JPH07228263A - Electric power steering device - Google Patents

Abstract

(57) [Abstract] [Object] The present invention relates to an electric power steering apparatus, which increases the electric motor output only when kickback from the road surface is large even when traveling on a bad road where the road surface μ is low, and the steering force is not unnecessarily increased. The purpose of this is to prevent the steering feeling from being deteriorated by making it lighter. [Structure] A steering torque change amount detection means M4 detects a steering torque change amount. The steering angular velocity detection means M5 detects the steering angular velocity. The kickback determination means M6 determines that the kickback has occurred when the detected steering angular velocity is smaller than the predetermined value and the detected steering torque is larger than the predetermined value. When it is determined that a kickback has occurred, the correction means M7 increases and corrects the electric motor output in the direction of canceling the kickback. Furthermore, the rough road determination means M8 further determines the rough road running state.

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 apparatus, and more particularly to an electric power steering apparatus for vehicles such as automobiles.

[0002]

2. Description of the Related Art An electric power steering apparatus for a vehicle such as an automobile has heretofore generally been a motor for driving a steering linkage member such as a rack bar via a clutch and a steering gear box, and a controller for controlling the rotation of the motor. The control device is configured to generate a required steering assist force by controlling the motor based on the detection results of various sensors.

An example of such an electric power steering device is disclosed in Japanese Patent Application Laid-Open No. 2-296574.

This device determines whether or not the vehicle is traveling on a rough road, and when the vehicle is traveling on a rough road, the output torque assist amount is increased to increase the steering holding force and prevent the steering wheel from being taken on a rough road.

[0005]

Since the conventional device determines the output torque assist amount depending on whether or not the vehicle is traveling on a rough road, it is always possible to travel on a rough road where the friction coefficient μ of the road surface is relatively low. The output torque assist force is increased.
However, if the road surface μ is small, the road surface reaction force is small and the steering holding force can be small, but since the output torque assist force is increased, the steering force of the driver is lightened as a whole and the overall steering feel is reduced. There was a problem that the ring got worse.

The present invention has been made in view of the above points, and determines the occurrence of kickback from the steering torque change amount and the steering angular velocity and corrects the electric motor output.
An object of the present invention is to provide an electric power steering device that prevents the steering force from being unnecessarily lightened and the overall steering feeling from being deteriorated.

[0007]

FIG. 1 shows the principle of the present invention.

In the figure, the steering torque detecting means M1 detects the steering torque, and based on this steering torque, the control means M2 drives the electric motor M3 to perform auxiliary steering.

The steering torque change amount detecting means M4 detects the steering torque change amount.

The steering angular velocity detecting means M5 detects the steering angular velocity.

The kickback judging means M6 judges that the kickback is occurring when the detected steering angular velocity is smaller than the predetermined value and the detected steering torque is larger than the predetermined value.

When it is determined that a kickback has occurred, the correcting means M7 increases and corrects the electric motor output in the direction of canceling the kickback.

Further, the correction means M7 increases the correction amount of the damper control of the electric motor.

Further, the correcting means M7 increases the inertia compensation control value of the electric motor.

Further, the rough road judging means M8 judges the rough road running state. In this case, the correction means M7 corrects the electric motor output when it is determined that the vehicle is traveling on a rough road and a kickback has occurred.

[0016]

According to the present invention, since the electric motor output is corrected by determining the occurrence of kickback from the steering torque change amount and the steering angular velocity, the kickback from the road surface is large even when the road surface is low and the road μ is low. Only by increasing the electric motor output, it is possible to prevent the steering force from being unnecessarily reduced and the overall steering feeling from being deteriorated.

Further, since the correction amount of the damper control is increased when the kickback is large, the convergence of the movement of the steering wheel due to the kickback is improved.

Further, when the kickback is large, the correction amount of the inertia compensation control is increased, so that the electric motor output is increased before the steering wheel is moved by the kickback, and the movement of the steering wheel can be suppressed.

Further, since the kickback state is detected only when traveling on a rough road, there is no possibility of false detection of kickback.

[0020]

2 is a schematic block diagram showing an embodiment of an electric power steering apparatus according to the present invention, and FIG. 3 is a block diagram showing the electronic control apparatus shown in FIG.

In FIG. 2, reference numeral 10 denotes a steering wheel. The steering wheel 10 drives a rack bar 16 via a steering shaft 12 and a steering gear box 14. A power unit 20 is drivingly connected to the steering shaft 12 by a gear reduction mechanism 18. Power unit 20
Has a motor 22 and an electromagnetic clutch 24 for selectively drivingly connecting the gear reduction mechanism 18 and the motor 22.

The steering shaft 12 is provided with a steering angle sensor 26 for detecting a steering angle θ and a torque sensor 28 for detecting a steering torque T, and a motor 22 is provided with a rotation angle sensor 36. Is output to the electronic control unit 32. Further, the electronic control unit 32 is a signal indicating the vertical acceleration of each of the right front wheel (FR), the left front wheel (FL), the right rear wheel (RR), and the left rear wheel (RL) detected by the acceleration sensors 30a to 30d. , And a signal indicating the vehicle speed V detected by the vehicle speed sensor 34, and the estimated road surface μ from the other system 31.

The electronic control unit 32 includes a microcomputer 38, as shown in FIG.
8 is a central processing unit (CPU) 40, a read only memory (ROM) 42, and a random access memory (R).
AM) 44, an input port device 46, and an output port device 48, which are connected to each other by a bidirectional common bus 50.

The steering angle sensor 26 is provided in the input port device 46.
A signal indicating the steering angle θ detected by the torque sensor 2
8, a signal indicating the steering torque T detected by the vehicle speed sensor 8, a signal indicating the vehicle speed V detected by the vehicle speed sensor 34, a signal indicating the rotation angle of the motor detected by the rotation sensor 36, and each of the acceleration sensors 30a to 30d. A signal indicating the vertical acceleration of each wheel and the estimated road surface μ from the other system 31 are input. The input port device 46 appropriately processes the signal input thereto, and outputs the processed signal to the CPU and the RAM 44 according to the instruction of the CPU 40 based on the control program stored in the ROM 42.

The ROM 42 stores a control program and a map. The CPU 40 performs various calculations and signal processing based on the control program as described later. The output port device 48 outputs a control signal to the motor 22 via the drive circuit 52 according to an instruction from the CPU 40, and outputs a control signal to the electromagnetic clutch 24 via the drive circuit 54.

FIGS. 4 and 5 show a flowchart of an embodiment of steering control processing executed by the electronic control unit 32. This process is started by closing an ignition switch not shown in FIG.

First, in step S10 of FIG. 4, the clutch is connected by supplying a control signal to the electromagnetic clutch 24 via the drive circuit 54, and in step S20, a signal indicating the steering angle θ detected by the steering angle sensor 26, A signal indicating the motor rotation angle θm detected by the rotation angle sensor 36, a signal indicating the steering torque T detected by the torque sensor 28, a signal indicating the vehicle speed V detected by the vehicle speed sensor 34, and detected by the acceleration sensors 30a to 30d. The signal indicating the vertical acceleration of each wheel is read.

In step S30, the basic assist amount Tab is calculated from the map shown in FIG. 6 based on the steering torque T read in step S20. In step S40, the basic assist amount Tab is calculated based on the vehicle speed V read in step S20. The vehicle speed coefficient Kv is calculated from the map shown in FIG. 7, and in step S50, the motor rotation angular speed Δθm is obtained by taking the difference from the previous value of the motor rotation angle θm read in step S20, and based on this Δθm, FIG. The damper control amount Td is calculated from the map shown. In step S60, the vehicle speed V
Based on the above, the damper vehicle speed coefficient Kd is calculated from the map shown in FIG. 9, and in step S70, the road surface μ value estimated by the antilock brake system (ABS) or the traction control system is read.

After that, in step S80 of FIG. 5, it is determined whether the estimated road surface μ value is equal to or smaller than a predetermined μ determination value μ ₀ (for example, μ ₀ = 0.5). High μ if the estimated road surface μ> μ ₀
It is determined that the road is a road, and the process proceeds to step S90, and the estimated road surface μ ≦ μ
_In the case of ₀ , it is determined that the road is a low μ road, and the process proceeds to step S100. In step S100, the road surface μ correction coefficient Kμ is calculated from the map shown in FIG. 10 based on the estimated road surface μ.

In the next step S110, the acceleration sensor 3
The correlation value C of the vertical acceleration of each wheel detected at 0a to 30d is calculated. Here, it is not necessary to calculate all the correlation values of each of the four wheels, and for example, only the correlation values of the right front wheel and the left rear wheel may be calculated. After this, the rough road determination means M8
In step S120 corresponding to, it is determined whether the correlation value C is less than or equal to a predetermined correlation determination value C ₀ . If the correlation value C> C ₀ , it is determined as a good road such as a paved road and the process proceeds to step S90. If the correlation value C ≦ C ₀ is determined as a bad road such as an unpaved road, the step S1.
Proceed to 30.

In step S130 corresponding to the steering angular velocity detecting means M5, the steering angular velocity Δθ is obtained by taking the difference between the present detected value θn of the steering angle θ and the detected value θn-k before k (eg, k = 1) times. Then, in the next step S140, it is determined whether or not the steering angular velocity Δθ is less than or equal to a predetermined determination value Δθ ₀ . Δ
When θ ≦ Δθ ₀ , the process proceeds to step S150 corresponding to the steering torque change amount detecting means M5, and the difference between the current detected value Tn of the steering torque T and the detected value Tn-k of k times before is calculated. The amount ΔT is obtained, and it is determined in step S160 whether the steering torque change amount ΔT is equal to or greater than a predetermined determination value ΔT ₀ .

Here, Δθ ≦ Δθ₀And ΔT ≧ ΔT₀of
If the reaction force from the road surface, that is, the kickback force is large,
It is determined and the process proceeds to step S170, where Δθ> Δθ₀Or Δ
T <ΔT₀In case of, it is judged that the kickback force is small.
It proceeds to step S90. That is, steps S140 and S
Reference numeral 160 corresponds to the kickback determination means M6. Su
In step S90, the kickback force is small, so the kick
Back coefficient K₁, K ₂Set 1 to each. Step
Since the kickback force is large in S170, the steering torque is
The kickback coefficient K is calculated by multiplying the change amount ΔT by a constant α.
₁Set to (ΔT ・ α ≧ 1) and kickback coefficient
K₂Is set to a constant β (β ≧ 1).

After the kickback coefficients K ₁ and K ₂ are set in step S90 or step S170, the correction means M is set.
In step S180 corresponding to step 7, the assist amount T _M
Is calculated by the following equation.

T _M = Tab · Kv · Kμ−Td · Kd · K ₁ + ΔT · Ki · K ₂ (1) where Ki is a constant as an inertia correction coefficient. (1)
The first term on the right side of the equation represents the assist amount according to the vehicle speed and the road surface μ. The second term on the right side represents the assist amount of damper control for suppressing the movement of the steering wheel when the steering wheel is moved by the kickback force, and improves the convergence of the steering wheel. The third term on the right side represents the assist amount of inertia compensation control for suppressing the movement of the steering wheel before the steering wheel is moved by the kickback force.

After that, the process proceeds to step S190, in which the control signal corresponding to the assist amount T _M is supplied to the motor 22 through the drive circuit 52, whereby the steering assist force is controlled in addition to that corresponding to the assist amount Ta. , And returns to step S20 in FIG.

That is, when the kickback force is small on the high μ road or the low μ road, the kickback correction coefficient, which is an element of the second and third terms on the right side of the equation (1), is fixed at 1. Therefore, when the kickback force is small on the low μ road, the correction coefficient Kμ according to the road surface μ of the first term on the right side becomes less than 1, so the assist amount T _M becomes smaller as the road surface μ becomes smaller. The steering feeling can be kept constant.

The correction coefficient Kμ is less than 1 even when the kickback force is large on a low μ road, but the kickback correction coefficient K
₁ , ₁ and K ₂ become 1 or more, and the correction amount of the damper control of the second term on the right side and the correction amount of the inertia compensation control of the third term on the right side increase. The increase in the correction amount of the damper control improves the convergence of the steering wheel that moves by kickback. Further, due to the increase in the correction amount of the inertia compensation control, the motor output torque increases before the steering wheel starts to move due to kickback, the movement of the steering wheel can be reduced, and the steering feeling is improved.

Further, since the process proceeds to steps S130 and S140 only when it is determined that the road is bad in step S120, it is prevented that the kickback is erroneously determined and the control is erroneous despite the good road.

FIG. 11 shows a block diagram of control of the device of the present invention. In the figure, the steering torque T is the phase compensation unit 1
The phase is compensated at 00 and supplied to the map 101 shown in FIG. 6, where the basic assist amount Tab is supplied to the read multiplier 102. The vehicle speed V is map 1 shown in FIG.
04, where the vehicle body coefficient Kv is read and supplied to the multiplier 102. Further, the estimated road surface μ is supplied to the map 106 shown in FIG. 10, where the correction coefficient Kμ is read out and supplied to the multiplier 102, and the multiplier 102 (1)
The first term on the right side of the equation is obtained and supplied to the adder 107.

Further, the steering torque T is differentiated by the differentiator 110 to obtain the steering torque change amount ΔT. This steering torque change amount ΔT is multiplied by the kickback coefficient K ₂ in the multiplier 111, and further multiplied by the inertia correction coefficient Ki in the multiplier 112, and the third term on the right side of the equation (1) is obtained and supplied to the adder 107. To be done.

Further, the vehicle speed V is supplied to the map 120 shown in FIG. 9 to obtain the damper vehicle speed coefficient Kd. This damper vehicle speed coefficient Kd is multiplied by the kickback correction coefficient K in the multiplier 121.
_It is multiplied by ₁ and supplied to the multiplier 122.

The motor rotation angle θm of the motor 22 is determined by the differentiator 1
The rotation angular velocity Δθm is obtained by differentiating by 23. This rotational angular velocity Δθm is supplied to the map 124 shown in FIG.
The damper control amount Td read here is supplied to the multiplier 122. The second term on the right side of the expression (1) obtained by the multiplier 122 is subtracted from the output of the adder 107 by the subtractor 123 to obtain the assist amount T _{M of the} expression (1).

The assist amount T _M is supplied to the subtractor 124, and the output of the current detector 125, which detects the current flowing through the motor 22, is subtracted for feedback and supplied to the drive circuit 52 to drive the motor 22. To be done.

[0044]

As described above, according to the electric power steering apparatus of the present invention, since the occurrence of kickback is determined from the steering torque change amount and the steering angular velocity to correct the electric motor output, the road surface μ is low. Even when the vehicle is running, the electric motor output can be increased only when the kickback from the road surface is large, and it is possible to prevent the steering force from being unnecessarily reduced and the overall steering feeling being deteriorated.

Further, when the kickback is large, the correction amount of the damper control is increased, so that the convergence of the movement of the steering wheel due to the kickback is improved.

Further, when the kickback is large, the correction amount of the inertia compensation control is increased, so that the electric motor output is increased before the steering wheel is moved by the kickback, and the movement of the steering wheel can be suppressed.

Furthermore, since the kickback state is detected only when the vehicle is traveling on a rough road, there is no risk of false kickback detection, which is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a schematic configuration diagram of the device of the present invention.

FIG. 3 is a block diagram of an electronic control unit.

FIG. 4 is a flowchart of steering control processing of the device of the present invention.

FIG. 5 is a flowchart of steering control processing of the device of the present invention.

FIG. 6 is a map of steering torque and basic assist amount.

FIG. 7 is a map of vehicle speed and vehicle speed coefficient.

FIG. 8 is a map of a motor rotation angular velocity and a damper control amount.

FIG. 9 is a map of vehicle speed and damper vehicle speed coefficient.

FIG. 10 is a map of road surface μ and road surface μ correction coefficient.

FIG. 11 is a control block diagram of the device of the present invention.

[Explanation of symbols]

 10 Steering Wheel 12 Steering Shaft 14 Steering Gear Box 22 Motor 24 Electromagnetic Clutch 26 Steering Angle Sensor 28 Torque Sensor 32 Electronic Control Device 34 Vehicle Speed Sensor 36 Rotation Sensor M1 Steering Torque Detecting Means M2 Control Means M3 Electric Motor M4 Steering Torque Change Detecting Means M5 Steering angular velocity detection means M6 Kickback determination means M7 Correction means M8 Bad road determination means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B62D 137: 00

Claims (4)

[Claims] 1. An electric power steering apparatus for driving an electric motor according to a steering torque to perform an auxiliary steering, a steering torque change amount detecting means for detecting a steering torque change amount, and a steering angular velocity detecting means for detecting a steering angular velocity. A kickback determining means for determining a kickback occurrence state when the detected steering angular velocity is smaller than a predetermined value and a detected steering torque larger than the predetermined value, and a kickback determination means for determining a kickback occurrence state. An electric power steering device comprising: a correction unit that increases and corrects the electric motor output in a direction in which the back is canceled. 2. The electric power steering device according to claim 1, wherein the correction unit increases a correction amount of damper control of the electric motor. 3. The electric power steering apparatus according to claim 1, wherein the correction unit increases an inertia compensation control value of the electric motor. 4. The electric power steering apparatus according to claim 1, claim 2 or claim 3, further comprising: bad road determination means for determining a bad road running state, wherein the correction means is for running on a bad road and kickbacks. An electric power steering apparatus, which corrects the electric motor output when it is determined that the electric power steering apparatus is in the generation state.