanism and road surface conditions. Therefore,
The accuracy of neutral estimation of the handle 7 is improved.

In S107, the CPU 21 estimates the steering neutral angle θc based on the following equation (2), and shifts the processing to S108. Since the accuracy of the neutral estimation of the steering wheel 7 is improved in S106, the estimation accuracy of the steering neutral angle θc is also improved.

Θc = (1−λ) θd + λθc (n−1) (2) where λ is a forgetting factor (0 ≦ λ <1), and the weight for the past input is determined. That is, the smaller the forgetting factor λ, the greater the influence of the latest parameter (for example, the previous steering neutral angle θc) in the sequential calculation, and the stronger the degree of removing the influence of the past parameter. On the contrary, as the forgetting factor λ is increased, the latest parameter and the relatively old parameter influence the current parameter with the same weight.

Θd is a steering relative angle sampled when all the sampling conditions defined by the vehicle speed V, the steering torque T, the steering angular velocity ω, and the yaw rate Y are satisfied, and is detected by the motor rotation angle sensor 5. It is obtained based on the rotation angle of the electric motor 3. θc
(N-1) is the steering neutral angle estimated last time.

In S108, the CPU 21 executes S107.
The steering absolute angle (actual steering angle) θ based on the steering neutral angle θc estimated in (3) is calculated based on the following equation (3). Since the estimation accuracy of the steering neutral angle θc is improved in S107, the accuracy of the steering absolute angle θ is also improved.

Θ = θd−θc (3) Here, θd is a steering relative angle, which is obtained based on the rotation angle of the electric motor 3 detected by the motor rotation angle sensor 5. θc is the steering neutral angle previously estimated and calculated. For example, immediately after the engine is started, the steering neutral angle θc stored when the engine was stopped last time is used as the initial value (temporary value) of this time.

After that, the CPU 21 repeats the processing of S101 to S108 at every predetermined control cycle. The motor rotation angle sensor 5, the relative angle calculation means 36, and the differential calculation means 39 constitute steering angular velocity detection means. The torque sensor 11 constitutes a steering torque detecting means. The front wheels 18 form left and right wheels. The vehicle speed sensor 19 constitutes a vehicle speed detecting means and a wheel speed detecting means. The yaw rate sensor 20 constitutes vehicle direction determination means and yaw rate detection means. The relative angle calculation means 36 constitutes a steering angle detection means. The yaw rate Y constitutes the vehicle direction information.

(Effects of the Embodiment) Therefore, according to this embodiment, the following effects can be obtained. (1) When a predetermined sampling condition defined by the vehicle speed V, the steering torque T, the steering angular velocity ω, and the yaw rate Y is satisfied, the steering wheel 7 is estimated to be in the neutral position. Then, the steering neutral angle θc is estimated based on the steering relative angle θd sampled at this time. Therefore, for example, even when the vehicle is turning at a low speed such that the steering torque T is not generated, this is detected by the yaw rate sensor 20 (yaw rate Y ≠).
0). Therefore, regardless of whether the sampling conditions defined by the vehicle speed V, the steering torque T, and the steering angular velocity ω are correct or incorrect, the accuracy of neutral estimation of the steering wheel 7 can be improved. As a result, the estimation accuracy of the steering neutral angle θc can be improved.

Incidentally, if the sampling condition defined by the yaw rate Y is omitted, the turning when the steering torque T = 0 cannot be detected, and the steering wheel 7 is in the neutral position even though it is not in the neutral position. It is estimated that As a result, the estimation accuracy of the steering neutral angle θc may not be ensured.

(2) Thresholds that define the boundary conditions of the vehicle speed V, the steering torque T, the steering angular velocity ω, and the yaw rate Y, that is, the vehicle speed determination threshold Vs, the steering torque determination threshold Ts, the steering angular velocity determination threshold ωs, and the yaw rate determination threshold Ys. Provided. The vehicle speed V is higher than the vehicle speed determination threshold Vs, and the absolute value | T | of the steering torque T and the absolute value | ω of the steering angular velocity ω are
If the absolute value | Y | of the yaw rate Y is smaller than the steering torque determination threshold Ts, the steering angular velocity determination threshold ωs, and the yaw rate determination threshold Ys, it is determined that the neutral estimation is established. The steering torque T, the vehicle speed V, and the yaw rate Y include noise components, and there are some detection errors.
In consideration of this detection error, the steering torque determination threshold value Ts, the steering angular velocity determination threshold value ωs, and the yaw rate determination threshold value Ys are set. The steering torque determination threshold value Ts, the steering angular velocity determination threshold value ωs, and the yaw rate determination threshold value Ys are values greater than 0 and close to 0 (that is, Ts, ω).
s, Ys≈0). Therefore, the neutral estimation processing of the steering wheel 7 can be performed in consideration of the detection errors of the steering torque T, the vehicle speed V, and the yaw rate Y.

(Other Example) The above embodiment may be modified as follows. -In this embodiment, the yaw rate Y is detected by the yaw rate sensor 20, but the following may be adopted. That is, the yaw rate Y is calculated based on the rotational speed difference ΔV based on the rotational speed difference ΔV between the left and right front wheels or the left and right rear wheels based on the wheel speeds detected by the vehicle speed sensors 19 provided on the left and right front wheels or the left and right rear wheels, respectively. presume. In this case, for example, a rotational speed difference ΔV-yaw rate Y characteristic map is provided in advance, and the yaw rate Y is calculated from the rotational speed difference ΔV by referring to this characteristic map. Even in this way, the yaw rate Y can be detected. By the way, if the rotational speed difference ΔV between the left and right front wheels or the left and right rear wheels is 0, the yaw rate Y is also 0. That is, if the rotational speed difference ΔV between the left and right wheels is 0, the vehicle can be estimated to be in a straight traveling state
If the rotational speed difference ΔV is generated between the left and right wheels, it can be estimated that the vehicle is turning in the left-right direction. Also, the yaw rate Y increases as the rotational speed difference ΔV increases.

The sampling condition defined by the yaw rate Y may be replaced with the sampling condition defined by the rotational speed difference ΔV between the left and right wheels detected by the vehicle speed sensor (wheel speed sensor) 19. In this case, the rotation speed difference determination threshold value ΔVs that defines the boundary condition of the rotation speed difference ΔV between the left and right wheels is set (ΔVs≈
0). The rotation speed difference determination threshold value ΔVs is set for the rotation speed difference ΔV in this way because the detection signal of the vehicle speed sensor 19 contains a noise component. And │
When ΔV│ <ΔVs, the CPU 21 determines that the neutral estimation is established, and otherwise determines that the neutral estimation is not established.
Even in this case, the moving direction of the vehicle can be detected (that is, whether the vehicle is in the straight traveling state or the turning state is determined), and the neutral estimation of the steering wheel 7 can be performed based on the detection result.

The sampling condition defined by the yaw rate Y (neutral estimation condition) is replaced with the sampling condition defined by the rotational speed difference ΔN between the left and right wheels detected by the vehicle speed sensor (wheel speed sensor) 19. Good. In this case, a rotation speed difference determination threshold ΔNs that defines the boundary condition of the rotation speed difference ΔN between the left and right wheels is set (Δ
Ns≈0). When | ΔN│ <ΔNs, the CPU
21 determines that the neutral estimation is established, and otherwise determines that the neutral estimation is not established. Even in this case, the moving direction of the vehicle can be detected (that is, whether the vehicle is in the straight traveling state or the turning state is determined), and the neutral estimation of the steering wheel 7 can be performed based on the detection result.

In the present embodiment, the motor rotation angle sensor 5
Although the steering relative angle θd is calculated based on the motor rotation angle θm detected by, the steering shaft 8 is provided with a steering angle sensor (not shown), and the steering angle sensor detects the steering relative angle θd. You may do it. By doing so, the relative angle calculation means 36 becomes unnecessary.

(Supplementary Notes) Next, the technical ideas that can be understood from the above-described embodiment and other examples will be additionally described below. The electric vehicle according to claim 2, wherein the vehicle speed detecting means also functions as a wheel speed detecting means, and the yaw rate detecting means obtains a yaw rate based on a rotational speed difference between the left and right wheels detected by the wheel speed detecting means. Power steering device control device.

A vehicle speed judgment threshold value Vs, a steering torque judgment threshold value Ts, a steering angular speed judgment threshold value ωs, and a yaw rate judgment threshold value Ys that define the boundary conditions of the vehicle speed, the steering torque, the steering angular speed, and the vehicle direction information are provided, and the vehicle speed V is the vehicle speed. Greater than the determination threshold value Vs and the absolute value | T of the steering torque T
│, the absolute value │ω│ of the steering angular velocity ω, and the absolute value │Y│ of the yaw rate Y are smaller than the steering torque determination threshold Ts, the steering angular velocity determination threshold ωs, and the yaw rate determination threshold Ys, respectively, it is determined that the neutral estimation is established. The control device for an electric power steering device according to any one of claims 1 to 3.

[0077]

According to the present invention, in addition to the predetermined sampling condition defined by the vehicle speed, the steering torque, and the steering angular velocity, the sampling condition defined by the vehicle direction information is provided. The accuracy of neutral estimation can be improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electric power steering device according to an embodiment.

FIG. 2 is a functional block diagram of a control device of the electric power steering device according to the present embodiment.

FIG. 3 is a flowchart showing steering neutrality estimation processing according to the present embodiment.

FIG. 4 is a flowchart showing a conventional steering neutrality estimation process.

[Explanation of symbols]

1 ... Electric power steering device, 2 ... Control device, 5 ...
A motor rotation angle sensor that constitutes steering angular velocity detection means, 7
... steering wheel (steering wheel), 11 ... torque sensor forming steering torque detecting means, 18 ... front wheels forming left and right wheels, 19 ... vehicle speed detecting means, vehicle speed sensor (wheel speed sensor) forming wheel speed detecting means, 20 ... Vehicle direction determining means, yaw rate sensor constituting yaw rate detecting means, 36 ... Relative angle calculating means constituting steering angle detecting means, steering angular velocity detecting means, 37 ... Neutral angle estimating means, 39
Derivative calculation means constituting steering angular velocity detecting means, T ... Steering torque, V ... Vehicle speed, ω ... Steering angular velocity, Y ... Yaw rate constituting vehicle direction information, θc ... Steering neutral angle (estimated value), θd ... Steering relative Angle, ΔV ... difference in rotational speed.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B62D 119: 00 B62D 119: 00 137: 00 137: 00 (72) Inventor Shinji Takeuchi Asahi-cho, Kariya city, Aichi prefecture 1-1, Toyoda Machinery Co., Ltd. (72) Inventor Yoshiyuki Yasui 2-1-1, Asahi-machi, Kariya City, Aichi Prefecture In-house Aisin Seiki Co., Ltd. (72) Kenji Asano 2-chome, Asahi-cho, Kariya City, Aichi Prefecture Address A-Shin Seiki Co., Ltd. F-term (reference) 3D032 DA03 DA09 DA23 DA33 EB08 EC30 3D033 CA12 CA13 CA17 CA19

Claims (3)

[Claims] 1. A vehicle speed detected by a vehicle speed detecting means,
It is determined whether or not a predetermined sampling condition defined by the steering torque detected by the steering torque detection unit and the steering angular velocity detected by the steering angular velocity detection unit is satisfied, and the predetermined sampling condition is satisfied. If it is determined that the steering wheel is in the neutral position, the steering wheel is estimated to be in the neutral position, and based on the steering relative angle detected by the steering angle detecting means, the steering neutral angle estimating means for estimating the steering neutral angle is provided. In the control device of the power steering device, a vehicle direction determining means for detecting a moving direction of the vehicle is provided, and the neutral angle estimating means is defined by vehicle direction information from the vehicle direction determining means in addition to the predetermined sampling condition. The steering wheel is presumed to be in the neutral position when it is determined that the sampling conditions are satisfied. Control device for the electric power steering device. 2. The control device for an electric power steering apparatus according to claim 1, wherein the vehicle direction determination means includes yaw rate detection means for detecting a yaw rate of the vehicle. 3. The control device for an electric power steering system according to claim 1, wherein the vehicle direction determination means includes wheel speed detection means for detecting a difference in rotational speed between the left and right wheels.