JP2004210232A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of changing steering auxiliary force by detecting driver's force characteristic and compensating a control value of an electric motor based on the detected force characteristic and having great change of steering auxiliary force. <P>SOLUTION: When driver's force characteristic value P is in a first region A<SB>1</SB>(predetermined value P<SB>1</SB>≤ P < predetermined value P<SB>2</SB>), first compensation amount L = L<SB>1</SB>composed of a fixed positive value is set. When driver's force characteristic value P is in a second region A<SB>2</SB>(predetermined value P<SB>5</SB>≤ P), second compensation amount L = - L<SB>2</SB>composed of a fixed negative value is set. The set compensation amount L is added to a basic control value to obtain the control value of the electric motor. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering device that generates a steering assist force by controlling the driving of an electric motor based on a control value.
[0002]
[Prior art]
2. Description of the Related Art An electric power steering device (EPS) for a vehicle includes an electric motor, generates a steering assist force by the electric motor, and assists the driver's steering by applying the generated steering assist force to, for example, a steered shaft. I do. This makes the steering by the driver comfortable.
Also, in order to make the steering by the driver more comfortable, an electric power steering device that detects the driver's power characteristics and increases or decreases the steering assist force generated by the electric motor based on the detected power characteristics is proposed. (For example, see Patent Document 1). Thus, a force characteristic when the driver grips the steering member is detected, and a steering assist force corresponding to the driver's physical strength or the like is generated.
[0003]
[Patent Document 1]
JP-A-11-321671.
[0004]
[Problems to be solved by the invention]
However, the electric power steering device disclosed in Patent Document 1 linearly increases the amount of correcting the steering assist force as the driver's grip force increases. For this reason, there is a possibility that the steering assist force greatly changes depending on whether the same driver has weakened or increased the gripping force on the steering member, giving the driver an uncomfortable feeling.
The present invention has been made under such a background, and an object of the present invention is to provide an improved electric power steering device that enables a driver to perform steering comfortably without feeling uncomfortable.
[0005]
Means for Solving the Problems and Effects of the Invention
In order to achieve the above object, a first aspect of the present invention is an electric power steering device that generates a steering assist force by drivingly controlling an electric motor based on a control value, wherein a force characteristic detecting unit that detects a force characteristic of a driver includes: Correction means for setting a correction amount based on the force characteristic detected by the force characteristic detection means, and correcting the control value of the electric motor using the correction amount. And has a function of limiting the correction amount according to the force characteristic detected.
[0006]
According to the present invention, the amount by which the control value of the electric motor is corrected is limited, so that the change in the steering assist force does not become too large, and the driver does not feel uncomfortable.
In a second aspect based on the first aspect, the correction means sets a first correction amount having a constant positive value when the force characteristic value detected by the force characteristic detection means is in the first region. Then, a second correction amount having a constant negative value is set in a second area having a larger force characteristic value than the first area.
[0007]
According to the present invention, for example, when a relatively weak force of a woman or an elderly person is gripping the steering member, and the force characteristic value of the driver is relatively small, a correction amount consisting of a constant positive value is added. To set the control value. Further, for example, when the force characteristic value of the driver is relatively large, for example, when a man with relatively strong power is gripping the steering member, the control value is set by adding a correction amount consisting of a constant negative value. For this reason, a steering assist force can be generated according to the physical strength of the driver.
[0008]
Further, when the force characteristic value of the driver is in the first or second region, the correction amount is constant. Therefore, even if the same driver slightly changes the force, the change in the steering assist force is unnecessary. do not do. Therefore, a comfortable steering feeling can be achieved.
In a third aspect based on the second aspect, the correction means is provided when the force characteristic value detected by the force characteristic detection means is in a third area which is intermediate between the first area and the second area. , The correction amount is set to zero.
[0009]
According to the present invention, for example, when the driver is gripping the steering member in an appropriate strength range, the control value is not corrected, so that there is no unnecessary increase or decrease in the steering assist force, and a comfortable steering feeling can be achieved. .
In a fourth aspect based on the second or third aspect, the correction means is detected by the force characteristic detection means when the force characteristic value detected by the force characteristic detection means is smaller than the first area. It is characterized in that the correction amount is increased in accordance with an increase in the force characteristic value.
[0010]
According to the present invention, the correction amount curve is smoothly connected to the first region from the region where the force characteristic value is smaller than the first region where the correction amount is constant, and the driver does not feel uncomfortable.
In a fifth aspect based on the third or fourth aspect, the correction means is a fourth area in which the force characteristic value detected by the force characteristic detection means is between the first area and the third area. , And in a fifth area between the third area and the second area, the correction amount is reduced in accordance with an increase in the force characteristic value detected by the force characteristic detecting means.
[0011]
According to the present invention, the correction amount curve is smoothly connected between the regions where the correction amount is constant, and the driver does not feel uncomfortable.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering device according to one embodiment of the present invention. With reference to FIG. 1, the electric power steering apparatus 1 includes a first steering shaft 3a that is integrally rotatably connected to a steering member, for example, a steering wheel 2, and a first steering shaft 3a and a torsion bar 3b. A second steering shaft 3c that is coaxially connected to the second steering shaft 3c; and a steering mechanism 5 that is connected to the second steering shaft 3c and that includes a rack-and-pinion mechanism for achieving steering of the steered wheels 4.
[0013]
The steering mechanism 5 is arranged to extend in the left-right direction of the vehicle, and is connected to a steered shaft 6 that is movable along the axial direction via tie rods 7 at both ends of the steered shaft 6. A supporting knuckle arm 8.
A rack 9 is formed on a part of the steered shaft 6, and a pinion 10 provided at an end of the second steering shaft 3 c and integrally rotating with the second steering shaft 3 c meshes with the rack 9. I have. When the first and second steering shafts 3a, 3c are rotationally driven in response to the operation of the steering wheel 2, the rotation is converted by the pinion 10 and the rack 9 into the movement of the steered shaft 6 in the axial direction. Steering of the steering wheel 4 is achieved.
[0014]
The steered shaft 6 is supported by the housing 11 and is slidable in the axial direction. An electric motor 12 for generating a steering assist force is incorporated in, for example, a middle portion of the housing 11. The rotation of the electric motor 12 is converted into an axial movement of the steered shaft 6 by a motion converting mechanism (not shown) such as a ball screw mechanism, and the steered wheels 4 are steered. By turning the steered wheels 4 by the rotation of the electric motor 12, the steering of the driver is assisted. The electric motor 12 is controlled by a control unit C that drives and controls the electric motor 12 based on a control value.
[0015]
The steering wheel 2 is provided with, for example, a force characteristic detection sensor 13 as force characteristic detection means for detecting a driver's force characteristic (for example, grip force) applied to the steering wheel 2. The force characteristic detection sensor 13 includes, for example, an electrode 13a disposed on the steering wheel 2, and an impedance converter 13b connected to the electrode 13a.
The electrode 13a is disposed on the steering wheel 2 at a position where the driver normally grips (such as a position at 8:20). The electrode 13a is arranged flush with the surface of the steering wheel 2 so that when the driver grips the steering wheel 2, the driver can touch the palm of the driver without any discomfort.
[0016]
Further, an impedance converter 13b is connected to the electrode 13a so that the influence of environmental noise picked up by the electrode 13a can be removed. More specifically, when the driver grips the steering wheel 2, the palm of the driver contacts the electrode 13a. The body potential of the driver detected by the electrode 13a fluctuates depending on the contact ratio, the contact pressure, and the like. Therefore, the potential detected by the electrode 13a is passed through the impedance converter 13b to output, for example, about μV, and the difference in the situation where the palm of the driver is in contact with the electrode 13a, that is, the influence of environmental noise is removed. Have been to be. In other words, by using the electrode 13a as an active electrode, the detection capability of the electrode 13a is improved. The force characteristic detection sensor 13 outputs a detection signal corresponding to the detected force characteristic to the control unit C.
[0017]
In the above-described force characteristic detection sensor 13, the grip force of the driver holding the steering wheel 2 is detected using the contact resistance generated at the electrode 13a, but is not limited thereto, and may be detected using a piezoelectric element, a pressure-sensitive semiconductor, or the like. It is also possible. Further, the output signal from the force characteristic detection sensor 13 may be time-integrated via an integration circuit and provided to the control unit C.
A torque sensor 14 is provided near the torsion bar 3b. The torque sensor 14 detects an operation torque applied to the first and second steering shafts 3a, 3c based on a relative rotational displacement of the first and second steering shafts 3a, 3c via the torsion bar 3b. . The detection signal of the torque sensor 14 is output to the control unit C. Further, a detection signal from a vehicle speed sensor 15 that detects a vehicle speed is input to the control unit C.
[0018]
The control unit C includes a basic control value setting unit 17 that sets a basic control value based on detection signals given from the torque sensor 14 and the vehicle speed sensor 15 by a program process performed by a microcomputer provided therein, and a force characteristic detection sensor 13. A correction amount L is set based on the detected force characteristic, and the correction amount setting unit 18 and the correction amount setting unit 18 are used as correction means for correcting the basic control value using the correction amount L. Each function of the adding unit 19 that adds the correction amount L to the basic control value set by the basic control value setting unit 17 is realized.
[0019]
The control unit C adds the correction amount L and the basic control value in the addition unit 19, and sends a control signal to the drive circuit 16 as a drive unit for driving the electric motor 12 based on the control value obtained by the addition. Is output.
The drive circuit 16 supplied with the control signal from the control unit C supplies electric power to the electric motor 12 and drives the electric motor 12 to generate a steering assist force.
Further, a detection signal of the torque sensor 14 is input to the correction amount setting unit 18 of the control unit C, and when a driver operates the steering wheel 2 to generate an operation torque, a correction is performed. The amount is set. That is, when the vehicle is traveling straight and no operation torque is generated, the correction amount is not set.
[0020]
FIG. 2 is a characteristic diagram showing a relationship between a driver's force characteristic value P detected by the force characteristic detection sensor 13 and a correction amount L set by the correction amount setting unit 18 based on the force characteristic value P. is there. Referring to FIG. 2, correction amount setting unit 18 has a function of limiting correction amount L according to force characteristic value P detected by force characteristic detection sensor 13.
When the force characteristic value P detected by the force characteristic detection sensor 13 is in the first area A ₁ (predetermined value P ₁ ≦ P <predetermined value P ₂ ), the correction amount setting unit 18 sets a constant positive value L _{A first} correction amount L consisting of 1 is set.
[0021]
The correction amount setting unit 18, the force characteristic detected by the detecting sensor 13 force characteristic value P is greater second region of the first force characteristic value than the region A ₁ A _{2 (predetermined} value P ₅ ≦ P when in), and sets the second correction amount L consisting of constant negative value -L _2.
On the other hand, the correction amount setting unit 18 determines that the force characteristic value P detected by the force characteristic detection sensor 13 is in the third area A ₃ (predetermined value) which is located between the first area A ₁ and the second area A _2. When P ₃ ≦ P <predetermined value P ₄ ), the correction amount L is set to zero.
[0022]
Further, when the force characteristic value P detected by the force characteristic detection sensor 13 is in the region A ₀ (0 ≦ P <P ₁ ) where the force characteristic value is smaller than the first region A _1, The correction amount L is increased, for example, linearly in accordance with an increase in the force characteristic value P detected by the force characteristic detection sensor 13.
In addition, the correction amount setting unit 18 determines that the force characteristic value P detected by the force characteristic detection sensor 13 is in the fourth area A ₄ (P) between the first area A ₁ and the third area A _{3. 2} ≦ P <P ₃ ) and a fifth characteristic area A ₅ (P ₄ ≦ P <P ₅ ) between the third area A ₃ and the second area A ₂ , the force characteristic detection sensor The correction amount L is decreased, for example, linearly in accordance with an increase in the force characteristic value P detected by the control unit 13.
[0023]
FIG. 3 is a flowchart illustrating a process of setting the correction amount L performed by the correction amount setting unit 18 of the control unit C. Referring to FIG. 3, the correction amount setting unit 18 monitors the operation torque detected by the torque sensor 14 (Step S1).
When the driver does not operate the steering wheel 2 and no operation torque is generated (NO in step S1), the correction amount setting unit 18 does not shift to subsequent processing. As a result, a control value based on only the correction amount L is set, and the drive control of the electric motor 12 by this control value is prevented. Therefore, no steering assist force based on only the driver's force characteristics is generated.
[0024]
When an operation torque is generated by the driver operating the steering wheel 2 (YES in step S1), the control unit C determines the force characteristic value P of the driver (step S2).
When the driver's force characteristic value P detected by the force characteristic detection sensor 13 is in a region A ₀ (0 ≦ P <P ₁ ) smaller than the predetermined value P ₁ (YES in step S2), the correction amount setting unit 18 The correction amount L is increased in accordance with the increase in the force characteristic value P. (Step S3).
[0025]
Thus, the correction amount first region _A 1 L is constant _{(P 1} ≦ P _{<P 2)} smaller areas _{A 0} of force characteristic value P than the first region _A 1 _{(P 1} ≦ P < The correction amount curve is smoothly connected to P ₂ ), and the driver does not feel uncomfortable.
The first area A ₁ (P ₁ ≦ P <P) in which the driver's force characteristic value P detected by the force characteristic detection sensor 13 is equal to or more than the predetermined value P ₁ (NO in step S2) and less than the predetermined value P ₂ when in ₂₎ (YES at step S4), and the correction amount setting unit 18 sets the correction amount L to L = _{L 1} (step S5).
[0026]
That is, for example relatively weak women and elderly force is or are gripping the steering wheel 2, (corresponding to the first region A ₁₎ when the force characteristic value P of the driver is relatively small, as described above a correction amount L = L ₁ which is set to a constant value, but sets the control value by adding to the basic control value, if the force characteristic value P of the driver is in the first area a _1, the same operation Even if the user slightly changes the grip force, the steering assist force does not change unnecessarily. Therefore, a comfortable steering feeling can be achieved.
[0027]
Further, the correction amount L, because it limits so as not to exceed a certain positive value L _1, not too large change in the steering assist force, never discomfort to the driver.
Force characteristic detecting the magnitude P of the sensed force characteristic by sensor 13 at a predetermined value _{P 2} or more (NO in Step S4), and the fourth region _A 4 less than the predetermined value _{P 3 (P 2} ≦ P _{<P 3} ) (YES in step S6), the correction amount setting unit 18 decreases the correction amount L in accordance with the increase in the force characteristic value P (step S7).
[0028]
Accordingly, the correction amount L ties correction curve smoothly between the first region A ₁ and the third region A ₃ is a constant, not to give the driver a sense of discomfort.
Force characteristic value P detected by the force characteristic detecting sensor 13 is at a predetermined value _{P 3} or more (step S6 in NO), and the third region _A 3 is less than the predetermined value _{P 4 (P 3} ≦ P _{<P 4)} If there is (YES in step S8), the correction amount setting unit 18 sets the correction amount L to L = 0 (step S9).
[0029]
As a result, for example, when the driver is gripping the steering wheel 2 within an appropriate strength range, the control value is not corrected, so that there is no unnecessary increase or decrease in the steering assist force, and a comfortable steering feeling can be achieved.
Force characteristic detected by the detecting sensor 13 force characteristic value P is at a predetermined value _{P 4} or more (NO in step S8), and and the fifth region _A 5 less than the predetermined value _{P 5 (P 4} ≦ P _{<P 5)} If there is (YES in step S10), the correction amount setting unit 18 performs the process of step S7.
[0030]
Accordingly, the correction amount L leads to smooth the correction amount curve between the third region A ₃ and the second region A ₂ is constant (zero), not to give the driver a sense of discomfort.
When the force characteristic value P detected by the force characteristic detection sensor 13 is in the second area A ₂ (P ₅ ≦ P) equal to or greater than the predetermined value P ₅ (NO in step S10), the correction amount setting unit 18 setting the amount L to L = -L ₂ (step S11).
[0031]
The correction amount L, because it limits so as not to fall below a certain negative value -L _2, not too large change in the steering assist force, never discomfort to the driver.
Furthermore, for example, when a relatively strong man is holding the steering wheel 2 or the driver's force characteristic value P is relatively large, the correction amount L = −L ₂ is added to the basic control value, Set the control value. That is, by subtracting the correction amount L ₂ from the basic control value, sets the control value. For this reason, a steering assist force can be generated according to the physical strength of the driver. Furthermore, if the force characteristic value P of the driver is in the second area A _2, the same driver even slightly changing the grip, steering assist force is not unnecessary changes. Therefore, a comfortable steering feeling can be achieved.
[0032]
The present invention is not limited to the contents of the above embodiments, and various changes can be made within the scope of the claims.
For example, a region where the correction value L changes according to the force characteristic value P detected by the force characteristic detection sensor 13 is a region A ₀ equal to or smaller than the _first region A ₁ , a fourth region A _4, and a fifth region. It has a configuration which is three of a _5, but is not limited thereto. For example, a configuration may be employed in which the areas A ₀ , A _4, and A ₅ are finely divided so that the change in the correction amount curve is made smoother and the change in the correction value L is made smoother. .
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering device according to an embodiment of the present invention.
FIG. 2 is a characteristic diagram illustrating a relationship between a driver's force characteristic value detected by a force characteristic detection sensor and a correction amount set by a correction amount setting unit based on the force characteristic value.
FIG. 3 is a flowchart illustrating a process of setting a correction amount performed by a correction amount setting unit of a control unit.
[Explanation of symbols]
12 Electric motor 13 Force characteristic detection sensor (force characteristic detection means)
18 Correction amount setting unit (correction means)
A ₀ Area A having a smaller force characteristic value than the first area A ₁ First area A ₂ Second area A ₃ Third area A ₄ Fourth area A ₅ Fifth area C Control unit L Correction amount L ₁ First correction amount−L ₂ Second correction amount P Force characteristic value

Claims (5)

In an electric power steering device that generates a steering assist force by driving control of an electric motor based on a control value,
Force characteristic detecting means for detecting a force characteristic of the driver;
A correction unit that sets a correction amount based on the force characteristic detected by the force characteristic detection unit, and corrects a control value of the electric motor using the correction amount,
The electric power steering apparatus according to claim 1, wherein the correction unit has a function of limiting a correction amount according to the force characteristic detected by the force characteristic detection unit. 2. The method according to claim 1, wherein the correction unit sets a first correction amount having a constant positive value when the force characteristic value detected by the force characteristic detection unit is in the first region. An electric power steering apparatus, wherein a second correction amount including a constant negative value is set when the second power correction value is in a second region having a large force characteristic value. The correction means according to claim 2, wherein the correction means sets the correction amount to zero when the force characteristic value detected by the force characteristic detection means is in a third area intermediate between the first area and the second area. An electric power steering device, comprising: The correction means according to claim 2 or 3, wherein when the force characteristic value detected by the force characteristic detection means is smaller than the first area, the correction means responds to an increase in the force characteristic value detected by the force characteristic detection means. An electric power steering device characterized by increasing a correction amount. 5. The device according to claim 3, wherein the correction unit includes a fourth region in which the force characteristic value detected by the force characteristic detection unit is between the first region and the third region, and An electric power steering apparatus characterized in that a correction amount is decreased in accordance with an increase in a force characteristic value detected by a force characteristic detecting means in a fifth region between the second region and the fifth region.

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