JP2004074833A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device for operating at steering torque determined irrespective of a road surface condition, and providing a natural steering feeling. <P>SOLUTION: The electric power steering device comprises a torque sensor 11 for detecting the steering torque, a steering angle sensor 10 for detecting a steering angle, a model steering means 20 for outputting a model steering angle on the basis of a model steering model 20a which determines a relation between the steering torque, and the model steering angle corresponding to the steering torque, and a means 21 for outputting a control signal for driving a motor M for steering assistance so that the model steering means 20 reduces a difference between the model steering angle outputted on the basis of the steering torque detected by the torque sensor 11 and the steering angle detected by the steering angle sensor 10. The model steering model 20a includes a structure of a secondary delay element 1/(Js<SP>2</SP>+Cs+K) comprising a moment of inertia J of a steering member, a friction coefficient C between the steering member and a supporting member, and a spring constant K when the steering member is regarded as a spring. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power comprising: a torque sensor for detecting a steering torque applied to a steering member of a vehicle; and control means for outputting a control signal for driving a steering assist motor based on the steering torque detected by the torque sensor. The present invention relates to a steering device.
[0002]
[Prior art]
2. Description of the Related Art An electric power steering device mounted on a vehicle assists a steering force of a vehicle by a motor, and is applied to a steering mechanism to which a steering member (a steering wheel and a steering shaft) is connected. A torque sensor for detecting a steering torque and a steering assist motor for assisting the operation of the steering mechanism are provided, and the steering assist motor is driven so as to obtain an assist force according to the steering torque detected by the torque sensor. Thereby, the operation force on the steering member is reduced. In addition, when the vehicle is running at high speed, an assist force according to the vehicle speed can be obtained so that the operation force on the steering member does not become too light.
[0003]
In such an electric power steering device, the assist force is predetermined in accordance with the steering torque and the vehicle speed. Therefore, the steering torque required for steering differs depending on the reaction force from the road surface and the vehicle side. This has the advantage that the driver can know the road surface condition and the like. However, a driver having a physical handicap and an elderly driver may have a possibility of being picked up by a steering wheel, and may want to operate with a predetermined steering torque regardless of the road surface condition.
Therefore, the present applicant has proposed an electric power steering device capable of switching between driving with a predetermined steering torque regardless of the road surface condition and driving with a conventional steering assisted steering torque, in Japanese Patent Application No. 2001-310526. In the proposal.
[0004]
[Problems to be solved by the invention]
In the above-described driving with the steering torque determined regardless of the road surface condition, since it is based only on the steering torque, it is not possible to obtain a natural steering feeling, and it is possible to obtain an assist force according to the vehicle speed. There is a problem that the steering feeling is not stable, the straightness of the vehicle is poor, and the return of the steering wheel is poor.
The present invention has been made in view of the circumstances described above, and in the first and second inventions, it is possible to drive at a predetermined steering torque regardless of the road surface condition and to obtain a natural steering feeling. It is an object of the present invention to provide an electric power steering device that can be used.
[0005]
A third object of the present invention is to provide an electric power steering device capable of operating at a steering angle with respect to a determined steering torque regardless of a road surface condition and obtaining an assist force according to a vehicle speed.
A fourth object of the present invention is to provide an electric power steering device capable of operating at a steering angle with respect to a predetermined steering torque regardless of a road surface condition and stabilizing a steering feeling.
It is an object of the fifth invention to provide an electric power steering device that can operate at a steering angle corresponding to a determined steering torque regardless of a road surface condition and has good straightness of a vehicle.
It is an object of the sixth invention to provide an electric power steering device which can operate at a steering angle with respect to a predetermined steering torque regardless of a road surface condition and has a good steering wheel return.
[0006]
[Means for Solving the Problems]
An electric power steering apparatus according to a first aspect of the present invention includes a torque sensor that detects a steering torque applied to a steering member, a steering angle sensor that detects a steering angle of the steering member, and a steering corresponding to the steering torque and the steering torque. A reference steering model that outputs a reference steering angle based on a reference steering model that defines a relationship of a reference steering angle that is an angle, a reference steering angle that the reference steering unit outputs based on a steering torque detected by the torque sensor, and Output means for outputting a control signal for driving a steering assist motor, in order to reduce the difference between the steering angles detected by the steering angle sensor, wherein the reference steering model comprises: It consists of a moment of inertia J of the steering member, a coefficient of friction C of the steering member with the support member, and a spring constant value K when the steering member is regarded as a spring. Next lag element 1 / (Js ² + Cs + K). (S is a complex variable)
[0007]
In this electric power steering apparatus, the output means includes a steering assist for reducing a difference between the reference steering angle output based on the steering torque detected by the torque sensor and the steering angle detected by the steering angle sensor. Outputs a control signal for driving the motor. The reference steering model for determining the relationship between the torque and the reference steering angle of the reference steering means is based on the assumption that the moment of inertia J of the steering member, the coefficient of friction C of the steering member with the support member, and the steering member are springs. Second order lag element 1 / (Js ² + Cs + K).
As a result, it is possible to realize an electric power steering device capable of operating at a steering angle corresponding to a determined steering torque regardless of road surface conditions and obtaining a natural steering feeling.
[0008]
An electric power steering device according to a second aspect of the present invention includes a motor for assisting steering, a torque sensor for detecting a steering torque applied to a steering member, a steering angle sensor for detecting a steering angle of the steering member, and a steering torque. And a relation between a reference steering angle which is a steering angle corresponding to the steering torque, and a moment of inertia J of the steering member, a coefficient of friction C between the steering member and a support member, and the steering member as a spring. The second order lag element 1 / (Js ² + Cs + K), a reference steering model that calculates and outputs a reference steering angle based on the reference steering model stored by the storage means, and a reference steering unit that detects the torque sensor. Calculating means for calculating the difference between the reference steering angle calculated and output based on the calculated steering torque and the steering angle detected by the steering angle sensor; and driving the motor to reduce the difference calculated by the calculating means. And output means for outputting the control signal.
[0009]
In this electric power steering apparatus, a secondary delay element 1 / (Js) that determines the relationship between the steering torque and a reference steering angle that is a steering angle corresponding to the steering torque. ² + Cs + K) is stored in the storage means, and based on the stored reference steering model, the reference steering means calculates and outputs a reference steering angle. The reference steering means calculates a difference between the reference steering angle calculated and output based on the steering torque detected by the torque sensor and the steering angle detected by the steering angle sensor, and the calculation means calculates the difference between the reference steering angle and the steering angle detected by the steering angle sensor. The output means outputs a control signal for driving the steering assist motor.
As a result, it is possible to realize an electric power steering device capable of operating at a steering angle corresponding to a determined steering torque regardless of road surface conditions and obtaining a natural steering feeling.
[0010]
An electric power steering device according to a third aspect of the present invention is a vehicle speed sensor for detecting a vehicle speed of the vehicle, and first changing means for changing the spring constant value K according to the vehicle speed detected by the vehicle speed sensor. And further comprising:
[0011]
In this electric power steering device, the spring constant value K of the secondary delay element of the reference steering model is changed to be large or small according to the level of the vehicle speed detected by the vehicle speed sensor. It is possible to realize an electric power steering device capable of operating at a steering angle and obtaining an assist force according to the vehicle speed.
[0012]
The electric power steering apparatus according to a fourth aspect of the present invention is characterized in that the electric power steering apparatus further includes a second changing unit that changes the friction coefficient value C according to the level of the vehicle speed detected by the vehicle speed sensor.
[0013]
In this electric power steering device, the friction coefficient value C of the secondary delay element of the reference steering model is changed to be large or small according to the level of the vehicle speed detected by the vehicle speed sensor. It is possible to realize an electric power steering device that can drive at the steering angle and stabilize the steering feeling.
[0014]
The electric power steering apparatus according to a fifth aspect of the present invention is characterized in that the electric power steering apparatus further includes a third changing unit that changes the inertia moment value J to a large or small value according to the level of the vehicle speed detected by the vehicle speed sensor.
In this electric power steering device, the inertia moment value J of the secondary delay element of the reference steering model is changed to be large or small according to the level of the vehicle speed detected by the vehicle speed sensor. An electric power steering device that can operate at a steering angle with respect to the steering torque and has good straightness of a vehicle can be realized.
[0016]
The electric power steering apparatus according to a sixth aspect of the present invention further includes a fourth changing unit that changes the spring constant value K to a small or large value according to the magnitude of the steering angle detected by the steering angle sensor. .
[0017]
In this electric power steering device, the spring constant value K of the secondary delay element of the reference steering model is changed to a small value according to the magnitude of the steering angle detected by the steering angle sensor. An electric power steering device that can operate at a steering angle with respect to the steering torque and has a good steering wheel return can be realized.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings showing the embodiments.
Embodiment 1 FIG.
FIG. 1 is a block diagram showing a main configuration of an electric power steering apparatus according to a first embodiment of the present invention. The electric power steering apparatus includes a torque sensor 11 for detecting a steering torque applied to a steering member (steering wheel and steering shaft) of a steering system 14, a steering assist motor M connected to the steering system 14, and a torque sensor. A first control means for outputting a first control signal for driving a steering assist motor based on a steering torque detected by the vehicle speed sensor and a vehicle speed detected by the vehicle speed sensor; A steering angle sensor 10 for detecting a steering angle.
[0019]
The electric power steering apparatus further includes a reference steering unit 20 that outputs a reference steering angle based on a reference steering model 20a that defines a relationship between the steering torque detected by the torque sensor 11 and the reference steering angle. A driving assist motor M for driving a steering assist motor M so as to reduce the deviation of the steering angle detected by the steering angle sensor 10 from the reference steering angle θd calculated and output based on the steering torque detected by the torque sensor 11. A second control means 21 for outputting a second control signal and a first switching means 18 for switching and outputting the first control signal and the second control signal are provided.
The reference steering unit 20 changes the reference steering model 20a according to the vehicle speed detected by the vehicle speed sensor 12 and the steering angle detected by the steering angle sensor 10.
[0020]
The electric power steering device also determines whether or not the behavior of the vehicle is abnormal by using a manual changeover switch 19 interlocked with the first switching means 18 and a yaw rate sensor, and when it is determined that the behavior is abnormal. A behavior determining means 13 for switching the first switching means 18 to the second control signal, an amplifier 16 for amplifying the control signal switched and output by the first switching means 18 in inverse proportion to a reduction ratio and a torque constant of the motor M, A PI controller 15 for providing a PI control signal to the motor M based on the control signal amplified by the amplifier 16.
[0021]
FIG. 2 is a block diagram showing the internal configuration of the second control means 21 and its related parts. The reference steering unit 20 includes a phase compensating unit 22 for compensating a phase delay of the steering torque. The reference steering model 20a includes a moment of inertia J of a steering member of the steering system 14, a coefficient of friction of the steering member with a support member. C and a second-order lag element 1 / (Js) consisting of a spring constant K when the steering member is regarded as a spring. ² + Cs + K), and is realized by software stored in a memory built in the reference steering means 20. (S is a complex variable)
[0022]
As shown in FIG. 3, the configuration of the steering member of the steering system 14 is such that a distal end of a steering shaft 53 that supports the steering wheel 50 is supported by a fixed portion via a spring 52, and an intermediate portion of the steering shaft 53 is supported. It can be shown schematically as supported by the member 51. In this case, the secondary delay element 1 / (Js ² The moment of inertia J of (+ Cs + K) corresponds to the moment of inertia of the entire steering system 14, the friction coefficient C corresponds to the friction coefficient between the steering shaft 53 and the support member 51, and the spring constant K corresponds to the spring constant of the spring 52.
[0023]
The reference steering unit 20 further includes a reference table 42 (first changing unit) for changing the spring constant value K to a large or small value according to the vehicle speed detected by the vehicle speed sensor 12, and a reference to the vehicle speed. , A reference table 41 (second changing means) for changing the friction coefficient value C to a large or small value, and a reference table 40 (third change) for changing the inertia moment value J to a large or small value according to the vehicle speed. Means), and a reference table 43 (fourth changing means) for changing the spring constant value K to a small or large value according to the magnitude of the steering angle detected by the steering angle sensor 10.
The reference steering unit 20 further includes a multiplying unit 44 that multiplies the outputs of the reference tables 42 and 43 and provides the output to the reference steering model 20a.
[0024]
The second control means 21 calculates a deviation of the steering angle (actual steering angle signal) detected by the steering angle sensor 10 from the reference steering angle θd output by the reference steering means 20, and outputs a subtraction point 23; An amplifier 24 for amplifying the deviation output by the point 23 with a gain G1, a differentiating means 25 for differentiating the steering angle detected by the steering angle sensor 10, and a steering angle (steering angular velocity) differentiated by the differentiating means 25 for a gain G2. , And a subtraction point 36 for subtracting the output of the amplifier 26 from the output of the amplifier 24 and outputting the second control signal. Other configurations have been described with reference to FIG. However, the first switching means 18 is omitted.
[0025]
The reference steering means 20 uses the steering torque whose phase delay has been compensated by the phase compensation means 22 for the secondary delay element 1 / (Js ² + Cs + K) to obtain the reference steering angle θd. The subtraction point 23 calculates a deviation of the steering angle detected by the steering angle sensor 10 from the reference steering angle θd obtained by the reference steering means 20, and the amplifier 24 amplifies the deviation by a gain G1.
On the other hand, the steering angle detected by the steering angle sensor 10 is differentiated by the differentiating means 25, and the differentiated steering angle (steering angular velocity) is amplified by the amplifier 26 with the gain G2.
The subtraction point 36 outputs the second control signal by subtracting the output of the amplifier 26 from the output of the amplifier 24.
[0026]
Hereinafter, an electric power steering apparatus having such a configuration will be described.
The first control means 17 outputs a first control signal based on the steering torque detected by the torque sensor 11 and the vehicle speed detected by the vehicle speed sensor 12.
The reference steering means 20 calculates and outputs the reference steering angle θd based on the steering torque, and the second control means 21 outputs the second control signal by the above-described operation.
The reference steering unit 20 also changes the friction coefficient value C of the reference steering model 20a according to the magnitude of the output of the reference table 41, and changes the friction coefficient value C of the reference steering model 20a according to the magnitude of the output of the reference table 40. The moment of inertia value J is changed to be large or small. Further, the spring constant value K of the reference steering model 20a is changed to be large or small according to the magnitude of the output of the multiplying means 44.
[0027]
Here, when the friction coefficient value C is increased, the convergence of the steering wheel (steering member) is accelerated. When the inertia moment value J is increased, the fit of the steering wheel is improved, and the straightness of the vehicle is improved. When the spring constant K is increased, the rigidity of the steering wheel is increased, and the vehicle is stabilized during high-speed running. Further, when the spring constant value K is reduced as the steering angle increases, the driver can easily recognize the middle point of the steering wheel, and the return of the steering wheel is improved.
[0028]
When the changeover switch 19 is operated, the first changeover means 18 switches to the first control means 17 side or the second control means 21 side, and outputs the first control signal or the second control signal.
The first switching unit 18 switches to the second control unit 21 and outputs the second control signal when an instruction signal is transmitted from the behavior determination unit 13 when the first switching unit 18 is switched to the first control unit 17 side. I will do it.
[0029]
After the first control signal or the second control signal is amplified by the amplifier 16, the first control signal or the second control signal is converted into a PI control signal by the PI controller 15 and supplied to the steering assist motor.
When the first switching unit 18 switches to the second control unit 21 and outputs the second control signal, the driver can perform steering with the steering torque and the reaction force determined according to the steering angle. In addition, the influence of unevenness of the road surface, frictional force, and the like is not transmitted to the steering member.
[0030]
FIG. 4 shows a case where the steering angular velocity obtained by differentiating the steering angle detected by the steering angle sensor 10 in the second control means 21 is subtracted from the second control signal (a) (gain G2 of amplifier 26 = 400). FIG. 7B is a characteristic diagram showing the phase and gain frequency characteristics of the steering system 14 when no subtraction is performed (b) (gain G2 = 0 of the amplifier 26). In the case of subtraction (a), it is shown that the vibration is suppressed.
[0031]
Embodiment 2 FIG.
FIG. 5 is a block diagram showing a main configuration of an electric power steering apparatus according to Embodiment 2 of the present invention. The electric power steering apparatus includes a torque sensor 11 for detecting a steering torque applied to a steering member (steering wheel and steering shaft) of a steering system 14, a steering assist motor M connected to the steering system 14, and a torque sensor. A first control means for outputting a first control signal for driving a steering assist motor based on a steering torque detected by the vehicle speed sensor and a vehicle speed detected by the vehicle speed sensor; A steering angle sensor 10 for detecting a steering angle.
[0032]
The electric power steering apparatus further includes a reference steering unit that calculates and outputs a reference steering angle based on a reference steering model 20b that defines a relationship between the steering angle detected by the steering angle sensor 10 and the steering torque detected by the torque sensor 11. 20c, a subtraction point 23 (calculation means) for calculating a deviation of the steering angle detected by the steering angle sensor 10 from the reference steering angle output by the reference steering means 20c, and a deviation output by the subtraction point 23 is calculated by a gain g1. An amplifier 31 for amplifying, a differentiating means 25 for differentiating the steering angle detected by the steering angle sensor 10, an amplifier 32 for amplifying the steering angle (steering angular velocity) differentiated by the differentiating means 25 with a gain g2, and an output of the amplifier 31 An output of the amplifier 32 is subtracted to create a second control signal, and an addition point 30 for adding the first control signal from the first control means 17 to the second control signal is added. Eteiru.
[0033]
The reference steering model 20b has, for example, three types of reference steering models 20a as described in the first embodiment, and the reference steering unit 20c responds to the vehicle speed detected by the vehicle speed sensor 12, for example, when the vehicle speed is high. Selects from three types of reference steering models so that the steering torque is relatively heavy. The reference steering unit 20c switches between three types of reference steering models by operating the manual changeover switch 35.
The reference steering unit 20c changes the reference steering model 20b according to the vehicle speed detected by the vehicle speed sensor 12 and the steering angle detected by the steering angle sensor 10.
[0034]
FIG. 6 is a block diagram showing the internal configuration of the reference steering means 20c. The reference steering means 20c has a built-in phase compensating means 22 for compensating for a phase delay of the steering torque. The reference steering model 20b includes a moment of inertia J of the steering member of the steering system 14, a coefficient of friction of the steering member with the support member. C and a second-order lag element 1 / (Js) consisting of a spring constant K when the steering member is regarded as a spring. ² + Cs + K), and is realized by software stored in a memory built in the reference steering unit 20c. (S is a complex variable)
[0035]
As shown in FIG. 3, the configuration of the steering member of the steering system 14 is such that a distal end of a steering shaft 53 that supports the steering wheel 50 is supported by a fixed portion via a spring 52, and an intermediate portion of the steering shaft 53 is supported. It can be shown schematically as supported by the member 51. In this case, the secondary delay element 1 / (Js ² The moment of inertia J of (+ Cs + K) corresponds to the moment of inertia of the entire steering system 14, the friction coefficient C corresponds to the friction coefficient between the steering shaft 53 and the support member 51, and the spring constant K corresponds to the spring constant of the spring 52.
[0036]
The reference steering unit 20c further includes a reference table 42a (first changing unit) that stores three types of relations for changing the spring constant value K between large and small according to the level of the vehicle speed detected by the vehicle speed sensor 12. And a reference table 41a (second changing means) for storing three types of relations for changing the friction coefficient value C according to the level of the vehicle speed. Further, a reference table 40a (third changing means) storing three types of relations for changing the inertia moment value J into large and small according to the level of the vehicle speed, and the magnitude of the steering angle detected by the steering angle sensor 10 And a reference table 43a (fourth changing means) for storing three types of relations for changing the spring constant value K to a small value or a large value according to.
[0037]
The three types of relationships stored in the reference tables 40a, 41a, 42a, and 43a are switched by a switching signal from the changeover switch 35 (FIG. 5), whereby the standard steering model 20b is changed to the three standard steering models. Switch to.
The reference steering unit 20c further includes a multiplying unit 44 that multiplies each output of the look-up tables 42a and 43a to give the output to the reference steering model 20b.
[0038]
This electric power steering apparatus also subtracts the deviation amplified by the amplifier 33 from the amplifier 33 that amplifies the deviation output from the subtraction point 23 (FIG. 5) with the gain g3 and the steering torque detected by the torque sensor 11, and subtracts the deviation. Subtraction point 28 for giving the obtained steering torque to the reference steering model 20b, gain variable means 34 for continuously changing the gains g1, g2, and g3, and the gain variable means 34 interlocked with the gain variable means 34 to vary the gain according to the slide position. The means 34 includes a slide switch 19a for continuously and smoothly changing the gains g1, g2, and g3.
[0039]
By changing the gains g1, g2, and g3, the gain varying means 34 can set the mixing ratio of the first control signal and the second control signal of the control signal output from the addition point 30. For example, when the mixture ratio is 100% first control signal, gain g1 = 0 and gain g3 = 500, and when the mixture ratio is 100% second control signal, gain g1 = 125000 and gain g3 = 0. In order to obtain an intermediate mixture ratio between them, the gains g1 and g3 are continuously changed in inverse proportion. The gain g2 is appropriately set according to the gains g1 and g3 so that vibration does not occur.
[0040]
The electric power steering device also determines whether or not the behavior of the vehicle is abnormal with a yaw rate sensor or the like. A behavior determining means 13 for switching the output of the motor M to the second control signal, an amplifier 16 for amplifying the control signal output from the addition point 30 in inverse proportion to the reduction ratio and the torque constant of the motor M, A PI controller 15 for providing a PI control signal to the motor M based on the signal.
[0041]
Hereinafter, an electric power steering apparatus having such a configuration will be described.
The first control means 17 outputs a first control signal based on the steering torque detected by the torque sensor 11 and the vehicle speed detected by the vehicle speed sensor 12, and provides the first control signal to the addition point 30.
The reference steering means 20c calculates and outputs a reference steering angle based on the steering torque obtained by subtracting the deviation amplified by the amplifier 33. The deviation of the steering angle detected by the steering angle sensor 10 from the reference steering angle is: The signal is amplified by the amplifier 31 with the gain g1 and given to the addition point 30.
[0042]
The reference steering unit 20c also changes the friction coefficient value C of the reference steering model 20b according to the magnitude of the output of the reference table 41a, and changes the friction coefficient value C of the reference steering model 20b according to the magnitude of the output of the reference table 40a. Change the moment of inertia J to a larger or smaller value. Further, according to the magnitude of the output of the multiplying means 44, the spring constant value K of the reference steering model 20b is changed to a magnitude.
[0043]
Here, when the friction coefficient value C is increased, the convergence to the middle point of the steering wheel (steering member) is accelerated. When the inertia moment value J is increased, the fit of the steering wheel is improved, and the straightness of the vehicle is improved. When the spring constant K is increased, the rigidity of the steering wheel is increased, and the vehicle is stabilized during high-speed running. Further, when the spring constant value K is reduced as the steering angle increases, the driver can easily recognize the middle point of the steering wheel, and the return of the steering wheel is improved.
[0044]
On the other hand, the steering angle detected by the steering angle sensor 10 is differentiated by the differentiating means 25, and the differentiated steering angle (steering angular velocity) is amplified by the amplifier 32 with a gain g2.
The summing point 30 creates a second control signal obtained by subtracting the output of the amplifier 32 from the output of the amplifier 31.
[0045]
The gain changing means 34 continuously and smoothly changes the gains g1, g2, and g3 according to the slide position of the slide switch 19a. As a result, the mixture ratio of the first control signal and the second control signal of the control signal output from the addition point 30 is set, and the driver can perform various steering operations between the first control means and the second control means. The driver can enjoy driving with the assisting steering torque.
Further, when the instruction signal is transmitted from the behavior determining means 13, the gain varying means 34 gradually changes the mixture ratio of the first control signal and the second control signal to 100% the second control signal.
[0046]
The control signal output from the addition point 30 is amplified by the amplifier 16 and then converted by the PI controller 15 into a PI control signal, which is provided to the steering assist motor.
When the control signal output from the addition point 30 is the 100% second control signal, the driver can perform steering with the steering torque and the reaction force determined according to the steering angle, and the steering member has The influence of unevenness of road surface, frictional force, etc. is not transmitted.
[0047]
FIG. 7 shows that the mixture ratio of the first control signal and the second control signal of the control signal output from the addition point 30 is changed from 100% first control signal (conventional control) to 100% second control signal (reference control). FIG. 9 is a waveform diagram showing a state in which the steering torque (operating the steering member periodically) changes when changed over 20 seconds. This shows that the control is switched from the conventional control to the reference control continuously and smoothly.
[0048]
【The invention's effect】
According to the electric power steering apparatus according to the first and second aspects of the present invention, an electric power steering apparatus capable of operating at a steering angle corresponding to a predetermined steering torque regardless of road surface conditions and obtaining a natural steering feeling is realized. You can do it.
[0049]
According to the electric power steering device according to the third aspect of the invention, an electric power steering device capable of operating at a steering angle with respect to a predetermined steering torque regardless of road surface conditions and obtaining an assist force according to a vehicle speed is realized. You can do it.
[0050]
According to the electric power steering apparatus according to the fourth aspect of the invention, it is possible to realize an electric power steering apparatus that can operate at a steering angle corresponding to a predetermined steering torque regardless of a road surface condition and has a stable steering feeling.
[0051]
According to the electric power steering device according to the fifth aspect of the invention, the electric power steering device can be operated at a steering angle corresponding to the determined steering torque irrespective of the road surface condition, and the vehicle can travel straight.
[0052]
According to the electric power steering device according to the sixth aspect of the present invention, it is possible to realize an electric power steering device that can operate at a steering angle with respect to a determined steering torque regardless of road surface conditions and has good steering wheel return.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a main configuration of an electric power steering apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram showing an internal configuration of a second control means and its related parts.
FIG. 3 is an explanatory diagram schematically showing a configuration of a steering member of a steering system.
FIG. 4 is a characteristic diagram illustrating frequency characteristics of a phase and a gain of a steering system when a steering angular velocity is subtracted from a second control signal (a) and when the steering angular velocity is not subtracted (b).
FIG. 5 is a block diagram showing a main configuration of an electric power steering apparatus according to an embodiment of the present invention.
FIG. 6 is a block diagram showing an internal configuration of a reference steering unit.
FIG. 7 is a waveform diagram showing how the steering torque changes when the mixture ratio of the first control signal and the second control signal is changed.
[Explanation of symbols]
10 Steering angle sensor
11 Torque sensor
12 Vehicle speed sensor
13 Behavior determination means
14 Steering system (steering member)
15 PI controller (output means)
16, 24, 26, 31, 32, 33 Amplifier
18 First switching means
19, 35 changeover switch
20, 20c Standard steering means
20a, 20b Reference steering model (memory means)
21 Second control means
23, 28, 36 Subtraction points (calculation means)
25 Differentiating means
30 addition points
34 Gain changing means
40, 40a lookup table (third change means)
41, 41a lookup table (second changing means)
42, 42a lookup table (first changing means)
43, 43a lookup table (fourth changing means)
44 Crossing means
50 Steering wheel (steering member)
M Motor for steering assist

Claims (6)

A torque sensor that detects a steering torque applied to a steering member, a steering angle sensor that detects a steering angle of the steering member, and a standard that defines a relationship between the steering torque and a standard steering angle that is a steering angle corresponding to the steering torque. A reference steering unit that outputs a reference steering angle based on the steering model, a reference steering angle output by the reference steering unit based on the steering torque detected by the torque sensor, and a steering angle difference detected by the steering angle sensor. Output means for outputting a control signal for driving a steering assist motor, in order to reduce
The reference steering model includes a second-order lag element consisting of a moment of inertia J of the steering member, a coefficient of friction C of the steering member with a support member, and a spring constant value K when the steering member is regarded as a spring. An electric power steering apparatus characterized in that 1 / (Js ² + Cs + K). (S is a complex variable) A motor for assisting steering, a torque sensor for detecting a steering torque applied to the steering member, a steering angle sensor for detecting a steering angle of the steering member, and a steering angle corresponding to the steering torque and the steering torque. A relation of a certain reference steering angle is determined, and the relation is defined by a moment of inertia J of the steering member, a coefficient of friction C of the steering member with a support member, and a spring constant value K when the steering member is regarded as a spring. Storage means for storing a reference steering model that is the next delay element 1 / (Js ² + Cs + K); reference steering means for calculating and outputting a reference steering angle based on the reference steering model stored in the storage means; Means for calculating a difference between a standard steering angle calculated and output based on the steering torque detected by the torque sensor and a steering angle detected by the steering angle sensor; and a difference calculated by the calculation means. In order to reduce the electric power steering device characterized by an output means for outputting a control signal for driving the motor. 3. The vehicle according to claim 1, further comprising a vehicle speed sensor that detects a vehicle speed of the vehicle, and a first changing unit that changes the spring constant value K according to a level of the vehicle speed detected by the vehicle speed sensor. 4. Electric power steering device. 4. The electric power steering apparatus according to claim 3, further comprising: a second changing unit that changes the friction coefficient value C according to a level of the vehicle speed detected by the vehicle speed sensor. 5. The electric power steering apparatus according to claim 3, further comprising a third changing unit that changes the inertia moment value J according to a level of the vehicle speed detected by the vehicle speed sensor. The electric power steering apparatus according to any one of claims 1 to 5, further comprising a fourth changing unit that changes the spring constant value K to a small value according to the magnitude of the steering angle detected by the steering angle sensor.

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