JP2803488B2 - Fuzzy control type electronic control power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronically controlled power steering apparatus for electronically controlling a steering assist amount in a steering mechanism of a vehicle, and more particularly, to a fuzzy control type electronic control in which a target assist amount is set by a fuzzy rule. It relates to a power steering device.

[0002]

2. Description of the Related Art In recent years, power steering devices have become widespread for assisting a force for operating a steering wheel (hereinafter, referred to as a steering wheel) (hereinafter, referred to as a steering wheel operating force or a steering force). As this power steering device, a hydraulic power steering device that assists steering by hydraulic pressure using a hydraulic cylinder mechanism is generally used. In addition, an electric power steering device that assists steering by an electric motor has been developed. ing.

[0003] With such a power steering device, even a vehicle requiring a large steering wheel operating force, such as a large vehicle or a vehicle using a wide tire for the steering wheel, can be steered with a small steering wheel operating force. The so-called handle weight is eliminated. By the way, in general, it is desired that the steering wheel can be operated more lightly at the time of low speed such as garage parking. In addition, during high-speed running, running becomes unstable if the steering wheel is too light. So, depending on the vehicle speed,
2. Description of the Related Art A vehicle speed-sensitive power steering apparatus has been developed in which the steering assist amount is increased at low speeds, and the steering assist amount is reduced as the vehicle speed increases at medium to high speeds.

As such a vehicle speed-sensitive power steering device, a vehicle is provided with a vehicle speed sensor, and a valve or the like capable of adjusting a hydraulic pressure supplied to the power steering is provided in a part of a hydraulic system of the hydraulic power steering device. There is one that electronically controls the operation of valves and the like based on a vehicle speed detected by a vehicle speed sensor and adjusts a steering assist amount (this is referred to as an electronic control power steering device).

[0005] For example, FIGS. 13 to 15 are configuration diagrams each showing an example of an electronic control power steering device. FIG. 13 is a diagram showing a longitudinal section of an input shaft portion and a pinion portion together with a hydraulic cylinder for power steering. FIG. 14 is a cross-sectional view of the input shaft portion, and is a cross-sectional view taken along the line AA of FIG. 13, and FIG. 15 is a configuration diagram showing a vertical cross-section of a hydraulic control valve arranged side by side with the input shaft together with a reaction force plunger. there, the hydraulic control valve portion is a B-B sectional view of FIG. 13, the reaction force plunger portion is a C-C sectional view of FIG. 14.

In FIGS. 13 to 15, an input shaft 11 receives a steering force from a steering wheel (handle) (not shown), and is rotatably mounted in a casing 25. A pinion gear 12 is provided at a lower end of the input shaft via a bush or the like (not shown). A torsion bar 15 is provided inside the input shaft 11.
Are coupled to each other via a pin or the like so that the lower end thereof is not restrained with respect to the input shaft 11.

The pinion gear 12 is serrated with the lower end of the torsion bar 15 so that the steering force input to the input shaft 11 is applied to the torsion bar 1.
5 is transmitted to the pinion gear 12. The pinion gear 12 meshes with a rack 13, and a steering force is transmitted to the rack 13 via the pinion gear 12 to drive the rack 13 in the axial direction to steer wheels.

Reference numeral 14 denotes a hydraulic cylinder for power steering (power steering).
A cylinder 14A installed on a member on the vehicle body side and a rack 1
3 and the cylinder unit 1 together with the rack 13
With a piston 14B that moves in the axial direction in 4A,
Inside the cylinder 14A, oil chambers 14C and 14D are formed by being partitioned left and right by the piston 14B.

Reference numeral 16 denotes a rotary valve for driving the hydraulic cylinder 14, and the left and right oil chambers 14C, 1 of the hydraulic cylinder 14 are opened and closed according to the opening and closing of the rotary valve 16.
Hydraulic oil is supplied or discharged to the 4D, and a steering assist force is applied to the rack 13. The rotary valve 16 is interposed between the input shaft 11 and the pinion gear 12, and opens and closes according to the phase difference between the input shaft 11 and the pinion gear 12. That is, the input shaft 1
When a steering force is input to the torsion bar 1, the input shaft 11 is rigid and hardly twists.
5 transmits the steering force to the pinion gear 12 while twisting, so that the pinion gear 12
A phase difference is generated on the steering side with respect to 1. The rotary valve 16 opens and closes so that a required steering assist force is generated in the steering direction according to the phase difference.

[0010] A reaction force plunger 17 is provided on the outer periphery of the lower portion of the input shaft 11 to increase the steering force (ie, steering response) by applying a steering reaction force during steering. As shown in FIG. 15 , a plurality of reaction force plungers 17 are provided so as to surround the outer periphery of the input shaft 11, and receive the hydraulic pressure supplied through the control of the hydraulic control valve 18 into the chamber 17A at the back thereof. Thus, the input shaft 11 is restrained in accordance with the hydraulic pressure to apply a steering reaction force. The chamber 17A communicates with the oil reservoir 24 via the return orifice 22.

As shown in FIG. 15 , the hydraulic control valve 18 is provided on the side of the input shaft 11 in the casing 25 in parallel with the input shaft 11, and has a plunger 18A which can slide up and down in the casing 25. It has a solenoid 19 for applying an axial force upward to the plunger 18A, and a spring 20 for urging the plunger 18A downward.

An oil reservoir 2 is provided in the plunger 18A.
4, an annular oil passage 18D that can communicate with the oil pump 23, an annular oil passage 18E that can communicate with the chamber 17A of the reaction force plunger 17, and these annular oil passages 18D and 18E communicate with each other. Oil passage 18F is provided. That is, the chamber 1 of the reaction force plunger 17
7A, the annular oil passage 18D to the oil passage 18F, the annular oil passage 1
High pressure hydraulic oil from the oil pump 23 can be supplied through 8E.

For example, the maximum current is applied to the solenoid 19 at the time of stationary steering or low-speed running steering. As a result, the plunger 18A rises most, and the annular oil passage 18D does not communicate with the oil pump 23,
Oil is no longer supplied to the chamber 17A of the reaction force plunger 17, and the reaction force plunger 17 does not restrain the input shaft 11, so that the steering can be performed lightly.

For example, when the vehicle is running at a medium to high speed, the current applied to the solenoid 19 is reduced in accordance with the increase in the vehicle speed. Then, when the handle is neutral, the plunger 18
The axial force of A decreases as the current decreases, and the plunger 18A descends, and the annular oil passage 18D communicates with the oil pump 23.
Is supplied to the chamber 17A.

In this state, the reaction force plunger 17 restrains the input shaft 11, so that the handle is held neutral. When the steering wheel is slightly steered in the neutral state, the output of the oil pump tends to increase. However, the discharge pressure is hardly controlled by the hydraulic control valve 18 and acts on the chamber 17A of the reaction force plunger 17. . Therefore, in the vicinity of the neutral state of the steering wheel, the steering force is increased, a neutral response of the steering wheel is sufficiently obtained, and the sense of stability of the steering wheel in the neutral state is increased.

When the vehicle is steered during high-speed running, the output of the oil pump is increased in accordance with the steering of the steering wheel (according to the increase in the steering force) within the normal steering range to increase the steering assist. Act like so. On the other hand, while the discharge pressure of the oil pump is controlled by the hydraulic control valve 18,
It acts on the chamber 17A of the reaction force plunger 17. Therefore, the reaction force plunger 17 acts to restrain the input shaft 11 and increase the steering response (steering force).

As a result, the steering force is increased by the amount of the reaction force plunger 17 at the time of middle- and high-speed running steering as compared with the stationary steering and low-speed running steering. That is, the steering response is increased, and a stable steering feeling is obtained. In particular, by decreasing the current applied to the solenoid 19 in accordance with the increase in the vehicle speed, the steering assist decreases as the speed increases, and the steering force (steering response) increases, resulting in a more stable steering feeling. Is obtained.

As described above, the steering assist characteristic can be controlled by adjusting the current applied to the solenoid 19. For example, as shown in FIG. 15 , in addition to the vehicle speed information from the vehicle speed sensor 31, EPS (electronic control power steering) The control unit (control means) 30 sets the amount of current to be applied to the solenoid 19 based on mode setting information from the mode changeover switch 32, an engine rotation signal from the engine speed sensor 33 and the like, and switches the solenoid 19 Controlling.

That is, the EPS mode changeover switch 32 can set a normal mode and a sports mode for performing control for increasing the steering force from a lower speed than the normal mode. When the control unit 30 sets these modes, The assist characteristics of the power steering are controlled according to the mode. For example, when set to the sports mode, as shown in FIG. 16, based on the vehicle speed information, in accordance with an increase in speed from speed range within the speed V ₁ as gradually as the assist characteristic as assist amount decreases , The current supplied to the solenoid 19 is adjusted. Moreover, when set to the normal mode, based on the vehicle speed information, as increasingly assist amount with increasing speed from a slightly high-speed range of the speed V ₂ (> V ₁₎ is assisted properties such as decreasing, the solenoid Adjust the current applied to 19.

An abnormality in the detection system or the like is detected based on the vehicle speed information and the engine rotation signal. At this time, fail-safe control is performed by turning off the solenoid 19 or the like.

[0021]

By the way, actually,
The required steering force characteristics differ depending on the running state of the vehicle, that is, whether the vehicle is accelerating or decelerating, for example. However, in the conventional electronically controlled power steering apparatus, as described above, since the control is simply performed in accordance with the vehicle speed, an optimum steering feeling has not always been obtained.

In particular, in the case of a front-wheel drive vehicle (FF vehicle),
During acceleration, there is a problem that the steering force (that is, steering response) is easily released due to a decrease in the front wheel contact load or the like. Further, at the time of braking, the steering force suddenly rises due to an increase in the front-wheel contact load, and the driver may feel uncomfortable. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a fuzzy control electronically controlled power steering device capable of obtaining optimum steering characteristics according to a running state of a vehicle.

[0023]

According to a first aspect of the present invention, there is provided a fuzzy control electronically controlled power steering apparatus according to the present invention, wherein an electronically controlled power steering apparatus for electronically controlling a steering assist amount in a vehicle steering mechanism is provided. A target assist amount setting means for setting a target assist amount at the time of control is provided. The target assist amount setting means uses a fuzzy rule as an input condition of the traveling speed of the vehicle, the acceleration / deceleration of the vehicle, and the steering angle of the vehicle. configured to set the target assist amount based, the
The fuzzy rule is applied in the area where the steering angle of the vehicle is small.
Is mainly based on the acceleration / deceleration of the vehicle.
As the target assist amount decreases with the increase,
In the region where the steering angle of the vehicle is large, the acceleration of the vehicle
With the increase, the target assist amount decreases and the vehicle
The target assist amount decreases as both decelerations increase
Set to not or only slightly decrease
It is characterized by:

[0024]

In addition to this, as described in claim 2 ,
It is desirable that the fuzzy rule is set such that the target assist amount decreases promptly with an increase in the acceleration of the vehicle.

[0026]

In the fuzzy controlled electronically controlled power steering apparatus according to the first aspect of the present invention, the target assist amount setting means uses the fuzzy control based on the running speed of the vehicle, the acceleration / deceleration of the vehicle, and the steering angle of the vehicle. A target assist amount is set based on a rule, and the steering assist amount of the steering mechanism of the vehicle is electronically controlled based on the target assist amount.

Further, the fuzzy rule is set such that the target assist amount decreases with an increase in the acceleration / deceleration mainly in accordance with the acceleration / deceleration of the vehicle in a region where the steering angle of the vehicle is small. In a large area, the target assist amount is set so as to decrease as the acceleration of the vehicle increases, and so that the target assist amount does not decrease so much as the deceleration of the vehicle increases.

Therefore, the target assist amount changes (decreases or increases) in accordance with the increase of the acceleration or the deceleration. However, in addition to the first and second aspects, a fuzzy rule is set. Then, the target assist amount rapidly decreases with an increase in acceleration.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will now be given, with reference to the drawings, of a fuzzy control type electronically controlled power steering apparatus according to an embodiment of the present invention. FIG. 1 is a schematic structural view of a main part thereof, and FIG. FIG. 3 is a diagram showing an example of a membership function used for the curved road fuzzy control, and FIG. 4 is a diagram showing an example of a table set for obtaining a power steering assist amount from each fitness level. FIG. 5 is a diagram showing a specific example of obtaining the respective fitness levels,
FIG. 6 is a diagram showing a specific example of a table set for obtaining the power steering assist amount from each degree of adaptation, FIG. 7 is a flowchart showing the control contents, FIG. 8 is a diagram showing the effect of the acceleration / deceleration fuzzy control, and FIG. FIG. 10 is a diagram showing an effect on steering linearity by the curving road fuzzy control, FIG. 10 is a diagram showing an effect on steering information by the curving road fuzzy control, and FIG. 11 is a diagram showing an effect on vehicle controllability by the curving road fuzzy control. FIG. 12 is a diagram showing the effect of the rudder effect by the curved road fuzzy control.

The mechanical part (hardware configuration) of the fuzzy control type electronically controlled power steering apparatus 1 is configured in substantially the same manner as that of the above-mentioned conventional example (see FIGS. 13 to 15), so that it will be briefly described. . 1 and 1
As shown in FIGS. 3 and 14, a torsion bar 15 is connected to the inside of the input shaft 11 such that an upper end thereof rotates integrally with the input shaft 11, and a lower end of the torsion bar 15 is restrained with respect to the input shaft 11. Not.

The pinion gear 12 is serrated with the lower end of the torsion bar 15 so that the steering force input to the input shaft 11 is applied to the torsion bar 1.
5 is transmitted to the pinion gear 12. The pinion gear 12 meshes with a rack 13, and a steering force is transmitted to the rack 13 via the pinion gear 12 to drive the rack 13 in the axial direction to steer wheels.

Hydraulic cylinder 1 provided on rack 13
4 includes a cylinder 14A provided on a member on the vehicle body side, and a piston 14B provided in the middle of the rack 13 and moving in the cylinder portion 14A in the axial direction together with the rack 13. The piston 14A is provided in the cylinder 14A. Oil chambers 14C and 14D are formed by being partitioned left and right by 14B.

Further, a rotary valve 16 is interposed between the input shaft 11 and the pinion gear 12, and the rotary valve 16 opens and closes according to the phase difference between the input shaft 11 and the pinion gear 12. Accordingly, the left and right oil chambers 14 of the hydraulic cylinder 14 are
Hydraulic oil is supplied or discharged to C and 14D, and a steering assist force is applied to the rack 13.

A reaction force plunger 17 is provided on the outer periphery of the lower portion of the input shaft 11 to increase the steering force (ie, steering response) by applying a steering reaction force during steering. A plurality of the reaction force plungers 17 are provided so as to surround the outer periphery of the input shaft 11, and the hydraulic pressure supplied through the control of the hydraulic pressure control valve 18 is received by the chamber 17A at the back thereof, and the reaction force plunger 17 is accordingly operated. The input shaft 11 is restrained to apply a steering reaction force. The chamber 17A communicates with the oil reservoir 24 via the return orifice 22.

The hydraulic control valve 18 is provided on the side of the input shaft 11 in the casing 25 in parallel with the input shaft 11, and has a plunger 18A which can slide up and down in the casing 25, and a plunger provided on the plunger 18A. A solenoid 19 for applying force and a spring 20 for urging the plunger 18A downward are provided. The plunger 18A has an oil passage 18 communicating with the oil reservoir 24.
B, 18C, and an annular oil passage 1 that can communicate with the oil pump 23
8D, an annular oil passage 18E that can communicate with the chamber 17A of the reaction force plunger 17, and these annular oil passages 18D and 18E.
And an oil passage 18F that communicates with each other. That is, high-pressure hydraulic oil from the oil pump 23 can be supplied to the chamber 17A of the reaction force plunger 17 from the annular oil passage 18D through the oil passage 18F and the annular oil passage 18E.

As shown in FIG. 1, the hydraulic control valve 18 is controlled by a control unit (control means) 30 based on vehicle speed information from a vehicle speed sensor 31 and steering angle information from a steering angle sensor 34. The amount of current applied to the solenoid 19 is set to control the solenoid 19.
That is, the control unit 30 includes a longitudinal acceleration calculator 30E, a lateral acceleration calculator 30A, and target assist amount setting means (fuzzy calculator) 30B for setting a target assist amount by fuzzy calculation. The unit 30 includes a longitudinal acceleration calculation unit 30E
In, based on the vehicle speed V, and calculates the longitudinal acceleration G _X occurring in the vehicle, the lateral acceleration calculation unit 30A, a vehicle speed V and the steering angle ha
, The lateral acceleration G _Y occurring in the vehicle is calculated, and the fuzzy arithmetic unit 30B performs fuzzy arithmetic from the longitudinal acceleration value G _X , the lateral acceleration G _Y , the vehicle speed V, and the steering angle ha. I have.

[0037] In particular, the fuzzy computation unit 30B includes deceleration control arithmetic unit 30b which performs fuzzy operation corresponding to the acceleration of the vehicle based on the longitudinal acceleration G _X occurring in the vehicle
When the lateral acceleration G _Y i.e. the crooked path running control computing section 3 for performing fuzzy operation corresponding to the winding road running state of a vehicle based on a turning state of the vehicle that occurs in the vehicle at a speed range suitable vehicle
0b '.

[0038] In deceleration control arithmetic unit 30b, and a longitudinal acceleration value G _X and vehicle speed V and the steering angle ha, and performs a fuzzy operation by the membership function shown in FIG. In addition, the curving road traveling control calculation unit 30b 'performs a fuzzy calculation based on the lateral acceleration value _GY and the vehicle speed V using a membership function as shown in FIG.

Then, as shown in the diagram of the table set in FIG. 4, the control amount (that is, the control amount (that is,
The amount of current to be applied to the solenoid 19 is controlled by determining the amount of decrease in assist. The membership function shown in FIG. 2 will now be described. Here, a straight traveling region where the steering angle ha is small, a turning region where the steering angle ha is not small (medium or higher) and a low speed region where the traveling speed of the vehicle is small, Angle ha is not small (medium or higher)
Different evaluations are made in a turning area where the running speed of the vehicle is not low (medium or higher) and in a medium-high speed area.

As shown in FIG. 4, the evaluation of the assist reduction control amount is performed for S (small), MS (medium small), M (medium), MB (medium big), and B (big). It is divided into five stages. In the evaluation S, the assist amount is 100%, and in the evaluation B, the assist amount is 0%. In other words, for the evaluation of the “straight-travel region (the steering angle ha is small)”, the degree of conformity is determined according to the steering angle ha, as in the relationship of the membership function on the left side of FIG. At this time, along with this, the fitness is determined according to the acceleration / deceleration of the vehicle, as in the relationship of the membership function on the right side of FIG.

Then, the smaller one of these two adaptations is adopted. When determining the degree of fitness, there is a method of employing the center of gravity (average value) of the two degrees of fitness, or a method of employing the sum of the degrees of fitness. In addition, the degree of conformity here is B which greatly reduces the target assist amount.
(Big).

Note that the membership function for evaluating straight traveling based on the steering angle ha is as shown in the left part of FIG.
Here, the degree of conformity is 1 when the steering angle ha is 0 to 5 deg, and linearly decreases from 1 to 0 when the steering angle ha is 5 to 15 deg. The membership function relating to the longitudinal acceleration value G _X, as shown in the right portion of FIG. 2 (A), during acceleration, to 1 from matching level 0 is between longitudinal acceleration value G _X is 0~0.3G The linearity increases, and the degree of conformity is 1 when the longitudinal acceleration value G _X is 0.3 G or more. Also, at the time of deceleration, the degree of conformity linearly increases from 0 to 1 when the longitudinal acceleration value G _X is between 0 and 0.7 G, and becomes 1 when the longitudinal acceleration value G _X is 0.7 G or more. . As described above, the degree of adaptation is set to increase relatively rapidly with acceleration during acceleration, and the degree of adaptation is set to increase more slowly with deceleration during deceleration than during acceleration.

The control for greatly reducing the target assist amount in the straight-ahead region with a low steering angle in this manner is more stable than straight-ahead steering (ie, lighter steering wheel). The reason why the target assist amount is greatly reduced in response to acceleration / deceleration is to increase the steering stability as the acceleration / deceleration becomes larger during straight running. . Further, the reason why the assist amount is promptly reduced during acceleration is to cope with the fact that the steering force is easily released during acceleration.

For the "turning area (steering angle ha is not small)", the degree of conformity is determined according to the steering angle ha, as in the relationship of the central membership function in FIG. 2B. At this time, if the vehicle speed is in the low speed region, the degree of conformity is determined according to the speed of the vehicle according to the relationship of the membership function on the left side of FIG. Based on the relationship between the membership functions, the degree of conformity is determined according to the acceleration / deceleration of the vehicle.

Then, the smaller one of these three degrees of fitness is adopted. In determining the degree of adaptation, there is also a method of adopting the center of gravity (average value) of three degrees of adaptation or employing the sum of the degrees of adaptation in correspondence with the case where the steering angle ha is small. The fitness here relates to B (big) that greatly reduces the target assist amount during acceleration. This relates to S (small) in which the target assist amount is not reduced during deceleration.

As shown in the center of FIG. 2B, the membership function for evaluating turning based on the steering angle ha has a degree of conformity of 0 to 0 when the steering angle ha is between 5 and 15 deg. Linearly increases to 1 and the steering angle ha becomes 15d
The degree of conformity is equal to or greater than eg. Also, the membership function that evaluates to low speed based on the vehicle speed V is shown in FIG.
Here, as shown on the left, the vehicle speed V is 0 to 20 km.
/ H, the conformity is 1, and the vehicle speed V is 20 to 40 km / h.
The fit decreases linearly from 1 to 0 between.

As shown in the right part of FIG. 2B, the membership function relating to the longitudinal acceleration value G _X is the same as when traveling straight, so that the degree of fitness increases relatively rapidly with acceleration during acceleration. Is set so that the degree of fitness increases more slowly with deceleration than during acceleration. As shown in the drawing, control is performed to greatly reduce the target assist amount when acceleration is involved during turning steering in a low speed range, for the same reason as in the case of straight traveling described above.

Further, control is performed so that the target assist amount is not reduced when deceleration is involved during turning steering in a low speed range, that is, a control that ensures a sufficient assist amount is performed. This is to cope with this because it tends to be heavy.
This is because the ease of steering (ie, the lightness of the steering wheel) is more important than the stability of the steering.

Furthermore, when the vehicle is in a turning area and the vehicle speed is in a medium to high speed area, the degree of conformity is obtained in accordance with the speed of the vehicle according to the relationship of the membership function on the left side of FIG. According to the relationship of the membership function on the right side of FIG. 2C, the degree of conformity is determined according to the acceleration / deceleration of the vehicle. Then, the smaller one of these three degrees of matching is adopted. In determining the degree of conformity,
Corresponding to each of the above cases, there is a method of employing the center of gravity (average value) of the three fitness levels, or employing the sum of the fitness levels.

Then, the degree of fitness here is that at the time of acceleration,
MB (medium big) that reduces the target assist amount
It is about. The present invention relates to an MS (medium small) that slightly reduces the target assist amount during deceleration. As shown in the left part of FIG. 2 (C), the membership function that evaluates to medium-to-high speed based on the vehicle speed V changes the degree of conformity from 0 to 1 when the vehicle speed V is between 20 and 40 km / h. It increases linearly, and the degree of conformity is 1 when the vehicle speed V is 40 km / h or more.

The membership function for evaluating turning based on the steering angle ha is the same as that at the time of low speed, as shown in the center of FIG. 2C. Further, membership functions for the longitudinal acceleration value G _X, as shown in the right portion of FIG. 2 (B), has become similar to the straight running, is set to fit with the acceleration is relatively rapid increase at the time of acceleration At the time of deceleration, the degree of conformity is set to increase more slowly with deceleration than at the time of acceleration.

As shown in the figure, control is performed to reduce the target assist amount when acceleration is involved during turning steering in the middle and high speed range, for the same reason as in the low speed range described above. Also, in this area, the degree of decrease is weaker than that of the evaluation B in the case of the low-speed area, which is evaluated as MB.
In the middle and high speed range, since the later-described curved road control is performed, the degree of decrease in the target assist amount is reduced.

Further, control is performed to slightly reduce (but not decrease) the target assist amount slightly when deceleration is involved in turning steering in the low speed region, for the same reason as in the low speed region described above. In this area, MS
Is evaluated and the assist amount is slightly reduced from the evaluation S in the case of the low speed region.
This is because the later-described curved road control is performed.

The curved road traveling control calculating section 30b 'includes a membership function for obtaining a fitness (grade) relating to the traveling state from the vehicle speed V as shown in FIG.
By using a membership function for determining the degree of conformity with respect to the lateral acceleration value G _Y as shown in (B), the degree of conformity of the running state and the degree of conformity of the lateral acceleration value G _Y are determined. Then, as shown in FIG. 4, a control amount (that is, an amount for reducing the assist) is determined from these degrees of conformity, and the amount of current applied to the solenoid 19 is controlled by the center of gravity method. It has become.

That is, the vehicle speed V as shown in FIG.
A membership function for obtaining a degree of fitness (grade) related to the driving state from the vehicle, and a lateral acceleration value G as shown in FIG.
By the membership function for obtaining the fitness about _Y, goodness of fit of the fit and lateral acceleration value G _Y of the running state. Then, as shown in FIG. 4, a control amount (that is, an amount for reducing the assist) is determined from these degrees of conformity, and the amount of current applied to the solenoid 19 is controlled by the center of gravity method. It has become.

In this example, a garage mode (stationary or low-speed running mode), a medium-speed running mode, a curved road running mode, and a high-speed running mode are set as running conditions. Determined according to vehicle speed. The assist reduction control amount corresponds to, for example, S for the garage parking mode (stationary or low-speed traveling mode), M for the medium-speed traveling mode, MB for the curved road traveling mode, and B for the high-speed traveling mode. Let it.

[0057] membership function relating to the lateral acceleration value G _Y, lateral acceleration value G _Y is in the region of the small (0G) (0.6
To the area of G) is the fitness in accordance with the increase in the lateral acceleration value G _Y increases linearly, the lateral acceleration value G _Y is medium (0.6
From the area of G) to the region of the large (0.8G) is fit is constant regardless of the increase in the lateral acceleration value G _Y, the lateral acceleration value G _Y is a region of a large (more than 0.8G), the horizontal Acceleration value G _Y
Is set so that the degree of conformity decreases as the value of .gamma. Increases.

The control relating to the lateral acceleration value G _Y reduces the assist amount to B (big) in accordance with the degree of conformity. And, in this manner, and adaptability for the fit of the lateral acceleration value G _Y about running mode determined in the crooked path running control computing section 30b ', and fit found by acceleration and deceleration control calculation unit 30b Therefore, the target assist amount is obtained by the center of gravity method.

Since the fuzzy control type electronically controlled power steering apparatus according to one embodiment of the present invention is configured as described above, the electronic control of the power steering is performed as shown in FIG. 7, for example. That is, first,
Reads the sensor signals from the vehicle speed sensor 31 and the steering angle sensor 34 (step S1), enter these sensor signals to the control unit 30, and conversion processing an analog signal into a digital signal, the lateral acceleration calculation unit 30A,
Based on the vehicle speed V and the steering angle ha, it calculates the lateral acceleration G _Y generated in the vehicle (step S2).

Further, the longitudinal acceleration value G is calculated by the fuzzy operation unit 30B by a membership function as shown in FIG.
Obtains the fitness of each control amount regarding acceleration and deceleration from the _X and vehicle speed V and the steering angle ha, obtains the goodness of fit about the traveling state from the vehicle speed V, the goodness of fit about the lateral acceleration G _Y of the lateral acceleration G _Y (step S3 ). Then, a target assist amount is determined by the center of gravity method from these degrees of matching (step S4). Further, the target assist amount is converted into a current amount to be applied to the corresponding solenoid 19 (step S5), and is output to the drive circuit, that is, the solenoid 19 of the hydraulic control valve 18 (step S6).

As a result, in the acceleration / deceleration fuzzy control of the present apparatus, the stability of steering is ensured during straight running, and the stability of steering is increased as the acceleration / deceleration increases. Furthermore, during acceleration, the assist amount decreases quickly,
In particular, in the case of a front-wheel drive vehicle (FF vehicle) or the like, there is an effect that the steering force is prevented from coming off. Also, during turning steering, the greater the acceleration, the higher the steering stability. Conversely, the greater the deceleration, the more the weight of the steering wheel is eliminated, and the easier the steering (ie, the lighter the steering wheel) is. Also,
As in the case of straight running, also during turning steering, when accelerating, the assist amount is quickly reduced, so that there is an effect of preventing the steering force from being lost.

The improvement of the steering feeling when the acceleration / deceleration fuzzy control of the present apparatus is applied to a front-wheel drive vehicle (FF vehicle) is specifically evaluated based on experiments as follows. FIG. 8 is a diagram showing a control effect in the case of turning acceleration / deceleration. The case where acceleration / deceleration fuzzy control is performed is shown by a solid line, and the case of speed-based control without acceleration / deceleration fuzzy control is shown by a broken line.

That is, when a constant steering angle Ha is maintained as shown in FIG. 8A and acceleration and deceleration are performed so as to generate longitudinal acceleration as shown in FIG. of (C), the steering assist amount when not performed deceleration fuzzy control is decreased so as to correspond to the increase vehicle speed at the time of acceleration (see time t ₁ ~t _2), at high speed substantially maintain the reduced state when the constant speed running (see time t ₂ ~t _3). However, actually, there is a time lag in the assist, so that the speed slightly decreases even at a constant speed at a high speed. further,
During deceleration (see time t ₃ ~t ₄₎ is increased so as to correspond to the decrease vehicle speed, substantially maintain the increased state when constant speed running at a low speed (see time t ₄ later). Also in this case, actually, even when the vehicle runs at a constant speed at a low constant speed where there is a time lag in the assist, the speed slightly increases.

On the other hand, when the acceleration / deceleration fuzzy control is performed, the steering assist amount is determined during acceleration (time t _{1 to} t _2).
) To correspond to an increase in vehicle speed, but this decrease is greater than without control. And, although slightly reduced at the time of constant speed driving at high speed (see time t ₂ ~t _3),
This reduction is also greater than without control. Furthermore, although increased to correspond to the decrease vehicle speed during deceleration (see time t ₃ ~t _4), larger than the absence of this increase is also controlled.
Then, although slightly increased during constant speed running at a constant speed (see time t ₄ later), greater than the absence of this increase is also controlled.

As a result, as shown in FIG. 8 (D), the steering force characteristic eliminates the loss of the steering force during acceleration.
It can be seen that the sudden increase in the steering force at the time of deceleration is also eliminated, and the steering force is made uniform to flat characteristics. In addition, a specific example related to the curved road fuzzy control will be described.
Consider a situation in which the vehicle starts turning with a vehicle speed V of 50 km / h and a lateral acceleration of about 0.4 G from a state of straight traveling at km / h (lateral acceleration is 0). This situation, on a curved road,
This is equivalent to entering a corner while decelerating.

When the vehicle speed V is 60 km / h, the degree of suitability for traveling on a curved road is 1, but when the vehicle speed V becomes 50 km / h, the degree of conformity for traveling on a curved road is 0.5 and the degree of conformity for traveling in an urban area is 0.5. 0.5. For running on a curved road, the assist reduction control amount is MB.
The assist reduction control amount is M. And the lateral acceleration is 0
When the lateral acceleration is 0.4, the fitness is 0.67.

Accordingly, when the vehicle speed V is 60 km / h and the lateral acceleration is 0, the vehicle speed V is 50 km / h and the lateral acceleration is 0 (MB = 25%) as shown by P1 in FIG. .6, as shown by P2 in FIG.
Shift to the B side. In other words, when you are entering the corner in spite of decelerating is the handle of is slightly heavy.

Of course, when the vehicle enters a corner while accelerating, the assist decreases due to the increase in the lateral acceleration is superimposed on the assist decrease in accordance with the acceleration, so that the steering wheel becomes heavy. As described above, since the assist amount is controlled in accordance with the lateral acceleration value G _Y in addition to the increase and decrease of the vehicle speed,
When approaching a corner, the steering angle increases, so the degree of decrease in assist increases, and the steering wheel becomes heavier by this amount. Therefore, even when the vehicle speed is different, when entering the corner, the driver can always steer while feeling the approach to the corner with the steering wheel.

[0069] Further, the membership function relating to the lateral acceleration value G _Y, since the steering linearity region fit the lateral acceleration value G _Y varies linearly is provided, the steering linearity is ensured. Then, the lateral acceleration value G _Y
In large areas, since steering limit in formation regions matching level decreases according to increase of the lateral acceleration value G _Y is provided, it becomes easy to recognize the steering limit.

The improvement of the steering feeling in the case where such a curved road fuzzy control of the present apparatus is employed in a front-wheel drive vehicle (FF vehicle) is specifically evaluated from various viewpoints based on experiments. Become like First, the steering linearity characteristics are as shown in FIG. 9, in which the horizontal axis indicates the front wheel slip angle and the vertical axis indicates the steering force. The solid line shows the characteristics of this device by the curved road fuzzy control, and the broken line shows the characteristics of the conventional electronically controlled power steering device.

As shown by the solid line in FIG. 9, according to the curving road fuzzy control of the present apparatus, up to a region where the front wheel slip angle is larger than that of the conventional example, and thus to a region where the lateral acceleration generated in the vehicle is large. Thus, relatively linear steering characteristics can be obtained over a wide area. This is obtained corresponding to the steering linearity region in the membership function relating to the lateral acceleration value G _Y.

Further, in the vicinity of the neutral position of the steering, the inclination is slightly steeper than that of the conventional steering wheel, and the steering reaction force in this region increases, so that the steering neutral feeling is improved and the steering wheel return is improved. In the device in which the control characteristic of the assist amount is changed, the linearity characteristic as shown by a chain line in FIG. 10 is obtained, and the neutral feeling is enhanced. However, in a region where the slip angle is large, the change of the steering force with respect to the slip angle is abrupt. Become smaller,
Linearity is reduced.

[0073] Incidentally, as shown in solid line in FIG. 9, a steering force its limit has suddenly changed at the time, the effect of the steering limit in formation regions in the membership function relating to the lateral acceleration value G _Y has appeared. Further, the characteristics of the steering information are as shown in FIG.
In FIG. 10, the horizontal axis represents the front wheel slip angle, and the vertical axis represents the steering force. In addition, △ indicates the characteristics of this device by the curved road fuzzy control, 〇 indicates the characteristics of the conventional electronically controlled power steering device, and the solid line indicates the speed (10
0 km / h), and the dashed line indicates a middle speed (60 km / h).
h).

As shown in FIG. 10, the conventional electronically controlled power steering apparatus has an advantage that it is easy to handle because the steering force is generally small, but it has an advantage in a region where the front wheel slip angle is large, that is, the lateral force generated in the vehicle. In a region where the acceleration is large, the change in the steering force is small, so that the steering information is not sufficient. In addition, the steering force is lost in the region where the lateral acceleration is large.

In the case of this device, since the steering force clearly changes over the region where the lateral acceleration is large, there is sufficient steering information, and the steering wheel is relatively light even in a low speed range, making it easy to handle. Has become. As described above, in the present device, it is possible to achieve a good balance between handleability in a low-speed range and steering information (change in steering force).

The characteristics of the controllability of the vehicle are as follows:
As shown in FIG. In FIG. 11, the horizontal axis indicates the yaw angular velocity of the vehicle, and the vertical axis indicates the steering force.
The solid line shows the characteristics of this device by the curved road fuzzy control, and the chain line shows the characteristics of the conventional electronically controlled power steering device. As shown in FIG. 11, in the case of the conventional electronically controlled power steering apparatus, in a region where the yaw angular velocity is large, the steering force does not appear as a change in the steering force even if the yaw angular velocity changes, and the turning performance of the vehicle is regarded as the steering force. Hard to detect. However, according to the curving road fuzzy control of the present apparatus, the steering force rises substantially linearly with respect to the yaw angular velocity up to the region where the yaw angular velocity is large, so that the turning performance of the vehicle can be realized as the steering force. Thereby, the controllability of the vehicle such as the traceability and the maneuverability of the vehicle is improved.

Further, the characteristics of the effectiveness of the rudder are as shown in FIG. In FIG. 12, the horizontal axis represents the front cornering force of the vehicle, and the vertical axis represents the steering force. The solid line shows the characteristics of this device by the curved road fuzzy control, and the broken line shows the characteristics of the conventional electronically controlled power steering device. As shown in FIG. 12, according to the curved road fuzzy control of the present device, the steering force rises linearly with respect to the cornering force (the effect of the rudder),
The rudder can be easily determined, and it is possible to reduce the number of turning of the steering wheel and the returning steering.

As described above, since the steering force rises substantially linearly with respect to the yaw angular velocity, the turning performance of the vehicle can be realized as the steering force. Thereby, the controllability of the vehicle such as the traceability and the maneuverability of the vehicle is improved. In this way, in the present device, the steering force characteristic is largely improved mainly on traveling on a curved road by applying the fuzzy control.

Naturally, the specific characteristic value of each membership function can be changed while maintaining the characteristics of each fuzzy rule described above. Further, in the fuzzy control type electronically controlled power steering apparatus of the present embodiment, the control configuration is such that the curved road fuzzy control is added to the acceleration / deceleration fuzzy control. However, other fuzzy control rules may be added to these controls. Alternatively, only the acceleration / deceleration fuzzy control may be performed to omit the curved road fuzzy control, or another fuzzy control law may be added to the acceleration / deceleration fuzzy control.

Further, the control system of the present apparatus can be applied not only to a hydraulic power steering apparatus but also to an electric power steering apparatus.

[0081]

As described above in detail, according to the fuzzy control type electronically controlled power steering apparatus of the present invention, there is provided an electronically controlled power steering apparatus for electronically controlling a steering assist amount in a vehicle steering mechanism. A target assist amount setting means for setting a target assist amount at the time of electronic control, wherein the target assist amount setting means uses a fuzzy speed as a condition for inputting a running speed of the vehicle, an acceleration / deceleration of the vehicle, and a steering angle of the vehicle. configured to set the target assist amount is based on rules, upper
The fuzzy rule is applied in the area where the steering angle of the vehicle is small.
Is mainly based on the acceleration / deceleration of the vehicle.
As the target assist amount decreases with the increase,
In the region where the steering angle of the vehicle is large, the acceleration of the vehicle
With the increase, the target assist amount decreases and the vehicle
The target assist amount decreases as both decelerations increase
Set to not or only slightly decrease
Therefore, when the vehicle accelerates or decelerates, the steering stability and ease of handling
, The steering force characteristics are balanced, so that the optimum steering characteristics can be obtained according to the acceleration / deceleration state of the vehicle, and this has the effect of contributing to an improvement in the steering feeling .

[0082]

In addition, as described in claim 2 ,
The fuzzy rules, as the target assist amount decreases rapidly with respect to the increase in the acceleration of the vehicle, by being set, in addition to the effect of the above mentioned, omission-prone steering force at the time of acceleration (steering The effect of avoiding too much force) can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of a fuzzy control electronically controlled power steering apparatus as one embodiment of the present invention.

FIG. 2 is a diagram showing an example of a membership function used for fuzzy control of a fuzzy control type electronically controlled power steering apparatus as one embodiment of the present invention.

FIG. 3 is a diagram showing an example of a table set for obtaining a power steering assist amount from each degree of fitness in fuzzy control of a fuzzy control type electronically controlled power steering apparatus as one embodiment of the present invention.

FIG. 4 is a diagram showing an example of a table set for obtaining a power steering assist amount from each degree of fitness in fuzzy control of a fuzzy control electronically controlled power steering apparatus as one embodiment of the present invention.

FIG. 5 is a diagram showing a specific example of obtaining respective fitness levels in fuzzy control of a fuzzy control electronically controlled power steering apparatus as one embodiment of the present invention.

FIG. 6 is a diagram showing a specific example of a table set for obtaining a power steering assist amount from each fitness level in fuzzy control of a fuzzy control electronically controlled power steering apparatus as one embodiment of the present invention.

FIG. 7 is a flowchart showing control contents of a fuzzy control type electronically controlled power steering apparatus as one embodiment of the present invention.

FIG. 8 is a diagram showing an effect of the fuzzy control type electronically controlled power steering apparatus as one embodiment of the present invention relating to acceleration / deceleration fuzzy control.

FIG. 9 is a diagram showing an effect on steering linearity by fuzzy control on a curved road in a fuzzy control electronically controlled power steering apparatus as one embodiment of the present invention.

FIG. 10 is a diagram illustrating an effect related to steering information by a fuzzy control on a curved road in a fuzzy control electronically controlled power steering apparatus as one embodiment of the present invention.

FIG. 11 is a diagram showing an effect on vehicle controllability by a fuzzy control on a curved road in a fuzzy control type electronically controlled power steering apparatus as one embodiment of the present invention.

FIG. 12 is a diagram showing an effect related to a rudder effect by a fuzzy control on a curved road in a fuzzy control electronically controlled power steering apparatus as one embodiment of the present invention.

FIG. 13 is a diagram showing a longitudinal section of an input shaft portion and a pinion portion of a conventional electronically controlled power steering device together with a hydraulic cylinder for power steering.

FIG. 14 is a cross-sectional view of an input shaft portion in a conventional electronically controlled power steering device, and FIG.
FIG. 3 is a sectional view taken along line AA of FIG.

FIG. 15 is a configuration diagram showing a longitudinal section of a hydraulic control valve arranged in parallel with an input shaft in a conventional electronically controlled power steering device together with a reaction force plunger;
The hydraulic control valve portion is a sectional view taken along line BB of FIG. 13, and the reaction force plunger portion is a sectional view taken along line CC of FIG.

FIG. 16 is a diagram showing characteristics of an assist amount in a conventional electronically controlled power steering device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuzzy control type electronic control power steering device 11 Input shaft 12 Pinion gear 13 Rack 14 Hydraulic cylinder 14A Cylinder 14B Piston 14C, 14D Oil chamber 15 Torsion bar 16 Rotary valve 17 Reaction force plunger 17A Chamber 18 Hydraulic control valve 18A Plunger 18B, 18C oil Road 18D, 18E Annular oil path 18F Oil path 19 Solenoid 20 Spring 22 Return orifice 22 24 Oil reservoir 25 Casing 30 Control unit (control means) 30A Lateral acceleration calculating section 30B Target assist amount setting means (fuzzy calculating section) 30b Acceleration / deceleration Control operation unit 30b 'Curved road traveling control operation unit 30E Longitudinal acceleration operation unit 31 Vehicle speed sensor 34 Steering angle sensor

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI B62D 125: 00 (56) References JP-A-4-43168 (JP, A) JP-A-3-90478 (JP, A) ( 58) Field surveyed (Int.Cl. ⁶ , DB name) B62D 6/00

Claims (2)

(57) [Claims] 1. An electronically controlled power steering device for electronically controlling a steering assist amount in a steering mechanism of a vehicle, comprising: target assist amount setting means for setting a target assist amount at the time of electronic control; configured to set the target assist amount based on fuzzy rules and steering angle of the acceleration and the vehicle running speed and the vehicle of the vehicle as an input condition, the fuzzy rules, the steering angle of the vehicle In small areas, mainly the vehicles
In accordance with the acceleration / deceleration of
In a region where the steering angle of the vehicle is large, the acceleration of the vehicle is reduced so that the assist amount decreases.
The target assist amount decreases with the increase of
As the vehicle deceleration increases, the target assist amount decreases.
Set to have little or no decrease
Characterized in that that, fuzzy control electronically controlled power steering apparatus. Wherein said fuzzy rules, so the target assist amount decreases rapidly with respect to the increase in the acceleration of the vehicle, characterized in that it is set, the fuzzy control electronic of claim 1 Control power steering device.