JP2985580B2 - Electronically controlled 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 for example, to set a target assist amount by a fuzzy rule.

[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] By using such a power steering device, even a vehicle that requires a large steering wheel operating force, such as a large vehicle or a vehicle having wide tires mounted on steering wheels, can be operated with a small steering wheel operating force. Steering can be performed, so-called steering wheel weight is eliminated. By the way, in general, it is desired that the steering wheel be made lighter at a low speed such as in a garage so that the vehicle can be operated lightly. On the other hand, if the steering wheel is too light when traveling at high speed, traveling becomes unstable, so we want to make it possible to operate stably by increasing the weight. Therefore, a vehicle speed-sensitive power steering device has been developed in which the steering assist amount is increased at low speeds according to the vehicle speed, and reduced as the vehicle speed becomes high at medium and high speeds.

In such a vehicle speed-sensitive power steering device, a vehicle speed sensor is provided in a vehicle, and a valve or the like capable of adjusting a hydraulic pressure supplied to power steering is provided in a part of a hydraulic system of a hydraulic power steering device. There is a type in which the steering assist amount is adjusted while electronically controlling the operation of a valve or the like based on a vehicle speed detected by a vehicle speed sensor (this is referred to as an electronically controlled power steering device).

FIG. 10 shows a schematic configuration of a hydraulic power control unit for power steering which represents an example of a conventional electronically controlled power steering device. FIG. 11 shows a cross section taken along line XI-XI of FIG. 10 and FIG. Show.

As shown in FIGS. 10 to 12, an input shaft 11 receives a steering force from a steering wheel (handle) (not shown), and is rotatably supported in a casing 12 by a bearing. A pinion gear 13 is rotatably mounted on a lower end of the input shaft 11 via a bush or the like (not shown).
A torsion bar 14 is provided in the hollow portion of the input shaft 11.
The upper end is connected to the input shaft 11 by a pin so as to be integrally rotatable, while the lower end is free without being restrained with respect to the input shaft 11.

[0007] The pinion gear 13 at the lower end of the input shaft 11 is serrated with the lower end of the torsion bar 14 so that the steering force input to the input shaft 11 is transmitted to the pinion gear 13 via the torsion bar 14. I have. The pinion gear 13 meshes with a rack 15, and the steering force of the input shaft 11 is transmitted to the rack 15 via the pinion gear 13, and the rack 15 is driven in an axial direction (a direction orthogonal to the paper surface of FIG. 10) to thereby provide a wheel (not shown). Can be steered.

In the casing 12, a rotary valve 16 is interposed between the input shaft 11 side and the pinion gear 13 side.
Are opened and closed according to a circumferential phase difference between the input shaft 11 and the pinion gear 13. The rotary valve 16 has a hydraulic oil supply pipe 18 of an oil pump 17 provided outside and an oil reservoir 1.
Nine hydraulic oil discharge pipes 20 are connected. On the other hand, 21 is a hydraulic cylinder for power steering. The hydraulic cylinder 21 is configured such that a piston 23 is supported in a hollow cylinder 22 installed on a predetermined member on the vehicle body side so as to be movable in the axial direction. The piston shaft 24 is fixed in the middle of the rack 15 described above. The piston 23 partitions the inside of the cylinder 22 left and right, and the oil chamber 2
5, 26 are formed.

Accordingly, when a steering force is input to the input shaft 11, the input shaft 11 is rigid and hardly twists, but the torsion bar 14 transmits the steering force to the pinion gear 13 while twisting. . Then, the pinion gear 13 is connected to the input shaft 11.
, A phase difference is generated on the steering side, and the rotary valve 16 is driven according to the phase difference. The oil pump 17 is operated according to the opening and closing of the rotary valve 16.
Is supplied to the left and right oil chambers 25 and 26 of the hydraulic cylinder 22 through the hydraulic oil supply pipe 18, so that the steering assist force is given to the rack 15, and the required steering assist force in the steering direction is provided. Is to occur.

In the casing 12, a reaction plunger 27 is provided on the outer periphery of the lower portion of the input shaft 11 to increase the steering force (steering response) by applying a steering reaction force during steering. A plurality of the reaction force plungers 27 are provided so as to surround the outer periphery of the input shaft 11, receive the hydraulic pressure supplied through the control of the hydraulic control valve 28, restrain the input shaft 11 according to the hydraulic pressure, and perform steering. It gives a reaction force.

That is, four reaction force plungers 27 are provided at equal intervals in the casing 12 so as to surround the outer periphery of the input shaft 11, and a chamber 29 is formed on the outer end side thereof, and the return orifice 30 Is provided. On the other hand, the hydraulic control valve 18 is provided adjacent to and parallel to the side of the input shaft 11 in the casing 12. In this hydraulic control valve 28, a spool 31 is provided in the casing 12.
The spool 31 is movably provided up and down, and the spool 31 is biased and supported downward by a spring 32 provided at an upper portion. Further, a solenoid 33 is provided on a lower outer peripheral piece of the spool 31, and an upward axial force is applied to the spool 31 by exciting the solenoid 33.

The spool 31 has an oil reservoir 19.
Oil passages 34 and 35 communicating with the hydraulic oil discharge pipe 20 and an annular oil passage 36 communicating with the hydraulic oil supply pipe 18 of the oil pump 17 are formed, and the chamber 2 of the reaction force plunger 27 is formed.
An annular oil passage 38 that communicates with the hydraulic oil supply line 9 via a hydraulic oil supply / discharge pipe 37 and an oil passage 39 that interconnects the annular oil passages 36 and 38 are formed. Therefore, normally, in the demagnetized state of the solenoid 33, the spool 31 is in the lowered position and the hydraulic oil supply pipe 18
And the annular oil passage 36 communicate with each other. Therefore, the hydraulic oil supplied from the oil pump 17 to the hydraulic control valve 28 via the hydraulic oil supply pipe 18 flows from the annular oil passage 36 to the oil passage 3.
9, is supplied to the chamber 29 of the reaction plunger 27 through the annular oil passage 38. On the other hand, when the solenoid 33 is in the excited state, the spool 31 is at the raised position, and the hydraulic oil supply pipe 18 and the annular oil passage 36 are not in communication. Therefore, the oil supply pipe 18
Is not supplied to the chamber 29 of the reaction force plunger 27.

By adjusting the current supplied to the solenoid 33, the steering assist characteristic can be controlled. A control unit (CU) 40 for controlling the solenoid 33 is connected to a vehicle speed sensor 41, an engine speed sensor 42, and the like. The control unit 40 supplies a current to the solenoid 33 based on output signals from these units. The amount can be set to control the solenoid 33.

For example, the maximum current is applied to the solenoid 33 when the vehicle is stationary or when the vehicle is steered at a low speed. As a result, the spool 31 rises to the maximum and the annular oil passage 36 does not communicate with the hydraulic oil supply pipe 18 of the oil pump 17, so that oil is not supplied to the chamber 29 of the reaction force plunger 27. Therefore, the input shaft 11 is not restrained by the reaction force plunger 27, and the steering wheel can be steered lightly.

For example, when the vehicle is running at a high speed, the current applied to the solenoid 33 is reduced in accordance with the increase in the vehicle speed. Then, when the handle is in the neutral position, the axial force of the spool 31 decreases due to the current phenomenon, whereby the spool 31 descends and the annular oil passage 36 is connected to the oil pump 1.
7 and communicate with the hydraulic oil supply pipe 18, so that oil is supplied to the chamber 29 of the reaction force plunger 27. Therefore, the input shaft 11 is restrained by the reaction force plunger 27, and the handle is held neutral. When the steering wheel is slightly steered in the neutral state, the output of the oil pump 17 tends to increase, but this discharge pressure acts on the chamber 29 of the reaction force plunger 27 without being controlled by the hydraulic control valve 28. . Therefore, in the vicinity of the neutral state of the steering wheel, the steering force is increased, and a neutral response to the steering wheel can be sufficiently obtained, and the sense of stability of the steering wheel in the neutral state is increased.

When the vehicle is steered during middle-high speed running, the output of the oil pump 17 increases in accordance with the steering of the steering wheel (in accordance with the increase in the steering force) within the normal steering range, thereby increasing the steering assist. Act like so. On the other hand, the discharge pressure of the oil pump 17 acts on the chamber 29 of the reaction force plunger 27 while being controlled by the hydraulic control valve 28.
Therefore, the input shaft 11 is restrained by the reaction force plunger 27, and the steering response (steering force) can be increased.

As a result, the steering force is increased by the amount of the reaction force plunger 27 during the middle and high speed running steering as compared with the stationary or low speed running steering. That is, the steering response is increased, and a stable steering feeling is obtained. In particular, since the current applied to the solenoid 33 is reduced in accordance with the increase in the vehicle speed, the steering assist decreases and the steering force (steering response) increases as the vehicle speed increases, so that a more stable steering feeling can be obtained. it can.

A control unit 40 for controlling the solenoid 33 is connected to a vehicle speed sensor 41 and an engine speed sensor 42. The control unit 40 detects an abnormality in a detection system or the like from the vehicle speed signal and the engine speed signal.
The fail-safe control can be performed by turning off the switch.

[0019]

By the way, in the power steering apparatus, actually, the running state of the vehicle, that is, whether the vehicle is running straight or turning, and whether the vehicle is accelerating or braking. The required steering force characteristics are different depending on factors such as. However, in the conventional electronically controlled power steering apparatus described above, the steering assist amount is simply controlled in accordance with the vehicle speed, so that an optimum steering feeling cannot always be obtained.

For example, when the running vehicle decelerates, the steering force increases due to an increase in the front-wheel contact load. Therefore, the driver desires a steering force with a certain weight so that the vehicle at this time can be properly grasped. However, in the conventional electronically controlled power steering apparatus, the vehicle speed decreases due to the deceleration, so that the steering assist amount of the steering wheel increases and the steering force characteristics are reduced. Furthermore, when the vehicle enters a corner at a low speed while decelerating, there is a problem that the steering force (steering response) is lost due to a decrease in the steering force, and the user feels uncomfortable.

In addition to the electronically controlled power steering device described above, a power steering device that changes the assist amount according to a fuzzy rule based on a steering direction signal of a steering wheel and a signal of a vehicle height value is disclosed in Japanese Patent Laid-Open Publication No. Hei. 171384. Also,
Japanese Patent Application Laid-Open No. 2-171385 discloses a power steering device that changes an assist amount based on a signal of a steering direction of a steering wheel and a signal of a temperature in a vehicle according to a fuzzy rule.

However, even with these power steering devices, as described above, the steering assist amount of the steering wheel cannot be controlled so that the traveling state of the vehicle at the time of deceleration can be properly grasped. There is a problem that a good steering feeling cannot be obtained.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide an electronically controlled power steering apparatus capable of obtaining optimum steering characteristics according to a running state of a vehicle.

[0024]

According to the present invention, there is provided an electronically controlled power steering apparatus for electronically controlling a steering assist amount in a steering mechanism of a vehicle. Vehicle speed detecting means for detecting the running speed, longitudinal acceleration detecting means for detecting the longitudinal acceleration of the vehicle, and a fuzzy rule using the running speed and the longitudinal acceleration of the vehicle as input conditions
Target assist amount setting means for setting a target assist amount based on the target assist amount .
As the longitudinal acceleration of the vehicle increases in the low speed range
Thus, the target assist amount is reduced .

[0025]

[0026]

[0027]

[0028]

The vehicle speed detecting means detects the running speed of the vehicle, and the longitudinal acceleration detecting means detects the longitudinal acceleration of the vehicle.
The target assist amount setting means sets the target assist amount based on a fuzzy rule using the traveling speed and the longitudinal acceleration of the vehicle as input conditions, so that optimum steering characteristics can be obtained according to the acceleration or deceleration traveling state of the vehicle. Together with
Fine control is possible with no rules. Also this eyes
The target assist amount setting means is configured to control the vehicle in a low-speed traveling region of the vehicle.
The target assist amount as the vehicle deceleration increases
So, for example, the vehicle enters the corner at low speed while decelerating
The steering force is almost the same as at the start of deceleration.
As a result, the loss of the steering force is prevented.

[0029]

[0030]

[0031]

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0033]

FIG. 1 is a schematic diagram of a power steering hydraulic control unit according to an embodiment of an electronically controlled power steering apparatus of the present invention, FIG. 2 is a graph showing a membership function of vehicle speed used for fuzzy control, and FIG. Is a graph showing a membership function of vehicle speed × lateral acceleration used for fuzzy control, FIG. 4 is a graph showing membership functions of calculation of vehicle speed and lateral acceleration used for fuzzy control, and FIG. FIG. 6 is a graph showing calculation processing for obtaining the steering assist amount by the center of gravity method, FIG. 6 is a flowchart showing fuzzy control, and FIGS. 7 and 8 show the assist amount by the center of gravity method from each of the membership functions of vehicle speed and vehicle speed × lateral acceleration and longitudinal acceleration. FIG. 9 is a graph showing a specific control example of the arithmetic processing to be obtained, and FIG. Is shown. Note that members having the same functions as those in the related art are denoted by the same reference numerals, and redundant description will be omitted.

The electronically controlled power steering apparatus of this embodiment controls the power steering hydraulic control unit by fuzzy inference. The mechanical part (hard structure) of the electronically controlled power steering apparatus is as described above. The configuration is almost the same as that of the conventional example, and that point will be described briefly.

As shown in FIG. 1, the input shaft 1
Reference numeral 1 receives a steering force from a steering wheel (handle) (not shown), and is rotatably supported in a casing 12. A pinion gear 13 is mounted at the lower end of the input shaft 11 so as to be relatively rotatable. A torsion bar 14 is provided inside a hollow portion of the input shaft 11, and only the upper end thereof is connected to the input shaft 11. The pinion gear 13 is serrated with the lower end of the torsion bar 14, and
This pinion gear 13 meshes with the rack 15,
The steering force of the input shaft 11 is transmitted to the pinion gear 13 via the torsion bar 14, and further transmitted to the rack 15, and the rack 15 can be driven in the axial direction to steer the wheels. .

The rotary valve 16 in the casing 12 opens and closes in accordance with the circumferential phase difference between the input shaft 11 and the pinion gear 13, and operates the hydraulic oil supply pipe 18 of the oil pump 17 and the oil reservoir 19. The oil discharge pipe 20 is connected. On the other hand, the power steering hydraulic cylinder 21 is configured such that a piston 23 is supported in a cylinder 22 so as to be movable in the axial direction, and a piston shaft 24 of the piston 23 is fixed in the middle of the rack 15. The piston 23 partitions the inside of the cylinder 22 left and right to form oil chambers 25 and 26.

Accordingly, when a steering force is input to the input shaft 11, the torsion bar 14 transmits the steering force to the pinion gear 13 while twisting, and the pinion gear 13 generates a phase difference with respect to the input shaft 11 on the steering side. The rotary valve 16 is driven according to the phase difference. When the hydraulic oil is supplied from the oil pump 17 to the oil chambers 25 and 26 of the hydraulic cylinder 22 in response to the opening and closing of the rotary valve 16, a steering assist force is applied to the rack 15, and a required steering force is applied in the steering direction. A steering assist force is generated.

A reaction force plunger 27 is provided on the outer periphery of the lower portion of the input shaft 11 to apply a steering reaction force during steering to increase the steering force (steering response).
To give a steering reaction force. That is,
In the present embodiment, four reaction force plungers 27 are provided at equal intervals in the casing 12 so as to surround the outer periphery of the input shaft 11, and a chamber 29 is formed on the outer end side thereof. On the other hand, the hydraulic control valve 28 is provided in the casing 12 adjacent to and parallel to the side of the input shaft 11. In the hydraulic control valve 18, the spool 3 is provided in the casing 12.
1 is provided so as to be movable up and down, and the spool 31 is biased and supported downward by a spring 32 provided at an upper portion. Further, a solenoid 33 is provided on a lower outer peripheral piece of the spool 31, and an upward axial force is applied to the spool 31 by exciting the solenoid 33.

The spool 31 has an oil reservoir 19.
Oil passages 34 and 35 communicating with the hydraulic oil discharge pipe 20 and an annular oil passage 36 communicating with the hydraulic oil supply pipe 18 of the oil pump 17 are formed, and the chamber 2 of the reaction force plunger 27 is formed.
An annular oil passage 38 that communicates with the hydraulic oil supply line 9 via a hydraulic oil supply / discharge pipe 37 and an oil passage 39 that interconnects the annular oil passages 36 and 38 are formed. Therefore, when the solenoid 33 is in the demagnetized state, the spool 31 is at the lowered position, the hydraulic oil supply pipe 18 communicates with the annular oil passage 36, and the hydraulic oil is supplied to the oil pump 17.
Is supplied to the hydraulic control valve 28 through the hydraulic oil supply pipe 18, and is supplied from the annular oil passage 36 to the chamber 29 of the reaction force plunger 27 through the oil passage 39 and the annular oil passage 38.
On the other hand, when the solenoid 33 is excited, the spool 31 is in the raised position, the hydraulic oil supply pipe 18 is not in communication with the annular oil passage 36, and the hydraulic oil is not supplied to the hydraulic control valve 28.

The hydraulic control valve 28 is controlled by a control unit (CU) 51. That is, the control unit 51 is connected with the vehicle speed sensor 41, the steering angle sensor 52, the engine speed sensor 42, and the like. The control unit 51 includes a lateral acceleration calculator 53 and a longitudinal acceleration calculator 5.
4 and a fuzzy calculation unit 55 for setting a target assist amount by fuzzy calculation. Then, the control unit 51, the lateral acceleration calculation section 53 calculates the lateral acceleration G _Y generated in the vehicle based on the steering angle ha inputted vehicle speed V inputted from the vehicle speed sensor 41 from the steering angle sensor 52. Further, the lateral acceleration calculator 53 multiplies the vehicle speed V by the calculated lateral acceleration G _Y to obtain a calculated value V · G _Y, which is output to the fuzzy calculator 55.

Further, the longitudinal acceleration computing unit 54, and outputs the fuzzy operation unit 55 calculates the longitudinal acceleration G _X generated on the vehicle based on the vehicle speed V inputted from the vehicle speed sensor 41. The fuzzy operation unit 55, a fuzzy operation from a longitudinal acceleration G _X input from the operation value V · G _Y input from the vehicle speed V and the lateral acceleration calculation unit 53 is input longitudinal acceleration computing unit 54 from the vehicle speed sensor 41 Then, the calculation result is output to the hydraulic control valve 28, and the amount of current applied to the solenoid 33 is set to control the solenoid 33.

As shown in FIG. 2, the fuzzy calculation unit 55 includes a membership function for obtaining a degree of conformity (grade) relating to the running state from the vehicle speed V, and
A membership function for calculating the fitness for the calculated value V · G _Y obtained by multiplying the vehicle speed V by the lateral acceleration G _Y , and a membership for calculating the fitness for the calculated value of the vehicle speed V and the longitudinal acceleration G _X as shown in FIG. By applying the function, the fitness of the vehicle speed V and the fitness of the calculated values V · G _Y , the vehicle speed V and the longitudinal acceleration G _X in the running state of the vehicle are determined.
As shown in FIG. 5, the control amount, that is, the steering assist amount is determined from the graph indicating the set of tables by the center of gravity method, and the amount of current applied to the solenoid 33 is controlled based on these degrees of conformity. .

In the present embodiment, the running state is divided into three stages as shown in FIG. 2 as a membership function of the vehicle speed V, and the vehicle speed V is set to 0 to 85 km / h in the "low speed running mode".
30-140km / h "medium speed driving mode", 85km / h
The above is set as the "high-speed running mode", and the degree of conformity to these modes is determined according to the vehicle speed V. On the other hand, the evaluation of the assist control amount is divided into three stages as shown in FIG. 5, and is set to “S (small)”, “M (medium)”, and “B (big)”. In S, the assist amount is 100%, and in Evaluation B, the assist amount is 0%.
%.

Then, regarding the low speed running mode of the membership function of the vehicle speed V, the evaluation S of the assist control amount, and
Evaluation M is made for the medium-speed running mode, and evaluation B is made for the high-speed running mode. That is, a rule is set such that when the vehicle speed V increases, the steering assist amount is reduced to make the steering wheel heavier.

Further, the running condition as a membership function of the operation value V · G _Y obtained by multiplying the lateral acceleration G _Y in the vehicle speed V, the as shown in FIG. 3, operation value V · G _Y is 0~100Gkm / h
Until the area, fitness is increased linearly according to the increase of the calculated value V · G _Y, the operation value V · G _Y is 100Gkm / h or more areas, regardless of the increase of the calculated value V · G _Y The fitness is set to be constant. Then, the calculated value V
Membership function G _Y is made to correspond to the evaluation B of the assist control amount according to the goodness of fit. That is, the operation value V
· G _Y is heavier handle to reduce the steering assist amount to rise, is set a rule that.

Further, the vehicle speed V and the longitudinal acceleration G_XCalculated value of
Of the membership functions of
I am trying to adopt it. That is, the membership of the vehicle speed V
As shown in FIG. 4 (a), the running state as a function
Is constant and constant up to the range of 0 to 30 km / h.
The vehicle speed V increases until the vehicle speed V reaches 30-60 km / h.
The degree of conformity decreases linearly with increasing vehicle speed, and vehicle speed V increases
h, the fitness is set to 0 in the region
I have. Also, the longitudinal acceleration G_XAs a membership function of
As shown in FIG._XBut
The fitness at 0 G is 0, and the longitudinal acceleration G_XBut
Front-rear acceleration up to the range of 0 to -0.5G on the deceleration side
G_XFit increases linearly with the increase in
Degree G_XIs in the range of -0.5 to 1.0 G, the fitness is 1
It will be constant. On the other hand, the longitudinal acceleration G _XBut on the acceleration side
The degree of conformity is set to 0.

[0047] In this embodiment, it employs a smaller one of the fit to the membership function of the fit and the longitudinal acceleration G _X for the membership function of the vehicle speed V. In this method of determining the degree of conformity, not only a method of adopting the smaller one but also an average value may be employed. The membership function of the vehicle speed V or the longitudinal acceleration G _X is made to correspond to the evaluation M of the assist control amount according to the goodness of fit. That is, heavier handle to reduce the steering assist amount and the acceleration G _X is longitudinal increases at low-speed running state of the vehicle, is set a rule that.

Based on the degree of conformity of the vehicle speed V, the degree of conformity of the calculated value V · G _Y , and the degree of conformity of the longitudinal acceleration G _X (vehicle speed V) obtained in this manner, using the graph of the arithmetic processing shown in FIG. The target assist amount can be obtained by the center of gravity method.

Here, the control procedure of the control unit 51 in the above-described electronically controlled power steering apparatus of the present embodiment will be described with reference to the flowchart of FIG.

As shown in FIG. 6, first, in step S1, the vehicle speed sensor 41 detects the running speed V of the running vehicle, and outputs the vehicle speed sensor signal to the CU 51 (the lateral acceleration calculator 53 and the longitudinal acceleration calculator 54). , Fuzzy operation unit 55)
And the process proceeds to step S2. In step S2, the steering angle sensor 52 detects the steering angle ha of the vehicle, outputs a steering angle sensor signal to the CU 51 (lateral acceleration calculation unit 53), and proceeds to step S3. In step S3,
CU51 is an analog signal as a sensor signal of the vehicle speed V and the steering angle ha and conversion into a digital signal, and calculates the lateral acceleration G _Y generated in the vehicle based on at lateral acceleration calculation unit 53 and the vehicle speed V and the steering angle ha . Further, in step S4, multiplied by the lateral acceleration G _Y of the vehicle speed V by obtaining the operation value V · G _Y.
Further, in step S5, and calculates the longitudinal acceleration (acceleration or deceleration) G _X occurring in the vehicle based on at longitudinal acceleration computing unit 54 to the vehicle speed V.

Then, in step S6, the fuzzy operation unit 55 obtains the degree of conformity with respect to the running state of the vehicle speed V from the graph of the membership function shown in FIG.
Seeking fit about the traveling state of the operation value V · G _Y from the graph of the membership functions shown in further obtains the fitness concerning the traveling state of the longitudinal acceleration G _X from the graph of the membership function shown in FIG. Then, in step S7, a target assist amount is determined by the centroid method using the graphs of the arithmetic processing shown in FIG. Further, in step S8, the target assist amount is converted into a current amount to be applied to the solenoid 33 of the corresponding hydraulic control valve 28, and in step S9, the current amount for controlling the steering assist amount is converted into a drive circuit, that is, a hydraulic control. Valve 2
8 to the solenoid 33.

Here, a specific fuzzy control in the running state of the vehicle will be described based on the calculation processing for obtaining the assist amount by the center of gravity method shown in FIGS. For example, when the vehicle travels straight at a vehicle speed V of 30 km / h, the vehicle speed V
Starts turning at 20 km / h. This situation corresponds to a situation in which the vehicle enters a corner while decelerating in the low-speed traveling mode. In this case, the vehicle speed V is 3
Lateral acceleration G _Y when traveling straight at 0 km / h is 0 G
The longitudinal acceleration (deceleration) G _X is also zero. Further, the lateral acceleration G _Y when the vehicle is turning at a vehicle speed V of 20 km / h.
Is about 0.4G, and the longitudinal acceleration (deceleration) G _X is-
0.4G.

Therefore, as shown in FIG. 7, the vehicle speed V
Is traveling straight at 30 km / h, the fitness in the low-speed traveling mode is 1, and the evaluation of the assist control amount corresponding to the low-speed traveling mode is S. Since the lateral acceleration G _{Y at} this time is 0 G, the calculated value V · G _Y is also 0 G · km.
/ H, and the matching degree is 0. Furthermore, the calculated value of the vehicle speed V and the longitudinal acceleration G _X in this case, the vehicle speed V 30
Although fit in km / h is 1, and 0 are fit since the longitudinal acceleration (deceleration) G _X is fit because it is 0G adopts towards zero, smaller of the two.

On the other hand, as shown in FIG.
When the vehicle starts decelerating turning at 20 km / h,
In the low-speed driving mode.
The evaluation of the cyst control amount is S. Also, at this time
Speed G_YIs 0.4G, which corresponds to the vehicle speed V (20 km / h).
Lateral acceleration G_YThe calculated value VG multiplied by (0.4G) _Y
Is 8 Gkm / h, and the adaptability is 0.08. Change
The vehicle speed V and longitudinal acceleration G at this time_XCalculated value of
Although the vehicle speed V is 20 km / h and the degree of conformity is 1,
Longitudinal acceleration (deceleration) G_XIs -0.4G
The degree is 0.8 and the smaller of the two is adopted
And the degree of conformity is 0.8.

Then, the vehicle speed V and the vehicle speed V
Calculated value VG_Y, Longitudinal acceleration (deceleration) G_XIs the fitness of
By the centroid method, that is, the weight of the total area corresponding to the fitness
The target assist amount is determined by obtaining the center position. Immediately
In a straight running state at a vehicle speed V of 30 km / h, FIG.
As shown, the evaluation of the assist control amount with respect to the vehicle speed V is S
And its fitness is 1, and the calculated value VG_YAbout
Is 0, longitudinal acceleration G _XIs zero for
You. Therefore, the assist amount is 100%. On the other hand, vehicle speed
FIG. 8 shows a state in which the vehicle is running at a reduced speed at V of 20 km / h.
As described above, the evaluation of the assist control amount with respect to the vehicle speed V is performed in S.
Is 1 and the calculated value V · G_YAssistance for
The evaluation of the control amount is B, its fitness is 0.08, longitudinal acceleration
G_XThe evaluation of the assist control amount with respect to M is M
0.8. Therefore, the assist amount is 75%.

As described above, when the vehicle is running at a vehicle speed V = 30 km / h,
Start decelerating turn at vehicle speed V = 20km / h from forward running state
The vehicle speed V decreases, but the lateral acceleration G_YAnd before and after
Acceleration (deceleration) G_XRises, so power steering
The steering assist amount of the steering is reduced to 75%. Immediately
When the vehicle decelerates, the vehicle speed V decreases.
Increased the amount of power steering assist
The dollar is lighter. However, in this case,
Longitudinal acceleration G_XWorks and the vehicle turns.
Lateral acceleration G_YTo operate the steering wheel.
This may be difficult. Therefore, in this embodiment,
Acting lateral acceleration G_YAnd longitudinal acceleration G _XMembership
By applying it as a loop function,
When the vehicle enters the corner, the lateral acceleration G_YAnd longitudinal acceleration
G_XOf steering assist of power steering
To make the handle a bit heavier than usual.
is there.

When the vehicle enters a corner while accelerating, the vehicle speed V increases in accordance with the acceleration and the lateral acceleration G _Y and the longitudinal acceleration G _X increase.
Since the reduction of the steering assist amount of the power steering is superimposed, the steering wheel becomes heavy.

[0058] As described above, in the electronically controlled power steering apparatus of this embodiment, in addition to the increase or decrease of the vehicle speed V, the applied acceleration G _X as a membership function before and after,
Since the steering assist amount is controlled by fuzzy inference corresponding to this membership function, when the vehicle decelerates,
Since the longitudinal acceleration G _X (deceleration) increases, the degree of decrease in the assist amount increases, and the handle becomes heavier by that much. Therefore, even when the vehicle speed is different, at the time of deceleration, the driver can operate while realizing the operation with the steering wheel.

Also, the electronically controlled power steering of this embodiment
In the case of a ring device, the vehicle speed V and the lateral acceleration G_YMultiply by
Calculated value VG_YIs applied as a membership function,
Fuzzy inference corresponding to these membership functions
The steering assist amount is controlled by the
When entering the vehicle, the lateral acceleration G_Y(Steering angle) is large
As a result, the degree of decrease in assist amount increases, which is
Handle becomes heavy. Therefore, even if the vehicle speed condition is different
When entering a corner, the driver always
You can steer while feeling the approach with the steering wheel. Ma
The lateral acceleration G _YThis membership in the membership function
Speed G_YSteering linear whose degree of conformity changes linearly with respect to
The steering linearity.
Secured.

Further, in the electronically controlled power steering apparatus of the present embodiment, a calculation value V · G _Y obtained by multiplying the vehicle speed V and the lateral acceleration G _Y is applied as a membership function for controlling the steering assist amount. since, at the time of high speed running of the vehicle, since the lateral acceleration G _Y is less steering angle is also sufficiently large speed V decreases, is no longer significant reduction in calculation value V · G _Y, width of the target assist amount There is no significant increase and the handle is not so light. Therefore, the steering operation feeling during high-speed running of the vehicle is sufficiently maintained, and the stability of the steering operation is improved.

In the electronically controlled power steering apparatus according to the present embodiment, the "vehicle speed V
And the rule that "when the calculated value V · _GY increases, the steering assist amount is reduced and the steering wheel becomes heavy" and "when the vehicle runs at a low speed. in to reduce the steering assist amount and the acceleration G _X is longitudinal raised heavier handles "
By controlling the steering assist amount based on the three rules, more precise control can be performed with a small number of rules.

Here, in the case where such an electronically controlled power steering apparatus of this embodiment is applied to a vehicle, the control effect at the time of deceleration of the vehicle will be specifically evaluated based on experiments. That is, the control effect at the time of deceleration of the vehicle is as shown in the graph of FIG. In FIG. 9, the horizontal axis represents time, and the vertical axis represents steering angle, lateral acceleration, longitudinal acceleration, and steering force from the top, respectively. The solid line is the electronically controlled power steering device (EPS) of the present embodiment, and the dotted line is the conventional electronic steering system. Control type power steering device (EP
S).

[0063] As shown in FIG. 9, when braking the vehicle by maintaining a constant steering angle ha, acceleration G _X is increased before and after that time. In such a running condition of the vehicle, in the conventional EPS, since the vehicle speed V decreases as the vehicle decelerates, the steering assist amount increases, the steering force ha decreases, and the steering wheel becomes slightly lighter. Therefore, steering force loss occurs at this time. On the other hand, in the EPS of this embodiment, the vehicle is braked, because the vehicle speed V is reduced by reduction, but tends to increase the handle assistance amount, the acceleration G _X is increased before and after this time Then, control is performed to reduce the steering assist amount, and the steering force ha is maintained at a constant level substantially the same as the steering force at the start of deceleration without decreasing the steering force ha. Therefore, the steering wheel is not lightened, and the driver can obtain the optimum steering force, and the steering force does not drop out.

In the above-described embodiment, the control system of the electronically controlled power steering device has been described as a hydraulic system. However, the present invention is not limited to this, and the present invention is not limited to the electric power steering device using a motor. The same effects can be obtained even when the present invention is applied, and the mechanical system of the electronically controlled power steering device is not limited to the above-described embodiment, but can be applied to any of them. Can be done.

In the above embodiment, the control
A lateral acceleration calculator 53 is provided in the
The vehicle speed V input from the vehicle speed sensor 41 by the speed calculation unit 53
And the steering angle ha input from the steering angle sensor 52.
Lateral acceleration G occurring in the vehicle_YWas calculated, but
A lateral acceleration detection sensor is mounted on the vehicle and this lateral acceleration G _Y
May be directly measured. Further, the vehicle speed V and the lateral
Acceleration G_YCalculated value V · G_YMembership functions, list
The evaluation of the steering assist amount was divided into three stages,
For example, five stages may be used. And this steering assist amount
Although it was obtained by the centroid method, the maximum averaging method and the height method (Skelet
And the area method.

In the above embodiment, the control unit (target assist amount setting means) 51 sets the target assist amount based on the fuzzy rules.
The target assist amount may be set based on other control means.

[0067]

As described above in detail with reference to the embodiments, according to the electronically controlled power steering apparatus of the present invention, the vehicle speed is detected by the vehicle speed detecting means and the vehicle is detected by the longitudinal acceleration detecting means. And the target assist amount setting means sets the target assist amount based on the fuzzy rule using the running speed and the longitudinal acceleration of the vehicle as input conditions. making it possible to control the steering force can improve the steering feeling in accordance with the optimum steering characteristics in accordance with the deceleration state of the vehicle is obtained, it is possible to improve the stability of the steering operation , Fine steering control with few rules
Control, and a sense of stability and ease of handling depending on the vehicle speed.
Provides a balanced steering feel and steering
Increased linearity allows the driver to grasp the driving situation of the vehicle
And the steering performance can be improved. Ma
In addition, the target assist amount setting means determines that the traveling speed of the vehicle is low.
Target assist with increasing longitudinal acceleration of the vehicle in the area
The steering force at that time when the vehicle decelerates to reduce the amount
Is almost the same as at the start of deceleration, preventing loss of steering force.
Can be

[0068]

[0069]

[0070]

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a power steering hydraulic control unit according to an embodiment of an electronically controlled power steering device of the present invention.

FIG. 2 is a graph showing a membership function of vehicle speed used for fuzzy control.

FIG. 3 is a graph showing a membership function of vehicle speed × lateral acceleration used for fuzzy control.

FIG. 4 is a graph showing a membership function for calculating a vehicle speed and a lateral acceleration used for fuzzy control.

FIG. 5 is a graph showing an arithmetic process for obtaining a power steering assist amount from the fitness of each membership function by a centroid method.

FIG. 6 is a flowchart illustrating fuzzy control.

FIG. 7 is an explanatory diagram showing a specific control example of a calculation process for calculating an assist amount by a center of gravity method from respective membership functions of vehicle speed and vehicle speed × lateral acceleration and longitudinal acceleration.

FIG. 8 is an explanatory diagram showing a specific control example of a calculation process for obtaining an assist amount from the respective membership functions of vehicle speed and vehicle speed × lateral acceleration and longitudinal acceleration by a centroid method.

FIG. 9 is a graph illustrating an effect of preventing a loss of steering force by fuzzy control according to the present embodiment.

FIG. 10 is a schematic configuration diagram of a power steering hydraulic control unit representing an example of a conventional electronically controlled power steering device.

FIG. 11 is a sectional view taken along line XI-XI of FIG. 10;

FIG. 12 is a sectional view taken along line XII-XII of FIG.

[Explanation of symbols]

 Reference Signs List 11 input shaft 12 casing 13 pinion gear 14 torsion bar 15 rack 16 rotary valve 17 oil pump 19 oil reservoir 21 hydraulic cylinder 25, 26 oil chamber 27 reaction force plunger 28 hydraulic control valve 29 chamber 31 spool 33 solenoid 41 vehicle speed sensor 51 control unit ( CU) 52 Steering angle sensor 53 Lateral acceleration calculator 54 Front / rear acceleration calculator 55 Fuzzy calculator

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B62D 127: 00 (56) References JP-A-4-43168 (JP, A) JP-A-5-58325 (JP, A) ( 58) Field surveyed (Int.Cl. ⁶ , DB name) B62D 6/00

Claims (1)

(57) [Claims] 1. An electronically controlled power steering device for electronically controlling a steering assist amount in a steering mechanism of a vehicle, a vehicle speed detecting means for detecting a running speed of the vehicle, a longitudinal acceleration detecting means for detecting a longitudinal acceleration of the vehicle, comprising a target assist amount setting means for setting a target assist amount based on the fuzzy rules to speed and longitudinal acceleration of the vehicle as an input condition, the target assist amount
The setting means is provided for the front and rear of the vehicle in the low speed region of the vehicle traveling speed
An electronically controlled power steering device, wherein a target assist amount is reduced with an increase in acceleration .