JP3143605B2 - Electric power steering control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an electric power steering device for a vehicle, and more particularly to an electric power steering device for a general-purpose vehicle.

[0002]

2. Description of the Related Art Currently, vehicles equipped with power steering are rapidly increasing in terms of operability and safety. Most of these are hydraulically controlled, but these have had the problem that the oil pump for power steering must be driven even when the engine is idling.
A power steering device using an electric motor (hereinafter referred to as an electric power steering) has attracted particular attention because of its fuel efficiency, high degree of freedom in installation, light weight, high degree of freedom in setting characteristics, and the like.

In electric power steering for vehicles, when steering assist is stopped in a state where torque is applied to the steering wheel, tire twisting or the like becomes a spring, a reaction force is generated in the steering, and torque is generated in a direction in which the steering returns. May take a while.

Therefore, as proposed in Japanese Patent Publication No. 7-94227, for example, after the electric motor control operation is stopped, the electric motor control signal is gradually reduced (hereinafter referred to as "fade-out control") to perform steering. There has been proposed a device in which the steering torque of the rider is gradually increased to prevent a remarkable decrease in the steering feeling.

[0005]

FIG. 7A is a time chart showing a conventional fade-out control method showing a motor control signal with respect to a time axis. During this motor (assist) control, due to the characteristics of the electric motor,
As shown in FIG. 7B, there are a region where the reaction force is equal to or less than the assist force and a region where the reaction force exceeds the assist force. In the area where the reaction force is less than the assist force, the driver does not feel the reaction force, but if the reaction force exceeds the assist force after a certain period of time, the driver may suddenly feel the reaction force, reducing the steering feeling. I was

In particular, when the conventional control is applied to a general-purpose vehicle for various operations, it is necessary to take a long time (fade-out control time) from the generation of a stop signal to the stop of the control operation due to the rigidity of the vehicle. As shown in FIG. 7C, t1 ′
Is longer, the time from when the stop signal is output to when the reaction force is felt becomes longer, and the user feels more uncomfortable. Also,
The longer the time t2 ', the longer the time from the stop signal to the end of the assist, so that the power consumption increases.

An object of the present invention is to solve the above-mentioned problems and improve the steering feeling.
An object is to reduce power consumption.

[0008]

According to one aspect of the present invention, there is provided an electric power steering apparatus for a vehicle, comprising: an electric motor for generating a steering assist force in response to steering of a steering wheel;
An electric motor control signal output unit that outputs a signal for controlling the electric motor; a steering state detection unit that detects a steering state of the steering wheel; and the electric motor control based on a detection result of the steering state detection unit. An electric motor control unit that controls the electric motor using a signal output by a signal output unit; and an electric motor control operation stop signal detection unit that detects an operation stop signal of the electric motor control unit. when the front kidou operation stop signal is detected by the control operation stop signal detecting means immediately lowers the electric motor control signal to a predetermined level, was constructed as thereafter gradually decreases. Here, the predetermined level is appropriately set so that the driver does not feel uncomfortable above and below a boundary line where the reaction force and the assist force balance.

[0009] In claim 2 wherein the front when kidou operation stop signal is detected, lowers the electric motor control signal after a predetermined time has elapsed to a predetermined level, was constructed as thereafter gradually decreases.

According to a third aspect of the present invention, the predetermined level is such that the force that the steering wheel receives from the road surface is :
The value is close to a value that reverses from an area lower than the steering assist force to an area higher than the steering assist force.

According to a fourth aspect of the present invention, there is provided an electric power steering apparatus for a vehicle, the electric power steering apparatus comprising: an electric motor that generates a steering assist force in response to steering of a steering wheel; An electric motor control signal output unit that outputs a signal for controlling, a steering state detection unit that detects a steering state of the steering wheel, and the electric motor control signal output unit based on a detection result of the steering state detection unit. An electric motor control unit that controls the electric motor using the output signal; and an electric motor control operation stop signal detection unit that detects an operation stop signal of the electric motor control unit. when the front kidou operation stop signal is detected by the detection means, immediately the electric motor When together with lowering the control signal, it changes its decreasing rate to over time small, before
Increase the decrease speed up to a predetermined level, and
When the level falls below the level, the size is reduced .

[0012] In the 5 claims, before when kidou operation stop signal is detected, when the electric motor control operation stop signal is detected by the electric motor control operation stopping signal detecting means after a predetermined time has elapsed, the The electric motor control signal is reduced, and the reduction speed is changed so as to decrease with time. Therefore, in any case, the driver can be prevented from feeling the reaction force after a lapse of some time from the detection of the steering assist stop signal, so that the steering feeling can be further improved.

[0013]

According to a sixth aspect of the present invention, the steering state detecting means detects the steering state of the steering via at least one of a torque detecting means, a twist detecting means, a steering angle detecting means and a steering angular velocity detecting means. It was configured so that Therefore, the number of sensors suitable for the vehicle can be appropriately selected.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing the whole of a general-purpose vehicle equipped with an electric power steering control device according to the present invention, and FIG. 2 is an explanatory diagram of a steering system to which the present invention is applied.

Hereinafter, a description will be given with reference to FIGS. It should be noted that the electric power steering control device according to the present invention has a remarkable effect when mounted on a general-purpose vehicle. Therefore, the following description will be given by taking an example in which the electric power steering control device is mounted on a general-purpose vehicle.

The general-purpose vehicle 10 includes a transmission (not shown), a steering wheel 14, and a key switch 16 near the driver's seat 12. When the key switch 16 is turned on, the current of the battery 18 is supplied,
0 is started, the speed is changed by the transmission, and moves forward and backward.

The steering wheel 14 arranged in the driver's seat 12 as described above is connected to a steering shaft 20, and the steering shaft 20 is connected to the connecting shaft 2 via universal joints 22, 24.
6.

The connecting shaft 26 is a known steering mechanism 2 of a rack and pinion type or the like.
8, the steering mechanism 28 is connected to the connecting shaft 26 from the steering wheel 14.
The rotational motion transmitted to the front axle 30 is converted into a reciprocating motion of the front axle 30 to steer the two front wheels 32 in a desired direction.

As shown in FIG. 2, the steering shaft 2
Around 0, a steering angle sensor 36 and a torque sensor 38 are arranged, and output signals corresponding to the steering angle of the steering shaft 20 and the steering torque generated on the steering shaft 20 by operating the steering wheel 14, respectively. An engine speed sensor 40 is disposed at an appropriate position of the internal combustion engine (not shown), and the engine speed NE is set.
And a vehicle speed sensor 42 is disposed at an appropriate position near the wheel 32 to detect the vehicle speed VP.

The electric power steering control device according to this application includes a controller 50 including a microcomputer 44 and the like, and receives an output signal from the rotation speed sensor 40 and an output signal from the vehicle speed sensor 42 and the like. Since the present invention and the drive system do not have a deep relationship in configuration, detailed description of the drive system is omitted.

In the controller 50, the discrimination signal and each output signal are transmitted to the microcomputer 4
4 and the like, and an electric motor drive circuit 54 including an FET and the like is provided, and outputs and drives a motor control signal to the electric motor 56 so that the steering shaft 20 Apply assist torque.

Next, the operation of the electric power steering control device according to the present application will be described with reference to the flow charts of FIGS. 3 and 4 and the time chart of FIG. FIG.
And FIG. 4 are continuous flow charts showing the assisting operation of the device according to the present invention, and FIG. 5 is a time chart showing the motor control signals indicated by the flow charts of FIGS. It is. The illustrated program loops every 10 msec.

First, in S10, the flag F. FDOW
It is determined whether the bit of N is 1 or 0. This means that it is determined from the output of the rotation speed sensor 40 and the like and the operating state whether or not a known assist condition not described in this flowchart is satisfied.

At S10, the flag F. When the FDOWN bit is 1, no assist is performed, so the process proceeds to S12, where the motor control signal target value FDOBJ is set to 0. S12
Setting the target value of the motor control signal to 0 means that the fade-out control is started if the steering torque is currently being assisted, and that the state is maintained if the steering torque is not currently assisted. means.

Flag F. When the bit of FDDOWN is 0, the process proceeds to S14 to S16, and a failure signal output when an abnormality is detected from the steering angle sensor 36 or a failure signal output when an abnormality is detected from the torque sensor 38. Is detected, and if detected, a flag U.S. corresponding to each fail signal is detected in each step. FSA23, U.S.A. The bit of FSA21 is set to 1.

If the above failure has not been detected, the process proceeds to S18, where the flag U.S. Set FAIL0 bit to 0
To indicate that there is no failure and S
Proceed to 22 to set the motor control signal target value FDOBJ to MAX. If it is determined that a fail signal is detected in either S14 or S16, S2
0 and the flag U. The bit of FAIL0 is set to 1 and it is determined that a failure exists, the process proceeds to S12, and the motor control signal target value FDOBJ is set to 0.

Setting the motor control signal target value FDOBJ to MAX in S22 means that the motor control signal is gradually increased when steering torque assist is not currently performed (hereinafter referred to as "fade-in control"). ), And if steering torque assist is currently being performed, this means that steering torque assist is continued.

The processes from S10 to S22 are not different from the conventional steering torque assist method. Next, S2 of the flow chart of FIG. 4 which is continuous with the flow chart of FIG.
Then, the process proceeds to step 4 and thereafter to perform an increase / decrease operation or a continuous operation of the assist.

In S24, it is determined whether or not the motor control signal target value has changed compared to the current motor control signal. Specifically, the motor control signal target value FDOBJ set in S12 and S22 and the current motor control signal FDRT
02, and if they are the same, it is determined that the control signal currently instructing the motor is to be continued, and the process advances to S26 to change the current motor control signal FDRT02 to the motor control signal FDR.
As TO , the electric motor 56 is driven to end the program.

At S24, the current motor control signal FDRT0
If 2 is different from the motor control signal target value FDOBJ, the process proceeds to S28, and it is further determined whether or not the motor control signal target value is larger than the current motor control signal. If the motor control signal target value is larger than the current motor control signal in S28, the process proceeds to S30, and the flag F. Set the FD1ST bit to 0
Set to. This flag is a flag for indicating that the flow is not the first time in the next and subsequent loops.

Then, the program proceeds to S32, in which a value obtained by adding a predetermined amount dx to the current motor control signal FDRT02 is used as the motor control signal FDRT02. Next, the process proceeds to S34, and it is determined whether or not the current motor control signal FDRT02 exceeds the control signal maximum value MAX. If it is determined that the time exceeds the threshold, the fade-in control needs to be already terminated.
The process proceeds to S26 using T02 as a control signal, and the electric motor 56 is driven.

If it is determined in S34 that the following is being performed, the fade-in control is still being performed, so that S36 is skipped and the value set in S32 is used as the motor control signal in S2
Then, the program proceeds to 6, and the electric motor 56 is driven. Note that the fade-in control time in this embodiment is the same as the above S1.
Steps S0 to S24, S28, and S30 to S36 are looped as appropriate, and the processing ends in 0.85 sec.

At S28, the current motor control signal FDRT0
2 is determined to be greater than or equal to the motor control command value FDOBJ, the process proceeds to S38, and the flag F. The bit of FD1ST is determined, and it is determined whether or not the current loop is the first time. Flag F. If it is determined that the bit of FD1ST is 0, that is, it is determined that the loop is the first loop, the process proceeds to S40, and the current motor control signal is set near the threshold between the region where the driver feels the reaction force from the steering wheel 14 and the region where the driver does not feel the reaction force ( Α to β in FIG.
(Level) x (α <x <β) appropriately set in (interval)
Compare with Here, the threshold value is a value which is determined by the characteristics of the electric motor and the vehicle body and divides an area as shown in FIGS. 7 (b) and 7 (c). Above and below the boundary where the balance occurs, the distance is appropriately set so that the driver does not feel uncomfortable. More specifically, it is set appropriately according to the characteristics of the vehicle to which the present invention is applied.

In S40, if it is determined that the current motor control signal is equal to or greater than x, the flow proceeds to S42, where the target value of the motor control signal is x, and the flow proceeds to S44, where the flag F. The bit of FD1ST is set to 1, and the process proceeds to S46. Here, the flag F. Since the bit of FD1ST is set to 1, the next loop is determined to be not the first loop in S38, and S40 to S44 are skipped. When the target value of the motor control signal is smaller than x in S40, the fade-out control is started from the current motor control signal, so that S42 is skipped.

In S46, the value obtained by subtracting dx '(dx'> dx) from the current motor control signal FDRT02 is replaced with the motor control signal, and the flow advances to S48 to compare the current motor control signal FDRT02 with 0. It is determined whether to end the fade-out control. The fade-out control is completed by repeating the loop of S10 to S24, S28, S38 to S50 an appropriate number of times. Specifically, this means that when the motor control stop signal is detected, the electric motor control signal is immediately reduced to a predetermined level, and then gradually reduced.
In this embodiment, the fade-out control time when the decrease starts from x is 5.12 sec.

If it is determined in S48 that the motor control signal has fallen below 0, that is, if it is determined that the fade-out control has been completed, the process proceeds to S26 with the motor control signal target value as the motor control signal, and The program 56 is driven to end the program.

In the fade-out control operation according to the flow charts of FIGS.
When the assist stop signal is detected (S), the speed decreases as indicated by the solid line (1), but starts decreasing as indicated by the broken line (2), and gradually decreases so as to converge to zero while gradually decreasing the speed change. Is also good. Here, the speed change is an absolute value of a change amount of the motor control signal with respect to the time axis.

More specifically, as is well shown by the broken line (2) in FIG. 5, when the assist stop signal is detected, that is, immediately after the start of the fade-out control operation, the decreasing speed is increased to fall below the predetermined level. At times, the rate of decrease was reduced.

FIG. 6 is a partial flow chart which forms a part of the flow chart of FIG. 4 showing the second embodiment according to the present invention. In this flow chart, when it is determined that the fade-out control is performed in S28, S100
Then, n is counted down, and a predetermined number n = 0 (n
× 10 msec = Δt [msec]) until S1
02 was looped.

According to this partial flow chart, after the motor control signal MAX is continued until a predetermined time Δt has elapsed from the detection of the assist stop signal (S) in FIG.
As shown by the dashed line (3) in FIG. 5 , the motor control signal can be reduced. Note that the remaining configuration is not different from the first embodiment.

It should be noted that the motor control signal may be decreased by a curve as indicated by a broken line (2) from the position (S ') after a lapse of a fixed time from the detection of the assist stop signal as described above with reference to FIG. .

In the above-described embodiment, in the electric power steering apparatus for a vehicle, the electric motor 56 for generating a steering assist force in response to the steering of the steering wheel 14 and the signal for controlling the electric motor are transmitted. An electric motor control signal output means for outputting (S26 in the flowchart of FIG. 4), a steering state detecting means for detecting a steering state of the steering wheel 14 (a steering angle sensor 36, a torque sensor 38), and the steering state detecting means An electric motor control means (microcomputer 44) for controlling the electric motor using a signal output by the electric motor control signal output means based on the detection result, and an operation stop signal of the electric motor control means. Electric motor control operation stop signal detecting means (FIG. 3 flowchart) 20) and provided with, by the electric motor control operation stopping signal detecting means before kidou operation stop signal (Fig. 3
When S12 in the flow chart is detected, the electric motor control signal is immediately reduced to a predetermined level (x in FIG. 5) (S42 in the flow chart in FIG. 4), and then gradually decreased (flow in FIG. 4). The chart was configured as in S46).

Further, before when kidou operation stop signal is detected, it is lowered to a certain time the after elapse (Delta] t in FIG. 5) the electric motor control signal a predetermined level (x in FIG. 5), then gradually decreases (Dashed line (3) in FIG. 5).

The predetermined level (x in FIG. 5) is
The force that the steering wheel 14 receives from the road surface is
The value is close to a value (FIGS. 7 (b) and 7 (c)) that reverses from an area lower than the steering assist force to an area higher than the steering assist force.

An electric power steering device for a vehicle, wherein the electric power steering device controls an electric motor 56 for generating a steering assist force in response to the steering of the steering wheel 14 and the electric motor. An electric motor control signal output means (S26 in the flow chart of FIG. 4) for outputting a steering signal; a steering state detection means (steering angle sensor 36, torque sensor 38) for detecting the steering state of the steering wheel 14; An electric motor control means (microcomputer 44) for controlling the electric motor using a signal output by the electric motor control signal output means based on a detection result of the state detection means, and an operation stop signal of the electric motor control means Motor operation stop signal detection means for detecting the Comprising a S20) and the chart, when the front kidou operation stop signal (S12 of the flow chart of FIG. 3) is detected by the electric motor control operation stopping signal detecting means and is immediately lowered to the electric motor control signal, When the decreasing speed is changed so as to decrease over time, the decreasing speed is increased up to a predetermined level.
When the value falls below the predetermined level, the value is reduced (FIG. 5).
(Broken line (2)). More specifically, when the electric motor control operation stop signal is detected, the electric motor control signal is immediately reduced, and the absolute value of the decreasing speed is reduced with time to reduce the motor control signal to zero. It was configured to decrease so as to converge.

[0048] Further, when the front kidou operation stop signal is detected, a certain time with reducing the electric motor control signal after the lapse (Delta] t in FIG. 5), to change its rate of decrease as over time small It was configured as follows.

[0049]

Further, the steering state detecting means is provided via at least one of a torque detecting means (torque sensor 38), a twist detecting means, a steering angle detecting means (steering angle sensor 36), and a steering angular velocity detecting means. The steering state is detected (S14, S16 in FIG. 3).

Although the torque sensor and the steering angle sensor are exemplified as the steering state detecting means, a twist sensor (twist detecting means) or a steering angular velocity sensor (steering angular velocity detecting means)
In that sense, in claim 6 , the steering state detecting means may be configured to perform the steering via at least one of torque detecting means, torsion detecting means, steering angle detecting means, and steering angular velocity detecting means. Detecting the steering state of the vehicle. "

In the above description, the case where the present invention is applied to a general-purpose vehicle has been described. However, the present invention is not limited to this case.

[0053]

According to the first aspect of the present invention, the driver can feel as if the fade-out control is being performed immediately after detecting the steering assist stop signal, so that the driver's discomfort is reduced. In addition, power consumption can be reduced.

According to the second and third aspects, the uncomfortable feeling of the driver is further reduced.

According to the present invention, the driver's discomfort is reduced and the steering feeling can be improved.

In the present invention, the number of sensors suitable for the vehicle can be appropriately selected.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an entire vehicle equipped with an electric power steering control device according to the present invention.

FIG. 2 is an explanatory diagram showing an arrangement of an electric power steering control device applied to the device in FIG. 1;

FIG. 3 is a first half of a main flow chart showing the operation of the apparatus in FIG. 1;

FIG. 4 is a latter half of a main flow chart showing the operation of the apparatus in FIG. 1;

FIG. 5 is a time chart showing changes over time of a motor control signal output to the electric motor by the operation of the apparatus in FIG. 1;

FIG. 6 illustrates a second embodiment of the present invention.
It is a partial flow chart which forms a part of a flow chart.

FIG. 7 is an explanatory diagram illustrating threshold values of a region where the driver feels a reaction force and a region where the driver does not feel the reaction force when an assist torque is generated, using a conventional fade-out control method as an example.

[Explanation of symbols]

 10 General-purpose vehicle 14 Steering wheel 36 Steering angle sensor 38 Torque sensor 44 Microcomputer 50 Controller 56 Electric motor

Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B62D 6/00

Claims (6)

(57) [Claims] 1. An electric power steering apparatus for a vehicle, comprising: an electric motor for generating a steering assist force in response to steering of a steering wheel; and an electric motor control signal output means for outputting a signal for controlling the electric motor. An electric motor for controlling the electric motor by using a signal output by the electric motor control signal output means based on a detection result of the steering state detecting means for detecting a steering state of the steering wheel; and motor control means, and an electric motor control operation stopping signal detecting means for detecting an operation stop signal of the electric motor control means, when the front kidou operation stop signal is detected by the electric motor control operation stopping signal detecting means Immediately reduce the electric motor control signal to a predetermined level, and then gradually decrease An electric power steering control device characterized in that: When wherein before kidou operation stop signal is detected, lowers the electric motor control signal after a predetermined time has elapsed to a predetermined level, the then gradually according to claim 1, wherein, characterized in that to reduce Electric power steering control device. Wherein the predetermined level, the force of the steering wheel receives from the road surface, the claim 1, wherein or 2, characterized in that in the vicinity of the value that inverts the region over the region below the steering assist force 3. The electric power steering control device according to claim 1. 4. An electric power steering device for a vehicle, the electric power steering device comprising: an electric motor for generating a steering assist force in response to steering of a steering wheel; and a signal for controlling the electric motor. An electric motor control signal output unit that outputs a signal output from the electric motor control signal output unit based on a detection result of the steering state detection unit. and electric motor control means for controlling said electric motor with said and an electric motor control operation stopping signal detecting means for detecting an operation stop signal of the electric motor control means, before SL by the electric motor control operation stopping signal detecting means when operating stop signal is detected, when the immediately lower the electric motor control signal In both cases, when the decreasing speed is changed so as to decrease over time, the decreasing speed is set to a predetermined rate.
It is large up to the bell and below the predetermined level
Electric power steering control apparatus characterized by can was set to be smaller. When 5. Before kidou operation stop signal is detected, the lowering the electric motor control signal after a certain time, and changing the reduction rate to over time small claims Item 5. The electric power steering control device according to item 4. 6. The steering state detecting means detects a steering state of the steering via at least one of a torque detecting means, a torsion detecting means, a steering angle detecting means, and a steering angular velocity detecting means. claims 1, wherein the
6. The electric power steering control device according to any one of claims 5 to 5 .