JP2004352001A - Automatic steering device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a steering wheel from rapidly rotating at the moment of a changing of a control state of an actuator for turning the wheel. <P>SOLUTION: When, in automatic steering mode where the driving of the actuator is controlled based on a preset norm steering torque, a state where an external force FDO applied when a tire runs on a small stone or a step is canceled by a driving force FA0 generated by the actuator and the turning angle θ is kept 0 is switched to an electric power steering mode where the driving of the actuator is controlled based on a steering torque applied to the steering wheel by a driver, the driving force FA0 disappears, hence the wheel is turned by the external force FDO, and the steering wheel rapidly rotates. By slowly switching the automatic steering mode to the electric power steering mode in a switching time t0, the rapid rotation of the steering wheel is prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an automatic vehicle steering apparatus for assisting a driver to perform a parking operation using an actuator that steers a wheel of a vehicle.
[0002]
[Prior art]
Such an automatic steering device for a vehicle is known from the following patent documents. This automatic steering device is an electric power steering mode that assists the driver's steering operation with the steering torque generated by the actuator, and an automatic steering mode that automatically turns the wheels with the steering torque generated by the actuator to assist the parking operation. When the vehicle reaches the target position, the automatic steering mode is stopped and the mode shifts to the electric power steering mode.
[0003]
[Patent Document]
JP-A-4-55168
[Problems to be solved by the invention]
By the way, in the above-mentioned conventional type, when an external force is applied to the tire, such as when the tire is twisted due to stationary steering during the automatic steering mode or when the tire runs on a pebble or a step, the driving generated by the actuator is performed. The steering angle of the wheel is held at the control target value by the force. However, when the vehicle reaches the target position and is switched from the automatic steering mode to the electric power steering mode, the driving force is not generated by the actuator, so that the wheels are steered by the external force and the steering handle rotates rapidly. At this time, there was a problem that the driver felt uncomfortable when the driver put his hand on the steering wheel.
[0005]
The present invention has been made in view of the above circumstances, and has as its object to prevent the steering wheel from suddenly turning at the moment when the control state of the actuator for turning the wheels is switched.
[0006]
[Means for Solving the Problems]
To achieve the above object, according to the invention described in claim 1, an actuator for turning a wheel of a vehicle and an actuator control means for switching the actuator between a first control state and a second control state are provided. In the first control state, the driving of the actuator is controlled based on a steering torque applied to a steering wheel by a driver. In the second control state, the actuator is controlled based on a control target value stored or calculated in advance. In the automatic steering apparatus for a vehicle in which the driving of the vehicle is controlled, the actuator control means sets the transition time from the second control state to the first control state based on the driving force of the actuator before and after the transition in both control states. An automatic steering device for a vehicle is proposed.
[0007]
According to the above configuration, the driving of the actuator is controlled based on the steering torque applied to the steering wheel by the driver from the second control state in which the driving of the actuator is controlled based on the control target value stored or calculated in advance. The transition time to the first control state is set based on the driving force of the actuator before and after the transition in the two control states. Therefore, the driver is prevented from suddenly turning the steering handle due to the change in the driving force of the actuator. Discomfort can be eliminated.
[0008]
According to the second aspect of the invention, in addition to the configuration of the first aspect, the actuator control means sets a transition time from the second control state to the first control state before and after the transition in both control states. There is proposed an automatic steering apparatus for a vehicle, wherein the automatic steering apparatus is set based on a difference between driving forces of the actuators.
[0009]
According to the above configuration, the transition time from the second control state to the first control state is set based on the difference in the driving force of the actuator before and after the transition, so that the difference in the driving force, that is, the driving of the actuator The transition time can be set according to the magnitude of the generated steering angle, and rapid rotation of the steering wheel can be effectively prevented.
[0010]
According to a third aspect of the present invention, in addition to the configuration of the first or second aspect, the actuator is an electric motor, and the actuator control means detects a driving force of the actuator based on a current supplied to the actuator. An automatic steering device for a vehicle is proposed.
[0011]
According to the above configuration, the driving force of the actuator composed of the electric motor is detected based on the current supplied thereto, so that a special driving force detecting means is not required, which can contribute to cost reduction.
[0012]
Note that the electronic control unit U of the embodiment corresponds to the actuator control means of the present invention, the front wheel Wf of the embodiment corresponds to the wheel of the present invention, and the reference turning angle θref of the embodiment corresponds to the control target value of the present invention. Correspondingly, the electric power steering mode of the embodiment corresponds to the first control state of the present invention, and the automatic steering mode of the embodiment corresponds to the second control state of the present invention.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples of the present invention shown in the accompanying drawings.
[0014]
1 to 12 show an embodiment of the present invention. FIG. 1 is an overall configuration diagram of a vehicle provided with an automatic steering device, FIG. 2 is an explanatory diagram of an operation in a back parking / left mode, and FIG. FIGS. 4 and 5 are views showing a switch and an automatic parking start switch. FIGS. 4 and 5 are diagrams for explaining the operation of the first and second examples at the time of mode transition. FIG. 6 shows the relationship between the current difference of the actuator and the mode switching time. 7 to 10 are operation explanatory diagrams of the third to sixth examples at the time of mode transition, FIG. 11 is a graph showing the relationship between the current difference of the actuator and the mode switching time, and FIG. 12 is variable. 7 is a graph showing the mode switching time of FIG.
[0015]
As shown in FIG. 1, the vehicle V includes a pair of front wheels Wf, Wf and a pair of rear wheels Wr, Wr. The steering handle 1 and the front wheels Wf, Wf as the steered wheels, a steering shaft 2 rotating integrally with the steering handle 1, a pinion 3 provided at the lower end of the steering shaft 2, a rack 4 meshing with the pinion 3, and a rack 4 Are connected by left and right tie rods 5 and 5 provided at both ends of the knuckle and left and right knuckles 6 and 6 connected to the tie rods 5 and 5, respectively. An actuator 7 composed of an electric motor is connected to the steering shaft 2 via a worm gear mechanism 8 in order to assist the driver in operating the steering handle 1 or to perform automatic steering for garage described later.
[0016]
The steering control device 21 includes a control unit 22 and a storage unit 23. The control unit 22 includes a steering angle detection unit Sa that detects a steering angle θ that is a rotation angle of the steering handle 1, and a steering handle. A steering torque detecting means Sb for detecting the steering torque T, wheel rotational angle detecting means Sc for detecting the rotational angles of the wheels Wf, Wf; Wr, Wr, and a brake operation amount for detecting the operation amount of the brake pedal 9. Signals from the detecting means Sd and the shift range detecting means Se for detecting the shift range (“D” range, “R” range, “N” range, “P” range, etc.) selected by the select lever 10 are input. Is done.
[0017]
3, the mode selection switch Sf and the automatic parking start switch Sg operated by the driver are connected to the control unit 22. The mode selection switch Sf is operated when selecting one of four types of parking modes to be described later, that is, back parking / right mode, back parking / left mode, parallel parking / right mode, and parallel parking / left mode. Buttons. The automatic parking start switch Sg is operated when starting automatic parking in any mode selected by the mode selection switch Sf.
[0018]
The storage unit 23 stores data of the four types of parking modes, that is, a relationship between the reference turning angle θref and the moving distance X of the vehicle V as a table in advance. The moving distance X of the vehicle V is determined by multiplying the known circumference of the wheels Wf, Wf; Wr, Wr by the rotation angles of the wheels Wf, Wf; Wr, Wr detected by the wheel rotation angle detecting means Sc. Can be The moving distance X is calculated using a high select value, a low select value, or an average value of the outputs of the wheel rotation angle detecting means Sc.
[0019]
The control unit 22 controls the operation of the actuator 7 based on the signals from the detection units Sa to Se and the switches Sf and Sg, and the parking mode data stored in the storage unit 23. The operation of the operation stage teaching device 11 including a lamp, a chime, a buzzer, and the like is controlled.
[0020]
Next, the operation of the embodiment of the present invention having the above-described configuration will be described.
[0021]
At the normal time when the automatic parking is not performed (when the mode selection switch Sf is not operated), the electric power steering mode is set in which the steering control device 21 functions as a general power steering control device. Specifically, when the driver operates the steering handle 1 to turn the vehicle V, the steering torque detecting means Sb detects the steering torque T input to the steering handle 1, and the control unit 22 determines the steering torque T based on the steering torque T. To control the driving of the actuator 7. As a result, the left and right front wheels Wf, Wf are steered by the driving force of the actuator 7, and the steering operation of the driver is assisted.
[0022]
Next, the contents of the automatic steering control will be described by taking a back parking / left mode (a mode in which the vehicle is parked while backing at a parking position on the left side of the vehicle V) as an example.
[0023]
First, as shown in FIG. 2 (A), the driver moves the vehicle V to the vicinity of the garage to be parked by the driver's own steering operation. The vehicle V is stopped at a position (start position {circle around (1)}) where the mark M (see FIG. 1) provided on the vehicle coincides with the center line of the garage. Then, when the mode selection switch Sf is operated to select the back parking / left mode and the automatic parking start switch Sg is turned on, the mode is switched from the electric power steering mode to the automatic steering mode, and the automatic steering control is started. While the automatic steering control is being performed, the operation stage teaching device 11 displays the current position of the own vehicle, the surrounding obstacles, the parking position, and the target movement trajectory of the own vehicle from the start position (1) to the target position (3). A return position (2) for switching from forward to reverse is displayed, and various instructions and warnings such as operation of the select lever 10 at the return position (2) are given to the driver by voice from a speaker.
[0024]
Note that a door mirror may be used instead of the mark M provided inside the door, and the mark M or the door mirror may be aligned with the end of the garage instead of being aligned with the center line of the garage.
[0025]
By the automatic steering control, even if the driver only releases the brake pedal 9 to cause the vehicle V to creep and does not operate the steering handle 1, the front wheels are controlled based on the data of the back parking / left mode selected by the mode selection switch Sf. Wf and Wf are automatically steered. That is, while the vehicle V moves forward from the start position (1) to the turning position (2), the front wheels Wf and Wf are automatically steered to the right, and while the vehicle V moves backward from the turning position (2) to the target position (3). The front wheels Wf, Wf are automatically steered to the left.
[0026]
As is clear from FIG. 2B, while the automatic steering control is being performed, the control unit 22 reads the reference steering angle θref of the back parking / left mode read from the storage unit 23 and the steering angle detection means Sa. A deviation E (= θref−θ) is calculated on the basis of the steering angle θ input from the controller, and the operation of the actuator 7 is controlled so that the deviation E becomes zero. At this time, since the data of the reference turning angle θref is set in accordance with the moving distance X of the vehicle V, the vehicle V always moves on the moving trajectory even if there is a slight change in the vehicle speed of the creep running. Will be.
[0027]
The automatic steering control is stopped when the driver turns off the mode selection switch Sf. In addition, when the driver returns the select lever 10 to the “P” range, the driver releases the foot from the brake pedal 9. In this case, the operation is stopped when the driver operates the steering handle 1, and the control returns to the normal power steering control.
[0028]
By the way, when the vehicle V reaches the target position (3) and the driver turns off the mode selection switch Sf, returns the select lever 10 to the “P” range, or releases the foot from the brake pedal 9, the automatic steering mode is started. The mode is switched to the electric power steering mode. When switching to the electric power steering mode, if the driver does not operate the steering handle 1, the actuator 7 does not generate the steering torque, and the steering handle 1 does not rotate on its own. Then, when the vehicle V reaches the target position {circle around (3)}, the steering angle θ should be zero.
[0029]
However, when the vehicle V reaches the target position {circle around (3)}, as shown in FIG. 4, the tire is riding on a pebble or a curb, or the tire is twisted due to stationary cutting, so that the tire is directed rightward to the front wheels Wf, Wf. Assuming that the external force FD0 has been applied, the current IA0 flows through the actuator 7 by the automatic steering control, and the actuator 7 is driven to the left (steering torque) to maintain the reference turning angle θref = 0 against the external force FD0. FA0 (= -FD0) is generated.
[0030]
In this state, when the automatic steering mode ends and the mode is switched to the electric power steering mode at time a, the current IA0 of the actuator 7 instantaneously becomes 0 as shown by the broken line, and the leftward driving force FA0 instantly becomes 0. However, since the right-hand external force FD0 is still applied to the front wheels Wf, Wf, the steering angle θ increases instantaneously from 0 to θR0 as shown by the broken line by the external force FD0, and the steering handle 1 rotates rapidly. Doing so may make the driver feel uncomfortable.
[0031]
Therefore, in the present embodiment, a switching time t0 is taken between the end of the automatic steering mode and the start of the electric power steering mode, and the current of the actuator 7 is slowly changed from IA0 to 0 during the switching time t0. By changing, the steering wheel 1 is prevented from suddenly turning, and the driver's uncomfortable feeling is eliminated.
[0032]
As shown in FIG. 5, when the external force FD1 applied to the front wheels Wf, Wf from the pebbles and curbs is large, the switching time t0 may be taken between the end of the automatic steering mode and the start of the electric power steering mode. The change rate at which the current of the actuator 7 changes from IA1 to 0 during the switching time t0 is large (see the broken line), and the steering handle 1 rotates at a considerable speed, giving the driver an uncomfortable feeling. Therefore, when the external force FD1 applied to the front wheels Wf, Wf is large, by taking a sufficiently long switching time t1 in response thereto, the current of the actuator 7 is slowly changed from IA1 to 0, and the steering handle 1 is suddenly moved. By preventing rotation, the driver's discomfort can be eliminated.
[0033]
From the above, as shown in FIG. 6, by increasing the switching time t in accordance with the increase in the current difference | DIA | of the actuator 7 before and after switching from the automatic steering mode to the electric power steering mode, the front wheels Wf, The rapid rotation of the steering handle 1 can be prevented regardless of the magnitude of the external force applied to Wf and while minimizing the switching time t. However, an upper limit value tMAX is set for the switching time t so that the time required for switching from the automatic steering mode to the electric power steering mode does not become too long.
[0034]
Next, a case will be described in which the mode is shifted to the electric power steering mode because the driver operates the steering wheel 1 during the automatic steering mode.
[0035]
As shown in FIG. 7, the driver operates the steering wheel 1 in a state in which the tire runs on a pebble or a curb during the automatic steering mode, or the tire is twisted by the stationary steering to apply a rightward external force FD2 to the front wheels Wf, Wf. Is applied with a leftward driving force FH2. At this time, the actuator 7 generates a leftward driving force FA2 by the automatic steering control, and the sum of the driving force FH2 of the driver and the driving force FA2 of the actuator 7 is balanced with the external force FD2. The turning angle θref = 0 is maintained.
[0036]
When the driver switches from the automatic steering mode to the electric power steering mode by applying the leftward driving force FH2 to the steering wheel 1, the actuator 7 generates the leftward driving force FA2 'assisting the leftward driving force FH2 of the driver. However, since the sum FH2 + FA2 'of the two driving forces in the electric power steering mode is smaller than the sum FH2 + FA2 of the two driving forces in the automatic steering mode, the remaining FD2-FH2-FA2' of the external force that is not canceled out. However, the steering handle 1 rotates to the right without permission, and the steering angle θR2 is generated.
[0037]
Therefore, in the present embodiment, a switching time t2 is taken between the end of the automatic steering mode and the start of the electric power steering mode, and the current of the actuator 7 is slowly changed from IA2 to IA2 ′ during the switching time t2. By doing so, the abrupt rotation of the steering handle 1 is prevented and the driver's uncomfortable feeling is eliminated.
[0038]
As shown in FIG. 8, when the leftward driving force FH2 applied to the steering wheel 1 by the driver is larger than that in FIG. 7, the leftward driving generated by the actuator 7 after switching from the automatic steering mode to the electric power steering mode. The force FA2b 'also increases, and the sum of the leftward driving force FH2b by the driver and the leftward driving force FA2b' by the actuator 7 exceeds the external force FD2. Therefore, when the mode is switched to the electric power steering mode, the steering handle 1 is turned leftward. And the steering angle θR2b is generated.
[0039]
Also in this case, a switching time t2b is taken between the end of the automatic steering mode and the start of the electric power steering mode, and the current of the actuator 7 is slowly changed from IA2b to IA2b 'during the switching time t2b. By changing it, the sudden rotation of the steering handle 1 can be prevented, and the driver's discomfort can be eliminated.
[0040]
As shown in FIG. 9, when the leftward driving force FH2c applied to the steering handle 1 by the driver is further increased as compared with the case of FIGS. 7 and 8 and exceeds the rightward external force FD2, the driving force FA2c generated by the actuator 7 becomes Turn right. On the other hand, since the driving force FA2c 'generated by the actuator 7 after switching to the electric power steering mode becomes the same left direction as the driving force FH2c of the driver, the steering handle 1 moves leftward by the driving force of FH2c + FA2c'-FD2. And the steering angle θR2c is generated.
[0041]
Also in this case, a switching time t2c is taken between the end of the automatic steering mode and the start of the electric power steering mode, and the current of the actuator 7 is slowly changed from IA2c to IA2c 'during the switching time t2c. By changing it, the sudden rotation of the steering handle 1 can be prevented, and the driver's discomfort can be eliminated.
[0042]
As shown in FIG. 10, when the direction of the driving force FH3 applied to the steering wheel 1 by the driver in the automatic steering mode is the same right direction as the direction of the external force FD3, the driving force FA3 generated by the actuator 7 becomes leftward. Therefore, after switching to the electric power steering mode, the external force FD3, the driving force FH3 of the driver, and the driving force FA3 'generated by the actuator 7 are all rightward, and the steering handle 1 is turned rightward by the driving force of FD3 + FH3 + FA3'. And the turning angle θR3 is generated.
[0043]
Also in this case, a switching time t3 is taken between the end of the automatic steering mode and the start of the electric power steering mode, and the current of the actuator 7 is slowly changed from IA3 to IA3 'during the switching time t3. By changing it, the sudden rotation of the steering handle 1 can be prevented, and the driver's discomfort can be eliminated.
[0044]
Also in the four cases shown in FIGS. 7 to 10, as shown in FIG. 11, the current differences | DIA2b |, | DIA2 |, | DIA2c | of the actuator 7 before and after switching from the automatic steering mode to the electric power steering mode. , | DIA3 |, the rapid rotation of the steering wheel 1 regardless of the magnitude of the external force applied to the front wheels Wf, Wf, and while keeping the switching time t to a minimum. Can be prevented. However, an upper limit value tMAX is set for the switching time t so that the time required for switching from the automatic steering mode to the electric power steering mode does not become too long.
[0045]
The relationship between the switching time t and the current difference | DIA | of the actuator 7 before and after switching from the automatic steering mode to the electric power steering mode may be changed according to conditions as shown in FIG. That is, when the driver applies a driving force to the steering handle 1 (FIGS. 7 to 10), it is a case where the driver intends to perform spontaneous steering. As shown by the solid line, the switching time t may be set shorter than when the driving force is not applied (in the case of FIGS. 4 and 5). Thus, it is possible to perform steering based on the driver's will immediately after switching to the electric power steering mode.
[0046]
As described above, when the current difference | DIA | of the actuator 7 before and after switching from the automatic steering mode to the electric power steering mode is small, that is, when the steering angle θ generated by the operation of the actuator 7 when switching between the two modes is small. The switching time t for both modes is set short, and conversely, when the steering angle θ generated by the operation of the actuator 7 is large, the switching time t for both modes is set long, so that the switching time t for both modes is minimized. However, it is possible to prevent the steering handle 1 from suddenly turning and giving the driver an uncomfortable feeling.
[0047]
In addition, since the driving force generated by the actuator 7 is obtained by detecting the current supplied to the actuator 7, a special sensor for detecting the driving force generated by the actuator 7 can be eliminated to contribute to cost reduction.
[0048]
The embodiments of the present invention have been described above. However, various design changes can be made in the present invention without departing from the gist thereof.
[0049]
For example, in the embodiment, the movement trajectory of the vehicle V up to the target position (3) is stored in the storage unit 23 in advance, but the movement trajectory can be calculated from the current position of the vehicle V and the target position (3). It is.
[0050]
【The invention's effect】
According to the first aspect of the present invention, the steering applied to the steering wheel by the driver from the second control state in which the driving of the actuator is controlled based on the control target value stored or calculated in advance. The transition time to the first control state in which the driving of the actuator is controlled based on the torque is set based on the driving force of the actuator before and after the transition in both control states. It is possible to prevent the driver from feeling uncomfortable by preventing sudden rotation.
[0051]
According to the invention described in claim 2, the transition time from the second control state to the first control state is set based on the difference between the driving forces of the actuators before and after the transition, so that the difference between the driving forces is determined. The transition time is set in accordance with the magnitude, that is, the magnitude of the turning angle generated by driving the actuator, and it is possible to effectively prevent a sudden rotation of the steering handle.
[0052]
According to the third aspect of the present invention, the driving force of the actuator constituted by the electric motor is detected based on the current supplied thereto, so that a special driving force detecting means is not required, which contributes to cost reduction. Can be.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a vehicle provided with an automatic steering device. FIG. 2 is an explanatory diagram of an operation in a back parking / left mode. FIG. 3 is a diagram showing a mode selection switch and an automatic parking start switch. FIG. FIG. 5 is an operation explanatory diagram of the first example at the time of operation. FIG. 5 is an operation explanatory diagram of the second example at the time of mode transition. FIG. 6 is a graph showing the relationship between the current difference of the actuator and the mode switching time. FIG. 8 is an explanatory diagram of the operation of the third example at the time of the mode transition. FIG. 9 is an operational explanatory diagram of the fourth example at the time of the mode transition. FIG. 9 is an operational explanatory diagram of the fifth example at the time of the mode transition. FIG. 11 is a diagram illustrating the operation of the sixth example at the time of mode transition. FIG. 11 is a graph showing a relationship between the current difference of the actuator and the mode switching time. FIG. 12 is a graph showing a variable mode switching time.
1 steering handle 7 actuator U electronic control unit (actuator control means)
V Vehicle Wf Front wheel (wheel)
θre Standard steering angle (control target value)

Claims (3)

An actuator (7) for steering a wheel (Wf) of the vehicle (V); and an actuator control means (U) for switching the actuator (7) between a first control state and a second control state.
In the first control state, the driving of the actuator (7) is controlled based on the steering torque applied to the steering handle (1) by the driver,
In the second control state, in an automatic steering device for a vehicle in which driving of an actuator (7) is controlled based on a control target value (θref) stored or calculated in advance,
A vehicle, wherein the actuator control means (U) sets a transition time from the second control state to the first control state based on the driving force of the actuator (7) before and after the transition in both control states. Automatic steering system. The actuator control means (U) sets a transition time from the second control state to the first control state based on a difference between driving forces of the actuator (7) before and after the transition in both control states. The vehicle automatic steering device according to claim 1, wherein The actuator according to claim 1 or 2, wherein the actuator (7) is an electric motor, and the actuator control means (U) detects a driving force of the actuator based on a current supplied to the actuator (7). Automatic vehicle steering system.

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