JPH02290776A - Power steering device - Google Patents

Abstract

PURPOSE:To obtain the desired assistance quantity by the simple constitution by obviating the need of a table for converting the steering torque of a steering wheel on the basis of the car speed by executing power steering by utilizing the fuzzy calculation processing. CONSTITUTION:The steering torque of a steering wheel of a vehicle is detected by a torque sensor 2, and the speed of the vehicle is detected by a car speed sensor 5, and the outputs are inputted into a plurality of fuzzy inference parts 21-1-21-25. In each fuzzy inference part 21-1-21-25, fuzzy inference is carried out so that the assistance quantity is increased according to the increase of the steering torque in conformity with a previously determined rule, and the assistance quantity is reduced according to the car speed. While, in a determination part 22, the nonfuzzy determined value is obtained on the basis of the parallel outputs of the fuzzy inference parts 21-1-21-25. In an operation part 23, the assistance quantity for operating the steering wheel in a prescribed direction is outputted on the basis of the output of the determination part 22.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a power steering device that performs power steering using fuzzy control.

[Conventional technology]

Conventional electric power steering motor drive devices are as shown in Japanese Patent Application Laid-Open No. 156863/1983.
1st, 2nd and 3rd conductive, respectively, when steering in left and right directions.
．． A bridge connection is made around the steering motor using a control element such as a fourth transistor. When steering to the right, the first and second control elements are made conductive at the same time based on the detection of the steering torque, and a forward driving current flows to the motor, and when steering to the left, the third control element is made conductive based on the detection of the steering torque.
．． The fourth control element is made conductive at the same time to flow a drive current in the opposite direction to the motor to rotate the motor forward and reverse, respectively, thereby controlling the steering.

[Problem to be solved by the invention]

However, in such a conventional power steering device, the steering torque and the current flowing through the steering motor, that is, the steering assist force, have an almost one-to-one correspondence. However, even in vehicles of the same type, as the speed of the vehicle increases, the resistance received from the road surface decreases, so it is preferable to control the amount of assist to be small. In order to change the assist amount in this way, it is necessary to provide a torque table in the memory that converts the output obtained from the torque sensor using a vehicle speed signal, or to perform conversion processing on the torque signal. Therefore, the more detailed the torque value or vehicle speed value is, the larger the number of tables becomes, and the processing becomes more complicated.

The present invention has been made in view of the problems of conventional power steering devices, and is a technology that enables control by changing the amount of assist based on torque and vehicle speed with a relatively simple configuration. This will be a major issue.

[Means to solve the problem]

The present invention is a power steering device that performs a steering operation of a vehicle based on an input signal, and includes a torque sensor that outputs a torque signal in the operating direction of a steering wheel of a vehicle, a vehicle speed sensor that detects the speed of the vehicle, and a torque sensor that performs a steering operation of a vehicle based on an input signal. Fuzzy inference uses the signals obtained from the vehicle speed sensor and the vehicle speed sensor as input, and increases the amount of assist in response to an increase in the torque signal according to predetermined rules, and also decreases the amount of assist in response to the vehicle speed. a plurality of fuzzy inference units that perform this, a determining unit that obtains a non-fuzzy definite value based on the parallel outputs of each fuzzy inference unit, and an operation unit that outputs an assist ffi that operates the steering wheel in a predetermined direction based on the output of the determining unit. It is characterized by having the following.

[Effect]

According to the present invention having such features, the signals of the torque sensor and the vehicle speed sensor that output a 1-lux signal in the operating direction of the steering wheel are given to a plurality of fuzzy inference units, and fuzzy calculations are executed. Therefore, a predetermined fuzzy inference rule is created so that the amount of assist changes in response to the torque signal, and as the torque increases, the assist +-t increases, and as the vehicle speed increases, the amount of assist decreases. Fuzzy inference is executed based on each rule. Then, the output from each fuzzy inference section is given to the determining section to determine the non-fuzzy assist amount. Power steering is realized by operating the steering wheel in a predetermined direction based on this assist I.

〔Effect of the invention〕

Therefore, according to the present invention, by executing power steering using fuzzy calculation processing, there is no need to provide a conversion table or the like for converting a torque signal based on a signal from a vehicle speed sensor, and a desired amount of assist can be achieved with a relatively simple configuration. The effect is that power steering can be realized.

[Explanation of Examples]

FIG. 2 is a schematic diagram of a power steering mechanism to which the present invention is applied, and FIG. 1 is a block diagram showing the overall configuration of the fuzzy controller.

In FIG. 2, a torque sensor 2 and a transmission mechanism 3 for transmitting a steering force from the steering handle 1 are connected to the steering handle 1. The torque sensor 2 detects the torque of the steering wheel 1 in the left and right direction, and its output is given to the fuzzy controller 4. Further, the output of a vehicle speed sensor 5 that detects the speed of the vehicle is given to the fuzzy controller 4. The fuzzy controller 4 is connected to the vehicle's battery 6 and controls a steering motor 7 that drives in the left-right direction in response to a left-right torque signal given from the torque sensor 2. The wheel 8 is rotated by a predetermined angle in the left-right direction.

Next, the configuration of the fuzzy controller 4 will be explained with reference to FIG. In the present invention, signals from the torque sensor 2 that detects the driving torque of the steering shaft and the vehicle speed sensor 5 are used to determine the assist amount of the power steering. That is, the output of the torque sensor 2 and the vehicle speed sensor 5
The output is transmitted to a plurality of fuzzy inference units 2l-1 to 21-25, 25 in this embodiment, as shown in FIG. These fuzzy inference units are inference units that perform fuzzy inference according to predetermined rules based on the torque signal and vehicle speed signal, as described later, and their outputs are sent to the fuzzy determination unit 2.
2 can be conveyed. The fuzzy determining section 22 calculates the maximum value of each output section based on the parallel outputs obtained from each fuzzy inference section. Then, fuzzy definite values are obtained based on the centroid values of those outputs. This output is then given to the steering motor 7 as a drive signal via the motor drive section 23. Steering motor drive section 23
is an operation unit that drives the steering motor 7 according to a given operation amount.

Next, the configurations of the fuzzy inference section and determination section that perform fuzzy processing will be further explained. As shown in the figure, each fuzzy inference section has a membership function generation circuit (M
FC) and a membership function generator (MFG) that generates a membership function according to the assist 1 amount to be output.
) is provided. Now, in this embodiment, the torque input state is expressed as a Mahership function by 7 as shown in Fig. 3 (al).
The vehicle speed is divided into four states as shown in Figure 3 (bl). Here, NL is a large negative value, NM is a medium negative value, and NS is a negative medium value. NVS is a small negative value, ZR is almost zero, PVS is a small positive value, PS is a slightly small positive value, PM is a medium positive value, and PL is a large positive value. Also, the Mahership function of the assist force is N as shown in Figure 3 (Cl).
It is assumed that the L-PL is divided into nine states.

Next, the fuzzy inference units 21-1 to 21-25 will be explained. Each fuzzy inference unit except the fuzzy inference unit 21-25 has two MFCs 311 to 31-24. 32
-1 to 32-24. Fuzzy inference section 21-
1 is an inference unit that performs the inference of rule 1 as described later, and MFC31-1, 32-1 are respectively P of torque input S1.
This is a generation circuit (MFC) that generates a membership function of ZR of S and vehicle speed input S2, and the respective outputs are given to the MIN circuit 34-1. Also, MFG35-1 is shown in Figure 3 (C
This is a membership function generator (MFG) that generates a parallel membership function PM of assist output shown in 1, and its parallel output is given to the MIN circuit 36-1.

The MIN circuit 36-l generates a smaller parallel fuzzy signal by comparing it with the output of the MIN circuit 34-1, and its output is given to the MAX array circuit 37.

Next, the inference rules determined based on these inputs are shown below.

(Rule 1) If the torque input (S1) is PS and the input (S2) from the vehicle speed sensor 5 is ZR, let the assist output (E) be PM.

This rule l is simplified and expressed as follows.

If S1=ZR and S2=ZR then
PMSuch a rule is established so that the larger the signal from the torque sensor 2 becomes, the larger the assist i becomes, and the larger the signal from the vehicle speed sensor 5 is, the smaller the assist amount is controlled. . Such rules are shown in the table below.

In this way, 25 inference rules are defined. The fuzzy inference units 21-1 to 21-25 are inference units that execute respective fuzzy inferences, and the parallel fuzzy outputs that are the inference results of the respective rules are the fuzzy inference units 21-1 to 21-2.
5 to the MAX7tz circuit 37. The MAX array circuit 37 calculates the maximum value for each corresponding parallel line, and its parallel output is given to the defuzzifier circuit 38. Defuzzifier circuit 38
obtains a non-fuzzy output by calculating the center of gravity of the output, and the output is given to the motor drive section 23, which is the operating section.

Next, the operation of this embodiment will be explained. When the driver operates the steering wheel, a torque signal is obtained from the torque sensor 2 in response to the operation.

Also, while the vehicle is running, a vehicle speed signal is always obtained from the vehicle speed sensor 5. These signals are given to each fuzzy inference section 21-1 to 21-25 as described above, and the NL-PL signal is outputted by each MFC.

For example, as shown in FIGS. 3(a) and 3(b), the torque input 31 is at a predetermined value S1. and PS=0.7, PM=0.
The input 82 from the 3-way vehicle speed sensor 5 is a predetermined value S2. As shown in the figure, PM=0.8, P L=0.2
In this case, the MFC of the fuzzy inference section obtains a corresponding output, and the MIN circuit 34 outputs a signal with a smaller value. In this case, rules 3 and 4 in the rule table mentioned above. Rule 7.8 is applied, and the respective assist outputs E are as follows.

PVS=0.7, PVS=0.2, PS=0.3 and PVS=0.2 Therefore, fuzzy parallel outputs are obtained from 4 of the 25 fuzzy inference units, and these outputs A MAX calculation is performed by the MAX array circuit 37 of the determining section 22. As a result, as shown in FIG. 4, an output as shown by the broken line of the assist output Maber-Sissop function is obtained. The defuzzifier circuit 38 calculates the assist amount E1 by calculating the center of gravity of this signal. This assist i is given to the motor drive section 23.

The motor drive unit 23 drives the steering motor 7 based on the amount of assist given in the operating direction of the torque sensor 2 . In this way, the amount of steering operation is calculated based on the torque and vehicle speed, and steering is performed accordingly.

Although this embodiment describes a power steering device that performs fuzzy inference according to the M[N-MAX calculation rule, the present invention can also be realized by fuzzy inference according to other calculation rules. Furthermore, fuzzy processing is carried out using dedicated devices for fuzzy inference (for example, Nikkei Electronics, July 28, 1987, p. 148-
Page 152. Nikkei McGraw-Hill) as well as highnary-type computers programmed to perform fuzzy inference. It can also be realized by a processor or the like. Further, the Maher-Sissop function is not limited to a triangular shape as shown in FIG. 3, but may be of any shape. Further, the Maversysop function and the inference rules can be changed or modified as appropriate depending on the control results, etc.

Although this embodiment describes an electric power steering device, the present invention can also operate a hydraulic power steering mechanism based on the calculated assist it.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the overall configuration of an electric power steering device according to an embodiment of the present invention, FIG. 2 is a schematic diagram of an electric power steering mechanism to which the power steering device according to this embodiment is applied, and FIG. 3 (al is the Maber-Syssop function of the torque input, Figure 3 (b) is the Maher-Syssop function of the vehicle speed signal, Figure 3 (C) is a diagram showing the Maber-Syssop function of the assist output, and Figure 4 shows the Mae-Syssop function of the vehicle speed signal for a given torque input and vehicle speed input. It is a graph showing the center of gravity calculation process of the assist output obtained based on the steering wheel.
1... Conduction mechanism 4-... Fuzzy con 5-
・-・Vehicle speed sensor 7-・1・Steering 21-1~2
1-25...Fuzzy/definite part 23-...
-Motor drive 2...1--MFC 34 36-/35--
-1--MFG 37・-・-M38・-1---
- Defuzz fire circuit trolling motor inference section 22.1. Moving section 31-3 MIN circuit AX array circuit patent applicant Tateishi Electric Co., Ltd. agent Patent attorney Yoshiki Okamoto (and one other person) Figure (a) Figure (C) Figure (b) Figure

Claims (1)

[Claims] (1) A power steering device that performs a steering operation of a vehicle based on an input signal, comprising: a torque sensor that outputs a torque signal in the direction in which the steering wheel of the vehicle is operated; a vehicle speed sensor that detects the speed of the vehicle; and the torque The sensor and the signal obtained from the vehicle speed sensor are input, and the amount of assist is increased in response to an increase in the torque signal according to a predetermined rule, and the amount of assist is decreased in response to the vehicle speed. a plurality of fuzzy inference units that perform fuzzy inference; a determining unit that obtains a non-fuzzy definite value based on parallel outputs of the respective fuzzy inferring units; and an assist amount for operating the steering wheel in a predetermined direction based on the output of the determining unit. A power steering device comprising: an operation section that outputs an output.